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Sample records for breccia

  1. Hydrovolcanic Breccia Pipe Structures-General Features and Genetic Criteria. I. Phreatomagmatic Breccias

    Directory of Open Access Journals (Sweden)

    Călin G. Tămas

    2002-04-01

    Full Text Available Two types of hydrovolcanic breccias are generally accepted: phreatomagmatic and phreatic. Due to their specific characteristics generated during the brecciation, characteristics that control the ore deposition, these breccias represent favourable hosts for mineralization. The depth of formation, the general form and dimensions, the breccia - host rock contact, as well as fragments, matrix, and open spaces altogether control the position and the size of the breccia hosted ore bodies and contribute in different degrees to the rise of the ore grades in phreatomagmatic and phreatic structures. Consequently, the recognition of the genetic type of breccia allows an appropriate strategy in mineral exploration. Describing a breccia necessarily implies a check of its general features, such as environment/depth of formation, general form/geometry, dimensions, breccia-host rock contact, fragments, matrix, alteration, mineralization, surface connection, as well as of its additional features, namely fluidization and facies changes (see Table 2. There are several characteristics with high genetic significance among the abundant descriptive features regarding breccia structures. To point out such evidences means to find out the keys for the genetic intrepretation. A complete list of genetic criteria is proposed for phreatomagmatic breccias (see Table 3.

  2. A mineralized breccia pipe in Monhawk Canyon, Arizona

    International Nuclear Information System (INIS)

    This book reports on hundreds of solution-collapse breccia pipes in northern Arizona. High-grade U ore, and potentially economic concentrations of Ag, Co, Cu, Ni, Pb, and Zn in some pipes, has stimulated mining activity there. More than 900 confirmed and suspected breccia pipes have been mapped by this study. One pipe was chosen for exploration drilling in 1984 because it exhibited all preestablished exploration criteria. Five rotary and core holes were drilled into this pipe; they contained mineralized breccia

  3. Apollo 15 regolith breccias and soils: Comparative petrology and chemistry

    Science.gov (United States)

    Simon, S. B.; Papike, J. J.; Laul, J. C.

    1985-01-01

    Soils and regolith breccias contain clues to the geologic processes that contributed to the evolution of the local regolith over time. A suite of ten regolith breccias from the Apollo 15 site were compared with the results of previous studies in order to learn more about the regolith evolution at that site.

  4. Cockade breccia: Product of mineralisation along dilational faults

    Science.gov (United States)

    Frenzel, Max; Woodcock, Nigel H.

    2014-11-01

    Cockade breccias are fault fills in which individual clasts are completely surrounded by concentric layers of cement. They occur particularly in low-temperature near-surface hydrothermal veins. At least six mechanisms have been proposed for the formation of cockade breccia-like textures, but only two - repeated rotation-accretion, and partial metasomatic replacement of clast minerals - have been supported by detailed evidence. A typical example of cockade breccia from the Gower Peninsula (South Wales) shows clear evidence for the rotation-accretion mechanism: in particular, overgrown breakage points in cement layers - where cockades were previously touching each other - and rotated geopetal infills of haematitic sediment. Based on the available evidence, it is proposed that cockade textures result from low rates of cement growth compared to high rates of dilational fault slip. Seven criteria are given for the correct identification of cockade breccias.

  5. Synthesis for Lunar Simulants: Glass, Agglutinate, Plagioclase, Breccia

    Science.gov (United States)

    Weinstein, Michael; Wilson, Stephen A.; Rickman, Douglas L.; Stoeser, Douglas

    2012-01-01

    The video describes a process for making glass for lunar regolith simulants that was developed from a patented glass-producing technology. Glass composition can be matched to simulant design and specification. Production of glass, pseudo agglutinates, plagioclase, and breccias is demonstrated. The system is capable of producing hundreds of kilograms of high quality glass and simulants per day.

  6. The Curious Case of the Lunar Magnesian Granulitic Breccias

    Science.gov (United States)

    Korotev, R. L.; Jolliff, B. L.

    2001-01-01

    Magnesian granulitic breccias have high Th/Sm ratios, they are not related to Mg-suite plutonic rocks in any straightforward manner, and they may have an igneous rock precursor that is not yet recognized among our samples of the Moon. Additional information is contained in the original extended abstract.

  7. Sudbury project (University of Muenster-Ontario Geological Survey): New investigations on Sudbury breccia

    Science.gov (United States)

    Mueller-Mohr, V.

    1992-01-01

    Sudbury breccias occur as discordant dike breccias within the footwall rocks of the Sudbury structure, which is regarded as the possible remnant of a multiring basin. Exposures of Sudbury breccias in the North Range are known up to a radial distance of 60-80 km from the Sudbury Igneous Complex (SIC). The breccias appear more frequent within a zone of 10 km adjacent to the SIC and a further zone located about 20-33 km north of the structure. From differences in the structure of the breccias, as for example the size of the breccia dikes, contact relationships between breccia and country rock as well as between different breccia dikes, fragment content, and fabric of the ground mass, as seen in this section, the Sudbury Breccias have been classified into four different types. (1) Early breccias with a clastic/crystalline matrix comprise small dikes ranging in size from approx. 1 cm to max. 20 cm. (2) Polymict breccias with a clastic matrix represent the most common type of Sudbury breccia. The thickness of the dikes varies from several tens of centimeters to a few meters but can also extend to more than 100 m in the case of the largest known breccia dike. Contacts with country rock are sharp or gradational. Heterogenous matrix consisting of a fine-grained rock flour displays nonoriented textures as well as extreme flow lines. Chemical analysis substantiates at least some mixing with allochthonous material. (3) Breccias with a crystalline matrix are a subordinate type of Sudbury breccia. According to petrographical and chemical differences, three subtypes have been separated. (4) Late breccias with a clastic matrix are believed to represent the latest phase of brecciation. Two subtypes have been distinguished due to differences in the fragment content.

  8. Chemical variability of glass clasts in Apollo 16 regolith breccias

    International Nuclear Information System (INIS)

    Optically homogeneous discrete fragments of glass embedded in the matrix of eight regolith breccias from the Apollo 16 mission were selected for electron probe microanalysis. Seven of these breccias have a trapped 40Ar/36Ar ratio between 8.8 and 12.5; hence they are ancient breccias with assembly ages over 4.0 Ga. The other breccia has trapped 40Ar/36Ar ratio of 4.4 and is younger. We report on the 10-element (Na, Mg, Al, Si, K, Ca, Ti, Cr, Mn, Fe) analysis of 916 glass fragments. Glass fragments were classified according to colour, and also into four braod chemical categories. Basically, glasses with > 15 per cent FeO were termed mare-type and filtered, those of the rest with > 4 per cent K2O were termed KREEP-type and those with K2O between 0.1 per cent and 0.4 per cent were termed LKFM-type; the rest were called anorthositic. A few glasses have compositions of HASP; plagioclase, and 'granite'. Four glasses have an mg' > 0.9; three of these have troilite inclusions. Anorthositic compositions dominate the glass population; KREEP and LKFM compositions are more abundant than mare-type compositions in the ancient regolith breccias with the highest 40Ar/36Ar ratios include about 4.5 per cent mare-type glasses and about 7 per cent KREEP glasses; these abundances decrease marginally with decreasing 40Ar/36Ar ratios in the ancient regolith breccias. If these ancient regolith breccias represent ancient lunar regolith, then the inference may be made that there was an early lunar episode of mare basalt and KREEP rock emplacement followed by a more voluminous KREEP and mare basalt volcanism beginning at about 4.0 Ga ago or later. Our data suggest that the early lunar megaregolith and the anorthostic crust below were heterogeneous enough to have contained KREEP, LKFM, and mare basalts as well. (author). 48 refs

  9. Regional-scale Proterozoic IOCG-mineralized breccia systems: examples from the Wernecke Mountains, Yukon, Canada

    Science.gov (United States)

    Hunt, Julie; Baker, Tim; Thorkelson, Derek

    2005-12-01

    A large scale Proterozoic breccia system consisting of numerous individual breccia bodies, collectively known as Wernecke Breccia, occurs in north-central Yukon Territory, Canada. Breccias cut Early Proterozoic Wernecke Supergroup sedimentary rocks and occur throughout the approximately 13 km thick deformed and weakly metamorphosed sequence. Iron oxide-copper-gold ± uranium ± cobalt mineralization is associated with the breccia bodies and occurs as veins and disseminations within breccia and surrounding rocks and locally forms the breccia matrix. Extensive sodic and potassic metasomatic alteration occurs within and around breccia bodies and is overprinted by pervasive calcite and dolomite/ankerite, and locally siderite, alteration, respectively. Multiple phases of brecciation, alteration and mineralization are evident. Breccia bodies are spatially associated with regional-scale faults and breccia emplacement made use of pre-existing crustal weaknesses and permeable zones. New evidence indicates the presence of metaevaporitic rocks in lower WSG that may be intimately related to breccia formation. No evidence of breccia-age magmatism has been found to date.

  10. Geochemical studies of the White Breccia Boulders at North Ray Crater, Descartes region of the lunar highlands

    Science.gov (United States)

    Lindstrom, M. M.; Lindstrom, D. J.; Lum, R. K. L.; Schuhmann, P. J.; Nava, D. F.; Schuhmann, S.; Philpotts, J. A.; Winzer, S. R.

    1977-01-01

    The samples of the White Breccia Boulders obtained during the Apollo 16 mission and investigated in the reported study include an anorthositic breccia (67415), a dark matrix breccia (67435), a light matrix breccia (67455), and a large clast of dark matrix breccia (67475) taken from the 67455 boulder. The chemical analyses of bulk samples of the samples are listed in a table. A graph shows the lithophile trace element abundances. Another graph indicates the variation of Sm with Al2O3 content for samples from the White Breccia Boulders. The North Ray Crater breccias are found to be in general slightly more aluminous than breccias from the other stations at the Apollo 16 site. Analyses of eight Apollo 16 breccias cited in the literature range from 25% to 35% Al2O3. However, the North Ray Crater breccias are more clearly distinct from the other Apollo 16 breccias in their contents of lithophile trace elements.

  11. Roter Kamm impact crater, Namibia: Geochemistry of basement rocks and breccias

    Science.gov (United States)

    Reimold, Wolf Uwe; Koeberl, Christian; Bishop, Janice

    1994-06-01

    The Roter Kamm crater in the southern Namib Desert has previously been identified as an impact structure on the basis of crater morphology and the presence of impact melt breccias which contain shock metamorphosed quartz and lithic clasts. To better define the variety of target rocks and breccias, we studied the petrography and chemical composition of a new suite of twenty-eight basement and breccia samples from the Roter Kamm crater. Based on chemical data for target lithologies and breccias we suggest that the crater was formed in a two-layer target region: an upper layer of Gariep metasediments (schist, marble, ± quartzite and sandstone) overlying the crystalline basement of the Namaqualand Metamorphic Complex. The basement was also heavily intruded by coarse-grained quartz veins and quartz- and quartz-feldspar pegmatites. The clast population in the melt breccias indicates that impact-induced melting involved mainly metasedimentary target rocks, with rarely detected contributions from pegmatite and granite/granodiorite. Three varieties of melt breccias can be defined: (1) "schistose," (2) quartzitic melt breccias, (3) "true" impact melt breccias. These melt breccia types are chemically heterogeneous, and even the impact melt breccias may have been produced in situ and not from a coherent melt body. The shapes of the schistose melt breccias, previously thought to be ejected impact breccias, are most likely caused by erosion, and these breccias are now interpreted to be locally derived. The crater basement as exposed at the rim was structurally severely affected and, at least locally, considerable thermal energy was generated during formation of large volumes of cataclastic, mylonitic, and pseudotachylitic breccias. Analyses of mylonite and pseudotachylites from the crater rim, as well as their respective host rocks, show that these breccias were mainly formed from local material. Analyses of pseudotachylite-like breccias indicate that these possible friction

  12. Relationship between collapse history and ore distribution in Sage Breccia pipe, northwestern Arizona

    International Nuclear Information System (INIS)

    The Sage pipe is similar to other collapse breccia pipes in northern Arizona which have their beginnings in cave systems in the Redwall Limestone. Stoping of successively younger units caused the upward propagation of the pipe and provided the pipe-filling breccia. The Sage pipe extends at least 2,500 ft (762 m) vertically; the horizontal dimensions range from 100 to 300 ft (30.5-91 m), depending on variations in the adjoining host stratigraphy. The composition and distribution of breccia facies suggest a complex collapse history and variability in the mechanics of collapse. Rock failure took place both by block stoping and by decementation of sandstone and siltstone followed by flow of unconsolidated grains. The resulting breccias range from matrix to fragment-dominated, to sand flow breccia resulting from flow of individual grains. Episodic secondary collapse or readjustment within the breccia pile complicated facies distribution. Paragenetic studies indicate multiple periods of mineralization at Sage resulting in enrichment in an extensive suite of elements. Ore-grade uranium mineralization extends vertically for nearly 700 ft (213 m). Lateral distribution of the ore is variable and is directly related to breccia facies distribution. In generally, the more permeable breccias tend to be the most highly mineralized. Fracture, intergranular, and interfragment permeability were important to mineral distribution. Breccia continuity or plumbing was also important to lateral and vertical mineral distribution

  13. Laser-Ablation ICP-MS Analyses of Meteoritic Metal Grains in Lunar Impact-Melt Breccias

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    Korotev, R. L.; Jolliff, B. L.; Campbell, A. J.; Humayun, M.

    2003-01-01

    Lunar impact-melt breccias contain metal grains from the meteorites that formed the breccias. Because the breccias contain clastic material that may derive from older breccias, metal grains from earlier impacts may be present, too. The large subset of moderately mafic (8 - 12% FeO), KREEP-rich ("LKFM") melt breccias is particularly important because: (1) these are the melt breccias most likely to have been produced in basin-forming impacts, (2) it is from these breccias that many of the approx. 3.9 Gyr ages that are so common in lunar samples derive, (3) the breccias contain large proportions of FeNi metal, more than 1% in some types of Apollo 16 breccias, and (4) the metal potentially provides information about the impactors causing the apparent cataclysm at 3.9 Gyr.

  14. Digital outcrop model of stratigraphy and breccias of the southern Franklin Mountains, El Paso, Texas

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    Bellian, Jerome A.; Kerans, Charles; Repetski, John E.

    2012-01-01

    This chapter reviews and synthesizes the lithostratigraphy, biostratigraphy, chronostratigraphy, and breccia types of the southwestern part of the great American carbonate bank in the southern Franklin Mountains (SFM), El Paso, Texas. Primary stratigraphic units of focus are the Lower Ordovician El Paso and Upper Ordovician Montoya Groups. These groups preserve breccias formed by collapse of a paleocave system. Precambrian and Silurian units are discussed in the context of breccia clast composition and relative timing of breccia emplacement. Specific attention is paid to the juxtaposition of the top-Sauk second-order supersequence unconformity between the El Paso and Montoya Groups and its relationship to breccias above and below it. The unconformity represents a 10-m.y. exposure event that separates Upper and Lower Ordovician carbonates. The top-Sauk exposure has been previously documented as a significant karst horizon across much of North America.

  15. The geological features and uranium mineralization of Baquan cryptoexplosion breccia in Xiangshan orefield

    International Nuclear Information System (INIS)

    Located in the north of Xiangshan orefield, Baquan uranium deposit is a typical cryptoexplosion breccia related deposit. The cryptoexplosion breccia pipe was closely related to the granite porphyry rock sticks which penetrated into the Sinian metamorphic strata in Late Yanshanian. It's a comprehensive geological body of igneous rock, breccia bodies and ores which is the product of a continuous geological process affected by multi-stage magmatic activity, and hidden explosion. The intrusion of granite porphyry and dacite porphyry in Late Yanshanian, and the formation of crypto explosion breccia and the faults structure are very important to the uranium deposits. The pulsating and hidden cryptoexplosion resulted in the variety of rocks and mineralization alteration. Uranium ore body mainly occurred in cryptoexplosion and shattered breccia and the mineralization is rich in the centre and upper but poor in the edge and bottom of the pipe. (author)

  16. Coalingite from kimberlite breccia of the Manchary pipe, Central Yakutia

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    Zayakina, N. V.; Oleinikov, O. B.; Vasileva, T. I.; Oparin, N. A.

    2015-12-01

    Coalingite, Mg10Fe2(CO3)(OH)24 · 2H2O, rare Mg-Fe hydrous carbonate, has been found in the course of the mineralogical study of a disintegrated kimberlite breccia from the Manchary pipe of the Khompu-May field located in the Tamma Basin, Central Yakutia, 100 km south of Yakutsk. Coalingite occurs as small reddish brown platelets, up to 0.2 mm in size. It is associated with lizardite, chrysotile and brucite, which are typical kimberlitic assemblage. Coalingite is a supergene mineral, but in this case, it is produced by the interaction of brucite-bearing kimberlite and underground water circulating through a vertical or oblique fault zone.

  17. A mineralized breccia pipe in Mohawk Canyon, Arizona; lithologic and geophysical logs

    International Nuclear Information System (INIS)

    Hundreds of solution-collapse breccia pipes crop out in northern Arizona. High-grade U ore, and potentially economic concentrations of Ag, Co, Cu, Ni, Pb, and Zn in some pipes, has stimulated mining activity there. More than 900 confirmed and suspected breccia pipes have been mapped by this study. One pipe was chosen for exploration drilling 1984 because it exhibited all preestablished exploration criteria. Five rotary and core holes were drilled into this pipe; they contained mineralized breccia and zones of U-, Cu-, and Ni-mineralized rock

  18. Uranium-bearing breccia pipes of northwestern Arizona - an overview

    International Nuclear Information System (INIS)

    During the 1950s and 1960s, the uranium deposits in breccia pipes of the Grand Canyon region were regarded as geologic curiosities. Today this area is the site of numerous exploration projects for ore-bearing pipes. The classic example of the older mines is the Orphan Lode, a patented claim within Grand Canyon National Park. Between 1956 and 1969, this deposit produced 4.26 million lb U3O8. Exploration since the mid-1970s has developed numerous new deposits in the Grand Canyon region. The Hack 1, 2, and 3, Pigeon, Kanab North, Canyon, and Pinenut deposits are, or will be, mined. The pipes are circular and originated by dissolution of the Mississippian Redwall Limestone and collapse of the overlying strata. Uraninite ore occurs in both the pipe fill and in association with the peripheral shear zone. The principal host rocks are the Coconino Sandstone, Hermit Shale, and Esplanade Sandstone. Although small (3 to 5 million lb U3O8), the high grade (60 to 70% U3O8) of the deposits makes the pipes attractive exploration targets

  19. Thermal Metamorphic Signature in Melt-Bearing Polymict Breccias from the Steen River Impact Structure, Canada

    Science.gov (United States)

    Walton, E. L.; Dence, M. R.; Herd, C. D. K.

    2015-07-01

    Melt-bearing polymict breccias within drillcore from the Steen River impact structure are described which contain a matrix of clinopyroxene + feldspar + titanite + garnet + oxides formed by recyrstallization of a superheated clastic dust.

  20. Electrical impedance spectroscopy measurements to estimate the uniaxial compressive strength of a fault breccia

    Indian Academy of Sciences (India)

    Sair Kahraman; Michael Alber

    2014-10-01

    Fault breccias are usually not suitable for preparing smooth specimens or else the preparation of such specimens is tedious, time consuming and expensive. To develop a predictive model for the uniaxial compressive strength (UCS) of a fault breccia from electrical resistivity values obtained from the electrical impedance spectroscopy measurements, twenty-four samples of a fault breccia were tested in the laboratory. The UCS values were correlated with corresponding resistivity values and a strong correlation between them could not be found. However, a strong correlation was found for the samples having volumetric block proportion (VBP) of 25–75%. In addition, it was seen that VBP strongly correlated with resistivity. It was concluded that the UCS of the tested breccia can be estimated from resistivity for the samples having VBP of 25–75%.

  1. Northwest Africa 8709: A Rare but Revealing Type 3 Ordinary Chondrite Melt Breccia

    Science.gov (United States)

    Ruzicka, A. M.; Hutson, M.; Friedrich, J. M.; Bland, P. A.; Pugh, R.

    2015-07-01

    We discuss the discovery of a rare L3 melt breccia, which has implications for compaction processes that must have contributed to the lithification of what are expected to have been initially porous primordial chondritic agglomerates.

  2. Rappresentazioni e (in)traducibilità del delirio: Informe sobre ciegos di Alberto Breccia

    OpenAIRE

    Susanna Nanni

    2015-01-01

    The essay proposes an analysis of the relationship between text and images in Informe sobre ciegos (1991) by Alberto Breccia. In his obstinate renunciation to unnecessary words, or surplus signs, and by employing graphic devices that convey a "telluric and formless" world, Breccia interprets and illustrates – without making it comprehensible – the self-destructive delirious state of Fernando Vidal, one of the most controversial and fascinating characters in Argentinian literature. In particul...

  3. Breccia 66055 and related clastic materials from the Descartes region, Apollo 16

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    Fruchter, J. S.; Kridelbaugh, S. J.; Robyn, M. A.; Goles, G. G.

    1974-01-01

    Trace and major element contents obtained by instrumental neutron activation are reported for a number of Apollo 16 soil samples and miscellaneous breccia fragments. In addition, data obtained by instrumental neutron activation and electron microprobe techniques along with petrographic descriptions are presented for selected subsamples of breccia 66055. The compositions of our soil samples can be modeled by mixtures of various amounts of anorthosite, anorthositic gabbro and low-K Fra Mauro basalt components. These mixtures are typical of those found in a number of petrographic surveys of the fines. Breccia 66055 is a complex regolith breccia which consists of at least four distinct types of microbreccias. No systematic relation with respect to stratigraphic age among the various microbreccia types was observed. Compositionally and texturally, the clasts which compose breccia 66055 are similar to a number of previously reported rock types from the Apollo 16 area. The entire breccia appears to have undergone a complex history of thermal metamorphism. We conclude from the study of these samples that the Cayley Formation is probably homogeneous in its gross compositional and petrographic aspects.

  4. Historical, Geological, and Mining Benchmarks Concerning the Endogeneous Breccia Structures Associated with the Neogene Magmatic Events in Romania (in Romanian

    Directory of Open Access Journals (Sweden)

    Călin G. Tămas

    2001-04-01

    Full Text Available An up-to date exhaustive bibliographic study is presented in order to highlight the evolution of the knowledge of endogenous breccias related to Neogene magmatism from Romania during the 19th and 20th centuries. This approach is based mainly on Romanian literature but there are also several foreign citations. Instead of the general opinion (widespread among Romanian mining companies according to which the occurrence of the breccia structures in Romania is scarcely, this paper show the ubiquitous presence of breccia pipe and breccia dyke structures among the Neogene ore deposits from Romania, in Apuseni Mountains as well as in Eastern Carpathians.

  5. Planar deformation features in quartz from impact-produced polymict breccia of the Xiuyan crater, China

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    Chen, Ming; Koeberl, Christian; Xiao, Wansheng; Xie, Xiande; Tan, Dayong

    2011-05-01

    The 1.8 km-diameter Xiuyan crater is an impact structure in northeastern China, exposed in a Proterozoic metamorphic rock complex. The major rocks of the crater are composed of granulite, hornblendite, gneiss, tremolite marble, and marble. The bottom at the center of the crater covers about 100 m thick lacustrine sediments underlain by 188 m thick crater-fill breccia. A layer of polymict breccia composed of clasts of granulite, gneiss, hornblendite, and fragments of glass as well as clastic matrix, occurs near the base, in the depth interval from 260 to 295 m. An investigation in quartz from the polymict breccia in the crater-fill units reveals abundant planar deformation features (PDFs). Quartz with multiple sets of PDFs is found in clasts of granulite that consist of mainly quartz and feldspar, and in fine-grained matrix of the impact-produced polymict breccia. A universal stage was used to measure the orientation of PDFs in 70 grains of quartz from five thin sections made from the clasts of granulite of polymict breccia recovered at the depth of 290 m. Forty-four percent of the quartz grains contain three sets of PDFs, and another 40% contain two sets of PDFs. The most abundant PDFs are rhombohedron forms of ?, ?, and ? with frequency of 33.5, 22.3, and 9.6%, respectively. A predominant PDF form of ? in quartz suggests a shock pressure >20 GPa. The occurrence of PDFs in quartz from the polymict breccia provides crucial evidence for shock metamorphism of target rocks and confirms the impact origin of this crater, which thus appears to be the first confirmed impact crater in China.

  6. On identifying parent plutonic rocks from lunar breccia and soil fragments

    Science.gov (United States)

    Haskin, Larry A.; Lindstrom, David J.

    1988-01-01

    Breccia fragments expected from a well-studied boulder of Stillwater anorthosite have been modeled to test the ability to identify parental rock types from examination of breccia and soil fragments. Depending on their size, the boulder fragments give distributions that suggest mixtures of rock types, including monominerallic anorthosite with subordinant amounts of more gabbroic anorthosite, anorthosite, and gabbro for small fragments. The distribution of FeO in samples of lunar ferroan anorthosite (FAN) indicates that FAN has a heterogeneous distribution of mafic minerals like the boulder.

  7. Rappresentazioni e (intraducibilità del delirio: Informe sobre ciegos di Alberto Breccia

    Directory of Open Access Journals (Sweden)

    Susanna Nanni

    2015-07-01

    Full Text Available The essay proposes an analysis of the relationship between text and images in Informe sobre ciegos (1991 by Alberto Breccia. In his obstinate renunciation to unnecessary words, or surplus signs, and by employing graphic devices that convey a "telluric and formless" world, Breccia interprets and illustrates – without making it comprehensible – the self-destructive delirious state of Fernando Vidal, one of the most controversial and fascinating characters in Argentinian literature. In particular, the essay focuses on the conspiracy – at the level of both form and content – and on the graphic (untranslatability of his delirium.

  8. Petrochemistry and origin of basalt breccia from Ban Sap Sawat area, Wichian Buri, Phetchabun, central Thailand

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    Phisit Limtrakun

    2013-08-01

    Full Text Available Thailand is usually considered to be controlled by escape tectonics associated with India-Asia collision during theLate Cenozoic, and basaltic volcanism took place in this extensional period. This volcanism generated both subaqueous andsubaerial lava flows with tholeiitic to alkalic basaltic magma. The subaqueous eruptions represented by the studied WichianBuri basalts, Ban Sap Sawat in particular, are constituted by two main types of volcanic lithofacies, including lava flows andbasalt breccias. The lava flows are commonly porphyritic with olivine and plagioclase phenocrysts and microphenocrysts,and are uncommonly seriate textured. The basalt breccias are strongly vitrophyric texture with olivine and plagioclasephenocrysts and microphenocrysts. Chemical analyses indicate that both lava flows and basalt breccias have similar geochemical compositions, signifying that they were solidified from the same magma. Their chondrite normalized REE patternsand N-MORB normalized patterns are closely analogous to the Early to Middle Miocene tholeiites from central Sinkhote-Alinand Sakhalin, northeastern margin of the Eurasian continent which were erupted in a continental rift environment. The originfor the Wichian Buri basalts show similarity of lava flows and basalt breccias, in terms of petrography and chemical compositions, signifying that they have been formed from the same continental within-plate, transitional tholeiitic magma.

  9. Geochemical constraint on the genesis of uranium deposits hosted by paleokarst breccia in South China

    International Nuclear Information System (INIS)

    An unusual type of uranium deposits hosted by paleokarst breccia was found in South China. By combining the element, isotope and organic geochemistry with the geological data, U-Pb datings and temperature determinations for the representative Sanqilinyi, Sanbaqi and Saqisan deposit, multistage formation processes for this type of uranium deposits are deduced. (author)

  10. Paleomagnetic dating of fracturing using breccia veins in Durness group carbonates, NW Scotland

    Science.gov (United States)

    Douglas Elmore, R.; Burr, Rika; Engel, Michael; Parnell, John

    2010-12-01

    A paleomagnetic study of red fault-related breccia veins in the Cambro-Ordovician Durness Group in NW Scotland was conducted to determine the time of brecciation, the origin of the veins, and the nature and timing of associated fluid-related diagenetic alteration. The veins contain brecciated fragments of the host Durness Group and strike either east-west or north-south. Clasts of breccia cemented by calcite suggest multiple brecciation events. The host Durness Limestone is a gray dolomite and contains a Devonian chemical remanent magnetization (CRM) that resides in magnetite. The veins contain magnetizations that reside in hematite and are interpreted as CRMs. The breccias in north-south veins contain a Triassic CRM whereas the veins with east-west strikes contain a Jurassic CRM. Authigenic hematite is common in the breccias along growth planes in the calcite cements. The two CRMs within the veins are interpreted as dating two separate brecciation and fluid flow events that precipitated authigenic hematite. The brecciation and fluid flow events are interpreted to be related to extension in the Mesozoic which is consistent with the extensional history of the northern Atlantic margins.

  11. Fission track astrology of three Apollo 14 gas-rich breccias

    Science.gov (United States)

    Graf, H.; Shirck, J.; Sun, S.; Walker, R.

    1973-01-01

    The three Apollo 14 breccias 14301, 14313, and 14318 all show fission xenon due to the decay of Pu-244. To investigate possible in situ production of the fission gas, an analysis was made of the U-distribution in these three breccias. The major amount of the U lies in glass clasts and in matrix material and no more than 25% occurs in distinct high-U minerals. The U-distribution of each breccia is discussed in detail. Whitlockite grains in breccias 14301 and 14318 found with the U-mapping were etched and analyzed for fission tracks. The excess track densities are much smaller than indicated by the Xe-excess. Because of a preirradiation history documented by very high track densities in feldspar grains, however, it is impossible to attribute the excess tracks to the decay of Pu-244. A modified track method has been developed for measuring average U-concentrations in samples containing a heterogeneous distribution of U in the form of small high-U minerals. The method is briefly discussed, and results for the rocks 14301, 14313, 14318, 68815, 15595, and the soil 64421 are given.

  12. Analytical Modeling and Contradictions in Limestone Reservoirs: Breccias, Vugs, and Fractures

    Directory of Open Access Journals (Sweden)

    Nelson Barros-Galvis

    2015-01-01

    Full Text Available Modeling of limestone reservoirs is traditionally developed applying tectonic fractures concepts or planar discontinuities and has been simulated dynamically without considering nonplanar discontinuities as sedimentary breccias, vugs, fault breccias, and impact breccias, assuming that all these nonplanar discontinuities are tectonic fractures, causing confusion and contradictions in reservoirs characterization. The differences in geometry and connectivity in each discontinuity affect fluid flow, generating the challenge to develop specific analytical models that describe quantitatively hydrodynamic behavior in breccias, vugs, and fractures, focusing on oil flow in limestone reservoirs. This paper demonstrates the differences between types of discontinuities that affect limestone reservoirs and recommends that all discontinuities should be included in simulation and static-dynamic characterization, because they impact fluid flow. To demonstrate these differences, different analytic models are developed. Findings of this work are based on observations of cores, outcrops, and tomography and are validated with field data. The explanations and mathematical modeling developed here could be used as diagnostic tools to predict fluid velocity and fluid flow in limestone reservoirs, improving the complex reservoirs static-dynamic characterization.

  13. Petrographic and petrological studies of lunar rocks. [Apollo 15 breccias and Russian tektites

    Science.gov (United States)

    Winzer, S. R.

    1978-01-01

    Clasts, rind glass, matrix glass, and matrix minerals from five Apollo 15 glass-coated breccias (15255, 15286, 15465, 15466, and 15505) were studied optically and with the SEM/microprobe. Rind glass compositions differ from sample to sample, but are identical, or nearly so, to the local soil, suggesting their origin by fusion of that soil. Most breccia samples contain green or colorless glass spheres identical to the Apollo 15 green glasses. These glasses, along with other glass shards and fragments, indicate a large soil component is present in the breccias. Clast populations include basalts and gabbros containing phases highly enriched in iron, indicative of extreme differentiation or fractional crystallization. Impact melts, anorthosites, and minor amounts of ANT suite material are also present among the clasts. Tektite glasses, impact melts, and breccias from the Zhamanshin structure, USSR, were also studied. Basic tektite glasses were found to be identical in composition to impact melts from the structure, but no satisfactory parent material has been identified in the limited suite of samples available.

  14. Pseudotachylitic breccia from the Dhala impact structure, north-central India: Texture, mineralogy and geochemical characterization

    Science.gov (United States)

    Pati, J. K.; Reimold, W. U.; Greshake, A.; Schmitt, R. T.; Koeberl, C.; Pati, P.; Prakash, K.

    2015-05-01

    Pseudotachylitic breccia (PTB) occurs in a drill core from the crater floor of the 11 km diameter, Proterozoic Dhala impact structure, India. PTBs were intersected in late Archean granitoids between 348.15 m and 502.55 m depth in the MCB-10 drill core from the center of the Dhala structure. The breccias comprise both cataclastic-matrix as well as melt breccias. The presence of microlites and vesicles in the groundmass and a widely observed flow fabric in the PTB support the presence of melt in the groundmass of some samples. Clasts in PTB are derived from the Archean granitoid basement. PTB matrix, the matrix of impact melt breccia also occurring between 256.50 m and 502.55 m depth, and the target granitoids vary in terms of silica, total alkali, magnesium and iron oxide contents. Chondrite-normalized REE patterns of PTB and target granitoids are similar, but the elemental abundances in the PTB are lower. The restricted size of PTB as veins and pods of up to 2.5 cm width, their occurrence at varied depths over a core length of ~ 150 m, the clast population, and the chemical relationships between PTB and their host rocks all suggest the derivation of these breccias locally from the fractured basement granitoids involving in-situ melting. We favor that this took place due to rapid decompression during the collapse and modification stage of impact cratering, with, locally, additional energy input from frictional heating. Locally, amphibolite and dioritic mylonite occur in the host granitoids and their admixture could have contributed to the comparatively more mafic composition of PTB. Alteration of these crater floor rocks could have involved preferential reduction of silica and alkali element abundances, possibly due to impact-induced hydrothermal activity at crater floor level. This process, too, could have resulted in more mafic compositions.

  15. Age relationships from U-Th-Pb isotope studies of uranium mineralization in Wernecke breccias, Yukon Territory

    International Nuclear Information System (INIS)

    Pb-U ± Th isotope analyses for 17 specimens of uraniferous breccia from the northeastern Wernecke Mountains reveal several apparent ages for mineralization. The oldest date, 1194 Ma, reflects either initial emplacement of the breccias or their modification by effects of the Rackla of Rapitan (Windermere) thick clastic wedges and iron formation. The 510 Ma date reflects mid-Cambrian mineralization roughly coincident with regional uplift (and attendant karstification) and development of thick clastic wedges. This was also an important period for Pb-Zn mineralization. Younger dates resulted from continuing remobilization, and all isotopic ages for mineralized breccia reflect movements associated with the Richardson Fault array

  16. Exploration techniques for locating uranium-mineralized breccia pipes in northern Arizona

    International Nuclear Information System (INIS)

    Thousands of solution-collapse breccia pipes may crop out in the canyons and on the plateaus of northern Arizona, and more than 80 contain uranium or copper mineralized rock; however, their small size and limited rock outcrop make them difficult to locate. Recognition of the pipes on the plateaus is particularly important because mining access to the plateaus is far easier than to the canyons. Several reconnaissance geochemical methods have been tested to help locate suspected and mineralized breccia pipes. (1) A hydrogeochemical survey conducted on the 1500 mi2 (4000 km2) Hualapai Indian Reservation appears to yield anomalous values downstream from regions, such as Mohawk Canyon, where clusters of mineralized pipes occur. Pigeon Spring, east of the Pigeon mine, also had anomalous uranium (44 ppb). (2) A stream-sediment survey was not made on the Hualapai Reservation because the dilution factor that results from the large volume of country rock, compared to that of mineralized rock, swamps out any low-level geochemical signature contributed to streams by rock or soil overlying breccia pipes. Several types of detailed geochemical and geophysical surveys, made over individual collapse features located through examination of aerial photographs and later field mapping, have generally been successful at delineating collapse features from the surrounding host rock: (1) rock geochemistry commonly shows Ag, As, Ba, Cu, Pb, Se, and/or Zn enrichments of from 3 to 100 times background levels over mineralized breccia pipes; (2) soil surveys appear to have the greatest exploration potential of the geochemical methods (e.g., samples collected from the centers of several collapse features show consistently twice the background value for a number of elements);

  17. Petrology and chemistry of Apollo 17 regolith breccias - A history of mixing of highland and mare regolith

    Science.gov (United States)

    Simon, S. B.; Papike, J. J.; Gosselin, D. C.; Laul, J. C.; Hughes, S. S.

    1990-01-01

    Results are presented of petrological and chemical analyses of ten Apollo 17 breccias, showing that two of these consist predominantly of highland material, seven are mare-dominated, and one is a welded volcanic glass deposit; all were formed at or near the Apollo 17 site, and all contain both mare and highland components. The data are indicative of the Apollo 17 breccias formation from immature source regolith. The breccias are considered to be formed locally after an eruption of basalt and orange glass at the site. Since the formation of the breccias, the regolith at the Apollo 17 site has become more mature, and the orange glass abundance has been somewhat decreased by mixing. One of the sample may contain a previously unreported volcanic glass type.

  18. In quest of lunar regolith breccias of exotic provenance - A uniquely anorthositic sample from the Fra Mauro (Apollo 14) highlands

    Science.gov (United States)

    Jerde, Eric A.; Warren, Paul H.; Morris, Richard V.

    1990-01-01

    Bulk compositions of 21 Apollo regolith breccias were determined using an INAA procedure modified from that of Kallemeyn et al. (1989). With one major exception, namely, the 14076,1 sample, the regolith breccias analyzed were found to be not significantly different from the surfaces from which they were collected. In contrast, the 14076,1 sample from the Fra Mauro (Apollo 14) region is a highly anorthositic regolith breccia from a site where anorthosites are extremely scarce. The sample's composition resembles soils from the Descartes (Apollo 16) highlands. However, the low statistical probability for long-distance horizontal transport by impact cratering, together with the relatively high contents of imcompatible elements in 14076,1 suggest that this regolith breccia originated within a few hundred kilometers of the Apollo 14 site. Its compositional resemblance to ferroan anorthosite strengthens the hypothesis that ferroan anorthosite originated as the flotation crust of a global magmasphere.

  19. Petrology and oxygen isotopic compositions of clasts in HED polymict breccia NWA 5232

    Science.gov (United States)

    Drongelen, Katrina D.; Rumble, Douglas; Tait, Kimberly T.

    2016-06-01

    Northwest Africa (NWA) 5232, an 18.5 kg polymict eucrite, comprises eucritic and exogenic CM carbonaceous chondrite clasts within a clastic matrix. Basaltic clasts are the most abundant eucritic clast type and show a range of textures and grain size, from subophitic to granoblastic. Other eucritic clast types present include cumulate (high-En pyroxene), pyroxene-lath, olivine rich with symplectite intergrowths as a break-down product of a quickly cooled Fe-rich metastable pyroxferroite, and breccia (fragments of a previously consolidated breccia) clasts. A variable cooling rate and degree of thermal metamorphism, followed by a complex brecciation history, can be inferred for the clasts based on clast rounding, crystallization (and recrystallization) textures, pyroxene major and minor element compositions, and pyroxene exsolution. The range in δ18O of clasts and matrix of NWA 5232 reflects its origin as a breccia of mixed clasts dominated by eucritic lithologies. The oxygen isotopic compositions of the carbonaceous chondrite clasts identify them as belonging to CM group and indicate that these clasts experienced a low degree of aqueous alteration while part of their parent body. The complex evolutionary history of NWA 5232 implies that large-scale impact excavation and mixing was an active process on the surface of the HED parent body, likely 4 Vesta.

  20. 10Be Content in Suevite Breccia from the Bosumtwi Impact Crater

    Science.gov (United States)

    Losiak, Anna; Wild, Eva Maria; Michlmayr, Leonard; Koeberl, Christian

    2013-04-01

    Introduction: According to the current understanding of meteorite impact processes, surface target material is transported from a crater in the form of ejecta or is vaporized/melted (e.g., [1]). The formation model of tektites from the surface of the target rocks has been established using the 10Be content of tektites (e.g., [2]), and chemical comparison with the possible target surface material (e.g., [3]); it was also reproduced by computer modeling (e.g., [4]). On the other hand, some observations ([5, 6]) suggest that part of the surface material may be incorporated into the crater-fill. The aim of this study is to check if surface-derived material is present in suevitic breccias to better understand formation mechanisms of fallback breccias. Also, 10Be can be used to trace contamination of rocks in the top layer of the suevitic layer by meteoric (lake) water. This abstract is an update (based on more data now available) of the previous report presented during the Metsoc75 conference. Samples: The Bosumtwi crater was chosen as study site because of its relatively large size (10.5 km in diameter), young age of 1.07 Ma [7], good state of preservation, and availability of core samples. Clasts from suevitic breccia selected for this study come from the LB-07A and LB-08A cores that are located within the crater and represent fallback breccia (e.g., [7]). Of 41 analyzed samples (22 single clasts and 21 matrix samples - 11 of those being monomictic breccia), 36 came from core LB-07A (in the zone outside the central uplift) and represent depths of 333.7 - 407.9 m and 5 are from core LB-08A (on the flank of the central uplift) from depths 239.5 - 264.9 m. Methods: For each sample, 0.8 g of finely grounded material from clasts containing in situ produced and meteoric 10Be was dissolved in a mixture of HF and HNO3 by microwave digestion. A 9Be carrier (1 mg or 0.6 mg, 10Be/9Be ratio: 2.82±0.31*10-15 [2? uncertainty]) was added to the sample, and then Be was chemically

  1. Mineralogy of an unusual Cr-rich inclusion in the Los Martinez (L6) chrondritic breccia

    Science.gov (United States)

    Brearley, Adrian J.; Casanova, Ignacio; Miller, M. L.; Keil, Klaus

    1991-01-01

    During the petrological study of the L6 chondritic breccia, Los Martinez, we discovered a large, highly unusual Cr-rich inclusion whose mineralogy appears to be unique in both terrestrial and extraterrestrial occurrences. We carried out electron microprobe, scanning electron microscopy, and transmission electron microscopy investigations of this inclusion in order to determine its composition and mineralogy in detail and to establish its origin and possible relationship to other Cr-rich objects in chondritic meteorites. Details of the chemical composition, origin, and thermal history are given.

  2. Apollo 16 regolith breccias and soils - Recorders of exotic component addition to the Descartes region of the moon

    Science.gov (United States)

    Simon, S. B.; Papike, J. J.; Laul, J. C.; Hughes, S. S.; Schmitt, R. A.

    1988-01-01

    Using the subdivision of Apollo 16 regolith breccias into ancient (about 4 Gyr) and younger samples (McKay et al., 1986), with the present-day soils as a third sample, a petrologic and chemical determination of regolith evolution and exotic component addition at the A-16 site was performed. The modal petrologies and mineral and chemical compositions of the regolith breccias in the region are presented. It is shown that the early regolith was composed of fragments of plutonic rocks, impact melt rocks, and minerals and impact glasses. It is found that KREEP lithologies and impact melts formed early in lunar history. The mare components, mainly orange high-TiO2 glass and green low-TiO2 glass, were added to the site after formation of the ancient breccias and prior to the formation of young breccias. The major change in the regolith since the formation of the young breccias is an increase in maturity represented by the formation of fused soil particles with prolonged exposure to micrometeorite impacts.

  3. Breccia-pipe uranium mining in northern Arizona; estimate of resources and assessment of historical effects

    Science.gov (United States)

    Bills, Donald J.; Brown, Kristin M.; Alpine, Andrea E.; Otton, James K.; Van Gosen, Bradley S.; Hinck, Jo Ellen; Tillman, Fred D

    2011-01-01

    About 1 million acres of Federal land in the Grand Canyon region of Arizona were temporarily withdrawn from new mining claims in July 2009 by the Secretary of the Interior because of concern that increased uranium mining could have negative impacts on the land, water, people, and wildlife. During a 2-year interval, a Federal team led by the Bureau of Land Management is evaluating the effects of withdrawing these lands for extended periods. As part of this team, the U.S. Geological Survey (USGS) conducted a series of short-term studies to examine the historical effects of breccia-pipe uranium mining in the region. The USGS studies provide estimates of uranium resources affected by the possible land withdrawal, examine the effects of previous breccia-pipe mining, summarize water-chemistry data for streams and springs, and investigate potential biological pathways of exposure to uranium and associated contaminants. This fact sheet summarizes results through December 2009 and outlines further research needs.

  4. Petrogenesis of a vitrophyre in the martian meteorite breccia NWA 7034

    Science.gov (United States)

    Udry, Arya; Lunning, Nicole G.; McSween, Harry Y.; Bodnar, Robert J.

    2014-09-01

    Northwest Africa (NWA) 7034 and its paired meteorites NWA 7533 and NWA 7475 are the first recognized martian polymict breccia samples. An unusual, large, subrounded clast in NWA 7034 shows a vitrophyric texture, consisting of skeletal pyroxene and olivine with mesostasis. This lithology has not been observed in the paired meteorites. It crystallized under disequilibrium conditions as indicated by its olivine and pyroxene KDFe/Mg partitioning values, as well as reversed order of crystallization and mineral compositions relative to those predicted by MELTS. We report the highest bulk Ni value (1020 ppm) measured in any known martian meteorite or martian igneous rock, suggesting an impact melt origin for the vitrophyre. Addition of 5.3-7.7% chondritic material to the target rock would account for the Ni enrichment. The bulk major and trace element abundances of the vitrophyre indicate that the protolith was not the host breccia nor any other martian meteorites. However, the clast is compositionally similar to Humphrey rock in Gusev crater analyzed by the Spirit rover and to a texturally distinct group of clasts in the paired meteorite NWA 7533. Thus, we propose that the target rock was an igneous lithology similar to Gusev basalts, which was subsequently contaminated by a chondritic impactor.

  5. Mixed marine and lacustrine input to an oil-cemented sandstone breccia from Brora, Scotland

    Energy Technology Data Exchange (ETDEWEB)

    Peters, K.E. [Mobil Exploration and Producing Technical Center, Dallas, TX (United States); Clutson, M.J. [Mobil North Sea Ltd., Aberdeen (United Kingdom); Robertson, G. [Mobil New Exploration and Producing Ventures, Dallas, TX (United States)

    1999-07-01

    A rounded cobble collected from a beach near Brora, Scotland, contains angular, brecciated sandstone clasts cemented together by crude oil. No oil occurs within the tight, dolomite-cemented clasts, except along fractures. Provenance of the cobble is uncertain, however, the lithology and shape of the clasts suggests that they are fault gouge breccia composed of Old Red Sandstone from the nearby Helmsdale Fault. Oil emplacement, presumably along the fault, cemented the breccia prior to transport and weathering of the cobble. Independent source and biodegradation parameters support mixing of two charges of oil. Like oil from the nearby Beatrice Field, the oil cement contains 24-n-propylcholestanes and {beta}-carotene that indicate marine and lacustrine source rocks, respectively. The oil cement also contains pristane, phytane, residual n-alkanes and a complete series of 25-norhopanes, which indicate mild and heavy biodegradation respectively. The first charge consisted of lacustrine Devonian oil that was heavily biodegraded at shallow depth. The origin of the second charge is unclear. (author)

  6. Radar-Enabled Recovery of the Sutters Mill Meteorite, a Carbonaceous Chondrite Regolith Breccia

    Science.gov (United States)

    Jenniskens, Petrus M.; Fries, Marc D.; Yin, Qing-Zhu; Zolensky, Michael E.; Krot, Alexander N.; Sandford, Scott A.; Sears, Derek; Beauford, Robert; Ebel, Denton S.; Friedrich, Jon M.; Nagashima, Kazuhide; Wimpenny, Josh; Yamakawa, Akane; Nishiizumi, Kunihiko; Hamajima, Yasunori; Caffee, Marc W.; Welten, Kees C.; Laubenstein, Matthias; Davis, Andrew M.; Simon, Steven B.; Heck, Phillipp R.; Young, Edward D.; Kohl, Issaku E.; Thiemens, Mark H.; Nunn, Morgan H.; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Cahill, Thomas A.; Lawton, Jonathan A.; Barnes, David; Steele, Andrew; Rochette, Pierre; Verosub, Kenneth L.; Gattacceca, Jerome

    2012-01-01

    Doppler weather radar imaging enabled the rapid recovery of the Sutter's Mill meteorite after a rare 4-kiloton of TNT-equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand's parameter = 2.8 +/- 0.3). Sutter's Mill is a regolith breccia composed of CM (Mighei)-type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted.

  7. An Ion Microprobe Study of Fractionated Sulfur Isotopes in Hydrothermal Sulfides of the Kaidun Meteorite Breccia

    Science.gov (United States)

    McSween, H. Y., Jr.; Riciputi, L. R.; Paterson, B. A.

    1996-03-01

    The Kaidun breccia contains diverse clasts of enstatite and carbonaceous chondrite, identified by their petrography and oxygen isotopic compositions. One distinctive lithology, classified as CM1 to reflect its CM parentage and highly altered state, contains texturally unusual pyrrhotite needles wrapped in sheaths of phyllosilicate, as well as aggregates and crosscutting veins of pentlandite. The unique textures and associated alteration minerals (serpentine, saponite, melanite garnet, framboidal magnetite) indicate that these sulfides formed in a precursor parent body by reactions with hydrothermal fluids at temperatures as high as 450 degrees C . The alteration conditions recorded by these clasts are extreme in comparison to other carbonaceous chondrites, and coated, jackstraw pyrrhotites are unknown from other meteorites. Thus, it is important to document the reaction products as completely as possible. Here we report the results of in situ analyses of sulfur isotopes in Kaidun pyrrhotite and pentlandite, obtained using a Cameca ims-4f ion microprobe.

  8. Radar-enabled recovery of the Sutter's Mill meteorite, a carbonaceous chondrite regolith breccia.

    Science.gov (United States)

    Jenniskens, Peter; Fries, Marc D; Yin, Qing-Zhu; Zolensky, Michael; Krot, Alexander N; Sandford, Scott A; Sears, Derek; Beauford, Robert; Ebel, Denton S; Friedrich, Jon M; Nagashima, Kazuhide; Wimpenny, Josh; Yamakawa, Akane; Nishiizumi, Kunihiko; Hamajima, Yasunori; Caffee, Marc W; Welten, Kees C; Laubenstein, Matthias; Davis, Andrew M; Simon, Steven B; Heck, Philipp R; Young, Edward D; Kohl, Issaku E; Thiemens, Mark H; Nunn, Morgan H; Mikouchi, Takashi; Hagiya, Kenji; Ohsumi, Kazumasa; Cahill, Thomas A; Lawton, Jonathan A; Barnes, David; Steele, Andrew; Rochette, Pierre; Verosub, Kenneth L; Gattacceca, Jérôme; Cooper, George; Glavin, Daniel P; Burton, Aaron S; Dworkin, Jason P; Elsila, Jamie E; Pizzarello, Sandra; Ogliore, Ryan; Schmitt-Kopplin, Phillipe; Harir, Mourad; Hertkorn, Norbert; Verchovsky, Alexander; Grady, Monica; Nagao, Keisuke; Okazaki, Ryuji; Takechi, Hiroyuki; Hiroi, Takahiro; Smith, Ken; Silber, Elizabeth A; Brown, Peter G; Albers, Jim; Klotz, Doug; Hankey, Mike; Matson, Robert; Fries, Jeffrey A; Walker, Richard J; Puchtel, Igor; Lee, Cin-Ty A; Erdman, Monica E; Eppich, Gary R; Roeske, Sarah; Gabelica, Zelimir; Lerche, Michael; Nuevo, Michel; Girten, Beverly; Worden, Simon P

    2012-12-21

    Doppler weather radar imaging enabled the rapid recovery of the Sutter's Mill meteorite after a rare 4-kiloton of TNT-equivalent asteroid impact over the foothills of the Sierra Nevada in northern California. The recovered meteorites survived a record high-speed entry of 28.6 kilometers per second from an orbit close to that of Jupiter-family comets (Tisserand's parameter = 2.8 ± 0.3). Sutter's Mill is a regolith breccia composed of CM (Mighei)-type carbonaceous chondrite and highly reduced xenolithic materials. It exhibits considerable diversity of mineralogy, petrography, and isotope and organic chemistry, resulting from a complex formation history of the parent body surface. That diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to C-class asteroids are interpreted. PMID:23258889

  9. Are the Clast Lithologies Contained in Lunar Breccia 64435 Mixtures of Anorthositic Magmas

    Science.gov (United States)

    Simon, J. I.; Mittlefehldt, D. W.; Peng, Z. X.; Nyquist, L. E.; Shih, C.-Y.; Yamaguchi, A.

    2015-01-01

    The anorthositic crust of the Moon is often used as the archtypical example of a primary planetary crust. The abundance and purity of anorthosite in the Apollo sample collection and remote sensing data are generally attributed to an early global magma ocean which produced widespread floating plagioclase cumulates (the ferroan anorthosites; FANs. Recent geochronology studies report evidence of young (less than 4.4 Ga) FAN ages, which suggest that either some may not be directly produced from the magma ocean or that the final solidification age of the magma ocean was younger than previous estimates. A greater diversity of anorthositic rocks have been identified among lunar meteorites as compared to returned lunar samples. Granted that these lithologies are often based on small clasts in lunar breccias and therefore may not represent their actual whole rock composition. Nevertheless, as suggested by the abundance of anorthositic clasts with Mg# [Mg/(Mg+Fe)] less than 0.80 and the difficulty of producing the extremely high plagioclase contents observed in Apollo samples and the remote sensing data, modification of the standard Lunar Magma Ocean (LMO) model may be in order. To ground truth mission science and to further test the LMO and other hypotheses for the formation of the lunar crust, additional coordinated petrology and geochronology studies of lunar anorthosites would be informative. Here we report new mineral chemistry and trace element geochemistry studies of thick sections of a composite of FAN-suite igneous clasts contained in the lunar breccia 64435 in order to assess the significance of this type of sample for petrogenetic studies of the Moon. This work follows recent isotopic studies of the lithologies in 64435 focusing on the same sample materials and expands on previous petrology studies who identified three lithologies in this sample and worked on thin sections.

  10. Uranium exploration target selection for proterozoic iron oxide/breccia complex type deposits in India

    International Nuclear Information System (INIS)

    Multimetal iron oxide/breccia complex (IOBC) type deposits exemplified by Olympic Dam in Australia, fall under low grade, large tonnage deposits. A multidisciplinary integrated exploration programme consisting of airborne surveys, ground geological surveys, geophysical and geochemical investigations and exploratory drilling, supported adequately by the state of the art analytical facilities, data processing using various software and digital image processing has shown moderate success in the identification of target areas for this type of deposits in the Proterozoic terrains of India. Intracratonic, anorogenic, continental rift to continental margin environment have been identified in a very wide spectrum of rock associations. The genesis and evolution of such associations during the Middle Proterozoic period have been reviewed and applied for target selection in the (i) Son-Narmada rift valley zone; (ii) areas covered by Dongargarh Supergroup of rocks in Madhya Pradesh; (iii) areas exposing ferruginous breccia in the western part of the Singhbhum Shear Zone (SSZ) around Lotapahar; (iv) Siang Group of rocks in Arunachal Pradesh; (v) Crystalline rocks of Garo Hills around Anek; and (vi) Chhotanagpur Gneissic complex in the Bahia-Ulatutoli tract of Ranchi Plateau. Of theses six areas, the Son-Narmada rift area appears to be the most promising area for IOBC type deposits. Considering occurrences of the uranium anomalies near Meraraich, Kundabhati, Naktu and Kudar and positive favourability criteria observed in a wide variety of rocks spatially related to the rifts and shears, certain sectors in Son-Narmada rift zone have been identified as promising for intense subsurface exploration. 20 refs, 4 figs, 1 tab

  11. Paragenesis and conditions of formation of ore minerals from metalliferous breccia pipes, N. Arizona

    International Nuclear Information System (INIS)

    Ore deposits within N. Arizona breccia pipes are currently being exploited for U, but at various times during the past century Cu, Pb, Zn, and Ag were mined. These pipes formed as solution-collapses within the Mississippian Redwall Ls and stopped upward through overlying strata. The principal ore minerals are: uraninite, chalcopyrite, chalcocite, tennantite-tetrahedrite, galena, sphalerite, millerite, gersdorffite, siegenite, and molybdenite. Common gangue minerals are marcasite, pyrite, barite, dolomite, calcite and quartz. Marcasite and pyrite appear to have formed prior to the ore minerals, followed closely by chalcopyrite. The Ni and Co phases also appear to be early: gersdorffite crystals are rimmed by later galena. Tennantite-tetrahedrite formed later than both galena and sphalerite; uraninite, the latest ore mineral, consisting fills interstices. Primary fluid inclusions in dolomite, quartz, and sphalerite show filling temperatures from 80 to 145 degree C and high salinities, averaging 15 wt% NaCl (eq). Secondary inclusions in sphalerite have consistently higher filling temperatures from 105 to 173 degree C, but similar salinities. Rock-Eval pyrolysis of pyrobitumen yields little or no volatile hydrocarbons (S1=0-0.2 mg/gm), but large amounts of pyrolytic hydrocarbons (S2=105-216 mg/gm). Temperatures of maximum pyrolytic yield are relatively low (424-430 degree C), suggesting temperatures did not exceed 150 degree C following pyrobitumen emplacement. Except for uraninite, the breccia pipes are similar to Mississippi Valley-type (MVT) deposits in mineralogy, fluid-inclusion filling temperatures and salinities, and associated organic material. Because MVT deposits do not host U minerals, a possible two-stage mineralization history of the pipes is suggested, the first by a MVT brine and perhaps a second forming the uraninite

  12. Multiple episodes of breccia formation by particle fluidization in fault zones: implications repeated, rupture-controlled fluid flow and seismicity styles

    Science.gov (United States)

    Cox, Stephen

    2016-04-01

    Breccias in the Rusey Fault (Cornwall, UK) provide insights about the dynamics of fault behaviour, fluid flow and flow velocities when fault ruptures breach overpressured reservoirs of hydrothermal fluid. The 3 m wide fault core comprises a mix of breccias, banded cataclasites, probable psuedotachylites and extension veins. The damage products are dominated by high dilation breccias with cockade-like textures in which rock fragments are mantled by spheroidal overgrowths of quartz. Although none of the rock fragment cores of accretionary spheroids are in contact with their neighbours, the spheroidal overgrowths do contact each other and are at least partially cemented together. The hydrothermal overgrowths mostly comprise either outwards coarsening crystals that radiate from the surface of the core particle, or finer-grained, inequigranular to mesh-like intergrowths. Concentric textural banding and oscillatory growth zones are present in some hydrothermal overgrowths. The breccias occur as fault-parallel layers and lenses, each up to several tens of centimeter thick. Adjacent layers are characterised by texturally-distinct ranges of clast sizes and different proportions of clasts to hydrothermal overgrowths. Many texturally-distinct breccia layers are present within the fault core. Some breccia layers truncate others and many breccia layers exhibit grainsize grading or banding. Clasts in the breccias include fragments of wall-rock, veins and various fault damage products, including fragments of earlier generations of cemented breccia. As brecciation was episodic and separated by periods of cementation, the breccias are interpreted to have formed as a consequence of repeated seismogenic failure. The distinctive textures in the breccias are interpreted to have formed by fluidization of fault damage products in a high fluid flux regime, with each breccia layer being the product of one, rupture-related flow episode. Hydrothermal coatings developed while clasts were in a

  13. Ries Bunte Breccia revisited: Indications for the presence of water in Itzing and Otting drill cores and implications for the emplacement process

    Science.gov (United States)

    Pietrek, Alexa; Kenkmann, Thomas

    2016-04-01

    We reassessed two drill cores of the Bunte Breccia deposits of the Ries crater, Germany. The objectives of our study were the documentation of evidence for water in the Bunte Breccia, the evaluation of how that water influenced the emplacement processes, and from which preimpact water reservoir it was derived. The Bunte Breccia in both cores can be structured into a basal layer composed mainly of local substrate material, overlain by texturally and compositionally diverse, crater-derived breccia units. The basal layer is composed of the youngest sediments (Tertiary clays and Upper Jurassic limestone) and has a razor-sharp boundary to the upper breccia units, which are composed of older rocks of Upper Jurassic to Upper Triassic age. Sparse material exchange occurred between the basal layer and the rest of the Bunte Breccia. Fluids predominantly came from the Tertiary and the Upper Triassic sandstone formation. In the basal layer, Tertiary clays were subjected to intense, ductile deformation, indicating saturation with water. This suggests that water was mixed into the matrix, creating a fluidized basal layer with a strong shear localization. In the upper units, Upper Triassic sandstones are intensely deformed by granular flow. The texture requires that the rocks were disaggregated into granular sand. Vaporization of pore water probably aided fragmentation of these rocks. In the Otting core, hot suevite (T > 600 °C) covered the Bunte Breccia shortly after its emplacement. Vertically oriented gas escape pipes in suevite partly emanate directly at the contact to the Bunte Breccia. They indicate that the Bunte Breccia contained a substantial amount of water in the upper part that was vaporized and escaped through these vents.

  14. Informe sobre ciegos:de la narración de Ernesto Sabato a la alucinación gráfica de Alberto Breccia

    Directory of Open Access Journals (Sweden)

    Giulia De Sarlo

    2015-07-01

    Full Text Available Alberto Breccia has been one of the fathers of twentieth century graphic narrative. Author of key works as El Eternauta (1969, his forays into the world of literature have been frequent since his début. At the end of his life, Breccia turned into comic the Informe sobre ciegos, central and autonomous chapter of Sobre héroes y tumbas (1961 by Ernesto Sabato. This work will analyse the dialogue that the graphic genius of Breccia establishes with the tormented Sabato’s voice, enriching the meaning of one of the most controversial passages of recent Latin American literature.

  15. Informe sobre ciegos:de la narración de Ernesto Sabato a la alucinación gráfica de Alberto Breccia

    OpenAIRE

    Giulia De Sarlo

    2015-01-01

    Alberto Breccia has been one of the fathers of twentieth century graphic narrative. Author of key works as El Eternauta (1969), his forays into the world of literature have been frequent since his début. At the end of his life, Breccia turned into comic the Informe sobre ciegos, central and autonomous chapter of Sobre héroes y tumbas (1961) by Ernesto Sabato. This work will analyse the dialogue that the graphic genius of Breccia establishes with the tormented Sabato’s voice, enriching the mea...

  16. AR-39Ar-40 dating of basalts and rock breccias from Apollo 17 and the malvern achondrite

    Science.gov (United States)

    Kirsten, T.; Horn, P.

    1977-01-01

    The principles and the potential of the Ar-39/Ar-40 dating technique are illustrated by means of results obtained for 12 Apollo 17 rocks. Emphasis is given to methodical problems and the geological interpretation of lunar rock ages. Often it is ambigious to associate a given lunar breccia with a certain formation, or a formation with a basin. In addition, large-scale events on the Moon have not necessarily reset radiometric clocks completely. One rock fragment has a well-defined plateau age of 4.28 b.y., but the ages of two Apollo 17 breccias define an upper limit for the formation age of the Serenitatis basin at 4.05 b.y. Ages derived from five mare basalts indicate cessation of mare volcanism at Taurus-Littrow approximately 3.78 b.y. ago. Ca/Ar-37 exposure ages show that Camelot Crater was formed by an impact approximately 95 m.y. ago. After a short summary of the lunar timetable as it stands at the end of the Apollo program, we report about Ar-39/Ar-40 and rare gas studies on the Malvern meteorite. This achondrite resembles lunar highland breccias in texture as well as in rare-gas patterns. It was strongly annealed at some time between 3.4 and 3.8 b.y. ago. The results indicate that very similar processes have occurred on the Moon and on achondritic parent bodies at comparable times, leading to impact breccias with strikingly similar features, including the retention of rare-gas isotopes from various sources.

  17. Effects of Hybrid Polypropylene-Steel Fiber Addition on Some Hardened Properties of Lightweight Concrete with Pumice Breccia Aggregate

    OpenAIRE

    Slamet Widodo; Iman Satyarno; Sri Tudjono

    2012-01-01

    Lightweight concrete application in construction field is growing rapidly in these recent years due to its advantages over ordinary concrete. In this paper, pumice breccia which can be found abundantly in Indonesia is proposed to be utilized as the coarse aggregate. In spite of its benefits, lightweight concrete exhibits more brittle characteristics and lower tensile strength compared with normal concrete. On the other hand, fiber addition into concrete has become widely used to improve its t...

  18. FORMATION OF GOLD-BEARING HYDROFRACTURING BRECCIA BODIES IN TECTONIC LENSES: A CASE STUDY ON SHUANGWANG GOLD DEPOSIT, SHAANXI, CHINA

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Macro-microscopic tectonic analysis and lithologic features show that the gold-bearing breccia bodies in the Shuangwang gold deposit, for hydrofracturing of the deep-sourced and alkali-rich fluids in the Devonian sodic rock series, are identified as hydrofracturing breccia bodies. Since the Indosinian,intracontinental collisional orogenesis results in multiple fracturings and magmatic emplacements in the Qinling area. Deep-sourced fluids resulting from deep fractures and granitoid magmatic intrusion are of a supercritical nature. Joint action between the fluid-rock system and structures leads to hydroffacturing and ore formation of the gold deposit.Firstly, the progressive coaxial compression caused the competent sodic rock series and the incompetent pelitic rock series to be deformed and partitioned. Lens-like weak-strain domains are hence formed and distributed at the approximate equidistance zones and the linear strong-strain zones,respectively. Subsequently, the progressive non-coaxial shearing and right-lateral and high-angle oblique thrusting lead to the most developed fracture system in the core of the weak-strain domain to turn from compression to extension and to link up with the deep fracture systems. The periodical huge pressure decline in the pumping center causes the deep-sourced confined fluids to develop periodic tectonic pumping, hydrofracturing and precipitation-healing in the sodic rock series. The gold-bearing hydrofracturing breccia bodies are hence ultimately formed at near-equidistance tectonic lenses. On the basis of the above model, the predicted concealed gold-bearing hydrofracturing breccia bodies have been preliminarily validated by latest drillings.

  19. A new style of Ni-Cu mineralization related to magmatic breccia pipes in a transpressional magmatic arc, Aguablanca, Spain

    OpenAIRE

    Tornos Arroyo, Fernando; Casquet, César; Galindo Francisco, Mª del Carmen; Velasco Roldán, Francisco; Canales Gallarosa, Ángel

    2001-01-01

    The Aguablanca deposit represents a new style of magmatic Ni Cu mineralization in discordant sulfide rich pyro xenitic breccia pipes. The orebody is hosted by Variscan calc alkaline diorites and gabbros which intruded during an oblique subduction/collision event. Transpressional transtensional left lateral structures facilitated the intrusion of primitive magmas to shallow depths in the crust. A two stage genetic model is proposed. In the first stage, a transitional deep ...

  20. Geological setting and timing of the Chah Zard breccia-hosted epithermal gold-silver deposit in the Tethyan belt of Iran

    Science.gov (United States)

    Kouhestani, Hossein; Ghaderi, Majid; Zaw, Khin; Meffre, Sebastien; Emami, Mohammad Hashem

    2012-04-01

    The breccia-hosted epithermal gold-silver deposit of Chah Zard is located within a high-K, calc-alkaline andesitic to rhyolitic volcanic complex in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA), west central Iran. The total measured resource for Chah Zard is ˜2.5 million tonnes of ore at 12.7 g/t Ag and 1.7 g/t Au (28.6 t Ag, 3.8 t Au), making it one of the largest epithermal gold deposits in Iran. Magmatic and hydrothermal activity was associated with local extensional tectonics in a strike-slip regime formed in transtensional structures of the Dehshir-Baft strike-slip fault system. The host rocks of the volcanic complex consist of Eocene sedimentary and volcanic rocks covered by Miocene sedimentary rocks. LA-ICP-MS U-Pb zircon geochronology yields a mean age of 6.2 ± 0.2 Ma for magmatic activity at Chah Zard. This age represents the maximum age of mineralization and may indicate a previously unrecognized mineralization event in the UDMA. Breccias and veins formed during and after the waning stages of explosive brecciation events due to shallow emplacement of rhyolite porphyry. Detailed systematic mapping leads to the recognition of three distinct breccia bodies: volcaniclastic breccia with a dominantly clastic matrix; gray polymict breccia with a greater proportion of hydrothermal cement; and mixed monomict to polymict breccia with clay matrix. The polymictic breccias generated bulk-mineable ore, whereas the volcaniclastic breccia is relatively impermeable and largely barren. Precious metals occur with sulfide and sulfosalt minerals as disseminations, as well as in the veins and breccia cements. There is a progression from pyrite-dominated (stage 1) to pyrite-base metal sulfide and sulfosalt-dominated (stages 2 and 3) to base metal sulfide-dominated (stage 4) breccias and veins. Hydrothermal alteration and deposition of gangue minerals progressed from illite-quartz to quartz-adularia, carbonate, and finally gypsum-dominated assemblages. Free gold

  1. Petrography and composition of Martian regolith breccia meteorite Northwest Africa 7475

    Science.gov (United States)

    Wittmann, Axel; Korotev, Randy L.; Jolliff, Bradley L.; Irving, Anthony J.; Moser, Desmond E.; Barker, Ivan; Rumble, Douglas

    2015-02-01

    The Northwest Africa (NWA) 7475 meteorite is one of the several stones of paired regolith breccias from Mars based on petrography, oxygen isotope, mineral compositions, and bulk rock compositions. Its inventory of lithic clasts is dominated by vitrophyre impact melts that were emplaced while they were still molten. Other clast types include crystallized impact melt rocks, evolved plutonic rocks, possible basalts, contact metamorphosed rocks, and siltstones. Impact spherules and vitrophyre shards record airborne transport, and accreted dust rims were sintered on most clasts, presumably during residence in an ejecta plume. The clast assemblage records at least three impact events, one that formed an impact melt sheet on Mars ≤4.4 Ga ago, a second that assembled NWA 7475 from impactites associated with the impact melt sheet at 1.7-1.4 Ga, and a third that launched NWA 7475 from Mars ~5 Ma ago. Mildly shocked pyroxene and plagioclase constrain shock metamorphic conditions during launch to >5 and <15 GPa. The mild postshock-heating that resulted from these shock pressures would have been insufficient to sterilize this water-bearing lithology during launch. Magnetite, maghemite, and pyrite are likely products of secondary alteration on Mars. Textural relationships suggest that calcium-carbonate and goethite are probably of terrestrial origin, yet trace element chemistry indicates relatively low terrestrial alteration. Comparison of Mars Odyssey gamma-ray spectrometer data with the Fe and Th abundances of NWA 7475 points to a provenance in the ancient southern highlands of Mars. Gratteri crater, with an age of ~5 Ma and an apparent diameter of 6.9 km, marks one possible launch site of NWA 7475.

  2. Osmium isotope and highly siderophile element systematics of lunar impact melt breccias: Implications for the late accretion history of the Moon and Earth

    Science.gov (United States)

    Puchtel, I.S.; Walker, R.J.; James, O.B.; Kring, D.A.

    2008-01-01

    To characterize the compositions of materials accreted to the Earth-Moon system between about 4.5 and 3.8 Ga, we have determined Os isotopic compositions and some highly siderophile element (HSE: Re, Os, Ir, Ru, Pt, and Pd) abundances in 48 subsamples of six lunar breccias. These are: Apollo 17 poikilitic melt breccias 72395 and 76215; Apollo 17 aphanitic melt breccias 73215 and 73255; Apollo 14 polymict breccia 14321; and lunar meteorite NWA482, a crystallized impact melt. Plots of Ir versus other HSE define excellent linear correlations, indicating that all data sets likely represent dominantly two-component mixtures of a low-HSE target, presumably endogenous component, and a high-HSE, presumably exogenous component. Linear regressions of these trends yield intercepts that are statistically indistinguishable from zero for all HSE, except for Ru and Pd in two samples. The slopes of the linear regressions are insensitive to target rock contributions of Ru and Pd of the magnitude observed; thus, the trendline slopes approximate the elemental ratios present in the impactor components contributed to these rocks. The 187Os/188Os and regression-derived elemental ratios for the Apollo 17 aphanitic melt breccias and the lunar meteorite indicate that the impactor components in these samples have close affinities to chondritic meteorites. The HSE in the Apollo 17 aphanitic melt breccias, however, might partially or entirely reflect the HSE characteristics of HSE-rich granulitic breccia clasts that were incorporated in the impact melt at the time of its creation. In this case, the HSE characteristics of these rocks may reflect those of an impactor that predated the impact event that led to the creation of the melt breccias. The impactor components in the Apollo 17 poikilitic melt breccias and in the Apollo 14 breccia have higher 187Os/188Os, Pt/Ir, and Ru/Ir and lower Os/Ir than most chondrites. These compositions suggest that the impactors they represent were chemically

  3. A Late Mesoproterozoic 40Ar/39Ar age for a melt breccia from the Keurusselkä impact structure, Finland

    Science.gov (United States)

    Schmieder, Martin; Jourdan, Fred; Moilanen, Jarmo; Buchner, Elmar; Öhman, Teemu

    2016-02-01

    Field investigations in the eroded central uplift of the ≤30 km Keurusselkä impact structure, Finland, revealed a thin, dark melt vein that intersects the autochthonous shatter cone-bearing target rocks near the homestead of Kirkkoranta, close to the center of the impact structure. The petrographic analysis of quartz in this melt breccia and the wall rock granite indicate weak shock metamorphic overprint not exceeding ~8-10 GPa. The mode of occurrence and composition of the melt breccia suggest its formation as some kind of pseudotachylitic breccia. 40Ar/39Ar dating of dark and clast-poor whole-rock chips yielded five concordant Late Mesoproterozoic miniplateau ages and one plateau age of 1151 ± 10 Ma [± 11 Ma] (2σ; MSWD = 0.11; P = 0.98), considered here as the statistically most robust age for the rock. The new 40Ar/39Ar age is incompatible with ~1.88 Ga Svecofennian tectonism and magmatism in south-central Finland and probably reflects the Keurusselkä impact, followed by impact-induced hydrothermal chloritization of the crater basement. In keeping with the crosscutting relationships in the outcrop and the possible influence of postimpact alteration, the Late Mesoproterozoic 40Ar/39Ar age of ~1150 Ma should be treated as a minimum age for the impact. The new 40Ar/39Ar results are consistent with paleomagnetic results that suggested a similar age for Keurusselkä, which is shown to be one of the oldest impact structures currently known in Europe and worldwide.

  4. Plutonium-244 dating: Initial ratios of plutonium to uranium in the Apollo 11 and 14 lunar fines and breccias

    International Nuclear Information System (INIS)

    More than 550 mass-spectrometric analyses of xenon released from bulk samples and temperature fractions of the lunar fines, breccias and rocks have been carried out in various laboratories in the world including the Soviet Union, since Apollo 11 astronauts made the first successful landing on the moon on 20 July 1969. Re-examination of all the known xenon isotope data for the lunar samples reveals that the moon started to retain her xenon at about the same time as the carbonaceous chondrites, when the initial ratio of Pu to U within the solar system was about 1 to 10 (atom/atom) more than 4,800 million years ago

  5. The Donoso copper-rich, tourmaline-bearing breccia pipe in central Chile: petrologic, fluid inclusion and stable isotope evidence for an origin from magmatic fluids

    Science.gov (United States)

    Skewes, M. Alexandra; Holmgren, Carmen; Stern, Charles R.

    2003-01-01

    The copper-rich, tourmaline-bearing Donoso breccia pipe is one among more than 15 different mineralized breccias in the giant (>50 million metric tonnes of copper) Miocene and Pliocene Río Blanco-Los Bronces copper deposit in the high Andes of central Chile. This breccia pipe, bracketed in age between 5.2 and 4.9 Ma, has dimensions of 500 by 700 m at the current surface 3,670 m above sea level. Its roots have yet to be encountered, and it is >300 m in diameter at the depth of the deepest drill holes. The Donoso breccia is, for the most part, monolithic, containing clasts of the equigranular quartz monzonite pluton which hosts the pipe. It is matrix supported, with between 5 and 25% of the total rock volume consisting of breccia-matrix minerals, which include tourmaline, quartz, chalcopyrite, pyrite, specularite, and lesser amounts of bornite and anhydrite. An open pit mine, centered on this breccia pipe, has a current production of 50,000 tonnes of ore per day at an average grade of 1.2% copper, and copper grade in the breccia matrix is significantly higher. Measured δ18O for tourmaline and quartz from the matrix of the Donoso breccia at different levels of the pipe range from +6.9 to +12.0‰, and measured δD in tourmaline ranges from -73 to -95‰. Temperatures of crystallization of these minerals, as determined by the highest homogenization temperatures of highly saline fluid inclusions, range from 400 to >690°C. When corrected for these temperatures, the stable isotope data indicate that fluids from which these breccia-matrix minerals precipitated were magmatic, with δ18O between +5.6 to +9.1‰ and δD between -51 to -80‰. These isotopic data preclude participation of a significant amount of meteoric water in the formation of the Donoso breccia. They support a model in which brecciation is caused by expansion of magmatic fluids exsolved from a cooling pluton, and breccia-matrix minerals, including copper sulfides, precipitated from the same magmatic

  6. Rb-Sr and Sm-Nd isotopic and REE studies of igneous components in the bulk matrix domain of Martian breccia Northwest Africa 7034

    Science.gov (United States)

    Nyquist, Laurence E.; Shih, Chi-Yu; McCubbin, Francis M.; Santos, Alison R.; Shearer, Charles K.; Peng, Zhan X.; Burger, Paul V.; Agee, Carl B.

    2016-03-01

    The bulk matrix domain of the Martian breccia NWA 7034 was examined petrographically and isotopically to better understand the provenance and age of the source material that make up the breccia. Both 147Sm-143Nd and 146Sm-142Nd age results for mineral separates from the bulk matrix portion of breccia NWA 7034 suggest that various lithological components in the breccia probably formed contemporaneously ~4.44 Ga ago. This old age is in excellent agreement with the upper intersection ages (4.35-4.45 Ga) for U-Pb discordia and also concordia defined by zircon and baddeleyite grains in matrix and igneous-textured clasts. Consequently, we confirm an ancient age for the igneous components that make up the NWA 7034 breccia. Substantial disturbance in the Rb-Sr system was detected, and no age significance could be gleaned from our Rb-Sr data. The disturbance to the Rb-Sr system may be due to a thermal event recorded by bulk-rock K-Ar ages of 1.56 Ga and U-Pb ages of phosphates at about 1.35-1.5 Ga, which suggest partial resetting from an unknown thermal event(s), possibly accompanying breccia formation. The NWA 7034 bulk rock is LREE enriched and similar to KREEP-rich lunar rocks, which indicates that the earliest Martian crust was geochemically enriched. This enrichment supports the idea that the crust is one of the enriched geochemical reservoirs on Mars that have been detected in studies of other Martian meteorites.

  7. Magnetostratigraphy of the impact breccias and post-impact carbonates from borehole Yaxcopoil-1, Chicxulub impact crater, Yucatán, Mexico

    Science.gov (United States)

    Rebolledo-Vieyra, Mario; Urrutia-Fucugauchi, Jaime

    2004-06-01

    We report the magnetostratigraphy of the sedimentary sequence between the impact breccias and the post-impact carbonate sequence conducted on samples recovered by Yaxcopoil-1 (Yax-1). Samples of impact breccias show reverse polarities that span up to ~56 cm into the postimpact carbonate lithologies. We correlate these breccias to those of PEMEX boreholes Yucatán-6 and Chicxulub-1, from which we tied our magnetostratigraphy to the radiometric age from a melt sample from the Yucatán-6 borehole. Thin section analyses of the carbonate samples showed a significant amount of dark minerals and glass shards that we identified as the magnetic carriers; therefore, we propose that the mechanism of magnetic acquisition within the carbonate rocks for the interval studied is detrital remanent magnetism (DRM). With these samples, we constructed the scale of geomagnetic polarities where we find two polarities within the sequence, a reverse polarity event within the impact breccias and the base of the post-impact carbonate sequence (up to 794.07 m), and a normal polarity event in the last ~20 cm of the interval studied. The polarities recorded in the sequence analyzed are interpreted to span from chron 29r to 29n, and we propose that the reverse polarity event lies within the 29r chron. The magnetostratigraphy of the sequence studied shows that the horizon at 794.11 m deep, interpreted as the K/T boundary, lies within the geomagnetic chron 29r, which contains the K/T boundary.

  8. Petrology and geochemistry of feldspathic impact-melt breccia Abar al' Uj 012, the first lunar meteorite from Saudi Arabia

    Science.gov (United States)

    MéSzáRos, Marianna; Hofmann, Beda A.; Lanari, Pierre; Korotev, Randy L.; Gnos, Edwin; Greber, Nicolas D.; Leya, Ingo; Greenwood, Richard C.; Jull, A. J. Timothy; Al-Wagdani, Khalid; Mahjoub, Ayman; Al-Solami, Abdulaziz A.; Habibullah, Siddiq N.

    2016-08-01

    Abar al' Uj (AaU) 012 is a clast-rich, vesicular impact-melt (IM) breccia, composed of lithic and mineral clasts set in a very fine-grained and well-crystallized matrix. It is a typical feldspathic lunar meteorite, most likely originating from the lunar farside. Bulk composition (31.0 wt% Al2O3, 3.85 wt% FeO) is close to the mean of feldspathic lunar meteorites and Apollo FAN-suite rocks. The low concentration of incompatible trace elements (0.39 ppm Th, 0.13 ppm U) reflects the absence of a significant KREEP component. Plagioclase is highly anorthitic with a mean of An96.9Ab3.0Or0.1. Bulk rock Mg# is 63 and molar FeO/MnO is 76. The terrestrial age of the meteorite is 33.4 ± 5.2 kyr. AaU 012 contains a ~1.4 × 1.5 mm2 exotic clast different from the lithic clast population which is dominated by clasts of anorthosite breccias. Bulk composition and presence of relatively large vesicles indicate that the clast was most probably formed by an impact into a precursor having nonmare igneous origin most likely related to the rare alkali-suite rocks. The IM clast is mainly composed of clinopyroxenes, contains a significant amount of cristobalite (9.0 vol%), and has a microcrystalline mesostasis. Although the clast shows similarities in texture and modal mineral abundances with some Apollo pigeonite basalts, it has lower FeO and higher SiO2 than any mare basalt. It also has higher FeO and lower Al2O3 than rocks from the FAN- or Mg-suite. Its lower Mg# (59) compared to Mg-suite rocks also excludes a relationship with these types of lunar material.

  9. K-Ca Dating of Alkali-Rich Fragments in the Y-74442 and Bhola LL-Chondritic Breccias

    Science.gov (United States)

    Yokoyama, T; Misawa, K.; Okano, O; Shih, C. -Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2013-01-01

    Alkali-rich igneous fragments in the brecciated LL-chondrites, Krahenberg (LL5) [1], Bhola (LL3-6) [2], Siena (LL5) [3] and Yamato (Y)-74442 (LL4) [4-6], show characteristic fractionation patterns of alkali and alkaline elements [7]. The alkali-rich fragments in Krahenberg, Bhola and Y-74442 are very similar in mineralogy and petrography, suggesting that they could have come from related precursor materials [6]. Recently we reported Rb-Sr isotopic systematics of alkali-rich igneous rock fragments in Y-74442: nine fragments from Y-74442 yield the Rb-Sr age of 4429 plus or minus 54 Ma (2 sigma) for lambda(Rb-87) = 0.01402 Ga(exp -1) [8] with the initial ratio of Sr-87/Sr-86 = 0.7144 plus or minus 0.0094 (2 sigma) [9]. The Rb-Sr age of the alkali-rich fragments of Y-74442 is younger than the primary Rb-Sr age of 4541 plus or minus 14 Ma for LL-chondrite whole-rock samples [10], implying that they formed after accumulation of LL-chondrite parental bodies, although enrichment may have happened earlier. Marshall and DePaolo [11,12] demonstrated that the K-40 - Ca-40 decay system could be an important chronometer as well as a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [13,14] and more recently Simon et al. [15] determined K-Ca ages of lunar granitic rocks, and showed the application of the K-Ca chronometer for K-rich planetary materials. Since alkali-rich fragments in the LL-chondritic breccias are highly enriched in K, we can expect enhancements of radiogenic Ca-40. Here, we report preliminary results of K-Ca isotopic systematics of alkali-rich fragments in the LL-chondritic breccias, Y-74442 and Bhola.

  10. The Galim LL/EH Polymict Breccia: Evidence for Impact-Induced Exchange Between Reduced and Oxidized Meteoritic Material

    Science.gov (United States)

    Rubin, Alan E.

    1997-01-01

    Galim is a polymict breccia consisting of a heavily shocked (shock stage S6) LL6 chondrite, Galim (a), and an impact-melted EH chondrite, Galim (b). Relict chondrules in Galim (b) served as nucleation sites for euhedral enstatite grains crystallizing from the impact melt. Many of the reduced phases typical of EH chondrites (e.g., Si-bearing metallic Fe-Ni; Ti-bearing troilite) are absent. Galim (b) was probably shock-melted while in contact with a more oxidized source, namely, Galim (a); during this event, Si was oxidized from the metal and Ti was oxidized from troilite. Galim (a) contains shock veins and recrystallized, unzoned olivine. The absence of evidence for reduction in Galim (a) may indicate that the amount of LL material greatly exceeded that of EH material; shock metamorphism may have taken place on the LL parent body. Shock-induced redox reactions such as those inferred for the Galim breccia appear to be restricted mainly to asteroids because the low-end tail of their relative-velocity distribution permits mixing of intact disparate materials (including accretion of projectiles of different oxidation states), whereas the peak of the distribution leads to high equilibration shock pressures (allowing impact-induced exchange between previously accreted, disequilibrated materials). Galim probably formed by a two-stage process: (I) accretion to the LL parent body of an intact EH projectile at low relative velocities, and (2) shock metamorphism of the assemblage by the subsequent impact of another projectile at significantly higher relative velocities.

  11. Identification of New Lithic Clasts in Lunar Breccia 14305 by Micro-CT and Micro-XRF Analysis

    Science.gov (United States)

    Zeigler, Ryan A.; Carpenter, Paul K.; Jolliff, Bradley L.

    2014-01-01

    From 1969 to 1972, Apollo astronauts collected 382 kg of rocks, soils, and core samples from six locations on the surface of the Moon. The samples were initially characterized, largely by binocular examination, in a custom-built facility at Johnson Space Center (JSC), and the samples have been curated at JSC ever since. Despite over 40 years of study, demand for samples remains high (500 subsamples per year are allocated to scientists around the world), particularly for plutonic (e.g., anorthosites, norites, etc.) and evolved (e.g., granites, KREEP basalts) lithologies. The reason for the prolonged interest is that as new scientists and new techniques examine the samples, our understanding of how the Moon, Earth, and other inner Solar System bodies formed and evolved continues to grow. Scientists continually clamor for new samples to test their emerging hypotheses. Although all of the large Apollo samples that are igneous rocks have been classified, many Apollo samples are complex polymict breccias that have previously yielded large (cm-sized) igneous clasts. In this work we present the initial efforts to use the non-destructive techniques of micro-computed tomography (micro-CT) and micro x-ray fluorescence (micro-XRF) to identify large lithic clasts in Apollo 14 polymict breccia sample 14305. The sample in this study is 14305,483, a 150 g slab of regolith breccia 14305 measuring 10x6x2 cm (Figure 1a). The sample was scanned at the University of Texas High-Resolution X-ray CT Facility on an Xradia MicroXCT scanner. Two adjacent overlapping volumes were acquired at 49.2 micrometer resolution and stitched together, resulting in 1766 slices. Each volume was acquired at 100 kV accelerating voltage and 98 mA beam current with a 1 mm CaF2 filter, with 2161 views gathered over 360deg at 3 seconds acquisition time per view. Micro-XRF analyses were done at Washington University in St. Louis, Missouri on an EDAX Orbis PC micro-XRF instrument. Multiple scans were made at 40 k

  12. Deep-seated fragmentation, transport of breccia dikes and emplacement: An example from the Borborema province, northeastern Brazil

    Science.gov (United States)

    Ferreira, Valderez P.; Sial, Alcides N.; Weinberg, Roberto F.; Pimentel, Marcio M.

    2015-03-01

    Three syenite dike sets, named the Santa Cruz dikes, are coeval with the 627 ± 13 Ma old porphyritic calc-alkalic Princesa Izabel granitoid, northeastern Brazil. Dike set 1 is up to 1.5 m wide, strike 030-040 Az, roughly parallel to the regional foliation. Dike set 2 strikes 120°-130 Az and consists of xenolith-bearing syenites and is roughly parallel to dike set 3, which is up to 1.5 m wide and consists of xenolith-rich syenites forming matrix-supported breccias. Xenoliths in dike sets 2 and 3 are usually up to 3 cm long, angular to sub-rounded, tend to be evenly distributed and occupy ˜50% of the volume of dike set 3. They are amphibolite, mica-pyroxenite and diorite from deep source, and gneiss and feldspar xenocrysts from the conduit. The large amount of dense ultramafic/mafic xenoliths in the breccia dikes indicates rapid ascent of the host magma. The calculated natural viscosity, based on whole-rock chemical data, is 680-4600 Pa.s for 2.3 wt% water and temperatures from 1000 to 900 °C, respectively. A minimum ascent rate of ˜0.3 m/s is estimated from the settling velocity of a 30 cm-long diorite xenolith, the largest one, and an initial fraction of xenoliths of 5%. Progressive addition of xenoliths to the magma during its ascent increased the viscosity of the liquid-solid mixture during emplacement, and this would imply a Bingham rather than Newtonian behavior. These xenoliths were formed by early fracturing of wall rocks during dike propagation associated with thermal spalling of the wall rocks, by intrusion of magma along dike-parallel fractures during the development of a sequential conjugate pair of shear zones. Xenoliths are abundant not only because these magmas have ascended rapidly and could transport them, but also because the initial low viscosity of the magma promoted intense fracturing of the conduit.

  13. Experiment on water-rock interaction between felsic crypto-explosive breccia and basement rock and its geological significance in Jiangxi and Fujian provinces

    International Nuclear Information System (INIS)

    For the sake of study geochemical behavior of active U, Th, Pb, Zn elements in rocks, an experiment on water-rock interaction between felsic crypto-explosive breccia and basement rock from uranium deposit No. 570 in north Fujian, uranium deposit No. 6722 in south Jiangxi, Yinshan Polymetallic deposit in Jiangxi is conducted with the solution conditions of pH=1.9, ΣS=3.2x10-4, ΣCl=3.5 x 10-4, ΣF=3 x 10-5, t=90 degree C. The experiment result shows that U, Zn, Pb elements in rocks have stronger activation migration power, metasomatic alteration has important significance for the migration and enrichment of U, main ore formation material is not derived from felsic crypto-explosive breccia, and the basement rocks play an important role in ore formation

  14. Carbon and oxygen isotope study of carbonates from highly shocked clasts of the polymict breccia of the Haughton Crater (Canada)

    Science.gov (United States)

    Agrinier, P.; Martinez, I.; Javoy, M.; Schaerer, U.

    1992-01-01

    It is known that the release of volatiles on impact is an important controlling factor in cratering processes in carbonate terranes and in the mobility of chemical elements. In order to assess the nature and the role of carbon- and oxygen-bearing volatiles during impact-induced metamorphism of sedimentary rocks, the C-13/C-12 and O-18/O-16 ratios and carbonate contents were determined for 30 shocked clasts from the Haughton Crater polymict breccia as well as for some unshocked carbonates from the sedimentary cover adjacent to the crater. Shock-induced CO2 loss during decarbonation of calcite is known to be a function of peak pressure and ambient partial pressure of the volatile species. In our clast samples, shocked from 20 to 60 GPa, we expect about 20 to 100 percent CO2 loss and preferential depletion in C-13 and O-18 in the residual carbonate. Rayleigh model (progressive loss of CO2) and batch model (single-step loss of CO2) curves for this depletion are shown. The magnitudes of the C-13 and O-18 depletions increase with the increase of the CO2 loss. In addition, the isotopic depletions should be correlated with an enrichment in CaO and MgO in the residual solid.

  15. Early Solar System Alkali Fractionation Events Recorded by K-Ca Isotopes in the Yamato-74442 LL-Chondritic Breccia

    Science.gov (United States)

    Tatsunori, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.

    2015-01-01

    Radiogenic ingrowth of Ca-40 due to decay of K-40 occurred early in the solar system history causing the Ca-40 abundance to vary within different early-former reservoirs. Marshall and DePaolo ] demonstrated that the K-40/Ca-40 decay system could be a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [3,4] determined 40K/40Ca ages of lunar granitic rock fragments and discussed the chemical characteristics of their source materials. Recently, Yokoyama et al. [5] showed the application of the K-40/Ca-40 chronometer for high K/Ca materials in ordinary chondrites (OCs). High-precision calcium isotopic data are needed to constrain mixing processes among early solar system materials and the time of planetesimal formation. To better constrain the solar system calcium isotopic compositions among astromaterials, we have determined the calcium isotopic compositions of OCs and an angrite. We further estimated a source K/Ca ratio for alkali-rich fragments in a chondritic breccia using the estimated solar system initial Ca-40/Ca-44.

  16. The Cantarell Breccia System, Southern Gulf Of Mexico: Structural Evolution And Support For An Origin Relarted To The Chixculub Meteorite Impact

    Science.gov (United States)

    Ricoy, V.

    2003-04-01

    The Upper Cretaceous within the Campeche Basin, southern Gulf of Mexico hosts a world class petroleum system. Cantarell is the most important reservoir that consists of a complex brecciated carbonate reservoir deposited at or around the Cretaceous-Tertiary boundary. Previous sedimentological studies suggests that the Upper Cretaceous Carbonate breccias found in the Cantarell oilfield system and through the Bay of Campeche, were the result of a catastrophic shelf collapse event triggered by the Chixculub meteorite impact. This work presents new evidence from structural and stratigraphic interpretation of 3D seismic and 2D lines which gives light to features that support the platform collapse model. The reservoir consists of thick (up to 300 m), heterogeneous, monomyctic and polymictic breccias developed at the K-T boundary, and widely distributed throughout the Campeche Basin. The timing, internal architecture, widespread deposition and distance to the platform margin source (over 30 kms) of the breccia unit, combined with a contorted irregular seismic reflector near the base of the Cretaceous carbonate platform, suggests that the geological processes accountable for the emplacement of the breccias relates to the massive catastrophic collapse of the Cretaceous platform as a result of the Chixculub meteorite impact. Structural interpretation of the 3D seismic data, together with well stratigraphic markers unraveled a complex Oligocene-Miocene structural deformation history of the Cantarell field, which resulted in several discrete reservoir blocks partitioned by a complex array of thrusts, normal and reverse faults. It is proposed that the structural deformation of the area controlled to a large extent the distribution of the reservoir properties found in the Cantarell area. This idea is tested using the structural model matched against the well log porosity data.

  17. Origin of sulfide replacement textures in lunar breccias. Implications for vapor element transport in the lunar crust

    Science.gov (United States)

    Shearer, C. K.; Burger, P. V.; Guan, Y.; Papike, J. J.; Sutton, S. R.; Atudorei, N.-V.

    2012-04-01

    Lunar samples 67016,294, 67915,150, and 67016,297 represent clasts of Mg-suite and ferroan anorthosite lithologies that have interacted with a S-rich vapor. Numerous studies have speculated on the composition and source of these “fluids”, their capability for the transport of vapor-mobilized elements, and the scale and environment under which these types of process occurred. These models all assumed a Moon with a very “dry” mantle, crust, and surface. The olivine in these lithologies is partially to totally replaced by troilite and low-Ca pyroxene. The troilite makes up 30-54 vol% of the troilite + low-Ca pyroxene pseudomorphs after olivine. Other silicates and oxides in the assemblages have experienced post-magmatic reequilibration (pyroxene exsolution, recrystallization, “exsolution” of ilmenite in spinel). The troilite also occurs in veins cross cutting individual phases and metamorphic textures. The sulfide veining and replacement features are restricted to individual clasts and do not cut across the matrix surrounding the clasts, and thus predate the breccia-forming event. The proportion of troilite to low-Ca pyroxene and silicate chemistries indicate that simple reactions (such as olivine + S2 ↔ low-Ca pyroxene + troilite + O2) do not adequately represent the replacement process. The sulfides have compositions that are similar to those found in mare basalts. In particular, the sulfides generally are enriched in Co relative to Ni. Exsolution of Ni-Co-Cu in the sulfides is distinctly different between the breccias and mare basalts and suggests a different cooling or crystallization (melt versus vapor) history. The sulfur isotopic composition of the vein and replacement troilite ranges from approximately δ34S = -1.0‰ to -3.3‰. Based on our observations, it appears that the model suggested by Norman et al. (1995) is the most appropriate for the origin of the troilite veining and troilite-pyroxene pseudomorphs after olivine. Our data add

  18. Origin of sulfide replacement textures in lunar breccias. Implications for vapor element transport in the lunar crust

    Energy Technology Data Exchange (ETDEWEB)

    Shearer, C.K.; Burger, P.V.; Guan, Y.; Papike, J.J.; Sutton, S.R.; Atudorei, N.-V. (UNM); (CIT); (UC)

    2012-05-09

    Lunar samples 67016,294, 67915,150, and 67016,297 represent clasts of Mg-suite and ferroan anorthosite lithologies that have interacted with a S-rich vapor. Numerous studies have speculated on the composition and source of these 'fluids', their capability for the transport of vapor-mobilized elements, and the scale and environment under which these types of process occurred. These models all assumed a Moon with a very 'dry' mantle, crust, and surface. The olivine in these lithologies is partially to totally replaced by troilite and low-Ca pyroxene. The troilite makes up 30-54 vol% of the troilite + low-Ca pyroxene pseudomorphs after olivine. Other silicates and oxides in the assemblages have experienced post-magmatic reequilibration (pyroxene exsolution, recrystallization, 'exsolution' of ilmenite in spinel). The troilite also occurs in veins cross cutting individual phases and metamorphic textures. The sulfide veining and replacement features are restricted to individual clasts and do not cut across the matrix surrounding the clasts, and thus predate the breccia-forming event. The proportion of troilite to low-Ca pyroxene and silicate chemistries indicate that simple reactions (such as olivine + S{sub 2} {leftrightarrow} low-Ca pyroxene + troilite + O{sub 2}) do not adequately represent the replacement process. The sulfides have compositions that are similar to those found in mare basalts. In particular, the sulfides generally are enriched in Co relative to Ni. Exsolution of Ni-Co-Cu in the sulfides is distinctly different between the breccias and mare basalts and suggests a different cooling or crystallization (melt versus vapor) history. The sulfur isotopic composition of the vein and replacement troilite ranges from approximately {delta}{sup 34}S = -1.0{per_thousand} to -3.3{per_thousand}. Based on our observations, it appears that the model suggested by Norman et al. (1995) is the most appropriate for the origin of the troilite

  19. Tracing early breccia pipe studies, Waste Isolation Pilot Plant, southeastern New Mexico: A study of the documentation available and decision-making during the early years of WIPP

    Energy Technology Data Exchange (ETDEWEB)

    Power, D.W. [HC 12, Anthony, TX (United States)

    1996-01-01

    Breccia pipes in southeastern New Mexico are local dissolution-collapse features that formed over the Capitan reef more than 500,000 years ago. During early site studies for the Waste Isolation Pilot Plant (WIPP), the threat to isolation by these features was undetermined. Geophysical techniques, drilling, and field mapping were used beginning in 1976 to study breccia pipes. None were found at the WIPP site, and they are considered unlikely to be a significant threat even if undetected. WIPP documents related to breccia pipe studies were assembled, inspected, and analyzed, partly to present a history of these studies. The main objective is to assess how well the record reflects the purposes, results, and conclusions of the studies from concept to decision-making. The main record source was the Sandia WIPP Central File (SWCF). Early records (about 1975 to 1977) are very limited, however, about details of objectives and plans predating any investigation. Drilling programs from about 1977 were covered by a broadly standardized statement of work, field operations plan, drilling history, and basic data report. Generally standardized procedures for peer, management, and quality assurance review were developed during this time. Agencies such as the USGS conducted projects according to internal standards. Records of detailed actions for individual programs may not be available, though a variety of such records were found in the SWCF. A complete written record cannot be reconstructed. With persistence, a professional geologist can follow individual programs, relate data to objectives (even if implied), and determine how conclusions were used in decision-making. 83 refs.

  20. Tracing early breccia pipe studies, Waste Isolation Pilot Plant, southeastern New Mexico: A study of the documentation available and decision-making during the early years of WIPP

    International Nuclear Information System (INIS)

    Breccia pipes in southeastern New Mexico are local dissolution-collapse features that formed over the Capitan reef more than 500,000 years ago. During early site studies for the Waste Isolation Pilot Plant (WIPP), the threat to isolation by these features was undetermined. Geophysical techniques, drilling, and field mapping were used beginning in 1976 to study breccia pipes. None were found at the WIPP site, and they are considered unlikely to be a significant threat even if undetected. WIPP documents related to breccia pipe studies were assembled, inspected, and analyzed, partly to present a history of these studies. The main objective is to assess how well the record reflects the purposes, results, and conclusions of the studies from concept to decision-making. The main record source was the Sandia WIPP Central File (SWCF). Early records (about 1975 to 1977) are very limited, however, about details of objectives and plans predating any investigation. Drilling programs from about 1977 were covered by a broadly standardized statement of work, field operations plan, drilling history, and basic data report. Generally standardized procedures for peer, management, and quality assurance review were developed during this time. Agencies such as the USGS conducted projects according to internal standards. Records of detailed actions for individual programs may not be available, though a variety of such records were found in the SWCF. A complete written record cannot be reconstructed. With persistence, a professional geologist can follow individual programs, relate data to objectives (even if implied), and determine how conclusions were used in decision-making. 83 refs

  1. Neutron microtomography-based virtual extraction and analysis of a cercopithecoid partial cranium (STS 1039) embedded in a breccia fragment from sterkfontein member 4 (South Africa).

    Science.gov (United States)

    Beaudet, Amélie; Braga, José; de Beer, Frikkie; Schillinger, Burkhard; Steininger, Christine; Vodopivec, Vladimira; Zanolli, Clément

    2016-04-01

    The Plio-Pleistocene karstic sedimentary deposits of Sterkfontein Cave, South Africa, yielded numerous fossil primate specimens embedded in blocks of indurated breccia, including the partial cercopithecoid cranium labelled STS 1039. Because the surrounding matrix masks most of its morphology, the specimen remains taxonomically undetermined. While the use of X-ray microtomography did not allow extracting any structural information about the specimen, we experimented a new investigative technique based on neutron microtomography. Using this innovative approach, we successfully virtually extracted, reconstructed in 3D and quantitatively assessed the preserved dentognathic structural morphology of STS 1039, including details of its postcanine maxillary dentition. Following comparative analyses with a number of Plio-Pleistocene and extant cercopithecoid taxa, we tentatively propose a taxonomic attribution to the taxon Cercopithecoides williamsi. Our experience highlights the remarkable potential of this novel imaging method to extract diagnostic information and to identify the fossil remains embedded in hard breccia from the South African hominin-bearing cave sites. PMID:26661468

  2. The Halite-Bearing Zag and Monahans (1998) Meteorite Breccias: Shock Metamorphism, Thermal Metamorphism and Aqueous Alteration on the H-Chondrite Parent Body

    Science.gov (United States)

    Rubin, Alan E.; Zolensky, Michael E.; Bodnar, Robert J.

    2002-01-01

    Zag and Monahans (1998) are H-chondrite regolith breccias comprised mainly of lightcolored metamorphosed clasts, dark clasts that exhibit extensive silicate darkening, and a halite-bearing clastic matrix. These meteorites reflect a complex set of modification processes that occurred on the H-chondrite parent body. The light-colored clasts are thermally metamorphosed H5 and H6 rocks that were fragmented and deposited in the regolith. The dark clasts formed from light-colored clasts during shock events that melted and mobilized a significant fraction of their metallic Fe-Ni and troilite grains. The clastic matrices of these meteorites are rich in solar-wind gases. Parent-body water was required to cause leaching of chondri tic minerals and chondrule glass; the fluids became enriched in Na, K, CI, Br, AI, Ca, Mg and Fe. Evaporation of the fluids caused them to become brines as halides and alkalies became supersaturated; grains of halite (and, in the case of Monahans (1998), halite with sylvite inclusions) precipitated at low temperatures (less than or equal to 100 C) in the porous regolith. In both meteorites fluid inclusions were trapped inside the halite crystals. Primary fluid inclusions were trapped in the growing crystals; secondary inclusions formed subsequently from fluid trapped within healed fractures.

  3. Reply to Shaocheng Ji's discussion on `Coesite-bearing eclogite breccia: implication for coseismic ultrahigh-pressure metamorphism and the rate of the process' by Yang et al. (Contrib. Mineral. Petrol., 2014, 167: 1013)

    Science.gov (United States)

    Yang, Jian-Jun; Huang, Meng-Xi; Zhang, Hao-Ran; Yu, Cong

    2015-07-01

    In his discussion, Ji ascribes our results to other workers and, using quotation marks, alleges statements that do not exist in our papers. We interpret some textures in the Yangkou eclogite breccia to be the result of rapid crystallization of local melts, but do not regard the entire breccia or the matrix to be pseudotachylyte. These, combined with the formation of the eclogite breccia from the coronitic eclogite wallrock and the preservation of intergranular coesite, imply transient (coseismic) high-pressure metamorphism. It is clearly indicated that the coesite-bearing eclogites followed a decompression and cooling path from about 3.3 GPa and 700 °C to about 0.3-0.6 GPa and <375-400 °C, at which intergranular coesite and high-pressure microlites quenched. But Ji takes the pressure change to be from 3.3 to 1.2 GPa. The intercrystalline pressure vessel effect advocated by Ji for a compressed material should not be significant in subsequent decompression, particularly when considering the exhumation of intergranular coesite surrounded by fine omphacite grains in a deeply subducted slab.

  4. 云南东川因民角砾岩成因及分类探讨%Discussion on formation cause and classification of Yinmin breccias in Dongchuan, Yunnan

    Institute of Scientific and Technical Information of China (English)

    喻国东

    2012-01-01

    Yinmin breccias discovered in Kunyang Yinmin groups have close relations with Dongchuan copper deposits in mineralization environment and Metallogeny. Many experts gave different awareness attributions in the genesis and sequences aspects in different times, late 1980s, 314 Geological group research team of Yunnan Dongchuan considered that some parts of the breccias belts having the characteristics of volcano-gravel and sediment the breccias could be divided into two categories from the breccias figures, the cement ingredients and the bedding features . The author regards that it is a syngenetic sediments from earlier Kunyang Rift Valley, forming vocano -sediment breccia complex in the graben subsidence environment accompanied with strong undersea volcanc eruption or spraying activities profit on many occasions.%产于滇中昆阳群因民组中的因民角砾岩,因与东川铜矿成矿环境及矿床成因关系密切,不同时期、不同学者先后对因民角砾岩提出了不同认识,对其成因及层位归属进行过讨论.20世纪80年代后期云南东川314队综合组研究后,在因民角砾岩岩带中发现了多个火山—沉积特征,按角砾及胶结物成分、层理特征将因民角砾岩分为两大类,并将其划归因民组一段,重新认识它是昆阳裂谷早期下陷阶段生长断层一地堑盆地环境中伴随强烈海底火山多次喷发、喷溢活动生成的一套火山—沉积角砾杂岩.

  5. Petrography, sulfide mineral chemistry, and sulfur isotope evidence for a hydrothermal imprint on Musina copper deposits, Limpopo Province, South Africa: Evidence for a breccia pipe origin?

    Science.gov (United States)

    Chaumba, Jeff B.; Mundalamo, Humbulani R.; Ogola, Jason S.; Cox, J. A.; Fleisher, C. J.

    2016-08-01

    The Musina copper deposits are located in the Central Zone of the Limpopo orogenic belt in Limpopo Province, South Africa. We carried out a petrographic, sulfide composition, and δ34S study on samples from Artonvilla and Campbell copper deposits and a country rock granitic gneiss to Artonvilla Mine to place some constrains on the origin of these deposits. The assemblages at both Artonvilla and Campbell Mines of brecciated quartz, potassium feldspar, muscovite, chlorite, calcite, and amphibole are consistent with sericitic alteration. Quartz, amphibole, feldspars, and micas often display angular textures which are consistent with breccias. Sulfur concentrations in pyrite from Artonvilla Mine plot in a narrow range, from 50.2 wt. % to 55.7 wt. %. With the exception of a positive correlation between Fe and Cu, no well defined correlations are shown by data from the Musina copper deposits. The occurrence of sulfides both as inclusions in, or as interstitial phases in silicates, suggests that hydrothermal alteration that affected these deposits most likely helped concentrate the mineralization at the Musina copper deposits. Sulfur concentrations in chalcopyrite samples investigated vary widely whereas the copper concentrations in chalcopyrite are not unusually higher compared to those from chalcopyrite from other tectonic settings, probably indicating that either the Cu in the Musina copper deposits occurs in native form, and/or that it is hosted by other phases. This observation lends support to the Cu having been concentrated during a later hydrothermal event. One sample from Artonvilla Mine (AtCal01) yielded pyrite δ34S values of 3.1and 3.6‰ and chalcopyrite from the same sample yielded a value of 3.9‰. A country rock granitic gneiss to Artonvilla Mine yielded a δ34Spyrite value of 8.2‰. For Campbell Mine samples, one quartz vein sample has a δ34Spyrite value of 0.5‰ whereas chalcopyrite samples drilled from different areas within the same sample

  6. Deformation of host rocks and flow of magma during growth of minette dikes and breccia-bearing intrusions near Ship Rock, New Mexico

    Science.gov (United States)

    Delaney, Paul T.; Pollard, David D.

    1981-01-01

    We have studied a small group of minette dikes and plugs that crop out within a flat-lying sequence of siltstone and shale near Ship Rock, a prominent volcanic throat of tuff breccia in northwestern New Mexico. Seven dikes form a radial pattern about Ship Rock we describe in detail the northeastern dike, which has an outcrop length of about 2,900 m, an average thickness of 2.3 m, and a maximum thickness of 7.2 m. The dike is composed of 35 discrete segments arranged in echelon; orientation. of dike segments ranges systematically from N. 52? E. to N. 66? E. A prominent joint set strikes parallel to the segments and is localized within several tens of meters of the dike. Regional joint patterns display no obvious relation to dike orientation. Small offsets of segment contacts, as well as wedge-shaped bodies of crumpled host rock within segments mark the sites of coalescence of smaller segments during dike growth. Bulges in the dike contact, which represent a nondilational component of growth, indicate that wall rocks were brecciated and eroded during the flow of magma. Breccias make up about 9 percent of the 7,176-m 2 area of the dike, are concentrated in its southwest half, and are commonly associated with its thickest parts. We also describe three subcircular plugs; each plug is smaller than 30 m in diameter, is laterally associated with a dike, and contains abundant breccias. Field evidence indicates that these plugs grew from the dikes by brecciation and erosion of wallrocks and that the bulges in the contact of the northeastern dike represent an initial stage of this process. From continuum-mechanical models of host-rock deformation, we conclude that dike propagation was the dominant mechanism for creating conduits for magma ascent where the host rock was brittle and elastic. At a given driving pressure, dikes dilate to accept greater volumes of magma than plugs, and for a given dilation, less work is done on the host rocks. In addition, the pressure required

  7. High Spatial Resolution 40Ar/39Ar Geochronology of Impact Melt Breccias from Apollo 17 Boulders at Stations 2, 6, and 7

    Science.gov (United States)

    Mercer, C. M.; Hodges, K. V.; Jolliff, B. L.; Van Soest, M. C.; Wartho, J. A.; Weirich, J. R.

    2015-12-01

    Several boulders located at the bases of the North and South Massifs were among the primary field targets of the Apollo 17 mission to the Taurus-Littrow Valley on the Moon [1]. Some boulders are polylithologic, including Boulder 1 at Station 2 and the boulders at Stations 6 and 7. These boulders were the subjects of consortium studies [2, 3] that included 40Ar/39Ar geochronology to determine the ages of distinct lithologies within each boulder [e.g., 4-6]. We report new 40Ar/39Ar data for the impact melt breccias 72255, 76315, 77075, and 77135 obtained using the UV laser ablation microprobe (UVLAMP) methods of [7]. For 72255, we obtained a preliminary isochron date ca. 3814 Ma from 22 melt analyses, which is younger than published plateau dates (e.g., 3951-3835 Ma [4, 8]). Fifteen melt analyses of 76315 yield a preliminary isochron date ca. 3850 Ma, younger than the 3900 ± 16 Ma date reported by [8]. Melt analyses of 77075 yield preliminary dates between ca. 3797-3584 Ma, possibly reflecting partial loss of 40Ar. In this case, the oldest date may provide a minimum age for the formation of melt in 77075. Finally, the UVLAMP dates for the 77135 melt range from 3810-3361 Ma and corresponding Ca/K ratios range from ca. 100-6. Electron microprobe analyses of small (ca. 10s of microns wide) pockets of K-rich materials show that both K-rich glass and K-feldspar are present. The UVLAMP dates for 77135 likely reflect spatially variable 40Ar loss, consistent with published step heating results [e.g., 6]. References: [1] Schmitt (1973) Science, 182, 681-690. [2] Ryder (1993). Catalog of Apollo 17 Rocks: Volume 1 - Stations 2 and 3 (South Massif). LPI. [3] Ryder (1993). Catalog of Apollo 17 Rocks: Volume 4 - North Massif. LPI. [4] Leich et al. (1975) The Moon, 14, 407-444. [5] Cadogan & Turner (1976). LPSC, 7, 2267-2285. [6] Stettler et al. (1978). LPSC, 9, 1113-1115. [7] Mercer et al. (2015) Sci. Adv., 1, e1400050. [8] Dalrymple & Ryder (1996). JGR, 101, 26069-26084.

  8. Using the sulfide replacement petrology in lunar breccia 67915 to construct a thermodynamic model of S-bearing fluid in the lunar crust

    Science.gov (United States)

    Bell, Aaron S.; Shearer, Charles; deMoor, J. Maarten; Provencio, Paula

    2015-12-01

    In this work, we investigate the compositions and origin of metasomatic fluids responsible for the formation of sulfide replacement textures in Mg-Suite lithologies of lunar samples 67915-149 and 67915-150. We have constructed a quantitative thermodynamic model of the composition of the metasomatic fluid using fO2, fS2, and temperature constraints derived from a thermodynamic analysis of the metasomatic fluid-mineral reactions and the measured compositions of the phases in the sulfide assemblages. Results from this modeling indicate that the metasomatic fluid responsible for the formation of the sulfide replacement textures was likely dominated by a combination of H2 and CH4, with minor abundances of H2O, CO, and H2S. The modeling indicates that H2S was, by orders of magnitude, the dominant S-species present in the metasomatic fluid and S isotopes in the replacement sulfides suggest that the fluid experienced significant removal of H2S by sulfide precipitation. The calculated H2 and H2O contents of the metasomatic fluid are consistent with those that might be expected for the late stage degassing of shallowly emplaced, intrusive magma bodies. Sulfur, heat, and other volatile constituents (i.e., chalcophile metals and carbon) were sourced from the breccia-producing impactor; the volatile phase produced by the impact event subsequently metasomatized the crust (Haskin and Warren, 1991); The sulfide metasomatism occurred in an ejecta blanket, where both the heat and sulfur that were produced by the impactor re-mobilized volatiles, causing hydrothermal circulation within the crust that redistributed both sulfur and chalcophile elements to produce sulfide-silicate intergrowths (Haskin and Warren, 1991); and Sulfur, heat, and other volatile constituents, sourced from degassing intrusive magmas and sulfur-bearing fluid from the degassing magma, percolated into surrounding crust, metasomatizing the adjacent country rock (Norman et al., 1995). The development of these models

  9. Discussion on "Coesite-bearing eclogite breccia: implication for coseismic ultrahigh-pressure metamorphism and the rate of the process" by Yang et al. (Contrib. Mineral. Petrol., 2014a, 167: 1013)

    Science.gov (United States)

    Ji, Shaocheng

    2015-07-01

    Recently, Yang et al. (Contrib Mineral Petrol 167:1013, 2014a) proposed that "cataclasites," "breccias" and "pseudotachylytes" of eclogites at Yangkou in the Chinese Sulu UHP metamorphic belt are formed by "a compression stress wave of earthquake." They suggested that the intergranular coesite resulted from a rapid cooling from about 700 °C to below 375-400 °C and a "sudden pressure release of seismic wave" from 3.3 to 1.2 GPa in some hours. However, the earthquake-induced UHP metamorphism under fluid-deficient conditions, proposed by these authors, remains inconclusive and inconsistent with the available data from the UHP metamorphic belt. The coesite inclusions within garnet, zircon and omphacite, and intergranular coesite grains between these minerals can be preserved by the presence of the pressure vessel effect, the lack of fluid infiltration, and the presence of a low-temperature and nonhydrostatic deformation environment during rapid exhumation.

  10. Geological Characteristics and Prospecting Direction of Molybdenum Deposit Related to Cryptoexplosion Breccia in Panhe Area of East Qinling%东秦岭潘河钼矿地质特征及找矿方向

    Institute of Scientific and Technical Information of China (English)

    刘满年; 杨登美; 刘新会; 崔龙; 向红林; 王淑娟; 高选顿

    2013-01-01

      东秦岭潘河钼矿床位于东秦岭钼矿带西部,通过野外调查可知,矿床赋存于中元古界宽坪群多旋回沉积—喷发地层中,含矿岩性主要为大理岩、白云质大理岩和绿片岩。钼矿体受控于潘河背斜核部及两翼层间剪切破碎带中,具有多层平行排列的分布规律;钼矿的形成与发展主要受次火山活动与构造控制,是构造和火山活动共同作用和长期演化的结果,与区内广泛出露的隐爆角砾岩有关。研究认为,潘河钼矿的矿床类型为火山期后热液型,成矿时代为燕山晚期;指出应在矿区内多旋回沉积—喷发层间、磁—电异常和隐爆角砾岩层等深部有利部位寻找钼(钨)矿体。%Panhe molybdenum deposit is located in the western part of East Qinling molybdenum ore belt.The molybdenum orebody lies in the middle-proterozoic Kuanping group,a sedimentation-eruption formation generated from polycyclic evolution.The main ore-bearing rock types are marble,dolomitic marble and green schist.Panhe molybdenum deposit exhibits the characteristic of multilayer and parallel shape,which is chiefly controlled by Panhe anticline core and shear fracture stucture in its wings.The formation and development of molybdenum deposit are mainly influenced by subvolcanic activityand tectonic,and have close relationship with cryptoexplosion breccia that intergrowed with subvolcanic rocks.It is the results of the common effect and long-term evolution of the structure and volcanic activity.The Panhe molybdenum deposit belongs to hydrothermal type in late volcanic stage, and its metallogenic epoch is late Yanshanian.The results show that looking for the molybdenum (tungsten) orebody should be in the deep favorable positions which are polycyclic sedimentation-eruption formation,magneticly-electricly abnormaly and cryptoexplosion breccia layers mainly.

  11. Brechas y microbrechas cohesivas en cuarcitas de las sierras de Buenos Aires: Similitudes, diferencias y aproximaciones a su vinculación tectónica Cohesive breccias and microbreccias in quartzites in the Buenos Aires ranges: similitude, differences, and an approximation to their tectonic links

    Directory of Open Access Journals (Sweden)

    Armando C. Massabie

    2008-06-01

    Full Text Available En las Sierras Septentrionales de Buenos Aires se hallan brechas y microbrechas formadas a expensas de las rocas cuarcíticas del Grupo Sierras Bayas. Son rocas de falla identificadas en afloramientos tanto en las cercanías de la localidad homónima como también en los alrededores de Barker, donde se presentan cuarcitas atribuidas a las formaciones sedimentarias precámbricas integrantes del grupo en la localidad. En las Sierras Australes de Buenos Aires se registran rocas de falla similares, desarrolladas sobre las rocas cuarcíticas de varias de las formaciones paleozoicas presentes en esa comarca. En ambas regiones, las zonas de falla con este tipo de roca se observan como bancos subverticales de contactos netos con la caja. En cada localidad, las cuarcitas preservan sus texturas y estructuras originales. En las sierras Bayas el protolito de las brechas guarda las texturas y estructuras sedimentarias en tanto que, en las Sierras Australes, esas texturas han sido obliteradas por deformación penetrativa asociada a metamorfismo en facies de esquistos verdes de modo que el protolito, corresponde a metacuarcitas. La formación de estas rocas de falla, con similitudes en cuanto a su modo de yacer y tipo de texturas cataclásticas en ambas comarcas consideradas, podría ser vinculada a un episodio tectónico extensional de amplio desarrollo en la región, al que se relaciona el origen de las cuencas de Colorado y del Salado durante el Jurásico-Cretácico, que acompañó la apertura del Océano Atlántico.Quartzitic sandstones of the sierras Bayas Group in Sierras Septentrionales of Buenos Aires are studied. Outcrops of these deformed rocks are observed at sierras Bayas and Barker localities, where quartzitic sandstones from Precambrian units are present. These rocks are compared with similar fault breccias in Sierras Australes of Buenos Aires, which were develop in quartzitic rocks of several Paleozoic units of this region. At both regions

  12. Alberto Breccia. La pulsión de un ideario

    OpenAIRE

    FELLINGER, CHRISTIAN MATIAS

    2012-01-01

    Dentro de la historia del arte, el cómic, tiene un lugar excesivamente pobre, no solo por su juventud (posee un poco más de cien años desde su creación), sino por la marginalidad en que lo han catalogado y lo ubicaron la mayoría de los entendidos en el arte. Si bien en los últimos tiempos, el cómic, ha obtenido algún reconocimiento mayor, su valoración sigue siendo mala, por debajo de su presunto valor artístico, plástico y técnico. Seguramente su masividad y falta de calidad en la impresión ...

  13. Characteristics of mix crystal xenolith from basaltic(shoshonitic) volcanic breccia at Maguan Area, Yunnan Province, and their geological significance%云南马关碧(钾)玄质火山角砾岩中矿物混晶包体特征及其地质意义

    Institute of Scientific and Technical Information of China (English)

    黄玉蓬; 刘显凡; 李春辉; 卢秋霞; 陶专; 赵甫峰; 董毅; 邹金汐; 易立文

    2013-01-01

    在云南马关碧(钾)玄质火山角砾岩中发现了一类特殊包体,呈红色与黑色两种.经X射线粉晶衍射鉴定,红色者为以锰铝榴石为主要结晶相的隐晶-非晶质混晶,黑色者为以绿辉石为主要结晶相的隐晶-非晶质混晶.两种矿物混晶包体在一定程度上类似于熔浆玻璃或熔体囊,它们具有同源演化的相似地球化学特征.文中通过对两种矿物混晶包体的显微特征与地球化学分析研究表明,它们是亏损地幔部分熔融的产物,并作为一种不混溶熔体成分被碱性玄武岩浆携带、运移上升.它们代表了石榴石相(榴辉岩相)地幔源区组分,暗示新生代时期软流圈上涌除释放小体积交代熔体交代上地幔使其富集之外,还造成岩石圈地幔拆沉,尖晶石相地幔组分向石榴石相地幔组分转变.另外,据两种混晶包体与其他类型包体和寄主岩岩浆的不同来源,推测马关地区深部岩石圈地幔经交代作用发生过两次转换.首先是由原始地幔向亏损地幔转化,并发生部分熔融,其后是由亏损地幔转化为富集地幔,形成富碱岩浆和与其互不混溶的进一步富集成矿元素的地幔流体.由此暗示滇西地区与富碱斑岩有关的多金属成矿作用即受制于这一深部地质过程与壳幔混染机制.%A special kind of xenolith has been discovered from the basaltic (shoshonitic) volcanic breccia at Maguan area. Yunnan Province. There are two kinds of xenoliths: one is red and the other is black in color. It can be identified by X-ray crystal powder diffraction that the red one is a mixed crystal of aphanites-amorphous material, the major potential component of which is spessartine. while the black one is a mixed crystal of aphanites-amorphous material, major potential component of which is omphacite. To some extent the two kind of mixed crystals are similar to melting glass or melt pockets. It shows that they have the similar geochemical

  14. Preserved Flora and Organics in Impact Melt Breccias: Implications for Capturing Past Life on Mars

    Science.gov (United States)

    Schultz, P. H.; Harris, R. S.; Clemett, S.; Thomas-Keprta, K.

    2013-12-01

    At least seven impact glass-bearing deposits have been documented in the Argentine stratigraphy, each recording separate events between the Holocene and late Miocene [1,2]. Detailed evidence for their origin by impact includes: planar deformation features (PDFs in quartz, feldspars, pyroxene, olivine, etc.), asymmetric isotropization (i.e., alternate-twin deformation) in plagioclase, diaplectic phases, ultra-high temperature melting (e.g., lechatelierite, molten rutile) and decomposition (e.g., baddeleyite), and quench textures around minerals, e.g., beta-crystobalite, etc. [1-3]. Incorporation of materials from depth indicates that this was not an airburst but a series of crater-forming impacts. Many hand samples also contain relicts of extant biota. Scanning electron microprobe (SEM) images reveal preservation of delicate forms including: striated layers between vesicular impact glass and parallel vein-like features at higher magnification. The striated patterns resemble vascular bundles of the mesophyll (ground tissue) of a plant. Identifiable parts of the plant anatomy, e.g. papillae and cell walls, contain skeletal magnetite crystals and high-temperature, i.e., phases indicating that vitreous fossilization occurred at extremely high temperatures and rapid quench rates. The morphology is generally similar to contemporary regional grasses (pampas grass) including small spherules (papilla). The intricate forms (20nm to 20mm) indicate features rapidly preserved rather than simple impressions. Reaction zones (vesiculation and quenched minerals) along the interface between the melt and entrained plants indicate rapid quenching. Compositional mapping reveals the presence of insignificant levels of carbon, but chemical analyses confirm the high silica content (> 60%). Various analytical techniques (micro-Raman, TEM/SEM, and μltra-L2MS) further reveal the preserved organic materials, including tetracyclic pyrrolines, essential members of the group of porphyrin species that are produced through the thermal degradation of chlorophyll with heterogeneous survival of abundant C and N. The survival and preservations of organics within hydrous pockets in rapidly quenched impact glasses may provide a new strategy for identifying biomarkers of possible early life on ancient Mars. Impact melt could encapsulate and preserve this record. It is likely that the porous nature of the target (loess), which characterizes much of the Martian surface, would ensure flash-heat preservation under highly reducing conditions [4]. [1] Schultz, P. H. et al. (2004), EPSL, v. 219, 221-238; [2] Schultz et al. (2006), Schultz, P. H. et al. (2006), MAPS, v. 41, 749-771; [3] Harris, R. S. and Schultz, P. H. (2007), GSA abstracts 39, 371 [4] Harris, R. S., and Schultz, P. H. (2007), LPSC 38, no. 2306.

  15. (U-Th)/He dating and He diffusion in calcite from veins and breccia

    Science.gov (United States)

    Gautheron, C.; Cros, A.; Pagel, M.; Berthet, P.; Tassan-Got, L.; Douville, E.; Pinna-Jamme, R.; Sarda, P.

    2013-12-01

    Knowledge of He retention in crystalline calcite is mandatory to estimate the possibility of (U-Th)/He dating of calcite. To this aim, fault-filling calcite crystals from the Eocene/Oligocene Gondrecourt graben, Paris Basin, Eastern France, have been sampled, based on their relatively old, Eocene-Oligocene, precipitation age and cold thermal history (agreement with the He-retentive character of calcite as determined by Copeland et al. (2007), and these ages were obtained for the most recently precipitated crystals. To better understand the large He-age scatter and why calcites precipitated earlier show younger ages, He diffusion experiments have been conducted on 10 Gondrecourt calcite fragments from 3 samples with He ages of 0.2 to 6 Ma. In addition, a crystallographic investigation by X-Ray Diffraction (XRD) performed on similar samples reveals that the crystal structure evolves with increasing temperature, showing with micro-cracks and cleavage opening. These XRD results indicate that, in fault-filling calcite, He retention is controlled by multiple diffusion domains (MDD, Lovera et al., 1991) with various sizes, and therefore, evolves through time with strong consequences on (U-Th)/He age. We thus interpret the Gondrecourt calcite (U-Th)/He age scatter of older samples as a consequence of cleavage opening due to a succession of calcite crystallization phases related to the deformation history. Finally, we propose that the crystallization age of a calcite crystal with a known thermal history can nevertheless be retrieved by the (U-Th)/He method provided the He diffusion pattern can be measured by careful step-heating degassing analysis. Copeland, P., Watson, E.B., Urizar, S.C., Patterson, D., Lapen, T.J., 2007. Alpha thermochronology of carbonates. Geochim. Cosmochim. Acta, 71: 4488-4511. Cros, A. Gautheron, C., Pagel, M., Berthet, P., Tassan-Got, L., Douville, E., Pinna-Jamme, R., Sarda, P., submitted GCA, He behavior in calcite filling viewed by (U-Th)/He dating, He diffusion and crystallographic studies. Lovera, O.M., Richter, F.M., Harrison, T.M., 1991. Diffusion domains determined by 39Ar released during step heating. Journal of Geophysical Research, 96: 2057-2069.

  16. Impact Amber, Popcorn, and Pathology: The Biology of Impact Melt Breccias and Implications for Astrobiology

    Science.gov (United States)

    Harris, R. S.; Schultz, P. H.

    2007-03-01

    We present evidence that superheated impact melts can trap and preserve both floral and faunal remains forming "impact amber." We discuss terrestrial occurrences of impact amber and the strategy it suggests in searching for evidence of past life on other

  17. Hydrological, Geological, and Biological Site Characterization of Breccia Pipe Uranium Deposits in Northern Arizona

    Science.gov (United States)

    2010-01-01

    On July 21, 2009, U.S. Secretary of the Interior Ken Salazar proposed a two-year withdrawal of about 1 million acres of Federal land near the Grand Canyon from future mineral entry. These lands are contained in three parcels: two parcels on U.S. Bureau of Land Management land to the north of the Grand Canyon (North and East Segregation Areas) and one on the Kaibab National Forest south of the Grand Canyon (South Segregation Area). The purpose of the two-year withdrawal is to examine the potential effects of restricting these areas from new mine development for the next 20 years. This proposed withdrawal initiated a period of study during which the effects of the withdrawal must be evaluated. At the direction of the Secretary, the U.S. Geological Survey began a series of short-term studies designed to develop additional information about the possible effects of uranium mining on the natural resources of the region. Dissolved uranium and other major, minor, and trace elements occur naturally in groundwater as the result of precipitation infiltrating from the surface to water-bearing zones and, presumably, to underlying regional aquifers. Discharges from these aquifers occur as seeps and springs throughout the region and provide valuable habitat and water sources for plants and animals. Uranium mining within the watershed may increase the amount of radioactive materials and heavy metals in the surface water and groundwater flowing into Grand Canyon National Park and the Colorado River, and deep mining activities may increase mobilization of uranium through the rock strata into the aquifers. In addition, waste rock and ore from mined areas may be transported away from the mines by wind and runoff.

  18. Martian Noble Gases in Recently Found Shergottites, Nakhlites, and Breccia Northwest Africa 8114

    Science.gov (United States)

    Busemann, H.; Seiler, S.; Wieler, R.; Kuga, M.; Maden, C.; Irving, A. J.; Clay, P. L.; Joy, K. H.

    2015-07-01

    New noble gas data for several recently found martian meteorites will be presented to determine cosmic-ray exposure ages and source pairing. The presence of trapped (atmospheric) components and discrepancies to earlier data sets will be discussed.

  19. Spade: An H Chondrite Impact-melt Breccia that Experienced Post-shock Annealing

    Science.gov (United States)

    Rubin, Alan E.; Jones, Rhian H.

    2006-01-01

    The low modal abundances of relict chondrules (1.8 Vol%) and of coarse (i.e. >= 2200 micron-size) isolated mafic silicate grains (1.8 Vol%) in Spade relative to mean H6 chondrites (11.4 and 9.8 vol%, respectively) show Spade to be a rock that has experienced a significant degree of melting. Various petrographic features (e.g., chromite-plagioclase assemblages, chromite veinlets, silicate darkening) indicate that melting was caused by shock. Plagioclase was melted during the shock event and flowed so that it partially to completely surrounded nearby mafic silicate grains. During crystallization, plagioclase developed igneous zoning. Low-Ca pyroxene that crystallized from the melt (or equilibrated with the melt at high temperatures) acquired relatively high amounts of CaO. Metallic Fe-Ni cooled rapidly below the Fe-Ni solws and transformed into martensite. Subsequent reheating of the rock caused transformation of martensite into abundant duplex plessite. Ambiguities exist in the shock stage assignment of Spade. The extensive silicate darkening, the occurrence of chromite-plagioclase assemblages, and the impact-melted characteristics of Spade are consistent with shock stage S6. Low shock (stage S2) is indicated by the undulose extinction and lack of planar fractures in olivine. This suggests that Spade reached a maximum prior shock level equivalent to stage S6 and then experienced post-shock annealing (probably to stage Sl). These events were followed by a less intense impact that produced the undulose extinction in the olivine, characteristic of shock stage S2. Annealing could have occurred if Spade were emplaced near impact melts beneath the crater floor or deposited in close proximity to hot debris within an ejecta blanket. Spade firmly establishes the case for post-shock annealing. This may have been a common process on ordinary chondrites (OC) asteroids.

  20. Rb-Sr Isotopic Systematics of Alkali-Rich Fragments in the Yamato-74442 LL-Chondritic Breccia

    Science.gov (United States)

    Yokoyama, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simo, J. I.; Tappa, M. J.; Yoneda, S.

    2012-01-01

    Alkali-rich igneous fragments were identified in the brecciated LL-chondrites, Kr henberg (LL5)], Bhola (LL3-6) and Yamato (Y)-74442 (LL4), and show characteristic fractionation patterns of alkaline elements. The K-Rb-Cs-rich fragments in Kr henberg, Bhola, and Y-74442 are very similar in mineralogy and petrography (olivine + pyroxene + glass), suggesting that they could have come from related precursor materials. We have undertaken Rb-Sr isotopic studies on alkali-rich fragments in Y-74442 to precisely determine their crystallization ages and the isotopic signatures of their precursor material(s).

  1. Reanalysis of the Benesov bolide and recovery of polymict breccia meteorites - old mystery solved after 20 years

    Czech Academy of Sciences Publication Activity Database

    Spurný, Pavel; Haloda, J.; Borovička, Jiří; Shrbený, Lukáš; Halodová, P.

    2014-01-01

    Roč. 570, October (2014), A39/1-A39/14. ISSN 0004-6361 R&D Projects: GA ČR GA205/08/0411; GA ČR(CZ) GAP209/11/1382 Grant ostatní: EU(XE) MRTN-CT-2006-035519 Institutional support: RVO:67985815 Keywords : meteorites * meteors * meteoroids Subject RIV: BN - Astronomy , Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  2. Intensive Behavioral Intervention for School-Aged Children with Autism: Una Breccia nel Muro (UBM)--A Comprehensive Behavioral Model

    Science.gov (United States)

    Fava, Leonardo; Vicari, Stefano; Valeri, Giovanni; D'Elia, Lidia; Arima, Serena; Strauss, Kristin

    2012-01-01

    Although, reviews and outcome research supports empirical evidence for Early Intensive Behavior Intervention in pre-scholars, intensive behavioral service provision for school-aged children with autism spectrum disorders (ASD) are less subject to research studies. In order to provide effective behavioral interventions for school-aged children it…

  3. Mineralogy of iron sulfides in CM1 and CI1 lithologies of the Kaidun breccia: Records of extreme to intense hydrothermal alteration

    Science.gov (United States)

    Harries, Dennis; Zolensky, Michael E.

    2016-05-01

    The polymict Kaidun microbreccia contains lithologies of C-type chondrites with euhedral iron sulfide crystals of hydrothermal origin. Our FIB-TEM study reveals that acicular sulfides in a CM1 lithology are composed of Fe-rich pyrrhotite with nonintegral vacancy superstructures (NC-pyrrhotite), troilite, and pentlandite, all showing distinct exsolution textures. Based on phase relations in the Fe-Ni-S system, we constrain the temperature of formation of the originally homogeneous monosulfide solid solution to the range of 100-300 °C. In some crystals the exsolution of pentlandite and the microtextural equilibration was incomplete, probably due to rapid cooling. We use thermodynamic modeling to constrain the physicochemical conditions of the extreme hydrothermal alteration in this lithology. Unless the CM1 lithology was sourced from a large depth in the parent body (internal pressure >85 bar) or the temperatures were in the lower range of the interval determined, the water was likely present as vapor. Previously described light δ34S compositions of sulfides in Kaidun's CM1 lithology are likely due to the loss of 34S-enriched H2S during boiling. Platy sulfide crystals in an adjacent, intensely altered CI1 lithology are composed of Fe-poor, monoclinic 4C-pyrrhotite and NC-pyrrhotite and probably formed at lower temperatures and higher fS2 relative to the CM1 lithology. However, a better understanding of the stability of Fe-poor pyrrhotites at temperatures below 300 °C is required to better constrain these conditions.

  4. Evidence for Localized High Temperature Hydrothermal Fluid Flow within the Sub-Crater Environment of the Rochechouart Impact Structure: Observations from a Polymict Breccia Dike

    OpenAIRE

    Simpson, S.L.; Lambert, P; Lee, M R

    2015-01-01

    Hypervelocity impacts into volatilebearing terrestrial targets can initiate hydrothermal circulation for a finite period of time; evidence for this is preserved in approximately one-third of impact structures on Earth [1, 2]. Hydrothermal environments can host extremophile life, and microbial communities have been found to colonize impact craters [3, 4]. The majority of impact structures on Earth have yet to be studied in great detail; many aspects of the post-impact environment such as the e...

  5. Argon-40/Argon-39 Age Spectra of Apollo 17 Highlands Breccia Samples by Laser Step Heating and the Age of the Serenitatis Basin

    Science.gov (United States)

    Dalrymple, G. Brent; Ryder, Graham

    1996-01-01

    We have obtained high-resolution (21-63 steps) Ar-40/Ar-39 age spectra using a continuous laser system on 19 submilligram samples of melt rocks and clasts from Apollo 17 samples collected from the pre-Imbrian highlands in the easternmost part of the Serenitatis basin. The samples include poikilitic melt rocks inferred to have been formed in the Serenitatis basin-forming impact, aphanitic melt rock whose compositions vary and whose provenance is uncertain, and granulite, gabbro, and melt clasts. Three of the poikilitic melts have similar age spectrum plateau ages (72395,96, 3893 +/- 16 Ma (2sigma); 72535,7, 3887 +/- 16 Ma; 76315,150, 3900 +/- 16 Ma) with a weighted mean age of 3893 +/- 9 Ma, which we interpret as the best age for the Serenitatis basin- forming impact. Published Ar-40/Ar-39 age spectrum ages of Apollo 17 poikilitic melts are consistent with our new age but are much less precise. Two poikilitic melts did not give plateaus and the maxima in their age spectra indicate ages of greater than or equal to 3869 Ma (72558,7) and greater than or equal to 3743 Ma (77135,178). Plateau ages of two poikilitic melts and two gabbro clasts from 73155 range from 3854 +/- 16 Ma to 3937 +/- 16 Ma and have probably been affected by the ubiquitous (older?) clasts and by post- formation heating (impact) events. Plateau ages from two of the aphanitic melt 'blobs' and two granulites in sample 72255 fall in the narrow range of 3850 q 16 Ma to 3869 q 16 Ma with a weighted mean of 3862 +/- 8 Ma. Two of the aphanitic melt blobs from 72255 have ages of 3883 +/- 16 Ma and greater than or equal to 3894 Ma, whereas a poikilitic melt clast (of different composition from the 'Serenitatis' melts) has an age of 3835 +/- 16 Ma, which is the upper limit for the accretion of 72255. These data suggest that either the aphanitic melts vary in age, as is also suggested by their varying chemical compositions, or they formed in the 72255 accretionary event about 3.84-3.85 Ga and older relict material is responsible for the dispersion of ages. In any case the aphanitic melts do not appear to be Serenitatis products. Our age for the Serenitatis impact shows, on the basis of the isotopic age evidence alone, that Serenitatis is greater than 20-25 Ma and probably greatr than 55-60 Ma older than Imbrium (less than or equal to 3870 Ma and probably less than or equal to 3836 Ma (Dalrymple and Ryder, 19931). Noritic granulite sample 78527 has a plateau age of 4146 +/- 17 Ma, representing a minimum age for cooling of this sample in the early lunar crust. So far there is no convincing evidence in the lunar melt rock record for basin-forming impacts significantly older than 3.9 Ga.

  6. Hydrocarbon-derived ferromanganese nodules in carbonate-mud mounds from the Gulf of Cadiz: Mud-breccia sediments and clasts as nucleation sites

    OpenAIRE

    Torres Pérez-Hidalgo, Trinidad José de

    2009-01-01

    More than 500 F e - M n nodules were sampled during the Anastasya-01 cruise (TASYO project) along the continental margin of the Gulf of Cadiz (eastern Central Atlantic), at the confluence of the Mediterranean Sea with the Atlantic Ocean, where extensive nodule fields were discovered. Based o n wide previous studies that included swath bathymetry, multi-channel and very high-resolution seismic reflection, gravimetry, magnetism and underwater photography surveys, nodules were collec...

  7. 40Ar/39Ar age of the Rotoiti Breccia and Rotoehu Ash, Okataina Volcanic Complex, New Zealand, and identification of heterogeneously distributed excess 40Ar in supercooled crystals

    DEFF Research Database (Denmark)

    Flude, Stephanie; Storey, Michael

    2016-01-01

    Co-magmatic granitoid clasts erupted as part of the Rotoiti Ignimbrite (Rotoehu Tephra) contain euhedral K-feldspar and biotite crystals that protrude into miarolytic cavities and show textural evidence for growth in super-cooled conditions and are thus interpreted as growing during eruption. 40Ar....../39Ar stepped heating experiments on single K-feldspar crystals reveal the presence of heterogeneously distributed excess 40Ar, preferentially released at lower temperature steps (most likely from fluid/melt inclusions), which cannot reliably be characterised by, or corrected for using isotope...... correlation diagrams due to mixing between three reservoirs of 40Ar (radiogenic, atmospheric and excess). This excess 40Ar component is common, but not ubiquitous, and an age population unmixing algorithm applied to single-crystal fusion data identifies a younger group of K-feldspar and biotite crystals that...

  8. Holocene geology of central Africa

    OpenAIRE

    Thiéblemont, Denis

    2008-01-01

    N° Outcrop: Belinga-Palace. View of a typical "lateritic profile" including a lateritic breccia (Stone Line) and the overlying Cover Horizon. The breccia is composed of ferricrust blocks of varied size.

  9. Geochemistry and petrography of the MacAlpine Hills lunar meteorites

    Science.gov (United States)

    Lindstrom, Marilyn M.; Mckay, David S.; Wentworth, Susan J.; Martinez, Rene R.; Mittlefehldt, David W.; Wang, Ming-Sheng; Lipschutz, Michael E.

    1991-01-01

    MacAlpine Hills 88104 and 88105, anorthositic lunar meteorites recovered form the same area in Antartica, are characterized. Petrographic studies show that MAC88104/5 is a polymict breccia dominated by impact melt clasts. It is better classified as a fragmental breccia than a regolith breccia. The bulk composition is ferroan and highly aluminous (Al2O3-28 percent).

  10. UNAM Scientific Drilling Program of Chicxulub Impact Structure-Evidence for a 300 kilometer crater diameter

    Science.gov (United States)

    Urrutia-Fucugauchi, J.; Marin, L.; Trejo-Garcia, A.

    As part of the UNAM drilling program at the Chicxulub structure, two 700 m deep continuously cored boreholes were completed between April and July, 1995. The Peto UNAM-6 and Tekax UNAM-7 drilling sites are ˜150 km and 125 km, respectively, SSE of Chicxulub Puerto, near the crater's center. Core samples from both sites show a sequence of post-crater carbonates on top of a thick impact breccia pile covering the disturbed Mesozoic platform rocks. At UNAM-7, two impact breccia units were encountered: (1) an upper breccia, mean magnetic susceptibility is high (˜55 × 10-6 SI units), indicating a large component of silicate basement has been incorporated into this breccia, and (2) an evaporite-rich, low susceptibility impact breccia similar in character to the evaporite-rich breccias observed at the PEMEX drill sites further out. The upper breccia was encountered at ˜226 m below the surface and is ˜125 m thick; the lower breccia is immediately subjacent and is >240 m thick. This two-breccia sequence is typical of the suevite-Bunte breccia sequence found within other well preserved impact craters. The suevitic upper unit is not present at UNAM-6. Instead, a >240 m thick evaporite-rich breccia unit, similar to the lower breccia at UNAM-7, was encountered at a depth of ˜280 m. The absence of an upper breccia equivalent at UNAM-6 suggests some portion of the breccia sequence has been removed by erosion. This is consistent with interpretations that place the high-standing crater rim at 130-150 km from the center. Consequently, the stratigraphic observations and magnetic susceptibiity records on the upper and lower breccias (depth and thickness) support a ˜300 km diameter crater model.

  11. The Role of Palaeogene Clastics in the Tectonic Interpretation of Northern Dalmatia (Southern Croatia)

    OpenAIRE

    Tari, V.; Mrinjek, E.

    1994-01-01

    The Palaeogene coarse-grained clastics of Northern Dalmatia (Jelar breccia, Promina deposits and Flysch) are syntectonic deposits related to the structural evolution of the Dinaride Thrust Belt. The Jelar breccia is a proximal sedimentary unit deposited in response to early compression of the carbonate platform (Lutetian to Bartonian). Flysch deposits are considered as their distal equivalents. The Early Jelar breccia displays a blended clast composition related to the simultaneous erosion of...

  12. Production of Synthetic Lunar Simulants Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Zybek Advanced Products has proven the ability to produce industrial quantities of lunar simulant materials, including glass, agglutinate and melt breccias. These...

  13. Internal structure, fault rocks, and inferences regarding deformation, fluid flow, and mineralization in the seismogenic Stillwater normal fault, Dixie Valley, Nevada

    Science.gov (United States)

    Caine, J.S.; Bruhn, R.L.; Forster, C.B.

    2010-01-01

    Outcrop mapping and fault-rock characterization of the Stillwater normal fault zone in Dixie Valley, Nevada are used to document and interpret ancient hydrothermal fluid flow and its possible relationship to seismic deformation. The fault zone is composed of distinct structural and hydrogeological components. Previous work on the fault rocks is extended to the map scale where a distinctive fault core shows a spectrum of different fault-related breccias. These include predominantly clast-supported breccias with angular clasts that are cut by zones containing breccias with rounded clasts that are also clast supported. These are further cut by breccias that are predominantly matrix supported with angular and rounded clasts. The fault-core breccias are surrounded by a heterogeneously fractured damage zone. Breccias are bounded between major, silicified slip surfaces, forming large pod-like structures, systematically oriented with long axes parallel to slip. Matrix-supported breccias have multiply brecciated, angular and rounded clasts revealing episodic deformation and fluid flow. These breccias have a quartz-rich matrix with microcrystalline anhedral, equant, and pervasively conformable mosaic texture. The breccia pods are interpreted to have formed by decompression boiling and rapid precipitation of hydrothermal fluids whose flow was induced by coseismic, hybrid dilatant-shear deformation and hydraulic connection to a geothermal reservoir. The addition of hydrothermal silica cement localized in the core at the map scale causes fault-zone widening, local sealing, and mechanical heterogeneities that impact the evolution of the fault zone throughout the seismic cycle. ?? 2010.

  14. Crypto-explosion process and volcanic rock type uranium mineralizations in northwestern Fujian Province

    International Nuclear Information System (INIS)

    It has been proved by practice that crypto-explosive breccia rock body plays an important role in the volcanic rock type uranium mineralization. The author expounds the formative time and space conditions of the cryto-explosive breccia in northwestern Fujian Province, its relation with the country rocks, zonate and key identification factors. Examples are used to demonstrate the 3 major control styles of crypto-explosive breccia on uranium mineralization. The methods of locating crypto-explosive breccia rock body are also discussed

  15. 豫西祁雨沟金矿床成矿流体岩浆来源的流体包裹体和稳定同位素证据

    Institute of Scientific and Technical Information of China (English)

    范宏瑞; 胡芳芳; 杨奎锋; 金成伟

    2009-01-01

    Gold ores of the Qiyugou deposit in the eastern part of the Xiong' ershan region are hosted in breccia pipes within a Mesozoic granitic porphyry. Three stages of alteration-hydrothermal activity are recognized within the Qiyugou breccias. The first stage of hydrothermal metasomatism produced extensive Kfeldspar alteration, The second stage is associated with deposition of gold and base metal sulfide minerals.

  16. Holocene geology of central Africa

    OpenAIRE

    Thiéblemont, Denis

    2008-01-01

    N° Outcrop: Belinga-Palace. View of a typical "lateritic profile" including a lateritic breccia (Stone Line) and the overlying Cover Horizon. The breccia is composed of ferricrust blocks of varied size. Note the sharp contact between Stone Line and Cover Horizon and the occurrence of a coarse layer with an irregular surface at the top of the Stone Line.

  17. Basaltic Clasts in Y-86032 Feldspathic Lunar Meteorite: Ancient Volcanism far from the Procellarum Kreep Terrane

    Science.gov (United States)

    Yamaguchi, A.; Takeda, H.; Nyquist, L. E.; Bogard, D.; Karouji, Y.; Ebihara, M.

    2008-01-01

    Lunar meteorite, Y-86032 is a fragmental or regolith breccia enriched in Al2O3 (28-31 wt%) and having very low concentrations of REEs and Th, U [e.g., 1]. Nyquist et al. [2] suggested that Y- 86032 contains a variety of lithologies not represented by the Apollo samples. They found clasts with old Ar-Ar ages and an ancient Sm-Nd age, and negative Nd indicating a direct link to the primordial magma ocean. Importantly, the final lithification of the Y-86032 breccia was likely >3.8-4.1 Ga ago. Therefore, any lithic components in the breccia formed prior to 3.8 Ga, and lithic components in breccia clasts in the parent breccia formed even earlier. Here we report textures and mineralogy of basaltic and gabbroic clasts in Y- 86032 to better understand the nature of ancient lunar volcanism far from the Procellarum KREEP Terrain (PKT) [3] and the central nearside.

  18. The relationships between geology and soil chemistry at the Apollo 17 landing site

    Science.gov (United States)

    Rhodes, J. M.; Rodgers, K. V.; Bansal, B. M.; Wiesmann, H.; Shih, C.; Nyquist, L. E.; Hubbard, N. J.

    1974-01-01

    Within the wide compositional range of the Apollo 17 soils, three distinct chemical groups have been recognized, each one corresponding broadly with a major geological and physiographic unit. These groups are: (1) Valley Floor type soils, (2) South Massif type soils, and (3) North Massif type soils. The observed chemical variations within and between these three groups is interpreted by means of mixing models in terms of lateral transport and mixing of prevailing local rock types, such as high-titanium basalts, KREEP-like noritic breccias, anorthositic gabbro breccias and orange glass. According to these models, North Nassif types evolved on the lower slopes of the North Massif and Sculptured Hills where anorthositic gabbro predominates over noritic breccia and where lateral mixing with basalt is effective, whereas the South Massif type soils originally developed on the upper slopes of the South Massif, where anorthositic breccia and noritic breccias are equally abundant, and where lateral mixing with basalt was minimal.

  19. Some petrological aspects of Imbrium stratigraphy

    Science.gov (United States)

    Ridley, W. I.

    1977-01-01

    Descriptions are given of the petrochemistry of two Apennine Front breccias, both ejected to the surface during excavation of Spur Crater. The first clast type is breccia number 15445, a spinel pyroxenite whose mineralogy and petrochemistry are consistent with the original rock type being a garnet pyroxenite. The second rock, breccia 15459, is plutonic norite, in which coarsely exsolved inverted pigeonite is associated with anorthitic plagioclase. Application of mineral geothermometers indicates crystallization of these rocks below 1100 C; hence their textures probably developed largely by solid state recrystallization during impact-metamorphism.

  20. Geochemical Comparison of Four Cores from the Manson Impact Structure

    Science.gov (United States)

    Korotev, Randy L.; Rockow, Kaylynn M.; Jolliff, Bradley L.; Haskin, Larry A.; McCarville, Peter; Crossey, Laura J.

    1996-01-01

    Concentrations of 33 elements were determined in relatively unaltered, matrix-rich samples of impact breccia at approximately 3-m-depth intervals in the M-1 core from the Manson impact structure, Iowa. In addition, 46 matrix-rich samples from visibly altered regions of the M-7, M-8, and M-10 cores were studied, along with 42 small clasts from all four cores. Major element compositions were determined for a subset of impact breccias from the M-1 core, including matrix-rich impact-melt breccia. Major- and trace-element compositions were also determined for a suite of likely target rocks. In the M-1 core, different breccia units identified from lithologic examination of cores are compositionally distinct. There is a sharp compositional discontinuity at the boundary between the Keweenawan-shale-clast breccia and the underlying unit of impact-melt breccia (IMB) for most elements, suggesting minimal physical mixing between the two units during emplacement. Samples from the 40-m-thick IMB (M-1) are all similar to each other in composition, although there are slight increases in concentration with depth for those elements that have high concentrations in the underlying fragmental-matrix suevite breccia (SB) (e.g., Na, Ca, Fe, Sc), presumably as a result of greater clast proportions at the bottom margin of the unit of impact-melt breccia. The high degree of compositional similarity we observe in the impact-melt breccias supports the interpretation that the matrix of this unit represents impact melt. That our analyses show such compositional similarity results in part from our technique for sampling these breccias: for each sample we analyzed a few small fragments (total mass: approximately 200 mg) selected to be relatively free of large clasts and visible signs of alteration instead of subsamples of powders prepared from a large mass of breccia. The mean composition of the matrix-rich part of impact-melt breccia from the M-1 core can be modeled as a mixture of approximately

  1. Graphite-magnetite aggregates in ordinary chondritic meteorites

    Science.gov (United States)

    Scott, E. R. D.; Taylor, G. J.; Rubin, A. E.; Keil, K.; Okada, A.

    1981-01-01

    The graphite-magnetite component has been found (1) as abundant isolated inclusions in eight ordinary-chondritic, regolith breccias; (2) as the sole matrix in a new kind of unequilibrated chondrite that forms clasts in these regolith breccias; and (3) together with a Huss matrix in six unequilibrated ordinary chondrites. It is suggested that the component was formed by low-temperature, gas-solid reactions before the accretion of the meteorite, and that the isolated inclusions of graphite-magnetite in regolith breccias were derived from bodies composed of the new kind of chondrite that has graphite-magnetite as its sole matrix.

  2. Petrology and geochemistry of the NWA 3368 Eucrite

    OpenAIRE

    Gardner, K.G.; Lauretta, D. S.; Hill, D. H.; Goreva, J. S.; Domanik, K.J.; Franchi, I. A.; Drake, M.J.

    2006-01-01

    We report the petrology and geochemistry of NWA 3368, a new non-cumulate, monomict eucrite breccia with a variety of clast sizes and a pink-tinted matrix. Analytical techniques include electron microprobe, INAA, and ICP-MS.

  3. Apollo 16 - Impact melt sheets, contrasting nature of the Cayley plains and Descartes mountains, and geologic history

    Science.gov (United States)

    Mckinley, J. P.; Taylor, G. J.; Keil, K.; Ma, M.-S.; Schmitt, R. A.

    1984-01-01

    Apollo 16 stations four and five rake samples have been examined petrographically and by electron microprobe and INAA. Lithologic abundances support the idea (Korontev, 1981) that the variation of soil composition at Apollo 16 results from mixing between a component represented by station five and components much like either the dimict breccias or feldspathic fragmental breccias in composition. Pyroxene, olivine, and coexisting plagioclase compositions from within the anorthosite portions of dimict breccias bridge the gap between the Mg-rich and ferroan anorthosite fields. Analyses from associated cumulate and granulitic clasts indicate that they are the source of the intermediate material. Dimict breccias formed about 3.92 b.y. ago, the nectaris event occurred 3.84-3.92 b.y. ago, and the Cayley plains were deposited as a result of the Imbrium event sometime later than 3.84 b.y.

  4. Black Beauty's Rainbow: Hyperspectral Imaging of Northwest Africa 7034

    Science.gov (United States)

    Cannon, K. M.; Mustard, J. F.; Agee, C. B.; Wilson, J. H.; Greenberger, R. N.

    2014-07-01

    Hyperspectral imaging is used to characterize the first basaltic breccia from Mars, Northwest Africa 7034. Initial results show the spectral character of NWA 7034 is unlike other SNC meteorites and may be more representative of average martian crust.

  5. Inert gases in twelve particles and one 'dust' specimen from the Lunar-16 sample

    Science.gov (United States)

    Heymann, D.; Yaniv, A.; Lakatos, S.

    1974-01-01

    Mass spectrography was used to measure inert gases in lunar breccia and basalt particles. The He-4/Ne-20 ratio (mean value of 49) in the breccia was systematically lower than in basalt (mean value of 78). Possibly, this may be due to fractionation of He and Ne during and after breccia formation. Pronounced differences observed in the He-4/Ne-3 ratio are attributed to the presence of variable quantities of cosmogenic He-3. This means that either the solar wind intensity varied in time, or that small-ratio particles were exposed to solar radiation rich in He-3 and/or H-3. The exposure ages of four particles are several hundred million years. The Ar-40/Ar-36 ratio is 0.65 for breccia and basalts.

  6. Ouarkziz Impact Structure, Algeria: Preliminary Petrographic and Geochemical Studies

    Science.gov (United States)

    Sahoui, R.; Belhai, D.

    2015-07-01

    Ouarkziz impact crater in Algeria is set in Namurian lower limestone and marls with gypsum. We present here preliminary petrographic and geochemical studies of the rocks and breccias forming the rings ans the central area of the structure.

  7. Shock-Induced Twinning of K-Spars Crystals — The Remarkable Feature of Glass-Poor Suevites of Zeleny Gay Astrobleme, Ukraine

    Science.gov (United States)

    Valter, A.

    2011-03-01

    The shock twins of microcline from the suevite-poor breccia of a small ancient impact crater from Ukrainian shield was investigated. The genesis of this rare phenomena was connected with the ricochet nature of impact.

  8. Biostratigraphic Indications of End Cretaceous Age of the Boltysh Impact Crater (Ukrainian Shield)

    Science.gov (United States)

    Valter, A. A.; Plotnikova, L. F.

    2003-03-01

    The complexes of foraminifera in ejecta breccia fragments and in ejecta covering sediments were determined. According to these data the time interval of crater formation is detected to be 66.8 - 65 Ma.

  9. Micro-XRF Study of the Buzzard Coulee Meteorite

    Science.gov (United States)

    Higgins, M. D.; Herd, C. D.; Walton, E. L.

    2011-03-01

    A 50 by 50 mm slice of the Buzzard Coulee H4 breccia was examined using optical and micro-XRF methods. Fragments are clearly revealed which have contrasting compositions and fabrics. Fabric was developed early during accretion.

  10. Identification of Rocks on Planetary Surface Using Husar-9 Rover Camera: Field Work Simulations with Hunveyor-9 Space Probe Model System at Eötvös High School, Tata, Hungary

    Science.gov (United States)

    Magyar, I.; Badics, A.; Bakonyi, I.; Csiszár, Á.; Franko, M.; Gyürki, Á.; Héricz, M.; Marschall, B.; Nagyházi, Á.; Varga, T. N.; Végh, Gy.; Varga, T. P.; Bérczi, Sz.

    2009-03-01

    We studied the rock types along the Husar-9 rover’s path and identified them on the basis of their shape, color and surface textures: komatiite, basalt, granite, conglomerate, schist rock, porphyritic granite, suevite breccia, and vesicular basalt.

  11. Geology characteristics and prospecting model discussing of sodic-metasomatic type uranium deposits in Longshoushan

    International Nuclear Information System (INIS)

    Alkali-metasomatic type uranium deposits is an important uranium ore type in Longshoushan ore belt. In this paper, it introduces ore features and forming mechanism of Alkali-metasomatic type uranium deposits in Longshoushan. By discussing the features and forming reason of ore bearing area crypto-explosive breccia, it sets up the prospecting model which makes crypto-explosive breccia to be prospecting target. (authors)

  12. Mineral exploration in the area of the Fore Burn igneous complex, south-western Scotland

    OpenAIRE

    P M Allen; Cooper, D. C.; Parker, M.E.; Easterbrook, G.D.; Haslam, H.W.

    1982-01-01

    The Fore Burn igneous complex consists mainly of quartz-microdiorite, tonalite and feldspar porphyry forming semiconcordant or concordant bodies within early Devonian volcanic and sedimentary rocks, just north of the Southern Upland Fault, some 24 km east of Girvan. There is evidence that the complex has been folded. Several small bodies of intrusion breccia occur within both the complex and the country rock and there is a zone of monolithologic breccias along a fau...

  13. Geological notes and local details for geological sheet SS91SE (Tiverton)

    OpenAIRE

    Lee, Jonathan R.

    2005-01-01

    This report describes and provides an initial interpretation of the bedrock and superficial geology of 1:10, 000 Geological Sheet SS 91 SE Tiverton (Devon). The geology of the area consists of Carboniferous sandstones and mudstones, which belong to the Bude Formation (Culm), in-turn these are unconformably overlain by Permian sandstone and breccias. The sandstone, typically a fine-grained sandstone or sandy mudstone, is informally called the ‘Tidcombe Sands’, whilst two breccias can be recogn...

  14. The Mg-suite and the highland crust: An unsolved enigma

    Science.gov (United States)

    Taylor, Stuart Ross; Norman, Marc D.; Esat, Tezer M.

    1993-01-01

    Most of the rocks returned from the highlands are polymict breccias, pulverized by the massive bombardment. However, some monomict breccias with low siderophile element contents are considered to be 'pristine' rocks that represent the original igneous components making up the highland crust. Three principal pristine constituents make up the lunar highland crust: ferroan anorthosites, the Mg-suite, and KREEP. A discussion of these three constituents is presented.

  15. Ancient Impact and Aqueous Processes at Endeavour Crater, Mars

    OpenAIRE

    Knoll, Andrew Herbert; Squyres, S. W.; Arvidson, R. E.; Bell, J. F.; Calef, F., III; Clark, B.C.; Cohen, B. A.; Crumpler, L. A.; P.A. Souza; Farrand, W. H.; Gellert, R.; Grant, J; Hurowitz, J. A.; Herkenhoff, K. E.; J. R. Johnson

    2012-01-01

    The rover Opportunity has investigated the rim of Endeavour Crater, a large ancient impact crater on Mars. Basaltic breccias produced by the impact form the rim deposits, with stratigraphy similar to that observed at similar-sized craters on Earth. Highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits. Gypsum-rich veins cut sedimentary rocks adjacent to the crater rim. The gypsum was precipitated from low-temperature aqueous fluids flowing...

  16. Geological characterization of Ia volcanic structure, Boyaca - Colombia

    International Nuclear Information System (INIS)

    Iza volcanic structure (5 grades 36 minutes 20 seconds N; 72 grades 59 minutes 33 seconds W) is the result of rising riodacitic to ryolithicmagmatic pulses, which didn't reach the surface, the first of them giving origin to intrusive breccias, interpreted as the result of indirect hot deep magma interaction with a sedimentary aquifer, leading to vapor overpressure and consequent fragmentation of the host rocks. The intrusive breccia form the southern part of the Iza edifice, it is massive beige to light red in color, locally with pseudo columnar joint; it is composed by angular to sub rounded sedimentary and minor igneous rock fragments in a porphyry rhyolitic matrix. This stage is followed by dome emplacement which a riodacitic to rhyolitic in composition. Petrographic analysis shows that they are similar to the matrix breccia; they have a porphiritic texture, phenocrist of sanidine, quartz and plagioclase and glassy matrix. Locally the domes are fractured presenting breccia facies (auto breccia and jig saw breccias, among others). Relationship with the host rock allow to interpreting the volcanic body as a cryptodomes, outcropping at surface by faulting and erosion.

  17. The spin zone: Transient mid-crust permeability caused by coseismic brecciation

    Science.gov (United States)

    Melosh, Benjamin L.; Rowe, Christie D.; Gerbi, Christopher; Bate, Charlotte E.; Shulman, Deborah

    2016-06-01

    Pore fluids migrating through the deep section of continental strike-slip fault zones have been invoked to explain such phenomena as tectonic tremor, stress transfer across the brittle-ductile transition, and short timescales of co-seismic healing. In this contribution, we describe a coseismic mechanism for forming transient vertical fluid conduits within dilational jogs in strike-slip faults. We present field observations of breccias that formed coseismically at dilational stepovers in the dextral Pofadder Shear Zone, a ∼ 1 Ga exhumed continental strike-slip fault in South Africa and Namibia. These breccias are interpreted to have formed when tensile fractures emanating from rupture tips intersected mylonitic foliation parallel to the rupture surface, which then failed, disaggregating the rock. We used quartz textures in the mylonites determined by electron backscatter diffraction to uniquely compare the orientation of each clast to the neighboring wall rock and constrain finite clast rotation within breccia bodies. Comparison of two- and three-dimensional rotation patterns show that clast trajectories are highly scattered when decoupled from wall rock, suggesting that Pofadder breccias were not formed by gradual plucking of clasts during slip. The dilational breccia bodies have sub-vertical geometries and high porosities relative to the host mylonites. We infer that the opening of these breccias may have created instantaneous, temporary vertical pathways for fluid draining through the brittle-plastic transition. These pathways healed post-seismically by cementation or ductile creep along the fault. The connection of many adjacent and overprinting breccia bodies through time provides a mechanism for fluid transport on a 10 s of km scale though the middle crust.

  18. Hydrothermal brecciation in the Jemez Fault zone, Valles Caldera, New Mexico: Results from CSDP (Continental Scientific Drilling Program) corehole VC-1

    Energy Technology Data Exchange (ETDEWEB)

    Hulen, J.B.; Nielson, D.L.

    1987-06-01

    Paleozoic and Precambrian rocks intersected deep in Continental Scientific Drilling Program corehole VC-1, adjacent to the late Cenozoic Valles caldera complex, have been disrupted to form a spectacular breccia sequence. The breccias are of both tectonic and hydrothermal origin, and probably formed in the Jemez fault zone, a major regional structure with only normal displacement since mid-Miocene. Tectonic breccias are contorted, crushed, sheared, and granulated; slickensides are commmon. Hydrothermal breccias, by contrast, lack these frictional textures, but arej commonly characterized by fluidized matrix foliation and prominent clast rounding. Fluid inclusions in the hydrothermal breccias are dominantly two-phase, liquid-rich at room temperature, principally secondary, and form two distinctly different compositional groups. Older inclusions, unrelated to brecciation, are highly saline and homogenize to the liquid phase in the temperature range 189 to 246/sup 0/C. Younger inclusions, in part of interbreccia origin, are low-salinity and homogenize (also to liquid) in the range 230 to 283/sup 0/C. Vapor-rich inclusions locally trapped along with these dilute liquid-rich inclusions document periodic boiling. These fluid-inclusion data, together with alteration assemblages and textures as well as the local geologic history, have been combined to model hydrothermal brecciation at the VC-1 site.

  19. Diamonds in an Archean greenstone belt: Diamond suites in unconventional rocks of Wawa, Northern Ontario (Canada)

    Science.gov (United States)

    Kopylova, Maya; Bruce, Loryn; Ryder, John

    2010-05-01

    Diamonds typically are found on Archean cratons entrained by younger Phanerozoic kimberlites. In contrast, Wawa diamonds are hosted in "unconventional", non-kimberlitic rocks that formed contemporaneously with the mafic and sedimentary rocks of the Archean Michipicoten Greenstone Belt (MGB). We studied two diamond suites that occur within the 2.9-2.7 Ga greenschist facies rocks of MGB located in the southwest portion of the Superior Craton (E. Canada). The first diamond suite henceforth referred to as the Wawa breccia diamonds (384 stones), are hosted in the 2618-2744 Ma calc-alkaline lamprophyres and volcaniclastic breccias, contemporaneous with pillow basalts and felsic volcanics of MGB. The second suite, the Wawa conglomerate diamonds (80 crystals), are hosted in the 2697-2700 Ma poorly sorted sedimentary polymictic conglomerate which is interpreted as a proximal alluvial fan debris flow in a fan-delta environment. The majority of the diamonds was found within the matrix of the conglomerate. The diamondiferous breccia occurs 20 km north of the town of Wawa, whereas the conglomerate is found 12 km northeast of Wawa. Diamonds from the 2 occurrences were characterized and described for provenance studies. Both the breccia and conglomerate diamonds show similar crystal habits, with the predominance of octahedral single crystals and ~ 10% of cubes. The conglomerate diamonds are significantly less resorbed (no resorbtion in 43% of the stones) than the breccia diamonds (8% non-resorbed stones). In both suites, only 21-24% show high degrees of resorption. The majority of crystals in both suites are colourless, with some yellow, brown and grey stones. Conglomerate diamonds had a wider variety of colours that were not seen in the breccia diamonds, including green and pink. The breccia diamonds contain 0-740 ppm N and show two modes of N aggregation at 0-30 and 60-95%. Among the breccia diamonds, Type IaA stones comprise 17%, whereas IaAB stones make up 49% of the

  20. Apollo 16 exploration of Descartes - A geologic summary.

    Science.gov (United States)

    1973-01-01

    The Cayley Plains at the Apollo 16 landing site consist of crudely stratified breccias to a depth of at least 200 meters, overlain by a regolith 10 to 15 meters thick. Samples, photographs, and observations by the astronauts indicate that most of the rocks are impact breccias derived from an anorthosite-gabbro complex. The least brecciated members of the suite include coarse-grained anorthosite and finer-grained, more mafic rocks, some with igneous and some with metamorphic textures. Much of the transverse area is covered by ejecta from North Ray and South Ray craters, but the abundance of rock fragments increases to the south toward the younger South Ray crater.

  1. Petrology and chemistry of hyperferroan anorthosites and other clasts from lunar meteorite ALHA81005

    Science.gov (United States)

    Goodrich, C. A.; Taylor, G. J.; Keil, K.; Boynton, W. V.; Hill, D. H.

    1984-01-01

    The results of petrographic and chemical studies of 11 previously undescribed clasts from the lunar meteorite Allan Hills A81005 are reported. The majority of lithic clasts in this regolith breccia are granular to cataclastic polymict breccias that are mixtures of ferroan anorthosites and troctolitic Mg-suite plutonic rocks with mg' greater than 84, An 97, and REE abundances consistent with those of known Mg-suite rocks. Clasts of appropriate Mg-suite end members have not been found in 81005, although magnesian olivine fragments are present. Impact-melt clasts similar in composition to bulk 81005 also occur. AH81005 is low in KREEP.

  2. Stratigraphy of Julian and Tuvalian Substage in the Oslica at Muljava Area (Slovenia

    Directory of Open Access Journals (Sweden)

    Stevo Dozet

    2002-12-01

    Full Text Available The Julian and Tuvalian lithologic column in the Oslica area starts with dolomitic breccias with limonitic groundmass and with a bauxite giving evidence of areal expose on the boundary between Cordevolian and Julian. Afterwards, precepitation of carbonate rocks followed. In the lithological interval where the limestone breccias predominate, oncolitic horizons are most characteristic. The Carnian sedimentary succession in the Oslica is terminated by a dolomite with intercalations of marls, bedded micritic limestones and a darkgrey dolomite with a roundish disintegration. The lithological composition and sedimentological characteristics of the succession indicate an origin in the littoral environment.

  3. Luminescence of Apollo 14 and Apollo 15 lunar samples.

    Science.gov (United States)

    Greenman, N. N.; Gross, H. G.

    1972-01-01

    Luminescence measurements have been made of Apollo 14 lunar samples with far UV, X-ray, and proton irradiation and of Apollo 15 lunar samples with X-ray irradiation. Preliminary efficiencies with the far UV are in the range .01 to .001; efficiencies with X-rays and protons are in the range .000001 to .00000001. The crystalline igneous rocks show higher efficiencies, in general, than the breccias and glasses, and the ratio of intensity of the green to the blue luminescence peak tends to be higher for the crystalline igneous rocks than for the breccias and glasses.

  4. Relationship between karstification and burial dolomitization in Permian platform carbonates (Lower Khuff - Oman)

    Science.gov (United States)

    Beckert, Julia; Vandeginste, Veerle; John, Cédric M.

    2016-08-01

    Large breccia fabrics associated with karst constitute an important structure in massive limestone successions. The dimensions and shapes of breccia structures are controlled by the initial fracture pattern of the limestone and preferential pathways of the karstifying fluids, but subsequently breccia fabrics can also govern the migration of later fluids. Therefore, breccias are highly relevant features to capture for reservoir characterisation. Outcrop analogues for Lower Khuff units in the Middle East present in the Central Oman Mountains reveal brecciated fabrics up to 10s of metres in diameter. These brecciated units are closely associated with dolomite bodies of late diagenetic origin. Based on an integrated set of data, the breccias are interpreted as collapsed karst cavities either formed by meteoric or hypogenic fluids. The exact origin of the fluids could not be constrained due to an overprint by later dolomitizing fluids. Based on the composition of the clasts and matrix in the breccias, two dolomitization events are interpreted to have affected the succession, one prior to (early diagenetic [ED] dolomite) and one after brecciation (late diagenetic [DT2] dolomite). Dolomite of shallow burial origin (ED dolomite) was only observed as clasts within breccia and is much more frequent than late diagenetic (medium to deep burial) dolomite clasts. Thus, the timing of the brecciation and collapse is assumed to postdate shallow burial early diagenetic dolomitization. Late diagenetic replacive dolomite (DT2 dolomite) forms 90% of the matrix in the breccia fabrics with the exception of a small area that was not affected by dolomitization, but is rarely present as clasts. Stable isotope measurements [δ18O: - 2.5‰ to - 6‰ VPDB and δ13C: 2.9‰ to 4.8‰ VPDB] suggest a burial origin for the late diagenetic dolomite potentially with the participation of hydrothermal fluids. The dolomitized matrix indicates a migration of late dolomitizing fluids subsequent to or

  5. Development, evolution, and destruction of the saline mineral area of Eocene Lake Uinta, Piceance Basin, western Colorado

    Science.gov (United States)

    Johnson, Ronald C.; Brownfield, Michael E.

    2015-01-01

    Halite and the sodium bicarbonate mineral nahcolite were deposited in Eocene-age saline Lake Uinta in the Piceance Basin, northwestern Colorado. Variations in the areal extent of saline mineral deposition through time were studied using descriptions of core and outcrop. Saline minerals have been extensively leached by groundwater, and the original extent of saline deposition was determined from the distribution of empty vugs and collapse breccias. Because vugs and breccias strongly influence groundwater movement, determining where leaching has occurred is an important consideration for in-situ oil shale extraction methods currently being developed.

  6. Heterogeneity in friction strength of an active fault by incorporation of fragments of the surrounding host rock

    Science.gov (United States)

    Kato, Naoki; Hirono, Tetsuro

    2016-07-01

    To understand the correlation between the mesoscale structure and the frictional strength of an active fault, we performed a field investigation of the Atera fault at Tase, central Japan, and made laboratory-based determinations of its mineral assemblages and friction coefficients. The fault zone contains a light gray fault gouge, a brown fault gouge, and a black fault breccia. Samples of the two gouges contained large amounts of clay minerals such as smectite and had low friction coefficients of approximately 0.2-0.4 under the condition of 0.01 m s-1 slip velocity and 0.5-2.5 MP confining pressure, whereas the breccia contained large amounts of angular quartz and feldspar and had a friction coefficient of 0.7 under the same condition. Because the fault breccia closely resembles the granitic rock of the hangingwall in composition, texture, and friction coefficient, we interpret the breccia as having originated from this protolith. If the mechanical incorporation of wall rocks of high friction coefficient into fault zones is widespread at the mesoscale, it causes the heterogeneity in friction strength of fault zones and might contribute to the evolution of fault-zone architectures.

  7. Geotechnical considerations for radiological hazard assessment of WIPP: a report of a meeting held on January 17-18, 1980

    International Nuclear Information System (INIS)

    Summary reports from a meeting of the Environmental Evaluation Group on geologic and hydrologic mechanisms which might lead to the release of radionuclides from the WIPP repository are presented. The following topics are discussed: ground water hydrology, deep dissolution and breccia pipes; brine reservoirs; faults, dikes, folds, and diapiric structures; and human intrusion

  8. Alteration of a Martian Impact Regolith Recorded in NWA 8114

    Science.gov (United States)

    Bridges, J. C.; MacArthur, J. L.; Hicks, L. J.; Burgess, R.; Joy, K.

    2015-07-01

    A TEM, XANES, Ar-Ar study of martian breccia NWA 8114 shows it underwent high T oxidation and breakdown of px to Fe oxide, amorphous silicate and recrystallised px. This together with veining and accretionary rim formation reset the Ar-Ar.

  9. Application of soil radon and trace element geochemistry for uranium exploration at Kuchanapalle, Guntur District, Andhra Pradesh

    International Nuclear Information System (INIS)

    A radioactive fault breccia zone trending N30deg E is exposed intermittently within the Ipuru granite dome, near Kuchanapalle village in the NE margin of Cuddapah basin. A major part of the fault zone is under soil cover. Within this fault zone, a dark coloured ferruginous and uraniferous fault breccia is exposed over an area of 150m x 2.5m. In order to trace the continuity of the concealed fault zone, the uraniferous breccia zone was tested by closed circuit soil-gas radon (CCT) measurement, solid state nuclear track detection (SSNTD) survey, and trace element analysis of augur-hole soil samples. Radon levels in 164 auger holes vary from 9 to 863 per 50 sec. The alpha track density on cellulose nitrate films used in SSNTD surveys varies from 27 to 820 per sq.mm. The iso-alpha track density map has confirmed the anomalous patterns obtained by the soil-radon survey. Trace element data of soil samples have been processed using R-mode factor analysis of correlation matrix. These data along with radon and SSNTD surveys have thus been found to be very effective in delineating the extension of the radioactive breccia zone under soil cover, up to 1200 m towards north. (author)

  10. Aquifer characterization through the construction of groundwater production Well in Suwawal Village, Pakis Aji Sub District, Jepara

    International Nuclear Information System (INIS)

    Kampung teknologi Jepara located in Suwawal Village, Pakis Aji Sub District, Jepara Regency, Central Java with an area of ±140 Ha. Integrated analysis from groundwater surveys resulting two (2) potential location, which is SWL-10 (potential 1) and SWL-21 (potential 2). Potential aquifers of SWL-10 located in a depth of 13 to 82 meters and >114 meters. Potential aquifers of SWL-21 located in a depth of 12 to 60 meters and >87 meters. Groundwater drilling conducted in SWL-10 shows that this area composed with lithologies such as: soil from weathered rocks (0 to 10 m depth), breccia (10 - 38 m depth), tuff with medium to coarse sandstone intercalation (38 to 68 m depth), sandy breccia (68 to 90 m depth), and tuff with medium to coarse sandstone intercalation (90 to 125 m depth). Water debit in this well as much as 5.8 1/s. Potential aquifers lithologies in this area are sandy breccia, breccia, and sandstone. (author)

  11. Geomorphological aspects of gypsum karst areas with special emphasis on exposed karst

    OpenAIRE

    Sauro U.

    1996-01-01

    Medium- to large-size forms in gypsum karst are described, including dolines, blind valleys, ploje-like depressions, collapses and positive and/or residual forms such as outliers, cone-like hills, dome-like hills, mesa-like tabular blocks and plateaux and breccia pipe hills. The similarities and/or difference between gypsum and carbonate forms are discussed.

  12. Occurrence of Siliceous Impact Melt in Netschaëvo IIE? A FIB-TEM Study

    Science.gov (United States)

    Hamann, C.; Van Roosbroek, N.; Greshake, A.; Pittarello, L.; Hecht, L.; Debaille, V.; Wirth, R.; Claeys, Ph.

    2015-07-01

    A silicate inclusion in a sample of the Netschaëvo IIE iron meteorite was studied with FIB-TEM. We present petrographic features indicating that this inclusion is quenched impact melt and suggest that Netschaëvo is an impact melt breccia.

  13. Holocene geology of central Africa

    OpenAIRE

    Thiéblemont, Denis

    2009-01-01

    N° Outcrop: MAK0101. View of a typical "lateritic profile" including a lateritic breccia (Stone Line) overlying an altered basement and a soft yellow cover (Cover Horizon). Note the sharp contact between Stone Line and Cover Horizon. The Stone Line is mainly composed of rounded ferricrust gravels.

  14. Holocene geology of central Africa

    OpenAIRE

    Thiéblemont, Denis

    2008-01-01

    N° Outcrop: Belinga-Palace. Detailed view of the "lateritic profile" of the Belinga Palace. The sedimentary nature (breccia) of the lateritic Stone Line clearly appears on this picture. The coarse facies on the left becomes thinner toward the right and shows very irregular lower and upper surfaces.

  15. The role of intrusions in the formation of Irish-type mineralisation

    Science.gov (United States)

    McCusker, Jim; Reed, Christopher

    2013-08-01

    The Stonepark Prospect is located in County Limerick, south-central Ireland. Multiple zones of Zn-Pb mineralisation have been identified at Stonepark and these are approximately 5 km west of the Pallas Green Prospect. At Stonepark, the sulphide bodies are hosted within the Waulsortian Limestone and closely resemble other Irish-type deposits. The mineralisation is composed of pyrite-marcasite, sphalerite and galena with gangue Fe-dolomite and calcite cements. A key difference at Stonepark is the presence of Chadian-aged volcanic rocks (Knockroe Volcanics) that intrude into and overlie the Waulsortian Limestone. Subsequent hydrothermal brecciation of the Waulsortian Limestone and Knockroe intrusions resulted in the formation of tabular polymict breccia bodies containing mixed carbonate and clasts of intrusive rocks. These have then been overprinted by massive sulphide mineralisation. Further syn-mineralisation brecciation has overprinted the earlier breccias. Drilling has demonstrated a spatial relationship between the volume of intrusive rocks (dykes and polymict breccias) and Zn-Pb mineralisation. This association suggests that the intrusive rocks provided a mechanism for the introduction of the mineralising fluids into the breccia bodies. This is significant as to date no large controlling fault has been identified, as is seen at other Irish-type deposits. Further work is required to understand the alteration process of the intrusive rocks and how this may relate to the mineralising process.

  16. Proceedings of the Geophysical Laboratory - Lawrence Radiation Laboratory Cratering Symposium

    Energy Technology Data Exchange (ETDEWEB)

    Nordyke, M. D.

    1961-10-01

    The geological papers in this morning's session will deal descriptively with surficial features and end products of impact craters caused by meteorite falls. Such items as breccia, structural deformation, normal and inverse stratigraphy, glass (fused rock), and coesite will frequently be mentioned. Meteor and explosion crater data are presented.

  17. Introduction to the Apollo collections. Part 1: Lunar igneous rocks

    Science.gov (United States)

    Mcgee, P. E.; Warner, J. L.; Simonds, C. H.

    1977-01-01

    The basic petrographic, chemical, and age data is presented for a representative suite of igneous rocks gathered during the six Apollo missions. Tables are given for 69 samples: 32 igneous rocks and 37 impactites (breccias). A description is given of 26 basalts, four plutonic rocks, and two pyroclastic samples. The textural-mineralogic name assigned each sample is included.

  18. Origin and evolution of palaeokarst within the Lower Ordovician (Ibexian) Goodwin Formation (Pogonip Group)

    Institute of Scientific and Technical Information of China (English)

    Robert; J.; Kervin; Adam; D.; Woods

    2012-01-01

    Palaeokarst within the Lower to Middle Ordovician Goodwin Formation, Pogonip Group (upper Ibexian-lower Whiterockian) was examined in detail at Meiklejohn Peak, Nevada USA in order to determine its origin, evolution, and relationship to sea level change. Detailed outcrop and petrographic examination of dolostone breccias and host rock reveals that palaeokarst was formed and affected by two distinct cycles of sea level change. A relative transgression resulted in deposition of lagoonal, ooid shoal, and shallow subtidal facies as sea level rose. Exposure of the carbonate platform led to the formation of multiple phreatic caves below the water table, as well as the development of numerous vadose conduits from the downward percolation of meteoric waters. Vadose water flow through early cave-wall and cave-roof collapse breccias resulted in rounding of smaller breccias clasts via physical transport and corrosion, while subsidence of subsurface karst led to the formation of a palaeodoline at the exposure surface. A second relative transgression deposited lagoonal sediments over the older karst; subsequent re-exposure of the carbonate platform resulted in the development of small breccia pockets as well as grikes within the youngest lagoonal sediments, and may have led to further corrosion of the older, deeper subsurface karst. The distal location of the study area within the carbonate platform suggests karst formation was the result of a substantial drop in relative sea level; the presence of multiple generations of palaeokarst imply that at least two higher-frequency cycles of sea-level change overprint the larger regression.

  19. Geology and geochemistry of newly discovered Tertiary carbonatite occurrences near Villa Ahumada area, Basin and Range province, Chihuahua, northern Mexico

    Science.gov (United States)

    Nandigam, Ravi Chenchu

    This study targets some newly discovered carbonatite occurrences located in the eastern Mexican Basin and Range province, a few kilometers to the east of Villa Ahumada, Chihuahua. The region containing these occurrences experienced compression related to subduction of the Farallon plate until about 32 Ma that was followed by Basin and Range extension. Geological mapping (1:5,000 scale), petrography, study of drill hole cuttings and satellite images, and major and trace element chemical analyses were utilized to understand the intrusive style of the carbonatites, their mineralogy and petrogenesis. The carbonatites, named Yuca, Mariana and El Indio, collectively intrude limestones, granitic intrusives and subduction-related tuffs and lavas mainly as a stock, breccias and dikes. The Yuca carbonatite was emplaced as a 900-m diameter stock, 500 x 350 m breccia body, numerous dikes and networks of fracture fillings. Crosscutting field relationships at Yuca suggest at least two stages of carbonatite emplacement. At Mariana, carbonatite was emplaced as a 750 x 350 m breccia. Four out of nine reverse circulation drill holes penetrated and bottomed in the breccia at an average depth of about 300 m At El Indio, carbonatite was emplaced as a 20 m diameter breccia pipe and a 1m thick sill. Major minerals present are calcite, Fe-rich calcite and hematite. Sporadic presence of fluorite is common. At Mariana, two generations of grossular-rich garnets associated with limestones and granite porphyry respectively are recognized. It is inferred that garnets in granite porphyry represent metasomatic alteration due to the emplacement of carbonatite breccia. Parental magmas of Yuca carbonatites have undergone differentiation under low fO2 conditions during which they were progressively enriched in iron. The carbonatite compositional types recognized based on major element data, in the sequence of least to most highly differentiated, are (1) magnesio-, (2) calcio- and (3

  20. Study of aquifer's characteristic at BPLP-BATAN, Cipanas, West Java

    International Nuclear Information System (INIS)

    Farms Observational Land Agricultural (BPLP) BATAN lies at Palasari's Village, Cipanas's district, Cianjur's regency, West Java. The currently used water resources, come from shallow well that groundwater's quality adverse, brownish rust colored, so indecent being utilized as source of fresh water. Drilling activity of groundwater exploration is objected in order to obtain aquifer's characteristics which cover lithology, porosity of lithology, ground water condition that interpreted from well cutting, bores-hole geophysical data, pumping test data and water quality on the aquifer. These Regions constitute geologically volcanic rock, varied of volcanic breccia with grain size of sand to boulder. Potential aquifers at these regions are conglomeratic sandstone, breccias, and sandstone. The result of drilling activity shows that its lithology are yield of soil (depth 0-6 m), breccia (36-38 m), middle-rough sandstone (depth 38-40 m), breccia (40-52 m), sandy breccia (depth 52-97 m) and inter spaced tuff with middle-rough sandstone (depth 97-125 m). As a result, therefore, the well has been constructed with straight PVC pipe 6'', on depth of 0-40 m made by grouting cements, screen is assembled on depth of 60-82 m and 90-110 m. Result of pumping test that well's with maximum debit 17,25 L/sec, and optimum debit 13,2 L/sec. Static water level on 11 m depth. Current assembled pump is 5 L/sec on the 86 m depth. Result of groundwater quality test in laboratory shows that the water has good quality with fresh water quality standard, which mean that the water is suitable to be consumed. (author)

  1. Stable isotope studies of the Glen Eden Mo-W-Sn deposit, New England Batholith - Australia

    International Nuclear Information System (INIS)

    The Glen Eden Mo-W-Sn deposit is located 17 km northeast of Glen Innes in northeastern New South Wales. This deposit is located in the Late-Permian Emmaville Volcanics and mineralisation is related to the intrusion of the Glen Eden Granite (GEG). Glen Eden Granite is a highly-fractionated, most probably, I-type granite and it occurs as dykes at depths of more than 80 m and is not exposed at the surface. Mineralogical studies and field evidence indicate that the observed dykes have intruded after initiation of the hydrothermal activity. The Glen Eden orebody is composed of a pipe-like breccia body, veins and stockworks including moderately to steeply dipping, mainly NW- and NE- striking ore-bearing veinlets. Also, there are some ores in altered felsic volcanic wall rock, especially the greisen zone. The ore minerals include molybdenite, wolframite, cassiterite, Bi-bearing minerals and base metal sulfides. Two main mineralisation stages can be recognised: 1) before main brecciation (pre-breccia stage). 2) after main brecciation (post-breccia stage). The isotopic composition of the hydrothermal fluid at the pre-breccia stage is different from that at the post-breccia stage (see below). The main stage of ore mineralisation, based on fluid inclusion studies, has occurred at 280 to 360 deg C. Hydrothermal alteration at Glen Eden is similar to porphyry-type ore deposits and has been developed largely in the felsic volcanic host rocks. However, sericitic alteration has developed pervasively and formed the greisen zone. Various alteration styles include biotitic, greisen, potassic, argillic and propylitic types. Muscovite from greisen has given an early Triassic age of 240 Ma (Plimer,l.R., pers. comm., 2000). This paper summaries the stable isotope studies of this deposit

  2. Two-stage structural development of a Paleozoic auriferous shear zone at the Globe-Progress deposit, Reefton, New Zealand

    International Nuclear Information System (INIS)

    The Globe-Progress gold deposit at Reefton is hosted in a curvilinear mineralised zone that cuts Paleozoic Greenland Group basement metagreywackes. Two discrete phases of mineralisation have resulted in the formation of five different ore types along the shear. An initial phase of mineralisation formed hydrothermal quartz veins and associated Au, As, and S enrichment, with low-grade mineralised host rock. These quartz veins and mineralised host rocks form the outer regions of the mineralised zone. A second hydrothermal phase introduced Sb, Au, As, and S during brittle shear deformation focused on the pre-existing mineralised rocks. This deformation and mineralisation resulted in the formation of metre-scale cataclasite ore and quartz breccia from mineralised host rock and hydrothermal quartz veins, respectively. Cataclasite was derived from argillite layers in the host rock, from which Na, Fe, and Mg have been leached during mineralisation; Al, Ti, and Cr have been conserved; and there has been minor enrichment in Sr, Pb, Zn, and Cu. No quartz was added to the cataclasite or quartz breccia during mineralisation, but some quartz recrystallisation occurred locally, and quartz clasts were physically incorporated into the cataclasite during deformation. The presence of euhedral sulfides in the cataclasite (40% of total sulfides), late-stage undeformed stibnite veins infilling breccia (1-5 cm3 scale), and undeformed free gold in quartz breccia, imply that the second phase of mineralisation persisted both during and after cataclasis and brecciation. Antimony deposition is greatest in the central cataclasite, up to 6 wt%, and locally in the quartz breccia where stibnite veins are present. Concentrations of Sb decrease with distance from the shear zone. The second, Sb-rich phase of mineralisation in the Globe-Progress deposit resembles similar Sb-rich overprints in the correlative Victorian goldfield of Australia. (author). 38 refs., 10 figs., 1 tab.

  3. Reverse Polarity Magnetized Melt Rocks from the Cretaceous/Tertiary Chicxulub Structure, Yucatan Peninsula, Mexico

    Science.gov (United States)

    Urrutia-Fucugauchi, J.; Marin, Luis; Sharpton, Virgil L.

    1994-01-01

    We report paleomagnetic results for core samples of the breccia and andesitic rocks recovered from the Yucatan-6 Petrolcos Mexicanos exploratory well within the Chicxulub structure (about 60 km SSW from its center), northern Yucatan, Mexico. A previous study has shown that the rocks studied contain high iridium levels and shocked breccia clasts and an Ar/Ar date of 65.2 +/- 0.4 Ma. Andesitic rocks are characterized by stable single-component magnetizations with a mean inclination of -42.6 deg +/- 2.4 deg. Breccias present a complex paleomagnetic record characterized by multivectorial magnetizations with widely different initial NRM inclinations. However, after alternating field demagnetization, well defined characteristic components with upward inclinations are defined. IRM acquisition experiments, comparison of IRM and NRM coercivity spectra and the single component magnetization of the andesitic rocks indicate the occurrence of iron-rich titanomagnetites of single or pseudo-single domain states as the dominant magnetic carriers. Mean inclinations from the andesitic rocks and most of the breccia samples give a mean inclination of about -40 deg to -45 deg, indicating a reverse polarity for the characteristic magnetization that is consistent with geomagnetic chron 29R, which spans the Cretaceous/Tertiary (K/T) boundary. The inclination is also consistent with the expected value (and corresponding paleolatitude) for the site estimated from the reference polar wander curve for North America. We suggest that the characteristic magnetizations for the andesitic and breccia rocks are the result of shock heating at the time of formation of the impact structure and that the age, polarity and pateolatitude are consistent with a time at the K/T boundary.

  4. Rock and Roll at the Apollo 17 Site

    Science.gov (United States)

    Martel, L. M. V.

    2016-06-01

    Astronauts Eugene A. Cernan and Harrison H. (Jack) Schmitt collected 243 pounds (110 kg) of rock and regolith samples during 22 hours working on the lunar surface during the Apollo 17 mission in December 1972, while Astronaut Ronald Evans orbited in the command module. The field observations, audio descriptions, and photographs coupled with orbital data and detailed, laboratory analyses of Apollo samples provided unprecedented information about the Moon and its geologic history. The Apollo samples continue to inspire new questions and answers about the Moon. Debra Hurwitz and David Kring (Lunar and Planetary Institute and NASA Solar System Exploration Research Virtual Institute; Hurwitz now at NASA Goddard Space Flight Center) were particularly interested in solving the mystery of where the boulders came from at the base of the North Massif (station 6) and at the base of the South Massif (station 2) from which Apollo 17 astronauts collected samples of impact melt breccias. The breccias were unequivocally formed by impact processes, but forty years of analyses had not yet determined unambiguously which impact event was responsible. Was it the basin-forming event of the landing site's neighbor Serenitatis (possibly Nectarian age); the larger, nearby Imbrium basin (Imbrian age and one of the last large basins to form); a combination of these impacts or an impact event older or younger than all of the above. Tracking down the origin of the boulders would ideally unravel details of the formation age of the breccias and, ultimately, help with the historical record of basin formation on the Moon. Hurwitz and Kring verified the boulders rolled down from massif walls - Apollo 17 impact melt breccias originated in massif material, not from the Sculptured Hills, an overlying geologic unit. But the relative geologic context is easier to explain than the absolute age, at least until some discrepancies are resolved in existing Ar-Ar and U-Pb radiometric ages of the Apollo 17

  5. Postimpact heat conduction and compaction-driven fluid flow in the Chesapeake Bay impact structure based on downhole vitrinite reflectance data, ICDP-USGS Eyreville deep core holes and Cape Charles test holes

    Science.gov (United States)

    Malinconico, M.L.; Sanford, W.E.; Wright, Horton W.J.J., Jr.

    2009-01-01

    Vitrinite reflectance data from the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville deep cores in the centralcrater moat of the Chesapeake Bay impact structure and the Cape Charles test holes on the central uplift show patterns of postimpact maximum-temperature distribution that result from a combination of conductive and advective heat flow. Within the crater-fill sediment-clast breccia sequence at Eyreville, an isoreflectance (-0.44% Ro) section (525-1096 m depth) is higher than modeled background coastal-plain maturity and shows a pattern typical of advective fluid flow. Below an intervening granite slab, a short interval of sediment-clast breccia (1371-1397 m) shows a sharp increase in reflectance (0.47%-0.91% Ro) caused by conductive heat from the underlying suevite (1397-1474 m). Refl ectance data in the uppermost suevite range from 1.2% to 2.1% Ro. However, heat conduction alone is not sufficient to affect the temperature of sediments more than 100 m above the suevite. Thermal modeling of the Eyreville suevite as a 390 ??C cooling sill-like hot rock layer supplemented by compaction- driven vertical fluid flow (0.046 m/a) of cooling suevitic fluids and deeper basement brines (120 ??C) upward through the sediment breccias closely reproduces the measured reflectance data. This scenario would also replace any marine water trapped in the crater fill with more saline brine, similar to that currently in the crater, and it would produce temperatures sufficient to kill microbes in sediment breccias within 450 m above the synimsuevite. A similar downhole maturity pattern is present in the sediment-clast breccia over the central uplift. High-reflectance (5%-9%) black shale and siltstone clasts in the suevite and sediment-clast breccia record a pre-impact (Paleozoic?) metamorphic event. Previously published maturity data in the annular trough indicate no thermal effect there from impact-related processes. ?? 2009 The

  6. Paleocollapse structures as geological record for reconstruction of past karst processes during the upper miocene of Mallorca Island

    Directory of Open Access Journals (Sweden)

    Robledo Ardila Pedro A.

    2004-12-01

    Full Text Available Paleocollapse structures and collapse breccias are one of the major features for paleokarst analysis and paleoclimate record. These are affecting the Llucmajor and Santanyí carbonate platforms. These platforms, of southern and eastern Mallorca respectively, are a good example of progradation reef platform in the western Mediterranean. The Santanyí platform is constituted of two sedimentary units, both affected by paleocollapse structures: (1 The Reef Complex attributed to the upper Tortonian-lower Messinian; (2 Santanyí Limestone attributed to the Messinian. There are abundant paleocollapse outcropping in the Reef Complex and Santanyí Limestone units. These structures have been produced by roof collapse of caverns developed in the underlying reefal complex. According to the genetic model, the origin of same paleocollapse structures may be related to early diagenetic processes controlled by high-frequency sea-level fluctuations. During the lowstands of sea level, fresh water flow or mixing zone might have created a cave system near the water table by dissolution of aragonite in the reef front facies and coral patches existing in the lagoonal beds. During subsequent rise and highstands of sea level, inner-shelf beds overlaid the previously karstified reef-core and outer-lagoonal beds. Increase of loading by subsequent accretion of the shallow-water carbonate might have produced paleocollapse structures by gravitational collapse of cave roof. Morphometric and structural classification of paleocollapse is based on geometric and structural criteria according to the type of deformed strata and strata dip. Paleocollapse structures can be classified according to geometric section, size of the paleocave and lithification degree of the host rock when collapsed. Breccias are classified as crackle, mosaic and chaotic types. In same paleocollapse the type of breccias present a vertical and lateral gradation, from crackle in the upper part, to chaotic in

  7. In situ laser ablation ICP-MS analyses of dimict diogenites: Further evidence for harzburgitic and orthopyroxenitic lithologies

    Science.gov (United States)

    Beck, Andrew W.; McSween, Harry Y.; Bodnar, Robert J.

    2013-06-01

    Trace element concentrations in pyroxene, plagioclase, and olivine were measured in five diogenite breccias previously identified as containing distinct harzburgitic (ol+opx) and orthopyroxenitic (opx) lithologies (dimict). Three samples show two distinct populations of pyroxene trace element abundances, supporting their classification as dimict. These three meteorites show increases in Y, Yb, and HREE concentrations from harzburgitic to orthopyroxenitic pyroxenes, supporting the hypothesis that the lithologies are related through fractional crystallization whereby harzburgite olivine and pyroxene crystallized from the magma first followed by orthopyroxenite pyroxene. Depletions in LREE and Eu concentrations in the orthopyroxenitic lithology are most likely due to equilibration with LREE and Eu-rich phases, likely plagioclase, which is found primarily in that lithology. Two samples do not show evidence supporting a dimict classification. Large pyroxene trace element variation in one sample indicates that it is polymict, while uniform trace element distribution in the other suggests that it may be a monomict breccia.

  8. Mexico's giant fields, 1978-1988 decade

    Energy Technology Data Exchange (ETDEWEB)

    Acevedo, J.S.; Pemex, A.B.S.

    1990-09-01

    Twenty giant oil and gas fields were discovered in Mexico during the period of 1978-1988. The fields, located in adjacent areas, are described in terms of stratigraphy, tectonics, and general characteristics of the reservoirs. Production and reserves figures are also included. The two main oil productive areas in Mexico, Chiapas-Tabasco and offshore Campeche Sound, contribute 92% of Mexico's Mesozoic production. Production comes from Upper Jurassic carbonates; Cretaceous calcareous breccias, limestones, and dolomites; and from lower Paleocene calcareous breccias. The fields represented include 11 from the Chiapas-Tabasco area (Agave, Paredon, Iris, Giraldas, Cardenas, Jujo, Bellota, Tecominoacan, Muspac, Sen, and Luna) and nine from the the Campeche Sound area (Abkatun, Ku, Chuc, Ek, Pol, Malob, Caan, Uech, and Batab).

  9. Unusual Cathodoluminescence in Diamonds: Evidence for Metamorphism or a Source Characteristic

    Science.gov (United States)

    Bruce, L. F.; Longo, M.; Kopylova, M.; Ryder, J.

    2009-05-01

    Cathodoluminescence (CL) is a useful means of diamond "fingerprinting". CL-active cratonic macrodiamonds usually cathodoluminesce blue or yellow, and always exhibit prominent wide CL emittance peaks at 430-450 nm and 480-490 nm. Exceptions to this norm are diamond suites recently discovered in the Archean rocks metamorphosed in the greenschist facies. These macrodiamonds cathodoluminesce red, orange and yellow, and invariably exhibit the most prominent CL peak at 520 nm. The diamond suites with the unusual CL are derived from two different locations within the Michipicoten Greenstone Belt (Southern Superior craton), near the town of Wawa (Ontario). One suite is extracted from the 2.68-2.74 Ga polymict volcanic breccias and lamprophyres and the other suite - from the 2.68 Ga sedimentary conglomerates grading into overlying sandstones of the Dore assemblage. The diamondiferous conglomerates are found in an area 8 km south of the breccias and 12 km northeast of Wawa. CL emittance of macrodiamonds (> 0.5 mm) extracted from the breccias consists of a broad band at 520 nm, a sharp peak at 575.5 nm, and several lines at 550-670 nm. The conglomerate macrodiamonds mostly show a dominant peak at 520 nm, whereas corresponding microdiamonds exhibit two peaks at about 576 and 600 nm. None of the diamonds show a maximum peak at 420 nm. Polycrystalline stones from conglomerates show distinct CL spectra and colours for all intergrown crystals in the same diamond. The relative abundances of the CL colors of the conglomerate diamonds are orange-red (46%), yellow (28%), orange-green (10%), green (6%), and non-uniform colors (10%). These colours are more diverse than mostly orange CL colours in the breccia diamonds; this results from a larger variety of positions and intensity of CL peaks in the conglomerate diamonds. We propose two models for explaining the presence of the 520 nm CL peak in the breccia and conglomerate diamonds in Wawa. The first model suggests metamorphism as the

  10. Genesis of the central zone of the Nolans Bore rare earth element deposit, Northern Territory, Australia

    Science.gov (United States)

    Schoneveld, Louise; Spandler, Carl; Hussey, Kelvin

    2015-08-01

    The Nolans Bore rare earth element (REE) deposit consists of a network of fluorapatite-bearing veins and breccias hosted within Proterozoic granulites of the Reynolds Range, Central Australia. Mineralisation is divided into three zones (north, central, and south-east), with the north and south-east zones consisting of massive REE-bearing fluorapatite veins, with minor brecciation and carbonate infill. The central zone is distinctively different in mineralogy and structure; it features extensive brecciation, a high allanite content, and a large, epidote-rich enveloping alteration zone. The central zone is a reworking of the original solid apatite veins that formed during the Chewings Orogeny at ca. 1525 Ma. These original apatite veins are thought to derive from phosphate-rich magmatic-hydrothermal fluid exsolved from as-yet unrecognised alkaline magmatic bodies at depth. We define four ore breccia types (BX1-4) in the central zone on the basis of detailed petrological and geochemical analysis of drillcore and thin sections. BX1 ore comprises fluorapatite with minor crackle brecciation with carbonate infill and resembles ore of the north and south-east zones. Breccia types BX2, BX3, and BX4 represent progressive stages of ore brecciation and development of calc-silicate mineral (amphibole, epidote, allanite, calcite) infill. Comparison of bulk ore sample geochemistry between breccia types indicates that REEs were not mobilised more than a few centimetres during hydrothermal alteration and brecciation. Instead, most of the REEs were partitioned from the original REE fluorapatite into newly formed allanite, REE-poor fluorapatite and minor REE carbonate in the breccias. Negative europium (Eu) anomalies in the breccia minerals are accounted for by a large positive Eu anomaly in epidote from the alteration zones surrounding the ore breccias. This observation provides a direct link between ore recrystallisation and brecciation, and the formation of the alteration halo in

  11. Experimental petrology and origin of rocks from the Descartes Highlands

    Science.gov (United States)

    Walker, D.; Longhi, J.; Grove, T. L.; Stolper, E.; Hays, J. F.

    1973-01-01

    Petrographic studies of Apollo 16 samples indicate that rocks 62295 and 68415 are crystallization products of highly aluminous melts. 60025 is a shocked, crushed and partially annealed plagioclase cumulate. 60315 is a recrystallized noritic breccia of disputed origin. 60335 is a feldspathic basalt filled with xenoliths and xenocrysts of anorthosite, breccia, and anorthite. The Fe/(Fe+Mg) of plagioclase appears to be a relative crystallization index. Low pressure melting experiments with controlled Po2 indicate that the igneous samples crystallized at oxygen fugacities well below the Fe/FeO buffer. Crystallization experiments at various pressures suggest that the 62295 and 68415 compositions were produced by partial or complete melting of lunar crustal materials, and not by partial melting of the deep lunar interior.

  12. Groundwater drilling location determination in Girirejo Village, Tempuran Sub-District, Magelang

    International Nuclear Information System (INIS)

    Girirejo Village is one of the villages in Tempuran Sub-district, Magelang Regency which have fresh water difficulty. Determination of groundwater drilling location conducted with phases of activity include desk study stage, topographic data collection, geology and hydrogeology mapping, geo electrical surveys, and integrated analysis. Based on the results of field geological mapping, it is found that the area is composed of three rock units, namely andesite, breccia tuff and sandy tuff. Results of rock resistivity measurements show the value of resistivity 16 - 32 ohm-m are interpreted as sandy tuff with wet conditions, and the value of resistivity 60 - 80 ohm-m is interpreted as a breccia. Location TMG-14 at depths of 1.6 - 29.1 m by 27.5 m thick aquifer is a potential point which next recommended as potential sites of groundwater drilling. (author)

  13. Earthquake fault rock indicating a coupled lubrication mechanism

    Directory of Open Access Journals (Sweden)

    S. Okamoto

    2006-08-01

    Full Text Available A pseudotachylyte bounded by a carbonate-matrix implosion breccia was found at a fossilized out-of-sequence thrust in the Shimanto accretionary complex, Japan. This occurrence resulted from the following events: first implosion of host rock due to interstitial fluid pressure increase and asymmetric fracturing; second, Ca-Fe-Mg carbonate precipitation; and third, frictional melting. The rock-record suggests that these events took place in a single seismogenic slip event. Resulting from abrupt drop in fluid pressure after implosion, hydro-fracturing and fluid escape, recovered high effective friction promoted melting during fault movement. Coexistence of fluid implosion breccia and pseudotachylyte has never been reported from continental pseudotachylyte, but might be characteristic from hydrous seismogenic faults in subduction zone

  14. Shock-induced effects in calcite from Cactus Crater

    Science.gov (United States)

    Vizgirda, J.; Ahrens, T. J.; Tsay, F.-D.

    1980-01-01

    The paper discusses shock metamorphism of calcite from coralline limestone samples retrieved from a borehole drilled into rocks beneath Cactus Crater, a nuclear explosion crater at Eniwetok Atoll. The metamorphism was detected and quantified using electron spin resonance (ESR); the ESR spectra of Mn(+) present as a trace constituent in the coral samples, show a consistent decrease in hyperfine peak splitting with decreasing depth of sample. It is suggested that the decrease in hyperfine peak splitting reflects a decrease in crystal field splitting, and therefore, small increases on cation-anion distances produced by mechanical energy input during the shock process. Two alternative crater models suggested by the ESR results are a depiction of a steady decay of the shock wave, and a delineation of a breccia lens with a breccia-bedrock interface at 20 plus or minus 5 m.

  15. Microstructural studies of rocks from the 25 S oceanic core complex, along the Central Indian Ocean Ridge

    Science.gov (United States)

    Soda, Yusuke; Sawaguchi, Takashi; Enomoto, Tsubasa; Takagi, Hideo; Neo, Natsuki; Morishita, Tomoaki; Kumagai, Hidenori

    2010-05-01

    This study shows the microstructural development of rocks from the 25° S oceanic core complex (OCC) along the Central Indian Ocean Ridge, located near the Rodriguez Triple Junction. The samples described here are recovered by three submersible SHINKAI 6500 dives (Kumagai et al., 2008, Morishita et al., 2009). Characteristic foliated rocks with slickenline are recognized at a top surface of OCC, making up platy landform. Attitudes of those rocks are striking NE-SW and dipping to the NW and SE at moderate angle (20-30° ). Direction of lineation structures is perpendicular to the divergence ridge axis. We collect 55 samples during the three dives, and evaluate 10 samples as deformed rocks based on hand specimen scale structures on the shipboard. Deformed rocks distributed around the OCC surface consist of peridotite, gabbro, basalt, breccia and those altered rocks. Although almost olivine grains in peridotite are altered and replaced by talc, which forms anastmosing texture, olivine remnants show mylonitic texture characterized by undulose extinction and grain size reduction. Orthopyroxene grains are also elongated. Serpentine with platy shape makes up foliation, showing serpentinite mylonite texture. Olivine and serpentine are replaced by talc following mylonitization. Talc occurs as two different textures. One is static replacing primary minerals, and the other is syn-tectonic deformation textures such as foliated with shape preferred orientations, comprising talc schist. Gabbro also shows mylonitic structures featured by grain size reduction of plagioclase. Tremolite/actinolite is dominant facies in well foliated and altered gabbro in which has porphyroclasts of hornblende and plagioclase. Deformation of basalt is inhomogeneous and accompanying chloritization. Some part of basalt keeps plagioclase with basaltic textures, glassy texture and pseudomorph texture of them. Chlorite-rich basalt develops penetrative foliation and alters to chlorite schist. Breccia is

  16. Subsurface Geology of the Fenton Hill Hot Dry Rock Geothermal Energy Site

    Energy Technology Data Exchange (ETDEWEB)

    Levey, Schon S.

    2010-12-01

    The Precambrian rock penetrated by wells EE-2A and -3A belongs to one or more granitic to granodioritic plutons. The plutonic rock contains two major xenolith zones of amphibolite, locally surrounded by fine-grained mafic rock of hybrid igneous origin. The granodiorite is cut by numerous leucogranite dikes that diminish in abundance with depth. The most prominent structural feature is the main breccia zone, in which the rock is highly fractured and moderately altered. This zone is at least 75 m thick and is of uncertain but near-horizontal orientation. Fracture abundance decreases with increasing depth below the main breccia zone, and fractures tend to be associated with leucogranite dikes. This association suggests that at least some of the fractures making up the geothermal reservoir are of Precambrian age or have long-range orientations controlled by the presence of Precambrian-age granitic dikes.

  17. Age of the moon: An isotopic study of uranium-thorium-lead systematics of lunar samples

    Science.gov (United States)

    Tatsumoto, M.; Rosholt, J.N.

    1970-01-01

    Concentrations of U, Th, and Pb in Apollo 11 samples studied are low (U. 0.16 to 0.87; Th, 0.53 to 3.4; Pb, 0.29 to 1.7, in ppm) but the extremely radiogenic lead in samples allows radiometric dating. The fine dust and the breccia have a concordant age of 4.66 billion years on the basis of 207Pb/206Pb, 206Pb/238U, 207Pb/235U, and 208Pb/232Th ratios. This age is comparable with the age of meteorites and with the age generally accepted for the earth. Six crystalline and vesicular samples are distinctly younger than the dust and breccia. The 238U/235U ratio is the same as that in earth rocks, and 234U is in radioactive equilibrium with parent 238U.

  18. Reinterpretácia výskytov meliatika v oblasti Brádna a Rákoša (Revúcka vrchovina, Západné Karpaty

    Directory of Open Access Journals (Sweden)

    Alexander Lačný

    2015-06-01

    Full Text Available We present results of reinvestigation of two areas where, according to published geological maps, the Meliatic rocks should occur as tectonic slices inserted between the Turnaic Slovenská skala Nappe and the underlying Palaeozoic complexes of the Gemericum. However, these occurrences were not confirmed by our research. Instead, we document a continuous, though overturned, Lower–Middle Triassic succession of the Turnaicum in the area of Rákoš Village, since no typical Meliatic rocks were found there. Similarly, the supposed slivers of the Meliatic Bôrka Nappe near Brádno Village are reinterpreted as cataclastic tectonic breccias (rauhwackes. The breccias are dominantly composed of carbonate fragments with small portion of siliciclastic material derived from the overriding Turnaic thrust sheet. They likely formed during its nappe emplacement over the underlying Gemericum.

  19. Cryogenic Origin for Mars Analog Carbonates in the Bockfjord Volcanic Complex Svalbard (Norway)

    Science.gov (United States)

    Amundsen, H. E. F.; Benning, L.; Blake, D. F.; Fogel, M.; Ming, D.; Skidmore, M.; Steele, A.

    2011-01-01

    The Sverrefjell and Sigurdfjell eruptive centers in the Bockfjord Volcanic Complex (BVC) on Svalbard (Norway) formed by subglacial eruptions ca. 1 Ma ago. These eruptive centers carry ubiquitous magnesian carbonate deposits including dolomitemagnesite globules similar to those in the Martian meteorite ALH84001. Carbonates in mantle xenoliths are dominated by ALH84001 type carbonate globules that formed during quenching of CO2-rich mantle fluids. Lava hosted carbonates include ALH84001 type carbonate globules occurring throughout lava vesicles and microfractures and massive carbonate deposits associated with vertical volcanic vents. Massive carbonates include < or equal 5 cm thick magnesite deposits protruding downwards into clear blue ice within volcanic vents and carbonate cemented lava breccias associated with volcanic vents. Carbonate cements comprise layered deposits of calcite, dolomite, huntite, magnesite and aragonite associated with ALH84001 type carbonate globules lining lava vesicles. Combined Mossbauer, XRD and VNIR data show that breccia carbonate cements at Sverrefjell are analog to Comanche carbonates at Gusev crater.

  20. Igneous history of the aubrite parent asteroid - Evidence from the Norton County enstatite achondrite

    Science.gov (United States)

    Okada, Akihiko; Keil, Klaus; Taylor, G. Jeffrey; Newsom, Horton

    1988-01-01

    Numerous specimens of the Norton County enstatite achondrite (aubrite) were studied by optical microscopy, electron microprobe, and neutron-activation analysis. Norton County is found to be a fragmental impact breccia, consisting of a clastic matrix made mostly of crushed enstatite, into which are embedded a variety of mineral and lithic clasts of both igneous and impact melt origin. The Norton County precursor materials were igneous rocks, mostly plutonic orthopyroxenites, not grains formed by condensation from the solar nebula. The Mg-silicate-rich aubrite parent body experienced extensive melting and igneous differentiation, causing formation of diverse lithologies including dunites, plutonic orthopyroxenites, plutonic pyroxenites, and plagioclase-silica rocks. The presence of impact melt breccias (the microporphyritic clasts and the diopside-plagioclase-silica clast) of still different compositions further attests to the lithologic diversity of the aubrite parent body.

  1. Crystallization, flow and thermal histories of lunar and terrestrial compositions

    Science.gov (United States)

    Uhlmann, D. R.

    1979-01-01

    Contents: a kinetic treatment of glass formation; effects of nucleating heterogeneities on glass formation; glass formation under continuous cooling conditions; crystallization statistics; kinetics of crystal nucleation; diffusion controlled crystal growth; crystallization of lunar compositions; crystallization between solidus and liquidus; crystallization on reheating a glass; temperature distributions during crystallization; crystallization of anorthite and anorthite-albite compositions; effect of oxidation state on viscosity; diffusive creep and viscous flow; high temperature flow behavior of glass-forming liquids, a free volume interpretation; viscous flow behavior of lunar compositions; thermal history of orange soil material; breccias formation by viscous sintering; viscous sintering; thermal histories of breccias; solute partitioning and thermal history of lunar rocks; heat flow in impact melts; and thermal histories of olivines.

  2. 40Ar/39Ar geochronology of the El Teniente porphyry copper deposit

    International Nuclear Information System (INIS)

    Chile's El Teniente deposit is the largest known porphyry Cu-Mo orebody (>70 Mt Cu ), and is genetically related to Late Miocene-Early Pliocene igneous activity on the western slopes of the Andean Cordillera (cf. Howell and Molloy, 1960, Camus, 1975, Cuadra, 1986, Skewes and Stern, 1995). The deposit is 2700 m long by 1000 to 1700 m wide and is elongated in a N-S direction, with a recognized vertical extent of about 1800 m. Approximately 80% of the copper at El Teniente is distributed within a stockwork of mineralized veinlets and minor hydrothermal breccias within pervasively altered andesites, basalts and gabbros that are part of the Upper Miocene country rocks. Two intrusive bodies occur within the deposit, the Sewell Diorite (actually a tonalite) in the southeast part of the orebody and the dacitic Teniente Porphyry in its northern part. The Teniente Porphyry occurs as a north-south trending dike 1500 m long and 200 m wide. Minor quartz-diorite or tonalite intrusions known as the Central Diorite and the Northern Diorite occur along the eastern side of the deposit. Hydrothermal breccias commonly occur along the contacts of intrusive bodies with the country rocks. The Braden Breccia is a conspicuous diatreme in the center of the deposit that forms a pipe 1200 m in diameter at the surface, narrowing to 600 m at a depth of 1800 m. The Braden diatreme pipe is poorly mineralized (∼0.3% Cu), but it is surrounded by the copper-rich Marginal Breccia, a discontinuous rim of tourmaline-matrix hydrothermal breccia. Latite dikes intrude El Teniente, some forming altered ring dikes that encircle the Braden breccia pipe. After mineralization had ceased, the southern section of the deposit was cut by a 3.8 ± 0.3 Ma lamprophyre dyke, marking the end of igneous activity (Cuadra, 1986). Biotite-dominated K-silicate alteration is widespread within the orebody. In contrast, pervasive phyllic alteration is restricted to 'diorite' intrusions, and to the Braden and Marginal

  3. The Gao-Guenie impact melt breccia—Sampling a rapidly cooled impact melt dike on an H chondrite asteroid?

    Science.gov (United States)

    Schmieder, Martin; Kring, David A.; Swindle, Timothy D.; Bond, Jade C.; Moore, Carleton B.

    2016-04-01

    The Gao-Guenie H5 chondrite that fell on Burkina Faso (March 1960) has portions that were impact-melted on an H chondrite asteroid at ~300 Ma and, through later impact events in space, sent into an Earth-crossing orbit. This article presents a petrographic and electron microprobe analysis of a representative sample of the Gao-Guenie impact melt breccia consisting of a chondritic clast domain, quenched melt in contact with chondritic clasts, and an igneous-textured impact melt domain. Olivine is predominantly Fo80-82. The clast domain contains low-Ca pyroxene. Impact melt-grown pyroxene is commonly zoned from low-Ca pyroxene in cores to pigeonite and augite in rims. Metal-troilite orbs in the impact melt domain measure up to ~2 mm across. The cores of metal orbs in the impact melt domain contain ~7.9 wt% of Ni and are typically surrounded by taenite and Ni-rich troilite. The metallography of metal-troilite droplets suggest a stage I cooling rate of order 10 °C s-1 for the superheated impact melt. The subsolidus stage II cooling rate for the impact melt breccia could not be determined directly, but was presumably fast. An analogy between the Ni rim gradients in metal of the Gao-Guenie impact melt breccia and the impact-melted H6 chondrite Orvinio suggests similar cooling rates, probably on the order of ~5000-40,000 °C yr-1. A simple model of conductive heat transfer shows that the Gao-Guenie impact melt breccia may have formed in a melt injection dike ~0.5-5 m in width, generated during a sizeable impact event on the H chondrite parent asteroid.

  4. 長崎県に分布する赤黄色土の粘土鉱物組成

    OpenAIRE

    江頭, 和彦; 中島, 康夫; 秋山, 美保子; 林, 由紀子; 和仁, 佳子

    1987-01-01

    Red-Yellow soils are widely distributed on the mountains, hills, and plateaus in Nagasaki Prefecture, located at the most western part of Japan, and used as an important agricultural land. They are derived from various kinds of parent rock including basalt, andesite, andesitic tuff breccia, welded tuff, Tertiary sedimentary rock, and crystalline schist. The purpose of the present study is to investigate the clay mineralogical composition of the Red-Yellow soils in relation to their parent roc...

  5. The weathered Carboniferous Limestone at Bullslaughter Bay, South Wales: the first example of ghost-rock recorded in the British Isles

    Czech Academy of Sciences Publication Activity Database

    Rowberry, Matthew David; Battiau-Queney, Y.; Walsh, P.; Blažejowski, B.; Bout-Roumazeilles, V.; Trentesaux, A.; Křížová, L.; Griffiths, H.

    2014-01-01

    Roč. 17, č. 1 (2014), s. 33-42. ISSN 1374-8505 Institutional research plan: CEZ:AV0Z30460519 Keywords : deep weathering * saprolite * ghost-rock * Gash Breccia Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.782, year: 2014 http://popups.ulg.ac.be/1374-8505/index.php?id=4353&file=1&pid=4150

  6. Detailed Ar-40/Ar-39 dating of geologic events associated with the Mantos Blancos copper deposit, northern Chile

    OpenAIRE

    Oliveros, V.; Feraud, G.; L. Aguirre; Ramirez, L.; Fornari, Michel; Palacios, C.; Parada, M.

    2008-01-01

    The Ar-40/Ar-39 geochronological method was applied to date magmatic and hydrothermal alteration events in the Mantos Blancos mining district in the Coastal Cordillera of northern Chile, allowing the distinction of two separate mineralization events. The Late Jurassic Mantos Blancos orebody, hosted in Jurassic volcanic rocks, is a magmatic-hydrothermal breccia-style Cu deposit. Two superimposed mineralization events have been recently proposed. The first event is accompanied by a phyllic hydr...

  7. BIOCHRONOLOGY OF THE PLEISTOCENE MAMMAL FAUNA FROM PONTE GALERIA (ROME) AND REMARKS ON THE MIDDLE GALERIAN FAUNAS

    OpenAIRE

    CARMELO PETRONIO; RAFFAELE SARDELLA

    1999-01-01

    Taking into account the fossil mammal material recently discovered at Cava di Breccia (sands outcropping at Ponte Galeria, Rome), the revised fossils from the area and the updated stratigraphical settings of the Ponte Galeria Formation (Rome), the Authors discuss the biochronology of the Middle Galerian faunal assemblages with a new definition of its Faunal Units.1) The mammal fauna of Isernia in our opinion is strongly conditioned by palaeoenvironmental factors and by human influence. The oc...

  8. Impact of Mercury Mine Activities on Water Resources at Azzaba-North-East of Algeria

    OpenAIRE

    Fadila Alligui; Abdelhak Boutaleb

    2010-01-01

    Problem statement: Mercury mineralization occurred in Azzaba (north-eastern Algeria) as a part of mercurial Numidian belt, consists of numerous of Hg deposits (Koudiat Sma, Mrasma, Guenicha, Fendek, Ismail and Ras Elma). These deposits are hosted in a variety of lithologies including sandstone, limestone, breccias and conglomerate. The ores occur as cinnabar deposits in Ypresian-Lutetian formations. Although the quantity and type of information relating to mining oper...

  9. Origin and age of the earliest Martian crust from meteorite NWA 7533

    Science.gov (United States)

    Humayun, M.; Nemchin, A.; Zanda, B.; Hewins, R. H.; Grange, M.; Kennedy, A.; Lorand, J.-P.; Göpel, C.; Fieni, C.; Pont, S.; Deldicque, D.

    2013-11-01

    The ancient cratered terrain of the southern highlands of Mars is thought to hold clues to the planet's early differentiation, but until now no meteoritic regolith breccias have been recovered from Mars. Here we show that the meteorite Northwest Africa (NWA) 7533 (paired with meteorite NWA 7034) is a polymict breccia consisting of a fine-grained interclast matrix containing clasts of igneous-textured rocks and fine-grained clast-laden impact melt rocks. High abundances of meteoritic siderophiles (for example nickel and iridium) found throughout the rock reach a level in the fine-grained portions equivalent to 5 per cent CI chondritic input, which is comparable to the highest levels found in lunar breccias. Furthermore, analyses of three leucocratic monzonite clasts show a correlation between nickel, iridium and magnesium consistent with differentiation from impact melts. Compositionally, all the fine-grained material is alkalic basalt, chemically identical (except for sulphur, chlorine and zinc) to soils from Gusev crater. Thus, we propose that NWA 7533 is a Martian regolith breccia. It contains zircons for which we measured an age of 4,428 +/- 25 million years, which were later disturbed 1,712 +/- 85 million years ago. This evidence for early crustal differentiation implies that the Martian crust, and its volatile inventory, formed in about the first 100 million years of Martian history, coeval with earliest crust formation on the Moon and the Earth. In addition, incompatible element abundances in clast-laden impact melt rocks and interclast matrix provide a geochemical estimate of the average thickness of the Martian crust (50 kilometres) comparable to that estimated geophysically.

  10. Possible thermal spring deposit in the Arad area, Israel

    Energy Technology Data Exchange (ETDEWEB)

    Issar, A. (Geological Survey of Israel); Eckstein,Y.; Bogoch, R.

    1969-01-01

    A dolomite-chert breccia body, cemented by a hematite-geothite-barite-calcite mineral assemblage was found in the Arad area. This assemblage, plus the presence of anomalous quantities of various elements, particularly molybdenum, and the goethite-hematite relationship, suggest a thermal mineral spring deposit from a hypogene water source. The mineralogy and paragenesis of the deposit are discussed, and a normative analysis is tabulated.

  11. Chemistry of Fullerenes on the Earth and in the Solar System: A 1995 Review

    Science.gov (United States)

    Heymann, D.

    1996-03-01

    Fullerenes C(sub)60 and C(sub)70, the all-carbon molecules with closed-cage structures were discovered in 1990 in shungite from the Kola peninsula. Subsequent discoveries in terrestrial materials include a fulgurite from Colorado, clays and marls from several locations on the Cretaceous-Tertiary boundary, and carbon-rich breccias from the Sudbury impact structure. A search for fullerenes in the carbon-rich materials anthraxolite, shungite, and thucholite, however, failed to find them.

  12. Lunar meteorites:witnesses of the composition and evolution of the Moon

    Institute of Scientific and Technical Information of China (English)

    MIAO Bingkui; CHEN Hongyi; XIA Zhipeng; YAO Jie; XIE Lanfang; NI Wenjun; ZHANG Chuantong

    2014-01-01

    Lunar meteorites are fragments of the Moon that escaped the gravity of the Moon following high-energy impacts by asteroids, subsequently fell to Earth. An inventory of 165 lunar meteorites has been developed since the discovery and identiifcation of the ifrst lunar meteorite, ALHA 81005, in 1979. Although the Apollo samples are much heavier in mass than lunar meteorites, the meteorites are still an important sample supplement for scientiifc research on the composition and history of the Moon. Apart from a small amount of unbrecciated crystalline rocks, the majority of lunar meteorites are breccias that can be classiifed into three groups:highland feldspathic breccia, mare basaltic breccia, and mingled(including lfedspathic and basaltic clasts) breccia. The petrography of lunar rocks suggests that there are a series of rock types of anorthosite, basalt, gabbro, troctolite, norite and KREEP in the Moon. Although KREEP is rare in lunar rocks, KREEP components have been found in the increasing number of lunar meteorites. KREEP provides important information on lunar magmatic evolution, e.g., the VHK KREEP clasts in SaU 169 may represent the pristine lunar magma (urKREEP). Six launching pairs of lunar meteorites have been proposed now, along with ten possible lunar launching sites. In addition, symplectite is often found in lunar basalts, which is a signiifcant record of shock metamorphism on the lunar surface. Furthermore, isotopic ages and noble gases not only provide information on crystallization processes in lunar rocks and the formation of lunar crust, but also provide insight into shock events on the lunar surface.

  13. The Gao-Guenie impact melt breccia—Sampling a rapidly cooled impact melt dike on an H chondrite asteroid?

    Science.gov (United States)

    Schmieder, Martin; Kring, David A.; Swindle, Timothy D.; Bond, Jade C.; Moore, Carleton B.

    2016-06-01

    The Gao-Guenie H5 chondrite that fell on Burkina Faso (March 1960) has portions that were impact-melted on an H chondrite asteroid at ~300 Ma and, through later impact events in space, sent into an Earth-crossing orbit. This article presents a petrographic and electron microprobe analysis of a representative sample of the Gao-Guenie impact melt breccia consisting of a chondritic clast domain, quenched melt in contact with chondritic clasts, and an igneous-textured impact melt domain. Olivine is predominantly Fo80-82. The clast domain contains low-Ca pyroxene. Impact melt-grown pyroxene is commonly zoned from low-Ca pyroxene in cores to pigeonite and augite in rims. Metal-troilite orbs in the impact melt domain measure up to ~2 mm across. The cores of metal orbs in the impact melt domain contain ~7.9 wt% of Ni and are typically surrounded by taenite and Ni-rich troilite. The metallography of metal-troilite droplets suggest a stage I cooling rate of order 10 °C s-1 for the superheated impact melt. The subsolidus stage II cooling rate for the impact melt breccia could not be determined directly, but was presumably fast. An analogy between the Ni rim gradients in metal of the Gao-Guenie impact melt breccia and the impact-melted H6 chondrite Orvinio suggests similar cooling rates, probably on the order of ~5000-40,000 °C yr-1. A simple model of conductive heat transfer shows that the Gao-Guenie impact melt breccia may have formed in a melt injection dike ~0.5-5 m in width, generated during a sizeable impact event on the H chondrite parent asteroid.

  14. Tree-mould caves in Slovakia.

    OpenAIRE

    Gaal Ludovit

    2003-01-01

    Four tube-shaped caves are described in this work, which origined in consequence of weathering the trees. Their length ranges from 5.8 to 17 m. All of them occur in neovolcanic rocks of Middle Slovakia, in epiclastic andesite conglomerates, breccias or in the tuffs. Some other caverns are close to the entrance of this caves, however they are inaccessible for a man. Thin rim of silicates (opal or chalcedony) occurs in some of them.

  15. Gypsum karst in Great Britain

    OpenAIRE

    Cooper A.H.

    1996-01-01

    In Great Britain the most spectacular gypsum karst development is in the Zechstein gypsum (late Permian) mainly in north-eastern England. The Midlands of England also has some karst developed in the Triassic gypsum in the vicinity of Nottingham. Along the north-east coast, south of Sunderland, well-developed palaeokarst, with magnificent breccia pipes, was produced by dissolution of Permian gypsum. In north-west England a small gypsum cave system of phreatic origin has been surveyed and recor...

  16. Black Sea desiccation during the Messinian Salinity Crisis: Fact or fiction?

    OpenAIRE

    Grothe, A.; Sangiorgi, F.; Mulders, Y.; Vasiliev, I.; Brinkhuis, H.; Stoica, M.; Krijgsman, W.; Reichart, G.-J.

    2014-01-01

    The late Miocene Messinian Salinity Crisis (MSC) was an extraordinary geologic event inthe Mediterranean Basin marked by massive salt accumulation and presumably basin desiccationas a consequence of the reduced water exchange with the Atlantic Ocean. The discoveryof a desiccation deposit in the Black Sea, the so-called Pebbly Breccia unit, was used to claimthat the Black Sea also became desiccated during the MSC. Erosional features interpretedfrom seismic profi les of the Black Sea margin, co...

  17. Mineralogy of an unusual CM clast in the Kaidun meteorite

    Science.gov (United States)

    Zolensky, M. E.; Ivanov, A. V.; Yang, S. V.; Barrett, R. A.; Browning, L.

    1994-01-01

    Kaidun is breccia of disparate enstatite and carbonaceous chondrite clasts, and continues to provide real surprises. Many Daidun clasts have been intensely altered by an aqueous fluid, as evidenced by the widespread occurrence of ferromagnesian phyllosilicates and presence of carbonate- and phyllosilicate-filled veins. In this report we describe an unusual CM lithology containing beautiful aggregates of jackstraw pyrrhotites, not previously reported from any meteorite.

  18. Petrography and Geochemistry of Lunar Meteorite Miller Range 13317

    Science.gov (United States)

    Zeigler, R. A.; Korotev, R. L.

    2016-01-01

    Miller Range (MIL) 13317 is a 32-g lunar meteorite collected during the 2013-2014 ANSMET (Antarctic Search for Meteorites) field season. It was initially described as having 25% black fusion crust covering a light- to dark-grey matrix, with numerous clasts ranging in size up to 1 cm; it was tenta-tively classified as a lunar anorthositic breccia. Here we present the petrography and geochemistry of MIL 13317, and examine possible pairing relationships with previously described lunar meteorites.

  19. The Regolith of 4 Vesta - Inferences from Howardites

    Science.gov (United States)

    Mittlefehldt, D. W.; Herrin, J. S.; Cartwright, J. A.

    2011-01-01

    Asteroid 4 Vesta is quite likely the parent asteroid of the howardite, eucrite and diogenite meteorites - the HED clan. Eucrites and diogenites are the products of igneous processes; the former are basaltic composition rocks from flows, and shallow and deep intrusive bodies, whilst the latter are cumulate orthopyroxenites thought to have formed deep in the crust. Impact processes have excavated these materials and mixed them into a suite of polymict breccias. Howardites are polymict breccias composed mostly of clasts and mineral fragments of eucritic and diogenitic parentage, with neither end-member comprising more than 90% of the rock. Early work interpreted howardites as representing the lithified regolith of their parent asteroid. Recently, howardites have been divided into two subtypes; fragmental howardites, being a type of non-regolithic polymict breccia, and regolithic howardites, being lithified remnants of the active regolith of 4 Vesta. We are in the thralls of a collaborative investigation of the record of impact mixing contained within howardites, which includes studies of their mineralogy, petrology, bulk rock compositions, and bulk rock and clast noble gas contents. One goal of our investigation is to test the hypothesis that some howardites represent breccias formed from an ancient, well-mixed regolith on Vesta. Another is to use our results to further understand regolith processing on differentiated asteroids as compared to what has been learned from the Moon. We have made petrographic observations and electron microprobe analyses on 21 howardites and 3 polymict eucrites. We have done bulk rock analyses using X-ray fluorescence spectrometry and are completing inductively coupled plasma mass spectrometry analyses. Here, we discuss our petrologic and bulk compositional results in the context of regolith formation. Companion presentations describe the noble gas results and compositional studies of low-Ca pyroxene clasts.

  20. Stratigraphy, artefact industries and hominid associations for Sterkfontein, member 5.

    Science.gov (United States)

    Kuman, K; Clarke, R J

    2000-06-01

    A revised stratigraphy for the early hominid site of Sterkfontein (Gauteng Province, South Africa) reveals a complex distribution of infills in the main excavation area between 2.8 and 1.4 m.y.a, as well as deposits dating to the mid to late Pleistocene. New research now shows that the Member 4 australopithecine breccia (2.8-2.6 Ma) extends further west than was previously thought, while a late phase of Member 4 is recognized in a southern area. The artefact-bearing breccias were defined sedimentologically as Member 5, but one supposed part of these younger breccias, the StW 53 infill, lacks in situ stone tools, although it does appear to post-date 2.6 Ma when artefacts first appear in the archaeological record. The StW 53 hominid, previously referred to Homo habilis, is here argued to be Australopithecus. The first artefact-bearing breccia of Member 5 is the Oldowan Infill, estimated at 2-1.7 Ma. It occupies a restricted distribution in Member 5 east and contains an expedient, flake-based tool industry associated with a few fossils of Paranthropos robustus. An enlarged cave opening subsequently admitted one or more Early Acheulean infills associated in Member 5 west with Homo ergaster. The artefacts attest to a larger site accumulation between ca. 1.7 and 1.4 Ma, with more intensive use of quartzite over quartz and a subtle but important shift to large flakes and heavier-duty tools. The available information on palaeoenvironments is summarized, showing an overall change from tropical to sub-tropical gallery forest, forest fringe and woodland conditions in Member 4 to more open woodland and grassland habitats in the later units, but with suggestions of a wet localized topography in the Paranthropus -bearing Oldowan Infill. PMID:10835264

  1. Paleokarst Evaluation in the Upper Albian Calcareous Platforms in Mexico, Guatemala and Honduras

    OpenAIRE

    Carrasco-Velázquez B.E.

    2011-01-01

    This paper presents the evaluation in México, Guatemala and Honduras of theUpper Albian platform carbonate rocks that were exposed to subaerial conditions by the falling of the sea level, exposing the rocks to the physical, chemical and temperature phenomena allowing for some type of karst formation. There is a methodology for the identification of paleokarsts by the petrology, fabrics, geometry and stratigraphy of the breccias. Only at Dengandho in the Actopan Platform there are the evidence...

  2. Composition, Microstructures, and Petrophysics of the Mozumi Fault, Japan: In Situ Analyses of Fault Zone Properties and Structure in Sedimentary Rocks from Shallow Crustal Levels

    OpenAIRE

    Isaacs, Angela J.; Evans, James P; Kolesar, Peter T.; Nohara, Tsuyoshi

    2008-01-01

    [1] We characterize the chemical, microstructural, and geophysical properties of fault-related rock samples from the 80–100 m wide Mozumi fault zone, north central Honshu, Japan. The fault is exposed in a research tunnel 300–400 m below the ground, and we combine geological data with borehole geophysical logs to determine the elastic and seismic properties of the fault zone. Detailed mapping within the tunnel reveals that the fault zone consists of two zones of breccia to foliated cataclasi...

  3. Multistage dolomitization in the Acungui Group metacarbonate rocks, Proterozoic of Parana state, Brazil; Dolomitizacao multifasica em reochas metacarbonaticas do Grupo Acungui, Proterozoico do estado do Parana, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Pinto-Coelho, Cristina Valle; Reis Neto, Jose Manoel dos [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Geologia], e-mail: cristinavpc@ufpr.br, e-mail: jmreis@ufpr.br, e-mail: salla82@gmail.com; Eeva, Salla Talvikki [PETROBRAS (Brazil). E e P. Gerencia de Estratigrafia e Sedimentologia

    2007-11-15

    The carbonate rocks of Rio Bonito Quarry, at the state of Parana, are represented by metamarls, mylonized rocks, calcite and dolomite marbles and dolomite breccias, which were formed in several burial stages. The first dolomitization process which affected the marbles had its origin in a burial environment. The process occurred during Mesoproterozoic, where a precedent calcitic rock had its matrix replaced by fine to medium sized dolomite crystals with cloudy aspect, and where styolites and fractures formed the principal conduits for the circulation of Mg-rich solutions. The dolomite breccia were formed during the Brazilian Cycle (Neoproterozoic), in conditions of hydraulic fracturing, originated by devolatilization which occurred during the metamorphism of green schist facies. The second dolomitization process, caused the formation of Fe-rich microcrystalline dolomite (Dp1), originated through a fluid at chemical disequilibrium with the fluid responsible for the former dolomitization. In the Paleozoic occurred a new phase of dolomitization, developing the Dp2-type dolomite, as the consequence of reactivation of deep crustal faults or igneous intrusions (dykes of microgabbro). This dolomite is constituted by saddle dolomite, with nonplanar and coarse crystals, strong undulate extinction, which fills fractures in breccias as well as in dolomitic marbles. Superficial processes at the Paleogene, related to the topographic evolution, promoted the percolation of low-temperature fluids, occasioning the process of dedolomitization via dissolution and posterior filling of cavities. The process of dedolomitization occurred in dolomitic breccia with precipitation of late calcite, which filled the cavities, associated to dolomite of generation Dp2. Quartz completes the final phase of the void-filling process.(author)

  4. Magnetic mineral characterization close to the Yingxiu-Beichuan fault surface rupture zone of the Wenchuan earthquake (Mw 7.9, 2008) and its implication for earthquake slip processes

    Science.gov (United States)

    Liu, Dongliang; Li, Haibing; Lee, Teh-Quei; Sun, Zhiming; Liu, Jiang; Han, Liang; Chevalier, Marie-Luce

    2016-01-01

    The 2008 Mw 7.9 Wenchuan Earthquake produced two major rupture zones: one in the Yingxiu-Beichuan fault zone (YBF) and another in the Anxian-Guanxian fault zone (AGF). A shallow trench was dug in Bajiaomiao village, Dujiangyan, Sichuan Province, which experienced a ∼4.3 m vertical offset during this large earthquake. The hanging wall of the YBF in this trench includes fault gouge and breccia. Optical microscope observations and X-ray diffraction (XRD) measurements show obvious differences between the fault gouge and breccia. Moreover, rock magnetism measurements were collected and include mass magnetic susceptibility (MS), Isothermal Remnant Magnetization (IRM), Saturation Isothermal Remnant Magnetization (SIRM), high-temperature thermo-magnetism (K-T) and magnetic hysteresis loops. Several cm-thick magnetic mineral anomalies are observed close to the Wenchuan Earthquake surface rupture zone of the YBF. Magnetite and Fe-sulfide are the main magnetic carrier materials for the fault rocks close to the surface rupture zone, including 3 cm-thick fault gouge and 3 cm-thick fault breccia, while the other fault breccia, further from the surface rupture zone, contains the paramagnetic minerals. The possible magnetic change is attributed to newly-formed magnetite from paramagnetic minerals at high temperatures (>500 °C) during the large earthquake, implying that the YBF has ever experienced high-temperature thermal pressurization earthquake slip dynamics. Moreover, the YBF has also experienced high-temperature frictional melting earthquake slip dynamics, constrained by the multiple vein pseudotachylite. These high-temperature earthquake slip processes may be responsible for the high dip angle thrust characteristic of the YBF.

  5. The Gravina Sequence: Remnants of a Mid-Mesozoic oceanic arc in southern southeast Alaska

    OpenAIRE

    Rubin, Charles M.; Saleeby, Jason B.

    1991-01-01

    Fragments of Upper Jurassic to Lower Cretaceous volcanic and basinal strata constitute the Gravina belt in southeast Alaska. In the Ketchikan area the Gravina belt is made up of two lithotectonic units. The lower unit consists of coarse marine pyroclastic and volcaniclastic strata, mafic flows, breccia, and fine-grained tuff which are locally intruded by hypabyssal bodies of diorite and quartz diorite. The volcanic rocks are characterized by tholeiitic arc basalts, lack felsic volcanic strata...

  6. Geology, alteration, mineralization, petrogenesis, geochronology, geochemistry and airborne geophysics of Kuh Shah prospecting area, SW Birjand

    OpenAIRE

    Maryam Abdi; Mohammad Hassan Karimpour

    2012-01-01

    The Kuh Shah prospecting area is located in Tertiary volcano-plutonic belt of the Lut Block. More than seventeen subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, were identified in the study area. The intrusions are related to hydrothermal alteration zones and contain argillic, propylitic, advanced argillic, silicified, quartz-sericite-pyrite, gossan and hydrothermal breccia which overprinted to each other and are accompanied by weathering which made it c...

  7. Apollo 14 inverted pigeonites - Possible samples of lunar plutonic rocks.

    Science.gov (United States)

    Papike, J. J.; Bence, A. E.

    1972-01-01

    Analysis of 'inverted pigeonites' found in Apollo 14 samples 14082 and 14083 (a polymict breccia, the 'white rock') by a combination of optical, electron probe, and single-crystal X-ray diffraction techniques. These 'inverted pigeonites' are regarded as samples of plutonic rocks that have been blasted out of the Imbrium Basin. It is also concluded that lunar pigeonites will invert to orthopyroxenes, given sufficiently slow cooling histories even in very anhydrous environments.

  8. Analisis stratigrafi awal kegiatan Gunung Api Gajahdangak di daerah Bulu, Sukoharjo; Implikasinya terhadap stratigrafi batuan gunung api di Pegunungan Selatan, Jawa Tengah

    Directory of Open Access Journals (Sweden)

    Hill Gendoet Hartono

    2014-06-01

    Full Text Available http://dx.doi.org/10.17014/ijog.vol4no3.20091Generally, Tertiary volcanisms in the Southern Mountains, Central Jawa were started with the formation of pillow lavas having basalt to basaltic andesite in composition. This initial stage volcanism developed into a  construction period of composite volcanoes that consist of alternating basaltic to andesitic lava flows, breccias, and tuffs. The construction period could be followed by a destructive phase, producing pumice-rich pyroclastic breccias, lapillistones, and tuffs of high silica andesite to dacite, or even rhyolite in composition. A stratigraphic measuring section at Bulu area, Sukoharjo Regency, presents an alternat- ing fine-grained andesitic volcaniclastic material and some limestones, with the total thickness is 143.33 m. The thickness of bedded volcaniclastic material tends to be thickening upward from 35 m until 90 m. The grain size of the volcaniclastic material also tends to be coarsening upward from clay size through silt and fine sand to coarse sand and granules. Paleontological analysis on fossils contained in the lime- stone gives an age of Early Miocene (N7 - N9. The volcaniclastic rocks is conformably overlain by the Mandalika Formation, comprising alternating andesitic breccias, lavas, and tuffs. These data imply that the fine-grained volcaniclastic material is an initial product of the construction period of Gajahdangak Volcano in the area, that formed the Mandalika Formation. This Formation is overlain by the Semilir Formation, composed of pumice-rich pyroclastic breccias and tuffs with dacitic composition. This as- sociated volcanic rock reflects a product of a caldera explosion or a destructive phase. Based on the characteristics of lithology of volcanic products from the initial stage, to a construction and destruction period, and compiled age data, the Southern Mountains represent formal volcanic rock units that are able to be divided into many formations.  

  9. Influence of Lithology and Slope Gradient to Infiltration of the Mount Malabar, West Java

    Science.gov (United States)

    Pratama, A.; Irawan, D. E.; Susanto, A.; Ardi, R. D. W.

    2016-01-01

    Volcano is an area which serves as a catchment area for the lowlands. Ability of rock or weathered-soil to absorb the rain water depends on several things, such as lithology and large of slope. Different lithology has different characteristics, including in terms of porosity which is directly related to the ability of rock to store water. Characteristics of lithology in volcanic area can change rapidly, both vertically and laterally. Large of slope in volcanic area that change significantly also can affect the infiltration rate (the seepage of rain) in rock or weathered-soil. Therefore, the influence of lithology and large of slope to the infiltration rate should be proven to predict the infiltration zone in volcanic area. Observations has been conducted on the eastern slopes of Mount Malabar with an area 78 km2, at coordinates 7003'28.04" LS - 7010'32.05" LS and 107038'37.64" BT - 107041'50.6" BT. The infiltration rate observed on the weathered-soil using simple single infiltrometer made of PVC pipe 50 cm long, on March-April 2015. The measurement is carried out at several points where the weathered-rock result has been known, as much two times for different slope in each point. 26 measurement points have been obtained from different slopes and weathered-soil of different five-lithology. The results showed that the infiltration rate proportional to the percentage of rock porosity and large of slope. Infiltration rate sequence from the smallest to the greatest are weathered-soil andesites, basaltic andesite, laharic breccias, alteration of dacite, and pyroclastic breccias. The greatest infiltration rate obtained is 10.11 cm/minute in pyroclastic breccia with 25o slope, while the smallest is 0.0437 cm/minute in pyroclastic breccias with 4o slope.

  10. Mineralogy of the Asuka 87 and 88 eucrites and crustal evolution of the HED parent body

    OpenAIRE

    Takeda,Hiroshi/Ishii,Teruaki/Arai,Tomoko/Miyamoto,Masamichi

    1997-01-01

    Mineralogical study of three apparently crystalline eucrites, Asuka (A)-87272,A-881388 and A-881394 revealed that their textures are not primary crystallization products from a magma. A-87272 is a monomict breccia, but the finegrained matrix is recrystallized to a granulitic texture with fine, rounded pyroxene crystals set in a plagioclase matrix. Large fragments of pyroxene are inverted to orthopyroxene with coarse exsolution lamellae on (001) and fine ones on (100). A-881388 contains a larg...

  11. The Composition of the Prebasin Crust in the Central Highlands of the Moon

    Science.gov (United States)

    Korotev, R. L.

    1996-03-01

    The Apollo 16 regolith consists of a large amount of material derived from the prebasin crust, i.e., (1) plutonic ferroan anorthosite and brecciated derivatives (>90% plagioclase), (2) a variety of noritic anor-thosites (plutonic, feldspathic fragmental breccias [FFBs], granulitic breccias [GrBs], feldspathic impact-melt breccias), and (3) a minor amount of gabbronorites of highland affinity. However, the site is sufficiently close to nearside mare basins that the regolith also contains a substantial fraction of basin ejecta as well as some mare-derived materials (MDMs) delivered to the site by volcanism and impacts since filling of the basins with mare basalt. These syn- and postbasin products include (4) mafic impact-melt breccias [MIMBs, i.e., "LKFM" and "VHA"], (5) MDMS, i.e., glasses and some crystalline mare basalt, and (6) meteoritic material (largely from micrometeorites) accumulated in the regolith since basin for-ma-tion ~3.9 Ga ago. The MIMBs, which are rich in incompatible trace elements, were formed during the time of basin formation by impacts large enough to penetrate the outer feldspathic crust and melt mafic underlying material, although not all of the several known varieties at the Apollo 16 site may actually have been formed by impacts that produced basins. The Central Highlands, as sampled by the Apollo 16 mission, differs from highlands regions distant from mare basins in its high abundance of mafic syn- and postbasin material. For example, some feldspathic lunar meteorites (ALHA81005, Yamato-86032, MAC 88104/5, QUE93069) contain virtually no MDMSor MIMBs.

  12. ENGINEERING GEOLOGICAL CHARACTERISTICS OF THE ROAD SOLIN - KLIS (DALMATIA, CROATIA

    Directory of Open Access Journals (Sweden)

    Slobodan Šestanović

    1993-12-01

    Full Text Available The research, that has been done both on the »intact« terrain and on the opened cuts and discontinuities, and which has been carried on in the basic caves of the object, as well as in the tunnels; has verified the engineering geological and basic tectonic characteristics of Senonian limestones, Eocene flysch, the Promina breccias and breccia-conglomerates, as well as Oligocene poorly sorted breccias, on the route of semi-highway Solin-Klis (Dalmatia, Croatia. The lab analyses, of the great number of the rock samples, have brought out the parametres of their basic physical and mechanical features within a particular engineering geological unit. The results, thus obtained, have been compared to the qualities of the rock structure block as a whole, and had been previously evaluated by applying RMR-classification of the rocks, and the results of the measured velocities of the longitudinal waves. It has been pointed out that similar procedure may be applied in the publication of General Engineering Geological Map of the Republic of Croatia (the paper is published in Croatian.

  13. Anatomy of the Chesapeake Bay impact structure revealed by seismic imaging, Delmarva Peninsula, Virginia, USA

    Science.gov (United States)

    Catchings, R.D.; Powars, D.S.; Gohn, G.S.; Horton, J.W., Jr.; Goldman, M.R.; Hole, J.A.

    2008-01-01

    A 30-km-long, radial seismic reflection and refraction survey completed across the northern part of the late Eocene Chesapeake Bay impact structure (CBIS) on the Delmarva Peninsula, Virginia, USA, confirms that the CBIS is a complex central-peak crater. We used a tomographic P wave velocity model and low-fold reflection images, constrained by data from two deep boreholes located on the profile, to interpret the structure and composition of the upper 5 km of crust. The seismic images exhibit well-defined structural features, including (with increasing radial distance) a collapsed central uplift, a breccia-filled moat, and a collapsed transient-crater margin (which collectively constitute a ???40-km-wide collapsed transient crater), and a shallowly deformed annular trough. These seismic images are the first to resolve the deep structure of the crater (>1 km) and the boundaries between the central uplift, moat, and annular trough. Several distinct seismic signatures distinguish breccia units from each other and from more coherent crystalline rocks below the central uplift, moat, and annular trough. Within the moat, breccia extends to a minimum depth of 1.5 km or a maximum of 3.5 km, depending upon the interpretation of the deepest layered materials. The images show ???350 to 500 m of postimpact sediments above the impactites. The imaged structure of the CBIS indicates a complex sequence of event during the cratering process that will provide new constraints for numerical modeling. Copyright 2008 by the American Geophysical Union.

  14. Petrologic comparisons of Cayley and Descartes on the basis of Apollo 16 soils from stations 4 and 11

    Science.gov (United States)

    Basu, A.; Mckay, D. S.

    1984-01-01

    Petrologic aspects of the Cayley and Descartes formations are reviewed in the light of new data on Apollo 16 soils. Specific comparison of the modal abundances of lithic fragments in drive tube sample 64001/2 from the slopes of Stone Mountain (station 4) and in soil 67941 from the North Ray Crater rim (station 11) shows that melt rocks, especially poikilitic rocks, are more abundant at station 4 than at station 11; the reverse is true for fragmental breccias. Such lithologic differences suggest that stations 4 and 11 do not belong to the same geologic formation. Metamorphosed breccias are pervasive in both the formations and may represent a local component that has been reworked and diluted as fresh materials were added. Lithologic compositions inferred from the study of soil samples are different from lithologic compositions inferred from the study of rake samples or breccia clasts. This difference may be related to a mixing of material of different grain size distributions. The petrology of soils at the Apollo 16 site may not accurately reflect original material associated with either the Descartes or the Cayley formation because of extensive mixing with local material.

  15. Bohemian circular structure, Czechoslovakia: Search for the impact evidence

    Science.gov (United States)

    Rajlich, Petr

    1992-01-01

    Test of the impact hypothesis for the origin of the circular, 260-km-diameter structure of the Bohemian Massif led to the discovery of glasses and breccias in the Upper Proterozoic sequence that can be compared to autogeneous breccias of larger craters. The black recrystallized glass contains small exsolution crystals of albite-oligoclase and biotite, regularly dispersed in the matrix recrystallized to quartz. The occurrence of these rocks is limited to a 1-sq-km area. It is directly underlain by the breccia of the pelitic and silty rocks cemented by the melted matrix, found on several tens of square kilometers. The melt has the same chemistry as rock fragments in major and in trace elements. It is slightly impoverished in water. The proportion of melted rocks to fragments varies from 1:5 to 10:1. The mineralogy of melt viens is the function of later, mostly contact metamorphism. On the contact of granitic plutons it abounds on sillimanite, cordierite, and small bullets of ilmenite. Immediately on the contact with syenodiorites it contains garnets. The metamorphism of the impact rock melt seems the most probable explanation of the mineralogy and the dry total fusion of rocks accompanied by the strong fragmentation. Other aspects of this investigation are discussed.

  16. Utilization of rocks and ectomycorrhizal fungi to promote growth of eucalypt

    Directory of Open Access Journals (Sweden)

    Luciano Alves

    2010-10-01

    Full Text Available The utilization of rocks as fertilizers is limited by their low solubility. However, solubilization may be achieved by some micro-organisms, such as ectomycorrhizal fungi (ECMf. The aim of this study was to evaluate the potential of seven isolates of ECMf to solubilize two rocks, alkaline breccia and granite, and to liberate potassium and phosphorus for Eucalyptus dunnii seedlings under greenhouse conditions. Fungal inoculants were produced in a peat-vermiculite-liquid medium mixture and added to the planting substrate at 10 %. Rocks were ground up and added at 0.500 mg and 16.0 mg per plant, as a source of phosphorus and potassium, respectively. Other nutrients were added and E. dunnii seeds were sown. Control plants, non-inoculated, were fertilized with the same amount of phosphorus and potassium using soluble forms. After 90 days, the plant height, shoot dry weight, root length, phosphorus and potassium contents, and mycorrhizal colonization were evaluated. Alkaline breccia was more efficient than granite as a source of phosphorus and potassium for the plants, and may be an alternative to conventional fertilizers. Isolates UFSC-Pt22 (Pisolithus sp. and UFSC-Pt186 (Pisolithus microcarpus were the most efficient in promoting plant growth, mainly when combined with alkaline breccia to replace potassium and phosphorus fertilizers, respectively.

  17. Study on the origin of the Hongshan brecciated copper deposit in Huichang County,Jiangxi Province, China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Hongshan copper deposit is a typical cryptoexplosive breccia-type deposit, which occurs in a Metamorphic rock series of the Mesoproterozoic Taoxiyuan Formation. Orebodies are distributed inside and outside porphyry-cryptoexplosive breccia pipes. The isotope geochemistry of the deposit is consistent with the origin of porphyry breccia: the δ18OH2O values ranging from 1.2‰ to 6.1‰ and the δ34S values varying from 0 to 2.5‰.206Pb/204Pb,207Pb/204Pb and 208Pb/204Pb ratios of pyrite, which coexists with ore minerals, indicate it was derived from the orogenic belt. Thermodynamic analysis indicates that the main metals were deposited largely as a result of the decreasing of proton concentrations associated with H2S and CO2 exsolution during exploslon and temperature dropping.Based on K-Ar dating of quartz coexisting with ore minerals,the age of mineralization was estimated to be 97.1-98.8 Ma,which suggests that mineralization occurred between the Early and Late Cretaceous. According to the relevant informtion obtained,a diagenetic and metallogenic pattern in the area has been presented in this paper.

  18. Insights on Structural, Petrographical, Mineralogical and Geochemical Approach on the Grahamstown Kaolin Deposit Genesis in the Eastern Cape, South Africa

    Directory of Open Access Journals (Sweden)

    Kakaba Madi

    2013-04-01

    Full Text Available The town of Grahamstown is known on the geological and mineralogical point of view mainly because of its kaolin deposit, which derived from the intense weathering of the Dwyka tillite of the Karoo Supergroup. The weathering is favoured by the occurrence of brittle structures and breccias of granites that contains considerable amount of feldspar. The purpose of this study is to examine the importance of structural control in the weathering process leading to the formation of kaolin, to check the petrographical data by comparing breccias found in the fresh tillite and those in the kaolin, to highlight the mineralogical composition in some samples. The methods used in this study include: a comprehensive literature review, field observations, fault and fracture measurements to produce a general orientation, microscopic study, XRD and XRF analysis. Muscovite, albite, orthoclase, plagioclase, smectite, illite and quartz are some of the minerals present; smectization and illitization precede kaolinization in the Grahamstown area from k-feldspar and feldspar by leaching of elements such as K, Na and Ca and concentration of Al that later combines with Si to produce kaolin. A fresh tillite has higher intensity in peak diffraction analysis than a less and more weathered rock at a certain angle 2 theta. It is concluded that the primary source rock that is the parent rock in the genesis of kaolin is the Dwyka tillite, this tillite comprises breccias of granite and quartzite having microfractures that contribute to the alteration of feldspathic materials into kaolin.

  19. Karst in evaporites in southeastern New Mexico

    International Nuclear Information System (INIS)

    Permian evaporites in southeastern New Mexico include gypsum, anhydrite, and salt, which are subject to both blanket and local, selective dissolution. Dissolution has produced many hundreds of individual karst features including collapse sinks, karst valleys, blind valleys, karst plains, caves, and breccia pipes. Dissolution began within some formations during Permian time and has been intermittent but continual ever since. Karst features other than blanket deposits of breccia are not preserved from the early episodes of dissolution, but some karst features preserved today - such as breccia pipes - are remnants of karst activity that was active at least as early as mid-Pleistocene time. Rainfall was much more abundant during Late Pleistocene time, and many features visible today may have been formed then. The drainage history of the Pecos River is related to extensive karstification of the Pecos Valley during mid-Pleistocene time. Large-scale stream piracy and dissolution of salt in the subsurface resulted in major shifts and excavations in the channel. In spite of intensive groundwater studies that have been carried out in the region, major problems in near-surface evaporite karst remain to be solved. Among these are determination of recharge areas and time of recharge. 109 refs., 31 figs., 1 tab

  20. Otavipithecus namibiensis, first Miocene hominoid from southern Africa.

    Science.gov (United States)

    Conroy, G C; Pickford, M; Senut, B; Van Couvering, J; Mein, P

    1992-03-12

    We report here the discovery of a Miocene hominoid from Berg Aukas, Namibia, the first known from the African continent south of equatorial East Africa. This represents a major range extension of Miocene Hominoidea in Africa to latitude 20 degrees S. The holotype, a right mandibular corpus preserving the crowns of the P4-M3, partial crown and root of the P3, partial root of the canine, alveoli for all four incisors, and partial alveolus for the left canine, was found during paleontological explorations of karst-fill breccias in the Otavi region of northern Namibia. The mandible has unique characteristics that differentiate it from other middle Miocene hominoids of Africa and Eurasia and represents the only fossil evidence documenting a pre-australopithecine stage of hominoid evolution in southern Africa. Faunal analyses indicate that the breccia block containing the specimen accumulated during the latter part of the middle Miocene, about 13 +/- 1 Myr. Fauna from other breccia blocks at Berg Aukas are of diverse ages, including the earlier part of the middle Miocene, the upper Miocene, Plio-Pleistocene and Holocene. PMID:1545864

  1. New oil source rocks cut in Greek Ionian basin

    Energy Technology Data Exchange (ETDEWEB)

    Karakitsios, V. [Univ. of Athens (Greece); Rigakis, N. [Public Petroleum Corp., Athens (Greece)

    1996-02-12

    The Ionian zone of Northwest Greece (Epirus region) constitutes part of the most external zones of the Hellenides (Paxos zone, Ionian zone, Gavrovo Tripolitza zone). The rocks of the Ionian zone range from Triassic evaporites and associated breccias through a varied series of Jurassic through Upper Eocene carbonates and lesser cherts and shales followed by Oligocene flysch. The surface occurrences of petroleum in the Ionian zone are mainly attributed to Toarcian Lower Posidonia beds source rocks and lesser to late Callovian-Tithonian Upper Posidonia beds and to the Albian-Cenomanian Upper Siliceous zone or Vigla shales of the Vigla limestones. Oil that could not be attributed to the above source rocks is believed to have an origin from Triassic formations that contain potential source rocks in Albania and Italy. However, several samples of the shales of Triassic breccias from outcrops and drillholes were analyzed in the past, but the analytical results were not so promising since their hydrocarbon potential was low. In this article, the authors will present their analytical results of the Ioannina-1 well, where for the first time they identified some very rich source beds in the Triassic breccias formation of Northwest Greece.

  2. Butalón igneous rocks, Neuquén, Argentina: Age, stratigraphic relationships and geochemical features

    Science.gov (United States)

    Casé, A. M.; López-Escobar, L.; Danieli, J. C.; Schalamuk, A.

    2008-09-01

    Three main groups of igneous rocks of different age are recognized in the Butalón area, including volcanic rocks of the Choiyoi Group (Permian-Triassic), stocks and dikes of the Granodiorita Varvarcó (Upper Cretaceous-Paleocene) and stocks and dikes of the Tonalita Butalón (Paleocene-Eocene?). The Choiyoi Group consists of ignimbrites, breccias, tuffs and silicic lavas. Most are subalkaline and four groups can be distinguished on the basis of their trace element patterns. Most samples are enriched in Ba, but depleted in Nb, Sr, P, Ti and Eu. The subvolcanic rocks of the Granodiorita Varvarcó and Tonalita Butalón are mainly calc-alkaline, metaluminous to peraluminous, with low to medium potassium contents. They have similar subparallel REE and multielement patterns with low La/Yb and Eu/Eu ∗ ratios. These patterns mimic those observed in Pleistocene-Holocene volcanic rocks, of similar SiO 2 content, from the CSVZ of the Andes. They are depleted in Nb and Ti, have normal to low P, and are enriched in Sr and Zr. Hornfels-skarn type hydrothermal alteration is produced by Tonalita Butalón in the adjacent igneous rocks. Magmatic-hydrothermal breccias are developed on top of some of the stocks. While some of the breccias exhibit Mo anomalies, Au and Ag anomalies are present in the Choiyoi Group.

  3. Hydrothermal Processes and Mobile Element Transport in Martian Impact Craters - Evidence from Terrestrial Analogue Craters

    Science.gov (United States)

    Newsom, H. E.; Nelson, M. J.; Shearer, C. K.; Dressler, B. L.

    2005-01-01

    Hydrothermal alteration and chemical transport involving impact craters probably occurred on Mars throughout its history. Our studies of alteration products and mobile element transport in ejecta blanket and drill core samples from impact craters show that these processes may have contributed to the surface composition of Mars. Recent work on the Chicxulub Yaxcopoil-1 drill core has provided important information on the relative mobility of many elements that may be relevant to Mars. The Chicxulub impact structure in the Yucatan Peninsula of Mexico and offshore in the Gulf of Mexico is one of the largest impact craters identified on the Earth, has a diameter of 180-200 km, and is associated with the mass extinctions at the K/T boundary. The Yax-1 hole was drilled in 2001 and 2002 on the Yaxcopoil hacienda near Merida on the Yucatan Peninsula. Yax-1 is located just outside of the transient cavity, which explains some of the unusual characteristics of the core stratigraphy. No typical impact melt sheet was encountered in the hole and most of the Yax-1 impactites are breccias. In particular, the impact melt and breccias are only 100 m thick which is surprising taking into account the considerably thicker breccia accumulations towards the center of the structure and farther outside the transient crater encountered by other drill holes.

  4. Stratigraphic analysis of the Sterkfontein StW 573 Australopithecus skeleton and implications for its age.

    Science.gov (United States)

    Bruxelles, Laurent; Clarke, Ronald J; Maire, Richard; Ortega, Richard; Stratford, Dominic

    2014-05-01

    StW 573, Little Foot, is the most complete Australopithecus skeleton yet discovered, with many of its bones found in their correct anatomical position. Since the discovery of the in situ skeleton in the Silberberg Grotto in 1997, several teams have attempted to date the fossil. This appeared a simple process because several flowstones are inter-bedded in the breccia above and below StW 573. Dating of these flowstones, using U-Pb (uranium-lead) isotope decay techniques, gave younger results than expected from the fauna and stratigraphic position, around 2.2 Ma (millions of years). Our recent stratigraphic, micromorphological and geochemical studies revealed that the stratigraphy is much more complicated than was previously thought, with localized post-depositional processes leading to the creation of voids within the breccia around the skeleton. These voids were then filled by multiple generations of flowstone growth. The research we present here demonstrates that the proposed dates based on the flowstone deposition can give only a minimum age for StW 573 and that the flowstone formation came after, and probably long after, the breccia deposition. If one takes account of the long evolution of these karst fillings, StW 573 appears to be significantly older than 2.2 Ma. PMID:24698198

  5. High crustal diversity preserved in the lunar meteorite Mount DeWitt 12007 (Victoria Land, Antarctica)

    Science.gov (United States)

    Collareta, Alberto; D'Orazio, Massimo; Gemelli, Maurizio; Pack, Andreas; Folco, Luigi

    2016-02-01

    The meteorite Mount DeWitt (DEW) 12007 is a polymict regolith breccia mainly consisting of glassy impact-melt breccia particles, gabbroic clasts, feldspathic clasts, impact and volcanic glass beads, basaltic clasts, and mingled breccia clasts embedded in a matrix dominated by fine-grained crystals; vesicular glassy veins and rare agglutinates are also present. Main minerals are plagioclase (typically An>85) and clinopyroxene (pigeonites and augites, sometimes interspersed). The presence of tranquillityite, coupled with the petrophysical data, the O-isotope data (Δ17O = -0.075), and the FeOtot/MnO ratios in olivine (91), pyroxene (65), and bulk rock (77) indicate a lunar origin for DEW 12007. Impactites consist of Al-rich impact-melt splashes and plagioclase-rich meta-melt clasts. The volcanic products belong to the very low titanium (VLT) or low titanium (LT) suites; an unusual subophitic fragment could be cryptomare-related. Gabbroic clasts could represent part of a shallow intrusion within a volcanic complex with prevailing VLT affinity. DEW 12007 has a mingled bulk composition with relatively high incompatible element abundances and shows a high crustal diversity comprising clasts from the Moon's major terranes and rare lithologies. First-order petrographic and chemical features suggest that DEW 12007 could be launch-paired with other meteorites including Y 793274/981031, QUE 94281, EET 87521/96008, and NWA 4884.

  6. A submarine welded ignimbrite-crystal-rich sandstone facies association in the Cambrian Tyndall Group, western Tasmania, Australia

    Science.gov (United States)

    White, Matthew J.; McPhie, Jocelyn

    1997-04-01

    Three occurrences of rhyolitic welded ignimbrite are intercalated within a submarine, below-storm-wave-base sedimentary succession in the Cambrian Tyndall Group, Mount Read Volcanics, western Tasmania. These occurrences are closely associated with very thick crystal-rich sandstone facies that is present at this stratigraphic level throughout the Tyndall Group. This facies is interpreted to comprise deposits from syn-eruptive, crystal-rich, submarine sediment gravity flows that were generated by interaction of subaerial pyroclastic flows with seawater. Removal of fine ash and pumice from the submarine flows by hydraulic sorting and flotation resulted in marked crystal enrichment in the deposits. Rapid, essentially syn-eruptive aggradation of crystal-rich sand led to temporary shoaling so that in some cases, subsequent pyroclastic flows deposited welded ignimbrite in shallow marine or possibly subaerial settings (e.g., Zig Zag Hill welded ignimbrite). Breccia units composed of welded ignimbrite clasts and crystal-rich matrix (e.g., Comstock and Anthony Road ignimbrite breccias) imply that some welded ignimbrite was submerged, providing clasts to syn-eruptive, submarine, crystal-rich sediment gravity flows. One example of welded ignimbrite (Cradle Mountain Link Road) may have been deposited in an entirely below-storm-wave-base environment. The distinctive facies association of welded ignimbrite, crystal-rich sandstone and ignimbrite-clast breccia in the Tyndall Group exemplifies the submarine record of a major rhyolitic explosive eruption in the source volcanic terrane.

  7. Exsolution and shock microstructures of igneous pyroxene clasts in the Northwest Africa 7533 Martian meteorite

    Science.gov (United States)

    Leroux, Hugues; Jacob, Damien; Marinova, Maya; Hewins, Roger H.; Zanda, Brigitte; Pont, Sylvain; Lorand, Jean-Pierre; Humayun, Munir

    2016-05-01

    Northwest Africa (NWA) 7533 is a Martian regolith breccia. This meteorite (and its pairings) offers a good opportunity to study (near-) surface processes that occurred on early Mars. Here, we have conducted a transmission electron microscope study of medium- and coarse-grained (a few tens to hundreds of micrometers) Ca-rich pyroxene clasts in order to define their thermal and shock histories. The pyroxene grains have a high-temperature (magmatic) origin as revealed by the well-developed pigeonite-augite exsolution microstructure. Exsolution lamella characteristics (composition, thickness, and spacing) indicate a moderately slow cooling. Some of the pyroxene clasts display evidence for local decomposition into magnetite and silica at the submicron scale. This phase decomposition may have occurred at high temperature and occurred at high oxygen fugacity at least 2-3 log units above the QFM buffer, after the formation of the exsolution lamellae. This corresponds to oxidizing conditions well above typical Martian magmatic conditions. These oxidizing conditions seem to have prevailed early and throughout most of the history of NWA 7533. The shock microstructure consists of (100) mechanical twins which have accommodated plastic deformation. Other pyroxene shock indicators are absent. Compared with SNC meteorites that all suffered significant shock metamorphism, NWA 7533 appears only mildly shocked. The twin microstructure is similar from one clast to another, suggesting that the impact which generated the (100) twins involved the compacted breccia and that the pyroxene clasts were unshocked when they were incorporated into the NWA 7533 breccia.

  8. Contribution to the speleology of Sterkfontein cave, Gauteng province, South Africa.

    Directory of Open Access Journals (Sweden)

    Martini Jacques E. J.

    2003-01-01

    Full Text Available The authors present more data about the speleological aspect of the Sterkfontein Cave, famous for its bone breccia which yielded abundant hominid remains. They also briefly review the previous voluminous studies by numerous authors, which are mainly dealing with the paleontology, stratigraphy and sedimentology of the breccia. The present investigations were oriented to hitherto poorly investigated aspects such as detail mapping of the cave, its country rock stratigraphy and recording the underground extension of the basal part of the breccia body. The cave consists of a complex network of phreatic channels, developed along joints in Neoarchaean cherty dolostone over a restricted surface of 250x250m. The combined length of all passages within this area amounts to 5,23km. The system extends over a height of about 50m and the dry part of it is limited downwards by the water-table appearing as numerous static pools. The fossiliferous breccia (= Sterkfontein Formation forms an irregular lenticular mass 75x25m horizontally by 40m vertically, which is included within the passage network. It crops out at surface and in the cave, and resulted from the filling of a collapse chamber, which was de-roofed by erosion. The present investigation confirmed that the cave and the Sterkfontein Formation are part of a single speleogenetic event. The breccia resulted from cavity filling by sediments introduced from a pit entrance, whereas many of the phreatic passages around it, which are developed at the same elevation, were only partly filled or remained entirely open up to present. This filling took place mainly in a vadose environment. Taking into account the age of the Sterkfontein Formation (>3,3-1,5 My, from base to top, the geomorphic evolution of the landscape and the context of other caves in the region, it seems that the cave might have started to form 5 My ago. It has been continuously developing up to present as a result of a slow drop of the water-table.

  9. The Complex Stratigraphy of the Highland Crust in the Serenitatis Region of the Moon Inferred from Mineral Fragment Chemistry

    Science.gov (United States)

    Ryder, Graham; Norman, Marc D.; Taylor, G. Jeffrey

    1997-01-01

    Large impact basins are natural drill holes into the Moon, and their ejecta carries unique information about the rock types and stratigraphy of the lunar crust. We have conducted an electron microprobe study of mineral fragments in the poikilitic melt breccias collected from the Taurus Mountains at the Apollo 17 landing site. These breccias are virtually unanimously agreed to be impact melt produced in the Serenitatis impact event. They contain lithic fragments and much more abundant mineral fragments of crustal origin. We have made precise microprobe analyses of minor element abundances in fragments of olivine, pyroxene, and plagioclase to provide new information on the possible source rocks and the crustal stratigraphy in the Serenitatis region. These data were also intended to elucidate the nature of the cryptic geochemical component in breccias such as these with low-K Fra Mauro basalt compositions. We chose the finest-grained (i.e., most rapidly quenched) breccias for study, to avoid reacted and partly assimilated fragments as much as possible. Most of the mineral fragments appear to have been derived from rocks that would fall into the pristine igneous Mg-suite as represented by lithic fragments in the Apollo collection, or reasonable extensions of it. Gabbroic rocks were more abundant in the target stratigraphy than is apparent from the Apollo sample collection. Some pyroxene and plagiociase, but probably not much olivine, could be derived from feldspathic granulites, which are metamorphosed polymict breccias. Some mineral fragments are from previously unknown rocks. These include highly magnesian olivines (up to Fo(sub 94)), possibly volcanic in origin, that exacerbate the difficulty in explaining highly magnesian rocks in the lunar crust. It appears that some part of the lunar interior has an mg*(= 100 x Mg/(Mg/Fe) atomic) greater than the conventional bulk Moon value of 80-84. Other volcanic rocks, including mare basalts, and rapidly- cooled impact melt

  10. Petrogenesis of Igneous-Textured Clasts in Martian Meteorite Northwest Africa 7034

    Science.gov (United States)

    Santos, A. R.; Agee, C. B.; Humayun, M.; McCubbin, F. M.; Shearer, C. K.

    2016-01-01

    The martian meteorite Northwest Africa 7034 (and pairings) is a breccia that samples a variety of materials from the martian crust. Several previous studies have identified multiple types of igneous-textured clasts within the breccia [1-3], and these clasts have the potential to provide insight into the igneous evolution of Mars. One challenge presented by studying these small rock fragments is the lack of field context for this breccia (i.e., where on Mars it formed), so we do not know how many sources these small rock fragments are derived from or the exact formation his-tory of these sources (i.e., are the sources mantle de-rived melt or melts contaminated by a meteorite impactor on Mars). Our goal in this study is to examine specific igneous-textured clast groups to determine if they are petrogenetically related (i.e., from the same igneous source) and determine more information about their formation history, then use them to derive new insights about the igneous history of Mars. We will focus on the basalt clasts, FTP clasts (named due to their high concentration of iron, titanium, and phosphorous), and mineral fragments described by [1] (Fig. 1). We will examine these materials for evidence of impactor contamination (as proposed for some materials by [2]) or mantle melt derivation. We will also test the petrogenetic models proposed in [1], which are igneous processes that could have occurred regardless of where the melt parental to the clasts was formed. These models include 1) derivation of the FTP clasts from a basalt clast melt through silicate liquid immiscibility (SLI), 2) derivation of the FTP clasts from a basalt clast melt through fractional crystallization, and 3) a lack of petrogenetic relationship between these clast groups. The relationship between the clast groups and the mineral fragments will also be explored.

  11. Geological study of Ujungwatu area as support for NPP planning in Muria Central Java

    International Nuclear Information System (INIS)

    In accordance with growth of life in Java, the need for electricity is also growing accordingly. Efforts to provide electricity such as planning to build nuclear power plant (NPP) has been in the debate for a while. There are many factors to be considered in this planning, such as its environmental condition. Geological factor is one of the important one to be considered. Surface geological conditions around NPP area at Ujungwatu needed include stratigraphy, geological structure, geomorphology, and environmental geology. Geology in Ujungwatu at radius 5 km is quite interesting. This area is part of Genuk volcano group which is laid at south and Ujungwatu coast at north. Genuk mountain group is divided into mountain slope, mountain back, and mountain skeleton. Coastal area is composed of coast sand. Sand up to broken rock was present along river gullies. Others were volcanic rocks which was composed of lapili tuff, trachite, pyroxene andesite, tuff breccia, tephrite-andesitic tuff breccia, and basaltic tuff breccia. Volcanic structure is well reflected by morphological feature as lineaments and half circular form in mount Genuk. This structure was predominantly in NW-SE direction, and less dominant in NE-SW direction. Ujungwatu, from environmental view, is deserved to be developed because of its underground potency. Iron sand, fluvial tuff, kaolin, mud, riverstone, volcanic rock, tuff and marble were easily found underground. Those could be benefited to the people in the area so that it could change socio-economical condition of the people which in turn electricity is becoming a necessity. Last but not least, Portuguese fort as potential touristic object is also situated at Kartini beach near Ujungwatu. (author). 15 refs, 3 tabs, 5 figs

  12. The submarine record of a large-scale explosive eruption in the Vanuatu Arc: ˜1 Ma Efaté Pumice Formation

    Science.gov (United States)

    Raos, Alison M.; McPhie, Jocelyn

    The Efaté Pumice Formation (EPF) is the record of a major explosive eruption that occurred in the Vanuatu arc, southwestern Pacific, at about 1 Ma. The EPF is the oldest stratigraphic unit of the Efaté Island Group and consists of a succession of non-welded, trachydacitic pumice breccia and shard-rich sand and silt beds with a minimum thickness of ˜500 m and a minimum bulk volume of approximately 85 km3. The lower part (Efaté Pumice Breccias) of the EPF comprises very thick beds composed almost exclusively of glassy, trachydacitic, pumice fragments with ragged terminations. In contrast, the upper part (Rentabau Tuffs) consists of up to 70 m of well-bedded and well-sorted shard-rich sand and silt. The clast population of this upper part comprises >95% glassy or formerly glassy shards, but fossil foraminifera are a ubiquitous and important non-volcanic component. Some glass shards have blocky, equant shapes and arcuate fracture surfaces, features typically associated with the influence of external water during fragmentation, but most are cuspate and platy bubble-wall shards. Pyroclast morphologies indicate that the Efaté Pumice Breccias were largely generated by magmatic-volatile-driven ("dry"), explosive fragmentation processes, and lithofacies characteristics indicate deposition in below-storm-wave-base environments, from eruption-sourced, water-supported density currents of waterlogged pumice. The Rentabau Tuffs are interpreted to represent a change to hydromagmatic activity in response to waning discharge that allowed ingress of water (presumably seawater) to the vent(s).

  13. Debris jets in continental phreatomagmatic volcanoes: A field study of their subterranean deposits in the Coombs Hills vent complex, Antarctica

    Science.gov (United States)

    Ross, Pierre-Simon; White, James D. L.

    2006-01-01

    The Ferrar large igneous province of Antarctica contains significant mafic volcaniclastic deposits, some of which are interpreted to fill large vent complexes. Such a complex was re-examined at Coombs Hills to map individual steep-sided cross-cutting bodies in detail, and we found several contrasting types, two of which are interpreted to have filled subterranean passageways forcefully opened from below into existing, non-consolidated debris. These transient conduits were opened because of the propagation of debris jets - upward-moving streams of volcaniclastic debris, steam, magmatic gases +/- liquid water droplets - following explosive magma-aquifer interaction. Some debris jets probably remained wholly subterranean, whereas others made it to the surface, but the studied outcrops do not allow us to differentiate between these cases. The pipes filled with country rock-rich lapilli-tuff or tuff-breccia are interpreted to have formed following phreatomagmatic explosions occurring near the walls or floor of the vent complex, causing fragmentation of both magma and abundant country rock material. In contrast, some of the cross-cutting zones filled with basalt-rich tuff-breccia or lapilli-tuff could have been generated following explosions taking place within pre-existing basalt-bearing debris, well away from the complex walls or floor. We infer that once focused jets were formed, they did not incorporate significant amounts of existing debris while travelling through them; instead, incorporation of fragments from the granular host took place near explosion sites. Other basalt-rich tuff-breccia zones, accompanied by domains of in situ peperite and coherent basalt pods, are inferred to have originated by less violent processes.

  14. Zinc isotopes in sphalerite from base metal deposits in the Red Dog district, northern Alaska

    Science.gov (United States)

    Kelley, K.D.; Wilkinson, J.J.; Chapman, J.B.; Crowther, H.L.; Weiss, D.J.

    2009-01-01

    Analyses of sphalerite samples from shale-hosted massive sulfide and stratigraphically underlying vein breccia deposits in the Red Dog district in northern Alaska show a range ??66Zn values from zero to 0.60 per mil. The lowest values are observed in the vein breccia deposits, and the stratigraphically overlying (but structurally displaced) shale-hosted massive sulfide deposits show a systematic trend of increasing ??66Zn values from south to north (Main-Aqqaluk-Paalaaq-Anarraaq). The ??66Zn values are inversely correlated with sphalerite Fe/Mn ratio and also tend to be higher in low Cu sphalerite, consistent with precipitation of lower ??66Zn sphalerite closer to the principal hydrothermal fluid conduits. The most likely control on isotopic variation is Rayleigh fractionation during sulfide precipitation, with lighter zinc isotopes preferentially incorporated in the earliest sphalerite to precipitate from ore fluids at deeper levels (vein breccias) and close to the principal fluid conduits in the orebodies, followed by precipitation of sulfides with higher ??66Zn values in shallower and/or more distal parts of the flow path. There is no systematic variation among the paragenetic stages of sphalerite from a single deposit, suggesting an isotopically homogeneous zinc source and consistent transport-deposition conditions and/or dissolution-reprecipitation of earlier sphalerite without significant fractionation. Decoupled Zn and S isotope compositions are best explained by mixing of separate metal- and sulfur-bearing fluids at the depositional site. The results confirm that Zn isotopes may be a useful tracer for distinguishing between the central and distal parts of large hydrothermal systems as previously suggested and could therefore be of use in exploration. ?? 2009 by Economic Geology.

  15. The Chicxulub crater - impact metamorphism of sulfate and carbonate lithologies

    Science.gov (United States)

    Deutsch, A.; Langenhorst, F.; Hornemann, U.; Ivanov, B. A.

    2003-04-01

    It is discussed whether in the aftermath of the Chicxulub event, impact-released CO_2 and SO_x have changed the Earth's climate, acting also as lethal thread for life. Undoubtedly, vaporization of carbonates and sulfates, which are major target lithologies at the Chicxulub impact site, occurred in the footprint of the projectile. What happened to these lithologies outside this very restricted zone was so far unconstrained. Petrologic observations on PEMEX and UNAM as well as on the CSDP cores allow to set up a general classification for shock-related pro-grade effects on sulfate and carbonate sedimentary rocks. Shock effects in lithic breccias are restricted to brecciation and formation of twins in calcite. Suevites mostly lack melted carbonate clasts; annealing effects in anhydrite fragments are absent. The underlying melt breccias contain anhydrite fragments still displaying a sedimentary texture, and limestone clasts, whose texture reflect crystallization from melt. Impact melt breccias from deeper levels frequently contain partially resorbed anhydrite clasts and a melt matrix with the Ca-rich mineral assemblage quartz + plagioclase + clinopyroxene; this mineral assemblage provides evidence for partial dissociation of CaSO_4. Large clasts of anhydrite consist of equant crystals with 120^o triple junctions, a feature indicative for re-crystallization in the solid state. Tagamites (impact melt rocks) are virtually free of clasts from sedimentary lithologies. These rocks have an extremely high formation temperature, which caused total dissociation of CaSO_4 and CaCO_3. Finally, up to 100 μm wide veins of anhydrite + calcite + quartz cut the matrix of all lithologies except the tagamites. They probably represent "degassing vents". The given scheme is in qualitative accordance with data of shock recovery and annealing experiments as well as with modeling results. In addition, it substantiates that annealing plays a fundamental role in the impact metamorphism of

  16. Hydrothermal dolomitization of basinal deposits controlled by a synsedimentary fault system in Triassic extensional setting, Hungary

    Science.gov (United States)

    Hips, Kinga; Haas, János; Győri, Orsolya

    2016-06-01

    Dolomitization of relatively thick carbonate successions occurs via an effective fluid circulation mechanism, since the replacement process requires a large amount of Mg-rich fluid interacting with the CaCO3 precursor. In the western end of the Neotethys, fault-controlled extensional basins developed during the Late Triassic spreading stage. In the Buda Hills and Danube-East blocks, distinct parts of silica and organic matter-rich slope and basinal deposits are dolomitized. Petrographic, geochemical, and fluid inclusion data distinguished two dolomite types: (1) finely to medium crystalline and (2) medium to coarsely crystalline. They commonly co-occur and show a gradual transition. Both exhibit breccia fabric under microscope. Dolomite texture reveals that the breccia fabric is not inherited from the precursor carbonates but was formed during the dolomitization process and under the influence of repeated seismic shocks. Dolomitization within the slope and basinal succession as well as within the breccia zones of the underlying basement block is interpreted as being related to fluid originated from the detachment zone and channelled along synsedimentary normal faults. The proposed conceptual model of dolomitization suggests that pervasive dolomitization occurred not only within and near the fault zones. Permeable beds have channelled the fluid towards the basin centre where the fluid was capable of partial dolomitization. The fluid inclusion data, compared with vitrinite reflectance and maturation data of organic matter, suggest that the ascending fluid was likely hydrothermal which cooled down via mixing with marine-derived pore fluid. Thermal gradient is considered as a potential driving force for fluid flow.

  17. Impact history of the Chelyabinsk meteorite: Electron microprobe and LA-ICP-MS study of sulfides and metals

    Science.gov (United States)

    Andronikov, A. V.; Andronikova, I. E.; Hill, D. H.

    2015-12-01

    Electron microprobe and LA-ICP-MS study of sulfides and metals from two fragments of the LL5 Chelyabinsk meteorite were conducted. The fragments are impact breccias, one fragment contains both chondritic and shock vein lithologies, and the other contains shock-darkened chondritic clasts and vesicular impact melts. The chondritic lithology and shock veins display very similar opaque mineral compositions. The mineral compositions in the impact-melt breccias are distinctly different. The brecciated state of the Chelyabinsk meteorite suggests strong involvement of shock-related processes during the evolution of the parent body. Multiple heavy impact events occurred on the parent asteroid and on the Chelyabinsk meteoroid itself over the time period from ca. 4.5 Ga until ca. 1.2 Ma. The shock veins were produced in situ on the parent body. The impact-melt breccias could have formed because of the dramatic impact to the parent LL-chondrite body that could be partly disintegrated. The fragment containing shock-darkened chondritic clasts and vesicular impact melt lithologies preserves a record of melting, volatilization, partial degassing, and quenching of the molten material. The abundance and size (up to 1 mm) of the vesicles suggest that the impact melt must have been buried at some depth after formation. After impact and subsequent melting occurred, the impact-induced pressure on the shallow asteroid interior was released that caused "boiling" of volatiles and generation of S-rich bubbles. Such an impact excavated down to depths of the body generating multiple fragments with complicated histories. These fragments reaccumulated into a gravitational aggregate and formed the parental meteoroid for the Chelyabinsk meteorite.

  18. Structural, mineralogical, and paleoflow velocity constraints on Hercynian tin mineralization: the Achmmach prospect of the Moroccan Central Massif

    Science.gov (United States)

    Mahjoubi, El Mahjoub; Chauvet, Alain; Badra, Lakhlifi; Sizaret, Stanislas; Barbanson, Luc; El Maz, Abdelkader; Chen, Yan; Amann, Méderic

    2016-03-01

    The Achmmach tin mineralization (NE of the Moroccan Central Massif) is associated with tourmaline-rich alteration halos, veins, and faults hosted in sandstones and metapelites of the Upper Visean-Namurian. These deposits are reported to be late Hercynian in age and related to the emplacement of late-orogenic granite not outcropping in the studied area. Structural and paragenetic studies of the Achmmach tin deposit were conducted in order to establish a general model of the mineralization. From field constraints, the late Hercynian phase is marked by a transition from transpression to extension with deformation conditions evolving from ductile to brittle environments. The transpression (horizontal shortening direction roughly trending E-W) is coeval with the emplacement of the first tourmaline halos along several conjugated trends (N070, N020, and N120). Thereafter, a tourmaline-rich breccia formed in response to the fracturing of early tourmaline-altered rocks. Subsequently, during the extensional phase, these structures were reactivated as normal faults and breccias, allowing the formation of the main tin mineralization (cassiterite) associated with a wide variety of sulfides (arsenopyrite, chalcopyrite, sphalerite, galena, pyrrhotite, bismuthinite, pyrite, and stannite). This evolution ends with fluorite and carbonate deposition. The hydrothermal fluid flow velocity, calculated by applying statistical measures on the tourmaline growth bands, varies with the lithology. Values are lower in metapelites and higher in breccia. In the general evolution model proposed here, tourmaline alteration makes the rock more competent, allowing for brittle fracturing and generation of open space where the main Sn mineralization was precipitated.

  19. Chemical Zoning of Feldspars in Lunar Granitoids: Implications for the Origins of Lunar Silicic Magmas

    Science.gov (United States)

    Mills, R. D; Simon, J. I.; Alexander, C.M. O'D.; Wang, J.; Christoffersen, R.; Rahman, Z..

    2014-01-01

    Fine-scale chemical and textural measurements of alkali and plagioclase feldspars in the Apollo granitoids (ex. Fig. 1) can be used to address their petrologic origin(s). Recent findings suggest that these granitoids may hold clues of global importance, rather than of only local significance for small-scale fractionation. Observations of morphological features that resemble silicic domes on the unsampled portion of the Moon suggest that local, sizable net-works of high-silica melt (>65 wt % SiO2) were present during crust-formation. Remote sensing data from these regions suggest high concentrations of Si and heat-producing elements (K, U, and Th). To help under-stand the role of high-silica melts in the chemical differentiation of the Moon, three questions must be answered: (1) when were these magmas generated?, (2) what was the source material?, and (3) were these magmas produced from internal differentiation. or impact melting and crystallization? Here we focus on #3. It is difficult to produce high-silica melts solely by fractional crystallization. Partial melting of preexisting crust may therefore also have been important and pos-sibly the primary mechanism that produced the silicic magmas on the Moon. Experimental studies demonstrate that partial melting of gabbroic rock under mildly hydrated conditions can produce high-silica compositions and it has been suggested by that partial melting by basaltic underplating is the mechanism by which high-silica melts were produced on the Moon. TEM and SIMS analyses, coordinated with isotopic dating and tracer studies, can help test whether the minerals in the Apollo granitoids formed in a plutonic setting or were the result of impact-induced partial melting. We analyzed granitoid clasts from 3 Apollo samples: polymict breccia 12013,141, crystalline-matrix breccia 14303,353, and breccia 15405,78

  20. Groundwater Characterization of Cihaur Watershed Basin, Batujajar and Adjacent, West Bandung District, West Java, Indonesia

    Science.gov (United States)

    Azy, Fikri Noor; Sapari Dwi Hadian, Mohamad; Ismawan

    2016-01-01

    The study was conducted based on data from outcrop, well data, and springs with field orientation method assisted by the use of GPS and measurement tool physical and chemical properties of groundwater. Geological conditions investigated were geomorphology and stratigraphy, geomorphology unit study area consists of four units, namely geomorphology unit of strato volcano body, foot of strato volcano, intrusion units, and plains units and the river drainage patterns are parallel and subparallel. Stratigraphy in the study area are volcanic breccia (Qbv), Unit Andesite (Qa), Unit Tuff (Qtf) and Unit Clay Tuffan (Qlt). The characteristics of the groundwater of the study area are in form of the physico-chemical, major elements, and hydrolic parameter of the groundwater aquifers. From 27 locations, the water quality assesment by physico-chemical properties is classified as fresh water category and based on chemical major elements, has been classified 8 facies which are located in the study area. Then, there are two lithologies which act as aquifers ie, tuff and volcanic breccias. Conductivity values in the range of volcanic breccia aquifers respectively 0,128 m/day and 0,288 m/day, transmitivity (T) ranges respectively 1,9296 m2/day and 4,32 m2/day. The value of conductivity in tuff aquifer is 0,063 m/day, transmitivity (T) is 0,95 m2/day. While lithology Qlt (Clay tuffan) is lithology with very low productivity of groundwater or called groundwater rare area (akiclud) and the rock units Qa (Andesite) is a non-aquifer that is the absence of groundwater in these rock units (akifug).

  1. The Sytykanskaya kimberlite pipe:Evidence from deep-seated xenoliths and xenocrysts for the evolution of the mantle beneath Alakit, Yakutia, Russia

    Institute of Scientific and Technical Information of China (English)

    I.V. Ashchepkov; I.V. Makovchuk; V.S. Palesskiy; 0.S. Khmel’nikova; A.M. Logvinova; L.F. Reimers; T. Ntaflos; Z.V. Spetsius; N.V. Vladykin; H. Downes; D.S. Yudin; A.V. Travin

    2015-01-01

    Mantle xenoliths (>150) and concentrates from late autolithic breccia and porphyritic kimberlite from the Sytykanskaya pipe of the Alakit field (Yakutia) were analyzed by EPMA and LAM ICP methods. In P-T-X-f(O2) diagrams minerals from xenoliths show widest variations, the trends P-Fe#-CaO, f(O2) for minerals from porphyric kimberlites are more stepped than for xenocrysts from breccia. Ilmenite PTX points mark moving for protokimberlites from the lithosphere base (7.5 GPa) to pyroxenite lens (5e3.5 GPa) accompanied by Cr increase by AFC and creation of two trends P-Fe#Ol w10e12% and 13e15%. The Opx-Gar-based mantle geotherm in Alakit field is close to 35 mW/m2 at 65 GPa and 600 ?C near Moho was determined. The oxidation state for the megacrystalline ilmenites is lower for the metasomatic associations due to reduction of protokimberlites on peridotites than for uncontaminated varieties at the lithosphere base. Highly inclined linear REE patterns with deep HFSE troughs for the parental melts of clinopyroxene and garnet xenocrysts from breccia were influenced by differentiated protokimberlite. Melts for metasomatic xenoliths reveal less inclined slopes without deep troughs in spider diagrams. Garnets reveal S-shaped REE patterns. The clinopyroxenes from graphite bearing Cr-websterites show inclined and inflected in Gd spectrums with LREE variations due to AFC differen-tiation. Melts for garnets display less inclined patterns and Ba-Sr troughs but enrichment in Nb-Ta-U. The 40Ar/39Ar ages for micas from the Alakit mantle xenoliths for disseminated phlogopites reveal Proterozoic (1154 Ma) age of metasomatism in early Rodinia mantle. Veined glimmerites with richterite e like amphiboles mark w1015 Ma plume event in Rodinia mantle. The w600e550 Ma stage manifests final Rodinia break-up. The last 385 Ma metasomatism is protokimberlite-related.

  2. A Zircon U-Pb Study of the Evolution of Lunar KREEP

    Science.gov (United States)

    Meyer, Charles; Nemchin, A.; Pidgeon, R.; Whitehouse, M.; Vaughan, J.

    2007-01-01

    SIMS U-Pb analyses show that zircons from breccias from Apollo 14 and Apollo 17 have essentially identical age distributions in the range 4350 to 4200 Ma but, whereas Apollo 14 zircons additionally show ages from 4200 to 3900 Ma, the Apollo 17 samples have no zircons with ages <4200 Ma. The zircon results also show an uneven distribution with distinct peaks of magmatic activity. In explaining these observations we propose that periodic episodes of KREEP magmatism were generated from a primary reservoir of KREEP magma, which contracted over time towards the centre of Procellarum KREEP terrane.

  3. Evidence for coeval Late Triassic terrestrial impacts from the Rochechouart (France) meteorite crater

    CERN Document Server

    Carporzen, L; Carporzen, Laurent; Gilder, Stuart A.

    2006-01-01

    High temperature impact melt breccias from the Rochechouart (France) meteorite crater record magnetization component with antipodal, normal and reverse polarities. The corresponding paleomagnetic pole for this component lies between the 220 Ma and 210 Ma reference poles on the Eurasian apparent polar wander path, consistent with the 214 $\\pm$ 8 Ma 40Ar/39Ar age of the crater. Late Triassic tectonic reconstructions of the Eurasian and North American plates place this pole within 95% confidence limits of the paleomagnetic pole from the Manicouagan (Canada) meteorite impact crater, which is dated at 214 $\\pm$ 1 Ma. Together, these observations reinforce the hypothesis of a Late Triassic, multiple meteorite impact event on Earth.

  4. Thermoluminescence and the origin of the dark matrix of Fayetteville and similar meteorites

    Science.gov (United States)

    Haq, M.; Hasan, F. A.; Sears, D. W. G.; Moore, C. B.; Lewis, C. F.

    1989-06-01

    The paper presents measurements of the induced thermoluminescence properties and carbon contents of the dark matrix and light clasts of six regolith breccias. For all of the meteorites, the dark matrix has a lower mean thermoluminescence sensitivity than the light clasts; the extent of the difference depends on the meteorite. The data suggest the formation of the dark matrix by comminution of the light clasts with the addition of a component, perhaps CM-like chondrites, with thermoluminescence properties distinct from those of ordinary chondrites.

  5. Apollo 16 stratigraphy - The ANT hills, the Cayley Plains, and a pre-Imbrian regolith

    Science.gov (United States)

    Taylor, G. J.; Drake, M. J.; Hallam, M. E.; Marvin, U. B.; Wood, J. A.

    1973-01-01

    A total of 645 particles in the 1 to 2 mm size range has been classified in the Apollo 16 soil samples 60602,3, 61242,7, 66042,4, 67602,13, and 69942,13. Five major categories of lithic fragments recognized in these samples include (1) an anorthositic/noritic/troctolitic, or ANT suite, (2) light-matrix breccias, (3) poikiloblastic noritic/anorthositic fragments, (4) spinel-troctolites, and (5) feldspathic basalts. The petrography and phase chemistry of the lithic fragments are discussed along with results of the fragment census and the stratigraphy of the Apollo 16 site.

  6. Petrology of Diogenite NWA 5480, A Pristine Olivine-Rich Deformed Harzburgite

    Science.gov (United States)

    Peslier, A. H.; Brandon, A. D.; Tarduno, J. A.; Mittlefehldt, D. W.

    2015-01-01

    Diogenites are achondrites that are part of the HED (howardite, eucrite, diogenite) meteorite group thought to originate from asteroid Vesta. This suite of igneous rocks offers a glimpse of early planetary differentiation and subsequent igneous processes. While eucrites represent asteroidal basaltic crust and howardites the impact brecciated surface, diogenites are samples of the mantle and lower crust. Most of them are orthopyroxene (Opx) dominated cumulates, although harzburgites and rare dunites have also been found. The majority of diogenites are impact breccias. This study describes NWA 5480, a pristine, i.e. hardly altered and minimally shocked, harzburgitic diogenite.

  7. Kimberlite, lamproite, ultramafic lamprophyre, and carbonatite relationships on the Dharwar Craton, India; an example from the Khaderpet pipe, a diamondiferous ultramafic with associated carbonatite intrusion

    Science.gov (United States)

    Smith, C. B.; Haggerty, S. E.; Chatterjee, B.; Beard, A.; Townend, R.

    2013-12-01

    Are kimberlites, lamproites, ultramafic lamprophyres and carbonatites genetically associated or not? There are strong opinions for and against any relationship. The 20 Ha Khaderpet pipe, discovered by Rio Tinto Exploration, is an unusual diamondiferous carbonatite-kimberlite clan rock (KCR) association in the Anumpalle Cluster of the Wajrakarur Kimberlite Field in the Dharwar Craton of Peninsular Indian. The Khaderpet pipe has a discrete sovite phase intrusive into KCR breccia, not noticed elsewhere in the Wajrakarur kimberlite field. Petrographically, the KCR is a clast-supported lithic breccia and crystal lithic tuff, with occasional pelletal lapilli. Clasts show a weak horizontal imbrication. The overall appearance of the tuffs and breccias is suggestive of terminal-blocked, vent accumulations that formed by under pressure, with spallation of country rock causing an abundance of granitoid debris. The sovite phase has up to 95% calcite, occasionally showing flow textured polycrystalline laths set in a minor saponite matrix. There are mineralogical gradations from an olivine-rich ultramafic to a calcite-dominant rock resembling pure carbonatite. Rare REE mineral phases in the carbonatite include allanite and other REE-rich unidentified mineral phases. Xenocrystic high pressure phases in both ultramafic and carbonatite include mantle-derived diamonds, lherzolitic-, eclogitic- and subcalcic-pyrope, Ti-poor andradite, chrome diopside, picrochromite and picroilmenite. Extensive metasomatism in the form of reddening of country rock feldspars by hematite, introduction of green chlorite, and saponitic alteration of breccia clasts and the ultramafic phase is common. The chemistry of the Khaderpet ultramafic component, suggests that the KCR is transitional between kimberlite and ultramafic lamprophyres, like certain other pipes in the Wajrakarur Kimberlite Field, with strong enrichment in LREE, CaO and CO2. However, low MgO (~ 13%) and high CaO (~ 10%) values are more

  8. Bournonia excavata (D’Orbigny from the Campanian-Maastrichtian of Stranice (north-east of Slovenia

    Directory of Open Access Journals (Sweden)

    Mauro Caffau

    2002-06-01

    Full Text Available The rudist fauna of Stranice, in the north-east of Slovenia, has been studied for a long time thanks to the good preservation-state of the specimens found in the calcareous breccias from Campanian-Maastrichtian. The presence of Bournonia excavata (d’Orbignyat Stranice is reported for the first time in this work. The specimen described in this paper is compared with other specimens from other carbonate platform deposits, previously described by different authors. In addition, a complete individual with both valves ofRadiolites angeiodes (Lapeirouse is described.

  9. The enigmatic Zerelia twin-lakes (Thessaly, Central Greece): two potential meteorite impact Craters

    OpenAIRE

    Dietrich, V. J.; Lagios, E.; Reusser, E.; Sakkas, V; Gartzos, E.; Kyriakopoulos, K.

    2013-01-01

    Two circular permanent lakes of 150 and 250 m diameter and 6–8 m depth to an unconsolidated muddy bottom occur 250 m apart from each other in the agricultural fields SW of the town of Almiros (Thessaly, central Greece). The age of the lakes is assumed to be Late Pliocene to Early Holocene with a minimum age of approx. 7000 yr BP. The abundant polymict, quartz-rich carbonate breccia and clasts with a clay rich matrix in the shallow embankments of the lakes show weak strat...

  10. Spanish yellow cake production by bioleaching

    International Nuclear Information System (INIS)

    Eighty-seven percent of Spanish uranium production is obtained by bioleaching of the metamorphic shales of Salamanca. The deposit's paragenesis and mineralogy, with pitchblende and pyrite enrichening in the breccias and fissures are an optimum combination for direct attack of the pyrite by bacteria and the uranium's subsequent indirect leaching. The only acid which is introduced into the system is that used for conditioning the pregnant liquids before solvent extraction. Recycling (60-95%) of raffinates to leaching contributes sufficient acidity to have an optimum pH (2 - 2.6) for developing microorganisms. (author). 14 refs, 6 figs

  11. Crystallization Age and Impact Resetting of Ancient Lunar Crust from the Descartes Terrane

    Science.gov (United States)

    Norman, M. D.; Borg, L. E.; Nyquist, L. E.; Bogard, D. D.

    2002-01-01

    Lunar ferroan anorthosites (FANs) are relics of an ancient, primary feldspathic crust that is widely believed to have crystallized from a global magma ocean. Compositions and ages of FANs provide fundamental information about the origin and magmatic evolution of the Moon, while the petrology and thermal history of lunar FANs illustrate the structure and impact history of the lunar crust. Here we report petrologic, geochemical, and isotopic (Nd-Sr-Ar) studies of a ferroan noritic anorthosite clast from lunar breccia 67215 to improve our understanding of the composition, age, and thermal history of the Moon.

  12. Early Solar System Cryovolcanics in the Laboratory

    Science.gov (United States)

    Zolensky, M.; Fries, M.; Bodnar, R.; Yurimoto, H.; Itoh, S.; Steele, A.; Mikouchi, T.; Hagiya, K.; Ohsumi, K.; Le, L.; Rahman, Z.

    2013-01-01

    Two thermally-metamorphosed ordinary chondrite regolith breccias, Monahans 1998 (H5) and Zag (H3-6) contain fluid inclusion-bearing halite (NaCl) crystals, dated by K-Ar, Rb-Sr and I-Xe systematics to be approx. 4.5 billion years old. Heating/freezing studies of the aqueous fluid inclusions demonstrated that they were trapped near 25 C, and their continued presence in the halite grains requires that their incorporation into the H chondrite asteroid was post metamorphism.

  13. Geologic Mapping in Nogal Peak Quadrangle: Geochemistry, Intrusive Relations and Mineralization in the Sierra Blanca Igneous Complex, New Mexico

    Science.gov (United States)

    Goff, F.; Kelley, S. A.; Lawrence, J. R.; Cikowski, C. T.; Krier, D. J.; Goff, C. J.; McLemore, V. T.

    2011-12-01

    Nogal Peak quadrangle is located in the northern Sierra Blanca Igneous Complex (SBIC) and contains most of the White Mountain Wilderness (geologic map is available at http://geoinfo.nmt.edu/publications/maps/geologic/ofgm/details.cfml?Volume=134). The geology of the quad consists of a late Eocene to Oligocene volcanic pile (Sierra Blanca Volcanics, mostly alkali basalt to trachyte) intruded by a multitude of dikes, plugs and three stocks: Rialto, 31.4 Ma (mostly syenite), Three Rivers, ca. 29 to 27 Ma (quartz syenite intruded by subordinate alkali granite), and Bonito Lake, 26.6 Ma (mostly monzonite). Three Rivers stock is partially surrounded by alkali rhyolites that geochemically resemble the alkali granites. The circular shape of the stock and surrounding rhyolites suggests they form the root of a probable caldera. SBIC rocks have compositions typical of those found within the Rocky Mountain alkaline belt and those associated with continental rift zone magmatism. Because the volcanic host rocks are deeply eroded, intrusive relations with the stocks are well exposed. Most contacts at stock margins are near vertical. Roof pendants are common near some contacts and stoped blocks up to 700 m long are found within the Three Rivers stock. Contacts, pendants and stoped blocks generally display some combination of hornfelsing, brecciation, fracturing, faulting and mineralization. Sierra Blanca Volcanics display hydrothermal alteration increasing from argillic in the NW sector of the quad to high-temperature porpylitic near stock margins. Retrograde phyllic alteration occurs within breccia pipes and portions of the stocks. Mineral deposits consist of four types: Placer Au, fissure veins (mostly Ag-Pb-Zn±Au), breccia pipes (Au-Mo-Cu), and porphyry Mo-Cu. A singular pipe on the SW margin of Bonito Lake stock contains sapphire-lazulite-alunite. Although Au has been intermittently mined in the quad since 1865, best production of Au originated around the turn of the last

  14. Nature of the gases released from lunar rocks and soils upon crushing

    Science.gov (United States)

    Gibson, E. K., Jr.; Andrawes, F. F.

    1978-01-01

    Qualitative and quantitative analyses of inorganic gases released from lunar basalts, breccias and soils by crushing have been performed in an apparatus which consists of a piston operating in a stream of purified He and a dual-column gas chromatograph equipped with He-ionization detectors. The apparatus eliminates the problem of adsorption of the released gases by fresh sample surfaces generated by crushing. Upper concentration levels for nitrogen, H2, CH4, O2 and other gases released from crushed basalts are reported. A direct correlation is established between the amount of nitrogen released from lunar soils by crushing and the lunar soil maturity indicator proposed by Morris (1976).

  15. Large phreatomagmatic vent complex at Coombs Hills, Antarctica: Wet, explosive initiation of flood basalt volcanism in the Ferrar-Karoo LIP

    Science.gov (United States)

    McClintock, Murray; White, James D. L.

    2006-01-01

    The Mawson Formation and correlatives in the Transantarctic Mountains and South Africa record an early eruption episode related to the onset of Ferrar-Karoo flood basalt volcanism. Mawson Formation rocks at Coombs Hills comprise mainly (≥80% vol) structureless tuff breccia and coarse lapilli tuff cut by irregular dikes and sills, within a large vent complex (>30 km2). Quenched juvenile fragments of generally low but variable vesicularity, accretionary lapilli and country rock clasts within vent-fill, and pyroclastic density current deposits point to explosive interaction of basalt with groundwater in porous country rock and wet vent filling debris. Metre-scale dikes and pods of coherent basalt in places merge imperceptibly into peperite and then into surrounding breccia. Steeply dipping to sub-vertical depositional contacts juxtapose volcaniclastic rocks of contrasting componentry and grainsize. These sub-vertical tuff breccia zones are inferred to have formed when jets of debris + steam + water passed through unconsolidated vent-filling deposits. These jets of debris may have sometimes breached the surface to form subaerial tephra jets which fed subaerial pyroclastic density currents and fall deposits. Others, however, probably died out within vent fill before reaching the surface, allowing mixing and recycling of clasts which never reached the atmosphere. Most of the ejecta that did escape the debris-filled vents was rapidly recycled as vents broadened via lateral quarrying of country rock and bedded pyroclastic vent-rim deposits, which collapsed along the margins into individual vents. The unstratified, poorly sorted deposits comprising most of the complex are capped by tuff, lapilli tuff and tuff breccia beds inferred to have been deposited on the floor of the vent complex by pyroclastic density currents. Development of the extensive Coombs Hills vent-complex involved interaction of large volumes of magma and water. We infer that recycling of water, as well

  16. Temperature emission spectrum of exoelectrons of lunar regolith

    Science.gov (United States)

    Mints, R. I.; Alimov, V. I.; Melekhin, V. P.; Milman, I. I.; Kryuk, V. I.; Petukhova, T. M.; Kunin, L. L.; Tarasov, L. S.

    1974-01-01

    Thermostimulated exoelectronic emission of eight fragments of regolith returned by the Soviet Luna 16 automatic station was studied. The nature of the exoemission glove-curves was determined by particle type. Fragments of breccia, sinter, slag, anorthosite, glass plate, and leucocratic gabbro after the first heating disclosed a single exoemission maximum, whose temperature position is in the range 115 to 200 C. The data obtained indicate the complex and inhomogeneous energy structure of some regolith fragments. The presence of surface states capable of forming sorptive bonds can be assumed for most particles. The exoemission of anorthosite, olivine, and the glass spherule is due to the presence of formation defects at their surfaces.

  17. Tectonic implication of stockwork microbreccias

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jiasheng; HUANG Xiongnan; LIU Jianmin

    2005-01-01

    The stockwork microbreccia found in the Dabie and Helan Mountains bears no relation to either meteorite impact and cryptoexplosion, or fault displacement. It is controlled by tensional or transtensional fracture network in relatively hard felsic crystalline rocks, appearing as breccia with dark cryptocrystalline matrix. The kilometer-scale distribution and complicated relation to fracture system of the stockwork microbreccias, randomly distributed autochthonous fragments of host rock, ultracataclasis without notable displacement in the cryptocrystalline matrix, and a probable solid-state amorphization deformation mechanism all suggest that large-scale, high-energy and rapid brittle fracturing event might have occurred in the rocks at relatively deep crustal level in the areas.

  18. Chemistry and surface morphology of soil particles from Luna 20 LRL sample 22003.

    Science.gov (United States)

    Carter, J. L.

    1973-01-01

    Optical and scanning electron microscopy, scanning electron microprobes and energy dispersion techniques were applied in an analysis of six siliceous glass spheres, five siliceous glass-bonded agglutinates and one breccia fragment from Luna 20 sample 22003. It is theorized that local meteor impact processes might have been responsible for the formation of most of the glass spheres and that the impacts of relatively high velocity particles might have been responsible for the craters observed on the surfaces of the spheres. The concentrations of iron spherules on the surfaces of the glass spheres were generally lower than in similar Apollo 11 and 12 glass spheres.

  19. Karakul: a young complex impact crater in the Pamir, Tajikistan

    Science.gov (United States)

    Bouley, S.; Baratoux, D.; Baratoux, L.; Colas, F.; Dauvergne, J.; Losiak, A.; Vaubaillon, J.; Bourdeille, C.; Jullien, A.; Ibadinov, K.

    2011-12-01

    A fascinating controversy has been recently renewed about the origin of the Karakul depression in the Pamir (Tajikistan, 39°1'N, 73°27'E), about 4000 m above sea level. Based on the work of E. Gurov reporting breccia and shock features in minerals, the circular depression was mentioned in the Earth Impact Database as one of the largest complex craters, about 50 km in diameter. However, recent studies have suggested that the basin is actually a NW-SE extensional rift. We report the preliminary results of a new expedition in the Karakul area that successfully took place in June 2011. Different types of rocks have been observed, including metamorphosed sediments, granite, limestone, and rare occurrence. The granite appears to be the youngest rock predating the crater, with an age of 230-190 My2. The most exciting preliminary result is the finding of shatter cones in metamorphosed sediments in the northern part of the peninsula. Breccias (not necessary impact-breccia) occur as floats on the central island, and were also found in the northern part of the rim. Thin sections are in preparation at the time of writing, and the report on the search for shock features in granite and breccias will be presented at the conference. The age of the crater is unknown, but is necessarily younger than the India-Asia collision, 55 - 60 My ago. On the basis of the oldest sediments filling the depression, the crater has been tentatively attributed to Neogene, or Pliocene, and would be then younger than 23 My. Consequences of the formation of a large complex crater in the recent geological history of the Pamir have yet to be explored. In a context of elevated convergence rate and rapid exhumation, the site offers the possibility to investigate the possible interactions between impact cratering and tectonic activity. The formation of a 50 km crater has considerable effects on the environment, at least at the regional scale, suggesting the search for such effects in the sediment record

  20. An unusual clast in lunar meteorite MacAlpine Hills 88105: a unique lunar sample or projectile debris?

    OpenAIRE

    Joy K. H., Crawford I. A., Huss G., Nagashima K., and Taylor G.J.

    2014-01-01

    Lunar meteorite MacAlpine Hills (MAC) 88105 is a well-studied feldspathic regolith breccia dominated by rock and mineral fragments from the lunar highlands. Thin section MAC 88105,159 contains a small rock fragment, 400 × 350 μm in size, which is compositionally anomalous compared with other MAC 88105 lithic components. The clast is composed of olivine and plagioclase with minor pyroxene and interstitial devitrified glass component. It is magnesian, akin to samples in the lunar High Mg-...

  1. The frequency dependence of the viscous component of the magnetic susceptibility of lunar rock and soil samples

    Science.gov (United States)

    Hanneken, J. W.; Vant-Hull, L. L.; Carnes, J. G.

    1976-01-01

    The susceptibility of two lunar samples (a soil and a low metamorphic grade breccia) has been measured in a weak field - 0.001 Oe - and as a function of frequency from 0.032 to 1.0 Hz. The measurements were made using a superconducting magnetometer. The results show that the susceptibility decreases linearly with the log of frequency. This observation is in agreement with a theoretical model for viscous decay based on the Neel theory of single-domain and superparamagnetic grains. The relation derived agrees with a model in which there is a uniform distribution of relaxation times.

  2. GENERAL GEOLOGY

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>20110001 Chi Han (State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China); Li Chusi Shock-Metamorphosed Zircons in the Fragments of the Sudbury Breccias, Ontario, Canada (Earth Science Frontiers, ISSN1005-2321, CN11-3370/P, 17(1), 2010, p.86-92, 5 illus., 42 refs.)Key words: meteorite impacts, suevite, Canada It is widely accepted that the Sudbury structure formed by large bolide impact. To find more supporting evidences, the authors used elec

  3. Zn-Pb Ores of Mississippi Valley Type in the Lycksele-Storuman District, Northern Sweden: A Possible Rift-Related Cambrian Mineralisation Event

    Directory of Open Access Journals (Sweden)

    Kjell Billström

    2012-06-01

    Full Text Available The epigenetic Zn-Pb deposits in the Lycksele-Storuman ore district, northern Sweden, are hosted by Paleoproterozoic basement near the margin of the Caledonian mountains. A paleogeographic reconstruction suggests that platform sediments, including Cambrian shales, overlaid the mineralised basement. The mineralisation type, containing sphalerite, galena, calcite and fluorite, is confined to veins and breccias and interpreted to be of Mississippi Valley Type (MVT style. There is no appreciable wall rock alteration. Fluid inclusion work reveals coexisting aqueous and hydrocarbon fluids. Ore deposition is interpreted to have occurred during mixing of two fluids; a cool (

  4. 云南省江城、勐腊一带钾矿床和盐溶岩类的特征、形成条件以及找矿问题

    Institute of Scientific and Technical Information of China (English)

    邓尔新

    1982-01-01

    Potash deposits and various types of breccia-bearing argillaceous roeksalts and their surfacial salt-dissolved rocks are found in the Lower Tertiary strata in JiangehengMengla area, Yunnan Province. Distinct sedimentary cycles have been noticed for the potassium salt-bearing formations. These rocks are essentially mud stones cemented by salt minerals formed in stagnant, reducing environment in continental sabkhas. The potash deposits and potassium-bearing strata in this region are of marine origins as evidenced by dominant chlorides and high contents of Br and Rb in salt minerals.Methods for further prospecting efforts are also suggested.

  5. The Chacana caldera complex in Ecuador

    International Nuclear Information System (INIS)

    The Chacana caldera, located immediately east of Quito, capital of Ecuador, forms the most-northern edifice of Ecuadoros rhyolite province. It is a 50X30 km Pleistocene structure that has remained active into historic times. Vitrophyres, welded tuffs, and ignimbrites of rhyolitic and dacitic composition constitute the outer flanks, meantime syngenetic breccias and tuffs, capped later by extensive dacite lava flows and basin sediments, filled the calderaos depression. A notable resurgence occurred that lifted quiet-water sediments to over 4000 m in elevation. The area has numerous hot springs, and little seismic activity.

  6. On the barrier to crystal nucleation in lunar glasses

    Science.gov (United States)

    Yinnon, H.; Roshko, A.; Uhlmann, D. R.

    1980-01-01

    The paper describes an analytical method for calculating in detail the size distributions of small crystallites and nuclei in supercooled liquids as they are being quenched to form a glass and subsequently reheated above the glass transition to produce crystallization. This method is applied to experiments performed using differential thermal analysis (DTA) to estimate the barriers to crystal nucleation and the cooling rates required to form glasses or bodies with various degrees of crystallinity. DTA data and derived nucleation barriers are reported for anorthite and for the following lunar compositions: 15498, 15418, matrix and intrusion compositions of breccia 15286, Apollo 15 green glass, Luna 24 highland basalt, and 65016.

  7. Long term dismantling of a basaltic volcano (Piton des Neiges, La Réunion hotspot).

    Science.gov (United States)

    Chaput, Marie; Famin, Vincent; Michon, Laurent; Catry, Thibault

    2010-05-01

    We present a structural investigation of destabilization processes at the Piton des Neiges, the extinct volcano of La Reunion Island. We focus on the Cirque of Cilaos (a large erosional depression south of the volcano summit), where the exposed internal structure of Piton des Neiges is made of pahoehoe lava flows of the shield building stage (unknown thickness) and breccias (~1 km thick), covered by volcanic products of the differentiated stage (~1 km thick). The breccias contain only basic elements and consist in debris flows and debris avalanches deposits. Beddings in the debris flows and shear structures in the avalanche deposits indicate a runout in the direction 300°. We suggest that these breccias may represent the upper part of the Cap La Houssaye mass wasting events observed onshore and offshore on the western side of la Réunion (Bachèlery et al., 2003). The breccias display many indicators of brittle deformation, such as faults (normal and strike slip) and intrusions (dykes and sills). Fault data inversion allows to recognize two episodes of deformation. The first, older step of deformation is consistent with a minimum principal stress oriented N120. Intrusions related to this deformation are basic magmas of the shield building stage. The second, later stage of extension oriented N-S crosscuts the N120 deformation with intrusion compositions of the differentiated stage. These results show that the dismantling of Piton des Neiges proceeded in two ways: catastrophic episodic destabilization and slow internal deformation. During the shield-building stage, slow and rapid dismantling was occurring in the 300° direction in the studied area, whereas it evolved toward a N-S slow collapse during the differentiated stage of magmatic activity. This result fully agrees with a recent study carried out within debris avalanches deposits in the cirque of Salazie (north of Piton des Neiges summit) which attests that the northern flank of the Piton des Neiges has also

  8. Cooling History of Almahata Sitta Ureilite as Inferred from Transmission Electron Microscopy of Iron Metal

    Science.gov (United States)

    Mikouchi, T.; Aoyagi, Y.; Goodrich, C. A.; Yubuta, K.; Sugiyama, K.; Zolensky, M. E.; Goldstein, J. I.

    2013-01-01

    Almahata Sitta (AS) is a polymict breccia mainly composed of various ureilite lithologies with lesser chondritic lithologies [1]. In the ureilite lithologies, Fe metal is a common accessory phase present either as large grain boundary grains or small particles formed by reduction of olivine and pyroxene. In our earlier studies on grain boundary metals in one of AS fragments (#44) we found unique features never seen in other ureilites [2,3]. In order to further characterize these metal grains, we performed a detailed TEM study on a FIB section prepared from one of AS #44 grain boundary metals and here discuss its thermal history.

  9. GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS AND RELATED MINERALIZATION OF CHERT FORMATIONS IN SOUTH TIBET

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    There occur abundant cherts in the Mesozoic and Cenozoic strata in southern Tibet. Some of them possess characteristic hydrothermal structures such as layered, laminated, massive and breccia structures.Ratios of Al/(Al+Fe+Mn), Co/Ni, Fe/Ti and TiO2-Al2O3 demonstrate that their origin is related to hydrothermal sedimentation. The chert formations have close relationship with Sb, Au and poly-metallic mineralization, and the ore-forming fluid show strong correlation with fossil hydrothermal water.

  10. Palaeo-earthquake events during the late Early Palaeozoic in the central Tarim Basin (NW China: evidence from deep drilling cores

    Directory of Open Access Journals (Sweden)

    He Bizhu

    2014-07-01

    Full Text Available Various millimetre-, centimetre- and metre-scale soft-sediment deformation structures (SSDS have been identified in the Upper Ordovician and Lower-Middle Silurian from deep drilling cores in the Tarim Basin (NW China. These structures include liquefied-sand veins, liquefaction-induced breccias, boudinage-like structures, load and diapir- or flame-like structures, dish and mixed-layer structures, hydroplastic convolutions and seismic unconformities. The deformed layers are intercalated by undeformed layers of varying thicknesses that are petrologically and sedimentologically similar to the deformed layers.

  11. Workshop on Pristine Highlands Rocks and the early History of the Moon

    Science.gov (United States)

    Longhi, J. (Editor); Ryder, G. (Editor)

    1983-01-01

    Oxide composition of the Moon, evidence for an initially totally molten Moon, geophysical contraints on lunar composition, random sampling of a layered intrusion, lunar highland rocks, early evolution of the Moon, mineralogy and petrology of the pristine rocks, relationship of the pristine nonmore rocks to the highlands soils and breccias, ferroan anorthositic norite, early lunar igneous history, compositional variation in ferroan anosthosites, a lunar magma ocean, deposits of lunar pristine rocks, lunar and planetary compositions and early fractionation in the solar nebula, Moon composition models, petrogenesis in a Moon with a chondritic refractory lithophile pattern, a terrestrial analog of lunar ilmenite bearing camulates, and the lunar magma ocean are summarized.

  12. Research on the metallogenetic material source by means of mathematical statistics and spidergram. A case study of No.6722 uranium deposit in southern Jiangxi

    International Nuclear Information System (INIS)

    By means of Q-type fuzzy cluster analysis and spidergram on trace elements and REE data, the source of metallogenetic material for No. 6722 uranium deposit in South Jiangxi province is discussed in this paper. It has been discrminated that the ore-bearing cryptoexplosive breccia and the alted granite have a close genetical relationship with the biotite granite but not with the two-mica granite. It is concluded that mathematical statical analysis is able to obtain finer geochemical information with significant geo- logical implications which are hidden in the spidergram. Thus more strict and objective conclusions with scientific reappearance may be drawn after using this method. (authors)

  13. Mineral resources of the South Mccullough Mountains Wilderness Study Area, Clark County, Nevada

    International Nuclear Information System (INIS)

    The authors present a study of 19,558 acres of the South McCullough Mountains Wilderness Study Area. The study area contains no identified mineral resources and has no areas of high mineral resource potential. However, five areas that make up 20 percent of the study area have a moderate potential either for undiscovered silver, gold, lead, copper, and zinc resources in small vein deposits; for lanthanum and other rare-earth elements, uranium, thorium, and niobium in medium-size carbonatite bodies and dikes; for tungsten and copper in small- to medium-size vein deposits; or for silver and gold in small vein or breccia-pipe deposits. Six areas that makeup 24 percent of the study area have an unknown resource potential either for gold, silver, lead, and copper in small vein deposits; for gold, silver, lead, zinc, copper, and arsenic in small vein or breccia-pipe deposits; for lanthanum and other rare-earth elements, uranium, thorium, and niobium in medium-size carbonatite bodies and dikes; or for tungsten and copper in small vein deposits

  14. Determination of the occurrence of gold in an unoxidized Carlin-type ore sample using synchrotron radiation

    International Nuclear Information System (INIS)

    The occurrence of the so-called invisible gold in two unoxidized Carlin-type gold samples from Nevada have been determined using synchrotron x-ray fluorescence (SXRF) analysis at the National Sychrotron Light Source, Brookhaven National Laboratory. The samples were a bedded sample from the east ore zone of the Carlin deposit and a breccia sample from Horse Canyon. Preliminary results show that gold is found only in the Horse Canyon breccia sample. Experimental details including other x-ray line and diffraction peak interferences, standards used, and minimum detection limits (MDLs) are discussed. Gold was not detected in euhedral pyrite crystals except in the interior porous portion of one grain with MDLs of 0.8 to 3 ppM. Gold was detected in some parts of the matrix. The phase which contains gold has not yet been identified. The highest content of gold so far analyzed is about 40 ppM. Implications of these new findings are discussed. 2 figs

  15. Causes and consequences of conduit wall permeability changes during explosive eruptions

    Science.gov (United States)

    Rust, Alison; Hanson, Jonathan

    2015-04-01

    Magmatic volatiles, and in some cases external water, drive explosive volcanic eruptions and so the permeability of magma and conduit wall rocks can modulate the style and intensity of eruptions. Both modelling of eruption dynamics and field studies of lithic clasts indicate that fragmentation levels during explosive silicic eruptions commonly reach depths of kilometres. An important consequence is that substantial deviations from lithostatic pressure are sustained in the conduit during eruption, which, according to finite element modelling, are sufficient to damage a substantial volume of rock around the conduit. Underpressured regions will be susceptible to conduit erosion, widening the conduit; field data provide constraints on erosion rates and erosion depths where subsurface stratigraphy is known. Damage to wall rocks will also increase the rock permeability adjacent to the conduit, which could significantly affect magmatic degassing during and between eruptions. The degree to which external water can interact with magma in the conduit will also depend on wall rock permeability and spatial and temporal variations in pressure. When a major magmatic eruption ceases, deep magma is likely to ascend to fill the lower conduit, and the upper conduit may partially collapse forming vertically extensive breccia. Subvolcanic rocks exposed by exploration and mining of porphyry copper deposits (PCDs) and associated alteration and breccias may provide further field constraints on these models. Although syn- and post-mineralization explosive eruptions likely ruin potential PCDs, earlier eruptions might make space for vertical shallow intrusions and help establish permeable regions conducive to focussing of magmatic fluids required for PCD generation.

  16. Triassic beds in the basement of the Adriatic-Dinaric carbonate platform of Mt. Svilaja (Croatia

    Directory of Open Access Journals (Sweden)

    Vladimir Jelaska

    2003-12-01

    Full Text Available On the southwestern slope of Mt. Svilaja a Triassic sequence is exposed. It is composed of Lower Triassic carbonate siliciclastic shelf beds that are unconformably overlain by Anisian breccia. The overlying pelagic Anisian and Ladinian strata with pyroclastic rockscan be interpreted as a result of rift tectonics of Adria micro-plate. A 500 m thick sequence is capped by an emersion surface by karstification and terrigenous sediments including conglomerate as a result of Late Triassic transgression and marking the lower boundaryof a new, Late Mesozoic, megasequence of the External Dinarides.By means of conodont study, in the lowermost part of the studied Mesozoic sequence, a Lower Triassic shallow-water conodont fauna yielding Pachycladina obliqua apparatus was recorded. Pelagic limestone beds overlying the »Otarnik breccia« are marked byconodont elements of the Anisian constricta Zone. The Ladinian interval is characterized (from bottom to top: trammeri A. Z., hungaricus A. Z. and mungoensis A. Z. The uppermost part of the section below the emersion surface is identified by Pseudofurnishiusmurchianus, indicating the Upper Ladinian-Lower Carnian murchianus Zone.

  17. Ferromagnetic resonance studies of lunar core stratigraphy

    Science.gov (United States)

    Housley, R. M.; Cirlin, E. H.; Goldberg, I. B.; Crowe, H.

    1976-01-01

    We first review the evidence which links the characteristic ferromagnetic resonance observed in lunar fines samples with agglutinatic glass produced primarily by micrometeorite impacts and present new results on Apollo 15, 16, and 17 breccias which support this link by showing that only regolith breccias contribute significantly to the characteristic FMR intensity. We then provide a calibration of the amount of Fe metal in the form of uniformly magnetized spheres required to give our observed FMR intensities and discuss the theoretical magnetic behavior to be expected of Fe spheres as a function of size. Finally, we present FMR results on samples from every 5 mm interval in the core segments 60003, 60009, and 70009. These results lead us to suggest: (1) that secondary mixing may generally be extensive during regolith deposition so that buried regolith surfaces are hard to recognize or define; and (2) that local grinding of rocks and pebbles during deposition may lead to short scale fluctuations in grain size, composition, and apparent exposure age of samples.

  18. Stratigraphy of the Descartes region /Apollo 16/ - Implications for the origin of samples

    Science.gov (United States)

    Head, J. W.

    1974-01-01

    Analysis of terrain in the Apollo 16 Descartes landing region shows a series of features that form a stratigraphic sequence which dominates the history and petrogenesis at the site. An ancient 150-km diam crater centered on the Apollo 16 site is one of the earliest recognizable major structures. Nectaris ejecta was concentrated in a regional low at the base of the back slope of the Nectaris basin to form the Descartes Mountains. Subsequently, a 60-km diam crater formed in the Descartes Mountains centered about 25 km to the west of the site. This crater dominates the geology and petrogenetic history of the site. Stone and Smoky Mountains represent the degraded terraced crater walls, and the dark matrix breccias and metaclastic rocks derived from North and South Ray craters represent floor fallback breccias from this cratering event. The interpretation is developed that the stratigraphy of the Cayley and Descartes, and thus the historical record of the Apollo 16 region, documents the complex interaction of deposits and morphology of local and regional impact cratering events. Large local 60- to 150-km diam craters have had a dramatic and previously unrecognized effect on the history and petrology of the Apollo 16 site.

  19. Tectonic evolution, structural styles, and oil habitat in Campeche Sound, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Angeles-Aquino, F.J.; Reyes-Nunez, J.; Quezada-Muneton, J.M.; Meneses-Rocha, J.J. [Pemex Exploracion-Produccion, Mexico City (Mexico)

    1994-12-31

    Campeche Sound is located in the southern part of the Gulf of Mexico. This area is Mexico`s most important petroleum province. The Mesozoic section includes Callovian salt deposits; Upper Jurassic sandstones, anhydrites, limestones, and shales; and Cretaceous limestones, dolomites, shales, and carbonate breccias. The Cenozoic section is formed by bentonitic shales and minor sandstones and carbonate breccias. Campeche Sound has been affected by three episodes of deformation: first extensional tectonism, then compressional tectonism, and finally extensional tectonism again. The first period of deformation extended from the middle Jurassic to late Jurassic and is related to the opening of the Gulf of Mexico. During this regime, tilted block faults trending northwest-southwest were dominant. The subsequent compressional regime occurred during the middle Miocene, and it was related to northeast tangential stresses that induced further flow of Callovian salt and gave rise to large faulted, and commonly overturned, anticlines. The last extensional regime lasted throughout the middle and late Miocene, and it is related to salt tectonics and growth faults that have a middle Miocene shaly horizon as the main detachment surface. The main source rocks are Tithonian shales and shaly limestones. Oolite bars, slope and shelf carbonates, and regressive sandstones form the main reservoirs. Evaporites and shales are the regional seals. Recent information indicates that Oxfordian shaly limestones are also important source rocks.

  20. Determination of porosity and facies trends in a complex carbonate reservoir, by using 3-D seismic, borehole tools, and outcrop geology

    Energy Technology Data Exchange (ETDEWEB)

    Zacharakis, T.G. Jr.; Comet, J.N.; Murillo, A.A. [Respol Exploracion, S.A., Madrid (Spain)] [and others

    1996-08-01

    Mesozoic carbonate reservoirs are found in the Mediterranean Sea, off the east coast of Spain. A wide variation of porosities are found in the core samples and logs: vuggy, breccia, fractures, and cavern porosity. In addition, complex Tertiary carbonate geometries include olistostromes, breccia bodies, and reef buildups, which are found on top of Mesozoic carbonates. Predicting the porosity trends within these oil productive reservoirs requires an understanding of how primary porosity was further enhanced by secondary processes, including fractures, karstification, and dolomitization in burial conditions. Through an extensive investigation of field histories, outcrop geology, and seismic data, a series of basic reservoir styles have been identified and characterized by well log signature and seismic response. The distribution pattern of the different reservoirs styles is highly heterogeneous, but by integrating subsurface data and outcrop analogs, it is possible to distinguish field-scale and local patterns of both vertical and local variations in reservoir properties. Finally, it is important to quantify these reservoir properties through the study of seismic attributes, such as amplitude variations, and log responses at the reservoir interval. By incorporating 3-D seismic data, through the use of seismic inversion, it is possible to predict porosity trends. Further, the use of geostatistics can lead to the prediction of reservoir development within the carbonate facies.

  1. Hydrogeological properties of fault zones in a karstified carbonate aquifer (Northern Calcareous Alps, Austria)

    Science.gov (United States)

    Bauer, H.; Schröckenfuchs, T. C.; Decker, K.

    2016-03-01

    This study presents a comparative, field-based hydrogeological characterization of exhumed, inactive fault zones in low-porosity Triassic dolostones and limestones of the Hochschwab massif, a carbonate unit of high economic importance supplying 60 % of the drinking water of Austria's capital, Vienna. Cataclastic rocks and sheared, strongly cemented breccias form low-permeability (factor of 10 and fracture porosities varying by a factor of 3, and dilation breccias with average porosities >3 % and permeabilities >1,000 mD form high-permeability domains. With respect to fault-zone architecture and rock content, which is demonstrated to be different for dolostone and limestone, four types of faults are presented. Faults with single-stranded minor fault cores, faults with single-stranded permeable fault cores, and faults with multiple-stranded fault cores are seen as conduits. Faults with single-stranded impermeable fault cores are seen as conduit-barrier systems. Karstic carbonate dissolution occurs along fault cores in limestones and, to a lesser degree, dolostones and creates superposed high-permeability conduits. On a regional scale, faults of a particular deformation event have to be viewed as forming a network of flow conduits directing recharge more or less rapidly towards the water table and the springs. Sections of impermeable fault cores only very locally have the potential to create barriers.

  2. Apollo 16 soils - Grain size analyses and petrography

    Science.gov (United States)

    Heiken, G. H.; Mckay, D. S.; Fruland, R. M.

    1973-01-01

    Soils from South Ray Crater, North Ray Crater, and the interray area of Station 10 have a similar provenance, containing breccia fragments of low to medium metamorphic grade and low light/dark lithic fragment ratios; these appear to be characteristic of the Cayley Formation. The primary difference between soils possibly derived from North Ray and South Ray craters is in the agglutinate content. A soil from Stone Mountain (Station 4) is characterized by breccia fragments of medium to high metamorphic grade and a high light/dark lithic fragment ratio; this soil may be derived from the Descartes Formation. Differences between the selenomorphic units, the Descartes and Cayley formations, may be lithologic as well as structural. The mean grain size varies from 84 to 280 microns, and all of the samples are poorly to very poorly sorted. There appears to be a relation between the sorting, grain size, and agglutinate content, with the finer-grained, better sorted soils containing more than 30% agglutinates. 'Shadowed' soils, collected close to large boulders, are similar in all respects to the 'reference' soils collected at least 5 m from the boulders.

  3. Photogeology: Part D: Descartes highlands: possible analogs around the Orientale Basin

    Science.gov (United States)

    Hodges, Carroll Ann

    1972-01-01

    The Descartes highlands are adjacent to the terra plain on which the Apollo 16 lunar module landed (fig. 29-13). A variety of volcanic origins was proposed for the highlands before the mission (refs. 29-4, 29-21, and 29-35 to 29-37), but the returned samples of the area consist almost exclusively of nonvolcanic breccias. The breccias obtained from Stone Mountain have not been identified conclusively as sample materials of the Descartes Mountains (ref. 29-35). A volcanic origin is thus not yet precluded (sec. 6 of this report), but a review of possible impact-related origins seems to be appropriate. The orbital photography acquired during the Apollo 16 mission provides excellent imagery on which geomorphic interpretations may be based. No obvious local crater is a plausible source of the material, but there may be a relation to either the Nectaris or Imbrium Basin. The less degraded Orientale Basin (fig. 29-24) provides a model by which these comparisons can be made (part F of this section).

  4. Fluid Inclusions and Daughter Minerals of Taibai Gold Deposit, ShaanXi Province, China

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A discovery of daughter minerals in fluid inclusions of Taibai gold deposit, Shaanxi province has been focused on, which is a unique breccia-cemented gold-bearing system. The breccia zone strikes NWW-SEE, occurring in Devonian strata of Southern Qinling Mountains. The cement is mainly composed of ankerite, pyrite, calcite and quartz, which may be divided into four main tectonic-mineralizing stages. Gold mainly occurs in pyrite and ankerite of stage II and IV. It is found that three types of fluid inclusions can be distinguished: (1) aqueous inclusions (type B); (2) CO2-rich inclusions (type C); (3) daughter minerals-containing inclusions (type A). LRM (Laser Raman Micro-probe) analyses shows that the content of CO2 occupies 54.4-70.7% (mole fraction, so as the follows) in vapor phases of different type fluid inclusions. CH4 (5.2%-7.3%) and H2S (6.0%-12.7%) exist in both vapor and liquid phases. Many daughter minerals in fluid inclusions of ankerite and quartz have been found. Several kinds of daughter minerals, including ankerite, pyrite, arsenopyrite and halite, were determined by using SEM (scanning electron microscope) / EDS (energy dispersive spectrometer) technique. EPMA (electron probe micro-analysis) technique was also applied to study the daughter minerals exposed to the surface of polis hed thin sections.

  5. Nature of uranium mineralization and associated wall rock alteration in the White's East area of the Embayment, Rum Jungle, Northern Territory

    International Nuclear Information System (INIS)

    The uranium mineralisation in the White's East area of The Embayment is hosted by Lower Proterozoic schists of the Masson formation which have undergone polyphase deformation and upper greenschist metamorphism. Significant mineralisation is also present in apatite rocks. The ore zones occur near an unconformity with overlying Middle Proterozoic sandstone and breccia conglomerate. Kink breccias and fracture systems related to post Middle Proterozoic reverse faults are the controls for mineralising fluid migration. Pitchblende is the main uranium mineral and it occurs as fine disseminated grains, fibrous webs, clusters composed of botryoidal aggregates and locally as veins. Two generations of uranium mineralisation are present. The first generation (pitchblende I) occurs as fine grained inclusions within chlorite II, and the second (pitchblende II) as hydraulic fracture networks and massive veins intimately associated with sericite-hematite-chlorite III. Two hydrothermal alteration phases have affected both Lower Proterozoic and Middle Proterozoic sequences. The most extensive alteration mineral is chlorite, of which a number of varieties has been identified

  6. Geology of the Pavana geothermal area, Departamento de Choluteca, Honduras, Central America: Field report

    Energy Technology Data Exchange (ETDEWEB)

    Eppler, D.B.; Heiken, G.; Wohletz, K.; Flores, W.; Paredes, J.R.; Duffield, W.A.

    1987-09-01

    The Pavana geothermal area is located in southern Honduras near the Gulf of Fonseca. This region is underlain by late Tertiary volcanic rocks. Within ranges near the geothermal manifestations, the rock sequences is characterized by intermediate to mafic laharic breccias and lavas overlain by silicic tuffs and lavas, which are in turn overlain by intermediate to mafic breccias, lavas, and tuffs. The nearest Quaternary volcanoes are about 40 km to the southwest, where the chain of active Central American volcanoes crosses the mouth of the Gulf of Fonseca. Structure of the Pavana area is dominated by generally northwest-trending, southwest-dipping normal faults. This structure is topographically expressed as northwest-trending escarpments that bound blocks of bedrock separated by asymmetric valleys that contain thin alluvial deposits. Thermal waters apparently issue from normal faults and are interpreted as having been heated during deep circulation along fault zones within a regional environment of elevated heat flow. Natural outflow from the main thermal area is about 3000 l/min of 60/sup 0/C water. Geothermometry of the thermal waters suggests a reservoir base temperature of about 150/sup 0/C.

  7. Comparison of the mineralogy of the Boss-Bixby, Missouri copper-iron deposit, and the Olympic Dam copper-uranium-gold deposit, South Australia

    International Nuclear Information System (INIS)

    An ore microscopic examination of 80 polished sections prepared from selected drill core specimens from the Boss-Bixby, Missouri copper-iron deposit has shown that its mineral assemblage is similar to that of the Olympic Dam (Roxby Downs) copper-uranium-gold deposit in South Australia. A comparison with the mineralogy reported for Olympic Dam shows that both deposits contain: 1) the principal minerals, magnetite, hematite, chalcopyrite, and bornite, 2) the cobalt-bearing phases, carrollite and cobaltian pyrite, 3) the titanium oxides, rutile and anatase, 4) smaller amounts of martite, covellite, and electrum, 5) fluorite and carbonates, and 6) some alteration minerals. The deposits also are similar with regard to the sequence of mineral deposition: 1) early oxides, 2) then sulfide minerals, and 3) a final oxide generation. The deposits, however, are dissimilar with regard to their host rock lithologies and structural settings. The Boss-Bixby ores occupy breccia zones within a hydrothermally altered basic intrusive and intruded silicic volcanics, whereas the Olympic Dam ores are contained in sedimentary breccias in a graben or trough. Also, some minerals have been found thus far to occur at only one of the deposits. The similarity of mineralogy in these deposits suggests that they were formed from ore fluids that had some similarities in character and that the St. Francois terrane of Missouri is an important region for further exploration for deposits with this mineral assemblage

  8. Multi-episode fluid boiling in the Shizishan copper-gold deposit at Tongling, Anhui Province: its bearing on oreformation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Shizishan copper-gold deposit at Tongling, Anhui Province consists of two magmato-hydrothermal mineralization types: the crypto-explosive breccia type and the skarn type. At least four episodes of boiling occurred to the ore-forming fluids in this deposit. The first episode took place in accompany with the formation of the crypto-explosive breccias. The melt-fluid inclusions giving temperatures above 600℃ and salinities higher than 42% NaCl equiv represent a residual magma related to this episode. The second episode occurred during skarnization, giving fluid temperatures of 422℃-472℃, averaging 458℃, and salinities of 10.2%-45.1% NaCl equiv. The third episode corresponds to the main mineralization stage, i.e., the quartz-sulphide stage. Fluid temperatures of this episode vary in a range of 337℃-439℃ with an average of 390℃, and salinities in a range of 3%-30% NaCl equiv. The forth episode happened at the waning stage of mineralization, giving fluid temperatures below 350℃ with an average of 265℃ and salinities of 2.1%-40.4% NaCl equiv.

  9. A subaqueous eruption model for shallow-water, small volume eruptions: Evidence from two Precambrian examples

    Science.gov (United States)

    Mueller, Wulf U.

    Ancient, shallow-water, pyroclastic deposits are identified in the Paleoproterozoic Ketilidian Mobile belt, southeast Greenland at Kangerluluk and in the Neoproterozoic Gariep belt of Namibia in the Schakalsberg Mountains. The 1-30 m-thick tuff and lapilli tuff deposits are interpreted as eruption-fed density current deposits emanating from tephra jets that collapsed under subaqueous conditions due to water ingress. The presence of 1-10 mm diameter armoured lapilli, with a central vesicular lapillus or shard, suggests the existence of high velocity, gas, water vapour, and particle-rich tephra jets. A transition from a gas-steam supported tephra jet to a cold water-laden density current without an intermediate stage of storage and remobilization is inferred. Interpretation of a 5-15 m-thick lapilli tuff breccia further supports explosive subaqueous mechanisms. Pyroclasts in the lapilli tuff breccia are interpreted as bombs emplaced ballistically. Multiple bomb sags produced by the impact of rounded juvenile crystal-rich pyroclasts required a water-exclusion zone formed either by a continuous magma uprush or multiple jet activity occurring concurrently, rather than as isolated tephra jets. Intercalated density current deposits indicate uprush events of limited duration and their recurrence with rapid collapse after each pulse. A new subaqueous Surtseyan-type eruption model is proposed based on observations from these two Precambrian study areas.

  10. Sedimentación pedemontana en las nacientes delRío Jáchal y Pampa de Gualilán, Precordillera de San Juan Piedmont sedimentation in the headwaters of theRío Jachal and Pampa de Gualilán, Precordillera of San Juan

    Directory of Open Access Journals (Sweden)

    Julieta Suriano

    2009-11-01

    dominantemente local presentan mayor variabilidad litológica que losambientes antes mencionados. El análisis comparativo de los piedemontesencontrados en los distintos valles analizados, permite proponer un modeloconceptual de clasificación de piedemontes en cuencas intramontanas basado enextensión de las cuencas y en el espacio vertical de acomodación desedimentos.This paper deals with the sedimentological characteristics ofpiedmont deposits exposed in intramontane basins of the Precordillera. Detailedstudies carried out along the upper Jáchal river and in the Gualilán areaallowed identifying and characterizing six major types of piedmontaccumulations: 1 talus, 2 colluvial fans dominated by gravity flows, 3colluvial fans dominated by fluid flows, 4 collector-conoid fluvial system, 5piedmonts dominated by channalized flows and 6 alluvial fans. The talusdeposits are characterized by the dominance of clast-supported breccias(bearing minimum matrix amounts that commonly exhibit massive bedding, planaror high angle imbricated clasts fabric. Colluvial fans dominated by gravityflows are formed by massive matrix-supported breccias with minor percentages ofclast-supported breccias. On the contrary, colluvial fans dominated by fluidflows are composed of amalgamated channels infilled by both clast- andmatrix-supported breccias together with intercalation of graded breccias.Accumulations of the collector-conoid fluvial systems are the most diverse incomposition, including from massive matrix-supported breccias to cross-beddedconglomerates and scarce mudstones. In relation to the piedmont dominated bychannalized flows, they comprise massive clast-supported breccias and lessamounts of imbricated or cross-bedded ones. The alluvial fan deposits aremostly composed of cross-bedded clast-supported conglomerates, thoughmatrix-supported conglomerates and breccias also appear as proximal deposits.Different from the previously mentioned deposits, the clast of alluvial fanaccumulations shows

  11. Mineral resources of the South Mccullough Mountains Wilderness Study Area, Clark County, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    DeWitt, E.; Anderson, J.L.; Barton, H.N.; Jachens, R.C.; Podwysocki, M.H.; Brickey, D.W. (U.S. Geological Survey (US)); Close, T.J. (U.S. Bureau of Mines (US))

    1989-01-01

    The authors present a study of 19,558 acres of the South McCullough Mountains Wilderness Study Area. The study area contains no identified mineral resources and has no areas of high mineral resource potential. However, five areas that make up 20 percent of the study area have a moderate potential either for undiscovered silver, gold, lead, copper, and zinc resources in small vein deposits; for lanthanum and other rare-earth elements, uranium, thorium, and niobium in medium-size carbonatite bodies and dikes; for tungsten and copper in small- to medium-size vein deposits; or for silver and gold in small vein or breccia-pipe deposits. Six areas that makeup 24 percent of the study area have an unknown resource potential either for gold, silver, lead, and copper in small vein deposits; for gold, silver, lead, zinc, copper, and arsenic in small vein or breccia-pipe deposits; for lanthanum and other rare-earth elements, uranium, thorium, and niobium in medium-size carbonatite bodies and dikes; or for tungsten and copper in small vein deposits.

  12. Geology and mining development of the C-09 uranium deposit

    International Nuclear Information System (INIS)

    The uranium deposit at Campo do Cercado is the first one in Brazil to reach the stage of mining operations. Located in the alkaline volcanic complex of Pocos de Caldas, the deposit is divided into three ore bodies which lie at the edge of a secondary crater in the caldera. Uranium ore occurs in the primary form in association with volcanic breccia belts (body A), as well as a result of hydrothermal action (body B); it is also present in the secondary form (body E) as a product of the leaching of the breccia belts by the oxidation front, followed by concentration and deposition in a reduction zone. The mineralization takes the form of black uranium oxides (UO2/UO3), and, more rarely, coffinite. Pyrite, galena and fluorite are almost always present. Molybdenum is also found in close association with the uranium ore in quantities considered economically viable. The ore reserves of the Pocos de Caldas plateau are estimated at 26,800 t. (author)

  13. Carbonate Cements from the Sverrefjell and Sigurdfjell Volcanoes, Svalbard Norway: Analogs for Martian Carbonates

    Science.gov (United States)

    Blake, D. F.; Treiman, A. H.; Morris, R.; Bish, D.; Amundsen, H.E.F.; Steele, A.

    2011-01-01

    The Sverrefjell and Sigurdfjell volcanic complexes erupted at 1Ma on Svalbard, Norway. Sverrefjell is a cone of cinders, pillow lavas and dikes; Sigurdfjell is elongate in outcrop and may represent a fissure eruption [1]. The lavas of both volcanos were volatile rich. The volcanos erupted under ice and were subsequently dissected by glaciation (glacial eratics are present on most of Sverrefjell, even on its summit). Eruption beneath an ice sheet is inferred, based on the presence of pillow lavas from near sea level to 1000 m above sea level. Sverrefjell contains the largest fraction of ultramafic xenoliths of any volcanic complex in the world, in places accounting for as much as 50% of the volume of the outcrop. The Sverrefjell and Sigurdfell volcanos contain carbonate cements of several varieties: (1) Amundsen [2] reported Mg-Fe-rich carbonate in sub-mm globules in basalts and ultramafic xenoliths from the volcanos. These globules are the best terrestrial analogs to the carbonate globules in the Mars meteorite ALH84001 [3]. (2) Thick (1-3 cm) coatings of carbonate cement drape the walls of vertical volcanic pipes or conduits on the flanks and near the present summit of Sverrefjell. Similar occurrences are found on Sigurdfjell. (3) Breccia-filled pipes or vents occur on Sverrefjell and Siggurdfjell in which the breccia fragments are cemented by carbonate. The fragments themselves commonly contain carbonate globules similar to those found in the basalts and ultramafic xenoliths.

  14. Characteristics of a ridge-transform inside corner intersection and associated mafic-hosted seafloor hydrothermal field (14.0°S, Mid-Atlantic Ridge)

    Science.gov (United States)

    Li, Bing; Yang, Yaomin; Shi, Xuefa; Ye, Jun; Gao, Jingjing; Zhu, Aimei; Shao, Mingjuan

    2014-03-01

    Morphotectonic analysis of the inside corner intersection (14.0°S) between the southern Mid-Atlantic Ridge and the Cardno fracture zone indicate a young rough massif emerging after the termination of a previous oceanic core complex. The massif, which hosts an off-axis hydrothermal field, is characterized by a magmatic inactive volcanic structure, based on geologic mapping and sample studies. Mineralogical analyses show that the prominent hydrothermal deposit was characterized by massive pyrite-marcasite breccias with silica-rich gangue minerals. Geochemical analyses of the sulfide breccias indicate two element groups: the Fe-rich ore mineral group and silica-rich gangue mineral group. Rare earth element distribution patterns showing coexistence of positive Eu anomalies and negative Ce anomalies suggest that sulfides were precipitated from diffused discharge resulted from mixing between seawater and vent fluids. Different from several low temperature hydrothermal systems occurring on other intersection dome-like massifs that are recognized as detachment fault surfaces associated with variably metamorphosed ultramafic rocks, the 14.0°S field, hosted in gabbroic-basaltic substrate, is inferred to be of a high temperature system and likely to be driven by deep high temperature gabbroic intrusions. Additionally, the subsurface fossil detachment fault is also likely to play an important role in focusing hydrothermal fluids.

  15. Determination of ancient volcanic eruption center based on gravity methods (3D) in Gunungkidul area Yogyakarta, Indonesia

    Science.gov (United States)

    Santoso, Agus; Sismanto, Setiawan, Ary; Pramumijoyo, Subagyo

    2016-05-01

    Ancient eruption centers can be determined by detecting the position of the ancient volcanic material, it is important to understand the elements of ancient volcanic material by studying the area geologically and prove the existence of an ancient volcanic eruption centers using geophysics gravity method. The measuring instrument is Lacoste & Romberg gravimeter type 1115, the number of data are 900 points. The area 60×40 kilometers, the modeling 3D software is reaching depth of 15 km at the south of the island of Java subduction zone. It is suported by geological data in the field that are found as the following: 1. Pyroclastic Fall which is a product of volcanic eruptions, and lapilli tuff with felsic mineral. 2. Pyroclastic flow with Breccia, tuffaceous sandstone and tuff breccia. 3. Hot springs near Parangwedang Parangtritis. 4. Igneous rock with scoria structure in Parang Kusumo, structured amigdaloida which is the result of the eruption of lava/volcanic eruptions, and Pillow lava in the shows the flowing lava into the sea. Base on gravity anomaly shows that there are strong correlationship between those geological data to the gravity anomaly. The gravblox modeling (3D) shows the position of ancient of volcanic eruption in this area clearly.

  16. Search for a meteoritic component in drill cores from the Bosumtwi impact structure, Ghana: Platinum group element contents and osmium isotopic characteristics

    Science.gov (United States)

    McDonald, Iain; Peucker-Ehrenbrink, Bernhard; Coney, Louise; Ferrière, Ludovic; Reimold, Wolf Uwe; Koeberl, Christian

    An attempt was made to detect a meteoritic component in both crater-fill (fallback) impact breccias and fallout suevites (outside the crater rim) at the Bosumtwi impact structure in Ghana. Thus far, the only clear indication for an extraterrestrial component related to this structure has been the discovery of a meteoritic signature in Ivory Coast tektites, which formed during the Bosumtwi impact event. Earlier work at Bosumtwi indicated unusually high levels of elements that are commonly used for the identification of meteoritic contamination (i.e., siderophile elements, including the platinum group elements [PGE]) in both target rocks and impact breccias from surface exposures around the crater structure, which does not allow unambiguous verification of an extraterrestrial signature. The present work, involving PGE abundance determinations and Os isotope measurements on drill core samples from inside and outside the crater rim, arrives at the same conclusion. Despite the potential of the Os isotope system to detect even small amounts of extraterrestrial contribution, the wide range in PGE concentrations and Os isotope composition observed in the target rocks makes the interpretation of unradiogenic, high-concentration samples as an impact signature ambiguous.

  17. New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan

    Science.gov (United States)

    Granger, Darryl E.; Gibbon, Ryan J.; Kuman, Kathleen; Clarke, Ronald J.; Bruxelles, Laurent; Caffee, Marc W.

    2015-06-01

    The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 (`Little Foot') in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium-lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence. Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking. Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 +/- 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa. We also date the earliest stone tools at Sterkfontein to 2.18 +/- 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans and Wonderwerk.

  18. On the crypto-explosive crater and its relation with gold mineralization in larma Au-U deposit

    International Nuclear Information System (INIS)

    A new type of gold mineralization-controlling structure-hydrothermal crypto-explosive crater was identified at the Larma gold-uranium deposit in the border regions between Gansu and Sichuan provinces, western China. The hydrothermal crypto-explosive crater is ellipse-shaped at the surface, while funnel-like in profile. A silica-cap composed of hydrothermal siliceous breccia is distributed at the top of the crater, while hydrothermal crypto-explosive breccia are in the centre. The configuration of the crater is roughly consistent with the distribution of gold ore bodies. The formation mechanism of the crater is: first, a silica cap composed of hydrothermal siliceous metasomatic rock was formed at the contact area between the siliceous rock and the slate, and blocked the movement of hydrothermal fluid and resulted in the appearance of over-pressed geothermal environment. Then, at 49.5 Ma, the rejuvenation of the EW-striking faults in larma area resulted in the breaking of the brittle silica cap, followed by the crypto-explosion of hydrothermal fluid. In Larma gold-uranium deposit, the hydrothermal crypto-explosion gave rise to the precipitation of gold from the hydrothermal fluid, while the crypto-explosive crater provided the space for gold mineralization

  19. Karst features detection and mapping using airphotos, DSMs and GIS techniques

    Science.gov (United States)

    Kakavas, M. P.; Nikolakopoulos, K. G.; Zagana, E.

    2015-10-01

    The aim of this work is to detect and qualify natural karst depressions in the Aitoloakarnania Prefecture, Western Greece, using remote sensing data in conjunction with the Geographical Information Systems - GIS. The study area is a part of the Ionian geotectonic zone, and its geological background consists of the Triassic Evaporates. The Triassic carbonate breccias where formed as a result of the tectonic and orogenetic setting of the external Hellenides and the diaper phenomena of the Triassic Evaporates. The landscape characterized by exokarst features closed depressions in the Triassic carbonate breccias. At the threshold of this study, an in situ observation was performed in order to identify dolines and swallow holes. The creation of sinkholes, in general, is based on the collapse of the surface layer due to chemical dissolution of carbonate rocks. In the current study airphotos stereopairs, DSMs and GIS were combined in order to detect and map the karst features. Thirty seven airphotos were imported in Leica Photogrammetry Suite and a stereo model of the study area was created. Then in 3D view possible karst features were detected and digitized. Those sites were verified during the in situ survey. ASTER GDEM, SRTM DEM, high resolution airphoto DSM created from the Greek Cadastral and a DEM from digitized contours from the 1/50,000 topographic were also evaluated in GIS environment for the automatic detection of the karst depressions. The results are presented in this study.

  20. REPRISK-PC, Radioactive Waste Storage Risk Assessment

    International Nuclear Information System (INIS)

    A - Description of program or function: REPRISK-PC is a PC version of the REPRISK model used in the modelling of long-term radionuclide releases and population health effects resulting from disposal of high level radioactive wastes in mined geological repositories. REPRISK is a set of computer programs and databases that models the transport of radionuclides from the repository through the environment to exposed human populations and estimates the resulting health impact. B - Method of solution: Various natural processes or human activities could lead to radionuclide releases from a geological repository after it has been closed. These perturbations happen according to some frequency or probability. REPRISK-PC incorporates the characteristics of these perturbations and their associated probability. REPRISK-PC models four release scenarios: (1) direct impact of a waste package - releases to air and land surface (volcano, meteorite, drilling/direct hit); (2) direct impact of a waste package - releases to an aquifer (faulting, breccia pipes); (3) disruption of the repository - releases to land (drilling/no hit); (4) disruption of the repository - releases to an aquifer (normal groundwater flow, faulting, breccia pipes, drilling/no hit). C - Restrictions on the complexity of the problem: REPRISK-PC does not model the differences in radionuclide-specific velocities, which may control the travel time from repository to the accessible environment. It is not a good model for time periods greater than 10,000 years when radium daughters become important

  1. Abundance and distribution of ultramafic microbreccia in Moses Rock Dike: Quantitative application of AIS data

    Science.gov (United States)

    Mustard, John F.; Pieters, Carle M.

    1987-01-01

    Moses Rock dike is a Tertiary diatreme containing serpentinized ultramafic microbreccia (SUM). Field evidence indicates the SUM was emplaced first followed by breccias derived from the Permian strata exposed in the walls of the diatreme and finally by complex breccias containing basement and mantle derived rocks. SUM is found primarily dispersed throughout the matrix of the diatreme. Moses Rock dike was examined with Airborne Imaging Spectrometer (AIS) to map the distribution and excess of SUM in the matrix and to better understand the nature of the eruption which formed this explosive volcanic feature. AIS data was calibrated by dividing the suite of AIS data by data from an internal standard area and then multiplying this relative reflectance data by the absolute bidirectional reflectance of a selected sample from the standard area which was measured in the lab. From the calibrated AIS data the minerals serpentine, gypsum, and illite as well as desert varnish and the lithologies SUM and other sandstones were identified. SUM distribution and abundance in the matrix of the diatreme were examined in detail and two distinct styles of SUM dispersion were observed. The two styles are discussed in detail.

  2. LITHOSTRATIGRAPHY AND FACIES ARCHITECTURE OF THE OLIGOCENE CONGLOMERATES AT MONTE PAREI (FANES. DOLOMITES, ITALY

    Directory of Open Access Journals (Sweden)

    LORENZ KEIM

    2000-03-01

    Full Text Available The only occurrence of Tertiary (Oligocene sediments in the Dolomites at Monte Parei results from a complex tectonic and sedimentary history. The Tertiary marine clastic succession is sealing the Dinaric (Late Cretaceous to Paleogene deformed basement. The basin-fill can be differentiated into four lithofacies which show extensive lateral interfingering: ,local scarp breccias with giant blocks (facies A, chaotic breccias of debris flow origin (facies B, balanid and shell coquina beds (facies C and conglomeratic grain and debris flows with sandstone intercalations (facies D. Transport directions (imbricate clasts and cross bedding and petrographic composition indicate two different source areas. Sediments of facies B were shed from a structural high in the SW, while carbonate-siliciclastic debris of facies C and D originated from a pebbly or rocky shore in the N. Lithofacies and facies interrelationships clearly indicate the control by synsedimentary tectonic activity. Neoalpine closure of the basin by overthrusting lead to the preservation of the sediments. 

  3. Connecting Lunar Meteorites to Source Terrains on the Moon

    Science.gov (United States)

    Jolliff, B. L.; Carpenter, P. K.; Korotev, R. L.; North-Valencia, S. N.; Wittmann, A.; Zeigler, R. A.

    2014-01-01

    The number of named stones found on Earth that have proven to be meteorites from the Moon is approx. 180 so far. Since the Moon has been mapped globally in composition and mineralogy from orbit, it has become possible to speculate broadly on the region of origin on the basis of distinctive compositional characteristics of some of the lunar meteorites. In particular, Lunar Prospector in 1998 [1,2] mapped Fe and Th at 0.5 degree/pixel and major elements at 5 degree/pixel using gamma ray spectroscopy. Also, various multispectral datasets have been used to derive FeO and TiO2 concentrations at 100 m/pixel spatial resolution or better using UV-VIS spectral features [e.g., 3]. Using these data, several lunar meteorite bulk compositions can be related to regions of the Moon that share their distinctive compositional characteristics. We then use EPMA to characterize the petrographic characteristics, including lithic clast components of the meteorites, which typically are breccias. In this way, we can extend knowledge of the Moon's crust to regions beyond the Apollo and Luna sample-return sites, including sites on the lunar farside. Feldspathic Regolith Breccias. One of the most distinctive general characteristics of many lunar meteorites is that they have highly feldspathic compositions (Al2O3 approx. 28% wt.%, FeO Moon's farside highlands, the Feldspathic Highlands Terrane, which are characterized by low Fe and Th in remotely sensed data [4]. The meteorites provide a perspective on the lithologic makeup of this part of the Moon, specifically, how anorthositic is the surface and what, if any, are the mafic lithic components? These meteorites are mostly regolith breccias dominated by anorthositic lithic clasts and feldspathic glasses, but they do also contain a variety of more mafic clasts. On the basis of textures, we infer these clasts to have formed by large impacts that excavated and mixed rocks from depth within the lunar crust and possibly the upper mantle. One of the

  4. Fluorapatite in carbonatite-related phosphate deposits: the case of the Matongo carbonatite (Burundi)

    Science.gov (United States)

    Decrée, Sophie; Boulvais, Philippe; Tack, Luc; André, Luc; Baele, Jean-Marc

    2016-04-01

    The Matongo carbonatite intrusive body in the Neoproterozoic Upper Ruvubu alkaline plutonic complex (URAPC) in Burundi is overlain by an economic phosphate ore deposit that is present as breccia lenses. The ore exhibits evidence of supergene enrichment but also preserves textures related to the concentration of fluorapatite in the carbonatitic system. Magmatic fluorapatite is abundant in the ore and commonly occurs as millimeter-sized aggregates. It is enriched in light rare earth elements (LREE), which is especially apparent in the final generation of magmatic fluorapatite (up to 1.32 wt% LREE2O3). After an episode of metasomatism (fenitization), which led to the formation of K-feldspar and albite, the fluorapatite-rich rocks were partly brecciated. Oxygen and carbon isotope compositions obtained on the calcite forming the breccia matrix (δ18O = 22.1 ‰ and δ13C = -1.5 ‰) are consistent with the involvement of a fluid resulting from the mixing of magmatic-derived fluids with a metamorphic fluid originating from the country rocks. In a subsequent postmagmatic event, the carbonates hosting fluorapatite were dissolved, leading to intense brecciation of the fluorapatite-rich rocks. Secondary carbonate-fluorapatite (less enriched in LREE with 0.07-0.24 wt% LREE2O3 but locally associated with monazite) and coeval siderite constitute the matrix of these breccias. Siderite has δ18O values between 25.4 and 27.7 ‰ and very low δ13C values (from -12.4 to -9.2 ‰), which are consistent with the contribution of organic-derived low δ13C carbon from groundwater. These signatures emphasize supergene alteration. Finally, the remaining voids were filled with a LREE-poor fibrous fluorapatite (0.01 wt% LREE2O3), forming hardened phosphorite, still under supergene conditions. Pyrochlore and vanadiferous magnetite are other minerals accumulated in the eluvial horizons. As a consequence of the supergene processes and fluorapatite accumulation, the phosphate ore, which

  5. Aqueous Alteration of Endeavour Crater Rim Apron Rocks

    Science.gov (United States)

    Ming, D. W.; Mittlefehldt, D. W.; Gellert, R.; Clark, B. C.; Morris, R. V.; Yen, A. S.; Arvidson, R. E.; Crumpler, L. S.; Farrand, W. H.; Grant, J. A., III; Jolliff, B. L.; Parker, T. J.; Peretyazhko, T.

    2014-12-01

    Mars Exploration Rover Opportunity is exploring Noachian age rocks of the rim of 22 km diameter Endeavour crater. Overlying the pre-impact lithologies and rim breccias is a thin apron of fine-grained sediments, the Grasberg fm, forming annuli on the lower slopes of rim segments. Hesperian Burns fm sandstones overly the Grasberg fm. Grasberg rocks have major element compositions that are distinct from Burns fm sandstones, especially when comparing interior compositions exposed by the Rock Abrasion Tool. Grasberg rocks are also different from Endeavour rim breccias, but have general compositional similarities to them. Grasberg sediments are plausibly fine-grained materials derived from the impact breccias. Veins of CaSO4 transect Grasberg fm rocks demonstrating post-formation aqueous alteration. Minor/trace elements show variations consistent with mobilization by aqueous fluids. Grasberg fm rocks have low Mn and high Fe/Mn ratios compared to the other lithologies. Manganese likely was mobilized and removed from the Grasberg host rock by redox reactions. We posit that Fe2+ from acidic solutions associated with formation of the Burns sulfate-rich sandstones acted as an electron donor to reduce more oxidized Mn to Mn2+. The Fe contents of Grasberg rocks are slightly higher than in other rocks suggesting precipitation of Fe phases in Grasberg materials. Pancam spectra show that Grasberg rocks have a higher fraction of ferric oxide minerals than other Endeavour rim rocks. Solutions transported Mn2+ into the Endeavour rim materials and oxidized and/or precipitated it in them. Grasberg has higher contents of the mobile elements K, Zn, Cl, and Br compared to the rim materials. Similar enrichments of mobile elements were measured by the Spirit APXS on West Spur and around Home Plate in Gusev crater. Enhancements in these elements are attributed to interactions of hydrothermal acidic fluids with the host rocks. Interactions of fluids with the Grasberg fm postdate the genesis

  6. Age determination and development of experimental methods for quaternary fault and formation

    International Nuclear Information System (INIS)

    Correlation of palaeo-shoreline elevations indicates that the MQt4 terrace in Suryum site has formed during MIS 5e, which is supported by stratigraphically concordant OSL ages for NQt3 terrace sediments in Yonghan area. Sedimentological features of the trench site of the Eupcheon fault suggest multiple fault movements during the Late Quaternary. All of these observations imply that uplift rate in the middle part of the coast has been much larger than that in the northern part during 125 ka ∼ 80 ka, requiring the revision of conventional view that the Korean peninsula is tectonically very stable. The ESR data suggest that the Ilkwang fault zone has been formed by the initial surface fault activity at 2-3 Ma and reactivated at least 4 times at 1.2-1.3 Ma, 1 Ma, 0.6 Ma and 0.5 Ma, with part of adjacent NNE and NE trending faults. The Eupcheon fault has been reactivated along the boundary between fault breccia originated from Cretaceous sedimentary rocks and Tertiary lithic tuff at around 2 Ma, 1.3 Ma, and 1 Ma. It has been reactivation again along the boundary between Cretaceous sandstone and fault breccia at 0.8 Ma, and between fault breccia and Tertiary lithic tuff at 0.6 Ma. During the late Quaternary after MIS 5e, the Eupcheon fault reactivated along the boundary between fault gouges, cutting Quaternary marine terrace deposits. The ESR data for the Eupcheon fault, however, should be carefully reexamined because it is probable that the samples contain clay components of weathering, not cataclastic origin. A weathering profile developed in the Suryum site was disturbed by tectonic movement that appears to be a simple one-time reverse faulting event based on field observations. A comparative analysis of the mineralogy, micromorphology, and chemistry of the weathering profile and fault gouge, however, reveals that both the microfissures in the deformed weathering profile and larger void spaces along the fault plane were filled with multi-stage accumulations of

  7. Waduk Parangjoho dan Songputri: Alternatif Sumber Erupsi Formasi Semilir di daerah Eromoko, Kabupaten Wonogiri, Jawa Tengah

    Directory of Open Access Journals (Sweden)

    Sutikno Bronto

    2014-06-01

    Full Text Available http://dx.doi.org/10.17014/ijog.vol4no2.20091The Semilir Formation was typically originated from products of a very explosive volcanic activity, i.e. breccias, lapillistones, and tuffs containing abundant pumice. It has a light grey to white colour and high silica andesite to dacite in composition, mainly rich in volcanic glass and quartz. Sedimentary structures of these volcanic rocks are massive, grading, planar bedding, and cross-bedding to antidunes, with grain size varies from ash (≤ 2 mm to lapilli (2 – 64 mm to bomb and block (> 64 mm. The formation is widely distributed from the west side (Pleret and Piyungan areas, Bantul Regency, Special Province of Yogyakarta until Eromoko area in the east (Wonogiri Regency, Jawa Tengah Province. Stratigraphically, the Semilir Formation underlies the Nglanggeran Formation, and overlies the Mandalika Formation in the eastern part and Kebo-Butak Formation in the western part. Geomorphological- and lithological analyses of the Semilir Formation in areas of Parangjoho and Song- putri Dams, Eromoko Sub-regency, Wonogiri Regency indicate that the two depressions were alternatively volcanic sources of the Semilir Formation in the Eromoko area. This is proved by the presence of co-ignimbrite breccias(co-ignimbrite lag fall deposits, that descriptively they are polymict breccias. This rock is characterized by a mixing of pumice and various hard rock fragments that primarily are juvenile materials (volcanic blocks, bombs, accessory-, and accidental rock fragments set in pumice-rich volcanic ash and lapilli sizes. The accessory materials came from older volcanic rocks, whereas the accidental ones were originated from basement rocks. During a caldera forming event or a destruction period of an older composite volcanic cone(s, all older rocks resting above the magma chamber were ejected to the surface by a very high magmatic pressure. Since they were heavier than the juvenile material, most accessory and

  8. Insights into the Martian Regolith from Martian Meteorite Northwest Africa 7034

    Science.gov (United States)

    McCubbin, Francis M.; Boyce, Jeremy W.; Szabo, Timea; Santos, Alison R.; Domokos, Gabor; Vazquez, Jorge; Moser, Desmond E.; Jerolmack, Douglas J.; Keller, Lindsay P.; Tartese, Romain

    2015-01-01

    Everything we know about sedimentary processes on Mars is gleaned from remote sensing observations. Here we report insights from meteorite Northwest Africa (NWA) 7034, which is a water-rich martian regolith breccia that hosts both igneous and sedimentary clasts. The sedimentary clasts in NWA 7034 are poorly-sorted clastic siltstones that we refer to as protobreccia clasts. These protobreccia clasts record aqueous alteration process that occurred prior to breccia formation. The aqueous alteration appears to have occurred at relatively low Eh, high pH conditions based on the co-precipitation of pyrite and magnetite, and the concomitant loss of SiO2 from the system. To determine the origin of the NWA 7034 breccia, we examined the textures and grain-shape characteristics of NWA 7034 clasts. The shapes of the clasts are consistent with rock fragmentation in the absence of transport. Coupled with the clast size distribution, we interpret the protolith of NWA 7034 to have been deposited by atmospheric rainout resulting from pyroclastic eruptions and/or asteroid impacts. Cross-cutting and inclusion relationships and U-Pb data from zircon, baddelleyite, and apatite indicate NWA 7034 lithification occurred at 1.4-1.5 Ga, during a short-lived hydrothermal event at 600-700 C that was texturally imprinted upon the submicron groundmass. The hydrothermal event caused Pb-loss from apatite and U-rich metamict zircons, and it caused partial transformation of pyrite to submicron mixtures of magnetite and maghemite, indicating the fluid had higher Eh than the fluid that caused pyrite-magnetite precipitation in the protobreccia clasts. NWA 7034 also hosts ancient 4.4 Ga crustal materials in the form of baddelleyites and zircons, providing up to a 2.9 Ga record of martian geologic history. This work demonstrates the incredible value of sedimentary basins as scientific targets for Mars sample return missions, but it also highlights the importance of targeting samples that have not been

  9. Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean

    Science.gov (United States)

    López-Rodríguez, C.; Stadnitskaia, A.; De Lange, G. J.; Martínez-Ruíz, F.; Comas, M.

    2014-06-01

    Mud volcanoes (MVs) are the most prominent indicators of active methane/hydrocarbon venting at the seafloor on both passive and active continental margins. Their occurrence in the western Mediterranean is patent at the West Alboran Basin, where numerous MVs develop overlaying a major sedimentary depocentre containing overpressured shales. Although some of these MVs have been studied, the detailed biogeochemistry of expelled mud so far has not been examined in detail. This work provides the first results on the composition and origin of organic matter, anaerobic oxidation of methane (AOM) processes and general characteristics on MV dynamics using lipid biomarkers as the main tool. Lipid biomarker analysis was performed on MV expelled material (mud breccias) and interbedded hemipelagic sediments from Perejil, Kalinin and Schneider's Heart MVs located in the northwest margin of the Alboran Sea. The n alkane distributions and n alkane-derived indices (CPI and ACL), in combination with the epimerization degree of hopanes (22S/(22S+22R)) indicate that all studied mud breccia have a similar biomarker composition consisting of mainly thermally immature organic matter with an admixture of petroleum-derived compounds. This concordant composition indicates that common source strata must feed all three studied MVs. The past or present AOM activity was established using lipid biomarkers specific for anaerobic methanotrophic archaea (irregular isoprenoids and dialkyl glycerol diethers) and the depleted carbon isotope composition (δ13C) of crocetane/phytane. The presence of these lipid biomarkers, together with the low amounts of detected glycerol dialkyl glycerol tetraethers, is consistent with the dominance of anaerobic methanotrophs of the ANME-2 over ANME-1, at least in mud breccia from Perejil MVs. In contrast, the scarce presence or lack of these AOM-related lipid biomarkers in sediments from Kalinin and Schneider's Heart MVs, suggests that no recent active methane seepage

  10. Magnetic susceptibility experimental study of the rocks from north-western part of Dnieper-Donets depression

    International Nuclear Information System (INIS)

    Complete text of publication follows. Magnetic susceptibility χ of the sedimentary and effusive Devonian and Carbonian rocks from 8 bore-holes of north-western part of Dnieper-Donets depression was investigated. There are argillits, aleurolites, sandstones, limestones, anhydrites, salt, tuff breccias, tuff sandstones, marls, dolomitic limestones, basalts. The crystalline basement (Precambrian) is presented by gneisses and granite-gneisses from Stroyivska bore-hole (2976-3803m). Oil and gas perspectives are connected with Devonian deposits. Magnetic susceptibility values of the rocks vary in wide interval: from 5,4 x 10-5 Si (Zorkivska) to 921 x 10-5 Si (Borkivska) for argillites; from 7 x 10-5 Si (Nizhynska) to 11450 x 10-5 Si (Borkivska) for aleurolites; from 3,9 x 10-5 Si to 207 x 10-5 Si for limestones; about 0 (Zorkivska) for anhydrite; from 1,7 x 10-5 Si (Guzhivska) to 11666 x 10-5 Si (Borkivska) for sandstones. Tuff breccias are characterized by χ of only 13 x 10-5 Si and 80 x 10-5 Si. Magnetic susceptibility of basalt is high enough - 11110 x 10-5 Si. Low values of magnetic susceptibility characterize gneisses (from 17 x 10-5 Si to 51 x 10-5 Si) and granite-gneiss (about 41 x 10-5 Si). The temperature influence on magnetic susceptibility of the rocks was researched. We made a pair from each sample for laboratory experiments. One of them was saturated by gasoline during 1 month the other remained dry. Samples magnetic susceptibility in dependence on temperature with the purpose of accelerating any processes taking place in them was measured. Step of heating was 50 deg C (from 100 deg C to 350 deg C). Magnetic susceptibility was measured on the astatic magnetometer and on the magnetic susceptibility bridge. As a result graphs of absolute values of magnetic susceptibility in dependence on the temperature were received. After experiment we can confirm that only in a small number of gasoline-saturated samples magnetic susceptibility increase (argillites

  11. CO2 outburst events in relation to seismicity: Constraints from microscale geochronology, geochemistry of late Quaternary vein carbonates, SW Turkey

    Science.gov (United States)

    Ünal-İmer, Ezgi; Uysal, I. Tonguç; Zhao, Jian-Xin; Işık, Veysel; Shulmeister, James; İmer, Ali; Feng, Yue-Xing

    2016-08-01

    Vein and breccia carbonates precipitated in a highly fractured/faulted carbonate bedrock in SW Turkey were investigated through high-resolution U-series geochronology, microstructural and geochemical studies including C-O-Sr isotope and rare-earth element and yttrium (REY) analyses. Petrographical observations and geochronological data are interpreted as evidence that the calcite veins formed through a crack-seal mechanism, mostly accompanied/initiated by intensive hydraulic fracturing of the host limestone in response to high-pressure fluids, which is manifested by multi-stage breccia deposits. Microscale U-series dates (272.6-20.5 kyr) and geochemical compositions of the vein/breccia samples provide information on the timing and mechanism of the vein formation and identify the source of CO2-bearing fluids responsible for the carbonate precipitation. δ18OVPDB and δ13CVPDB values of the calcite veins range between -5.9 and -1.7‰, and -10.6 and -4.6‰, respectively. The isotopic compositions of the veins show highly fluctuating values as calcite grew successively perpendicular to vein walls, which, in combination with microstructural and geochronological constraints, are interpreted to reflect episodic CO2 degassing events associated with seismic and aseismic deformation. Oxygen and Sr isotope compositions (δ18OVPDB: -5.9 to -1.7‰; 87Sr/86Sr: 0.7082 to 0.7085) together with REY concentrations indicate deep infiltration of meteoric waters with various degrees of interactions mostly with the host limestone and siliciclastic parts of the basement rocks. Oxygen and carbon isotope compositions suggest CO2 degassing through intensive limestone dissolution. While majority of the veins display similar Post-Archaean Australian Shale (PAAS)-normalised REY variations, some of the veins show positive EuPAAS anomalies, which could be indicative of contributions from a deeply derived, heated, and reduced fluid component, giving rise to multiple fluid sources for the

  12. Uranium-rich opal from the Nopal I uranium deposit, Peña Blanca, Mexico: Evidence for the uptake and retardation of radionuclides

    Science.gov (United States)

    Schindler, Michael; Fayek, Mostafa; Hawthorne, Frank C.

    2010-01-01

    The Nopal I uranium deposit of the Sierra Peña Blanca, Mexico, has been the focus of numerous studies because of its economic importance and its use as a natural analog for nuclear-waste disposal in volcanic tuff. Secondary uranyl minerals such as uranophane, Ca[(UO 2)(SiO 3OH)] 2(H 2O) 5, and weeksite, (K,Na) 2[(UO 2) 2(Si 5O 13)](H 2O) 3, occur in the vadose zone of the deposit and are overgrown by silica glaze. These glazes consist mainly of opal A, which contains small particles of uraninite, UO 2, and weeksite. Close to a fault between brecciated volcanic rocks and welded tuff, a greenish silica glaze coats the altered breccia. Yellow silica glazes from the center of the breccia pipe and from the high-grade pile coat uranyl-silicates, predominantly uranophane and weeksite. All silica glazes are strongly zoned with respect to U and Ca, and the distribution of these elements indicates curved features and spherical particles inside the coatings. The concentrations of U and Ca correlate in the different zones and both elements inversely correlate with the concentration of Si. Zones within the silica glazes contain U and Ca in a 1:1 ratio with maximum concentrations of 0.08 and 0.15 at.% for the greenish and yellow glazes, respectively, suggesting trapping of either Ca 1U 1-aqueous species or -particles in the colloidal silica. X-ray photoelectron spectroscopy (XPS), Fourier-transform infra-red spectroscopy (FTIR), and oxygen-isotope ratios measured by secondary-ion mass spectrometry (SIMS) indicate higher U 6+/U 4+ ratios, higher proportions of Si-OH groups and lower δ 18O values for the greenish silica glaze than for the yellow silica glaze. These differences in composition reflect increasing brecciation, porosity, and permeability from the center of the breccia pipe (yellow silica glaze) toward the fault (green silica glaze), where the seepage of meteoric water and Eh are higher.

  13. Seismic Investigation of El'gygytgyn Lake, Chukotka (NE Siberia)

    Science.gov (United States)

    Gebhardt, C.; Niessen, F.; Kopsch, C.; Wagner, B.

    2004-12-01

    Lake El'gygytgyn is a 3.6 Mio years old crater lake located in Central Chukotka, NE Russia, with a water depth of 170 m and a diameter of 12 km. Not having been glaciated ever since, it would reveal a paleoclimatic record unique in the Arctic realm. During the last years it has become a major focus of multi-disciplinary international research as a target for deep drilling in the near future. During expeditions in 2000 and 2003, reflection and refraction seismic combined with high resolution 3.5 kHz echosound profiling was carried out. Raytracing of the sonobuoy refraction data reveals a four-layer model of the lake that is interpreted as follows: (a) upper sedimentary unit, consisting of lacustrine muds with velocities of around 1500 m/s and a thickness of about 170 m, (b) lower sedimentary unit, consisting of lacustrine muds with velocities of around 1650 m/s and a thickness between 80 and 200 m, (c) fallback breccia with velocities of about 3000 m/s and a thickness between 50 and 300 m and (d) brecciated bedrock with velocities of > 3600 m/s. The brecciated bedrock forms a central uplift structure which is almost levelled by the overlying fallback breccia. The lower sedimentary unit drapes the smooth topography of the fallback breccia, whereas the upper sedimentary unit is almost flat. Small faults are associated with the central uplift structure and have been active until recently. Reflection seismic data indicate that the upper sedimentary unit is characterized by well stratified sediments, whereas the lower sedimentary unit is more massive. The upper sedimentary unit is locally intercalated with debris flows to a depth of at least 160 m subbottom. Debris flows are more common in the western part of the lake and along the slopes. The 3.5 kHz profiling allows a detailed mapping of the debris flow distribution. At the proposed drillsite near the centre of the lake, the sediments appear to be well stratified and largely unaffected by debris flows and promises a

  14. Chicxulub Impact, Yucatan Carbonate Platform, Cretaceous-Paleogene Boundary and Paleocene-Eocene Thermal Maximum

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L. L.

    2015-12-01

    Chicxulub formed 66 Ma ago by an asteroid impact on the Yucatan carbonate platform, southern Gulf of Mexico. Impact produced a 200 km diameter crater, platform fracturing, deformation and ejecta emplacement. Carbonate sedimentation restarted and crater was covered by up to 1 km of sediments. Drilling programs have sampled the Paleogene sediments, which record the changing sedimentation processes in the impact basin and platform. Here, results of a study of the Paleocene-Eocene sediments cored in the Santa Elena borehole are used to characterize the K/Pg and PETM. The borehole reached a depth of 504 m and was continuously cored, sampling the post-impact sediments and impact breccias, with contact at 332 m. For this study, we analyzed the section from ~230 to ~340 m, corresponding to the upper breccias and Paleocene-Eocene sediments. The lithological column, constructed from macroscopic and thin-section petrographic analyses, is composed of limestones and dolomitized limestones with several thin clay layers. Breccias are melt and basement clast rich, described as a suevitic unit. Section is further investigated using paleomagnetic, rock magnetic, X-ray fluorescence geochemical and stable isotope analyses. Magnetic polarities define a sequence of reverse to normal, which correlate to the geomagnetic polarity time scale from chrons 29r to 26r. The d13 C values in the first 20 m interval range from 1.2 to 3.5 %0 and d18 O values range from -1.4 to -4.8 %0. Isotope values show variation trends that correlate with the marine carbon and oxygen isotope patterns for the K-Pg boundary and early Paleocene. Positive carbon isotopes suggest relatively high productivity, with apparent recovery following the K-Pg extinction event. Geochemical data define characteristic trends, with Si decreasing gradually from high values in the suevites, low contents in Paleocene sediments with intervals of higher variability and then increased values likely marking the PETM. Variation trends are

  15. Mineralizing conditions and source fluid composition of base metal sulfides in the Lon District, southeastern Iceland

    Science.gov (United States)

    Kremer, C. H.; Thomas, D.; García del Real, P.; Zierenberg, R. A.; Bird, D. K.

    2014-12-01

    Hydrothermal base metal mineralization is rare in Iceland due to the scarcity of evolved magma bodies that discharge metal-rich aqueous fluids into bedrock. One exception is the Lon District of southeastern Iceland, where explosively emplaced rhyolitic breccias host base metal sulfide minerals. We performed petrographic, fluid inclusion, and stable isotope analyses on samples collected in Lon to constrain the conditions of sulfide mineral formation. Based on outcrop and hand sample observations, hot, early-stage hydrothermal fluids precipitated sulfide minerals, quartz, and epidote in rhyolitic breccia and basalt flows. Cooler late-stage fluids precipitated carbonates and quartz in rhyolitic breccia and basalt flows. The order of precipitation of the sulfides was: galena, sphalerite, then chalcopyrite. Homogenization temperatures of liquid-dominated multi-phase fluid inclusions in hydrothermal early-stage quartz coeval with chalcopyrite cluster around 303 °C and 330 °C, indicating precipitation of metallic sulfides in two main hydrothermal fluid pulses early in the period of hydrothermal activity in the Lon District. Freezing point depression analyses of fluid inclusions in quartz show that the sulfide minerals precipitated from a solution that was 4 wt. % NaCl. The 𝛿34S values of sulfides indicate that early-stage hydrothermal sulfur was derived from igneous rocks, either through leaching by non-magmatic hydrothermal fluids or by exsolution of magmatic waters. Early stage epidote 𝛿D values were on average -65.96 per mil, about 14 per mil higher than reported values in epidotes from elsewhere in southeastern Iceland. The 𝛿13C and 𝛿18O values of late-stage carbonates indicate that late stage hydrothermal fluids were meteoric in origin. Collectively, fluid inclusion and stable isotope analyses suggest that early-stage aqueous fluids derived from a mixture of magmatic waters exsolved from the proximal Geitafell intrusion and meteoric

  16. The internal geology and emplacement history of the Renard 2 kimberlite, Superior Province, Quebec, Canada

    Science.gov (United States)

    Fitzgerald, C. E.; Hetman, C. M.; Lepine, I.; Skelton, D. S.; McCandless, T. E.

    2009-11-01

    The Renard 2 kimberlite is located in the Otish Mountains region of Quebec, Canada and is one of the largest pipes in the Renard cluster. The cluster consists of nine kimberlite bodies and was discovered in 2001 by Ashton Mining of Canada Inc. and its joint venture partner SOQUEM Inc. Renard 2 was emplaced into Archean meta-greywacke derived migmatite, gneiss and granite of the Opinaca Subprovince of the eastern Superior Province at approximately 640.5 ± 2.8 Ma. An undetermined amount of erosion has occurred since emplacement with the present surface expression of the pipe estimated to be 0.75 ha. This kimberlite is interpreted as a steep-sided diatreme with minor irregularities in the external shape. The dominant infill is a massive volcaniclastic kimberlite (MVK) that is classified as tuffisitic kimberlite breccia (TKB) and is characterized by a high proportion of granitoid country rock xenoliths. A second dominant infill is a texturally complex, less diluted coherent kimberlite (CK) characterized locally by a transitional textures between CK and TKB. Surrounding the diatreme is a significant zone of variable width comprised of extensively brecciated country rock (+/-kimberlite) and referred to as marginal breccia. In addition to the two main rock types infilling the pipe, a number of hypabyssal kimberlite (HK) dykes and irregular shaped intrusions occur throughout the body, along the pipe contacts, within the marginal breccia and in the surrounding country rock. Geological features displayed by Renard 2 are similar to those described from Class 1 kimberlites of the Kimberley area of South Africa, the Gahcho Kué cluster of Canada and the Pimenta Bueno kimberlite field of Brazil. The economic evaluation of Renard 2 is in progress and to date has included extensive diamond and reverse circulation drilling as well as the collection of an underground bulk sample. Results from material sampled from Renard 2, including a 2449 tonne bulk sample, suggest Renard 2 has

  17. Origin and diagenetic evolution of gypsum and microbialitic carbonates in the Late Sag of the Namibe Basin (SW Angola)

    Science.gov (United States)

    Laurent, Gindre-Chanu; Edoardo, Perri; Ian, Sharp R.; Peacock, D. C. P.; Roger, Swart; Ragnar, Poulsen; Hercinda, Ferreira; Vladimir, Machado

    2016-08-01

    Ephemeral evaporitic conditions developed within the uppermost part of the transgressive Late Sag sequence in the Namibe Basin (SW Angola), leading to the formation of extensive centimetre- to metre-thick sulphate-bearing deposits and correlative microbialitic carbonates rich in pseudomorphs after evaporite crystals. The onshore pre-salt beds examined in this study are located up to 25 m underneath the major mid-Aptian evaporitic succession, which is typified at the outcrop by gypsiferous Bambata Formation and in the subsurface by the halite-dominated Loeme Formation. Carbonate-evaporite cycles mostly occur at the top of metre-thick regressive parasequences, which progressively onlap and overstep landward the former faulted (rift) topography, or fill major pre-salt palaeo-valleys. The sulphate beds are made up of alabastrine gypsum associated with embedded botryoidal nodules, dissolution-related gypsum breccia, and are cross-cut by thin satin-spar gypsum veins. Nodular and fine-grained fabrics are interpreted as being diagenetic gypsum deposits resulting from the dissolution and recrystallisation of former depositional subaqueous sulphates, whereas gypsum veins and breccia result from telogenetic processes. The carbonates display a broader diversity of facies, characterised by rapid lateral variations along strike. Thin dolomitic and calcitic bacterial-mediated filamentous microbialitic boundstones enclose a broad variety of evaporite pseudomorphs and can pass laterally over a few metres into sulphate beds. Dissolution-related depositional breccias are also common and indicate early dissolution of former evaporite layers embedded within the microbialites. Sulphate and carbonate units are interpreted as being concomitantly deposited along a tide-dominated coastal supra- to intertidal- sabkha and constitute high-frequency hypersaline precursor events, prior to the accumulation of the giant saline mid-Aptian Bambata and Loeme Formations. Petrographic and geochemical

  18. The graben caldera of Guanajuato, Mexico

    Science.gov (United States)

    Aguirre-Diaz, G. J.; Tristán-González, M.; Labarthe-Hernández, G.; Marti, J.

    2013-05-01

    Guanajuato has been an important gold and silver mineral district of Mexico since the 16th century until Present. Famous mines such as Rayas, La Valenciana and El Cubo, are part of this important mining development. Stratigraphy and structures are well known, and major faults and vein systems are precisely mapped. The series include a Mesozoic metamorphosed volcano-sedimentary sequence interpreted as a tectonically accreted terrane during Early Cretaceous subduction; a >1000 m thick red beds sequence, apparently Eocene and interpreted originally as molasses posterior to K/T Laramide orogeny, but more probably fanglomerates filling a graben formed during mid-Tertiary extension; an Eocene-Miocene volcanic sequence that accumulated in this tectonic basin and the surrounding area, including andesitic lavas, silicic ignimbrites and surge deposits, and rhyolitic domes. Pyroclastic rocks have not been studied with a volcanological approach, with the purpose of understanding the physical volcanic processes that formed them. Randall (1994) suggested a caldera source for some of them. Our purpose is to describe the volcanic processes involved in the mid-Tertiary units of Guanajuato. There are dacitic and andesitic lavas that were apparently contemporaneous with deposition of the Red Conglomerate of Guanajuato. The ignimbrites correspond to the Sierra Madre Occidental volcanic province. These units were originated as two main pyroclastic densety currents sequences that formed the Loseros-Bufa and the Calderones formations. The former is rhyolitic and the later andesitic-dacitic. Loseros is composed of a series of thin-bedded to laminated pyroclastic surge deposits in continuous and concordant contact with overlying Bufa massive ignimbrite. Bufa ignimbrite is partly welded, with columnar jointing, completely devitrified, and highly silicified by post-deposition hydrothermalism and/or vapor phase alteration. Co-ignimbrite lithic lag breccias are observed at several sites in

  19. Chronology for the Cueva Victoria fossil site (SE Spain): Evidence for Early Pleistocene Afro-Iberian dispersals.

    Science.gov (United States)

    Gibert, Luis; Scott, Gary R; Scholz, Denis; Budsky, Alexander; Ferràndez, Carles; Ribot, Francesc; Martin, Robert A; Lería, María

    2016-01-01

    Cueva Victoria has provided remains of more than 90 species of fossil vertebrates, including a hominin phalanx, and the only specimens of the African cercopithecid Theropithecus oswaldi in Europe. To constrain the age of the vertebrate remains we used paleomagnetism, vertebrate biostratigraphy and (230)Th/U dating. Normal polarity was identified in the non-fossiliferous lowest and highest stratigraphic units (red clay and capping flowstones) while reverse polarity was found in the intermediate stratigraphic unit (fossiliferous breccia). A lower polarity change occurred during the deposition of the decalcification clay, when the cave was closed and karstification was active. A second polarity change occurred during the capping flowstone formation, when the upper galleries were filled with breccia. The mammal association indicates a post-Jaramillo age, which allows us to correlate this upper reversal with the Brunhes-Matuyama boundary (0.78 Ma). Consequently, the lower reversal (N-R) is interpreted as the end of the Jaramillo magnetochron (0.99 Ma). These ages bracket the age of the fossiliferous breccia between 0.99 and 0.78 Ma, suggesting that the capping flowstone was formed during the wet Marine Isotopic Stage 19, which includes the Brunhes-Matuyama boundary. Fossil remains of Theropithecus have been only found in situ ∼1 m below the B/M boundary, which allows us to place the arrival of Theropithecus to Cueva Victoria at ∼0.9-0.85 Ma. The fauna of Cueva Victoria lived during a period of important climatic change, known as the Early-Middle Pleistocene Climatic Transition. The occurrence of the oldest European Acheulean tools at the contemporaneous nearby site of Cueva Negra suggest an African dispersal into SE Iberia through the Strait of Gibraltar during MIS 22, when sea-level was ∼100 m below its present position, allowing the passage into Europe of, at least, Theropithecus and Homo bearing Acheulean technology. PMID:26581114

  20. Uranium and Sm isotope studies of the supergiant Olympic Dam Cu-Au-U-Ag deposit, South Australia

    Science.gov (United States)

    Kirchenbaur, Maria; Maas, Roland; Ehrig, Kathy; Kamenetsky, Vadim S.; Strub, Erik; Ballhaus, Chris; Münker, Carsten

    2016-05-01

    The Olympic Dam Cu-U-Au-Ag deposit in the Archean-Proterozoic Gawler Craton (South Australia) is a type example of the iron oxide-copper-gold (IOCG) spectrum of deposits and one of the largest Cu-U-Au resources known. Mineralization is hosted in a lithologically and texturally diverse, hematite-rich breccia complex developed within a granite of the 1.59 Ga Gawler Silicic Province. Emerging evidence indicates that both the breccia complex and its metal content developed over ∼1000 Ma, responding to major tectonic events, e.g., at 1300-1100, 825 and 500 Ma. However, metal sources and exact mechanism/s of ore formation remain poorly known. New high-precision 238U/235U data for a set of 40 whole rock samples representing all major lithological facies of the breccia complex show a narrow range (δ238UCRM112a = -0.56‰ to +0.04‰). At the scale of sampling, there is no correlation of δ238U with lithology, degree of alteration or U mineralogy, although ores with U > 5 wt.% have subtly higher δ238U values (-0.20‰ to 0.00) than the majority of samples (5 wt.% U, U/Sm ≫ 500) Olympic Dam ores define a neutron capture line, with correlated depletions in 149Sm (up to ∼2ε units) and excesses in 150Sm (up to ∼ 4ε units), but fission fragment contributions to Sm are below detection. These observations provide evidence for small-scale neutron-capture effects, with calculated neutron fluences of 1015 to 1016 n cm-2, similar to those observed in several Proterozoic and Phanerozoic U deposits. The apparent lack of fission fragment contributions in Olympic Dam high-grade ores can be explained with an age of U deposition, or re-deposition that is substantially younger than the initial 1.59 Ga age of the oldest IOCG-style mineralization. The results presented here thus (i) suggest uranium sources in common (likely igneous) upper crustal lithologies, (ii) support geochronological evidence for gradual addition of U in several stages over 1000 Ma at elevated temperatures of

  1. Facies-controlled volcanic reservoirs of northern Songliao Basin, NE China

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Volcanic rocks of the late Mesozoic are very important reservoirs for the commercial natural gases including hydrocarbon, carbon dioxide and rare gases in the northern Songliao Basin. The reservoir volcanic rocks include rhyolite,andesite, trachyte, basalt and tuff. Facies of the volcanic rocks can be classified into 5 categories and 15 special types.Porosity and permeability of the volcanic reservoirs are facies-controlled. Commercial reservoirs were commonly found among the following volcanic subfacies: volcanic neck (Ⅰ1), underground-explosive breccia (Ⅰ3), pyroclastic-bearing lava flow (Ⅱ3), upper effusive (Ⅲ3) and inner extrusive ones (Ⅳ1). The best volcanic reservoirs are generally evolved in the interbedded explosive and effusive volcanics. Rhyolites show in general better reservoir features than other types of rocks do.

  2. Highly Sideophile Element Abundance Constraints on the Nature of the Late Accretionary Histories of Earth, Moon and Mars

    Science.gov (United States)

    Walker, R. J.; Puchtel, I. S.; Brandon, A. D.; Horan, M. F.; James, O. B.

    2007-01-01

    The highly siderophile elements (HSE) include Re, Os, Ir, Ru, Pt and Pd. These elements are initially nearly-quantitatively stripped from planetary silicate mantles during core segregation. They then may be re-enriched in mantles via continued accretion sans continued core segregation. This suite of elements and its included long-lived radiogenic isotopes systems (Re-187 (right arrow) Os-187; Pt-190 (right arrow) Os-186) can potentially be used to fingerprint the characteristics of late accreted materials. The fingerprints may ultimately be useful to constrain the prior nebular history of the dominant late accreted materials, and to compare the proportion and genesis of late accretionary materials added to the inner planets. The past ten years have seen considerable accumulation of isotopic and compositional data for HSE present in the Earth's mantle, lunar mantle and impact melt breccias, and Martian meteorites. Here we review some of these data and consider the broader implications of the compiled data.

  3. EEG review comments on the geotechnical reports provided by DOE to EEG under the stipulated agreement through March 1, 1983

    International Nuclear Information System (INIS)

    The purpose of the Environmental Evaluation Group (EEG) is to conduct an independent technical evaluation of the potential radiation exposure to people from the proposed federal radioactive Waste Isolation Pilot Plant (WIPP) near Carlsbad, in order to protect the public health and safety and ensure that there is minimal environmental degradation. Analyses are conducted of available data concerning the proposed site, the design of the repository, its planned operation, and its long-term stability. These analyses include assessments of reports issued by the US Department of Energy (DOE) and its contractors, other federal agencies and organizations, as they relate to the potential health, safety and environmental impacts from WIPP. This publication is a compilation of EEG's written comments on each of the following reports: Deep Dissolution; Breccia Pipes; DMG Hydrology; Natural Resources; Plans for Site and Preliminary Design Validation; Plans for Simulated Waste; Brine Reservoir Report; Disturbed Zone Exploration; and Fracture Flow in the Rustler Aquifers

  4. Uranium and thorium deposits of Northern Ontario

    International Nuclear Information System (INIS)

    This, the second edition of the uranium-thorium deposit inventory, describes briefly the deposits of uranium and/or thorium in northern Ontario, which for the purposes of this circular is defined as that part of Ontario lying north and west of the Grenville Front. The most significant of the deposits described are fossil placers lying at or near the base of the Middle Precambrian Huronian Supergroup. These include the producing and past-producing mines of the Elliot Lake - Agnew Lake area. Also included are the pitchblende veins spatially associated with Late Precambrian (Keweenawan) diabase dikes of the Theano Point - Montreal River area. Miscellaneous Early Precambrian pegmatite, pitchblende-coffinite-sulphide occurrences near the Middle-Early Precambrian unconformity fringing the Lake Superior basin, and disseminations in diabase, granitic rocks, alkalic complexes and breccias scattered throughout northern Ontario make up the rest of the occurrences

  5. National uranium resource evaluation, Marble Canyon Quadrangle, Arizona and Utah

    International Nuclear Information System (INIS)

    The Marble Canyon Quadrangle (20), northeast Arizona, was evaluated to a depth of 1500 m for uranium favorability using National Uranium Resource Evaluation criteria. Known mines and prospects were examined; field reconnaissance was done in selected areas of the quadrangle; and a ground-water geochemical survey was made in the southeast third of the quadrangle. The Shinarump and Petrified Forest Members of the Triassic Chinle Formation, which is exposed in the western and northeastern parts of the quadrangle and is present beneath the surface of much of the quadrangle, were found favorable for channel-sandstone uranium deposits. A portion of the Cretaceous Toreva Formation in the southeast part of the quadrangle was found favorable for peneconcordant-sandstone uranium deposits. The western part of the quadrangle was found favorable for uranium concentrations in breccia pipes

  6. K-Ar Geochronology and isotopic composition of the late oligocene- early miocene Ancud volcanic complex, Chiloe

    International Nuclear Information System (INIS)

    The Ancud Volcanic Complex (Gally and Sanchez , 1960) forms a portion of the Mid-Tertiary Coastal Magmatic Belt which outcrops in the area of northern Chiloe island. Main exposures occur at Ancud, Punta Polocue, Punihuil, Pumillahue, Tetas de Teguaco and Bahia Cocotue. The Ancud Volcanic Complex consists of basaltic to basaltic andesites lava flows and volcanic necks and rhyolitic pyroclastic flows and vitric domes. Previous studies indicate a Late Oligocene-Early Miocene age (Garcia et al., 1988; Stern and Vergara, 1992; Munoz et al., 2000). The Ancud Volcanic Complex covers and intrudes Palaeozoic-Triassic metamorphic rocks and is partially covered by an early to middle Miocene marine sedimentary sequence known as Lacui Formation (Valenzuela, 1982) and by Pleistocene glacial deposits (Heusser, 1990). At Punihuil locality, lava flows are interbedded with the lower part of the marine sedimentary sequence, which includes significant amounts of redeposited pyroclastic components. Locally, the presence of hyaloclastic breccias suggests interaction of magma with marine water (au)

  7. Thermoluminescence of lunar samples

    Science.gov (United States)

    Dalrymple, G.B.; Doell, Richard R.

    1970-01-01

    Appreciable natural thermoluminescence with glow curve peaks at about 350 degrees centigrade for lunar fines and breccias and above 400 degrees centigrade for crystalline rocks has been recognized in lunar samples. Plagioclase has been identified as the principal carrier of thermoluminescence, and the difference in peak temperatures indicates compositional or structural differences between the feldspars of the different rock types. The present thermoluminescence in the lunar samples is probably the result of a dynamic equilibrium between acquisition from radiation and loss in the lunar thermal environment. A progressive change in the glow curves of core samples with depth below the surface suggests the use of thermoluminescence disequilibrium to detect surfaces buried by recent surface activity, and it also indicates that the lunar diurnal temperature variation penetrates to at least 10.5 centimeters.

  8. The origin and history of alteration and carbonatization of the Yucca Mountain ignimbrites. Volume I

    Energy Technology Data Exchange (ETDEWEB)

    Szymanski, J.S.

    1992-04-01

    This document contains Volume I of the report entitled The Origin and History of Alteration and Carbonatization of the Yucca Mountain Ignimbrites by Jerry S. Szymanski and a related correspondence with comments by Donald E. Livingston. In the Great Basin, the flow of terrestrial heat through the crust is affected in part by the flow of fluids. At Yucca Mountain, the role of fluids in crustal heat transport is manifested at the surface by youthful calcretes, sinters, bedrock veins, hydrothermal eruption breccias and hydrothermal alteration. This report discusses evidence for recent metasomatism high in the stratigraphic section at Yucca Mountain. Over the last several hundred years, episodes of calcite emplacement contemporaneous with local mafic volcanism have occurred at intervals that are not long in comparison with the isolation time required for a High-Level Radioactive Waste repository.

  9. Sima de los Huesos (Sierra de Atapuerca, Spain). The site.

    Science.gov (United States)

    Arsuaga, J L; Martínez, I; Gracia, A; Carretero, J M; Lorenzo, C; García, N

    1997-01-01

    In this article a topographical description of the Cueva Mayor Cueva de Silo cave system is provided, including a more detailed topography of the Sala de los Ciclopes Sala de las Oseras-Sima de los Huesos sector. The history of the excavations and discoveries of human and carnivore fossils in Sima de los Huesos and adjacent passages is briefly reported, as well as the increase, throughout the succeeding field seasons, of the human collection and changes in the relative representation of the different skeletal elements and major biases. The carnivore assemblage structure is also considered. Examining the characteristics of the bone breccia, and the current and ancient karst topography, different alternative accesses are discussed for the accumulation of carnivores and humans in the Sima de los Huesos. Taking into account all the available information, an anthropic origin for the accumulation of human fossils seems to us to be the most likely explanation. PMID:9300338

  10. The Sima de los Huesos hominids date to beyond U/Th equilibrium (>350 kyr) and perhaps to 400-500 kyr: New radiometric dates

    Science.gov (United States)

    Bischoff, J.L.; Shamp, D.D.; Aramburu, Arantza; Arsuaga, J.L.; Carbonell, E.; Bermudez de Castro, Jose Maria

    2003-01-01

    The Sima de los Huesos site of the Atapuerca complex near Burgos, Spain contains the skeletal remains of at least 28 individuals in a mud breccia underlying an accumulation of the Middle Pleistocene cave bear (U. deningeri). Earlier dating estimates of 200 to 320 kyr were based on U-series and ESR methods applied to bones, made inaccurate by unquantifiable uranium cycling. We report here on a new discovery within the Sima de los Huesos of human bones stratigraphically underlying an in situ speleothem. U-series analyses of the speleothem shows the lower part to be at isotopic U/Th equilibrium, translating to a firm lower limit of 350 kyr for the SH hominids. Finite dates on the upper part suggest a speleothem growth rate of c. 1 cm/32 kyr. This rate, along with paleontological constraints, place the likely age of the hominids in the interval of 400 to 600 kyr. ?? 2002 Elsevier Science Ltd. All rights reserved.

  11. Stratigraphy, structure, and some petrographic features of Tertiary volcanic rocks in the USW G-2 drill hole, Yucca Mountain, Nye County, Nevada

    Science.gov (United States)

    Maldonado, Florian; Koether, S.L.

    1983-01-01

    A continuously cored drill hole designated as USW G-2, located at Yucca Mountain in southwestern Nevada, penetrated 1830.6 m of Tertiary volcanic strata composed of abundant silicic ash-flow tuffs, minor lava and flow breccias, and subordinate volcaniclastic rocks. The volcanic strata penetrated are comprised of the following in descending order: Paintbrush Tuff (Tiva Canyon Member, Yucca Mountain Member, bedded tuff, Pah Canyon Member, and Topopah Spring Member), tuffaceous beds of Calico Hills, Crater Flat Tuff (Prow Pass Member, Bullfrog Member, and Tram unit), lava and flow breccia (rhyodacitic), tuff of Lithic Ridge, bedded and ash-flow tuff, lava and flow breccia (rhyolitic, quartz latitic, and dacitic), bedded tuff, conglomerate and ash-flow tuff, and older tuffs of USW G-2. Comparison of unit thicknesses at USW G-2 to unit thicknesses at previously drilled holes at Yucca Mountain indicate the following: (1) thickening of the Paintbrush Tuff members and tuffaceous beds of Calico Hills toward the northern part of Yucca Mountain; (2) thickening of the Prow Pass Member but thinning of the Bullfrog Member and Tram unit; (3) thinning of the tuff of Lithic Ridge; (4) presence of approximately 280 m of lava and flow breccia not previously penetrated by any drill hole; and (5) presence of an ash-flow tuff unit at the bottom of the drill hole not previously intersected, apparently the oldest unit penetrated at Yucca Mountain to date. Petrographic features of some of the units include: (1) decrease in quartz and K-feldspar and increases in biotite and plagioclase with depth in the tuffaceous beds of Calico Hills; (2) an increase in quartz phenocrysts from the top to the bottom members of the Crater Flat Tuff; (3) a low quartz content in the tuff of Lithic Ridge, suggesting tapping of the magma chamber at quartz-poor levels; (4) a change in zeolitic alteration from heulandite to clinoptilolite to mordenite with increasing depth; (5) lavas characterized by a rhyolitic

  12. Electron microscopic observations of hydrogen implantation in ilmenites

    Science.gov (United States)

    Blanford, G. E.

    1983-01-01

    Hydrogen ion beams were found to form submicrometer, bumpy textures on the surface of ilmenite grains. From this effect, it is believed that similar bumpy textures seen on lunar ilmenite, pyroxene, and olivine grains are likely to be caused by solar wind irradiation. As a consequence, the concentration of bumpy textured grains may be a useful index of surface maturity for lunar soils. An attempt was made to search for grains with these bumpy textures in interplanetary dust and lunar and meteoritic regolith breccias in order to obtain information about the duration of their exposure to the solar wind. Solar wind irradiation was simulated on natural, terrestrial ilmenite. Hydrogen ion beams were directed at small grains and polished sections which were then examined by electron microscopy.

  13. The Montesbelos mass-flow (southern Amazonian craton, Brazil): a Paleoproterozoic volcanic debris avalanche deposit?

    Science.gov (United States)

    Roverato, M.

    2016-07-01

    The present contribution documents the extremely well-preserved Paleoproterozoic architecture of the Montesbelos breccia (named here for the first time), which is interpreted as a rare example of a subaerial paleoproterozoic (>1.85 Ga) granular-dominated mass-flow deposit, few of which are recorded in the literature. Montesbelos deposit is part of the andesitic Sobreiro Formation located in the São Felix do Xingu region, southern Amazonian craton, northern Brazil. The large volume, high variability of textural features, presence of broken clasts, angular low sphericity fragments, mono- to heterolithic character, and the size of the outcrops point to a volcanic debris avalanche flow. Fluviatile sandy material and debris flows are associated with the deposit as a result of post-depositional reworking processes.

  14. SARSTEINIA BABAI N. GEN., N. SP., A NEW PROBLEMATIC SPONGE (INOZOA? FROM THE LATE JURASSIC OF THE NORTHERN CALCAREOUS ALPS, AUSTRIA

    Directory of Open Access Journals (Sweden)

    FELIX SCHLAGINTWEIT

    2006-07-01

    Full Text Available The new problematic sponge Sarsteinia babai n. gen., n. sp. is described from the Kimmeridgian to Tithonian Plassen and Lärchberg Formations of the Northern Calcareous Alps of Austria. The type-locality is the Sarsteinalm north of Mount Hoher Sarstein in the Austrian Salzkammergut, other findings come from Mount Sandling, Mount Jainzen, Mount Trisselwand and the Litzlkogel-Gerhardstein-complex west of Lofer. Most findings can be attributed to a fore-reef to upper slope facies or slope-of-toe breccias, small fragments can occasionally also be found in the back-reef facies. The suprageneric systematic position of the new sponge is unknown so far since it shows morphological characteristics known from Inozoa but also from "stromatoporoids".

  15. The 57Fe hyperfine interactions in the iron bearing phases in different fragments of Chelyabinsk LL5 meteorite: a comparative study using Mössbauer spectroscopy with a high velocity resolution

    International Nuclear Information System (INIS)

    A comparative study of the 57Fe hyperfine interactions in iron bearing phases of Chelyabinsk LL5 ordinary chondrite fragments with different lithology was carried out using Mössbauer spectroscopy with a high velocity resolution. The obtained values of hyperfine parameters for the same iron bearing phases in different fragments demonstrated small variations. These differences were related to small variations in the Fe local microenvironments in both M1 and M2 sites in olivine and pyroxene, to deviation from stoichiometry in troilite with increase in Fe vacancies and to differences in Ni concentrations in α-Fe(Ni, Co) and γ-Fe(Ni, Co) phases in the metal grains. The obtained differences may indicate a breccia structure of Chelyabinsk LL5 ordinary chondrite

  16. A review of recent studies in the Pine Creek geosyncline with special reference to uranium

    International Nuclear Information System (INIS)

    The Lower Proterozoic metasediments of the Pine Creek Geosyncline form a chronostratigraphic sequence of mainly greenschistand amphibolite-grade shallow-marine to supratidal pelites, psammites, carbonate rocks, and volcaniclastics which in places rests unconformably on Archaean basement. Granite and later dolerite intrude the sequence, and are associated with the major orogenic 1800-m.y. event which regionally metamorphosed the sediments. Most mineralisation is stratabound, and can be related at least partly to volcanic activity. Uranium mineralisation is mainly confined to particular carbonate-rich horizons near basement. Specialist studies indicate that uranium was leached from its souce rock, and probably carried as carbonate complexes in highly saline fluids at between 100 and 350 deg. C. Precipitation took place by redox reactions in breccia zones in carbonate rocks; these zones were formed by carbonate solution or diapiric movement of evaporites which preceded the carbonate

  17. Geological history of Yucca Mountain (Nevada) and the problem of a high-level nuclear waste repository

    International Nuclear Information System (INIS)

    Three types of deposits are widely distributed throughout the Yucca Mountain unsaturated zone: mosaic breccias, quartz-calcite veinlets, and micritic opal-calcite veins and associated slope deposits were found to be of hydrothermal origin. The inference is based on petrographic, accessory mineral, fluid inclusion, and stable isotopic data. The overall conclusion is that recurrent low-temperature hydrothermal (epithermal) activity occurred at Yucca Mountain in the geologically recent past (from ca. 8-10 Ma to as recently as 25 ka). New data require the currently- accepted concept of the hydrogeological system at Yucca Mountain to be reconsidered. The subject relates to the suitability of Yucca Mountain as a high-level nuclear waste site. 21 refs

  18. WIRGO in TIC's? [What (on Earth) is Really Going On in Terrestrial Impact Craters?

    Science.gov (United States)

    Dence, Michael R.

    2003-02-01

    Canada is well endowed with impact craters formed in crystalline rocks with relatively homogeneous physical properties. They exhibit all the main morphological-structural variations with crater size seen in craters on other rocky planets, from small simple bowl to large peak and ring forms. Lacking stratigraphy, analysis is based on the imprint of shock melting and metamorphism, the position of the GPL (limit of initial Grady-Kipp fracturing due to shock wave reverberations) relative to shock level, the geometry of late stage shears and breccias and the volume of shocked material beyond the GPL. Simple craters, exemplified by Brent (D = 3.7 km) allow direct comparison with models and experimental data. Results of interest include: 1. The central pool of impact melt and underlying breccia at the base of the crater fill is interpreted as the remnant of the transient crater lining; 2. The overlying main mass of breccias filling the final apparent crater results from latestage slumping of large slabs bounded by a primary shear surface that conforms to a sphere segment of radius, rs approx. = 2dtc, where dtc is the transient crater depth; 3. The foot of the primary shear intersects above the GPL at the centre of the melt pool and the rapid emplacement of slumped slabs produces further brecciation while suppressing any tendency for the centre to rise. In the autochthonous breccias below the melt and in the underlying para-allochthone below the GPL, shock metamorphism weakens with depth. The apparent attenuation of the shock pulse can be compared with experimentally derived rates of attenuation to give a measure of displacements down axis and estimates of the size of a nominal bolide of given velocity, the volume of impact melt and the energy released on impact. In larger complex craters (e.g. Charlevoix, D = 52 km) apparent shock attenuation is low near the centre but is higher towards the margin. The inflection point marks the change from uplift of deep material in the

  19. Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material

    Science.gov (United States)

    Friedman, I.; O'Neil, J.R.; Adami, L.H.; Gleason, J.D.; Hardcastle, K.

    1970-01-01

    The water content of the breccia is 150 to 455 ppm, with a ??D from -580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a ??D of -830 to -970 per mil. The CO2 is 290 to 418 ppm with S 13C = + 2.3 to + 5.1 per mil and ??18O = 14.2 to 19.1 per mil. Non-CO2 carbon is 22 to 100 ppm, ??18C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H2O (D = 80 ppm) and 188 ppm total carbon (??13C = -17.6 per mil). The 18O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100?? to 1300??C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.

  20. Grainstones and cementstone mounds: The Trogkofel summit section (Lower Permian, Carnic Alps, Austria).

    Science.gov (United States)

    Schaffhauser, M.; Sanders, D.; Krainer, K.

    2009-04-01

    are overgrown by abundant, thick fringes and botryoids of fibrous cement that is interpreted as calcitized aragonite cement. In addition, brachiopods, crustose red algae, and a few solitary and colonial rugose corals are typical. By volume, the former aragonite cement comprises the majority of the mounds. Intrinsic pores within the cementstone fabrics typically are filled by micropeloidal grainstone and/or by lime mudstone. The Trogkofel Limestone is locally dolomitized. Replacement dolomites show a wide range of crystal shapes and textures, but overall comprise (a) finely-crystalline, limpid dolostone of xenotopic or hypidiotopic fabrics that broadly mimick the texture of replaced sediment and cements, (b) coarse-crystalline fabrics of hypidiotopic to idiotopic, limpid or optically zoned dolomite, and (c) replacement saddle dolomite. The Trogkofel Limestone is riddled by karstic dykes and caverns that are mainly filled by, both or either of, geopetally-laminated red lime mudstone, terrigenous red sandstones, or thick fringes of fibrous cement. In the karstic cavity fills, packages of convolute geopetal lamination and brecciated internal sediments (internal seismites) overlain by infills with non-convolute lamination, fracture of fibrous cements, and dykes filled by multi-phase fracture breccias record tectonism during or after deposition of the Trogkofel Limestone. The Trogkofel Limestone is capped by a truncation surface which, in turn, is overlain by an interval of extremely poorly sorted, thick-bedded breccias with a former matrix of lime mudstone ("Trogkofel Breccia"). Both the components and the matrix of the Trogkofel Breccia are dolomitized. We interpret the facies and facies architecture of the eastern cliff section of Trogkofel as succession from the seaward side of a "grainstone-dominated" platform margin with cementstone mounds. The lack of clear-cut vertical trends in prevalent facies suggests that the platform margin developed mainly by aggradation. The

  1. Volcanic petrology and geologic history of Northeast Bank, Southern California Borderland.

    Science.gov (United States)

    Hawkins, J. W.; Macdougall, D.; Allison, E. C.

    1971-01-01

    Basaltic rocks, hyaloclastites, and fossil fragments incorporated in volcanic material, dredged from the flanks of Northeast Bank on the Southern California Borderland, show trace element abundances typical of eastern Pacific basin alkali basalts but enriched (880 ppm) Ba. The fossil fragments, incorporated in breccia, hyaloclastite, and agglomerate, include a fauna which lived in less than 50 m of water, as well as forms from the intertidal zone. Bathymetry of the bank and the depth range of the dredged zone indicate that there has been at least 300 or as much as 500 m subsidence since the volcanism which incorporated the fauna in volcanic material. Isostatic adjustments due to crustal load of the bank can account for this subsidence.

  2. The origin and history of alteration and carbonatization of the Yucca Mountain ignimbrites. Volume I

    International Nuclear Information System (INIS)

    This document contains Volume I of the report entitled The Origin and History of Alteration and Carbonatization of the Yucca Mountain Ignimbrites by Jerry S. Szymanski and a related correspondence with comments by Donald E. Livingston. In the Great Basin, the flow of terrestrial heat through the crust is affected in part by the flow of fluids. At Yucca Mountain, the role of fluids in crustal heat transport is manifested at the surface by youthful calcretes, sinters, bedrock veins, hydrothermal eruption breccias and hydrothermal alteration. This report discusses evidence for recent metasomatism high in the stratigraphic section at Yucca Mountain. Over the last several hundred years, episodes of calcite emplacement contemporaneous with local mafic volcanism have occurred at intervals that are not long in comparison with the isolation time required for a High-Level Radioactive Waste repository

  3. Le domaine Tariquide (arc de Gibraltar, Espagne et Maroc) : succession et hiatus de la sédimentation du Jurassique supérieur au Paléocène

    Science.gov (United States)

    Durand-Delga, Michel; Esteras, Manuel; Gardin, Silvia; Paquet, Hélène

    2005-07-01

    The originality of the Malm-Cretaceous series of the Tariquides (Gibraltar arc), as compared to those of the Rifian-Betic 'Dorsale' (Alboran domain), and especially with the Penibetic (Iberia) domain, is emphasized. In the Los Pastores Group, near Algeciras, Upper Tithonian nodular limestones directly lie on the Dogger and are followed by Aptychus-bearing limestones (Late Berriasian to Barremian). In the Musa Group, Rif, radiolarites are followed by siliceous limestones (Kimmeridgian-Tithonian), then by karst and massflow breccias connected to a Berriasian tectonics, by Aptychus-bearing marly limestones, then by karst filled by Turonian limestones, and finally by Maastrichtian-Palaeocene polychrome pelites, whose micropalaeontological and mineral compositions (clay minerals, Fe sbnd Mn nodules) refer to a deep-sea, probably infra-CCD, sedimentation. To cite this article: M. Durand-Delga et al., C. R. Geoscience 337 (2005).

  4. Activités volcaniques sous-marines à la limite Jurassique-Crétacé dans le Rif externe (Maroc). Âge et relation avec la sédimentation et la paléogéographie du sillon rifain externe

    Science.gov (United States)

    Benzaggagh, Mohamed

    2011-04-01

    Following the recent stratigraphic works carried out on the Jurassic-Cretaceous boundary in the external Rif chain (Mesorif area and Bou Haddoud nappe), numerous submarine volcanism traces have been discovered in Upper Oxfordian to Upper Berriasian deposits. These traces display various aspects: volcaniclastic complexes incorporated within Upper Berriasian marls; volcanic lavas and basalt clasts included in the breccias with clay matrix of Upper Oxfordian to Lower Berriasian age, or in brecciated Lower Tothonian calcareous beds of the Early Tithonian. These submarine volcanic activities took place in a carbonate platform environment during the Kimmeridgian to Early Tithonian interval or in a pelagic basin from Late Tithonian onwards. They caused an intense brecciation of Upper Jurassic carbonate formations and a general dismantling of marly calcareous alternations of Upper Tithonian-Lower Berriasian. Therefore, the Upper Tithonian-Lower Berriasian deposits are marked by frequent stratigraphic gaps in many outcrops of Mesorif, Prerif areas and in the Bou Haddoud nappe.

  5. Geochemical data synthesis and analysis

    Science.gov (United States)

    Philpotts, J. A.

    1979-01-01

    Data obtained at the Goddard Flight Center were collected for the purpose of completing analyses started at Goddard in order to maximize the scientific yield of the geochemistry program which was terminated in 1977. The major analytical task undertaken was to complete Gd analyses on a large number of samples already analyzed by mass spectrometry for other rare earth element abundances at Goddard. Gd values are important for pinning down the central part of the geochemically significant rare earth abundance pattern and are especially useful in the high precision definition of the utilitarian Eu anomaly. Isotope-dilution Gd abundances were obtained for 39 samples. The data are for 27 partition-coefficient samples, six Apollo 15 and 16 breccia samples, four terrestrial impactities, and associated rock standards.

  6. Mineralogy at the magma-hydrothermal system interface in andesite volcanoes, New Zealand

    Science.gov (United States)

    Wood, C. Peter

    1994-01-01

    Ejecta from phreatomagmatic eruptions of Ruapehu and White Island andesite volcanoes in New Zealand provide insight into the mineralogical reactions that occur when magma invades a vent-hosted hydrothermal system. At the surface and in ejected blocks from shallow depths, hydrothermal alteration mineralogies are dominated by silica polymorphs, anhydrite, natroalunite, and pyrite. Blocks from greater depths are composed mainly of cristobalite, anhydrite, halite, and magnetite. Where altered material was heated to magmatic temperatures, thermal decomposition reactions produced mullite, wollastonite, and indialite. Some ejected breccias contain osumilite, cordierite, sanidine, and hypersthene, indicative of reactions occurring near the osumilite-cordierite phase boundary at >800 °C and water pressure hydrothermal deposits. High- temperature parageneses of these types have not been reported before in shallow, acidic volcano-hydrothermal systems. However, they may be typical of the magma- hydrothermal contact zone at many andesite volcanoes.

  7. Depositional architecture of a mixed travertine-terrigenous system in a fault-controlled continental extensional basin (Messinian, Southern Tuscany, Central Italy)

    Science.gov (United States)

    Croci, Andrea; Della Porta, Giovanna; Capezzuoli, Enrico

    2016-03-01

    The extensional Neogene Albegna Basin (Southern Tuscany, Italy) includes several thermogene travertine units dating from the Miocene to Holocene time. During the late Miocene (Messinian), a continental fault-controlled basin (of nearly 500-km2 width) was filled by precipitated travertine and detrital terrigenous strata, characterized by a wedge-shaped geometry that thinned northward, with a maximum thickness of nearly 70 m. This mixed travertine-terrigenous succession was investigated in terms of lithofacies types, depositional environment and architecture and the variety of precipitated travertine fabrics. Deposited as beds with thickness ranging from centimetres to a few decimetres, carbonates include nine travertine facies types: F1) clotted peloidal micrite and microsparite boundstone, F2) raft rudstone/floatstone, F3) sub-rounded radial coated grain grainstone, F4) coated gas bubble boundstone, F5) crystalline dendrite cementstone, F6) laminated boundstone, F7) coated reed boundstone and rudstone, F8) peloidal skeletal grainstone and F9) calci-mudstone and microsparstone. Beds of terrigenous deposits with thickness varying from a decimetre to > 10 m include five lithofacies: F10) breccia, F11) conglomerate, F12) massive sandstone, F13) laminated sandstone and F14) claystone. The succession recorded the following three phases of evolution of the depositional setting: 1) At the base, a northward-thinning thermogene travertine terraced slope (Phase I, travertine slope lithofacies association, F1-F6) developed close to the extensional fault system, placed southward with respect to the travertine deposition. 2) In Phase II, the accumulation of travertines was interrupted by the deposition of colluvial fan deposits with a thickness of several metres (colluvial fan lithofacies association, F10 and F12), which consisted of massive breccias, adjacent to the alluvial plain lithofacies association (F11-F14) including massive claystone and sandstone and channelized

  8. Lunar Science Conference, 4th, Houston, Tex., March 5-8, 1973, Proceedings. Volume 1 - Mineralogy and petrology. Volume 2 - Chemical and isotope analyses. Organic chemistry. Volume 3 - Physical properties

    Science.gov (United States)

    Gose, W. A.

    1973-01-01

    The mineralogy, petrology, chemistry, isotopic composition, and physical properties of lunar materials are described in papers detailing methods, results, and implications of research on samples returned from eight lunar landing sites: Apollo 11, 12, 14, 15, 16, 17, and Luna 16 and 20. The results of experiments conducted or set up on the lunar surface by the astronauts are also described along with observations taken from Command Modules and subsatellites. Major topics include general geology, soil and breccia studies, petrologic studies, mineralogic analyses, elemental compositions, radiometric age determinations, rare gas chemistry, radionuclides, organogenic compounds, particle track records, thermal properties, seismic studies, resonance studies, orbital mapping, lunar atmosphere, magnetic studies, electrical studies, optical properties, and microcratering. Individual items are announced in this issue.

  9. Redbeds from the Middle Muschelkalk (Middle Triassic) of the SW Germanic Basin: arid environments from Pangea's interior

    Science.gov (United States)

    Vecsei, A.; Mandau, T.

    2002-01-01

    The facies of a redbed succession from the lower Middle Muschelkalk of the SW Germanic Basin allows reconstruction of the depositional environment and inference with regard to the climate in a little studied part of Pangea's interior. The redbeds are dominated by fine-grained terrigenous deposits, with both intercalated thin sandstone and carbonate beds. The clastics were derived from the nearby hinterland, and their facies suggest episodic deposition on a playa mud flat or flood plain. The occurrence in the lower part of the succession of sand-patch breccias, ooids, and dolomicrite beds suggests an origin in saline pans and playa lakes. These diverse facies, and phreatic dolomites, reflect an arid climate during deposition.

  10. Volatility in the lunar crust: Trace element analyses of lunar minerals by PIXE proton microprobe

    Science.gov (United States)

    Norman, M. D.; Griffin, W. L.; Ryan, C. G.

    1993-01-01

    In situ determination of mineral compositions using microbeam techniques can characterize magma compositions through mineral-melt partitioning, and be used to investigate fine-grained or rare phases which cannot be extracted for analysis. Abundances of Fe, Mn, Sr, Ga, Zr, Y, Nb, Zn, Cu, Ni, Se, and Sb were determined for various mineral phases in a small number of lunar highlands rocks using the PIXE proton microprobe. Sr/Ga ratios of plagioclase and Mn/Zn ratios of mafic silicates show that the ferroan anorthosites and Mg-suite cumulates are depleted in volatile lithophile elements to about the same degree compared with chondrites and the Earth. This links the entire lunar crust to common processes or source compositions. In contrast, secondary sulfides in Descartes breccia clasts are enriched in chalcophile elements such as Cu, Zn, Ni, Se, and Sb, and represent a potential resource in the lunar highlands.

  11. Paleomagnetism of the Mississippi Valley-type Zn-Pb deposits of the Silesian-Cracow area, Poland

    Science.gov (United States)

    Symons, David T. A.; Sangster, D.F.; Leach, D.L.

    1996-01-01

    Paleomagnetic analysis of zinc-lead ore and host rocks from 35 sites in three mines and several quarries was completed using alternating field and thermal step demagnetization and saturation isothermal remanent magnetization methods. Paleomagnetic conglomerate, breccia and fold tests were used to test for remanence stability. Most limestone and dolostone sites of the Middle Triassic Muschelkalk Formation carry a dual-polarity primary or diagenetic Middle to Upper Triassic remanence. Late dolomite and Mississippi Valley-type (MVT) mineralization from 14 sites carry a dual-polarity Tertiary magnetization that is shown to be post-brecciation and syndeformational by the paleomagnetic tests. This age supports gravity-driven fluid flow models for ore genesis that are associated with the Alpine orogeny.

  12. The Archaean gold-telluride-sulphide and gold-telluride mineralisation of a multiple stage hydrothermal vein deposit at the Commoner Mine, Zimbabwe

    International Nuclear Information System (INIS)

    The Commoner Mine is situated on the western edge of the Midlands greenstone belt, 50 km west-southwest of Kadoma, Zimbabwe. Current geological interest in this deposit was initiated by the presence of coarse grained telluride minerals in ore exposed on 21 level in 1978. The deposit is a hydrothermal quartz-calcite vein. It was found that coarse grained gold-silver tellurides fill fractures which transect the telluride breccia. Comparison of the physical and mineralogical characteristics of the Commoner orebody with those of the Tertiary gold-telluride deposits of the Circum Pacific Belt and the Archaean deposits of Canada and Australia indicates that this mineralisation was probably deposited in a near-surface environment. It was found that the gold-telluride ores of the Commoner Mine display features characteristic of both plutonic-hydrothermal and volcanic-hydrothermal styles of telluride mineralisation

  13. The occurrence of U-Cu-Au mineralisation in Khokhri-Bairath area, district Jaipur, Rajasthan, India

    International Nuclear Information System (INIS)

    Several old workings for copper have been found in the vicinity of Khokhri Pahadi of the Bairath Plateau of Jaipur district, Rajasthan, which comprises Bairath granite and Meso-Proterozoic metamorphosed volcano-sedimentary rocks of Delhi Supergroup. These copper workings lie within shear zones, represented by ferruginous siliceous breccia. Presence of anomalous gold (39-641 ppb), uranium (0.021 to 0.134%U38), copper (452-11212 ppm) and cobalt (75 to 512 ppm) has been recorded in 5 channel samples taken from the Khokhri shear zone (440 X 2-12m). The shear zones trending NW-SE to E-W are considered to have developed during early phase of deformation of Bairath granite and metasediments. The geological characteristics of the mineralized zones are characteristic of the shear controlled type deposits. (author)

  14. Central ring structure identified in one of the world's best-preserved impact craters

    Science.gov (United States)

    Gebhardt, A. C.; Niessen, F.; Kopsch, C.

    2006-03-01

    Seismic refraction and reflection data were acquired in 2000 and 2003 to study the morphology and sedimentary fill of the remote El'gygytgyn crater (Chukotka, northeastern Siberia; diameter 18 km). These data allow a first insight into the deeper structure of this unique impact crater. Wide-angle data from sonobuoys reveal a five-layer model: a water layer, two lacustrine sedimentary units that fill a bowl-shaped apparent crater morphology consisting of an upper layer of fallback breccia with P-wave velocities of ˜3000 m/s, and a lower layer of brecciated bedrock (velocities >3600 m/s). The lowermost layer shows a distinct anticline structure that, by analogy with other terrestrial and lunar craters of similar size, can be interpreted as a central ring structure. The El'gygytgyn crater exhibits a well-expressed morphology that is typical of craters formed in crystalline target rocks.

  15. Ar-40-Ar-39 Age of an Impact-Melt Lithology in Lunar Meteorite Dhofar 961

    Science.gov (United States)

    Cohen, Barbara; Frasl, Barbara; Jolliff, Brad; Korotev, Randy; Zeigler, Ryan

    2016-01-01

    The Dhofar 961 lunar meteorite was found in 2003 in Oman. It is texturally paired with Dhofar 925 and Dhofar 960 (though Dhofar 961 is more mafic and richer in incompatible elements). Several lines of reasoning point to the South Pole-Aitken Basin (SPA) basin as a plausible source (Figure 2): Mafic character of the melt-breccia lithic clasts consistent the interior of SPA, rules out feldspathic highlands. Compositional differences from Apollo impact-melt groups point to a provenance that is separated and perhaps far distant from the Procellarum KREEP Terrane SPA "hot spots" where Th concentrations reach 5 ppm and it has a broad "background" of about 2 ppm, similar to lithic clasts in Dhofar 961 subsamples If true, impact-melt lithologies in this meteorite may be unaffected by the Imbrium-forming event that is pervasively found in our Apollo sample collection, and instead record the early impact history of the Moon.

  16. Rb-Sr ages and palaeomagnetic data for some Angolan alkaline intrusives

    International Nuclear Information System (INIS)

    New Rb-Sr age measurements are reported for a number of intrusives from Angola. Data for the Njoio and Tchivira nepheline syenite bodies yield mineral isochrons indicating ages of 104,3+-0,8 Ma and 130,8+-1,4 Ma respectively. Palaeomagnetic studies on the same occurrences gave marginal and scattered results respectively. Micas from the Camafuca crater-facies kimberlite yielded and apparent age of 1 822+-151 Ma, a result that is far in excess of the Tertiary (or younger) age inferred for this pipe. Similarly conflicting data were obtained for the Nova Lisboa kimberlite. It is likely that older crustal micas incorporated in the kimberlite breccias are responsible for the anomalous ages reported on the kimberlites. Satisfactory palaeomagnetic data are reported for the Zenza and Bailundu occurrences, not dated by the Rb-Sr method. A convenient K-Ar age of 80+-0,8 Ma was obtainable for Zenza

  17. Alisitos Formation, calcareous facies: Early Cretaceous episode of tectonic calm

    Energy Technology Data Exchange (ETDEWEB)

    Suarez-Vidal, F.

    1986-07-01

    The Alisitos Formation (Aptian-Albian), shaped as a marine volcanic arc, crops out along the western side of the peninsula of Baja California bounding the Peninsular Range batholith. Lithologically, this formation is formed by volcanic-breccias, porphyritic flows, biohermal limestones, and tuffaceous and pyroclastic sediments. The distribution of the different facies depends on the nature of volcanism and the distance from a volcanic center, although the presence of massive biohermal limestone indicates that in the Early Cretaceous (during the tectonic episodes), the volcanic activity decreased to the level that the environmental conditions were favorable for the development of an organic reef barrier, behind an island arc. Such conditions existed south of the Agua Blanca fault and extended to El Arco, Baja California. Based upon field observations and petrological analysis of the Alisitos limestone, an attempt is made to recreate the environmental condition in the Punta China and San Fernando, Baja California, sites.

  18. Is There any Relationship Between the Santa Elena Depression and Chicxulub Impact Crater, Northwestern Yucatan Peninsula, Mexico?

    Science.gov (United States)

    Lefticariu, L.

    2005-05-01

    isolated saline lake (Middle Eocene), and 3) shallow marine water (Middle-Late Eocene?). In places, the deeper-water facies are similar to those within the Chicxulub Sedimentary Basin. The shallow-water facies is similar to those occurring outside the Basin. In general, quartz and silicates are rare in the Cenozoic sedimentary carbonate of the northwestern Yucatan Peninsula. Therefore, their presence in the UNAM 5 core could be attributed to either impact breccia reworking or silicic volcanic processes. Quartz, chert, zeolite, and clay also are common in the suevite breccia of both Yax-1 and UNAM 5 cores. The fact that the Santa Elena Depression was a distinct sedimentary basin during much of the Paleogene could be explained by any or a combination of the following hypotheses: 1) In spite of being located outside the cenote ring, the Depression is a sub-basin of the larger and deeper Chicxulub Sedimentary Basin and is therefore located within the Chicxulub Impact Crater, 2) the Depression coincides with an impact crater distinct from the Chicxulub Impact Crater, 3) the Depression formed after the Chicxulub bolide impact due to slumping, crater wall failure, or larger-scale tectonic processes. The lack of conclusive evidence for multiple impact breccia layers in the northwestern Yucatan Peninsula, corroborated with the presence on top of the impact breccia from UNAM 5 core of deeper-water limestone similar to that of Late Paleocene-Early Eocene age from Yax-1 core, would be more consistent with either the first or third hypothesis.

  19. Geology of coal fires: case studies from around the world

    Energy Technology Data Exchange (ETDEWEB)

    Glenn B. Stracher (ed.)

    2008-01-15

    Coal fires are preserved globally in the rock record as burnt and volume-reduced coal seams and by pyrometamorphic rocks, explosion breccias, clinker, gas-vent-mineral assemblages, fire-induced faulting, ground fissures, slump blocks, and sinkholes. Coal fires are responsible for coronary and respiratory diseases and fatalities in humans, as well as arsenic and fluorine poisoning. Their heat energy, toxic fumes, and solid by-products of combustion destroy floral and faunal habitats while polluting the air, water, and soil. This volume includes chapters devoted to spontaneous combustion and greenhouse gases, gas-vent mineralogy and petrology, paralavas and combustion metamorphic rocks, geochronology and landforms, magnetic signatures and geophysical modeling, remote-sensing detection and fire-depth estimation of concealed fires, and coal fires and public policy.

  20. Dacite – siltstone peperite from Trlično at Rogatec, Eastern Slovenia

    Directory of Open Access Journals (Sweden)

    Polona Kralj

    2006-06-01

    Full Text Available Dacitic glassy lava flow at Trlično is surrounded by a dacite – siltstone peperite and peperitic breccia that underwent alteration, recognised in two, only a few metres thick zones. In the higher-temperature alteration zone, albite extensively replaces volcanic glass and primary plagioclases. The siltstone components are altered to microcrystalline quartz, iron oxides and interlayered illite/smectite clay minerals. This zone developed upon thermalmetamorphosis related to the transfer of heat from the cooling lava. In the lower temperature alteration zone, analcime occurs as the replacement of volcanic glass and pore- and fissure-filling, while the primary plagioclases and poorly lithified siltstone remained fairly unchanged. This zone developed under hydrothermal conditions related to the heating, circulation and reactions of pore waters in the sediment surrounding the lava flow.

  1. Early lunar magnetism

    Science.gov (United States)

    Banerjee, S. K.; Mellema, J. P.

    1976-01-01

    A new method (Shaw, 1974) for investigating paleointensity (the ancient magnetic field) was applied to three subsamples of a single, 1-m homogeneous clast from a recrystallized boulder of lunar breccia. Several dating methods established 4 billion years as the age of boulder assembly. Results indicate that the strength of the ambient magnetic field at the Taurus-Littrow region of the moon was about 0.4 oersted at 4 billion years ago. Values as high as 1.2 oersted have been reported (Collison et al., 1973). The required fields are approximately 10,000 times greater than present interplanetary or solar flare fields. It is suggested that this large field could have arisen from a pre-main sequence T-Tauri sun.

  2. Lunar hydrogen: A resource for future use at lunar bases and space activities

    Science.gov (United States)

    Gibson, Everett K., Jr.; Bustin, Roberta; Mckay, David S.

    1988-01-01

    Hydrogen abundances were determined for grain size separates of five lunar soils and one soil breccia. The hydrogen abundance studies have provided important baseline information for engineering models undergoing study at the present time. From the studies is appears that there is sufficient hydrogen present in selected lunar materials which could be recovered to support future space activities. It is well known that hydrogen can be extracted from lunar soils by heating between 400 and 800 C. Recovery of hydrogen for regolith materials would involve heating with solar mirrors and collecting the released hydrogen. Current baseline models for the lunar base are requiring the production of 1000 metric tons of oxygen per year. From this requirement it follows that around 117 metric tons per year of hydrogen would be required for the production of water. The ability to obtain hydrogen from the lunar regolith would assist in lowering the operating costs of any lunar base.

  3. Degradation of Endeavour Crater, Mars

    Science.gov (United States)

    Grant, J. A.; Crumpler, L. S.; Parker, T. J.; Golombek, M. P.; Wilson, S. A.; Mittlefehldt, D. W.

    2015-01-01

    The Opportunity rover has traversed portions of two western rim segments of Endeavour, a 22 km-diameter crater in Meridiani Planum, for the past three years. The resultant data enables the evaluation of the geologic expression and degradation state of the crater. Endeavour is Noa-chian-aged, complex in morphology, and originally may have appeared broadly similar to the more pristine 20.5 km-diameter Santa Fe complex crater in Lunae Palus (19.5degN, 312.0degE). By contrast, Endeavour is considerably subdued and largely buried by younger sulfate-rich plains. Exposed rim segments dubbed Cape York (CY) and Solander Point/Murray Ridge/Pillinger Point (MR) located approximately1500 m to the south reveal breccias interpreted as remnants of the ejecta deposit, dubbed the Shoemaker Formation. At CY, the Shoemaker Formation overlies the pre-impact rocks, dubbed the Matijevic Formation.

  4. Cordierite-spinel troctolite, a new magnesium-rich lithology from the lunar highlands

    Science.gov (United States)

    Marvin, U. B.; Carey, J. W.; Lindstrom, M. M.

    1989-02-01

    A clast of spineltroctolite containing 8 percent cordierite (Mg2,Al4Si5O18) has been identified among the constituents of Apollo 15 regolith breccia 15295. The cordierite and associated anorthite, forsteritic olivine, and pleonaste spinel represent a new, Mg-rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate. The cordierite-forsterite pair in the assemblage is stable at a maximum pressure of 2.5 kilobars, equivalent to a depth of 50 kilometers, or 10 kilometers above the lunar crust-mantle boundary. The occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized. The rarity of cordierite-spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events, such as the one that formed the adjacent Imbrium Basin.

  5. The formation kinetics of lunar glasses

    Science.gov (United States)

    Uhlmann, D. R.; Handwerker, C. A.; Onorato, P. I. K.; Salomaa, R.; Goncz, D.

    1978-01-01

    The kinetic treatment of crystallization and glass formation, involving the construction of time-temperature-transformation curves (TTT) corresponding to a given degree of crystallinity, is extended to permit the description of crystallization of a body initially cooled to a glassy state. The key assumption is that if at any time and temperature a crystallite is smaller than the critical size corresponding to that temperature, it will melt completely and can be ignored in any further calculations of the crystal distribution. This approach is used to predict the temperature of maximum crystallization rate for the matrix composition of lunar breccia 67975; results are shown to be in excellent agreement with experiment. Theoretical results obtained for anorthite indicate a barrier to nucleation in the range of 75 kT when the ratio of the undercooling to the liquidus temperature is 0.2. Measured nucleation barriers for the 67975 matrix composition are in the range of 42 to 45 kT.

  6. Meteorite impact craters and possibly impact-related structures in Estonia

    Science.gov (United States)

    Plado, Jüri

    2012-10-01

    Three structures (Neugrund, Kärdla, and Kaali) of proven impact origin make Estonia the most cratered country in the world by area. In addition, several candidate impact structures exist, waiting for future studies to determine their origin. This article is an overview of these proven and possible impact structures, including some breccia layers. It summarizes the information and descriptions of the morphology; geological characteristics; and mineralogical, chemical, and geophysical data available in the literature. The overview was prepared to make information in many earlier publications in local journals (many of which had been published in Estonian or Russian) accessible to the international community. This review summarizes the facts and observations in a historical fashion, summarizing the current state of knowledge with some additional comments, and providing the references.

  7. Contribution to the use of marble in Central-Lusitania in Roman times: The stone architectural decoration of Ammaia (São Salvador da Aramenha, Portugal

    Directory of Open Access Journals (Sweden)

    Taelman, Devi

    2014-12-01

    Full Text Available This paper reports the results of a quantitative and qualitative study of the imported architectural decorative stone of the Roman town of Ammaia (São Salvador da Aramenha, Portugal, located centrally in the province of Lusitania. All studied ornamental stones were counted, weighed, classified and their provenance was determined. Six types of stone were used for the architectural decoration at Ammaia: white marble, pink–purple limestone, grey– white marble, two marble breccias and granite. Granite was the most widely used building stone and was used for the production of columns and capitals. Previous studies have established a local source for the Ammaia granite (Taelman et alii in press. The provenance of the remaining ornamental stones is primarily regional (the southern part of the Iberian Peninsula. Only the two marble breccia varieties were imported from the Mediterranean: africano from Teos (Turkey and breccia di Sciro from the island of Skyros also (Greece. The predominant use of regionally available stones is observed in other Roman towns located in the interior of the Iberian Peninsula, such as Emerita Augusta, Asturica Augusta and Munigua, and results mainly from the geographic location of the sites, remote from any seaport and/or navigable river.El presente trabajo presenta los resultados de una valorización cuantitativa y cualitativa de la utilización de las piedras decorativas arquitectónicas importadas de la ciudad romana lusitana de Ammaia (São Salvador da Aramenha, Portugal. Todas las piedras decorativas estudiadas fueron contadas, pesadas, clasificadas y su procedencia fue determinada. En la época romana se utilizaron seis tipos de piedra para la decoración arquitectónica de la ciudad de Ammaia: mármol blanco, caliza morada–rosa, mármol blanco y gris, dos brechas compuestas de fragmentos de mármol blanco y granito. El granito fue la piedra de construcción principal en Ammaia. Además, el granito se utiliz

  8. Petro-mineralogical Studies of the Paleoproterozoic Phosphorites in the Sonrai basin, Lalitpur District, Uttar Pradesh, India

    Energy Technology Data Exchange (ETDEWEB)

    Dar, Shamim A., E-mail: sjshamim@gmail.com; Khan, K. F.; Khan, Saif A.; Khan, Samsuddin [Aligarh Muslim University, Department of Geology (India); Masroor Alam, M. [Aligarh Muslim University, Geology Section Department of Civil Engineering (India)

    2015-09-15

    The Paleoproterozoic phosphorites constitute an economically significant component of the Sonrai basin of Lalitpur district. These are associated with ferruginous shale, ironstone, limestone and quartz breccia. Petro-mineralogical studies of samples of the phosphorites, using X-ray diffractometry and scanning electron microscopy, reveal that the collophane (carbonate-fluorapatite) is the dominant phosphate mineral. Calcite, dolomite, quartz, mica and haematite are the dominant gangue constituents. The phosphate minerals occur as oolites mutually replaced by carbonate and silica. The presence of iron oxides has been found in most of the thin sections. There is meagre evidence of organic matter in the form of filaments of microbial phosphate laminae in the samples of phosphorite. The mineral assemblages, their texture and various forms in these phosphorites may be due to some environmental vicissitudes followed by replacement processes and biogenic activities.

  9. Trace geochemistry of lunar material

    Science.gov (United States)

    Morrison, G. H.

    1974-01-01

    The lunar samples from the Apollo 16 and 17 flights which were analyzed include soil, igneous rock, anorthositic gabbro, orange soil, subfloor basalt, and norite breccia. Up to 57 elements including majors, minors, rare earths and other trace elements were determined in the lunar samples. The analytical techniques used were spark source mass spectrometry and neutron activation analysis. The latter was done either instrumentally or with group radiochemical separations. The differences in abundances of the elements in lunar soils at the various sites are discussed. With regard to the major elements only Si is about the same at all the sites. A detailed analysis which was performed on a sample of the Allende meteorite is summarized.

  10. Pairing Relationships Among Feldspathic Lunar Meteorites from Miller Range, Antarctica

    Science.gov (United States)

    Zeigler, Ryan A.; Korotev, R. L.; Jolliff, B. L.

    2012-01-01

    The Miller Range ice fields have been amongst the most prolific for lunar meteorites that ANSMET has searched [1-3]. Six different stones have been recovered during the 2005, 2007, and 2009 field seasons: MIL 05035 (142 g), MIL 07006 (1.4 g), MIL 090034 (196 g), MIL 090036 (245 g), MIL 090070 (137 g), and MIL 090075 (144 g). Of these, the five stones collected during the 2007 and 2009 seasons are feldspathic breccias. Previous work on the Miller Range feldspathic lunar meteorites (FLMs) has suggested that they are not all paired with each other [4-5]. Here we examine the pairing relationships among the Miller Range FLMs using petrography in concert with traceand major-element compositions.

  11. Thermal Analyses of Apollo Lunar Soils Provide Evidence for Water in Permanently Shadowed Areas

    Science.gov (United States)

    Cooper, Bonnie L.; Smith, M. C.; Gibson, E. K.

    2011-01-01

    Thermally-evolved-gas analyses were performed on the Apollo lunar soils shortly after their return to Earth [1-8]. The analyses revealed the presence of water evolving at temperatures above 200 C. Of particular interest are samples that were collected from permanently-shadowed locations (e.g., under a boulder) with a second sample collected in nearby sunlight, and pairs in which one was taken from the top of a trench, and the second was taken at the base of the trench, where the temperature would have been -10 to -20 C prior to the disturbance [9]. These samples include 63340/63500, 69941/69961, and 76240/76280. At the time that this research was first reported, the idea of hydrated minerals on the lunar surface was somewhat novel. Nevertheless, goethite was observed in lunar breccias from Apollo 14 [10], and it was shown that goethite, hematite and magnetite could originate in an equilibrium assemblage of lunar rocks

  12. Petro-mineralogical Studies of the Paleoproterozoic Phosphorites in the Sonrai basin, Lalitpur District, Uttar Pradesh, India

    International Nuclear Information System (INIS)

    The Paleoproterozoic phosphorites constitute an economically significant component of the Sonrai basin of Lalitpur district. These are associated with ferruginous shale, ironstone, limestone and quartz breccia. Petro-mineralogical studies of samples of the phosphorites, using X-ray diffractometry and scanning electron microscopy, reveal that the collophane (carbonate-fluorapatite) is the dominant phosphate mineral. Calcite, dolomite, quartz, mica and haematite are the dominant gangue constituents. The phosphate minerals occur as oolites mutually replaced by carbonate and silica. The presence of iron oxides has been found in most of the thin sections. There is meagre evidence of organic matter in the form of filaments of microbial phosphate laminae in the samples of phosphorite. The mineral assemblages, their texture and various forms in these phosphorites may be due to some environmental vicissitudes followed by replacement processes and biogenic activities

  13. Catastrophic erosion of Hellas basin rim on Mars induced by magmatic intrusion into volatile-rich rocks

    Science.gov (United States)

    Tanaka, K.L.; Kargel, J.S.; MacKinnon, D.J.; Hare, T.M.; Hoffman, N.

    2002-01-01

    Malea and Hesperia Plana form large sectors of the rim of Hellas basin that display partly eroded volcanic shields and plains. These regions have topographic profiles that appear to be several hundred meters lower than those of adjacent rim sectors and lack prominent massifs of remnant basement that would be expected to stand above the lava plains. We interpret that before the volcanic edifices were constructed, these regions were denuded by an early stage of voluminous sill intrusion into friable, volatile-rich impact breccia. Magma-volatile interactions may have resulted in catastrophic generation of debris flows deposited into the adjacent basin, particularly if CO2 were involved. Later, lavas covered the eroded terrain; in turn, the lavas were eroded locally by volatile interactions. Across Mars, huge channel systems, erosional features in volcanic terranes, and vast layered deposits may be due to magma-volatile interactions.

  14. A condensed middle Cenomanian succession in the Dakota Sandstone (Upper Cretaceous), Sevilleta National Wildlife Refuge, Socorro County, New Mexico

    Science.gov (United States)

    Hook, S.C.; Cobban, W.A.

    2007-01-01

    The upper part of the Dakota Sandstone exposed on the Sevilleta National Wild-life Refuge, northern Socorro County, New Mexico, is a condensed, Upper Cretaceous, marine succession spanning the first five middle Cenomanian ammonite zones of the U.S. Western Interior. Farther north in New Mexico these five ammonite zones occur over a stratigraphic interval more than an order of magnitude thicker. The basal part of this marine sequence was deposited in Seboyeta Bay, an elongate east-west embayment into New Mexico that marked the initial transgression of the western shoreline of the Late Cretaceous seaway into New Mexico. The primary mechanism for condensing this section was nearshore, submarine erosion, although nondeposition played a minor role. The ammonite fossils from each zone are generally fragments of internal molds that are corroded on one side, indicating submarine burial, erosion of the prefossilized steinkern, and corrosion on the sea floor. In addition, the base of the condensed succession is marked by a thin bed that contains abundant, white-weathering, spherical to cylindrical phosphate nodules, many of which contain a cylindrical axial cavity of unknown origin. The nodules lie on the bedding surface of the highly burrowed, ridge-forming sand-stone near the top of the Dakota and occur in the overlying breccia. The breccia consists of rip-up clasts of sandstone and eroded internal molds of the ammonite Conlinoceras tarrantense, the zonal index for the basal middle Cenomanian. The nodules below the breccia. imply a time of erosion followed by nondeposition or sediment bypass during which the phosphatization occurred. The breccia implies a time of submarine erosion, probably storm-related. Remarkably, this condensed succession and the basal part of the overlying Mancos Shale tongue contain one of the most complete middle Cenomanian ammonite sequences in the U.S. Western Interior. Five of the six ammonite zones that characterize the middle Cenomanian of the

  15. First data for deep seated xenoliths and mantle geotherms of Zarnitsa kimberlite pipe, Daldyn, Yakutia.

    Science.gov (United States)

    Ashchepkov, Igor; Pokhilenko, Nikolai; Vladykin, Nikolai; Spetsius, Zdislav; Logvinova, Alla; Palessky, Stanislav; Khmelnikova, Olga; Shmarov, Gleb

    2014-05-01

    First discovered in Yakutia and the largest in Daldyn region kimberlite pipe is composed from several phases including breccias and porphyric kimberlites. Commonly mantle xenolith from this pipe especially included in the prevailing grey breccia are nearly completely altered. Only relatively fresh material from the brownish - grey breccia from the drilling core and porphyric kimberlites includes material which could be used for the mineral thermobarometry. The picroilmenites from the Zarnitsa pipe are forming three clusters according to the Cr- content: 0.5; 1.0 and 2.5 % Cr2O3 (Ashchepkov,Amshinsky, Pokhilenko, 1980; Amshinsky, Pokhilenko,1984; Alymova et al., 2003) due to the different contamination degree of protokimberlites in mantle peridotites. The ilmenites from porphyric kimberlites are forming stepped trend consisting from three groups of different pressure intervals from 6.5 to 4.0 GPa but more continuous than those determined for the ilmenites from breccia (Ashchepkov et al ., 2010). The relatively low Cr diopsides are corresponding to the deeper part while those containing to 2 -3 of Cr2O3 are from the middle part of the mantle section and are in association with the phlogopites contain the reflecting processes of the protokimbelite differentiation and contamination. Peridotites from the lithosphere base are of Hi temperature type and slightly Fe - enriched and are referred to the porphyroclustic types where garnets contain up to 10% Cr2O3 are they are relatively low in TiO2. But there are alos varieties of reduced Cr and the Fe-enriched which are closer to the deformed type (Agashev et al., 2013). The cold clot in the 60-5.5 GPa (34 mwm-2) are represented by Fe- low peridotites with the garnets of sub-Ca types. The Cr- low and LT eclogites are correspondent to the low 4.5-6.0 GPa interval similar to those from Udachnaya pipe. But near the pyroxenites lens the varieties enriched in Fe and sometimes hybrid pyroxenites appear like in most pf mantle

  16. Multiple shallow level sill intrusions coupled with hydromagmatic explosive eruptions marked the initial phase of Ferrar large igneous province magmatism in northern Victoria Land, Antarctica

    Science.gov (United States)

    Viereck-Goette, L.; Schöner, R.; Bomfleur, B.; Schneider, J.

    2007-01-01

    Field data gathered during GANOVEX IX (2005/2006) in Northern Victoria Land, Antarctica, indicate that volcaniclastic deposits of phreatomagmatic eruptions (so-called Exposure Hill Type events) are intercalated with fluvial deposits of Triassic-Jurassic age at two stratigraphic levels. Abundant scoriaceous spatter (locally welded) indicates a hawaiian/strombolian component. Breccia-filled diatremes, from which volcaniclastic deposits were sourced, are rooted in sills which intruded wet sediments. The deposits are thus subaerial expressions of initial Ferrar magmatism involving intrusion of multiple shallow-level sills. Due to magma-sediment interaction abundant clastic dikes are developed that intrude the sediments and sills. All igneous components in the volcaniclastic deposits are andesitic in composition, as are the chilled margins of the sills. They are more differentiated than the basaltic andesites of the younger effusive section of Kirkpatrick plateau lavas which in northern Victoria Land start with pillow lavas and small volume lava flows from volcanic necks.

  17. Rocks of the early lunar crust

    Science.gov (United States)

    James, O. B.

    1980-01-01

    Data are summarized which suggest a model for the early evolution of the lunar crust. According to the model, during the final stages of accretion, the outer part of the moon melted to form a magma ocean approximately 300 km deep. This ocean fractionated to form mafic and ultramafic cumulates at depth and an overlying anorthositic crust made up of ferroan anorthosites. Subsequent partial melting in the primitive mantle underlying the crystallized magma ocean produced melts which segregated, moved upward, intruded the primordial crust, and crystallized to form layered plutons consisting of Mg-rich plutonic rocks. Intense impact bombardment at the lunar surface mixed and melted the rocks of the two suites to form a thick layer of granulated debris, granulitic breccias, and impact-melt rocks.

  18. Survey of lunar plutonic and granulitic lithic fragments

    Science.gov (United States)

    Bickel, C. E.; Warner, J. L.

    1978-01-01

    A catalog of lunar plutonic rocks and granulitic impactites belonging to the ANT suite has been compiled. The coarser-grained, plutonic rocks in the compilation are probably pristine; they belong to two groups, Mg-rich plutonic rocks and anorthosites, with a preponderance of the latter type. The granulitic impactites, however, have bulk and mineral compositions that fall between the two groups defined by the pristine nonmare samples of Warren and Wasson (1977). Thus the granulitic impactites may have originated by metamorphism of mixed impactites in early breccia sheets. The catalog, representative of the lunar crust before the end of heavy bombardment, suggests a crust with over 78 vol. % plagioclase and about equal proportions of material with noritic and troctolitic affinity.

  19. The ancient lunar crust, Apollo 17 region

    Science.gov (United States)

    James, O. B.

    1992-01-01

    The Apollo 17 highland collection is dominated by fragment-laden melt rocks, generally thought to represent impact melt from the Serenitatis basin-forming impact. Fortunately for our understanding of the lunar crust, the melt rocks contain unmelted clasts of preexisting rocks. Similar ancient rocks are also found in the regolith; most are probably clasts eroded out of melt rocks. The ancient rocks can be divided into groups by age, composition, and history. Oldest are plutonic igneous rocks, representing the magmatic components of the ancient crust. The younger are granulitic breccias, which are thoroughly recrystallized rocks of diverse parentages. The youngest are KREEPy basalts and felsites, products of relatively evolved magmas. Some characteristics of each group are given.

  20. Chemistry and petrology of Apollo 17 highland coarse fines - Plutonic and melt rocks

    Science.gov (United States)

    Laul, J. C.; Gosselin, D. C.; Galbreath, K. C.; Simon, S. B.; Papike, J. J.

    1989-01-01

    A suite of 21 fragments from the Apollo 17 coarse-fines consists of ferroan anorthosites, anorthositic gabbros, granulitic and regolith breccias, and impact melts. These samples belong to known petrographic and chemical groups. Three ferroan anorthosites were found, including one which appears to be the lowest in REE (La = 0.60X) and probably the purest of the Apollo 17 anorthosites identified thus far. The ferroan suite is a more important component at the Apollo 17 site than previously recognized. The Apollo 17 melt rocks are similar to other samples with LKFM and low-K KREEP compositions and show less diversity in trace elements (REE) than the Apollo 15 melt rocks. Apollo 17 melt rocks consist of aphanitic and poikilitic types that show some compositional variability with identical Ni/Ir, suggesting that either two distinct melt sheets formed by similar projectiles, or compositional heterogeneity within one melt sheet is possible.

  1. Potassium determinations using SEM, FAAS and XRF: some experimental notes

    Science.gov (United States)

    Liritzis, I.; et al.

    The calibration of Scanning Electron Microscopy coupled with Energy Dispersive X- Rays Spec-trometry (SEM-EDS) for elemental quantitative analysis is an important task for characterization, provenance and absolute dating purposes. In particular the potassium determination is an im-portant contributor to dose rate assessments in luminescence and Electron Spin Resonance (ESR) dating. Here a SEM-EDX is calibrated on different archaeological and geoarchaeological materials against standard laboratory samples as well as measured by micro X-Rays Fluorescence (μXRF) and flame atomic absorption spectroscopy (FAAS) techniques. A common linear relationship is obtained for most elements and certain rock types used and two clear linear regressions for two types of rocks; one for granite, diorite, microgranite and sediments and another ceramic sherds, soils, marble schists, breccia. Such linear regressions become readily available for a future fast, efficient and accu-rate way of potassium determination.

  2. A Further Investigation of the Exceptional Zircon Aggregate in Lunar Thin Section 73235,82

    Science.gov (United States)

    Pidgeon, R. T.; Nemchin, a. A.; Meyer, C.

    2005-01-01

    Introduction: Smith et al. described an exceptional zircon assemblage in thin section 82 from lunar breccia 73235 which, in transmitted light, resembles a cluster of pomegranate seeds, situated in a clast dominated by bytownite (Fig.1). They reported that high-contrast back-scattered electron (BSE) images of the zircon assemblage clearly show an overgrowth around most of the crystals. Most significantly these authors reported that the age of the rims of ca 4.18Ga is 120 million years younger than age of the interiors, dated at ca 4.31Ga. Smith et al. concluded that ca 4.31 billion years ago a relatively large (500+micron) zircon crystallized within a clast of Ca rich plagioclase. The zircon was fractured into numerous smaller crystals and was subsequently overgrown by a second generation of zircon at approximately 4.18Ga.

  3. Thermal diffusivity of four Apollo 17 rock samples

    Science.gov (United States)

    Horai, K.-I.; Winkler, J. L., Jr.

    1976-01-01

    The modified Angstrom technique was used to measure the thermal diffusivity of four Apollo 17 rock samples in air at pressures of 1 atm and one-millionth torr in the temperature range 80-460 K, and in CO2 at different pressures for various temperature ranges and at different temperatures for the range of interstitial CO2 gas pressure 1 atm to 0.0001 torr. The experiments with CO2 were intended to simulate Martian conditions, and it was found that the thermal diffusivity of lunar crystalline basalt and breccia varies very little with temperature in a simulated Martian environment, which indicates that the thermal processes in the Martian regolith could be more straightforward than in the lunar regolith.

  4. Kimberlite Wall Rock Fragmentation: Venetia K08 Pipe Development

    Science.gov (United States)

    Barnett, W.; Kurszlaukis, S.; Tait, M.; Dirks, P.

    2009-05-01

    Volcanic systems impose powerful disrupting forces on the country rock into which they intrude. The nature of the induced brittle deformation or fragmentation can be characteristic of the volcanic processes ongoing within the volcanic system, but are most typically partially removed or obscured by repeated, overprinting volcanic activity in mature pipes. Incompletely evolved pipes may therefore provide important evidence for the types and stages of wall rock fragmentation, and mechanical processes responsible for the fragmentation. Evidence for preserved stages of fragmentation is presented from a detailed study of the K08 pipe within the Cambrian Venetia kimberlite cluster, South Africa. This paper investigates the growth history of the K08 pipe and the mechanics of pipe development based on observations in the pit, drill core and thin sections, from geochemical analyses, particle size distribution analyses, and 3D modeling. Present open pit exposures of the K08 pipe comprise greater than 90% mega-breccia of country rock clasts (gneiss and schist) with explosive early stage of fragmentation that pre-conditions the rock mass. The pre-conditioning would have been caused by explosions that are either phreatic or phreatomagmatic in nature. The explosions are likely to have been centered on a dyke, or pulses of preceding volatile-fluid phases, which have encountered a local hydrologically active fault. The explosions were inadequate in mechanical energy release (72% of a mine production blast) to eject material from the pipe, and the pipe may not have breached surface. The next stage of fragmentation is interpreted to have been an upward-moving collapse of the pre-conditioned hanging wall of a subterranean volcanic excavation. This would explain the mega-scale layering across the width of the breccia pipe. It must be questioned whether the preserved K08 architecture represents early pipe development in general, or is a special case of a late pipe geometry modification

  5. Elemental compositions and ages of lunar samples by nondestructive gamma-ray spectrometry.

    Science.gov (United States)

    O'kelley, G D; Eldridge, J S; Schonfeld, E; Bell, P R

    1970-01-30

    A gamma-ray spectrometry system with low background was used to determine the radioactivity of crystalline rocks, breccias, and fine material. Nuclides identified were (40)K, (232)Th, (238)U, (7)Be, (22)Na (26)A1, (44)Ti, (46)Sc, (48)V, (52)Mn, (54)Mn, and (56)Co. Concentrations of K, Th, and U ranged between 480 and 2550, 1.01 and 3.30, and 0.26 and 0.83 parts per million, respectively. Concentrations of thorium and uranium were those of terrestrial basalts, while the potassium concentrations were near values for chondrites. Products of low-energy nuclear reactions showed pronounced concentration gradients at rock surfaces. Concentrations of K and of (22)Na determined here were combined with concentrations of rare gases to estimate gas-retention ages and cosmic-ray exposure ages with ranges of 2200 to 3200 and 34 to 340 million years, respectively, for three rocks. PMID:17781504

  6. Petrophysical Analysis of Oil Sand in Athabasca

    Science.gov (United States)

    cheong, S.; Lee, H.

    2013-12-01

    Oil sands are the major unconventional energy sources which have great reserves in Alberta, Canada. Recovery techniques such as CSS (Cyclic Steam Stimulation) and SAGD (Steam Assisted Gravity Drainage) enabled to develop deeper bitumen about several hundred meter depth. Before applying CSS and SAGD, reservoir heterogeneity of mud barriers or shale breccias should be clarified to establish injection and production wells successfully. We conducted the integrated petro-physical analysis for oil sands deposits in Athabasca by correlating well logs with seismic data. From 33 well logs and 3D seismic, we have made P-wave impedance by recursive inversion. Target formations of our analysis were the top of Wabiskaw member. Using inverted impedance and multi-attributes, porosity volume was derived at a target depth. Porosity of time slice 375 ms ranged 20 ~ 40 % stretching porous sand body from NE to SW direction. Characteristics of porosity distribution may be useful to design optimum oil sands recovery in Athabasca.

  7. Gypsum karst in Great Britain

    Directory of Open Access Journals (Sweden)

    Cooper A.H.

    1996-01-01

    Full Text Available In Great Britain the most spectacular gypsum karst development is in the Zechstein gypsum (late Permian mainly in north-eastern England. The Midlands of England also has some karst developed in the Triassic gypsum in the vicinity of Nottingham. Along the north-east coast, south of Sunderland, well-developed palaeokarst, with magnificent breccia pipes, was produced by dissolution of Permian gypsum. In north-west England a small gypsum cave system of phreatic origin has been surveyed and recorded. A large actively evolving phreatic gypsum cave system has been postulated beneath the Ripon area on the basis of studies of subsidence and boreholes. The rate of gypsum dissolution here, and the associated collapse lead to difficult civil engineering and construction conditions, which can also be aggravated by water abstraction.

  8. Dawn and the Vesta-HED Connection

    Science.gov (United States)

    McSween, H. Y.; Mittlefehldt, D. W.; Beck, A. W.; McCoy, T.; Marchi, S.; DeSanctis, M. C.; Ammannito, E.; Raymond, C. A.; Russell, C. T.

    2012-01-01

    Although it is difficult to explain exactly how eucrites and diogenites are related through simple magmatic processes, their shared oxygen isotopic compositions and the common occurrence of clasts of both lithologies in howardite breccias support derivation from a common parent body. For decades, HED meteorites have been linked to asteroid 4 Vesta, based on spectral similarities [1] and the discovery of a dynamical family (Vestoids) that provides a bridge between Vesta and nearby resonance escape hatches [2]. Although recently derived constraints on the rapidity of HED parent body differentiation, based on measurements of Al-26 in diogenites, have been used to argue against the Vesta-HED connection [3], new thermal evolution models [e.g., 4] appear to be heated and melted fast enough to account for this constraint. Data from the Dawn orbiter strengthen the Vesta - HED linkage and provide new insights into petrogenetic interpretations of these meteorites.

  9. Geology of the Desert Hot Springs-Upper Coachella Valley Area, California (with a selected bibliography of the Coachella Valley, Salton Sea, and vicinity)

    Energy Technology Data Exchange (ETDEWEB)

    Proctor, Richard J.

    1968-01-01

    The Desert Hot Springs area is in the upper Coachella Valley at the junction of three natural geomorphic provinces of California--the Transverse Ranges, the Peninsular Ranges, and the Colorado Desert. The mapped area is about 100 miles east of Los Angeles and lies principally in north central Riverside County. The oldest rocks in the area are Precambrian(?) amphibolitic and migmatized paragneisses of the San Gorgonio igneous-metamorphic (Chuckwalla) complex. They are intruded by Cretaceous diorite porphyry, Cactus Granite, quartz monzonite, intrusive breccia, and basic plutonic rocks. Of probable late Paleozoic age are the metamorphic rocks of the San Jacinto Mountains which form spurs projecting into San Gorgonio Pass and Coachella Valley.

  10. Geophysical characterisation of two segments of the Møre-Trøndelag Fault Complex, Mid Norway

    Directory of Open Access Journals (Sweden)

    A. Nasuti

    2011-07-01

    Full Text Available The Møre-Trøndelag Fault Complex (MTFC has controlled the tectonic evolution of Mid Norway and its shelf for the past 400 Myr through repeated reactivations during Palaeozoic, Mesozoic and perhaps Cenozoic times, the very last phase of reactivation involving normal to oblique-slip faulting. Despite its pronounced signature in the landscape, its deep structure has largely remained unresolved until now. We focused on two specific segments of the MTFC (i.e. the Tjellefonna and Bæverdalen faults and acquired multiple geophysical datasets (i.e. gravity, magnetic, resistivity and shallow refraction profiles.

    A 100–200 m-wide zone of gouge and/or brecciated bedrock steeply dipping to the south is interpreted as being the Tjellefonna fault sensu stricto. The fault appears to be flanked by two additional but minor damage zones. A secondary normal fault also steeply dipping to the south but involving indurated breccias was detected ~1 km farther north. The Bæverdalen fault, ~12 km farther north, is interpreted as a ~700 m-wide and highly deformed zone involving fault gouge, breccias and lenses of intact bedrock. As such, it is probably the most important fault segment in the studied area and accommodated most of the strain during presumably Late Jurassic normal faulting. Our geophysical data are indicative of a Bæverdalen fault dipping steeply towards the south, in agreement with the average orientation of the local tectonic grain. Our findings suggest that the influence of Mesozoic normal faulting along the MTFC on landscape development is more complex than previously thought.

  11. The Hot—Spring Genesis of the Shimen Realgar Deposit,Northwest Hunan

    Institute of Scientific and Technical Information of China (English)

    张景荣; 王蔚; 等

    1993-01-01

    The Shimen realgar deposit is characterized by the pipi-shaped orebody and the development of silica sinter and hydrothermal explosive breccia which are typical of hot spring activity.Very similar trace-element associations are noticed between the silica cap and the breccia and modern hot spring waters in the area.The chemistr of ore-forming solutions is also well comparable with that of modern hot spring.,The spring system that gave rise to the mineralization was charged by ground waters heated through thermal conducting systems in the deep crust and,to a lesser extent,by geothermal gradient.ΔD,δ18O,δ13CCH4andδ13CH4andδ13CCO2values and 40Ar/36Ar and 3He/4He ratios indicate that the spring system is of crustal derivation.The ore-forming metals were supplied by surrounding strata,particularly those underlying the ore deposits.The mechanim of ore deposition is thought to be hydrothermal explosion and accompanying boiling and abrupt changes in pH and Eh.Located in northwest Hunan,the Shimen realgar deposit is the leading arsenic producer in the country,However,regardless of its long mining history,the genesis of this deposit has long been a puzzle.It was considered to be postmagmatic epithermal in the leading arsenic producer in the puzzle.It Was considered to be postmagmatic epithermal in origin,but this is trongly challenged by filling(metasomatism)in karst environment proposed later by Zhou Zhiquan(1986)also encounters a number of difficulties.For example,why can the pipi-shaped orebody vertically extend up to several hundreds meters without any compatible development in the lateral dimension? A hot spring genesis is suggested in the present paper based on geological observations and laboratory studies conducted by the authors in recent years.

  12. Aeromagnetic anomaly modeling of the central sector of the Chicxulub impact structure

    Science.gov (United States)

    Rebolledo-Vieyra, M.; Urrutia-Fucugauchi, J.; Lopez-Loera, H.; Delgado-Rodriguez, O.

    2003-04-01

    We propose an updated model of the Chicxulub impact structure based on modeling of the aeromagnetic anomaly data, which incorporates electromagnetic sounding models and UNAM and CSDP borehole information. Modeling takes into account the relative contributions of the induced and remanent components. Studies of the magnetic susceptibility variation in the UNAM and Yaxcopoil boreholes along the lithologic column in the crater area reveal that the suevite-like breccias have a stronger magnetic signature than that of the impact-melt. The crystalline component estimated from clasts analyses in the suevite-like breccias has a higher magnetic susceptibility (up to 1200x10-5 SI) than that of the impact melt (~500x10-5 SI) and the crystalline basement (400x10-5 SI). Reduction to the pole and downward continuations document a fragmented character of the anomaly. The second-derivative of the magnetic anomaly depicts five concentric rings within the anomaly, the last ring correlates with the cenote ring, supporting the its relation with the buried structure. The analytical signal and the radially averaged spectrum yield an estimate of the depth to the magnetic sources, ranging from 1000 to 6000 m. Using this data, new 2-D magnetic models were developed, which suggest that the fragmented character of the northern portion of the crater might be controlled by system of near vertical faults. The main central anomaly is produced by a central uplift that is ~2500 m deep, from ground level, in the central area of the crater. Geophysical models are developed and compared with borehole information for the area of the Yaxcopoil-1 well, drilled recently as part of the Chicxulub Scientific Drilling Project and the International Continental Scientific Drilling Program.

  13. Mineralogy and chemistry of Rumuruti: The first meteorite fall of the new R chondrite group

    Science.gov (United States)

    Schulze, H.; Bischoff, A.; Palme, H.; Spettel, B.; Dreibus, G.; Otto, J.

    1994-03-01

    The Rumuruti meteorite shower fell in Rumuruti, Kenya, on 1934 January 28 at 10:45 p.m. Rumuruti is an olivine-rich chondritic breccia with light-dark structure. Based on the coexistence of highly recrystallized fragments and unequilibrated components, Rumuruti is classified as a type 3-6 chondrite breccia. The most abundant phase of Rumuruti is olivine (mostly Fa(approximately 39) with about 70 vol%. Feldspar (approximately 14 vol%; mainly plagioclase), Ca-pyroxene (5 vol%), pyrrhotite (4.4 vol%), and pentlandite (3.6 vol%) are major constituents. All other phases have abundances below 1 vol%, including low-Ca pyroxene, chrome spinels, phosphates (chlorapatite and whitlockite), chalcopyrite, ilemenite, tridymite, Ni-rich and Ge-containing metals, kamacite, and various particles enriched in noble metals like Pt, Ir, and Au. The chemical composition of Rumuruti is chondritic. The depletion in refractory elements (Sc, REE, etc.) and the comparatively high Mn, Na, and K contents are characteristic of ordinary chondrites and distinguish Rumuruti from carbonaceous chondrites. However, S, Se, and Zn contents in Rumuruti are significantly above the level expected for ordinary chondrites. The oxygen isotope composition of Rumuruti is high in delta O-17 (5.52%) and delta O-18 (5.07%). With Rumuruti, nine meteorites samples exist that are chemically and mineralogically very similar. These meteorites are attributed to at least eight different fall events. It is proposed in this paper to call this group R chondrites (rumurutites) after the first and only fall among these meteorites. The meteorites have a close relationship to ordinary chondrites. However, they are more oxidized than any of the existing groups of ordinary chondrites. Small, but significant differences in chemical composition and in oxygen isotopes between R chondrites and ordinary chondrites exclude formation of R chondrites from ordinary chondrites by oxidation. This implies a separate, independent R chondrite

  14. Eocene age of the Baranowski Glacier Group at Red Hill, King George Island, West Antarctica

    Directory of Open Access Journals (Sweden)

    Mozer Anna

    2015-12-01

    Full Text Available Radiometric and geochemical studies were carried out at Red Hill in the southern part of King George Island (South Shetland Islands, northern Antarctic Peninsula on the Bransfield Strait coast. The rock succession at Red Hill has been determined to represent the Baranowski Glacier Group that was previously assigned a Late Cretaceous age. Two formations were distinguished within this succession: the lower Llano Point Formation and the upper Zamek Formation. These formations have stratotypes defined further to the north on the western coast of Admiralty Bay. On Red Hill the Llano Point Formation consists of terrestrial lavas and pyroclastic breccia; the Zamek Formation consist predominantly of fine to coarse tuff, pyroclastic breccia, lavas, tuffaceous mud-, silt-, and sandstone, locally conglomeratic. The lower part of the Zamek Formation contains plant detritus (Nothofagus, dicotyledonous, thermophilous ferns and numerous coal seams (vitrinitic composition that confirm the abundance of vegetation on stratovolcanic slopes and surrounding lowlands at that time. Selected basic to intermediate igneous rocks from the succession have been analysed for the whole-rock K-Ar age determination. The obtained results indicate that the Red Hill succession was formed in two stages: (1 from about 51–50 Ma; and (2 46–42 Ma, i.e. during the Early to Middle Eocene. This, in combination with other data obtained from other Baranowski Glacier Group exposures on western coast of Admiralty Bay, confirms the recently defined position of the volcano-clastic succession in the stratigraphic scheme of King George Island. The new stratigraphic position and lithofacies development of the Red Hill succession strongly suggest its correlation with other Eocene formations containing fossil plants and coal seams that commonly occur on King George Island.

  15. The architecture of an incipient oceanic basin: a tentative reconstruction of the Jurassic Liguria-Piemonte basin along the Northern Apennines-Alpine Corsica transect

    Science.gov (United States)

    Marroni, Michele; Pandolfi, Luca

    2007-11-01

    In this paper, a scenario for the early evolution of the Jurassic oceanic Liguria-Piemonte basin is sketched. For this purpose, four selected examples of ophiolite sequences from the Northern Apennines and Corsica are described and analyzed. In the External Ligurian units (Northern Apennines), the ocean-continent transition of the Adria plate was characterized by a basement made up of subcontinental mantle and lower continental crust, covered by extensional allochthons of upper crust. Both, the basement rocks and the extensional allochthons are cut by basaltic dikes and covered by basalts and pelagic deposits. The conjugate ocean-continent transition of the Corsica margin, represented by the Balagne nappe (Corsica), was composed of mantle peridotites and gabbros covered by basaltic flows and minor breccias, that in addition include continent-derived clasts. By contrast, the innermost (i.e., closest to the ocean) preserved area observed in the Internal Ligurian (Northern Apennines) and Inzecca (Corsica) units consists of former morphological highs of mantle peridotites and gabbros, bordered by small basins where the basement is covered by a volcano-sedimentary complex, characterized by ophiolitic breccias and cherts interlayered with basaltic flows. The overall picture resulting from our reconstructions suggests an asymmetric architecture for the Liguria-Piemonte basin with a central area bounded by two different transition zones toward the continental margins. This architecture can be interpreted as the result of a rifting process whose development includes a final stage characterized by passive, asymmetric extension of the lithosphere along an east-dipping detachment fault system.

  16. Geology and geochemistry of high-grade, volcanic rock-hosted, mercury mineralisation in the Nuevo Entredicho deposit, Almadén district, Spain

    Science.gov (United States)

    Jébrak, Michel; Higueras, Pablo L.; Marcoux, Éric; Lorenzo, Saturnino

    2002-06-01

    The Nuevo Entredicho deposit contains the richest concentration of mercury in the Almadén district, locally grading as much as 45% Hg. This ore deposit is hosted within an alkaline, conically shaped diatreme, about 150 m in diameter, which was subsequently filled with phreatomagmatic breccias. The diatreme cuts an Ordovician to Silurian clastic sedimentary rock sequence that is intercalated with basaltic sills. Structural analysis reveals a complex tectonic history with three main phases of Hercynian deformation. Mineralisation occurs as cinnabar replacements in volcanic tuffs and breccias and as recrystallised veins in tensions cracks associated with pyrophyllite and hydrothermal pyrite, which is strongly enriched in Cu, Pb and Hg. Lead isotopes in pyrite are characterised by high 207Pb/204Pb ratios (15.70-15.75), suggesting a contribution of ancient upper continental crust remobilised by Silurian-Devonian volcanism, with no mantle involvement. Sulphur isotopes of epigenetic cinnabar and pyrite range from +10.3 to +10.8‰ and from +10.6 to +11.9‰ respectively, suggesting a uniform sulphur source or a constant mixing ratio in the ore fluids. These isotopic compositions differ from those measured in the syngenetic deposits of the Almadén district; they suggest a higher temperature of ore formation of about 300 °C, and a genesis related to a distinct hydrothermal flow path at the Nuevo Entredicho deposit. Deposition of anomalously high-grade mercury ore at Nuevo Entredicho is related to a combination of (1) an abundance of black shale that provided sulphur and increasingly reducing conditions with high sulphide/sulphate ratios, (2) explosive Silurian-Devonian mafic magmatism that provided an initial source of mercury, (3) tectonic activity that lead to structurally favourable sites for ore deposition, and (4) replacement of secondary, carbonate-rich volcanic rocks.

  17. Chemical and Mineralogical Features of Smectite from the Morron de Mateo Bentonite Deposit (Cabo de Gata, Almeria) in Relation to the Parent Rocks and the Alteration Processes Occurred After the Bentonite Formation: Analogies and Implications for the Engineered Clayey Barrier of a Deep Geological Rad waste Repository; Naturaleza de las Esmectitas del Yacimiento de Morron de Mateo (Cabo de Gata, Almeria) en Relacion con la Roca Madre y con los Procesos Posteriores a la Bentonitizacion: Implicaciones Analogicas para la Barrera de Ingenieria de un Almacenamiento Geologico de Residuos Radiactivos

    Energy Technology Data Exchange (ETDEWEB)

    Pelayo, M.; Labajo, M. A.; Garcia Romero, L.; Perez del Villar, L.

    2009-10-12

    The Morron de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemical effects on the clayey barrier of a Deep Geological Rad waste Repository (DGRR) after its closure, in relation to the radioactive decay of the fission products and the container corrosion. This bentonite deposit and their host rocks were intruded by a rhyodacitic volcanic dome that induced a hydrothermal metasomatic process affecting the bioclastic calcarenite beds close to the dome. Bentonite from the NE sector of the deposit have been chemically and mineralogically characterized. Pyroclastic rocks (white tuffs), epyclastic rocks (mass flow) and andesitic breccia all of them hydrothermally altered, have been studied at the site. Samples are composed of feldspars, quartz and amphybols, as inherited minerals, and phyllosilicates, zeolites, crystoballite and calcite, as new formed minerals. White tuffs have the highest phyllosilicate contents, mainly dioctahedral smectite of montmorillonite type. Epyclastic rocks and andesitic breccia have a highest proportion of inherited minerals, the new formed phillosilicates being di octahedral smectite of beidellite type and an ordered interlayer chlorite/smectite mineral, of corrensite type. Smectite from the epyclastic rocks have higher Fe and Mg contents and chemical variability, as a consequence of nature of their parent rocks. The presence of corrensite in the epyclastic rocks suggests that in the Morron de Mateo area a propilitic alteration process occurred after bentonite formation, which transformed Fe-Mg-rich smectite into corrensite. This transformation was probably favoured by the sub volcanic intrusion, which also produced a temperature increase in the geological media and a supply of Fe-Mg-rich solutions, which also were the responsible for the metasomatic transformations observed in the calcarenite beds. (Author) 57 refs.

  18. Mineral chemistry of paleoproterozoic volcano-plutonism from the São Félix do Xingu (PA region, Amazonian Craton

    Directory of Open Access Journals (Sweden)

    Raquel Souza da Cruz

    2014-03-01

    Full Text Available The Sobreiro and Santa Rosa formations are result of large paleoproterozoic volcanic activities in the São Félix do Xingu (PA region, SE of Amazonian Craton. The Sobreiro Formation is composed of andesitic lava flow facies, with subordinate dacite and rhyodacite, and autoclastic volcaniclastic facies characterized by tuff, lapilli-tuff, and massive polymictic breccia. These rocks exhibit clinopyroxene, amphibole, and plagioclase phenocrysts in a microlytic or trachytic groundmass. The clinopyroxene is augite with subordinate diopside, and reveals chemical variations typical of minerals generated by arc-related magmatism. The amphibole is magnesiohastingsite, has oscillatory oxidizing conditions, and reveals breakdown rim textures linked to degassing during magma ascent. The Santa Rosa Formation has polyphase evolution controlled by large NE-SW crustal fissures, materialized by rhyolitic and dacitic lava flow facies. Volcaniclastic facies of ignimbrites, lapilli-tuffs, felsic crystal tuffs, and massive polymict breccias represents an explosive cycle in this unit. Metric dikes and stocks of granitic porphyries and equigranular granitoids complete this suite. K-feldspar, plagioclase, and quartz phenocrysts surrounded by quartz and K-feldspar integrowth occur in these rocks. Electron microprobe pressure and temperature estimates in clinopyroxene phenocrysts reveal formation depth between 58 and 17.5 km (17.5 – 4.5 kbar at temperatures between 1,249 and 1,082 ºC; and between 28 and 15 km (7.8 – 4.1 kbar for amphibole grains of the Sobreiro Formation, suggesting polybaric evolution. A model with generation of hydrated basaltic magma from partial melting of mantle wedge and accumulation in a hot zone of the lower crust, from which the andesitic and dacitic magmas are formed by the assimilation of continental crust and following fractional crystallization is proposed.

  19. HYDROGEOLOGICAL AND HYDROCHEMICAL FEATURES OF KALNIK MASSIF

    Directory of Open Access Journals (Sweden)

    Vinko Mraz

    2008-12-01

    Full Text Available Kalničko gorje consists of Cretaceous – Holocene sediments, which can be in hydrogeological sense classified in three hydrogeological units: (1 northern area from central massive of Kalnik, consists of Cretaceous and low Miocene impermeable and low permeable sediments which are hydrogeological barrier and low permeable Cretaceous eruptive sediments ; (2 Kalnik massive consists of Paleogen and Baden permeable carbonate – clastic sediments, which are aquifer; (3 southern Kalnik area consists of Neogene low permeable sediments and Quaternary medium permeable unconsolidated deposits. In the hydrogelogical units are several aquifers types: (i Paleogen carbonate aquifer consists of limestone – dolomite breccia and this is the most important aquifer in the Kalnik area; (ii Baden carbonate aquifer consists of lithothamnium, lithothamnium limestone, sandstone and breccia-conglomerate and it has high permeability, especially through the karst morphological features; (iii Quaternary alluvial aquifers – the most important is in the valley of the Kamešnica river and it’s permeability varies from poor to good depending on granulometric properties; (iv Cretaceous eruptive aquifer from which in the Apatovac area is abstraction of mineral water. The aquifers of the Kalnik area are very vulnerable considering the hydrogeological properties of the area. Nevertheless, physical, physicalchemical, and chemical properties of groundwater in the Kalnik area are showing that waters are of very good quality. The reasons of good quality of waters are that the area is poorly populated and there is no potential pollutant. The area is very valuable and important natural resource for water supply of whole region. In the future it is necessary to provide good protection and sustainable water management to obtain today’s good quality and quantity of groundwater (the paper is published in Croatian.

  20. Fluid-rock interactions in seismic faults: Implications from the structures and mineralogical and geochemical compositions of drilling cores from the rupture of the 2008 Wenchuan earthquake, China

    Science.gov (United States)

    Duan, Qingbao; Yang, Xiaosong; Ma, Shengli; Chen, Jianye; Chen, Jinyu

    2016-01-01

    We describe the structural features and mineralogical and geochemical compositions of the fault rocks recovered from boreholes at the Golden River site on the Yingxiu-Beichuan fault, which activated and slipped along a 240 km-long main surface rupture zone during the 2008 Wenchuan earthquake. The fault, which accommodated co-seismic slip, cuts granitic rocks from the Pengguan complex, in which this earthquake most likely nucleated. Fault rocks, including cohesive cataclasite, unconsolidated breccia and three fault gouges with distinct colors, were identified from the drilling cores. On-going uplift and erosion in the area means that the fault rocks, formed at different depth, were exhumed to the shallow surface during the uplift history of the Longmenshan fault zone. A clear change from fracturing and comminution in the cataclasites and breccia to more pervasive shear/formation of fine grained materials in the gouges has been observed. The gouges are distinct and have accommodated significant displacement in multiple increments of shear. Furthermore, fault rocks recovered from the boreholes display numerous features indicative of fluid infiltration and fluid-rock interaction. Toward the fault core, clay minerals have replaced feldspars. The element enrichment/depletion patterns of the fault rocks show general fluid infiltration trends, such as 1) mobile elements are generally depleted in the fault rocks, 2) the microstructural, mineralogical and geochemical results of the fault rocks consistently indicate that pervasive fluid infiltration and fluid-rock interactions altered feldspars and mafic minerals to clay minerals. The fluid was Mg2 +- and Fe2 +-rich, facilitating formation of chlorite. Isocon analyses further reveal that a large rock volume has been lost, which is attributed to the removal of mobile elements associated with fluid infiltration and perhaps enhanced by pressure solution. These results reflect the accumulated effects of cataclasis and fluid

  1. LA-ICP-MS zircon U-Pb dating and phenocryst EPMA of dikes, Guocheng, Jiaodong Peninsula: Implications for North China Craton lithosphere evolution

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Widespread dike swarm, including diorite-, monzonite-porphyry and lamprophyre, intruded in the al- tered breccia gold deposits along basin marginal faults, Guocheng, Jiaodong Peninsula. Petrography exhibits biotite enclaves in amphibole phenocrysts and the presence of acicular apatites in these dikes. Electron probe microanalyses (EPMA) show that the amphibole and clinopyroxene phenocryst’s mantle in diorite porphyry and lamprophyre respectively has sharply higher MgO (Mg#) and Cr2O3 contents in contrast to their cores. The plagioclase phenocryst in monzonite porphyry has reverse zoning. These results indicate that the magma mixing between mantle-derived mafic and crust-derived felsic magmas occurred in the original process of the dikes. Zircon cathodoluminescence (CL) images show well-developed magmatic oscillatory zones and the acquired LA-ICP-MS zircon U-Pb weighted mean 206Pb/238U ages are 114±2 Ma (MSDW=1.5) for monzonite porphyry (GS1) and 116±1 Ma (MSDW=0.8) for diorite porphyry (GS2), respectively. Earlier magmatic events in the northwest Jiaodong Peninsula represented by some inherited or captured zircons also occur in these dikes. Magmatic zircons from GS1 and GS2 display consistent chondrite-normalized REE patterns and Nb/Ta values, implying that they may share a similar or same source. HREE enrichment and obvious negative Eu anomalies of these zircons preclude garnet presented in their source. Our results, combined with preciously pub- lished data, indicate that dike intrusion and gold mineralization among quartz vein, altered tectonite and altered breccia gold deposits are broadly contemporaneous throughout the Jiaodong Peninsula. These also imply that the intensive crust-mantle interaction and asthenospheric underplating had oc- curred in the Early Cretaceous in the Peninsula, together with foundering of lower crust in the early Mesozoic, representing the different stages of lithosphere thinning in the North China Craton (NNC).

  2. LA-ICP-MS zircon U-Pb dating and phenocryst of dikes, Guocheng, Jiaodong Peninsula: Implications for North China Craton lithosphere evolution

    Institute of Scientific and Technical Information of China (English)

    TAN Jun; WEI JunHao; GUO LingLi; ZHANG KeQing; YAO ChunLiang; LU JianPei; LI HongMei

    2008-01-01

    Widespread dike swarm, including diorite-, monzonite-porphyry and lamprophyre, intruded in the altered breccia gold deposits along basin marginal faults, Guocheng, Jiaodong Peninsula. Petrography exhibits biotite enclaves in amphibole phenocrysts and the presence of acicular apatites in these dikes.Electron probe microanalyses (EPMA) show that the amphibole and clinopyroxene phenocryst's mantle in diorite porphyry and lamprophyre respectively has sharply higher MgO (Mg#) and Cr203 contents in contrast to their cores. The plagioclase phenocryst in monzonite porphyry has reverse zoning. These results indicate that the magma mixing between mantle-derived mafic and crust-derived felsic magmas occurred in the original process of the dikes. Zircon cathodoluminescence (CL) images show well-developed magmatic oscillatory zones and the acquired LA-ICP-MS zircon U-Pb weighted mean 206pb/238U ages are 114±2 Ma (MSDW=1.5) for monzonite porphyry (GS1) and 116±1 Ma (MSDW=0.8) for diorite porphyry (GS2), respectively. Earlier magmatic events in the northwest Jiaodong Peninsula represented by some inherited or captured zircons also occur in these dikes. Magmatic zircons from GSl and GS2 display consistent chondrite-normalized REE patterns and Nb/Ta values, implying that they may share a similar or same source. HREE enrichment and obvious negative Eu anomalies of these zircons preclude garnet presented in their source. Our results, combined with preciously published data, indicate that dike intrusion and gold mineralization among quartz vein, altered tectonite and altered breccia gold deposits are broadly contemporaneous throughout the Jiaodong Peninsula.These also imply that the intensive crust-mantle interaction and asthenospheric underplating had occurred in the Early Cretaceous in the Peninsula, together with foundering of lower crust in the early Mesozoic, representing the different stages of lithosphere thinning in the North China Craton (NNC).

  3. The Hyblean xenolith suite (Sicily): an unexpected legacy of the Ionian-Tethys realm

    Science.gov (United States)

    Manuella, Fabio Carmelo; Scribano, Vittorio; Carbone, Serafina; Brancato, Alfonso

    2015-07-01

    The extensive study of a great number of deep-seated xenoliths from Tortonian tuff-breccia pipes in the Hyblean area (Sicily) revealed the following fundamental evidence: (1) typical continental crust rocks are completely absent in the entire xenolith suite; (2) mantle ultramafics are more abundant than gabbroids; (3) sheared oxide-gabbros, closely resembling those from oceanic fracture zones, are relatively common; (4) secondary mineral assemblages, compatible with alteration processes in serpentinite-hosted hydrothermal systems, occur both in peridotites and gabbros. Among the products of this hydrothermal activity, organic compounds, having abiotic origin via Fischer-Tropsch synthesis, occur in some hydrothermally altered gabbro and ultramafic xenoliths, as well as in hydrothermal clays. Moreover, the U-Pb dating of hydrothermal zircon grains, hosted in a xenolith of metasomatized tectonic breccia, indicated an Early-Middle Triassic age of the fossil hydrothermal system. Another line of evidence for the oceanic nature of the Hyblean-Pelagian basement is the complete absence of continental crust lithologies (granites, felsic metaigneous, and metasedimentary rocks) in outcrops and in boreholes, and the oceanic affinity of the Tertiary volcanic rocks from the Hyblean Plateau and the Sicily Channel (Pantelleria and Linosa Islands), which lack of any geochemical signature for continental crust contamination. A reappraisal of existing geophysical data pointed out that serpentinites form the dominant lithologies in the lithospheric basement of the Hyblean-Pelagian area down to a mean depth of 19 km, which represents the regional Moho considered as the serpentinization front, marking the transition from serpentinites to unaltered peridotites. On these grounds, we confirm that Hyblean xenoliths contain mineralogical, compositional, and textural evidence for tectonic, magmatic, and hydrothermal processes indicating the existence of fossil oceanic core complexes, in the

  4. Iron-rich fragments in the Yamansu iron deposit, Xinjiang, NW China: Constraints on metallogenesis

    Science.gov (United States)

    Li, Hou-Min; Ding, Jian-Hua; Zhang, Zhao-Chong; Li, Li-Xing; Chen, Jing; Yao, Tong

    2015-12-01

    Volcanic rock-hosted iron deposits are among the important iron ores in China. However, the nature of primary magma and petrogenesis associated with these iron ores remains controversial. Here, we report iron-rich fragments (IRF) from the Yamansu iron deposit in Eastern Tianshan Mountains, NW China, which occurs in association with volcanic breccia, submarine volcanic breccia and ignimbrite. The IRF is composed of five types including oligoclase-iron oxide type (OIO), oligoclase-albite-iron oxide type (OAIO), albite-iron oxide type (AIO), albite-K-feldspar-iron oxide type (AKIO) and K-feldspar-iron oxide type (KIO). These fragments display typical volcanic fabric features, such as porphyritic texture, hyalopilitic texture of the groundmass and vesicles filled by minerals to form amygdales. The feldspar phenocrysts of IRF are dominantly albite. The groundmass of IRF consists of magnetite and feldspar. The magnetite is distributed in between the feldspar laths, and together display hyalopilitic texture which could be observed only in volcanic rocks. The vesicles are filled with magnetite, feldspar, chlorite and calcite from the margin to the interior. The IRF has high Si, Al, Fe, Ca, Ti, Na and K contents and low Mg content. The average total Fe is 26 wt.%. The magnetite is mostly titanium-vanadium magnetite, with the TiO2 content ranging up to 4.86 wt.% and V2O3 content up to 3.20 wt.%. The IRF probably came from iron-rich melts and represent the products of the Fenner magma evolution. The basaltic magma evolved into the Fe-Na-rich residual melts by crystallization under low oxygen fugacity condition in a closed magma chamber after intruding into the shallow crust. The Fe-Na-rich residual melts were emplaced in hypabyssal environments or erupted generating the orebodies or providing the material source for the generation of the high-grade iron ores which were subsequently enriched by the late-stage hydrothermal fluids.

  5. Chemical and Mineralogical Features of Smectite from the Morron de Mateo Bentonite Deposit (Cabo de Gata, Almeria) in Relation to the Parent Rocks and the Alteration Processes Occurred After the Bentonite Formation: Analogies and Implications for the Engineered Clayey Barrier of a Deep Geological Rad waste Repository

    International Nuclear Information System (INIS)

    The Morron de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemical effects on the clayey barrier of a Deep Geological Rad waste Repository (DGRR) after its closure, in relation to the radioactive decay of the fission products and the container corrosion. This bentonite deposit and their host rocks were intruded by a rhyodacitic volcanic dome that induced a hydrothermal metasomatic process affecting the bioclastic calcarenite beds close to the dome. Bentonite from the NE sector of the deposit have been chemically and mineralogically characterized. Pyroclastic rocks (white tuffs), epyclastic rocks (mass flow) and andesitic breccia all of them hydrothermally altered, have been studied at the site. Samples are composed of feldspars, quartz and amphybols, as inherited minerals, and phyllosilicates, zeolites, crystoballite and calcite, as new formed minerals. White tuffs have the highest phyllosilicate contents, mainly dioctahedral smectite of montmorillonite type. Epyclastic rocks and andesitic breccia have a highest proportion of inherited minerals, the new formed phillosilicates being di octahedral smectite of beidellite type and an ordered interlayer chlorite/smectite mineral, of corrensite type. Smectite from the epyclastic rocks have higher Fe and Mg contents and chemical variability, as a consequence of nature of their parent rocks. The presence of corrensite in the epyclastic rocks suggests that in the Morron de Mateo area a propilitic alteration process occurred after bentonite formation, which transformed Fe-Mg-rich smectite into corrensite. This transformation was probably favoured by the sub volcanic intrusion, which also produced a temperature increase in the geological media and a supply of Fe-Mg-rich solutions, which also were the responsible for the metasomatic transformations observed in the calcarenite beds. (Author) 57 refs

  6. Maintaining the uranium resources data system and assessing the 1989 US uranium potential resources

    International Nuclear Information System (INIS)

    Under the Memorandum of Understanding (MOU) between the EIA, US Department of Energy, and the US Geological Survey (USGS), US Department of the Interior, the USGS develops estimates of uranium endowment for selected geological environments in the United States. New estimates of endowment are used to update the Uranium Resources Assessment Data (URAD) System which, beginning in 1990, is maintained for EIA by the USGS. For 1989, estimates of US undiscovered resources were generated using revised economic index values (current to December 1989) in the URAD system's cost model. The increase in the estimates for the Estimated Additional Resources (EAR) and Speculative Resources (SR) classes resulted primarily from increases in the estimates of uranium endowment for the solution-collapse, breccia-pipe uranium deposit environment in the Colorado Plateau resource region. The mean values for $30-, $50-, and $100-per-pound U3O8 forward-cost categories of EAR increased by about 8, 48, and 32 percent, respectively, as compared to 1988. Estimates of the 1989 undiscovered resources in the SR class also increased in all three forward-cost categories by 10, 5, and 9 percent, respectively. The original cost equations in the URAD System were designed to cover drilling costs related to extensive flat-lying tabular ore bodies. The equations do not adequately treat drilling costs for the smaller areas of vertical breccia pipe uranium deposits in the Colorado Plateau resource region. The development of appropriate cost equations for describing the economics of mining this type of deposit represents a major new task. 12 refs., 4 figs., 5 tabs

  7. Petrographic and geochemical characteristics of the ignimbritic units containing uranium mineralization of the Sierra Pena Blanca, Mexico

    International Nuclear Information System (INIS)

    The Sierra Pena Blanca, which is characterized by Miocene-Plioquaternary Basin and Range tectonics, is a mountain range 70 km long oriented NNW-SSE and located 50 km to the north of the city of Chihuahua. This range is divided into two parts: a southern one with outcrops of old Palaeozoic and Mesozoic series and a northern one in which the Eocene ignimbritic sequence lies in unconformity over the folded Mesozoic series. The Eocene volcanic sequence consists of five cooling units locally separated by levels of calcareous breccias, conglomerates or arenites; the first two units were deposited at 43.5+-1 MA and the other three at 37.8+-0.5 MA. The uranium mineralization is found in the oldest ignimbritic units with the exception of the El Nopal I deposit which is of the breccia pipe type and is situated in the second cooling unit (Nopal ''rhyolite'' - Escuadra ''rhyolite''); the El Nopal deposit is either on the border between the lava flows (El Nopal III) or is well disseminated (El Puerto III and Las Margaritas). The Nopal and Escuadra ''rhyolites'', which are rich in silicon (75+-0.5%) and in alkalines (>8%) are noted for their K2O contents of above 6%; this is a primary characteristic confirmed by the composition of the vitreous inclusions of quartz phenocrysts (Na2O+K2O>10%-K2O=6.3+-0.1%) predating post-depositional processes which, on the other hand, have influenced the percentage of Na2O, causing the chemical compositions to move in the direction of hyperaluminosity. Developed rhyolites are enriched in Th (35 ppm) and U (10 ppm); this continuous background is sufficient to permit in situ remobilization as a result of the circulation of fluids linked with the escape of gases

  8. Epithermal uranium deposits in a volcanogenic context: the example of Nopal 1 deposit, Sierra de Pena Blanca, Mexico

    Science.gov (United States)

    Calas, G.; Angiboust, S.; Fayek, M.; Camacho, A.; Allard, T.; Agrinier, P.

    2009-12-01

    The Peña Blanca molybdenum-uranium field (Chihuahua, Mexico) exhibits over 100 airborne anomalies hosted in tertiary ignimbritic ash-flow tuffs (44 Ma) overlying the Pozos conglomerate and a sequence of Cretaceous carbonate rocks. Uranium occurrences are associated with breccia zones at the intersection of two or more fault systems. Periodic reactivation of these structures associated with Basin and Range and Rio Grande tectonic events resulted in the mobilization of U and other elements by meteoric fluids heated by geothermal activity. Trace element geochemistry (U, Th, REE) provides evidence for local mobilization of uranium under oxidizing conditions. In addition, O- and H-isotope geochemistry of kaolinite, smectite, opal and calcite suggests that argillic alteration proceeded at shallow depth with meteoric water at 25-75 °C. Focussed along breccia zones, fluids precipitated several generations of pyrite and uraninite together with kaolinite, as in the Nopal 1 mine, indicating that mineralization and hydrothermal alteration of volcanic tuffs are contemporaneous. Low δ34S values (~ -24.5 ‰) of pyrites intimately associated with uraninite suggest that the reducing conditions at the origin of the U-mineralization arise from biological activity. Later, the uplift of Sierra Pena Blanca resulted in oxidation and remobilization of uranium, as confirmed by the spatial distribution of radiation-induced defect centers in kaolinites. These data show that tectonism and biogenic reducing conditions can play a major role in the formation and remobilization of uranium in epithermal deposits. By comparison with the other uranium deposits at Sierra Pena Blanca and nearby Sierra de Gomez, Nopal 1 deposit is one of the few deposits having retained a reduced uranium mineralization.

  9. Volcanic geology and geochemistry of Motuhora (Whale Island), Bay of Plenty, New Zealand

    International Nuclear Information System (INIS)

    Motuhora (Whale Island) lies c. 11 km offshore from Whakatane in the Bay of Plenty, New Zealand, and comprises tuffaceous marine sediments of the Camp Bay and Motuhora Formations separated by lavas, volcanic breccias, and slope-wash deposits of the Whale Volcanics. Whale Volcanics can be divided into East Dome, Central Dome Complex, and Pa Hill Dome. East Dome is a flow banded, chaotically jointed dacite that is probably extrusive. Central Dome comprises lava flows, and extensive volcanic breccias and tuffs which thicken into a local depression to the north of the central high, suggesting rapid growth and erosion of the dome. Pa Hill Dome is largely intrusive into Camp Bay Formation, although blocks of Pa Hill dacite in an upper slope-wash cobble bed suggest it was partially extrusive. The lavas are porphyritic with phenocrysts of plagioclase, orthopyroxene, and titanomagnetite with subordinate clinopyroxene and amphibole (particularly in Pa Hill Dome), and rare biotite. Rounded or broken and embayed quartz crystals are found in the Central Dome Complex and Pa Hill domes. Magmatic xenoliths are common in all lavas. Chemically the lavas are medium-K, calc-alkaline andesites and dacites, and show relative LILE enrichment and HFSE depletion typical of arc volcanics. Isotopically, samples tend to have more radiogenic Sr and less radiogenic Nd than volcanics from neighbouring White Island. It is likely that Motuhora lavas were formed by a multi-stage process involving partial melting of N-MORB-type mantle that had been fluxed by fluids rich in incompatible elements derived from the dehydrating downgoing slab and followed by crystal fractionation of the magma. As the magma rose through the lower continental crust it was contaminated, probably by Torlesse metasediment. Petrographic textures and mineral chemistry indicate that magma mixing, while in an upper crustal magma chamber, is the norm for Motuhora lavas. (author). 69 refs., 12 figs., 2 tabs

  10. Non-explosive magma water interaction in a continental setting: Miocene examples from the Eastern Cordillera (central Andes; NW Argentina)

    Science.gov (United States)

    Vezzoli, Luigina; Matteini, Massimo; Hauser, Natalia; Omarini, Ricardo; Mazzuoli, Roberto; Acocella, Valerio

    2009-07-01

    The Middle-Upper Miocene Las Burras Almagro-El Toro (BAT) igneous complex within the Eastern Cordillera of the central Andes (˜24°S; NW Argentina) has revealed evidence of non-explosive interaction of andesitic magma with water or wet clastic sediments in a continental setting, including peperite generation. We describe and interpret lithofacies and emplacement mechanisms in three case studies. The Las Cuevas member (11.8 Ma) comprises facies related to: (i) andesite extruded in a subaqueous setting and generating lobe-hyaloclastite lava; and (ii) marginal parts of subaerial andesite lava dome(s) in contact with surface water, comprising fluidal lava lobes, hyaloclastite, and juvenile clasts with glassy rims. The Lampazar member (7.8 Ma) is represented by a syn-volcanic andesite intrusion and related peperite that formed within unconsolidated, water-saturated, coarse-grained volcaniclastic conglomerate and breccia. The andesite intrusion is finger-shaped and grades into intrusive pillows. Pillows are up to 2 m wide, tightly packed near the intrusion fingers, and gradually become dispersed in the host sediment ≥50 m from the parent intrusion. The Almagro A member (7.2 Ma) shows evidence of mingling between water-saturated, coarse-grained, volcaniclastic alluvial breccia and intruding andesite magma. The resulting intrusive pillows are characterized by ellipsoidal and tubular shape and concentric structure. The high-level penetration of magma in this coarse sediment was unconfined and irregular. Magma was detached in apophyses and lobes with sharp contacts and fluidal shapes, and without quench fragmentation and formation of a hyaloclastite envelope. The presence of peperite and magma water contact facies in the BAT volcanic sequence indicates the possible availability of water in the system between 11 7 Ma and suggests a depositional setting in this part of the foreland basin of the central Andes characterized by an overall topographically low coastal floodplain

  11. Age of Cu-Au mineralisation, Cloncurry district, eastern Mt Isa Inlier, Queensland, as determined by 40Ar/39Ar dating

    International Nuclear Information System (INIS)

    The 40Ar/39Ar dating of alteration biotite. muscovite and amphibole from a number of post-peak metamorphic Cu-Au deposits and alteration systems in the Cloncurry district. north Queensland has determined the timing of mineralisation and hydrothermal activity. Alteration biotite from the Ernest Henry Cu-Au, Starra Au-Cu, and Mt Elliott Cu-Au deposits, sericite associated with hematite breccias in the Wimberu Granite, muscovite from an albitite pipe that intrudes the Gilded Rose Breccia. And sericite from a granitoid near the Osborne Cu-Au deposit. yield ages which are broadly contemporaneous with the late ca 1510-1485 Ma phases of the Williams and Naraku Batholiths. Hornblende and biotite alteration, which pre-date Cu-Au mineralisation at Osborne. give a maximum age of ca 1540 Ma for the deposit. which is also a probable minimum age for peak metamorphism. Metamorphic minerals from the vicinity of Osborne yield dates which are significantly older (ca 1590-1570 Ma) than those from the hydrothermal phases. Dating by the K-Ar method of red. Hematitic K-feldspars which are regionally common in the Cloncurry district was not effective as the mineral yields ages up to 300 million years younger than coexisting alteration sericite. The 40Ar/39Ar age spectra obtained from most hydrothermal phases in the Eastern Fold Belt. Mt Isa Inlier commonly contain flat parts which comprise a large proportion of the released gas and are indicative of rapid cooling through the temperature of partial closure to Ar diffusion for the respective minerals. Copyright (1998) Blackwell Science Asia

  12. Feldspathic Meteorites MIL 090034 and 090070: Late Additions to the Lunar Crust

    Science.gov (United States)

    Nyquist, L. E.; Shirai, N.; Yamaguchi, A.; Shih, C.-Y.; Park, J.; Ebihara, M.

    2016-01-01

    Our studies of the Miller Range lunar meteorites MIL 090034, 090036, and 090070 show them to be a diverse suite of rocks from the lunar highlands hereafter referred to as MIL 34, MIL 36, and MIL 70, resp. MIL34 and MIL70, the focus of this work, are crystalline melt breccias. Plagioclase compositions in both peak sharply around An96-97. Mg numbers of olivine vary from 58-65 with a few higher values. MIL36 is a regolith breccia. MIL 34 and MIL 70 have some of the highest Al2O3 abundances of lunar highland meteorites, indicating that they have among the largest modal abundances of plagioclase for lunar meteorites. They have lower Sc and Cr abundances than nearly all lunar highland meteorites except Dho 081, Dho 489 and Dho 733. MIL34 and MIL70 also have similar cosmic ray exposure (CRE) ages of approximately 1-2 Ma indicating they are launch paired. (MIL36 has a larger CRE age approximately greater than 70 Ma). Park et al. found a variation in Ar-Ar ages among subsamples of MIL 34 and MIL70, but preferred ages of 3500+/-110 Ma for the "Dark" phase of MIL 34 anorthite and 3520+/-30 Ma for the "Light" phase of MIL70. Bouvier et al. reported a Pb-Pb age of 3894+/-39 Ma for a feldspathic clast of MIL 34 and a similar age for a melt lithology. Here we reexamine the Rb-Sr and Sm-Nd isotopic data, which show complexities qualitatively consistent with those of the Ar-Ar and Pb-Pb data. The Sm-Nd data in particular suggest that the feldspathic compositions of MIL 34 and MIL 70 formed during initial lunar geochemical differentiation, and REE modeling suggests a relatively late-stage formation.

  13. Significance of age relations above and below upper Jurassic ophiolite in the Geysers--Clear Lake region, California

    Energy Technology Data Exchange (ETDEWEB)

    McLaughlin, R.J.; Pessagno, E.A. Jr.

    1978-01-01

    In The Geysers--Clear Lake area of northern California, a fragmented Upper Jurassic ophiolite overlain depositionally by the Great Valley sequence is juxtaposed over deformed and metomorphosed rocks of the Franciscan assemblage along the Coast Range thrust. The basal strata of the Great Valley sequence consist of thick breccias of mafic clasts, identical in composition to the upper part of the ophiolite. These breccias and their contact relations suggest that more than 1 km of the upper part of the ophiolite was locally eroded in early Tithonian time. On the basis of their radiolarian faunas, cherts in the Franciscan assemblage below the ophiolite range in age from Late Jurassic (early Tithonian) to Late Cretaceous (early Cenomanian). Of particular significance is an individual chert body (=The Geysers chert) of this age range. The early Cenomanian radiolarians, except for two occurrences associated with pelagic limestone, are significantly younger than those previously reported from the Franciscan assemblage. The existence of a sequence of Late Jurassic to Late Cretaceous radiolarian chert places critical constraints on subduction models for emplacement of the Franciscan assemblage beneath the Coast Range ophiolite and Great Valley sequence in The Geysers--Clear Lake area. From early Tithonian to post-early Cenomanian time, the Franciscan assemblage received pelagic sedimentation far from any site of subduction. By other data, blueschist metamorphism of subducted Franciscanstrata also occurred during this time. The radiolarian data from The Geysers area permit a correlation with Upper Cretaceous pelagic limestones in the Laytonville area northwest of The Geysers and also imply that the Great Valley sequence was never depositionally in contact with the Franciscan assemblage.

  14. Diagenesis of the Lisburne Group, northeastern Brooks Range, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, R.C.; Goldstein, R.H.; Enos, P. [and others

    1995-05-01

    Petrographic cathodoluminescence studies of the cement stratigraphy of the Lisburne Group yield insights on its diagenetic history. Crosscutting relationships between features of subaerial exposure and calcite cements show that early generations of nonferroan, nonluminescent and multibanded-luminescent calcites are synchronous with or postdated by subaerial exposure surfaces within the Lisburne. Surfaces of subaerial exposure occur at 18 horizons within the Lisburne and are distinguished by features as laminated crusts, rhizoliths, autoclastic breccia, fissure fills, mud cracks, and erosional surfaces. Crosscutting relationships also occur between calcite cements and clasts in karst breccias and conglomerates that formed along the sub-Permian unconformity at the top of the Lisburne. The sub-Permian unconformity postdates later generations of calcite cement. These cements formed in the following sequence: nonferroan to low-ferroan, dully luminescent calcite; ferroan, very-dully luminescent calcite; and second generation of nonferroan, multibanded calcite. The crosscutting relationships not only constrain the timing of cement precipitation, but also suggest that the cements probably were precipitated from meteoric groundwaters introduced during subaerial exposure of the Lisburne platform. Late cements in the Lisburne postdate the Permian Echooka Formation. These cements are low-ferroan, moderately-bright to dully luminescent calcite, followed by a second generation of ferroan, very-dully luminescent calcite. Features of compaction and pressure solution are coincident with the precipitation of the late ferroan calcite and further constrain its timing to deep burial of the Lisburne. The youngest phase of calcite cement precipitated in the Lisburne Group is nonferroan, very-dully luminescent calcite. It commonly fills tectonically-induced shear fractures, indicating precipitation after the onset of Cretaceous (and/or Cenozoic) tectonism in the northeastern Brooks Range.

  15. Lithological and Petrographic Analyses of Carbonates and Sandstones From the Southern Gulf of Mexico

    Science.gov (United States)

    Garcia-Avendaño, A.; Urrutia-Fucugauchi, J.

    2012-04-01

    We present results of sedimentological and petrological studies of drill cores from the Bay of Campeche in the southern Gulf of Mexico. Based on reports on drill cores obtained from oil exploratory wells in the Cantarell Complex located 80 kilometres offshore in the Bay of Campeche and studies related to regional geology composite simplified stratigraphic columns for offshore Campeche region have been constructed up to depths of approximately 5000 m. The stratigraphic column is formed by a thick sediment sequence of Middle Jurassic age (evaporites, Callovian), Late Jurassic (terrigenous, calcareous clays and calcareous layers), Lower Cretaceous (carbonates), Upper Cretaceous-Paleogene (calcareous breccias), Paleogene-Neogene (terrigenous-carbonates intercalations) and Quaternary (terrigenous). The core samples studied come from wells in the Sihil and Akal fields in Cantarell. Analysis of reports on lithological descriptions indicates that these wells sample dolomitized sedimentary breccias from the Upper Cretaceous-Paleocene and fine-grained sandstones from the Late Jurassic Tithonian, respectively. Based on results of petrographic studies, the texture, cementing material and porosity of the units have been documented. The thin sections for carbonates were classified based on their texture according to Dunham (1962) for carbonate rocks, classified according to their components using the ternary diagrams of Folk (1974). Percentages refer to the data presented in tables, which were obtained by point-counting technique (with a total 250). Photomicrographs of scanning electron microscope (SEM) provide magnification for easy documentation of crystalline arrangements and description of micro-porous for different types of carbonates such as dolomite, in addition to the morphology of authigenic clays. Results of these studies and previous works in the area permit characterization of diagenetic processes of the carbonate sediments in the Campeche Bay, and provide

  16. Geophysical characterisation of two segments of the Møre-Trøndelag Fault Complex, Mid-Norway

    Directory of Open Access Journals (Sweden)

    A. Nasuti

    2011-02-01

    Full Text Available The Møre-Trøndelag Fault Complex (MTFC has controlled the tectonic evolution of Mid-Norway and its shelf for the past 400 Myr through repeated reactivations during Paleozoic, Mesozoic and perhaps Cenozoic times, the very last phase of reactivation involving normal to oblique slip faulting. Despite its pronounced signature in the landscape, its deep structure has remained unresolved until now. We focused on two specific segments of the MTFC (i.e. the so-called "Tjellefonna" and "Bæverdalen" faults and acquired multiple geophysical data sets (i.e. gravity, magnetic, resistivity and shallow refraction profiles. A 100–200 m wide zone of gouge and/or brecciated bedrock dipping steeply to the south is interpreted as being the "Tjellefonna Fault" stricto sensu. The fault appears to be flanked by two additional but minor damage zones. A secondary normal fault also steeply dipping to the south but involving indurated breccias was detected ~1 km farther north. The "Bæverdalen Fault" is interpreted as a ~700 m wide and highly deformed zone involving fault gouge, breccias and lenses of intact bedrock, as such it is probably the most important fault segment in the studied area and accommodated most of the strain during presumably late Jurassic normal faulting. Our geophysical data are indicative of a "Bæverdalen Fault" dipping steeply towards the south, in agreement with the average orientation of the local tectonic grain. Our findings suggest that the influence of Mesozoic normal faulting along the MTFC on landscape development is more complex than previously anticipated.

  17. Modelling Singhbhum uranium mineralization in the light of Proterozoic uranium metallogeny

    International Nuclear Information System (INIS)

    In mineral deposit modelling, a conceptual or genetic model is preferred to other ones when it is not dogmatic. The characteristics and genesis of major Proterozoic uranium deposits, such as the quartz-pebble conglomerate -type deposits, Franceville deposit, copper belt type deposits, Beaverlodge lake deposits, unconformity - type deposits, the fluidized hematite breccia deposit of Olympic dam, and the albitite - type deposits are discussed. They are grouped into four principal genetic types: (a) palaeoplacer - type, (b) (diagenetic - ) metamorphic - type, (c) the hydrothermal hematitic breccia type, and (d) metasomatic - type. There may be some amount of overprinting of a principal mechanism of ore formation by the features of a later process. In 'a' the original depositional and diagenetic features are still considerably maintained. Type 'b' is generally polygenetic and their genetic history is not always traceable. Type 'c' is hydrothermal, but atypical is being hematite-rich and the nature and origin of the ore fluid and the source of ore-elements in the hydrothermal fluid are far from clear. Albitite - uranium is also an important ore type in the Proterozoic, but far less discussed in the geological literature in English. 'a' and 'b' and 'd' are divisible into sub-types, depending on details. Occurrence along a zone of pronounced ductile (-brittle) shearing close to an Archean-Proterozoic boundary, ore participation in the metamorphic-metasomatic petrography and the ore bodies obeying the L-S structures, confirm an earlier conclusion that the uranium mineralization along the Singhbhum copper-uranium belt belongs to the metamorphic-metasomatic type. It rather belongs to the Beaverlodge lake sub-type. (author). 42 refs., 7 figs

  18. Geology and petrology of Lages Alkaline District, Santa Catarina State

    International Nuclear Information System (INIS)

    A 1:100.000 geological map shows the main outcrops, covering about 50 Km2, of the leucocratic alkaline rocks, ultra basic alkaline rocks, carbonatites and volcanic breccias which intruded the Gondwanic sedimentary rocks within a short time interval and characterize the Alkaline District of Lages. Chemical analyses of 33 whole-rock samples confirm the petrographic classification, but the agpaitic indexes, mostly below 1.0, do not reflect the mineralogical variations of the leucocratic alkaline rocks adequately. Partial REE analyses indicate that the light as well as the heavy rare earth contents decrease from the basic to the more evolved rocks, the La/Y ratio remaining approximately constant. Eleven new K/Ar ages from porphyritic nepheline syenites porphyritic phonolites, ultra basic alkaline rocks and pipe-breccias, together with six already available ages, show a major concentration in the range 65 to 75 Ma, with a mode at ca. 70 Ma. But one Rb/Sr whole-rock reference isochron diagram gives an age of 82+-6 Ma for the agpaitic phonolites of the Serra Chapada, which are considered younger than the miaskitic porphyriric nepheline syenites. The 87 Sr/86 Sr ratios of 0.705-0.706 are compatible with a sub continental mantelic origin, devoid of crustal contamination. A petrogenetic model based on subtraction diagrams and taking into consideration the geologic, petrographic, mineralogic and petrochemical characteristics of the alkaline rocks of Lages consists of limited partial melting with CO2, contribution of the previously metasomatized upper mantle, in a region submitted to decompression. (author)

  19. Uruguay geology contributions no. 4

    International Nuclear Information System (INIS)

    Sedimentary facies: the metasiltites and mela sandstones develop granoblastic textures. The present lepidoblastic textures in flexured bands of seri cite and/or chlorite, a fine qranoblastic matrix made by quartz-feldespaths. The carbonates develop mosaic textures with big crystals of calcites and dolomite, generally elongated following metamorphic foliation (seri cite/chlorite). The quartzites develop qranoblastic textures, with few minerals. Volcanics facies: the basic volcanics presents doleritic intersect al textural, that exist saussuritized plagioclase and albitic diabasa with diopside-augite beaches. Usually the pyroxenes develop poiquilitic textural. Present amphiboles of the acti note series and frequently sphene. Others basic rocks are microlitio porfiric, in intersect al or fluidal matrix, with albite microliters in epi dote-chlorite-acti note criploerislalline ground.The stability relationships of the diferents types of basic metavulcanites show low metamorphic facies, with temperatures under 530-550 grades C, being the most Irequenl association: albite+actinote+chlorite+epidote+opaques- opaques.The clastic faciest are integrated by monogenic breccia with elements of varied vulcanites and porfiric rnicrolitic texture. The matrix is made of line quartz and epidote aggregate. The basic volcanism present hyalo-porfiric textures with saussuritized plagiodase pheno crystals, and quartz in a micro lo criptocrystalline ground. Were also defined rocks with porfiric texture in a piromeritic ground as well as rocks with vacuolar microlitic texture.The clastic facies are made by breccias with sharp elements, with rare cement, integrated by pyroclastic products, The volcanics rocks present retrometamorphism of the phenocrystals and devitrification. The plagioclase are traslormated in fine aggregates of albite epidote. The regional metamorphism minerals are represented by the para genesis: quartz+albite+chlorite+epidote+(seri cite-actinole), subfacies quartz albite

  20. Internal architecture of the proto-Kern Canyon Fault at Engineer's Point, Lake Isabella Dam site, Kern County, California

    Science.gov (United States)

    Martindale, Z. S.; Andrews, G. D.; Brown, S. R.; Krugh, W. C.

    2014-12-01

    The core of the Cretaceous (?) proto-Kern Canyon Fault (KCF) is exposed continuously for 1.25 km along Engineer's Point at Lake Isabella, Kern County, California. The proto-KCF is notable for (1) its long and complex history within, and perhaps preceding the Sierra Nevada batholith, and (2) hosting the Quaternary Kern Canyon Fault, an active fault that threatens the integrity of the Lake Isabella auxiliary dam and surrounding communities. We are investigating the internal architecture of the proto-KCF to explore its control on the likely behavior of the modern KCF. The proto-KCF is developed in the Alta Sierra biotite-granodiorite pluton. A traverse across Engineer's Point, perpendicular to the proto-KCF trace, reveals gradational increases in fracture density, fracture length, bulk alteration, and decreases in fracture spacing and grain size toward the fault core. Mapping of the fault core reveals two prominent and laterally extensive zones: (1) continuous foliated blastomylonitic granodiorite with steeply-dipping, anastomosing shear bands and minor mylonite planes, and (2) foliated orange and green fault breccia with intergranular gouge, strong C/S fabric, and a central gouge plane. The fault breccia zone is intruded by a lensoidal, post-deformation dacite dike, probably ca. 105 - 102 Ma (Nadin & Saleeby, 2008) and is weakly overprinted by a set of cross-cutting spaced, short, brittle fractures, often coated in calcite, which we infer to be genetically related to the modern KCF. We present our structural and lithological data that will be supported by mineralogical and geochemical analyses. E. Nadin & J. Saleeby (2008) Disruption of regional primary structure of the Sierra Nevada batholith by the Kern Canyon fault system, California: Geological Society of America Special Paper 438, p. 429-454.

  1. Carbonate sedimentation in an extensional active margin: Cretaceous history of the Haymana region, Pontides

    Science.gov (United States)

    Okay, Aral I.; Altiner, Demir

    2016-03-01

    The Haymana region in Central Anatolia is located in the southern part of the Pontides close to the İzmir-Ankara suture. During the Cretaceous, the region formed part of the south-facing active margin of the Eurasia. The area preserves a nearly complete record of the Cretaceous system. Shallow marine carbonates of earliest Cretaceous age are overlain by a 700-m-thick Cretaceous sequence, dominated by deep marine limestones. Three unconformity-bounded pelagic carbonate sequences of Berriasian, Albian-Cenomanian and Turonian-Santonian ages are recognized: Each depositional sequence is preceded by a period of tilting and submarine erosion during the Berriasian, early Albian and late Cenomanian, which corresponds to phases of local extension in the active continental margin. Carbonate breccias mark the base of the sequences and each carbonate sequence steps down on older units. The deep marine carbonate deposition ended in the late Santonian followed by tilting, erosion and folding during the Campanian. Deposition of thick siliciclastic turbidites started in the late Campanian and continued into the Tertiary. Unlike most forearc basins, the Haymana region was a site of deep marine carbonate deposition until the Campanian. This was because the Pontide arc was extensional and the volcanic detritus was trapped in the intra-arc basins and did not reach the forearc or the trench. The extensional nature of the arc is also shown by the opening of the Black Sea as a backarc basin in the Turonian-Santonian. The carbonate sedimentation in an active margin is characterized by synsedimentary vertical displacements, which results in submarine erosion, carbonate breccias and in the lateral discontinuity of the sequences, and differs from blanket like carbonate deposition in the passive margins.

  2. Albian - Cenomanian resedimented limestone in the Lower flyschoid Formation of the Mt. Mrzli Vrh Area (Tolmin region, NW Slovenia

    Directory of Open Access Journals (Sweden)

    Boštjan Rožič

    2005-12-01

    Full Text Available The Lower flyschoid formation of the Slovenian Basin is characterized by marl, shale and subordinate chert, interbedded with micritic limestone and resedimented carbonates.In the upper part of the formation marly and micritic limestones commonly prevail. The maximum range of the formation is Albian to Turonian. Contact with underlying successions is always erosional and the formation usually overlies upper Tithonian to NeocomianBiancone limestone. In the Mt. Mrzli vrh area, the formation is composed of upper Albian to lower Cenomanian resedimented limestone and upper Cenomanian to Turonian shale and marl, marly limestone and cherts. It directly overlies Lower Jurassic basinal successionor Upper Triassic platform dolomite. In this study resedimented carbonates of the formation were analyzed. A two km2 area was mapped and an 80m thick Mt. Grmuč section was studied in detail. This section consists of micritic limestone and abundant breccia andcalcarenite. Whereas the calcarenite is predominantly composed of platform-derived material, the breccia consists of slope-to-basin intraclasts and various extraclasts of older platform and basin deposits. The analyzed facies association indicates a lower slopedepositional environment. A correlation with other successions of the Lower flyschoid formation reveals that resedimented carbonates are the thickest and most abundant in the Tolmin region, that paleogeographically corresponds to the western part of the SlovenianBasin. Intense Albian – Cenomanian tectonic activity is inferable regionally, from platform as well as basinal successions, and is thought to have been the major factor causing andcontrolling the carbonate gravity-flows sedimentation in the Slovenian Basin. The Mt. Mrzli vrh area is important for paleotopographic reconstruction because it links thecentral Slovenian Basin with the margin of the Dinaric Carbonate Platform. The observed lateral facies distribution, the composition of lithoclasts

  3. Sm-Nd and Rb-Sr Isotopic Studies of Meteorite Kalahari 009: An Old VLT Mare Basalt

    Science.gov (United States)

    Shih, C.-Y.; Nyquist, L. E.; Reese, Y.; Bischoff, A.

    2008-01-01

    Lunar meteorite Kalahari 009 is a fragmental basaltic breccia contain ing various very-low-Ti (VLT) mare basalt clasts embedded in a fine-g rained matrix of similar composition. This meteorite and lunar meteorite Kalahari 008, an anorthositic breccia, were suggested to be paired mainly due to the presence of similar fayalitic olivines in fragment s found in both meteorites. Thus, Kalahari 009 probably represents a VLT basalt that came from a locality near a mare-highland boundary r egion of the Moon, as compared to the typical VLT mare basalt samples collected at Mare Crisium during the Luna-24 mission. The concordant Sm-Nd and Ar-Ar ages of such a VLT basalt (24170) suggest that the extrusion of VLT basalts at Mare Crisium occurred 3.30 +/- 0.05 Ga ag o. Previous age results for Kalahari 009 range from approximately 4.2 Ga by its Lu-Hf isochron age to 1.70?0.04 Ga of its Ar-Ar plateau ag e. However, recent in-situ U-Pb dating of phosphates in Kalahari 009 defined an old crystallization age of 4.35+/- 0.15 Ga. The authors su ggested that Kalahari 009 represents a cryptomaria basalt. In this r eport, we present Sm-Nd and Rb-Sr isotopic results for Kalahari 009, discuss the relationship of its age and isotopic characteristics to t hose of other L-24 VLT mare basalts and other probable cryptomaria ba salts represented by Apollo 14 aluminous mare basalts, and discuss it s petrogenesis.

  4. Uranium geology of the eastern Baker Lake basin, District of Keewatin, Northwest Territories

    International Nuclear Information System (INIS)

    Proterozoic sequences associated with major unconformities are potential uranium metallogenic provinces. Late Aphebian to Paleohelikian Dubawnt Group contintental clastic sedimentary and subaerial alkaline volcanic rocks and underlying Archean gneisses, District of Keewatin, Northwest Territories, represent one such uraniferous metallogenic province. Three types of uranium mineralization are present in the eastern Baker Lake basin, which extends from Christopher Island at the eastern end of Baker Lake southwestwards to the western limit of Thirty Mile Lake. The three uranium associations are: 1) fracture controlled mineralization in the Dubawnt Group and basement gneisses (U-Cu-Ag-Au-Se or U-Cu-Pb-Mo-Zn), 2)diatreme breccia mineralization in basement gneisses (U-Cu-Zn), and 3) impregnation and microfracture mineralization in altered arkose peripheral to lamprophyre dykes(U-Cu-Ag). Hydrothermal fracture related mineralization is controlled by northwest- and east-northeast-trending fault-fracture zones. Diatreme breccia mineralization results from the channelling of groundwaters through highly permeable brecciated gneiss. Mineralization within the altered Kazan arkose peripheral to alkaline dyke complexes formed by a two stage process. Iron and copper sulphides and silver were deposited within the outer portions of the thermal aureole in response to a temperature and Eh gradient across a convective cell created by the thermal anomaly of the dyke complex. The epigenetic sulphide mineralization subsequently provided the reducing environment for precipitation of uranium from groundwater. All three uranium associations show a close spatial distribution to the basal Dubawnt unconformity. The lithological and structural relationships of the Dubawnt Group rocks, types of mineralization and associated alteration assemblages are strikingly similar to the Beaverlodge district, Saskatchewan. (author)

  5. The Early Mesozoic volcanic arc of western North America in northeastern Mexico

    Science.gov (United States)

    Barboza-Gudiño, José Rafael; Orozco-Esquivel, María Teresa; Gómez-Anguiano, Martín; Zavala-Monsiváis, Aurora

    2008-02-01

    Volcanic successions underlying clastic and carbonate marine rocks of the Oxfordian-Kimmeridgian Zuloaga Group in northeastern Mexico have been attributed to magmatic arcs of Permo-Triassic and Early Jurassic ages. This work provides stratigraphic, petrographic geochronological, and geochemical data to characterize pre-Oxfordian volcanic rocks outcropping in seven localities in northeastern Mexico. Field observations show that the volcanic units overlie Paleozoic metamorphic rocks (Granjeno schist) or Triassic marine strata (Zacatecas Formation) and intrude Triassic redbeds or are partly interbedded with Lower Jurassic redbeds (Huizachal Group). The volcanic rocks include rhyolitic and rhyodacitic domes and dikes, basaltic to andesitic lava flows and breccias, and andesitic to rhyolitic pyroclastic rocks, including breccias, lapilli, and ashflow tuffs that range from welded to unwelded. Lower-Middle Jurassic ages (U/Pb in zircon) have been reported from only two studied localities (Huizachal Valley, Sierra de Catorce), and other reported ages (Ar/Ar and K-Ar in whole-rock or feldspar) are often reset. This work reports a new U/Pb age in zircon that confirms a Lower Jurassic (193 Ma) age for volcanic rocks exposed in the Aramberri area. The major and trace element contents of samples from the seven localities are typical of calc-alkaline, subduction-related rocks. The new geochronological and geochemical data, coupled with the lithological features and stratigraphic positions, indicate volcanic rocks are part of a continental arc, similar to that represented by the Lower-Middle Jurassic Nazas Formation of Durango and northern Zacatecas. On that basis, the studied volcanic sequences are assigned to the Early Jurassic volcanic arc of western North America.

  6. Actinide and rare earth element characteristics of deep fracture zones in the Lac du Bonnet granitic batholith, Manitoba, Canada

    International Nuclear Information System (INIS)

    The history of major, trace, and actinide element mobility and fluid infiltration has been studied in two deep fractures (>1 km) in the Lac du Bonnet batholith as part of the Canadian Nuclear Fuel Waste Management Program. Core samples collected from two fracture zones, FR1 and FR2 (∼1,175 m deep), containing saline groundwater (TDS = 50 g/L) were investigated mineralogically, chemically, and isotopically (238U-series, O and H). Several sequentially overprinting alteration states were identified from early high-temperature to later low-temperature hydrothermal alteration. K-feldspar, illite, chlorite, and later kaolinite formed during these stages. Subsequent infiltration of oxidizing fluids produced alteration of the chlorite to hydrous iron oxides. Fracture zone FR1 contains predominantly hematite coating; fracture zone FR2 is characterized by the formation of a breccia and by an intense alteration of the granite in contact with this breccia to illitic clay. Alteration occurred during infiltration either of formation brines or of isotopically evolved meteoric water where δ18O = 8 to 12 per-thousand and δD = -65 to -20 per-thousand, at calculated temperatures between ∼250 and ≤25 degrees C. Pronounced disequilibria of 234U/238U (230Th/234U (∼0.7), and 226Ra/230Th (∼0.9) exist in the illitic clay, indicating loss of 234U, 230Th, and 226Ra to the groundwater within the last 1.5 Ma. In contrast, an excess of 234U, 230Th, and 226Ra was measured in the brecciated samples. The disequilibria are consistent with a model involving loss of 234U, 230Th, and 226Ra to groundwater by α-recoil from U deposited on the illitic clay surfaces. These radionuclides were deposited subsequently in the nearby brecciated zone. 51 refs., 11 figs., 8 tabs

  7. ASTEROIDAL GRANITE-LIKE MAGMATISM 4.53 GYR AGO

    International Nuclear Information System (INIS)

    Constraining the timescales for the evolution of planetary bodies in our solar system is essential for a complete understanding of planet-forming processes. However, frequent collisions between planetesimals in the early solar system obscured and destroyed much of the primitive features of the old, first-generation planetary bodies. The presence of differentiated, achondritic clasts in brecciated chondrites and of chondritic fragments in achondritic breccias clearly witness multiple processes such as metamorphism, magmatism, fragmentation, mixing, and reaccretion. Here, we report the results of ion microprobe Pb-Pb dating of a granite-like fragment found in a meteorite, the LL3-6 ordinary chondrite regolith breccia Adzhi-Bogdo. Eight spot analyses of two phosphate grains and other co-genetic phases of the granitoid give a Pb-Pb isochron age of 4.48 ± 0.12 billion years (95% confidence) and a model age of 4.53 ± 0.03 billion years (1σ), respectively. These ages represent the crystallization age of a parental granite-like magma that is significantly older than those of terrestrial (4.00-4.40 Gyr) and lunar granites (3.88-4.32 Gyr) indicating that the clast in Adzhi-Bogdo is the oldest known granitoid in the solar system. This is the first evidence that granite-like formation is not only a common process on Earth, but also occurred on primitive asteroids in the early solar system 4.53 Gyr ago. Thus, the discovery of granite magmatism recorded in a brecciated meteorite provides an innovative idea within the framework of scenarios for the formation and evolution of planetary bodies and possibly exoplanetary bodies.

  8. Alteration and petrology of Intrusive Rocks associated with Gold Mineralization at Kuh-E-Zar Gold Deposit, Torbat-e-Heydaryeh

    Directory of Open Access Journals (Sweden)

    Alireza Mazloumi Bajestani

    2009-09-01

    Full Text Available Kuh- e -Zar gold deposit located 35 km west of Torbat-e-Heydaryeh, (Khorassan e- Razavi province, East of Iran. This deposit is a specularite-rich Iron oxide type (IOCG. This mine is situated within Khaf-Bardascan volcanic plutonic belt. Based on recent exploration along this belt, several IOCG type system plus Kuh-e-Zar deposit are discovered. In the study area, several type of tuff and lava having acid to intermediate composition are identified (upper Eocene. Oligo-Miocene granite, granodiorite, synogranite and monzonite intruded upper Eocene andesite-dacite-rhyolite. Intrusive rocks are meta-aluminous, medium to high-K series I-type. Based on spider diagram, intrusive rocks show enrichment in LILE = K, Th, Rb and depletion in HFSE = Nb, Sr, Ti. Based geochemistry of igneous rock, they formed in continental margin subduction zone. Propylitic (chlorite alteration is dominated and covers large area. Silicification is restricted only to mineralized zones. Argillic and albitization is found in certain location and cover small areas. The style of mineralization was controlled by the type and geometry of fault zones. Mineralization is found as vein, stockwork and breccias. Hypogene mineral Paragenesis include: specularite-quartz-gold-chlorite ± chalcopyrite ± pyrite ± galena ± barite. Secondary minerals formed due to oxidation are: goethite, limonite, lepidocrucite, Malachite, Azurite, Covelite, Cerucite, hydrocerucite, Pyrolusite and Smitsonite. In a few localities, chalcopyrite and minor pyrite and galena are found. Based on SEM analysis gold is present as electrum. Mineralization appeared in different type such as vein, stockwork and Hydrothermal breccia in strike sleep fault zone which are hidden inside volcano plutonic rocks. The average gold grade is between 3.02 ppm and ore reserve is estimated more than 3 million tons (cut off grade = 0.7 ppm.

  9. Geology, alteration, mineralization, petrogenesis, geochronology, geochemistry and airborne geophysics of Kuh Shah prospecting area, SW Birjand

    Directory of Open Access Journals (Sweden)

    Maryam Abdi

    2012-04-01

    Full Text Available The Kuh Shah prospecting area is located in Tertiary volcano-plutonic belt of the Lut Block. More than seventeen subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, were identified in the study area. The intrusions are related to hydrothermal alteration zones and contain argillic, propylitic, advanced argillic, silicified, quartz-sericite-pyrite, gossan and hydrothermal breccia which overprinted to each other and are accompanied by weathering which made it complicated to distinguish zoning. Mineralization is observed as sulfide (pyrite and rare chalcopyrite, disseminated Fe-oxides and quartz-Fe-oxide stockwork veinlets. Intrusive rocks are metaluminous, calc-alkaline with shoshonitic affinity with high values of magnetic susceptibility. The Kuh Shah intrusive rocks are classified as magnetite-series of oxidant I-type granitoids. Based on zircon U–Pb age dating, the age of these granitoid rocks is 39.7± 0.7 Ma (Middle Eocene. The radioisotope data (initial 87Sr/86Sr and 143Nd/144Nd ratios as well as εNd and geochemical data suggest that the Kuh Shah granitoid rocks formed from depleted mantle in a subduction-related magmatic arc setting. Geochemical anomalies of elements such as Cu, Au, Fe, Pb, Zn, As, Sb, Mo, Bi, Hg and also Mn, Ba, Te and Se, correlated with quartz-sericite-pyrite, gossan-stockwork-hydrothermal breccias, irregular silicified bodies and advanced argillic hydrothermal alteration zones. Geophysical anomalies correlated with hydrothermal alteration and mineralization zones. The interpretation of the results represents complex patterns of sub-circular to ellipsoid shape with north-east to south-west direction. These evidences are similar to the other for known Cu-Au porphyry and Au-epithermal systems in Iran and worldwide.

  10. Ultrabasic-basic intrusive vizcaino layered complex and vizcaino ophiolite (southern baja california, mexico)

    International Nuclear Information System (INIS)

    Two ultrabasic-basic rocks-bearing units occur in the Vizcaino Peninsula of Southern Baja California (Mexico): the Vizcaino Layered Complex (VLC) and the San Hipolito Zone (SHZ). The VLC consists of two sequences: the lower Puerto Nuevo Sequence (serpentinite breccia, harzburgite, dunite, cyclic units), and the upper La Pintada Sequence (cyclic units, gabbros, diorites). The SHZ consists of serpentinite, actinote schists. microgabbros, spilitic pillow lavas, ophicalcites, radiolarites, tuffs, greywackes, interbedded limestone and dolomite, siliceous sandstones, and volcano sedimentary strata). The VLC is an autochtonous complex generated by a magma under plating, which is intrusive into the San Pablo Metamorphic Complex (SPMC) (amphibole-biotite gneiss with lenses of granite, migmatitic amphibolitic gneiss, orthoamphibolites). Originally, together with its metamorphic roof, the SPMC, it constituted a continental magmatic arc .The SHZ, a former Late Triassic marginal sea, is an allochthonous Carnian (?)-Norian ophiolitic unit, emplaced as a nappe upon the VLC during the Liassic. During the Late Triassic (starting at ±220 Ma) this zone underwent a long lived extensional event, during which plagiogranite dykes and dolerite/albitite dykes were emplaced into it, whereas the San Hipolito Basin opened behind it. Then, different units of the VLC were exhumed and exposed by low angle normal listric faults. It seems that the upper part of the VLC, La Pintada Sequence and the SPMC were then displaced to their present position of San Pablo-La Pintada. During the Liassic compressional phase the plagiogranite dykes were boudinaged, and slices of the SHZ Nappe came to rest upon every one of the units of the Puerto Nuevo Sequence, including the serpentinite breccia (which gave way to the erroneous notion of the so-called Puerto Nuevo melange of previous literature).

  11. Heterotrophic microbial colonization of the interior of impact-shocked rocks from Haughton impact structure, Devon Island, Nunavut, Canadian High Arctic

    Science.gov (United States)

    Fike, David A.; Cockell, Charles; Pearce, David; Lee, Pascal

    2002-10-01

    The polar desert is one of the most extreme environments on Earth. Endolithic organisms can escape or mitigate the hazards of the polar desert by using the resources available in the interior of rocks. We examined endolithic communities within crystalline rocks that have undergone shock metamorphism as a result of an asteroid or comet impact. Specifically, we present a characterization of the heterotrophic endolithic community and its environment in the interior of impact-shocked gneisses and their host polymict breccia from the Haughton impact structure on Devon Island, Nunavut, Canadian High Arctic. Microbiological colonization of impact-shocked rocks is facilitated by impact-induced fissures and cavities, which occur throughout the samples, the walls of which are lined with high abundances of biologically important elements owing to the partial volatilization of minerals within the rock during the impact. 27 heterotrophic bacteria were isolated from these shocked rocks and were identified by 16S rDNA sequencing. The isolates from the shocked gneiss and the host breccia are similar to each other, and to other heterotrophic communities isolated from polar environments, suggesting that the interiors of the rocks are colonized by microorganisms from the surrounding country rocks and soils. Inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis were used to identify the chemical composition of the shocked materials and to document the in situ growth of microbes in their interiors. The identification of these heterotrophic communities within impact-shocked crystalline rocks extends our knowledge of the habitable biosphere on Earth. The colonization of the interiors of these samples has astrobiological applications both for considering terrestrial, microbiological contamination of meteorites from the Antarctic ice sheet and for investigating possible habitats for microbial

  12. Hydrothermal zeolitisation controlled by host-rock lithofacies in the Periadriatic (Oligocene) Smrekovec submarine composite stratovolcano, Slovenia

    Science.gov (United States)

    Kralj, Polona

    2016-05-01

    Hydrothermal zeolites (laumontite, yugawaralite, analcime, heulandite, clinoptilolite), prehnite and pumpellyite have been recognised in a succession of volcanic, autoclastic, pyroclastic, resedimented volcaniclastic and mixed siliciclastic-volcaniclastic deposits. In cone-building lithofacies association attaining 310 m, the alteration minerals commonly change within a single normally graded depositional unit or alternate in the section on a dm- to m-scale, according to the host-rock lithofacies. Fine-grained deposits rich in juvenile glassy pyroclasts are altered to heulandite and clinoptilolite or analcime, and laumontite widely occurs in coarse-grained host-rocks (lapilli tuff, hyaloclastite breccia, volcaniclastic breccia, hyaloclastites) and fracture systems. In near-vent lithofacies association attaining 420 m, prehnite-laumontite, laumontite-analcime, and laumontite-heulandite-clinoptilolite zones developed as a result of superimposed thermal regime generated by the emplacement of an over 200 m thick sill. The recognised dependence of alteration on porosity, permeability and fracturing of the host-rock is closely related to hydrological conditions in the stratovolcano-hosted hydrothermal system with convective-advective flow regime. After separation of steam and gases from convecting hydrothermal fluids, denser liquids outflowed intermittently, preferentially through steeply inclined (20-30°) high-permeability layers in the stratovolcano edifice. In low-permeability layers the flow was slow and thermal conditions were mainly attained by conduction. Zeolites developed only in coarse- and fine-grained vitroclastic tuffs, presumably by the dissolution of volcanic glass. The interstratified siliciclastic siltstones, tuffites and resedimented deposits with low content of glassy particles are devoid of zeolites and indicate compositional constraint on zeolitisation. Lava flows, cooling in a submarine environment and undergoing disintegration and mingling with

  13. Stratigraphy and structure of volcanic rocks in drill hole USW-G1, Yucca Mountain, Nye County, Nevada

    International Nuclear Information System (INIS)

    Detailed subsurface studies in connection with the Nevada Nuclear Waste Storage Investigations program are being conducted to investigate the stratigraphic and structural features of volcanic rocks underlying Yucca Mountain, a volcanic highland situated along the western boundary of the Nevada Test Site in southern Nevada. As part of this continuing effort, drill hole USW-G1 was cored from 292 ft to a depth of 6000 ft from March to August 1980. The stratigraphic section is composed of thick sequences of ash-flow tuff and volcanic breccia interbedded with subordinate amounts of fine- to coarse-grained volcaniclastic rocks. All rocks are of Tertiary age and vary in composition from rhyolite to dacite. The 3005-ft level in the drill hole represents a significant demarcation between unaltered and altered volcanic rocks. For the most part, tuff units above 3005 ft appear devitrified and show little secondary alteration except within tuffaceous beds of Calico Hills, where the rock contains 60 to 80% zeolites. Below 3005 ft, most rocks show intermittent to pervasive alteration to clay minerals and zeolites. Examination of core for structural features revealed the presence of 61 shear fractures, 528 joints, and 4 conspicuous fault zones. Shear fractures mainly occurred in the Topopah Spring Member of the Paintbrush Tuff, flow breccia, and near fault zones. Nearly 88% of shear and joint surfaces show evidence of coatings. Approximately 40% of the fractures were categorized as completely healed. Rock quality characteristics as defined by the core index indicate that greater amounts of broken and lost core are commonly associated with (1) the densely welded zone of the Topopah Spring, (2) highly silicified zones, and (3) fault zones

  14. The distribution of megablocks in the Ries crater, Germany: Remote sensing, field investigation, and statistical analyses

    Science.gov (United States)

    Sturm, Sebastian; Kenkmann, Thomas; Willmes, Malte; PöSges, Gisela; Hiesinger, Harald

    2015-01-01

    The Ries crater is a well-preserved, complex impact crater that has been extensively used in the study of impact crater formation processes across the solar system. However, its geologic structure, especially the megablock zone, still poses questions regarding crater formation mechanics. The megablock zone, located between the inner crystalline ring and outer, morphologic crater rim, consists of allochthonous crystalline and sedimentary blocks, Bunte Breccia deposits, patches of suevite, and parautochthonous sedimentary blocks that slumped into the crater during crater modification. Our remote sensing detection method in combination with a shallow drilling campaign and geoelectric measurements at two selected megablocks proved successful in finding new megablock structures (>25 m mean diameter) within the upper approximately 1.5 m of the subsurface in the megablock zone. We analyzed 1777 megablocks of the megablock zone, 81 of which are new discoveries. In our statistical analysis, we also included 2318 ejecta blocks >25 m beyond the crater rim. Parautochthonous megablocks show an increase in total area and size toward the final crater rim. The sizes of allochthonous megablocks generally decrease with increasing radial range, but inside the megablock zone, the coverage with postimpact sediments obscures this trend. The size-frequency distribution of all megablocks obeys a power-law distribution with an exponent between approximately -1.7 and -2.3. We estimated a total volume of 95 km3 of Bunte Breccia and 47 km3 of megablocks. Ejecta volume calculations and a palinspastic restoration of the extension within the megablock zone indicate that the transient cavity diameter was probably 14-15 km.

  15. Feldspathic Clasts in Yamato 86032: Remnants of the Lunar Crust with Implications for its Formation and Impact History

    Science.gov (United States)

    Nyquist, L.; Bogard, D.; Yamaguchi, A.; Shih, C.-Y.; Ebihara, M.; Reese, Y.; Garrison, D.; Takeda, H.

    2006-01-01

    Yamato (Y)-86032 is a relatively large, feldspathic lunar highlands meteorite composed of a variety of highland lithologies. Low bulk contents of Th and Fe indicated that it came from a region of the moon far distant from the Procellarum KREEP Terrain (PKT) and the Apollo landing sites, perhaps from the farside. A large (5.2 x 3.6 cm) slab was cut from Y-86032 . We report results from coordinated textural, mineralogical-petrological, chemical, and isotopic studies of lithologies identified in the slab, emphasizing the results of Ar-39/Ar-40, Rb-Sr, and Sm-Nd chronological studies as well as Sm-isotopic studies. These studies characterize the history of Y-86032 and its precursors in the farside mega-regolith, leading to inferences about the formation and evolution of the lunar crust. Textural studies establish that the Y-86032 breccia is composed of a variety of highland components including feldspathic breccias, and other components, such as possible VLT mare basalts. Impact melt veins smoothly abut the other lithologies. Thus, Y-86032 experienced at least two impact events. These impacts occurred on a predominantly feldspathic protolith, which formed 4.43+/-0.03 Ga ago as determined from a Sm-Nd isochron for mineral clasts separated from the two dominant lithologies. Initial Nd-143/Nd-144 in the protolith at that time was -0.64+/-0.13 epsilon-units below Nd-143/Nd-144 in reservoirs having chondritic Sm/Nd ratios, consistent with prior fractionation of mafic cumulates from the LMO. Although the mineral chemistry of these clasts differs in detail from that of minerals in Apollo 16 Ferroan Anorthosites (FANs), the Rb-Sr studies establish that the initial Sr-87/Sr-86 in them was the same as in the FANs.

  16. Evaporite-karst problems and studies in the USA

    Science.gov (United States)

    Johnson, K.S.

    2008-01-01

    Evaporites, including rock salt (halite) and gypsum (or anhydrite), are the most soluble among common rocks; they dissolve readily to form the same types of karst features that commonly are found in limestones and dolomites. Evaporites are present in 32 of the 48 contiguous states in USA, and they underlie about 40% of the land area. Typical evaporite-karst features observed in outcrops include sinkholes, caves, disappearing streams, and springs, whereas other evidence of active evaporite karst includes surface-collapse structures and saline springs or saline plumes that result from salt dissolution. Many evaporites also contain evidence of paleokarst, such as dissolution breccias, breccia pipes, slumped beds, and collapse structures. All these natural karst phenomena can be sources of engineering or environmental problems. Dangerous sinkholes and caves can form rapidly in evaporite rocks, or pre-existing karst features can be reactivated and open up (collapse) under certain hydrologic conditions or when the land is put to new uses. Many karst features also propagate upward through overlying surficial deposits. Human activities also have caused development of evaporite karst, primarily in salt deposits. Boreholes (petroleum tests or solution-mining operations) or underground mines may enable unsaturated water to flow through or against salt deposits, either intentionally or accidentally, thus allowing development of small to large dissolution cavities. If the dissolution cavity is large enough and shallow enough, successive roof failures can cause land subsidence and/or catastrophic collapse. Evaporite karst, natural and human-induced, is far more prevalent than is commonly believed. ?? 2007 Springer-Verlag.

  17. Carbonatite associated with ultramafic diatremes in the Avon Volcanic District, Missouri, USA: Field, petrographic, and geochemical constraints

    Science.gov (United States)

    Shavers, Ethan J.; Ghulam, Abduwasit; Encarnacion, John; Bridges, David L.; Luetkemeyer, P. Benjamin

    2016-04-01

    Here we report field, petrographic, and geochemical analyses of the southeast Missouri Avon Volcanic District intrusive rocks and present the first combined textural and geochemical evidence for the presence of a primary magmatic carbonatite phase among ultramafic dikes, pipes, and diatremes of olivine melilitite, alnöite, and calciocarbonatite. The δ13CVPDB values measured for primary calciocarbonatite as well as carbonates in olivine melilitite and alnöite rocks range from - 3.8‰ to - 8.2‰, which are within the typical range of mantle values and are distinct from values of the carbonate country rocks, 0.0‰ to - 1.3‰. The carbonate oxygen isotope compositions for the intrusive lithologies are in the range of 21.5‰ to 26.2‰ (VSMOW), consistent with post-emplacement low temperature hydrothermal alteration or kinetic fractionation effects associated with decompression and devolatilization. Metasomatized country rock and breccia-contaminated igneous lithologies have carbonate δ13CVPDB values gradational between primary carbonatite values and country rock values. Unaltered sedimentary dolomite breccia and mafic spheroids entrained by calciocarbonatite and the lack of microstratigraphic crystal growth typical of carbonate replacement, also exclude the possibility of hydrothermal replacement as the cause of the magmatic-textured carbonates. Rare earth element (REE) patterns for the alnöite, olivine melilitite, and carbonatite are similar to each other with strong light REE enrichment and heavy REE depletion relative to MORB. These patterns are distinct from those of country rock rhyolite and sedimentary carbonate. These data suggest that rocks of the Avon Volcanic District represent a single ultramafic-carbonatite intrusive complex possibly derived from a single mantle source.

  18. The age, geology, and geochemistry of the Tapuaenuku Igneous Complex, Marlborough, New Zealand

    International Nuclear Information System (INIS)

    The Tapuaenuku Igneous Complex (TIC) is a mid-Cretaceous layered intrusion and dike swarm cropping out at the axis of the Inland Kaikoura Ranges, South Island, New Zealand. The TIC is part of an extensive, but poorly preserved, igneous province that formed during pr after cessation of subduction along the margin of Gondwana c. 100 Ma ago. The TIC is a complex, multiphase intrusion that is subdivided into eight unites (in order of relative emplacement): (1) radial dike swarm - basanite, trachybasalt, and shoshonite/latite dikes; (2) Layered Series (LS) - basin-shaped mafic cumulate rocks; (3) Staircase Intrusives - noncumulate gabbro and monzogabbro enclosed by a discontinuous sheet of cumulate gabbro; (4) Lower Hodder Gabbro and minor gabbroic intrusives - small sticks of noncumulate gabbro, mozogabbro, and monzonite; (5) Red Hills Breccia Pipe - heterolithic breccia emplaced in a pipe or diatreme; (6) Hodder Intrusives - a monzonite and sodalite syenite laccolith intruding the LS; (7)monzonite, orthoclase syenite and quartz syenite sills and dikes, and: (8) highly alkaline lamprophyre, phonotephrite, tephriphonolite, and phonolite dikes. The plethora of rock types in the TIC were produced by fractionation of different mineral assemblages from a trachybasalt or basanite parent magma. The parental magma had incompatible trace element and radiogenic isotopic characteristics similar to HIMU-type ocean island basalt and akin to that of the numerous Cenozoic intraplate volcanic provinces situated in southern New Zealand. However, elevated initial Sr isotope rations of some of the intrusive unites require them to have assimilated Torlesse greywacke country rock. (authors). 52 refs., 9 figs., 8 tabs

  19. Using Technology to Better Characterize the Apollo Sample Suite: A Retroactive PET Analysis and Potential Model for Future Sample Return Missions

    Science.gov (United States)

    Zeigler, R. A.

    2015-01-01

    From 1969-1972 the Apollo missions collected 382 kg of lunar samples from six distinct locations on the Moon. Studies of the Apollo sample suite have shaped our understanding of the formation and early evolution of the Earth-Moon system, and have had important implications for studies of the other terrestrial planets (e.g., through the calibration of the crater counting record) and even the outer planets (e.g., the Nice model of the dynamical evolution of the Solar System). Despite nearly 50 years of detailed research on Apollo samples, scientists are still developing new theories about the origin and evolution of the Moon. Three areas of active research are: (1) the abundance of water (and other volatiles) in the lunar mantle, (2) the timing of the formation of the Moon and the duration of lunar magma ocean crystallization, (3) the formation of evolved lunar lithologies (e.g., granites) and implications for tertiary crustal processes on the Moon. In order to fully understand these (and many other) theories about the Moon, scientists need access to "new" lunar samples, particularly new plutonic samples. Over 100 lunar meteorites have been identified over the past 30 years, and the study of these samples has greatly aided in our understanding of the Moon. However, terrestrial alteration and the lack of geologic context limit what can be learned from the lunar meteorites. Although no "new" large plutonic samples (i.e., hand-samples) remain to be discovered in the Apollo sample collection, there are many large polymict breccias in the Apollo collection containing relatively large (approximately 1 cm or larger) previously identified plutonic clasts, as well as a large number of unclassified lithic clasts. In addition, new, previously unidentified plutonic clasts are potentially discoverable within these breccias. The question becomes how to non-destructively locate and identify new lithic clasts of interest while minimizing the contamination and physical degradation of

  20. Ages and sources of components of Zn-Pb, Cu, precious metal, and platinum group element deposits in the goodsprings district, clark county, Nevada

    Science.gov (United States)

    Vikre, P.; Browne, Q.J.; Fleck, R.; Hofstra, A.; Wooden, J.

    2011-01-01

    The Goodsprings district, Clark County, Nevada, includes zinc-dominant carbonate replacement deposits of probable late Paleozoic age, and lead-dominant carbonate replacement deposits, copper ?? precious metal-platinum group element (PGE) deposits, and gold ?? silver deposits that are spatially associated with Late Triassic porphyritic intrusions. The district encompasses ??500 km2 although the distribution of all deposits has been laterally condensed by late Mesozoic crustal contraction. Zinc, Pb, and Cu production from about 90 deposits was ??160,000 metric tons (t) (Zn > Pb >> Cu), 2.1 million ounces (Moz) Ag, 0.09 Moz Au, and small amounts of PGEs-Co, V, Hg, Sb, Ni, Mo, Mn, Ir, and U-were also recovered. Zinc-dominant carbonate replacement deposits (Zn > Pb; Ag ?? Cu) resemble Mississippi Valley Type (MVT) Zn-Pb deposits in that they occur in karst and fault breccias in Mississippian limestone where the southern margin of the regional late Paleozoic foreland basin adjoins Proterozoic crystalline rocks of the craton. They consist of calcite, dolomite, sphalerite, and galena with variably positive S isotope compositions (??34S values range from 2.5-13%), and highly radiogenic Pb isotope compositions (206Pb/204Pb >19), typical of MVT deposits above crystalline Precambrian basement. These deposits may have formed when southward flow of saline fluids, derived from basinal and older sedimentary rocks, encountered thinner strata and pinch-outs against the craton, forcing fluid mixing and mineral precipitation in karst and fault breccias. Lead-dominant carbonate replacement deposits (Pb > Zn, Ag ?? Cu ?? Au) occur among other deposit types, often near porphyritic intrusions. They generally contain higher concentrations of precious metals than zinc-dominant deposits and relatively abundant iron oxides after pyrite. They share characteristics with copper ?? precious metal- PGE and gold ?? silver deposits including fine-grained quartz replacement of carbonate minerals in

  1. Geoelectrical structure of the central zone of Piton de la Fournaise volcano (Reunion)

    Science.gov (United States)

    Lenat, J.-F.; Fitterman, D.; Jackson, D.B.; Labazuy, P.

    2000-01-01

    A study of the geoelectrical structure of the central part of Piton de la Fournaise volcano (Reunion, Indian Ocean) was made using direct current electrical (DC) and transient electromagnetic soundings (TEM). Piton de la Fournaise is a highly active oceanic basaltic shield and has been active for more than half a million years. Joint interpretation of the DC and TEM data allows us to obtain reliable 1D models of the resistivity distribution. The depth of investigation is of the order of 1.5 km but varies with the resistivity pattern encountered at each sounding. Two-dimensional resistivity cross sections were constructed by interpolation between the soundings of the 1D interpreted models. Conductors with resistivities less than 100 ohm-m are present at depth beneath all of the soundings and are located high in the volcanic edifice at elevations between 2000 and 1200 m. The deepest conductor has a resistivity less than 20 ohm-m for soundings located inside the Enclos and less than 60-100 ohm-m for soundings outside the Enclos. From the resistivity distributions, two zones are distinguished: (a) the central zone of the Enclos; and (b) the outer zone beyond the Enclos. Beneath the highly active summit area, the conductor rises to within a few hundred meters of the surface. This bulge coincides with a 2000-mV self-potential anomaly. Low-resistivity zones are inferred to show the presence of a hydrothermal system where alteration by steam and hot water has lowered the resistivity of the rocks. Farther from the summit, but inside the Enclos the depth to the conductive layers increases to approximately 1 km and is inferred to be a deepening of the hydrothermally altered zone. Outside of the Enclos, the nature of the deep, conductive layers is not established. The observed resistivities suggest the presence of hydrated minerals, which could be found in landslide breccias, in hydrothermally altered zones, or in thick pyroclastic layers. Such formations often create perched

  2. The architecture and frictional properties of faults in shale

    Science.gov (United States)

    De Paola, Nicola; Murray, Rosanne; Stillings, Mark; Imber, Jonathan; Holdsworth, Robert

    2015-04-01

    The geometry of brittle fault zones and associated fracture patterns in shale rocks, as well as their frictional properties at reservoir conditions, are still poorly understood. Nevertheless, these factors may control the very low recovery factors (25% for gas and 5% for oil) obtained during fracking operations. Extensional brittle fault zones (maximum displacement ≤ 3 m) cut exhumed oil mature black shales in the Cleveland Basin (UK). Fault cores up to 50 cm wide accommodated most of the displacement, and are defined by a stair-step geometry, controlled by the reactivation of en-echelon, pre-existing joints in the protolith. Cores typically show a poorly developed damage zone, up to 25 cm wide, and sharp contact with the protolith rocks. Their internal architecture is characterised by four distinct fault rock domains: foliated gouges; breccias; hydraulic breccias; and a slip zone up to 20 mm thick, composed of a fine-grained black gouge. Hydraulic breccias are located within dilational jogs with aperture of up to 20 cm, composed of angular clasts of reworked fault and protolith rock, dispersed within a sparry calcite cement. Velocity-step and slide-hold-slide experiments at sub-seismic slip rates (microns/s) were performed in a rotary shear apparatus under dry, water and brine-saturated conditions, for displacements of up to 46 cm. Both the protolith shale and the slip zone black gouge display shear localization, velocity strengthening behaviour and negative healing rates. Experiments at seismic slip rates (1.3 m/s), performed on the same materials under dry conditions, show that after initial friction values of 0.5-0.55, friction decreases to steady-state values of 0.1-0.15 within the first 10 mm of slip. Contrastingly, water/brine saturated gouge mixtures, exhibit almost instantaneous attainment of very low steady-state sliding friction (0.1). Our field observations show that brittle fracturing and cataclastic flow are the dominant deformation mechanisms in

  3. S saturation history of Nain Plutonic Suite mafic intrusions: origin of the Voisey's Bay Ni-Cu-Co sulfide deposit, Labrador, Canada

    Science.gov (United States)

    Lightfoot, Peter C.; Keays, Reid R.; Evans-Lamswood, Dawn; Wheeler, Robert

    2012-01-01

    The Voisey's Bay deposit is hosted in a 1.34-Ga intrusion composed of troctolite, olivine gabbro, and ferrogabbro. The sulfide mineralization is associated with magmatic breccias that are enveloped by weakly mineralized olivine gabbros and troctolites, and also occurs as veins along structures in adjacent paragneiss. A dyke is connected to the base of the north wall of the Eastern Deeps Intrusion, and the entry point of this dyke into the chamber is the locus of the Eastern Deeps nickel sulfide deposit. A detailed exploration in the area between the Eastern Deeps and the Ovoid has shown that these intrusions and ore deposits are connected by a splayed dyke. The Eastern Deeps Deposit is surrounded by a halo of moderately to weakly mineralized variable-textured troctolite (VTT) that reaches a maximum thickness above the axis of the Eastern Deeps Deposit along the northern wall of the Eastern Deeps Intrusion. The massive sulfides and breccia sulfides are petrologically and chemically different when compared to the disseminated sulfides in the VTT, and there is a marked break in Ni tenor of sulfide between the two. Sulfides hosted in the dyke tend to have low metal tenors ([Ni]100 = 2.5-3.5%), sulfides in Eastern Deeps massive and breccia ores have intermediate Ni tenors ([Ni]100 = 3.5-4%), and disseminated sulfides in overlying rocks have high Ni tenors ([Ni]100 = 4-8%). Four principal processes control the compositions of the Voisey's Bay sulfides. Coarse-grained loop-textured ores consisting of pyrrhotite crystals separated by chalcopyrite and pentlandite exhibit a two orders of magnitude variation in the Pd/Ir ratio which is due to mineralogical variations where pentlandite is enriched in Pd and Ir is dispersed throughout the mineral assemblage. A decrease in Ir and Rh from the margin of the Ovoid toward cubanite-rich parts at the central part of the Ovoid is consistent with fractionation of the sulfide from the margins toward the center of the Ovoid. The Ovoid

  4. Multi-element variations in olivine as geochemical signatures of Ni-Cu sulfide mineralization in mafic magma systems—examples from Voisey's Bay and Pants Lake intrusions, Labrador, Canada

    Science.gov (United States)

    Bulle, Florian; Layne, Graham D.

    2016-01-01

    Olivine from the olivine gabbro to troctolite intrusions at Voisey's Bay and at Pants Lake, Labrador, was analyzed for multiple elements (Ca, Sc, Mg, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, and Zr) with secondary ion mass spectrometry (SIMS). Both intrusions have similar lithologies and petrographic characteristics and are approximately coeval (1.34 and 1.32 Ga, respectively) members of the Mesoproterozoic Nain Plutonic Suite. The Voisey's Bay intrusion hosts a producing economic Ni-Cu sulfide deposit, whereas the Pants Lake intrusion displays evidence of Ni-Cu sulfide mineralization, but, to date, a viable ore deposit has not been discovered. Olivine from both barren and mineralized lithologies was analyzed to assess the potential of the olivine composition for providing a record of silicate melt evolution and sulfide saturation related to formation of a massive sulfide deposit. Two detailed transects were sampled, using five diamond drill holes that laterally approach the basal massive sulfide in the Eastern Deeps portion of the Voisey's Bay intrusion from the barren central part. Olivine displays distinct trace element distributions that vary coherently with host lithology and proximity to sulfide mineralization. In particular, olivine shows an increase in Fe (˜Fo80 to ˜Fo60), Mn (˜2500 to 5000 ppm), and Zn (˜280 to 700 ppm), generally coupled with a decrease in Ni (˜1600 to ˜900 ppm), Co (˜270 to ˜190 ppm), and Cr (˜110 to 45 ppm), from barren troctolite (normal troctolite—NT) and weakly mineralized troctolite (variable-textured troctolite—VTT) towards the heavily mineralized, brecciated basal succession (basal breccia sequence—BBS). The enrichment in Fe-Mn-Zn is most pronounced in samples that laterally approach, but do not directly intersect, the massive sulfide deposit at the base of the intrusion, particularly in samples from the lower variable-textured troctolite and the basal breccia. Olivine from gabbro lithologies within the basal

  5. Tourmaline occurrences within the Penamacor-Monsanto granitic pluton and host-rocks (Central Portugal): genetic implications of crystal-chemical and isotopic features

    Science.gov (United States)

    da Costa, I. Ribeiro; Mourão, C.; Récio, C.; Guimarães, F.; Antunes, I. M.; Ramos, J. Farinha; Barriga, F. J. A. S.; Palmer, M. R.; Milton, J. A.

    2014-04-01

    Tourmalinization associated with peraluminous granitic intrusions in metapelitic host-rocks has been widely recorded in the Iberian Peninsula, given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of Sn-W mineralizations. In the Penamacor-Monsanto granite pluton (Central Eastern Portugal, Central Iberian Zone), tourmaline occurs: (1) as accessory phase in two-mica granitic rocks, muscovite-granites and aplites, (2) in quartz (±mica)-tourmaline rocks (tourmalinites) in several exocontact locations, and (3) as a rare detrital phase in contact zone hornfels and metapelitic host-rocks. Electron microprobe and stable isotope (δ18O, δD, δ11B) data provide clear distinctions between tourmaline populations from these different settings: (a) schorl-oxyschorl tourmalines from granitic rocks have variable foititic component (X□ = 17-57 %) and Mg/(Mg + Fe) ratios (0.19-0.50 in two-mica granitic rocks, and 0.05-0.19 in the more differentiated muscovite-granite and aplites); granitic tourmalines have constant δ18O values (12.1 ± 0.1 ‰), with wider-ranging δD (-78.2 ± 4.7 ‰) and δ11B (-10.7 to -9.0 ‰) values; (b) vein/breccia oxyschorl [Mg/(Mg + Fe) = 0.31-0.44] results from late, B- and Fe-enriched magma-derived fluids and is characterized by δ18O = 12.4 ‰, δD = -29.5 ‰, and δ11B = -9.3 ‰, while replacement tourmalines have more dravitic compositions [Mg/(Mg + Fe) = 0.26-0.64], close to that of detrital tourmaline in the surrounding metapelitic rocks, and yield relatively constant δ18O values (13.1-13.3 ‰), though wider-ranging δD (-58.5 to -36.5 ‰) and δ11B (-10.2 to -8.8 ‰) values; and (c) detrital tourmaline in contact rocks and regional host metasediments is mainly dravite [Mg/(Mg + Fe) = 0.35-0.78] and oxydravite [Mg/(Mg + Fe) = 0.51-0.58], respectively. Boron contents of the granitic rocks are low (Monsanto pluton, either as direct tourmaline precipitation in cavities and fractures crossing the

  6. Fluid evolution in a volcanic-hosted epithermal carbonate-base metal-gold vein system: Alto de la Blenda, Farallón Negro, Argentina

    Science.gov (United States)

    Márquez-Zavalía, M. Florencia; Heinrich, Christoph A.

    2016-03-01

    Alto de la Blenda is a ˜6.6-Ma intermediate-sulphidation epithermal vein system in the Farallón Negro Volcanic Complex, which also hosts the 7.1-Ma porphyry-Cu-Au deposit of Bajo de la Alumbrera. The epithermal vein system is characterised by a large extent and continuity (2 km × 400 m open to depth × 6 m maximum width) and an average gold grade of ˜8 g/t. The vein is best developed within an intrusion of a fine-grained equigranular monzonite, interpreted as the central conduit of a stratovolcano whose extrusive activity ended prior to porphyry-Cu-Au emplacement at Bajo de la Alumbrera, which is in turn cut by minor epithermal veins. The Alto de la Blenda vein consists predominantly of variably Mn-rich carbonates and quartz, with a few percent of pyrite, sphalerite, galena and other sulphide and sulphosalt minerals. Four phases of vein opening, hydrothermal mineralisation and repeated brecciation can be correlated between different vein segments. Stages 2 and 3 contain the greatest fraction of sulphide and gold. They are separated by the emplacement of a polymictic breccia containing clasts of quartz feldspar porphyry as well as basement rocks. Fluid inclusions in quartz related to stages 2 to 4 are liquid rich with 2-4 wt% NaCl(eq). They homogenise between 160 and 300 °C, with very consistent values within each assemblage. Vapour inclusions are practically absent in the epithermal vein. Quartz fragments in the polymictic breccia contain inclusions of intermediate to vapour-like density and similar low salinity (˜3 wt% NaCl(eq)), besides rare brine inclusions containing halite. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of epithermal inclusions indicate high concentrations of K, Fe, As, Sb, Cs, and Pb that significantly vary within and through subsequent vein stages. Careful consideration of detection limits for individual inclusions shows high gold concentrations of ˜0.5 to 3 ppm dissolved in the ore fluid, which

  7. X-Ray Micro-Computed Tomography of Apollo Samples as a Curation Technique Enabling Better Research

    Science.gov (United States)

    Ziegler, R. A.; Almeida, N. V.; Sykes, D.; Smith, C. L.

    2014-01-01

    X-ray micro-computed tomography (micro-CT) is a technique that has been used to research meteorites for some time and many others], and recently it is becoming a more common tool for the curation of meteorites and Apollo samples. Micro-CT is ideally suited to the characterization of astromaterials in the curation process as it can provide textural and compositional information at a small spatial resolution rapidly, nondestructively, and without compromising the cleanliness of the samples (e.g., samples can be scanned sealed in Teflon bags). This data can then inform scientists and curators when making and processing future sample requests for meteorites and Apollo samples. Here we present some preliminary results on micro-CT scans of four Apollo regolith breccias. Methods: Portions of four Apollo samples were used in this study: 14321, 15205, 15405, and 60639. All samples were 8-10 cm in their longest dimension and approximately equant. These samples were micro-CT scanned on the Nikon HMXST 225 System at the Natural History Museum in London. Scans were made at 205-220 kV, 135-160 microamps beam current, with an effective voxel size of 21-44 microns. Results: Initial examination of the data identify a variety of mineral clasts (including sub-voxel FeNi metal grains) and lithic clasts within the regolith breccias. Textural information within some of the lithic clasts was also discernable. Of particular interest was a large basalt clast (approx.1.3 cc) found within sample 60639, which appears to have a sub-ophitic texture. Additionally, internal void space, e.g., fractures and voids, is readily identifiable. Discussion: It is clear from the preliminary data that micro-CT analyses are able to identify important "new" clasts within the Apollo breccias, and better characterize previously described clasts or igneous samples. For example, the 60639 basalt clast was previously believed to be quite small based on its approx.0.5 sq cm exposure on the surface of the main mass

  8. Natural Shock Sintering of Unconsolidated Planetary Materials

    Science.gov (United States)

    Spray, J. G.

    2006-12-01

    On Earth, the transformation of unconsolidated sediment (e.g., sand) to rock (sandstone) occurs via the process of lithification. Lithification typically occurs via burial within the upper crust at less than 150 degrees celsius, at depths of less than 5 km in the presence of liquid H2O. Liquid H2O is often important in the process of lithification because it is the transporting medium for dissolved and suspended ions and mineral species, which eventually precipitate as a cement that binds the unconsolidated grains. Lithification also applies to sedimentary deposits formed by precipitation of minerals from aqueous solutions at surface, or near- surface, conditions (e.g., to generate sulfate or carbonate-rich evaporites). However, for many planetary bodies in our solar system, there are no large sources of liquid H2O to facilitate this type of lithification process. Despite the absence of water on such bodies, the development of consolidated fragmental material is commonplace and it probably dominates the surface materials of Mercury, the Moon, Mars and many asteroids. This material, typically in the form of breccias, is a relatively coherent rock, yet the nature of the "glue" that binds the fragments is not well understood. Clearly, other processes are responsible for the lithification that we take for granted in many of the sedimentary rocks developed on our wet planet. This work explores these processes. For certain planetary bodies unconsolidated material may be bound by ices, such that it possesses rock-like properties in terms in strength and behaviour. In the absence of H2O, unconsolidated semi-molten material can be lithified by welding and compaction (e.g., certain pyroclastic discharges that fall and accumulate to form ignimbrites). This requires the production of hot volcanogenic or impact ejecta. In this work we explore the nature of the binding medium in different types of lunar breccia collected during the Apollo15, 16 and 17 missions, in meteorites of

  9. A high-resolution geochronological and geochemical study on Aegean carbonate deposits, SW Turkey

    Science.gov (United States)

    Ünal-İmer, Ezgi; Uysal, I. Tonguç; Işık, Veysel; Zhao, Jian-Xin; Shulmeister, James

    2014-05-01

    Vein and breccia carbonates precipitated in highly fractured/faulted carbonate bedrock were investigated using high-resolution U-series geochronology, as well as through microstructural and geochemical studies including Sr-O-C isotope and REE element analyses. The study area (Kumlubük and Amos vein systems), located south of the town of Marmaris in SW Turkey, is a part of an active large-scale extensional system. Field studies show that the calcite veins generally occur sub-vertically and strike mostly NW and EW, in agreement with the regional N-S extensional stress regime. Microscopic observations indicate that the calcite veins formed through crack-seal mechanism, typically accompanied/initiated by intensive hydraulic fracturing of wall-rock evidenced by the presence of widespread breccia deposits. Vein textures are dominated by elongated, fibrous, and blocky calcites. Successive fracturing and layering of calcite with sharp contacts are traceable along the fluid inclusion bands occurring parallel to the wall rock boundary. In particular, inclusion trails aligned perpendicular to the wall-rock and calcite crystal elongation give information about the vein dilation (crack opening) vector and growth direction. High-resolution U-series dating (11-272 ka BP) and geochemical compositions of the vein and breccia samples were used to investigate the long-term behaviour as well as the general identity of the CO2-bearing fluids within deformed crust. The seismic nature of calcite veining is further assessed by stable isotopic ratio (δ18O and δ13C) plots against vein depths (distance from the wall-rock). The average δ18OPDBvalue for Kumlubük veins is -3.79o, while Amos has an average value of -4.05o. Similarly, average carbon isotope ratio (-8.30o) of the Kumlubük veins is slightly higher than that is observed for the Amos veins (-9.66o). Isotopic compositions are interpreted to reflect cyclic (or episodic) CO2 variations. This suggests the presence of several fluid

  10. Morphometric, acoustic and lithofacies characterization of mud volcanoes in the Eastern Mediterranean: Toward a new approach and classification to constrain the regional distribution and activity of mud volcanoes?

    Science.gov (United States)

    Flore, Mary; Sébastien, Migeon; Elia, d'Acremont; Alain, Rabaute; Silvia, Ceramicola; Daniel, Praeg; Christian, Blanpied

    2015-04-01

    morphologies and architectures representing end members: conical, with or without a caldera (empty or filled-up with a brine lake), to flat, circular to elongate. Identification of local mud flows on the flanks and/or the base of some mud volcanoes attest of different types of extrusive activity. Cored mud flows revealed the variety of mud breccia characteristics: a new methodology of analysis of the morphologies of mud-breccia clasts, their sizes and distribution is undertaken using X-rays images. This new approach revealed as a first observation that some types of mud volcanoes are more or less homogeneously scattered at the scale of Eastern Mediterranean while other types are more specifically located in a single area. In every studied area, mud volcanoes exhibit or not mud flows at the seafloor or shortly beneath, suggesting that their activity can change over short time periods and distances. Lithofacies evolving from two end-members, mousse-like to breccia, also revealed drastic changes of the type of activity in and between the studied areas.

  11. Evolution of the Bucium Rodu and Frasin magmatic-hydrothermal system, Metaliferi Mountains, Romania

    Science.gov (United States)

    Iatan, Elena Luisa; Berbeleac, Ion; Visan, Madalina; Minut, Adrian; Nadasan, Laurentiu

    2013-04-01

    The Miocene Bucium Rodu and Frasin maar-diatreme structures and related Au-Ag epithermal low sulfidation with passing to mesothermal mineralizations are located in the Bucium-Rosia Montana-Baia de Aries metallogenetic district, within so called the "Golden Quatrilaterum", in the northeastern part of the Metaliferi Mountains. These structures are situated at about 5 km southeast from Rosia Montana, the largest European Au-Ag deposit. The total reserves for Bucium Rodu-Frasin are estimated at 43.3 Mt with average contents of 1.3 g/t Au and 3 g/t Ag. The Miocene geological evolution of Bucium Rodu and Frasin magmatic-hydrothermal system took place in closely relationships with tectonic, magmatic and metallogenetic activity from Bucium-Rosia Montana-Baia de Aries district in general, and adjacent areas, in special. The hydrothermal alteration is pervasive; adularia followed by phyllic, carbonatization and silicification alterations, usually show a close relationship with the mineralizations. Propylitic alteration occurs dominantly towards the depth; argillic alteration shows a local character. The mineralization occurs in veins, breccias, stockworks and disseminations and is hosted within two volcanic structures emplaced into a sequence of Cretaceous sediments in closely genetically relations with the Miocene phreatomagmatic fracturing and brecciation events. Within Rodu maar-diatreme structure the mineralizations follow especially the contact between the diatreme and Cretaceous flysch. The vein sets with low, moderately and near vertical dippings, cover 400x400m with N-S trend. The most important mineralization style is represented by veins, accompanied by hydrothermal breccias and disseminations. The veins spatial distribution relives as "en echelon" tension veins. They carry gold, minor base metal sulphides (pyrite, chalcopyrite, sphalerite, galena, tetrahedrite, arsenopyrite). Gangue is represented by carbonates (calcite, dolomite, ankerite, siderite, rhodochrosite

  12. Cogenetic Rock Fragments from a Lunar Soil: Evidence of a Ferroan Noritic-Anorthosite Pluton on the Moon

    Science.gov (United States)

    Jolliff, B. L.; Haskin, L. A.

    1995-01-01

    The impact that produced North Ray Crater, Apollo 16 landing site, exhumed rocks that include relatively mafic members of the lunar ferroan anorthositic suite. Bulk and mineral compositions indicate that a majority of 2-4 mm lithic fragments from sample 67513, including impact breccias and monomict igneous rocks, are related to a common noritic-anorthosite precursor. Compositions and geochemical trends of these lithic fragments and of related samples collected along the rim of North Ray Crater suggest that these rocks derived from a single igneous body. This body developed as an orthocumulate from a mixture of cumulus plagioclase and mafic intercumulus melt, after the plagioclase had separated from any cogenetic mafic minerals and had become concentrated into a crystal mush (approximately 70 wt% plagioclase, 30 wt% intercumulus melt). We present a model for the crystallization of the igneous system wherein "system" is defined as cumulus plagioclase and intercumulus melt. The initial accumulation of plagioclase is analogous to the formation of thick anorthosites of the terrestrial Stillwater Complex; however, a second stage of formation is indicated, involving migration of the cumulus-plagioclase-intercumulus-melt system to a higher crustal level, analogous to the emplacement of terrestrial massif anorthosites. Compositional variations of the lithic fragments from sample 67513 are consistent with dominantly equilibrium crystallization of intercumulus melt. The highly calcic nature of orthocumulus pyroxene and plagioclase suggests some reaction between the intercumulus melt and cumulus plagioclase, perhaps facilitated by some recrystallization of cumulus plagioclase. Bulk compositions and mineral assemblages of individual rock fragments also require that most of the mafic minerals fortned in close contact with cumulus plagioclase, not as separate layers. The distribution of compositions (and by inference, modes) has a narrow peak at anorthosite and a broader, larger

  13. Arrested diatreme development: Standing Rocks East, Hopi Buttes, Navajo Nation, USA

    Science.gov (United States)

    Lefebvre, Nathalie S.; White, James D. L.; Kjarsgaard, Bruce A.

    2016-01-01

    Maar-diatreme volcanoes, defined by their relatively large pyroclastic debris-filled subsurface structures and craters that cut into the pre-eruptive land surface, are typically found in small-volume mafic to ultramafic monogenetic volcanic fields. Diatremes are associated with strong explosions throughout most of their development, focused along feeder dikes and generally attributed to magma-water interaction, or high magmatic volatiles. Detailed mapping of the magnificently exposed Standing Rocks East (SRE) diatreme shows evidence of additional eruptive complexity, and offers new insights into how the plumbing and vent structures of small-volume volcanoes evolve during an eruption. SRE is part of a larger, basanitic volcanic complex that includes several diatremes formed along a series of irregular, offset NW-SE trending dikes exposed 300 m below the pre-eruptive land surface. Its similarly oriented elliptical-shaped diatreme structure comprises predominantly country rock lithic-rich breccia of coarse inhomogeneously mixed wall-rock blocks sourced from above and below the current surface, plus sparse juvenile material. Domains of pyroclastic deposits crosscut the country rock breccia deposits, and the best exposed is the NW massif rising 35 m above the current erosional surface. It represents a cross-section of an evolving crater floor, and comprises matrix-rich lapilli tuff and spatter deposits cut by irregularly distributed dikes, some with very complex textures. The most significant deposit, in terms of volume, is an unbedded lapilli tuff that is poorly sorted and has a well-mixed population of wall-rock and juvenile clast varieties, thus resembling deposits typical of diatremes. It is overlain by and locally intercalated with spatter deposits, and this irregular contact demarcates the base of what was during eruption an uneven, evolving crater floor. The generally massive, variably welded spatter deposits constitute mostly lapilli-sized juvenile clasts with

  14. Petrología y geoquímica de la unidad ígnea Quebrada Blanca, sierra de la Huerta, Provincia de San Juan Petrology and geochemistry of the Quebrada Blanca Igneous Unit, Sierra de La Huerta, province of San Juan.

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    Brígida Castro de Machuca

    2011-12-01

    group of similar age and magmatic features distributed in the cited range. It comprises a hypabyssal rhyolite porphyry, a hydrothermal-intrusive breccia wherein two facies with contrasting texture and composition were distinguished, and felsite/rhyolite dikes. This association defines the root zone of a diatreme-type breccia which has been exposed by erosion. Breccia formation was associated with crystallization of the porphyry rhyolite, explosive brecciation, and exsolution of magmatic hydrothermal fluids which broke off and carried upward fragments of the solidified porphyry carapace and metamorphic wall rocks. The rhyolite porphyry was emplaced afterwards probably occupying the feeder conduit. The geochemistry data indicate a high-silica, subalkaline, high-K calk-alkaline and metaluminous to slightly peraluminous affinity for the Quebrada Blanca igneous Unit. Large-ion lithophile elements contents are high whilst Sr, P and Ti contents are low. They show enrichment of LREE and HREE depletion (La/YbN = 3.37 to 13.67. Geochemical characteristics are compatible with igneous rocks related to volcanic arcs. The studied rocks are tentatively correlated to the dacitic-rhyolitic upper section of the Choiyoi Group and could be assigned to the final stages of the continental magmatic arc developed along the western margin of Gondwana since the Late Carboniferous.

  15. Electron Backscatter Diffraction (EBSD) Analysis and U-Pb Geochronology of the Oldest Lunar Zircon: Constraining Early Lunar Differentiation and Dating Impact-Related Deformation

    Science.gov (United States)

    Timms, Nick; Nemchin, Alexander; Grange, Marion; Reddy, Steve; Pidgeon, Bob; Geisler, Thorsten; Meyer, Chuck

    2009-01-01

    The evolution of the early moon was dominated by two processes (i) crystallization of the Lunar Magma Ocean (LMO) and differentiation of potassium-rare earth element-phosphorous-rich residual magma reservoir referred to as KREEP, and (ii) an intense meteorite bombardment referred to as lunar cataclysm . The exact timing of these processes is disputed, and resolution relies on collection and interpretation of precise age data. This study examines the microstructure and geochronology of zircon from lunar impact breccias collected during the Apollo 17 mission. A large zircon clast within lunar breccia 72215,195 shows sector zoning in optical microscopy, cathodoluminescence (CL) imaging and Raman mapping, and indicates that it was a relict fragment of a much larger magmatic grain. Sensitive high resolution ion microprobe (SHRIMP) U-Pb analysis of the zircon shows that U and Th concentration correlate with sector zoning, with darkest CL domains corresponding with high-U and Th (approx.150 and approx.100 ppm respectively), and the brightest-CL sectors containing approx.30-50 ppm U and approx.10-20 ppm Th. This indicates that variations in optical CL and Raman properties correspond to differential accumulation of alpha-radiation damage in each sector. Electron backscatter diffraction (EBSD) mapping shows that the quality of electron backscatter patterns (band contrast) varies with sector zoning, with the poorest quality patterns obtained from high-U and Th, dark-CL zones. EBSD mapping also reveals a deformation microstructure that is cryptic in optical, CL and Raman imaging. Two orthogonal sets of straight discrete and gradational low-angle boundaries accommodate approx.12 misorientation across the grain. The deformation bands are parallel to the crystallographic {a}-planes of the zircon, have misorientation axes parallel to the c-axis, and are geometrically consistent with formation by dislocation creep associated with {010} slip. The deformation bands are unlike curved

  16. Enigmatic diamonds in Archean calc-alkaline lamprophyres of Wawa, southern Ontario, Canada

    Science.gov (United States)

    de Stefano, Andrea; Lefebvre, Nathalie; Kopylova, Maya

    2006-02-01

    A suite of 80 macrodiamonds recovered from volcaniclastic breccia of Wawa (southern Ontario) was characterized on the basis of morphology, nitrogen content and aggregation, cathodoluminescence (CL), and mineral inclusions. The host calc-alkaline lamprophyric breccias were emplaced at 2.68-2.74 Ga, contemporaneously with voluminous bimodal volcanism of the Michipicoten greenstone belt. The studied suite of diamonds differs from the vast majority of diamond suites found worldwide. First, the suite is hosted by calc-alkaline lamprophyric volcanics rather than by kimberlite or lamproite. Second, the host volcanic rock is amongst the oldest known diamondiferous rocks on Earth, and has experienced regional metamorphism and deformation. Finally, most diamonds show yellow-orange-red CL and contain mineral inclusions not in equilibrium with each other or their host diamond. The majority of the diamonds in the Wawa suite are colorless, weakly resorbed, octahedral single crystals and aggregates. The diamonds contain 0-740 ppm N and show two modes of N aggregation at 0-30 and 60-95% B-centers suggesting mantle storage at 1,100-1,170°C. Cathodoluminescence and FTIR spectroscopy shows that emission peaks present in orange CL stones do not likely result from irradiation or single substitutional N, in contrast to other diamonds with red CL. The diamonds contain primary inclusions of olivine (Fo92 and Fo89), omphacite, orthopyroxene (En93), pentlandite, albite, and An-rich plagioclase. These peridotitic and eclogitic minerals are commonly found within single diamonds in a mixed paragenesis which also combines shallow and deep phases. This apparent disequilibrium can be explained by effective small-scale mixing of subducted oceanic crust and mantle rocks in fast “cold” plumes ascending from the top of the slabs in convergent margins. Alternatively, the diamonds could have formed in the pre-2.7-2.9 Ga cratonic mantle and experienced subsequent alteration of syngenetic inclusions

  17. An integrated paleomagnetic and diagenetic investigation of the Barnett shale and underlying Ellenburger Group carbonates, Fort Worth Basin, Texas

    Science.gov (United States)

    Dennie, Devin P.

    The Ordovician Ellenburger Group carbonates are extensively karsted and brecciated throughout portions of the western half of the Fort Worth Basin, Texas, where it underlies the Mississippian Barnett Shale gas reservoir and source rock. An integrated geochemical/petrographic, paleomagnetic and rock magnetic study was conducted to better understand the nature and timing of diagenetic events in the unit. Samples from three scribe oriented conventional drill cores of the uppermost Ellenburger Group carbonates were analyzed for their diagenetic and paleomagnetic properties. Thermal demagnetization of samples from both units reveals a low-temperature steeply downward viscous remanent magnetization (VRM) as well as several components that are removed at higher temperatures (200-540°C). The higher temperature components reside in magnetite and are interpreted as chemical remanent magnetizations (CRMs) based on low burial temperatures. The specimen directions are streaked from an easterly and shallow direction to a southerly and shallow direction. The modern VRM was used to orient the CRM data for one of the wells and to test the scribe orienting method. The results confirm that the streak of directions is real. The streak disappears when the directions are grouped by diagenetic facies. Specimens from clasts in the karst breccia facies contain a CRM with easterly declinations and shallow inclinations that fails a conglomerate test and has an Ordovician pole. A mixed dolomite-limestone with shale filled fracture facies contains a pole which falls off of but close to the Late Mississippian-Early Pennsylvanian part of the apparent polar wander path. A group of facies (crystalline dolomite, wavy bedded to argillaceous dolomite, mottled, burrowed dolomite with fine grained breccia facies, and clastic-rich peritidal carbonates) contains a Late Permian-Early Triassic CRM. Dolomites with vug-fill solution-reprecipitation features contain a Late Triassic-Jurassic CRM. The results

  18. Interpretasi Mineralisasi Epitermal Berdasarkan Studi Ubahan Hidrotermal dan Tekstur Urat Kuarsa di Kawasan Hutan Lindung Taliwang, Nusa Tenggara Barat

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    Danny Zulkifli Herman

    2014-06-01

    Full Text Available http://dx.doi.org/10.17014/ijog.vol2no3.20072Taliwang conservation forest, West Nusa Tenggara, is particularly covered by volcanic rocks consisting of alternated breccia and tuff. The breccia is composed of andesitic – dioritic clasts and matrix of fine-grained to lapilli tuff which had partially been hidrothermally altered and invaded by gold bearing quartz veins. Outcrops of quartz veins are commonly limonitized, trending nearly east-west and north-south with respectively dip of 70o and 85o. Identification of quartz veins originated from people mining’s waste leads to a prediction that there are quartz stockworks beneath the earth surface (50 – 100 m depth in the conservation forest area, from which quartz veins penetrated the illite-paragonite-calcite-siderite- nacrite altered country rock. Textures of quartz veins were identified such as comb with some coarse- grained euhedral crystals, sugary/saccharoidal/fine grained crystalline quartz and ghost-bladed. Veins and host rocks generally contain disseminated and spotted pyrites. Evaluation of quartz textures, altered rocks analysis (PIMA method, fluid inclusion studies and chemical analysis (AAS method of selective altered rocks/quartz vein samples exhibits that the alteration and mineralization processes might occur in an epithermal system, connecting with a change of hydrothermal fluids from near neutral into acid conditions at a temperature ranging from 231 to 185oC. Alteration of illite-paragonite-kalsit-siderite is suggested as a result of reaction between host rock and a near neutral fluid, whilst nacrite (kaolin group or argillic is a result of reaction between host rock and an acid fluid, within a mixing zone of meteoric fluid and condensed acid gas released during boiling process of hydrothermal fluid in the depth. On the basis of salinity ranging from 0.9 to 2.2 equivalent wt.% NaCl of fluid inclusion, it is predicted that the deposition of gold bearing quartz and associated

  19. JURASSIC PALAEOGEOGRAPHY OF THE TRANSDANUBIAN CENTRAL RANGE (HUNGARY

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    ATTILA VÖRÖS

    1998-03-01

    Full Text Available The Transdanubian Central Range (TCR is a flattened range of hills in northern Transdanubia (Hungary, formed mainly by Mesozoic carbonate rocks showing strong facies similarities with the Southern Alps and the Austroalpine domain. The Jurassic system is divided into several formations of predominantly pelagic limestones. Ammonoids are frequent and were collected bed-by-bed in numerous sections, providing an excellent biostratigraphic resolution. The thickness of the Jurassic system is usually small but changes along the strike of the TCR. It reaches a maximum thickness of 500 m in the western part; is very variable (10-400 m in the central segment (Bakony Mts. and rather low (less than 100 m in the east (Gerecse. In the Bakony segment, the thickness variation reflects the strongly dissected topography of the Jurassic sea-floor. Synsedimentary tectonics is dominated by normal faults; tilted blocks and listric faults may be inferred only in the east.Five main steps were identified in the palaeogeographic evolution: 1 Late Hettangian: carbonate oolitic shoals prevail, except for a few sites where non-deposition or neritic sediments occur. 2 Sinemurian and Pliensbachian: tectonic disintegration resulted in an intricate pattern of submarine horsts and intervening basins, with condensed sedimentation or non-deposition on the horsts and thicker, continuous sedimentary sequences in the basins. The submarine topographic highs are surrounded by aprons of redeposited material (scarp breccias, brachiopod coquinas, crinoidal calcarenites, spiculitic cherty limestones, while pure or argillaceous limestones (Rosso Ammonitico prevail in the distal areas. 3 Early Toarcian: the Tethys-wide anoxic event is superimposed on the previous submarine bottom topography; the resulting black shales and sedimentary Mn-ores are concentrated on the western sides of some horsts. 4 Dogger to Early Malm: radiolarites with heterochronous lower and upper boundaries (Aalenian to

  20. The Kharapeh orogenic gold deposit: Geological, structural, and geochemical controls on epizonal ore formation in West Azerbaijan Province, Northwestern Iran

    Science.gov (United States)

    Niroomand, Shojaeddin; Goldfarb, Richard J.; Moore, Farib; Mohajjel, Mohammad; Marsh, Erin E.

    2011-01-01

    The Kharapeh gold deposit is located along the northwestern margin of the Sanandaj–Sirjan Zone (SSZ) in the West Azerbaijan province, Iran. It is an epizonal orogenic gold deposit formed within the deformed zone between central Iran and the Arabian plate during the Cretaceous–Tertiary Zagros orogeny. The deposit area is underlain by Cretaceous schist and marble, as well as altered andesite and dacite dikes. Structural analysis indicates that the rocks underwent tight to isoclinal recumbent folding and were subsequently co-axially refolded to upright open folds during a second deformation. Late- to post-tectonic Cenozoic granites and granodiorites occur northeast of the deposit area. Mineralization mainly is recognized within NW-trending extensional structures as veins and breccia zones. Normal faults, intermediate dikes, and quartz veins, oriented subparallel to the axial surface of the Kharapeh antiform, indicate synchronous extension perpendicular to the fold axis during the second folding event. The gold-bearing quartz veins are >1 km in length and average about 6 m in width; breccia zones are 10–50 m in length and ≤1 m in width. Hydrothermal alteration mainly consists of silicification, sulfidation, chloritization, sericitization, and carbonatization. Paragenetic relationships indicate three distinct stages—replacement and silicification, brecciation and fracture filling, and cataclastic brecciation—with the latter two being gold-rich. Fluid inclusion data suggest mineral deposition at temperatures of at least 220–255°C and depths of at least 1.4–1.8 km, from a H2O–CO2±CH4 fluid of relatively high salinity (12–14 wt.% NaCl equiv.), which may reflect metamorphism of passive margin carbonate sequences. Ore fluid δ18O values between about 7‰ and 9‰ suggest no significant meteoric water input, despite gold deposition in a relatively shallow epizonal environment. Similarities to other deposits in the SSZ suggest that the deposit formed as

  1. Stable isotope systematics and fluid inclusion studies in the Cu-Au Visconde deposit, Carajás Mineral Province, Brazil: implications for fluid source generation

    Science.gov (United States)

    da Costa Silva, Antonia Railine; Villas, Raimundo Netuno Nobre; Lafon, Jean-Michel; Craveiro, Gustavo Souza; Ferreira, Valderez Pinto

    2015-06-01

    The Cu-Au Visconde deposit is located in the Carajás Mineral Province (CMP), northern Brazil, near the contact between the ca. 2.76 Ga metavolcano-sedimentary rocks of the Itacaiunas Supergroup rocks and the ~3.0 Ga granitic-gneissic basement. It is hosted by mylonitized Archean rocks, mainly metadacites, the Serra Dourada granite, and gabbros/diorites, which have been successively altered by sodic, sodic-calcic-magnesian, potassic, and calcic-magnesian hydrothermal processes, producing diverse mineralogical associations (albite-scapolite; albite-actinolite-scapolite-epidote; K-feldspar-biotite; chlorite-actinolite-epidote-calcite, etc.). Chalcopyrite is the dominant ore mineral and occurs principally in breccias and veins/veinlets. The aqueous fluids responsible for the alteration/mineralization were initially hot (>460 °C) and very saline (up to 58 wt.% equivalent (equiv.) NaCl), but as the system evolved, they experienced successive dilution processes. Mineral oxygen and hydrogen isotope data show that 18O-rich ( to +9.4 ‰) fluids prevailed in the earlier alteration (including magnetitites) and reached temperatures as high as 410-355 °C. Metamorphic/formation waters, most likely derived from the Carajás Basin rocks, appear to have contributed a major component to the fluid composition, although some magmatic input cannot be discounted. In turn, the later alterations and the mineralization involved cooler (<230 °C), 18O-depleted ( to +3.7 ‰) and less saline (7-30 wt.% equiv. NaCl) fluids, indicating the influx of meteoric water. Fluid dilution and cooling might have caused abundant precipitation of sulfides, especially as breccia cement. Ore δ 34 S values (+0.5 to +3.4 ‰) suggest a magmatic source for sulfur (from sulfide dissolution in pre-existing igneous rocks). The chalcopyrite Pb-Pb ages (2.73 ± 0.15 and 2.74 ± 0.10 Ga) indicate that the Visconde mineralization is Neoarchean, rather than Paleoproterozoic as previously considered. If so, the

  2. Uranium exploration in the Proterozoic terranes of India: a petrometallographic study and implication on target selection

    International Nuclear Information System (INIS)

    Proterozoic terranes of India host different types of uranium mineralization like palaeo-placer, magmatic-syngenetic, magmatic-epigenetic, metamorphic-hydrothermal, and sedimentary polygenetic. Important characteristics of each type in terms of lithology, petromineragraphy, geochemistry, geochronology, metamorphism and structure are summarized, with listing of typical examples of each. Based on this account, broad exploration guides for these types are indicated. These are: (a) lithological -crustal-derived, fertile acidic rocks like granitoids and syenitoids as well as their variants that serve both as host for magmatic-syngenetic and-epigenetic types and provenance for other types, low-grade metavolcaniclastic rocks for metamorphic-hydrothermal type, and phosphatic carbonate rocks for the carbonate-hosted sedimentary polygenetic type; (b) mineralogical -presence of volatile rich and reductant phases, dominance of microcline over orthoclase in granitoids and syenitoids, and alteration zones involving volatilization reactions; (c) geochemical- S- and A-type granitoids, zones of reduction with high contents of P,F,S,C, and H2O, (87Sr/86Sr)i of more than 0.705 for granitoids permeability and porosity barriers, sudden changes in Eh-pH conditions as at the contact between two different rock types, and impurities of P and Si carbonate rocks (d) metamorphic - low grade metamorphic rocks, mainly of greenschist and rarely of epidote-amphibolite facies and zones of K-Fe-Mg-P-B-metasomatism, and (e) structural - major shears, thrusts, faults, and unconformities at the regional scale, and fractures, cross-folds, and sedimentary structures like ripple marks at the local scale, the latter for better grade. For the two major types of uranium deposits viz. unconformity related and breccia-complex, that are not recorded hitherto, it is suggested that marginal zones of the Proterozoic basins containing fertile basement rocks covered by impervious sedimentary rocks with an

  3. Geological setting of the Olkiluoto investigation site, Eurajoki, SW Finland. Excursion guidebook

    Energy Technology Data Exchange (ETDEWEB)

    Paulamaeki, S. (Geological Survey of Finland, Espoo (Finland))

    2009-08-15

    -1250 million years in age. Their geochemical features suggest that they are feeder channels to continental flood basalts, which have not, however, been preserved in the Satakunta area. Lake Saeaeksjaervi, northeast of the Satakunta sandstone, hosts approximately 4.5 km wide impact structure of early Cambrian age (ca. 560 Ma). Below water level it contains unexposed suevite breccia and impact melt breccia. Day 1 of the field excursion introduces the Palaeoproterozoic geology of the Olkiluoto site, with special emphasis to the structural geology. Day 2 presents the Mesoproterozoic history of southern Satakunta area, including the Laitila and Eurajoki rapakivi granites, the Satakunta sandstone and the olivine diabases. The excursion ends to the Lake Saeaeksjaervi, where boulders of impact rocks can be found on the northern shore of the lake. (orig.)

  4. Análisis sedimentológico de la Cuenca estefaniense de Tineoo (Asturias. Ejemplo de depósitos de carbón en abanicos aluviales

    Directory of Open Access Journals (Sweden)

    Santos García, J. A.

    1991-04-01

    Full Text Available A sedimentological analysis of the stephanian deposits of Tineo Basin is carried out. Three unities are established (Basal Breachs, Intermediate Unit and Conglomerate Unit by means of lithological, mining and sedimentological criteria, which represent larger episodes in the filling of the basin. The first episode corresponds to the initial configuration of the basin, with coarse grained breccia deposits related to steep slopes (Basal Breccia. The second and more complex (Intermediate Unit, is represented by four larger sequences (stages from UI-l to UI-4, La Prohida Zone which show secondary tectonic pulsations. At this moment the sedimentation is carried out in several subbasins separated by palaeoreliefs or thresholds. The third episode correspond to a strong reactivation of the northern edge of the basin, with deposition of the Conglomeratic Unit. The filling of the basin is assimilated to a pattern of alluvial fans in a tectonically-active basin, in which the coal deposition look place during calm (tranquil periods when a large alluvial fan flanked by coalescent smaller sized fans developped alongs the northern margin of the basin.En este trabajo se realiza el análisis sedimentológico de los depósitos estefanienses de la cuenca de Tineo. Se establecen 3 unidades (Brechas Basales, U. Intermedia y U. Conglomerática, en base a criterios litológicos, mineros y sedimentológicos, que representan episodios mayores en el relleno de la cuenca. El primer episodio corresponde a la configuración inicial de la cuenca, formándose depósitos relacionados con áreas de fuertes pendientes (Brechas Basales. El segundo y más complejo (U. Intermedia, está representado por 4 secuencias mayores (etapas UI-l a UI-4, zona de La Prohida, que denotan pulsaciones tectónicas secundarias. En este momento, la sedimentación se realiza en varias subcuencas, separadas por paleorelieves o umbrales. El tercer episodio indica una fuerte reactivación del borde

  5. Enigmatic carbonates of the Ombombo Subgroup, Otavi Fold Belt, Namibia: A prelude to extreme Cryogenian anoxia?

    Science.gov (United States)

    Hood, A. v. S.; Wallace, M. W.; Reed, C. P.; Hoffmann, K.-H.; Freyer, E. E.

    2015-07-01

    The Ombombo Subgroup of the Otavi Fold Belt, Kaokoveld, Namibia preserves a succession of clastic and carbonate sediments with unusual sedimentary features. The stratigraphy of these units is discussed here in detail for the first time since their initial definition, with particular emphasis on the sedimentology of carbonate units. Early Neoproterozoic shales of the Beesvlakte Formation, equivalent to the Zambian Katangan Copperbelt's Lower Roan Formation, host evaporitic lithologies and minor copper mineralisation. The overlying, dolomitic ~ 760 Ma Devede Formation contains carbonate platformal lithologies which are in many ways dissimilar to Phanerozoic shallow-water carbonates. This includes unusual "curl breccias", sheet cavities, carbonate shrubs, and tepee carbonate lithologies which contain large quantities of fibrous cements. "Curl breccias" are defined here as distinctive, curled intraclasts of laminated dolomite that often have shrinkage cracks in their margins, and are cemented by fibrous dolomite cements. Fibrous cements take on two forms: an early, length-fast fascicular-optic dolomite and a later length-slow phase with unit extinction. The presence of overlying internal sediments, the fibrous habit of these first-generation cements, as well as their preserved cathodoluminescent and optical character, suggests that these cements originally precipitated as calcite and dolomite marine cements respectively. After this initial marine calcite precipitation, all components of Devede Formation carbonates have been mimetically dolomitised, preserving original depositional fabrics. Combined with the presence of marine dolomite cements, this style of dolomitisation is suggested to be syn-sedimentary, similar to that of some Cryogenian dolomites, suggesting unusual ocean conditions during the Early Neoproterozoic. In particular, the presence of dolomite marine cements, which have been linked to ocean anoxia and high seawater Mg/Ca conditions, suggests that the

  6. Porosity characterization of fresh and altered stones by ultrasound velocity and mercury intrusion porosimetry

    Science.gov (United States)

    Scrivano, Simona; Gaggero, Laura; Gisbert Aguilar, Josep

    2016-04-01

    Porosity is the main physical feature dealing with rocks durability and storage capacity. The analysis of this parameter is key factor in predicting rock performances (Molina et al., 2011). There are several techniques that can be applied to acquire the widest information range possible about pores (e.g. size, shape, distribution), leading to a better understanding of decay processes and trapping capacity. The coupling of a detailed minero-petrographic analysis with physical measures such as ultrasounds and mercury intrusion porosimetry (MIP) proved to be a valid tool for understanding the porous network and its evolution during weathering processes. Both fresh and salt-weathered samples were analysed to investigate the modification triggered in the porous network by crystallization. The ageing process was induced using a Na2SO4 saturated saline solution with the partial continuous immersion method (Benavente et al., 2001). The study was addressed to four sedimentary lithotypes: 1) Arenaria Macigno, a greywacke made up of thickened clasts of quartz, plagioclase and K-feldspar cemented by micritic calcite and phyllosilicates; 2) Breccia Aurora, a calcareous breccia with nodules of compact limestone and micritic cement joints; 3) Rosso Verona, a biomicrite where the compact bio-micrite matrix is cut by clay minerals veins; and 4) Vicenza Stone, an organogenic limestone rich in micro- and macro foraminifera, algae, bryozoans and remains of echinoderms, with iron oxides. An appropriate description of the porous network variation and recognition of the origin of secondary porosity was attained. The study defined that the pore shape and distribution (anisotropy coefficient K) has a fluctuation up to the 50% after weathering treatments and pore-size distribution (defined in a range between 0,0025 - 75 μm), allowing modelling the mechanisms of water transport and evaluating decay susceptibility of these lithotypes. Molina E, Cultrone G, Sebastián E, Alonso FJ, Carrizo L

  7. Chicxulub Impact Crater and Yucatan Carbonate Platform - Stratigraphy and Petrography of PEMEX Borehole Cores

    Science.gov (United States)

    Gutierrez-Cirlos, A. G.; Perez-Drago, G.; Perez-Cruz, L.; Urrutia-Fucugauchi, J.

    2008-12-01

    Chicxulub impact crater is the best preserved of the three large multi-ring structures documented in the terrestrial record. Chicxulub, formed 65 Ma ago, is associated with the Cretaceous/Tertiary (K/T) boundary layer and the impact related to the organism extinctions and events marking the boundary. The crater is buried under Tertiary sediments in the Yucatan carbonate platform in the southern Gulf of Mexico. The structure was initially recognized from gravity and magnetic anomalies in the PEMEX exploration surveys of the northwestern Yucatan peninsula. The exploration program included eight deep boreholes completed from 1952 through the 1970s. The investigations showing Chicxulub as a large complex impact crater formed at the K/T boundary have relayed on the PEMEX decades-long exploration program. However, despite frequent use of PEMEX information and core samples, significant parts of the database and cores remain to be evaluated, analyzed and incorporated with results from recent efforts. Access to PEMEX Core Repository has permitted to study the cores and collect new samples from some of the boreholes. We analyzed cores from Yucatan-6, Chicxulub-1, Sacapuc-1, Ticul-1, Yucatan-1 and Yucatan-4 boreholes to make new detailed stratigraphic correlations and petrographic characterization, using information from PEMEX database and the recent studies. In C-1 cores, breccias show 4-8 cm clasts of fine grained altered melt dispersed in a medium to coarse grained matrix composed of pyroxene and feldspar with little macroscopic alteration. Clasts contain 0.2 to 0.1 cm fragments of silicate material (basement) that show variable degrees of digestion. Melt samples from C-1 N10 comes from interval 1,393-1,394 m, and show a fine-to-medium grained coherent microcrystalline groundmass. Melt and breccias in Y-6 extend from about 1,100 m to more than 1,400 m. Sequence is well sorted, with an apparent gradation in both the lithic and melt clasts. In this presentation we report on

  8. The Chicxulub event - sulfur-bearing minerals and lithologies

    Science.gov (United States)

    Strauss, H.; Deutsch, A.

    2003-04-01

    Evaporates form a major target lithology at the Chicxulub impact site. One of the postulated effects of the impact event at the Cretaceous/Tertiary boundary is the impact-induced dissociation of anhydrite to form sulfur-oxides and a solid residue; large isotope fractionation effects in sulfur should accompany this process. We have analyzed the sulfur isotope composition of (i) annealed anhydrite clasts in impact melt breccias of PEMEX core Yucatan-6 N 19, (ii) unshocked anhydrite from the CSDP well Yaxcopoil-1, which belong to the megabreccia below the suevite layer (YAX-1 1369, and 1376 m depth), and (iii) sulfide grains of hydrothermal origin in a finest-grained breccia, which transects a large limestone block of this megabreccia at a depth of 1369 m. Samples of groups (i) and (ii) yielded δ34S values between 18.0 and 19.8 ppm CDT (unweighted mean is 18.3 ppm, n=7), with one slightly lower value of 15.3 ppm for an anhydrite clast in Y-6 N19/Part 6. These data are in agreement with the δ34S value for the Late Cretaceous seawater (Strauss 1999). The δ34S obviously remained unchanged despite the fact that textural features indicate a severe annealing of the clasts in the impact melt. Sulfides of group (iii) show δ34S values around 41 ppm CDT (n=7), which are quite unusual values if these minerals are of non-biogenic origin. In contrast, δ34S for the yellow glass from the K/T boundary at Haiti range from 1.5 to 13.2 ppm (Chaussidon et al. 1996). Using this preliminary evidence, we conclude that only distant ejecta lithologies, and probably secondary material inside the crater, may display impact-related fractionation of sulfur isotopes. This observation is consistent with petrologic data, modeling results as well as of shock recovery and annealing experiments: anhydrite obviously is quite resistant to shock-related dissociation.

  9. What the rock record tells us about ocean crustal faulting

    Science.gov (United States)

    Hayman, N. W.

    2014-12-01

    Imaging and monitoring efforts along mid-ocean ridges, transform faults, and forebulges of subduction zones raise some apparently contradictory points about faulting in the oceanic lithosphere. Faults are conduits to fluid flow, but also reside within broader flow fields that extend beyond the fault planes themselves. Fault-zone properties appear to govern slip dynamics, yet seismicity and deformation also occur far off the map-trace of faults. Geologic observations of fast-spread oceanic crust exposed in seafloor escarpments and analogs in ophiolites offer some insight. (i) The upper crust — the sheeted dikes and deepest lavas — is highly altered, both within fault zones through which hydrothermal fluids flowed, but also in surrounding, low-permeability basaltic rock. (ii) The upper crust is highly fractured over areas tens-of-meters wide, despite relatively low (meters-to-tens of meters) fault displacements. (iii) Detailed structural mapping of such sections finds that fractures become more densely spaced toward fault zones, achieving a critical spacing of ~1 cm, below which the basaltic material is comminuted to breccia and gouge. (iv) Breccia and gouge also have characteristic grain sizes of ~1 cm, below which grain-size distributions steepen. (v) In experiments conducted in the Penn State Rock Mechanics Lab, altered basaltic fault rocks tended to be moderately weak and velocity strengthening. Putting i-v together paints a picture wherein gouge-filled faults indeed localize both fluid flow and stable sliding, but also reside within damage zones which host most of the active seismicity and within which penetrative fluid flow also occurs. Though these observations predominantly come from windows into subaxial processes, this damaged and altered crust is spread off axis where it is deformed and reactivated by transform and bend faults. Moreover, new faults and fractures formed off axis may well follow the same patterns of localization as subaxial faults, minus

  10. Juxtaposition of adakite, boninite, high-TiO 2 and low-TiO 2 basalts in the Devonian southern Altay, Xinjiang, NW China

    Science.gov (United States)

    Niu, Hecai; Sato, Hiroaki; Zhang, Haixiang; Ito, Jun'ichi; Yu, Xueyuan; Nagao, Takashi; Terada, Kentaro; Zhang, Qi

    2006-12-01

    We present petrographic and geochemical data on representative samples of the Devonian adakite, boninite, low-TiO 2 and high-TiO 2 basalts and associated rocks in the southern Altay areas, Xinjiang, NW China. These volcanic rocks mostly occur as tectonic blocks within suture zones between the Siberian and Junggar plates. Adakite occurs in the Suoerkuduke area ca. 40 km south of Fuyun, and actually represents a poorly-sorted massive volcaniclastic deposit, mostly consisting of a suite of hornblende andesite to pyroxene andesite. The geochemical features of the adakite suggest its generation by melting of subducted oceanic crust. Boninite occurs in the Saerbulake area ca. 20 km southwest of Fuyun, as pillowed lava or pillowed breccia. It is associated with high-TiO 2 basalt/gabbro and low-TiO 2 basalt. The boninites are metamorphosed, but contain relict clinopyroxene with Mg# (=100*Mg/(Mg+Fe)) of 90-92, and Cr 2O 3 contents of 0.5-0.7 wt% and chromian spinel with Cr/(Cr+Al) ratio of 0.84. The bulk rock compositions of the boninites are characterized by low and U-shaped REE with variable La/Yb ratios. They are classified as high-Ca boninite. The Cr-rich cpx phenocryst and Chromian spinel suggests that the boninites were formed by melting of mildly refractory mantle peridotite fluxed by a slab-derived fluid component under normal mantle potential temperature conditions. Basaltic rocks occur as massive flows, pillowed lavas, tuff breccia, lapilli tuff and blocks in tectonic mélanges. Together with gabbros, the basaltic rocks are classified into high-TiO 2 (>1.7 wt%) and low-TiO 2 (<1.5 wt%) types. They show variable trace element compositions, from MORB-type through transitional back-arc basin basalt to arc tholeiite, or within plate alkalic basalt. A notable feature of the Devonian formations in the southern Altay is the juxtaposition of volcanic rocks of various origins even within a limited area; i.e. the adakite and the boninites are associated with high-TiO 2 and

  11. Petrology, geochemistry, and tectonic implications of newly collected samples from Babeldaob Island, Republic of Palau

    Science.gov (United States)

    Reagan, M.; Ishizuka, O.; Hawkins, J.; Bloomer, S.; Fryer, P.; Ishii, T.; Kelley, K.; Kimura, J.; Michibayashi, K.; Ohara, Y.; Stern, R.; Blake, B.; Colin, P.; Colin, L.

    2006-12-01

    The islands of Palau in the Western Pacific mark the southern end of the Kyushu-Palau Ridge, which is the westernmost remnant arc of the Izu-Bonin-Mariana (IBM) system. Because it has extensive subaerial exposures of volcanic rocks, it offers an excellent opportunity for detailed geological and petrological investigation. The largest island of Palau, Babeldaob, is composed largely of volcanic materials erupted between the middle Eocene and Oligocene (Mason et al., 1956; Meijer et al., 1983; Cosca et al., 1998). Previous studies have been hampered by thick laterites but nevertheless have shown that boninites and more typical arc basalts and andesites make up these materials. These studies also suggest that early arc sequences similar to those identified along the IBM forearc to the north are also found here (Hawkins and Castillo, 1998). Road cutting and quarrying for the new "Compact Road" around Babeldaob have recently provided unprecedented exposures of the volcanic units. The scientific party for Cruise YK0612 of the R/V Yokosuka spent one day examining and sampling some of these outcrops. Here, we report geological impressions of these outcrops and preliminary petrological and geochemical data for these newly exposed volcanic rocks. The new outcrops expose volcanic conglomerates, breccias, and finer-grained sediments; lava flows, pillow lavas, dikes, and volcanic plugs. Some of the coarse sediments are massive and matrix- supported, and probably were deposited by debris flows. These are interbedded with normally graded turbidite sequences, suggesting subaqueous deposition. A quarry near the east-central coast exposed a complex of meter-scale dikes cut by fault gouge zones. Shallow dome and breccia deposits as well as a pillow lava sequence cropped out in a quarry and a road-cut respectively along the central spine of the island. Most samples are broadly basaltic to andesitic and boninitic, although hornblende andesites or dacites compose the dome and one section

  12. Hydrocarbons and Au Deposits (and Their Pyrite) - Is There a Link?

    Science.gov (United States)

    Stein, H. J.; Bingen, B.; Yang, G.; Ihlen, P.

    2008-12-01

    Non-economic and isolated occurrences of hydrocarbon are known in the rock record. Among these is the somewhat common association of hydrocarbon veins and breccia fillings observed at Au deposits. This association begs investigation of the genetic association between hydrocarbon and Au deposition. To address this question we obtained a suite of Au-associated pyrites and cross-cutting hydrocarbon occurrences (referred to as coalblende in the vernacular) that are typical of the ore at the Eidsvoll Au deposit in SE Norway. The Au mineralization at Eidsvoll has long been attributed to a Late Sveconorwegian continental-scale terrane boundary along the SW margin of Fennoscandia, known as the Mylonite Zone (1000-970 Ma). Eidsvoll is located in the MZ but ore-hosting structures clearly crosscut the MZ fabric. Re- Os dating of euhedral cubic pyrites provides a well-constrained 8-point isochron with a corresponding age of c. 870 Ma. Further, a second generation of fine-grained cataclastic pyrite with 187Re/188Os ratios of greater than 4000 yields early Caledonian ages of c. 440 Ma. We attribute the c. 870 Ma age to extensional reactivation of the Kristiansand-Porsgrunn shear zone separating the Bamble and Telemarkia terranes SW of the intervening Permian Oslo rift. The younger c. 440 Ma pyrite may represent cataclasis of earlier cubic pyrite leading to liberation of Au and creation of associated chalcopyrite. The c. 440 Ma age may reflect lithospheric deformation in response to loading by the encroaching Caledonian thrust sheets to the west. Late hydrocarbon fracture coatings, veins, and breccia cements are markedly present at the Eidsvoll Brustad mine where we obtained our samples. Surprisingly, Re-Os model ages for simple fracture coatings of coalblende yield Miocene ages, indicating that Au and hydrocarbon deposition are neither temporally nor genetically related. We interpret the Miocene ages as recording hydrocarbon migration into Eidsvoll rocks, likely expelled from

  13. Nondestructive Analysis of Astromaterials by Micro-CT and Micro-XRF Analysis for PET Examination

    Science.gov (United States)

    Zeigler, R. A.; Righter, K.; Allen, C. C.

    2013-01-01

    An integral part of any sample return mission is the initial description and classification of returned samples by the preliminary examination team (PET). The goal of the PET is to characterize and classify returned samples and make this information available to the larger research community who then conduct more in-depth studies on the samples. The PET tries to minimize the impact their work has on the sample suite, which has in the past limited the PET work to largely visual, nonquantitative measurements (e.g., optical microscopy). More modern techniques can also be utilized by a PET to nondestructively characterize astromaterials in much more rigorous way. Here we discuss our recent investigations into the applications of micro-CT and micro-XRF analyses with Apollo samples and ANSMET meteorites and assess the usefulness of these techniques in future PET. Results: The application of micro computerized tomography (micro-CT) to astromaterials is not a new concept. The technique involves scanning samples with high-energy x-rays and constructing 3-dimensional images of the density of materials within the sample. The technique can routinely measure large samples (up to approx. 2700 cu cm) with a small individual voxel size (approx. 30 cu m), and has the sensitivity to distinguish the major rock forming minerals and identify clast populations within brecciated samples. We have recently run a test sample of a terrestrial breccia with a carbonate matrix and multiple igneous clast lithologies. The test results are promising and we will soon analyze a approx. 600 g piece of Apollo sample 14321 to map out the clast population within the sample. Benchtop micro x-ray fluorescence (micro-XRF) instruments can rapidly scan large areas (approx. 100 sq cm) with a small pixel size (approx. 25 microns) and measure the (semi) quantitative composition of largely unprepared surfaces for all elements between Be and U, often with sensitivity on the order of a approx. 100 ppm. Our recent

  14. Mud volcano venting induced gas hydrate formation at the upper slope accretionary wedge, offshore SW Taiwan

    Science.gov (United States)

    Lin, Saulwood; Tseng, Yi-Ting; Cheng, Wan-Yen; Chou, Cheng-Tien; Chen, NeiChen; Hsieh, I.-Chih

    2016-04-01

    TsanYao Mud Volcano (TYMV) is the largest mud volcano cone in the Hengchun Mud Volcano Group (HCMVG), located at the upper slope of the accrretionary wedge, southwest of Taiwan. The region is under active tectonic activity with the Philippine Plate, moving northwestward at a rate of ~8 cm/year. This region also receives huge quantity of suspended particle load of ~100 mT/year at present time from adjacent small rivers of the Island of Taiwan. Large loads of suspended sediments influx become a major source of organic carbon and later gas and other hydrocarbon. Gas and fluid in the mud volcano are actively venting from deep to the sea floor on the upper slope of the accretionary wedge. In order to understand venting on the HCMVG, echo sounder, towcam and coring were carried out. Pore water sulfate, chloride, potassium, calcium, stable isotope O-18, gas compositions, dissolved sulfide were analysed. The HCMVG consists of 12 volcano cones of different sizes. Large quantity of gas and fluid are venting directly from deep to the TYMV structure high, as well as 50+ other vents as appeared as flares on the echo sounder. Some flares are reaching to the atmosphere and likely a source of green house gases to the atmosphere. Venting fluids include gas bubbles, suspended particle, mud, and breccia. Breccia size could reach more than 12 cm in diameter. Circular bands in different color appeared around the cone may represent stages of vent eruptions. Compositions of vent gas include methane, ethane and propane. High proportions of ethane and propane in the vent gas demonstrated that source of gas are thermogenic in origin. Patchy authigenic carbonate, bacterial mats, bivalves, tube worms and other chemosynthesis organisms were supported by venting gas AOM process near the sea floor. Pore water chloride concentrations show distinct variation pattern from center cone to the side of the volcano, with low in the center and high away from the cone. Pore water with higher than seawater

  15. Thickness distributions and evolution of growth mechanisms of NH4-illite from the fossil hydrothermal system of Harghita Bai, Eastern Carpathians, Romania

    Science.gov (United States)

    Bobos, Iuliu; Eberl, D.D.

    2013-01-01

    The crystal growth of NH4-illite (NH4-I) from the hydrothermal system of Harghita Bãi (Eastern Carpathians) was deduced from the shapes of crystal thickness distributions (CTDs). The 4-illite-smectite (I-S) interstratified structures (R1, R2, and R3-type ordering) with a variable smectite-layer content. The NH4-I-S (40–5% S) structures were identified underground in a hydrothermal breccia structure, whereas the K-I/NH4-I mixtures were found at the deepest level sampled (−110 m). The percentage of smectite interlayers generally decreases with increasing depth in the deposit. This decrease in smectite content is related to the increase in degree of fracturing in the breccia structure and corresponds to a general increase in mean illite crystal thickness. In order to determine the thickness distributions of NH4-I crystals (fundamental illite particles) which make up the NH4-I-S interstratified structures and the NH4,-I/K-I mixtures, 27 samples were saturated with Li+ and aqueous solutions of PVP-10 to remove swelling and then were analyzed by X-ray diffraction. The profiles for the mean crystallite thickness (Tmean) and crystallite thickness distribution (CTD) of NH4-I crystallites were determined by the Bertaut-Warren-Averbach method using the MudMaster computer code. The Tmean of NH4-I from NH4-I-S samples ranges from 3.4 to 7.8 nm. The Tmean measured for the NH4-I/K-I mixture phase ranges from 7.8 nm to 11.7 nm (NH4-I) and from 12.1 to 24.7 nm (K-I). The CTD shapes of NH4-I fundamental particles are asymptotic and lognormal, whereas illites from NH4-I/K-I mixtures have bimodal shapes related to the presence of two lognormal-like CTDs corresponding to NH4-I and K-I. The crystal-growth mechanism for NH4-I samples was simulated using the Galoper code. Reaction pathways for NH4-I crystal nucleation and growth could be determined for each sample by plotting their CTD parameters on an α–β2 diagram constructed using Galoper. This analysis shows that NH4-I

  16. Autonomous Segmentation of Outcrop Images Using Computer Vision and Machine Learning

    Science.gov (United States)

    Francis, R.; McIsaac, K.; Osinski, G. R.; Thompson, D. R.

    2013-12-01

    As planetary exploration missions become increasingly complex and capable, the motivation grows for improved autonomous science. New capabilities for onboard science data analysis may relieve radio-link data limits and provide greater throughput of scientific information. Adaptive data acquisition, storage and downlink may ultimately hold implications for mission design and operations. For surface missions, geology remains an essential focus, and the investigation of in place, exposed geological materials provides the greatest scientific insight and context for the formation and history of planetary materials and processes. The goal of this research program is to develop techniques for autonomous segmentation of images of rock outcrops. Recognition of the relationships between different geological units is the first step in mapping and interpreting a geological setting. Applications of automatic segmentation include instrument placement and targeting and data triage for downlink. Here, we report on the development of a new technique in which a photograph of a rock outcrop is processed by several elementary image processing techniques, generating a feature space which can be interrogated and classified. A distance metric learning technique (Multiclass Discriminant Analysis, or MDA) is tested as a means of finding the best numerical representation of the feature space. MDA produces a linear transformation that maximizes the separation between data points from different geological units. This ';training step' is completed on one or more images from a given locality. Then we apply the same transformation to improve the segmentation of new scenes containing similar materials to those used for training. The technique was tested using imagery from Mars analogue settings at the Cima volcanic flows in the Mojave Desert, California; impact breccias from the Sudbury impact structure in Ontario, Canada; and an outcrop showing embedded mineral veins in Gale Crater on Mars

  17. Geochemical evolution of tourmaline in the Darasun gold district, Transbaikal region, Russia: evidence from chemical and boron isotopic compositions

    Science.gov (United States)

    Baksheev, Ivan A.; Prokofiev, Vsevolod Yu.; Trumbull, Robert B.; Wiedenbeck, Michael; Yapaskurt, Vasilii O.

    2015-01-01

    The Darasun gold district, Transbaikal region, eastern Russia comprises three deposits: Teremkyn, Talatui, and Darasun, where gold-bearing quartz veins are hosted in metagabbro and granitoids. Tourmaline is a common gangue mineral in these deposits and a useful indicator of fluid source. The tourmaline compositions are oxy-dravite-povondraite, dravite, and schorl. We report here in situ B-isotope analyses by secondary ion mass spectrometry (SIMS) on tourmaline from veins in metagabbro and K-rich granodiorite, as well as from a breccia pipe at the margin of granodiorite porphyry. The B-isotope composition of tourmalines from the Darasun gold district as a whole covers a very wide range from -15.7 to +11.2 ‰, with distinctive differences among the three deposits. The δ11B values in the Teremkyn tourmalines are the most diverse, from -15.7 to +2.5 ‰. Tourmaline core compositions yield an inferred δ11B value of the initial fluid of ca. -12 ‰, suggesting granitic rocks as the B source, whereas the heavier rims and late-stage grains reflect Rayleigh fractionation. The δ11B values of tourmaline from Talatuiare -5.2 to -0.9 ‰. Taking into account fluid inclusion temperatures from vein quartz (ca. 400 °C), the inferred δ11B value of fluid is heavy (-2.5 to +2.2 ‰) suggesting a B source from the host metagabbro. At the Darasun deposit, tourmaline from the breccia pipe is isotopically uniform (δ11 B -6 to -5 ‰) and suggested to have precipitated from a 10B-depleted, residual fluid derived from granitic rocks. The Darasun vein-hosted tourmalines I and II (δ11B from -4.4 to +1.5 ‰) may have crystallized from strongly fractionated residual granitic fluid although mixing with heavy boron from the metagabbro rocks probably occurred as well; the boron isotopic composition of tourmaline III (-11.2 ‰) is attributed to a less-fractionated fluid, possibly a recharge from the same source.

  18. Monitoring and Characterizing the Geysering and Seismic Activity at the Lusi Mud Eruption Site, East Java, Indonesia

    Science.gov (United States)

    Karyono, Karyono; Obermann, Anne; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Abdurrokhim, Abdurrokhim; Masturyono, Masturyono; Hadi, Soffian

    2016-04-01

    The Lusi eruption began on May 29, 2006 in the northeast of Java Island, Indonesia, and to date is still active. Lusi is a newborn sedimentary-hosted hydrothermal system characterized by continuous expulsion of liquefied mud and breccias and geysering activity. Lusi is located upon the Watukosek fault system, a left lateral wrench system connecting the volcanic arc and the bakarc basin. This fault system is still periodically reactivated as shown by field data. In the framework of the Lusi Lab project (ERC grant n° 308126) we conducted several types of monitoring. Based on camera observations, we characterized the Lusi erupting activity by four main behaviors occurring cyclically: (1) Regular activity, which consists in the constant emission of water and mud breccias (i.e. viscous mud containing clay, silt, sand and clasts) associated with the constant expulsion of gas (mainly aqueous vapor with minor amounts of CO2 and CH4) (2) Geysering phase with intense bubbling, consisting in reduced vapor emission and more powerful bursting events that do not seem to have a regular pattern. (3) Geysering phase with intense vapor and degassing discharge and a typically dense plume that propagates up to 100 m height. (4) Quiescent phase marking the end of the geysering activity (and the observed cycle) with no gas emissions or bursts observed. To investigate the possible seismic activity beneath Lusi and the mechanisms controlling the Lusi pulsating behaviour, we deployed a network of 5 seismic stations and a HD camera around the Lusi crater. We characterize the observed types of seismic activity as tremor and volcano-tectonic events. Lusi tremor events occur in 5-10 Hz frequency band, while volcano tectonic events are abundant in the high frequencies range from 5 Hz until 25 Hz. We coupled the seismic monitoring with the images collected with the HD camera to study the correlation between the seismic tremor and the different phases of the geysering activity. Key words: Lusi

  19. Impact melt- and projectile-bearing ejecta at Barringer Crater, Arizona

    Science.gov (United States)

    Osinski, Gordon R.; Bunch, Ted E.; Flemming, Roberta L.; Buitenhuis, Eric; Wittke, James H.

    2015-12-01

    Our understanding of the impact cratering process continues to evolve and, even at well-known and well-studied structures, there is still much to be learned. Here, we present the results of a study on impact-generated melt phases within ejecta at Barringer Crater, Arizona, one of the first impact craters on Earth to be recognized and arguably the most famous. We report on previously unknown impact melt-bearing breccias that contain dispersed fragments of the projectile as well as impact glasses that contain a high proportion of projectile material - higher than any other glasses previously reported from this site. These glasses are distinctly different from so-called "melt beads" that are found as a lag deposit on the present-day erosion surface and that we also study. It is proposed that the melts in these impact breccias were derived from a more constrained sub-region of the melt zone that was very shallow and that also had a larger projectile contribution. In addition to low- and high-Fe melt beads documented previously, we document Ca-Mg-rich glasses and calcite globules within silicate glass that provide definitive evidence that carbonates underwent melting during the formation of Barringer Crater. We propose that the melting of dolomite produces Ca-Mg-rich melts from which calcite is the dominant liquidus phase. This explains the perhaps surprising finding that despite dolomite being the dominant rock type at many impact sites, including Barringer Crater, calcite is the dominant melt product. When taken together with our estimate for the amount of impact melt products dispersed on, and just below, the present-day erosional surface, it is clear that the amount of melt produced at Barringer Crater is higher than previously estimated and is more consistent with recent numerical modeling studies. This work adds to the growing recognition that sedimentary rocks melt during hypervelocity impact and do not just decompose and/or devolatilize as was previously thought

  20. Uranium

    International Nuclear Information System (INIS)

    concentration in peat bogs, deposits combined with marine phosphates, with coal and lignite, with black shales, with carbonate rocks, deposits in Precambrian quartz pebble conglomerates, basal-type deposits, deposits in sandstones (tabular, roll-type and tectono-lithologic deposits), breccia chimney filling deposits, deposits in metamorphic rocks, metasomatic deposits, deposits in intrusive rocks, deposits associated with hematite breccia complexes, deposits in granitic rocks, deposits in volcanic rocks, deposits in proterozoic discordances (Athabasca basin, Pine Creek geo-syncline); 4 - French uranium bearing areas and deposits: history of the French uranium mining industry, geological characteristics of French deposits (black shales, sandstones, granites), abroad success of French mining companies (Africa, North America, South America, Australia, Asia); 5 - exploration and exploitation; 6 - uranium economy: perspectives of uranium demand, present day production status, secondary resources, possible resources, market balances, prices and trends, future availability and nuclear perspectives. (J.S.)

  1. 宁芜北段火山岩型金矿类型及找矿方向%Types of volcanic rock gold deposits in northern Ningwu Basin and their prospecting direction

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    宁芜北段是长江中下游重要的火山岩型金矿成矿远景区。金矿类型繁多,主要有火山热液充填脉型金矿、陆相火山―沉积期后热液充填交代型金矿、蚀变破碎带型金矿、爆发角砾岩筒型金矿、铁帽型金矿以及伴生金。矿床主要受 NNE、NW 向区域性大断裂及其派生次级断裂控制,与安山质火山角砾岩、辉石闪长玢岩关系密切。梅山地区、铜井地区碱性火山岩内及外围、谷里地区及宁芜北段东部隆起带是今后的找矿方向。%Northern Ningwu Basin is an important volcanic rock type gold mineralization prospect area inside the regions along the middle and lower reaches of Yangtze River.Various types of gold deposits in this area include volcanic hydrothermal filling vein type gold deposit,continental volcano-post depositional hydrother-mal filling metasomatic gold deposit,alteration fracture zone type gold deposit,diatreme breccia pipe type gold deposit,gossan type gold deposit and associated gold deposit.The deposits are primarily controlled by NNE-and NW-trending regional major fractures and their derived subsidiary fractures,and they are closely related to andesitic volcanic breccia and pyroxene diorite porphyrite.The prospecting direction of this area are interior of the alkaline volcanic rocks and its peripheries in Meishan area and Tongjing area,as well as the uplift zone in Guli area and eastern part of northern Ningwu Basin.

  2. 准噶尔盆地春晖油田石炭系火山岩储层控制因素分析%Controlling factors of the Carboniferous volcanic reservoirs in the Chunhui Oil Field, Junggar Basin

    Institute of Scientific and Technical Information of China (English)

    董臣强

    2014-01-01

    春晖油田石炭系火山岩地层中,油气富集程度与储层发育程度呈正相关关系。研究认为,储层的发育与分布主要受岩相、岩性和构造运动的控制。岩相控制岩性,岩性控制储集空间组合类型,溢流相和火山沉积相围绕爆发相具有环带状分布特点,从火山角砾岩→玄武岩、安山岩→凝灰岩,储集性能逐渐变差;构造运动则控制裂缝的发育及溶蚀作用,断层周边微裂缝发育,沿着微裂缝则溶蚀作用增强,次生孔隙发育。%The Chunhui Oil Field in the Junggar Basin lies in the western part of the Halaalate Mountain tectonic zone, in which the Carboniferous volcanic strata consist dominantly of the volcanic rocks such as tuff, andesite, basalt and volcanic breccias. There is a positive correlation between the hydrocarbon enrichment and reservoir development in the Carboniferous volcanic reservoir rocks from the Chunhui Oil Field. The distribution and development of the volcanic reservoir rocks are primarily controlled by lithofacies, lithology and tectonism. On the whole, the lithofacies may exercise a major control on lithology of the volcanic reservoir rocks, which, in turn, may control the reservoir spaces types. The volcanic rocks in the Chunhui Oil Field exhibit a trend of the girdle pattern of lithofacies changes from the explosive facies through the effusive facies to the volcano-sedimentary facies. The reservoir capacity is gradually getting poor and poor from volcanic breccias to basalt and andesite and finally to tuff. The tectonism is also believed to be a major control on the fissure development and dissolution. The structural stress may give rise to the formation of the cracks or fissures in the brittle rocks, which may greatly improve the reservoir spaces of the Carboniferous volcanic reservoir rocks in the study area.

  3. A long-term change of the AR/KR/XE fractionation in the solar corpuscular radiation

    Science.gov (United States)

    Wieler, R.; Baur, H.; Signer, P.

    1993-01-01

    Solar noble gases in an ilmenite separate from breccia 79035 (antiquity greater than 1 Ga) were analyzed by closed system stepped etching (CSSE). All five gases show the familiar two-component structure: first solar-wind (SW) gases are released, followed by gases from solar energetic particles (SEP). Element patterns in 79035 are similar to those of 71501 ilmenite. SW-He-Ne were partly lost, but SEP-He-Ne-Ar are retained (nearly) unfractionated. Constant Ar/Kr/Xe ratios indicate that ilmenites contain an unfractionated sample of the heavy SW-SEP noble gases. Ar/Kr/Xe ratios in the solar corpuscular radiation are, however, different from 'solar system' values, whereby the Kr/Xe difference in 79035 is about twice as large as in 71501. We propose that Xe is less fractionated than Kr and Ar, though its first ionization potential (FIP) is higher than the 'cutoff' at approximately 11.5 eV, above which all elements in SEP are usually assumed to be depleted by a roughly constant factor. SW-Ne may be isotopically slightly heavier in the ancient SW trapped by 79035, as proposed earlier. In this work we extend our previous CSSE studies of solar noble gases including Kr and Xe to a lunar sample irradiated at least 1 Ga ago (breccia 79035, ilmenite separate, 42-64 microns). This sample was particularly gently etched in the first steps. Surprisingly, the first three steps, each releasing less than or equal to 0.5% of the total 36-Ar, showed an SEP-like trapped component plus relatively large concentrations of cosmogenic gases. Steps 4ff contain much less cosmogenic and more solar gas with a SW-like isotope pattern. Thus, a very minor easily etchable phase that has completely lost its SW-gases must be responsible for steps 1-3. We will not discuss these steps here and refer to the actual step 4 as the 'initial' etching step.

  4. Evolution of fluid-rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B

    Science.gov (United States)

    Fowler, Andrew P. G.; Zierenberg, Robert A.; Schiffman, Peter; Marks, Naomi; Friðleifsson, Guðmundur Ómar

    2015-09-01

    We describe the lithology and present spatially resolved geochemical analyses of samples from the hydrothermally altered Iceland Deep Drilling Project (IDDP) drill core RN-17B. The 9.3 m long RN-17B core was collected from the seawater-dominated Reykjanes geothermal system, located on the Reykjanes Peninsula, Iceland. The nature of fluids and the location of the Reykjanes geothermal system make it a useful analog for seafloor hydrothermal processes, although there are important differences. The recovery of drill core from the Reykjanes geothermal system, as opposed to drill cuttings, has provided the opportunity to investigate evolving geothermal conditions by utilizing in-situ geochemical techniques in the context of observed paragenetic and spatial relationships of alteration minerals. The RN-17B core was returned from a vertical depth of ~ 2560 m and an in-situ temperature of ~ 345 °C. The primary lithologies are basaltic in composition and include hyaloclastite breccia, fine-grained volcanic sandstone, lithic breccia, and crystalline basalt. Primary igneous phases have been entirely pseudomorphed by calcic plagioclase + magnesium hornblende + chlorite + titanite + albitized plagioclase + vein epidote and sulfides. Despite the extensive hydrothermal metasomatism, original textures including hyaloclastite glass shards, lithic clasts, chilled margins, and shell-fragment molds are superbly preserved. Multi-collector LA-ICP-MS strontium isotope ratio (87Sr/86Sr) measurements of vein epidote from the core are consistent with seawater as the dominant recharge fluid. Epidote-hosted fluid inclusion homogenization temperature and freezing point depression measurements suggest that the RN-17B core records cooling through the two-phase boundary for seawater over time to current in-situ measured temperatures. Electron microprobe analyses of hydrothermal hornblende and hydrothermal plagioclase confirm that while alteration is of amphibolite-grade, it is in disequilibrium

  5. Localized and Areally Extensive Alterations in Marathon Valley, Endeavour Crater Rim, Mars

    Science.gov (United States)

    Mittlefehldt, David W.; Gellert, Ralf; Van Bommel, Scott; Arvidson, Raymond E.; Clark, Benton C.; Cohen, Barbara A.; Farrand, William H.; Ming, Douglas W.; Schroeder, Christian; Yen, Albert S.; Jolliff, Bradley L.

    2016-01-01

    Mars Exploration Rover Opportunity is exploring the rim of 22 km diameter, Noachian-aged Endeavour crater. Marathon Valley cuts through the central region of the western rim providing a window into the local lower rim stratigraphic record. Spectra from the Compact Reconnaissance Imaging Spectrometer for Mars show evidence for the occurrence of Fe-Mg smectite in this valley, indicating areally extensive and distinct lithologic units and/or styles of aqueous alteration. The Alpha Particle X-ray Spectrometer has determined the compositions of 59 outcrop targets on untreated, brushed and abraded surfaces. Rocks in the Marathon Valley region are soft breccias composed of mm- to cm-sized darker clasts set in a lighter-toned, finegrained matrix. They are basaltic in non-volatile-element composition and compositionally similar to breccias investigated elsewhere on the rim. Alteration styles recorded in the rocks include: (1) Enrichments in Si, Al, Ti and Cr in more reddish-colored rock, consistent with leaching of more soluble cations and/or precipitation of Si +/- Al, Ti, Cr from fluids. Coprecipitation of Ge-rich phases with Si occurred in the western area only; high water:rock is indicated. Pancam multispectral observations indicate higher nanophase ferric oxide contents, but the rocks have lower Fe contents. The highly localized nature of the red zones indicate they cannot be the source of the widespread smectite signature observed from orbit. (2) Outcrops separated by approximately 65 m show common compositional changes between brushed and abraded (approximately 1 mm deep) targets: increases in S and Mg; decreases in Al, Cl and Ca. These changes are likely due to relatively recent, surface-related alteration of valley rocks and formation of surface coatings under low water:rock. (3) One target, from the center of a region of strong CRISM smectite signature, shows modest differences in composition (higher Si, K; lower Mn) compared to most Marathon Valley rocks, while

  6. Structure and evolution of Middle Permian palaeo-seamounts in Bayan Har and its adjacent area

    Institute of Scientific and Technical Information of China (English)

    WANG Yongbiao

    2005-01-01

    Middle Permian palaeo-seamounts in the area of Bayan Har are generally composed of volcanic basement and carbonate cap. Basaltic lava, volcanic breecia and polymictic breccia can be identified as the main kinds of rock in the basement of palaeo-seamounts. Massive bioclastic limestone and reef framestone formed the carbonate cap of the palaeo-sea- mounts. The contact relationship between carbonate cap and volcanic basement is a kind of conformity or depositional unconformity. Study of the structure and petrology of palaeo-sea- mounts suggests that the evolution history of the palaeo-seamounts in this area can be divided into five stages at least. They are the origin of the first volcanic basement, the formation of the first carbonate cap, the breaking of the first carbonate cap by renewed volcanism, the deposition of red calcareous mudstone and the rebuilding of the second carbonate cap at last. In one of the palaeo-seamounts, volcanic activation took place even after the reconstruction of the second carbonate cap. Lots of fusulinid fossils, such as Neoschwagerina craticulifera Schwager, Schwagerina sp. and Verbeekina sp., were found both in the carbonate cap and volcanic basement, showing that the palaeo-seamounts were originated and developed within the Maokou stage of Middle Permian.

  7. IODP Expedition 331: Strong and Expansive Subseafloor Hydrothermal Activities in the Okinawa Trough

    Directory of Open Access Journals (Sweden)

    the IODP Expedition 331 Scientists

    2012-04-01

    Full Text Available Integrated Ocean Drilling Program (IODP Expedition 331 drilled into the Iheya North hydrothermal system in the middle Okinawa Trough in order to investigate active subseafloor microbial ecosystems and their physical and chemical settings. We drilled five sites during Expedition 331 using special guide bases at three holes for reentry, casing, and capping, including installation of a steel mesh platformwith valve controls for postcruise sampling of fluids. At Site C0016, drilling at the base of the North Big Chimney (NBCmound yielded low recovery, but core included the first Kuroko-type black ore ever recovered from the modern subseafloor. The other four sites yielded interbedded hemipelagic and strongly pumiceous volcaniclastic sediment, along with volcanogenic breccias that are variably hydrothermally altered and mineralized. At most sites, analyses of interstitial water and headspace gas yielded complex patterns withdepth and lateral distance of only a few meters. Documented processes included formation of brines and vapor-rich fluids by phase separation and segregation, uptake of Mg and Na by alteration minerals in exchange for Ca, leaching of K at high temperature and uptake at low temperature, anhydrite precipitation, potential microbial oxidation of organic matter and anaerobic oxidation of methane utilizing sulfate, and methanogenesis. Shipboard analyses have found evidence for microbial activity in sediments within the upper 10–30 m below seafloor (mbsf where temperatures were relativelylow, but little evidence in the deeper hydrothermally altered zones and hydrothermal fluid regime.

  8. U-Pb Ages of Lunar Apatites

    Science.gov (United States)

    Vaughan, J.; Nemchin, A. A.; Pidgeon, R. T.; Meyer, Charles

    2006-01-01

    Apatite is one of the minerals that is rarely utilized in U-Pb geochronology, compared to some other U-rich accessory phases. Relatively low U concentration, commonly high proportion of common Pb and low closure temperature of U-Pb system of apatite inhibit its application as geochronological tool when other minerals such as zircon are widely available. However, zircon appear to be restricted to certain type of lunar rocks, carrying so called KREEP signature, whereas apatite (and whitlockite) is a common accessory mineral in the lunar samples. Therefore, utilizing apatite for lunar chronology may increase the pool of rocks that are available for U-Pb dating. The low stability of U-Pb systematics of apatite may also result in the resetting of the system during meteoritic bombardment, in which case apatite may provide an additional tool for the study of the impact history of the Moon. In order to investigate these possibilities, we have analysed apatites and zircons from two breccia samples collected during the Apollo 14 mission. Both samples were collected within the Fra Mauro formation, which is interpreted as a material ejected during the impact that formed the Imbrium Basin.

  9. Origin of zoning within dedolomite and calcitized gypsum of the Mississippian Arroyo Penasco Group

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, D.S.

    1985-01-01

    The Mississippian Arroyo Penasco Group carbonates are the oldest Paleozoic rocks present in north-central New Mexico. These supratidal to shallow,subtidal sediments exhibit complex diagenetic fabrics produced by periods of pre-Pennsylvanian subaerial exposure. Both extensive recrystallization of the Espiritu Santo carbonates and brecciation of the overlying Macho Member of the Tererro Formation resulted from an extended period of Mississippian subaerial exposure of broad, low-relief tidal flats. Cathodoluminescent petrography indicates that the recrystallized limestones consist of calcite pseudomorphs of dolomite and gypsum. Dedolomite and calcitized gypsum crystals, with /sup 13/C//sup 12/C ratios of -2 to +1.5% PDB, range from highly zoned to uniformly luminescent. Electron microprobe analyses reveals variable Mn and Fe contents across the pseudomorphs which are responsible for differences in observed luminosity. These features are interpreted to reflect a period of subaerial exposure after deposition of Macho Member sediments, which caused dissolution of gypsum and dolomite by sulfate and Mg depleted meteoric fluids and produced the collapse breccia. Preservation of zoning within some pseudomorphs required simultaneous dissolution of gypsum and dolomite and precipitation of calcite. C-isotope data indicates a meteoric to mixed phreatic origin for pore fluids which precipitated calcite; repetitive zoning within dolomite and gypsum pseudomorphs is indicative of interactions between marine and meteoric phreatic fluids in the intertidal environment.

  10. Giant fields in the southeast of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Acevedo, J.S.; Dautt, O.M.

    1980-01-01

    From a geologic and petroliferous point of view, the southeast zone coastal plain of Mexico has been divided into the saline basin of the Isthmus, the Macuspana Basin, and the Chiapas-Tabasco Mesozoic area. In the first 2 basins, there are giant producer fields from tertiary sands. In the saline basin of the Isthmus, production comes from structural traps associated with saline domes. In the Macuspana Basin, production comes from anticlines. The Chiapas-Tabasco Mesozoic area produces from Jurassic, Lower, Middle and Upper Cretaceous dolomitic limestones and dolomites associated with anticlines. The marine platform of Campeche produces from Jurassic and Cretaceous dolomites and lower Paleocene dolomitic Breccias associated with anticlines having numerous normal and thrust faults. A brief description is given of 5 giant fields in the saline basin of the Isthmus and 3 fields in the Macuspana Basin; a more detailed description is given of 4 giant fields in the Chiapas-Tabasco area and 2 in the sound of Campeche.

  11. Geochemical modelling of the unconformity related uranium mineralisation - A case study from Baskati area, Madhya Pradesh, India

    International Nuclear Information System (INIS)

    Full text: Signature of concealed unconformity related uranium mineralization at the contact of Chhotanagpur Granite Gneissic Complex (CGGC)/Mahakoshal, (Archaean/ lower Proterozoic age) and lower Vindhyan Semri sequence (middle to upper Proterozoic age) has come to light at Baskati in Vindhyan - Mahakoshal Basin following a multipronged exploratory effort. This involved airborne gamma-ray spectrometry (AGRS), remote sensing data interpretation, radio geochemical image analysis, regional geophysical gravity survey, aeroradiometric survey, radiometric survey, geological cum structural mapping and systematic close grid lithogeochemical sampling. Based on satellite and aeromagnetic data interpretation the CGGC/Mahakoshal - Vindhyan unconformity contact has been identified as target area. This contact runs for more than 100 km length. The area has been further narrowed down to 60 sq km based on integration of satellite and AGRS data. Detailed radiometric checking and geological mapping along the potential blocks demarcated by above mentioned surveys resulted in further narrowing down of target area to 6 sq km around Baskati - Paniha sector. Mahakoshal-Vindhyan basin has undergone various stages of magmatism and deformation from Archaean to post Vindhyan times leading to reactivation of basin marginal faults and development of pervasive fracture system cutting through basement and cover sequence rocks. Anomalous syngenetic uranium in the form of protore is available in different rocks for mobilization in the successive stages of deformation. Uranium mineralisation is associated with breccia zones developed along major faults close to unconformity contact. These breccias are probably developed by the process of tufficitic brecciation during younger magmatic activity in the basin. Uranium enriched along the Precambrian palaeosurface which was subsequently covered by Vindhyans would have been prone to mobilisation at the time of pre Vindhyan rifting and post Vindhyan

  12. Characterizing a fractured aquifer in Mexico using geological attributes related to open-pit groundwater

    Science.gov (United States)

    Herrera, Enrique; Garfias, Jaime

    2013-09-01

    A multivariable analysis of the Rock Quality Designation ( RQD) and its relation with the hydraulic conductivity of 17 dewatering wells in an open-pit mine (central Mexico) is presented as a tool for groundwater exploration in fractured aquifers. A solid model was constructed with the RQD data using three sizes for each grid cell and four interpolation methods. The inverse-distance method with a small grid gives the best results. The resulting RQD solid model was used to locate 22 pilot holes, on which an air-lift test was performed as a qualitative assessment of their usefulness. The results showed a lower water production (1.8 l/s) in shale that has low alteration, whereas in highly altered shale, breccias, and intrusive rock, the flow rate was 3.9 l/s. This implies an important relationship between the pilot-hole performance, the lithology, and the rock alteration, but it was also found that some fractures or faults, which cannot be detected clearly by the RQD, play an important role in the hydrodynamics of the aquifer. In conclusion, it is necessary to consider all available factors that can help to identify the hydrodynamic behavior of the aquifer because using only RQD data can lead to errors in prospecting for groundwater.

  13. Crystal Stratigraphy of Two Basalts from Apollo 16: Unique Crystallization of Picritic Basalt 606063,10-16 and Very-Low-Titanium Basalt 65703,9-13

    Science.gov (United States)

    Donohue, P. H.; Neal, C. R.; Stevens, R. E.; Zeigler, R. A.

    2014-01-01

    A geochemical survey of Apollo 16 regolith fragments found five basaltic samples from among hundreds of 2-4 mm regolith fragments of the Apollo 16 site. These included a high-Ti vitrophyric basalt (60603,10-16) and one very-low-titanium (VLT) crystalline basalt (65703,9-13). Apollo 16 was the only highlands sample return mission distant from the maria (approx. 200 km). Identification of basaltic samples at the site not from the ancient regolith breccia indicates input of material via lateral transport by post-basin impacts. The presence of basaltic rocklets and glass at the site is not unprecedented and is required to satisfy mass-balance constraints of regolith compositions. However, preliminary characterization of olivine and plagioclase crystal size distributions indicated the sample textures were distinct from other known mare basalts, and instead had affinities to impact melt textures. Impact melt textures can appear qualitatively similar to pristine basalts, and quantitative analysis is required to distinguish between the two in thin section. The crystal stratigraphy method is a powerful tool in studying of igneous systems, utilizing geochemical analyses across minerals and textural analyses of phases. In particular, trace element signatures can aid in determining the ultimate origin of these samples and variations document subtle changes occurring during their petrogenesis.

  14. A Comprehensive Investigation of an Offshore Active Fault in the Western Sagami Bay, Central Japan

    Institute of Scientific and Technical Information of China (English)

    吴时国; 坂本泉; 徐纪人; 黄孝健

    2002-01-01

    Offshore active faults, especially those in the deep sea, are very difficult to study because of the waterand sedimentary cover. To characterize the nature and geometry of offshore active faults, a combination of methods mustbe employed. Generally, seismic profiling is used to map these faults, but often only fault-related folds rather thanfracture planes are imaged. Multi-beam swath bathymetry provides information on the structure and growth history of afault because movements of an active fault are reflected in the bottom morphology. Submersible and deep-tow surveysallow direct observations of deformations on the seafloor (including fracture zones and microstructures). In the deep sea,linearly aligned cold seep communities provide indirect evidence for active faults and the spatial migration of theiractivities.The Western Sagami Bay fault (WSBF) in the western Sagami Bay off central Japan is an active fault that has beenstudied in detail using the above methods. The bottom morphology, fractured breccias directly observed andphotographed, seismic profiles, as well as distribution and migration of cold seep communities provide evidence for thenature and geometry of the fault. Focal mechanism solutions of selected earthquakes in the western Sagami Bay duringthe period from 1900 to 1995 show that the maximum compression trends NW-SE and the minimum stress axis strikesNE-SW, a stress pattern indicating a left-lateral strike-slip fault.

  15. High-resolution U-series dates from the Sima de los Huesos hominids yields 600 +∞-66: implications for the evolution of the early Neanderthal lineage

    Science.gov (United States)

    Bischoff, James L.; Williams, Ross W.; Rosenbauer, Robert J.; Aramburu, Arantza; Arsuaga, Juan Luis; Garcia, Nuria; Cuenca-Bescos, Gloria

    2007-01-01

    The Sima de los Huesos site of the Atapuerca complex near Burgos, Spain contains the skeletal remains of at least 28 individuals in a mud-breccia underlying an accumulation of the Middle Pleistocene cave bear (Ursus deningeri). We report here on new high-precision dates on the recently discovered speleothem SRA-3 overlaying human bones within the Sima de los Huesos. Earlier analyses of this speleothem by TIMS (thermal-ionization mass-spectrometry) showed the lower part to be indistinguishable from internal isotopic equilibrium at the precision of the TIMS instrumentation used, yielding minimum age of 350 kyr (kyr = 103 yr before present). Reanalysis of six samples of SRA-3 by inductively-coupled plasma-multicollector mass-spectrometry (ICP-MS) produced high-precision analytical results allowing calculation of finite dates. The new dates cluster around 600 kyr. A conservative conclusion takes the lower error limit ages as the minimum age of the speleothem, or 530 kyr. This places the SH hominids at the very beginnings of the Neandertal evolutionary lineage.

  16. Summary of the geology of the northern part of the Sierra Cuchillo, Socorroand Sierra Counties, southwestern New Mexico

    Science.gov (United States)

    Maldonado, Florian

    2012-01-01

    The northern part of the Sierra Cuchillo is located within the northeastern part of the Mogollon-Datil volcanic field west of the Rio Grande rift in the Basin and Range Province, approximately 50 km northwest of Truth or Consequences in south-central New Mexico. The Sierra Cuchillo is a north-south, elongated horst block composed of Tertiary volcanic and intrusive rocks, sparse outcrops of Lower Permian and Upper Cretaceous rocks, and sediments of the Tertiary-Quaternary Santa Fe Group. The horst is composed mainly of a basal volcanic rock sequence of andesite-latite lava flows and mud-flow breccias with a 40Ar/39Ar isotopic age of about 38 Ma. The sequence is locally intruded by numerous dikes and plugs that range in composition from basaltic andesite through rhyolite and granite. The andesite-latite sequence is overlain by ash-flow tuffs and a complex of rhyolitic lava flows and domes. Some of these units are locally derived and some are outflow sheets derived from calderas in the San Mateo Mountains, northeast of the study area. These locally derived units and outflow sheets range in age from 28 to 24 Ma.

  17. Uranium deposits in the Beaverlodge area, northern Saskatchewan: their relationship to the Martin Group (Proterozoic) and the underlying basement

    International Nuclear Information System (INIS)

    The rocks of the Martin Group crop out in an area 60 km by 50 km north of Lake Athabasca near Uranium City, northern Saskatchewan. This area has numerous uranium showings within a few kilometres of the unconformity below the Martin Group. Mineralization occurs in fault zones, in basement rocks and in sedimentary and volcanic rocks of the Martin Group. Martin Group sediments accumulated in alluvial fans, braided streams, and ephemeral lakes. The thickest sequence (8 km to 10 km) is preserved in the Beaverlodge area, near Uranium City. The style of sedimentation changed through time as the basin evolved from deposition of conglomeratic detritus along fault scarps to the accumulation of silt in ephemeral lakes. The uneven nature of the sub-Martin unconformity surface, the lithotype of the lowermost conglomerates and breccias (Beaverlodge Formation), and the shape of the basin fill indicate deposition in fault-controlled basins. The earliest economic uranium mineralization in the rocks of the Martin Group was epigenetic. The mineralization was coeval with that in basement rocks. Economic mineralization in basement rocks and in the lowermost formation of the Martin Group is close to the unconformity. Epigenetic uranium mineralization thus appears to have resulted from processes that were related, in time and space, to either the formation of the unconformity or the deposition of the Martin Group or both. (author). 29 refs, 5 figs

  18. Gunung Api purba Watuadeg: Sumber erupsi dan posisi stratigrafi

    Directory of Open Access Journals (Sweden)

    Sutikno Bronto

    2014-06-01

    Full Text Available http://dx.doi.org/10.17014/ijog.vol3no3.20081Pillow lava flows of pyroxene basalt containing 50 wt.% SiO are exposed at Opak River, west of Watuadeg Village, Sleman - Yogyakarta. The length of flow structures is between 2 – 10 m, with diameter of 0.5 – 1.0 m and it has a glassy skin at the surface body. Flow directions vary from N70E in the northern side, through N 120E in the middle to N 150E in the southern side. About 150 m away from the river to the west, there is a small hill about 15 m high, that has a similar composition with the pillow lavas. Both lava flows and the small hill are composed of pyroxene basalt, dark grey in color, hypocrystalline vitrophyre to porphyritic texture, with fine-grained phenocrysts of pyroxene (10 % and plagioclase (25 % set in glassy groundmass. These data indicate that the small hill was the eruption source of the basaltic pillow lavas. The lavas are overlain by pumice-rich volcaniclastic rocks, composed of tuff, lapillistones and pumice breccias, that are known as the Semilir Formation. Near the contact with lavas, the volcaniclastic rocks contain some fragments of pyroxene basalt, similar composition with the pillow lavas. This fact, together with analyses of petrology, volcanology, and radiometric dating show that the basaltic pillow lavas are unconformably overlain by the Semilir Formation.  

  19. Unconformity-related uranium deposits, Athabasca area, Saskatchewan, and East Alligator Rivers area, Northern Territory, Australia

    International Nuclear Information System (INIS)

    Most unconformity-type uranium deposits in Saskatchewan occur within a few tens of metres above and/or below the basal unconformity of the 1.45 b.y. Athabasca Sandstone. Graphitic basement rocks coincident with post-Athabasca faulting or brecciation at or near the unconformity are important in localizing uranium deposits which form as tabular, ribbon-like bodies with grades averaging over 2 percent uranium and containing up to 50,000 tonnes U3O8. Some of these deposits have similar contents of nickel and arsenic. In the genetic model used to explain these deposits, traces of uranium were leached from the sandstone and basement rocks by oxidized formation waters. A thick clay regolith absorbed uranium from the solution, and the fixed uranium was reduced through an indirect reaction with graphite. The clay mineral surfaces were thus continuously cleared to allow further adsorption. Fluid convection was induced by topographic relief and/or crustal heating from radioactive decay, and would continue uranium deposition until all permeability was plugged by minerals. The East Alligator Rivers uranium deposits in Northern Territory, Australia occur within Middle Proterozoic quartz-chlorite and quartz-muscovite schists overlain by sandstone. Highest grades occur in silicified breccias where carbonate beds were leached out. Mineralization ages are both pre- and post-Kombolgie Sandstone, but, to date, no significant uranium mineralization has been found in the sandstone. There are many similarities with Saskatchewan deposits, but also important differences. (auth)

  20. Petrografía y geoquímica preliminar de los basaltos cretácicos de la sierra de Las Quijadas y cerrillada de Las Cabras, provincia de San Luis, Argentina

    Directory of Open Access Journals (Sweden)

    Martínez Amancay N.

    2011-11-01

    Full Text Available Preliminary petrography and geochemistry of the Cretacic basalts of the Sierra de Las Quijadasand Cerrillada de Las Cabras, San Luis province, Argentina. We present preliminary results of the petrologyand geochemistry of Cretaceous basalts exposed in the anticlines of the sierra of Las Quijadas and cerrillada ofLas Cabras. In the mountainous western of San Luis crop out at least two depositional sequences which togetherexceed the 1500 m thick and consists mainly of clastic sedimentary sequences typical continental red beds belongingto the Giant Group and Lagarcito Formation. Within this group, recognizes two types of basalt events, representedby lava flows and dykes. The lava flows were described in the northeastern sector of the anticline, in a landscapeof gentle hills. The dykes were found on the western flank of the anticline, northern sector of that mountain.Basalt lava flows have porphyritic texture with phenocrystals show idiomorphic olivine with clinopyroxene,amphibole and plagioclase, while the basaltic dykes show olivine in porphyritic texture embedded in a plagioclasepaste without orientation, amphibole and apatite needles. The basalts of the cerrillada de Las Cabras presented asa volcanic breccia associated with basaltic bombs. They have phenocrystals of olivine and clinopyroxene in pastewith plagioclase oriented. The basalts are classified as alkali basalts and related to intraplate basalts. When analyzingrare earth elements chondrite normalized according to Nakamura’s design are observed with a steep negative slopefor the heavy rare earth elements, a design that is similar to that found in alkaline basalts from the Sierra Chica deCórdoba.