Sample records for breccia

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

    Călin G. Tămas


    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

    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

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


    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

    Frenzel, Max; Woodcock, Nigel H.


    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

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


    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

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


    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

    Mueller-Mohr, V.


    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

    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

    Hunt, Julie; Baker, Tim; Thorkelson, Derek


    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

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


    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

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


    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

    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

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


    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

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


    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

    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

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


    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

    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

    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

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


    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

    Sair Kahraman; Michael Alber


    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

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


    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

    Susanna Nanni


    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

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


    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

    Călin G. Tămas


    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

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


    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

    Haskin, Larry A.; Lindstrom, David J.


    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

    Susanna Nanni


    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

    Phisit Limtrakun


    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

    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

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


    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

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


    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

    Nelson Barros-Galvis


    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

    Winzer, S. R.


    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

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


    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

    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

    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

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


    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

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


    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

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


    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

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


    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

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


    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

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


    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

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


    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

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


    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

    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)


    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

    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


    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

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


    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.

    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


    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

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


    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

    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

    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

    Cox, Stephen


    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

    Pietrek, Alexa; Kenkmann, Thomas


    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

    Giulia De Sarlo


    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

    Giulia De Sarlo


    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

    Kirsten, T.; Horn, P.


    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

    Slamet Widodo; Iman Satyarno; Sri Tudjono


    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...



    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

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


    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

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


    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

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


    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

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


    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

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


    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

    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

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


    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

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


    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

    Rebolledo-Vieyra, Mario; Urrutia-Fucugauchi, Jaime


    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

    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.


    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

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


    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

    Rubin, Alan E.


    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

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


    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

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


    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

    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)

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


    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

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


    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

    Ricoy, V.


    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

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


    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

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


    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

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


    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

    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).

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


    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

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


    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)

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


    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



    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?

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


    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

    Delaney, Paul T.; Pollard, David D.


    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

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


    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

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


    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)

    Ji, Shaocheng


    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

    刘满年; 杨登美; 刘新会; 崔龙; 向红林; 王淑娟; 高选顿


      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

    Armando C. Massabie


    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



    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

    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


    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

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


    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

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


    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

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


    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


    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

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


    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

    Rubin, Alan E.; Jones, Rhian H.


    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

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


    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

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


    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

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


    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

    Harries, Dennis; Zolensky, Michael E.


    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

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


    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

    Dalrymple, G. Brent; Ryder, Graham


    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

    Torres Pérez-Hidalgo, Trinidad José de


    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

    Flude, Stephanie; Storey, Michael


    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

    Thiéblemont, Denis


    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

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


    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

    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)

    Tari, V.; Mrinjek, E.


    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

    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

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


    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

    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

    范宏瑞; 胡芳芳; 杨奎锋; 金成伟


    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

    Thiéblemont, Denis


    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

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


    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

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


    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

    Ridley, W. I.


    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

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


    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

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


    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

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


    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

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


    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

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


    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

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


    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

    Sahoui, R.; Belhai, D.


    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

    Valter, A.


    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)

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


    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

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


    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

    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.


    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

    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

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


    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)

    Lee, Jonathan R.


    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

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


    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

    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


    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

    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

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


    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

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


    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)

    Kopylova, Maya; Bruce, Loryn; Ryder, John


    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.


    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

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


    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

    Stevo Dozet


    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.

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


    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)

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


    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

    Johnson, Ronald C.; Brownfield, Michael E.


    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

    Kato, Naoki; Hirono, Tetsuro


    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

    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

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


    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

    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 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

    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

    Sauro U.


    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

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


    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

    Thiéblemont, Denis


    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

    Thiéblemont, Denis


    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

    McCusker, Jim; Reed, Christopher


    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

    Nordyke, M. D.


    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

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


    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)

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


    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

    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

    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

    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

    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

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


    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

    Martel, L. M. V.


    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

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


    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

    Robledo Ardila Pedro A.


    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

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


    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

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


    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

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


    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

    Schoneveld, Louise; Spandler, Carl; Hussey, Kelvin


    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

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


    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

    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

    S. Okamoto


    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

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


    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

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


    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

    Levey, Schon S.


    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

    Tatsumoto, M.; Rosholt, J.N.


    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

    Alexander Lačný


    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)

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


    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

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


    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

    Uhlmann, D. R.


    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

    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?

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


    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

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


    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

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


    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

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

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


    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...




    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

    Fadila Alligui; Abdelhak Boutaleb


    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

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


    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

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


    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

    Heymann, D.


    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

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


    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?

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


    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.

    Gaal Ludovit


    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

    Cooper A.H.


    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?

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


    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

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


    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

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


    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

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


    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.

    Kuman, K; Clarke, R J


    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

    Carrasco-Velázquez B.E.


    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

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


    [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

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


    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

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


    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

    Rubin, Charles M.; Saleeby, Jason B.


    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

    Maryam Abdi; Mohammad Hassan Karimpour


    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.

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


    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

    Hill Gendoet Hartono


    Full Text Available, 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

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


    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



    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

    Korotev, R. L.


    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.


    Slobodan Šestanović


    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

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


    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

    Basu, A.; Mckay, D. S.


    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

    Rajlich, Petr


    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

    Luciano Alves


    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


    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

    Kakaba Madi


    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

    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.

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


    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

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


    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

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


    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

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


    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.

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


    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)

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


    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

    White, Matthew J.; McPhie, Jocelyn


    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

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


    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.

    Martini Jacques E. J.


    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

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


    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

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


    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

    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

    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

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


    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

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


    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

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


    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

    Hips, Kinga; Haas, János; Győri, Orsolya


    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

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


    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

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


    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

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


    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

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


    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

    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


    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

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


    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

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


    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

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


    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

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


    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

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


    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

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


    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

    Mauro Caffau


    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

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


    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

    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