WorldWideScience

Sample records for ankerite

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

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

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

  2. The CO2 consumption potential during gray shale weathering: Insights from the evolution of carbon isotopes in the Susquehanna Shale Hills critical zone observatory

    Science.gov (United States)

    Jin, Lixin; Ogrinc, Nives; Yesavage, Tiffany; Hasenmueller, Elizabeth A.; Ma, Lin; Sullivan, Pamela L.; Kaye, Jason; Duffy, Christopher; Brantley, Susan L.

    2014-10-01

    Shale covers about 25% of the land surface, and is therefore an important rock type that consumes CO2 during weathering. We evaluated the potential of gray shale to take up CO2 from the atmosphere by investigating the evolution of dissolved inorganic carbon (DIC) concentrations and its carbon isotopic ratio (δ13CDIC) along water flow paths in a well-characterized critical zone observatory (Susquehanna Shale Hills catchment). In this catchment, chemical weathering in shallow soils is dominated by clay transformation as no carbonates are present, and soil pore waters are characterized by low DIC and pH. In shallow soil porewaters, the DIC, dominated by dissolved CO2, is in chemical and isotopic equilibrium with CO2 in the soil atmosphere where pCO2 varies seasonally to as high as 40 times that of the atmosphere. The degradation of ancient organic matter is negligible in contributing to soil CO2. The chemistry of groundwater varies along different flowpaths as soil pore water recharges to the water table and then dissolves ankerite or secondary calcite under the valley floor. Weathering of carbonate leads to much higher concentrations of DIC (∼2500 μmol/L) and divalent cations (Ca2+ and Mg2+) in groundwaters than soil waters. The depth to the ankerite weathering front is hypothesized to be roughly coincident with the water table but it varies due to heterogeneities in the protolith composition. Groundwater chemistry therefore shows different saturation indices with respect to ankerite depending upon location along the valley. The δ13CDIC values of these groundwaters document mixing between the ankerite and soil CO2. The major element concentrations, DIC, and δ13CDIC in the first-order stream incising the valley of the catchment are derived from groundwater and soil waters in proportions that vary both spatially and temporally. The CO2 degassed slightly in the stream but little evidence of C isotopic equilibration with the atmosphere is observed, due to the short

  3. Calibration of carbonate composition using micro-Raman analysis: application to planetary surface exploration.

    Science.gov (United States)

    Rividi, Nicolas; van Zuilen, Mark; Philippot, Pascal; Ménez, Bénédicte; Godard, Gaston; Poidatz, Emmanuel

    2010-04-01

    Stromatolite structures in Early Archean carbonate deposits form an important clue for the existence of life in the earliest part of Earth's history. Since Mars is thought to have had similar environmental conditions early in its history, the question arises as to whether such stromatolite structures also evolved there. Here, we explore the capability of Raman spectroscopy to make semiquantitative estimates of solid solutions in the Ca-Mg-Fe(+Mn) carbonate system, and we assess its use as a rover-based technique for stromatolite characterization during future Mars missions. Raman microspectroscopy analysis was performed on a set of carbonate standards (calcite, ankerite, dolomite, siderite, and magnesite) of known composition. We show that Raman band shifts of siderite-magnesite and ankerite-dolomite solid solutions display a well-defined positive correlation (r(2) > 0.9) with the Mg# = 100 x Mg/(Mg + Fe + Mn + Ca) of the carbonate analyzed. Raman shifts calibrated as a function of Mg# were used in turn to evaluate the chemical composition of carbonates. Raman analysis of a suite of carbonates (siderite, sidero-magnesite, ankerite, and dolomite) of hydrothermal and sedimentary origin from the ca. 3.2 Ga old Barite Syncline, Barberton greenstone belt, South Africa, and from the ca. 3.5 Ga old Dresser Formation, Pilbara Craton, Western Australia, show good compositional agreement with electron microprobe analyses. These results indicate that Raman spectroscopy can provide direct information on the composition and structure of carbonates on planetary surfaces.

  4. Exhalites Associated with Pb-Zn Mineralization in Devonian System and Their Prospecting Implications,Qinling,China

    Institute of Scientific and Technical Information of China (English)

    1991-01-01

    The exhalation origin of the ankerite-siliceous rocks associated with Pb-Zn mineralizations in the Devonian system of Qinling is discussed in the light of geologic setting,sedimentary-tectonic environment,lithological and chemical characteristics.On this basis,criteria for distinguishing them and their potential role as an indicator in prospecting are described.Ankerite-siliceous rocks are developed in the strata-bound Pb-Zn polymetallic belt in the Devonian system of Qinling.They are microcrystalline,dark grey and compact in appearance and are commonly carbonaceous,As a persistent ore-bearing horizon in the region,their genetic relation to the Pb-Zn deposits in generally accepted.However,a consensus has yet to be reached among geologists concerning their origein as a product of hydrothermal metasomtism at the late stage of sedimentation or as exhalite resulting from submarine exhalation.Accumulating evidence from direct observations on modern submarine hydrothermal systems strongly indicates that seafloor exhalation is a much more common geologic process than previously thought nd its metallogenic implications have long been overlooked.Characteristics of the ankerite-siliceous rocks as a product of exhalation and their significance as a guide in prospecting are described on the basis or geological setting,lithology,lithochemistry,REE,and isotopic and trace element features.

  5. Hydrothermal alteration geochemistry of Nugget gold vein system, Shotover valley, northwest Otago, New Zealand

    International Nuclear Information System (INIS)

    Ankeritic alteration zones are associated with gold mineralisation in the Nugget vein system, Shotover valley, northwest Otago. These zones consist of sheared and brecciated schist in Miocene normal faults. The zones are also extensively silicified. Mineralisation resulted from passage of low-salinity, low-CO2 water at 200-250 degrees C within a few kilometres of the surface. Alteration has involved replacement and veining of host pelitic schist in the mineralised zone. Most elements have been diluted by quartz and carbonate, with insignificant gains or losses. Ba has been leached as it became more soluble with decreasing fluid temperature. Considerable addition of Sr has occurred, as the fluid had higher Sr/Ca than most Otago mineralising fluids. Enrichment in Sr may be a distinctive feature of the Shotover style of mineralisation. Metallic mineralisation is due to addition of S, As, and Au during alteration. In contrast to many Otago gold vein systems, there has been no scheelite mineralisation. Carbonates have δ18O = +15.4 to +18.6, and δ13C = -8.2 to +0.5 per thousand. The oxygen isotopic signature is similar to other Otago gold veins. Carbon isotopes in aqueous CO2 which deposited Nugget ankerites are generally heavier (by 2-4 per thousand) than those in other Otago gold vein systems. This is caused by changes in dissolved carbonate species at the lower temperature, and fluid/rock interaction during ankerite mineralisation. (author). 29 refs., 10 figs., 2 tabs

  6. Mineralogical Analyses of a Precambrian Stromatolite

    OpenAIRE

    OHARA, Soji; Unno, Wasaburo; Tanaka, Masami; Sato, Yoshiyuki; Tanizawa, Kyoji

    1992-01-01

    [Abstract] Stromatolite is the fossil of the marine life of Infra-Cambrian era (ca.650-800Ma), having layered structure similar to the annual ring of woods. The mineralogy of these ring structures are studied by means of X-ray fluorescence analysis, IR (infra-red) absorption analysis and X-ray diffraction analysis. Dark-colored rings and light brown-colored intermediates are found to be consist of CaCO_3(Calcite) and Ca(FeMg)(CO_3)_2(Ankerite), respectively. Magnesium of chrolophyl origin is ...

  7. High resolution cathodoluminescence spectroscopy of carbonate cementation in Khurmala Formation (Paleocene-L. Eocene) from Iraqi Kurdistan Region, Northern Iraq

    Science.gov (United States)

    Omer, Muhamed F.; Omer, Dilshad; Zebari, Bahroz Gh.

    2014-12-01

    A combination of high resolution cathodoluminsecnce-spectroscopy (HRS-CL) with spatial electron microprobe analysis and optical microscopy is used to determine paragenesis and history of cementation in the limestones and dolostones of Khurmala Formation which is exposed in many parts of Northern Iraq. Khurmala Formation was subjected to different diagenetic processes such as micritization, compaction, dissolution, neomorphism, pyritization and cementation that occurred during marine to shallow burial stages and culminated during intermediate to deep burial later stages. Five dolomite textures are recognized and classified according to crystal size distribution and crystal-boundary shape. Dolomitization is closely associated with the development of secondary porosity that pre-and postdates dissolution and corrosion; meanwhile such porosity was not noticed in the associated limestones. Microprobe analysis revealed three types of cement, calcite, dolomite and ankerite which range in their luminescence from dull to bright. Cathodoluminescence study indicated four main texture generations. These are (1) unzoned microdolomite of planar and subhedral shape, with syntaxial rim cement of echinoderm that show dull to red luminescence, (2) equant calcite cements filling interparticle pores which shows dull luminescence and weak zonal growth, (3.1) homogenous intrinsic blue stoichiometric calcite with dull luminescence and without activators, (3.2) coarse blocky calcite cement with strong oscillatory zoning and bright orange luminescence which postdates other calcite cements, (4) ankerite cement with red to orange, non-luminescence growth zonation which is the last formed cement.

  8. Mineral identification in Colombian coals using Moessbauer spectroscopy and X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fajardo, M. [Universidad del Valle, A.A, Departamento de Fisica (Colombia); Mojica, J. [Instituto Nacional de Investigaciones en Geociencia, Mineria y Quimica (INGEOMINAS) (Colombia); Barraza, J. [Universidad del Valle, A.A, Departamento de Procesos Quimicos, Facultad de Ingenieria (Colombia); Perez Alcazar, G.A.; Tabares, J.A. [Universidad del Valle, A.A, Departamento de Fisica (Colombia)

    1999-11-15

    Minerals were identified in three Colombian coal samples from the Southwest of the country using Moessbauer spectroscopy and X-ray diffraction. Original and sink separated coal fractions of specific gravity 1.40 and 1.60 with particle size less than 600 {mu}m were used in the study. Using Moessbauer spectroscopy, the minerals identified in the original coal samples were pyrite jarosite, ankerite, illite and ferrous sulfate, whereas by means of X-ray diffraction, minerals identified were kaolinite, quartz, pyrite, and jarosite. Differences in mineral composition were found in the original and sink separated fractions using both techniques. Moessbauer spectra show that the mineral phases in low concentrations such as illite, ankerite and ferrous sulfate do not always appear in the spectra of sink coals, despite of those minerals occurring in the original coal, due to the fact that they are associated with the organic matter and not liberated in the grinding process. X-ray results show that the peak intensity grows as the specific gravity is increased indicating that the density separation method could be an effective process to clean coal.

  9. Rare earth chemistry of gold-bearing sedimentary carbonate horizons from the Abitibi Greenstone Belt, Ontario, Canada

    International Nuclear Information System (INIS)

    The ankerite, gold ore bodies of the Dome Mine, Timmins, Ontario are interflow units, 1 to 3 m thick in a sequence of tholeiitic basalts. The units consist of discontinuous layers of ferroan dolomite, chert and pyroclastic material, and laminations of iron sulfides, tourmaline, and graphite. They have been interpreted as sediments on the basis of their internal structure. Seven Rare Earth elements (REE) (Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb) were determined by instrumental neutron activation analysis, on 10 samples of carbonate material from the ankerite units. The chondrite normalized REE plots have relatively flat patterns with, in some cases, positive Europium anomalies. The flat patterns suggest that the fluids from which the carbonate precipitated was in equilibrium with volcanic rocks of tholeiitic and komatiitic composition. The positive Europium anomalies imply that the fluids were reducing at times. Such patterns are characteristic of Archaean sediments and also the precipitates associated with the discharge of hydrothermal solutions from vents on the East Pacific Rise

  10. Effects of H2S injection on the CO2-brine-sandstone interaction under 21MPa and 70°C.

    Science.gov (United States)

    Li, Chenyang; Zhang, Fengjun; Lyu, Cong; Hao, Jie; Song, Jianbin; Zhang, Shengyu

    2016-05-15

    In this study, laboratory experiments were conducted to investigate the influences of H2S injection on the capacity of CO2's solubility trapping and mineral trapping. Results demonstrated that the preferential dissolution of H2S gas into brine (compared with pure CO2) resulted in the decrease of pH, consequently inhibiting the CO2's solubility trappings to some extent. Then, the lower pH droved more severe corrosion of primary minerals, favored more secondary mineral to be formed. In addition, the discovery of pyrite demonstrated that H2S could precipitate by the formation of sulfide mineral trapping. As the secondary carbon sink minerals, ankerite and dawsonite were observed in the pure CO2-brine-sandstone interaction. However, there were no secondary carbonates found through the SEM images and EDS analyses, implied that the injection of H2S probably may partially inhibit the precipitation of Fe-bearing carbonate minerals such as ankerite in the CO2-H2S-brine-sandstone interaction in this short term experiments.

  11. ASTER spectral analysis and lithologic mapping of the Khanneshin carbonatite volcano, Afghanistan

    Science.gov (United States)

    Mars, J.C.; Rowan, L.C.

    2011-01-01

    Advanced Spaceborne Thermal and Reflection Radiometer (ASTER) data of the early Quaternary Khanneshin carbonatite volcano located in southern Afghanistan were used to identify carbonate rocks within the volcano and to distinguish them from Neogene ferruginous polymict sandstone and argillite. The carbonatitic rocks are characterized by diagnostic CO3 absorption near 11.2 ??m and 2.31-2.33 ??m, whereas the sandstone, argillite, and adjacent alluvial deposits exhibit intense Si-O absorption near 8.7 ??m caused mainly by quartz and Al-OH absorption near 2.20 ??m due to muscovite and illite. Calcitic carbonatite was distinguished from ankeritic carbonatite in the short wave infrared (SWIR) region of the ASTER data due to a slight shift of the CO3 absorption feature toward 2.26 ??m (ASTER band 7) in the ankeritic carbonatite spectra. Spectral assessment using ASTER SWIR data suggests that the area is covered by extensive carbonatite flows that contain calcite, ankerite, and muscovite, though some areas mapped as ankeritic carbonatite on a pre existing geologic map were not identified in the ASTER data. A contact aureole shown on the geologic map was defined using an ASTER false color composite image (R = 6, G = 3, B = 1) and a logical operator byte image. The contact aureole rocks exhibit Fe2+, Al-OH, and Fe, Mg-OH spectral absorption features at 1.65, 2.2, and 2.33 ??m, respectively, which suggest that the contact aureole rocks contain musco vite, epidote, and chlorite. The contact aureole rocks were mapped using an Interactive Data Language (IDL) logical operator. A visible through short wave infrared (VNIR-SWIR) mineral and rock-type map based on matched filter, band ratio, and logical operator analysis illustrates: (1) laterally extensive calcitic carbonatite that covers most of the crater and areas northeast of the crater; (2) ankeritic carbonatite located southeast and north of the crater and some small deposits located within the crater; (3) agglomerate that

  12. Predicting cement distribution in geothermal sandstone reservoirs based on estimates of precipitation temperatures

    Science.gov (United States)

    Olivarius, Mette; Weibel, Rikke; Whitehouse, Martin; Kristensen, Lars; Hjuler, Morten L.; Mathiesen, Anders; Boyce, Adrian J.; Nielsen, Lars H.

    2016-04-01

    Exploitation of geothermal sandstone reservoirs is challenged by pore-cementing minerals since they reduce the fluid flow through the sandstones. Geothermal exploration aims at finding sandstone bodies located at depths that are adequate for sufficiently warm water to be extracted, but without being too cemented for warm water production. The amount of cement is highly variable in the Danish geothermal reservoirs which mainly comprise the Bunter Sandstone, Skagerrak and Gassum formations. The present study involves bulk and in situ stable isotope analyses of calcite, dolomite, ankerite, siderite and quartz in order to estimate at what depth they were formed and enable prediction of where they can be found. The δ18O values measured in the carbonate minerals and quartz overgrowths are related to depth since they are a result of the temperatures of the pore fluid. Thus the values indicate the precipitation temperatures and they fit the relative diagenetic timing identified by petrographical observations. The sandstones deposited during arid climatic conditions contain calcite and dolomite cement that formed during early diagenesis. These carbonate minerals precipitated as a response to different processes, and precipitation of macro-quartz took over at deeper burial. Siderite was the first carbonate mineral that formed in the sandstones that were deposited in a humid climate. Calcite began precipitating at increased burial depth and ankerite formed during deep burial and replaced some of the other phases. Ankerite and quartz formed in the same temperature interval so constrains on the isotopic composition of the pore fluid can be achieved. Differences in δ13C values exist between the sandstones that were deposited in arid versus humid environments, which suggest that different kinds of processes were active. The estimated precipitation temperatures of the different cement types are used to predict which of them are present in geothermal sandstone reservoirs in

  13. The Werkendam natural CO2 accumulation: An analogue for CO2 storage in depleted oil reservoirs

    Science.gov (United States)

    Bertier, Pieter; Busch, Andreas; Hangx, Suzanne; Kampman, Niko; Nover, Georg; Stanjek, Helge; Weniger, Philipp

    2015-04-01

    The Werkendam natural CO2 accumulation is hosted in the Röt (Early Triassic) sandstone of the West Netherlands Basin, at a depth of 2.8 km, about 20 km south-east of Rotterdam (NL). This reservoir, in a fault-bound structure, was oil-filled prior to charging with magmatic CO2 in the early Cretaceous. It therefore offers a unique opportunity to study long-term CO2-water-rock interactions in the presence of oil. This contribution will present the results of a detailed mineralogical and geochemical characterisation of core sections from the Werkendam CO2 reservoir and an adjacent, stratigraphically equivalent aquifer. X-ray diffraction combined with X-ray fluorescence spectrometry revealed that the reservoir samples contain substantially more feldspar and more barite and siderite than those from the aquifer, while the latter have higher hematite contents. These differences are attributed to the effects hydrocarbons and related fluids on diagenesis in the closed system of the CO2 reservoir versus the open-system of the aquifer. Petrophysical analyses yielded overall higher and more anisotropic permeability for the reservoir samples, while the porosity is overall not significantly different from that of their aquifer equivalents. The differences are most pronounced in coarse-grained sandstones. These have low anhydrite contents and contain traces of calcite, while all other analyzed samples contain abundant anhydrite, dolomite/ankerite and siderite, but no calcite. Detailed petrography revealed mm-sized zones of excessive primary porosity. These are attributed to CO2-induced dissolution of precompactional, grain-replacive anhydrite cement. Diagenetic dolomite/ankerite crystals are covered by anhedral, epitaxial ankerite, separated from the crystals by bitumen coats. Since these carbonates were oil-wet before CO2-charging, the overgrowths are interpreted to have grown after CO2-charging. Their anhedral habit suggests growth in a 2-phase water-CO2 system. Isotopic

  14. Carbonate hosted gold deposit in Tasmania, Australia

    International Nuclear Information System (INIS)

    Full text: This study uses elemental and isotopic composition of carbonates associated with gold from Henty and Beaconsfield in Tasmania, Australia, to illustrate source of gold-bearing fluids, salinity, temperature and dissolution and reprecipitation of carbonate. The Beaconsfield and Henty gold mines are located in northern and western Tasmania respectively. Gold mineralisation in Beaconsfield occurs within the quartz-carbonate Tasmania Reef (Lower to Middle Palaeozoic sequence, Hills, 1998). The Henty gold mine is located at the base of the Cambrian Tyndall Group (volcano-sedimentary succession, White and McPhie, 1996) close to Henty Fault. Gold in carbonate samples from Henty ranges from 7.7 to 9360 ppm and in Beaconsfield ranges from 0.01 to 434 ppm. The amount of carbonate in samples from Henty and Beaconsfield gold mines varies from approximately 24 to 99.8%. Bivariate plot of Ca relative to total amounts of Mg, Fe and Mn illustrates that the major carbonate minerals at Beaconsfield and Henty gold mines are magnesian ankerite and calcite. The difference in carbonate mineralogy, at Henty and Beaconsfield gold mines, is attributed to the composition of fluids responsible for carbonate alteration. Gold and magnesium in Beaconsfield ankerite are derived from the leaching of Cambrian ultramafic rocks during the Devonian by the passage of meteoric fluids through tectonically affected Ordovician carbonates (Rao and Adabi, 1999). The total concentration of Fe and Mn are low (0.5 to 2%) in Henty and high (1 to 17.5%) in Beaconsfield ankerite, possibly due to oxidising conditions at Henty and reducing conditions at Beaconsfield gold mines during gold mineralisation. Variation of Sr values between Beaconsfield ankerite and Henty calcite is related to dissolution of limestone that increase Sr concentrations in gold mineralising fluids. Na values in both Beaconsfield (20 to 1100 ppm) and Henty carbonates (25 to 1650 ppm) suggest low salinity fluids responsible for gold

  15. Diagenesis and Fluid Flow History in Sandstones of the Upper Permian Black Jack Formation, Gunnedah Basin, Eastern Australia

    Institute of Scientific and Technical Information of China (English)

    BAI Guoping; John B. KEENE

    2007-01-01

    The fluid flow history during diagenesis of sandstones in the Upper Permian Black Jack Formation of the Gunnedah Basin has been investigated through integrated petrographic observations, fluid inclusion investigations and stable isotope analyses. The early precipitation of mixed-layer illite/smectite, siderite, calcite, ankerite and kaolin proceeded at the presence of Late Permian connate meteoric waters at temperatures of up to 60℃. These evolved connate pore waters were also parental to quartz, which formed at temperatures of up to 87℃. The phase of maximum burial was characterized by development of filamentous illite and late calcite at temperatures of up to ~90℃. Subsequent uplifting and cooling led to deep meteoric influx from surface, which in turn resulted in dissolution of labile grains and carbonate cements, and formation of second generation of kaolin. Dawsonite was the last diagenetic mineral precipitated and its formation is genetically related to deep-seated mamagtic sourced CO2.

  16. Formation of the world's largest REE deposit through protracted fluxing of carbonatite by subduction-derived fluids

    Science.gov (United States)

    Ling, Ming-Xing; Liu, Yu-Long; Williams, Ian S.; Teng, Fang-Zhen; Yang, Xiao-Yong; Ding, Xing; Wei, Gang-Jian; Xie, Lu-Hua; Deng, Wen-Feng; Sun, Wei-Dong

    2013-01-01

    Rare Earth Elements (REE) are essential to modern society but the origins of many large REE deposits remain unclear. The U-Th-Pb ages, chemical compositions and C, O and Mg isotopic compositions of Bayan Obo, the world's largest REE deposit, indicate a protracted mineralisation history with unusual chemical and isotopic features. Coexisting calcite and dolomite are in O isotope disequilibrium; some calcitic carbonatite samples show highly varied δ26Mg which increases with increasing Si and Mg; and ankerite crystals show decreases in Fe and REE from rim to centre, with highly varied REE patterns. These and many other observations are consistent with an unusual mineralisation process not previously considered; protracted fluxing of calcitic carbonatite by subduction-released high-Si fluids during the closure of the Palaeo-Asian Ocean. The fluids leached Fe and Mg from the mantle wedge and scavenged REE, Nb and Th from carbonatite, forming the deposit through metasomatism of overlying sedimentary carbonate.

  17. Microstructural characterization of material used as supporter in pre hispanic paints; Caracterizacion microestructural de material utilizado como soporte en pinturas prehispanicas

    Energy Technology Data Exchange (ETDEWEB)

    Silva V, Y. [FIME-UANL, San Nicolas de los Garza, Nuevo Leon (Mexico); Zorrilla, C.; Canetas, J.; Hernandez, R.; Aguilar F, M.; Arenas A, J. [IFUNAM, 04510 Mexico D.F. (Mexico); Martinez, G. [INAH, 04000 Mexico D.F. (Mexico)

    2005-07-01

    The aim of this work is to show the characterization of pre hispanic paintings mainly of the materials that support the pigments. The samples come from three different archaeological sites, Palenque-Chiapas (two specimens), Teotihuacan-Estado de Mexico (one specimen) and Mitla-Oaxaca (one specimen); Mayan, Teotihuacan and Mixtec-Zapotec culture respectively. The samples were analyzed by Sem, EDS, Tem, XRD and IR. The results show calcite as common phase for all the samples, however exist other phases identified depending on the site as dolomite, ankerite, calcium silicon chloride, etc. The origin of the red color of the analyzed pigments were cinnabar (HgS) by a sample of Palenque and hematite (Fe{sub 2}O{sub 3}) by the other specimen, this last crystalline phase also present in the Mitla and Teotihuacan samples. By IR were identified some organic compounds in all the samples, but not copal. (Author)

  18. Mineral Sequestration of Carbon Dixoide in a Sandstone-Shale System

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Apps, John A.; Pruess, Karsten

    2004-07-09

    A conceptual model of CO2 injection in bedded sandstone-shale sequences has been developed using hydrogeologic properties and mineral compositions commonly encountered in Gulf Coast sediments. Numerical simulations were performed with the reactive fluid flow and geochemical transport code TOUGHREACT to analyze mass transfer between sandstone and shale layers and CO2 immobilization through carbonate precipitation. Results indicate that most CO2 sequestration occurs in the sandstone. The major CO2 trapping minerals are dawsonite and ankerite. The CO2 mineral-trapping capacity after 100,000 years reaches about 90 kg per cubic meter of the medium. The CO2 trapping capacity depends on primary mineral composition. Precipitation of siderite and ankerite requires Fe+2 supplied mainly by chlorite and some by hematite dissolution and reduction. Precipitation of dawsonite requires Na+ provided by oligoclase dissolution. The initial abundance of chlorite and oligoclase therefore affects the CO2 mineral trapping capacity. The sequestration time required depends on the kinetic rate of mineral dissolution and precipitation. Dawsonite reaction kinetics is not well understood, and sensitivity regarding the precipitation rate was examined. The addition of CO2 as secondary carbonates results in decreased porosity. The leaching of chemical constituents from the interior of the shale causes slightly increased porosity. The limited information currently available for the mineralogy of natural high-pressure CO2 gas reservoirs is also generally consistent with our simulation. The ''numerical experiments'' give a detailed understanding of the dynamic evolution of a sandstone-shale geochemical system.

  19. A Geochemical Investigation of the Early Cretaceous Ultrapotassic Dykes in the Raniganj Coalfields in Damodar Valley, India

    Science.gov (United States)

    Jude, T. A.

    2015-12-01

    The early Cretaceous ultrapotassic dyke rocks intruding the Permocarboniferous coal bearing Gondwana sediments of the Eastern Damodar Valley, Singhbum craton, are known for their petrographic and geochemical diversity. They remain a 'Pandora's box of petrological confusion' with a variety of exotic, and potentially diamondiferous, rocks such as lamprophyre, lamproite, orangeite and kimberlite being continuously reported from them for over one century or more. Intra-plate volcanism of this type discloses hidden information about the interior of the Earth. Samples from two dykes intruding Raniganj coalfield is studied here. The samples from Dyke1 are characterized by fine grained texture and phlogopite+apatite+K-feldspar+rutile+ankerite+dolomite+ chromite+chlorite+quartz assemblage while the samples from Dyke2 are characterized by coarse grained texture and phlogopite+ pseudomorphosed-olivine+apatite+ clinopyroxene +dolomite+ankerite+calcite+norsethite+talc+rutile+quartz+Ca-Mg-Fe-Zr silicate+K-feldspar+monazite+ perovskite assemblage. Based on the TiO2-Al2O3-FeO trends observed in phlogopites, the dykes seem to be a lamproite-orangeite transitional variety. The phlogopites observed in Dyke2 show two stages of crystallization defined by Ti-poor overgrowths on Ti-rich cores indicating that Dyke2 consolidated from a melt that fractionated from a magma which was initially emplaced at a different depth while the Dyke 1 phlogopites do not show any such sudden drop in Ti concentration in their rims indicating single stage crystallization. Ti-in-Quartz Thermometry yields temperatures between 769°C to 1115°C for Dyke1 and 779°C to 1019°C for Dyke2 which must corresponds to the emplacement and crystallization of these dykes. Trace element and isotopic ratios can be used to constrain particular mantle source characteristics of the dykes. Rb-Sr method can be used to determine the emplacement ages of these dykes.

  20. Exhalative Lead-Zinc Deposits in Shallow Sea, Southern Xicheng Belt, Gansu Province

    Institute of Scientific and Technical Information of China (English)

    ZHU Xinyou; WANG Dongbo; WEI Zhiguo; QIU Xiaoping; WANG Ruiting

    2008-01-01

    SEDEX-type lead-zinc deposits in the southern belt of the Xicheng Devonian basin, GansuProvince has been already identified. However, the sedimentary environment of the limestone andphilite of the Xihanshui Group within which the lead-zinc deposits occur is littoral and shallow sea.This is different from those in the northern belt such as the Changba-Lijiagou lead-zinc deposits, whichwere formed in deep sea. The reef and bioclastic limestone are widespread in the southern belt.Particularly they are associated with lead-zinc ores and there are no striae and banding but massive ordisseminated structures. It is discovered that the black chimney consists of sphalerite, ankerite, pyriteand galena, in which black, coarse and radial sphalerite occurs as irregularly veins or cylindricafitywith a width of 10-40 cm in the center, and it is surround by fine ankerite and minor celestite withribbon structure. The immediate wall rock of the chimney, reef limestone, was unaltered and theoutside reef and bioclastic limestone were intensively silicified. Those silicified reef and bioclasticlimestone host disseminated lead-zinc ores of the Lnoba and Bijiashan type. It is concluded that theexhalative system occurred in a shallow sea in the Givetian of the middle Devonian. Brine is boiled dueto low pressure, and a great deal of lead and zinc was dispersed in the interface between the limestoneand phyllite and formed a source bed. In the Triassic period, meta-hydrothermai fluids leached andextracted metals from the source bed, and then moved and mineralized in open space such as archesand inverse limbs of anticlines, and formed massive and vein ores such as the Jianyagou andDengjiashan type deposits.

  1. Geology of the Alaska-Juneau lode system, Alaska

    Science.gov (United States)

    Twenhofel, William Stephens

    1952-01-01

    inches to 3 feet wide and extending along their strike and dip for several tens to hundreds of feet. In addition to quartz, the only other vein gangue mineral is ankerite. It occurs in small amounts along the borders of the quartz veins. Metallic vein minerals, in addition to native gold, are, in order of decreasing abundance, pyrrhotite, galena, sphalerite, and arsenopyrite. In the aggregate the metallic minerals comprise only 1 to 2 percent of the total amount of vein material. The wall rock, particularly the meta-gabbro, was profoundly altered by the vein-forming processes. The principal effects on the meta-gabbro were the addition of large amounts of soda, potash, titanium, carbon dioxide, and phosphorous, and the removal of considerable quantities of iron, magnesia, lime, and combined water. Silica also may have been decreased. The mineralogical changes involved in the alteration were the development of biotite and ankerite at the expense of original hornblende and feldspar, resulting in a brown-colored biotite- and ankerite-rich rock. The slates are relatively unaffected by the vein-forming processes. Because of their small size, relatively low grade, and discontinuity, no attempt has been made to mine any individual vein. The prevailing practice has been to mine large blocks of ground by a system of modified block-caving, followed by hand sorting to remove the barren country rock from the gold-bearing quartz prior to milling.

  2. The thermal and chemical evolution of hydrothermal vent fluids in shale hosted massive sulphide (SHMS) systems from the MacMillan Pass district (Yukon, Canada)

    Science.gov (United States)

    Magnall, J. M.; Gleeson, S. A.; Blamey, N. J. F.; Paradis, S.; Luo, Y.

    2016-11-01

    At Macmillan Pass (YT, Canada), the hydrothermal vent complexes beneath two shale-hosted massive sulphide (SHMS) deposits (Tom, Jason) are well preserved within Late Devonian strata. These deposits provide a unique opportunity to constrain key geochemical parameters (temperature, salinity, pH, fO2, ΣS) that are critical for metal transport and deposition in SHMS systems, and to evaluate the interaction between hydrothermal fluids and the mudstone host rock. This has been achieved using a combination of detailed petrography, isotopic techniques (δ34S, δ13C and δ18O values), carbonate rare earth element analysis (LA-ICP-MS), fluid inclusion analysis (microthermometry, gas analysis via incremental crush fast scan mass spectrometry), and thermodynamic modelling. Two main paragenetic stages are preserved in both vent complexes: Stage 1 comprises pervasive ankerite alteration of the organic-rich mudstone host rock and crosscutting stockwork ankerite veining (±pyrobitumen, pyrite and quartz) and; Stage 2 consists of main stage massive sulphide (galena-pyrrhotite-pyrite ± chalcopyrite-sphalerite) and siderite (±quartz and barytocalcite) mineralisation. Co-variation of δ18O and δ13C values in ankerite can be described by temperature dependent fractionation and fluid rock interaction. Together with fluid inclusion microthermometry, this provides evidence of a steep thermal gradient (from 300 to ∼100 °C) over approximately 15 m stratigraphic depth, temporally and spatially constrained within the paragenesis of both vent complexes and developed under shallow lithostatic (28), characteristic of diagenetic fluids, are coupled with positive europium anomalies and variable light REE depletion, which are more consistent with chloride complexation in hot (>250 °C) hydrothermal fluids. In this shallow sub-seafloor setting, thermal alteration of organic carbon in the immature, chemically reactive mudstones also had an important role in the evolution of fluid chemistry

  3. Fluid evolution and mineralogy of Mn-Fe-barite-fluorite mineralizations at the contact of the Thuringian Basin, Thüringer Wald and Thüringer Schiefergebirge in Germany

    Directory of Open Access Journals (Sweden)

    Majzlan Juraj

    2016-02-01

    Full Text Available Numerous small deposits and occurrences of Mn-Fe-fluorite-barite mineralization have developed at the contact of the Thuringian Basin, Thüringer Wald and Thüringer Schiefergebirge in central Germany. The studied mineralizations comprise the assemblages siderite+ankerite-calcite-fluorite-barite and hematite-Mn oxides-calcite-barite, with the precipitation sequence in that order within each assemblage. A structural geological analysis places the origin of the barite veins between the Middle Jurassic and Early Cretaceous. Primary fluid inclusions contain water vapour and an aqueous phase with NaCl and CaCl2 as the main solutes, with salinities mostly between 24–27 mass. % CaCl2 eq. Th measurements range between 85 °C and 160 °C in barite, between 139 °C and 163 °C in siderite, and between 80 °C and 130 °C in fluorite and calcite. Stable isotopes (S, O point to the evaporitic source of sulphur in the observed mineralizations. The S,C,O isotopic compositions suggest that barite and calcite could not have precipitated from the same fluid. The isotopic composition of the fluid that precipitated barite is close to the sea water in the entire Permo–Mesozoic time span whereas calcite is isotopically distinctly heavier, as if the fluids were affected by evaporation. The fluid evolution in the siliciclastic/volcanic Rotliegend sediments (as determined by a number of earlier petrological and geochemical studies can be correlated with the deposition sequence of the ore minerals. In particular, the bleaching of the sediments by reduced Rotliegend fluids (basinal brines could be the event that mobilized Fe and Mn. These elements were deposited as siderite+ankerite within the Zechstein carbonate rocks and as hematite+Mn oxides within the oxidizing environment of the Permian volcanic and volcanoclastic rocks. A Middle-Jurassic illitization event delivered Ca, Na, Ba, and Pb from the feldspars into the basinal brines. Of these elements, Ba was

  4. A high-pyrite semianthracite of Late Permian age in the Songzao Coalfield, southwestern China: Mineralogical and geochemical relations with underlying mafic tuffs

    Science.gov (United States)

    Dai, S.; Wang, X.; Chen, W.; Li, D.; Chou, C.-L.; Zhou, Y.; Zhu, Chen; Li, H.; Zhu, Xudong; Xing, Y.; Zhang, W.; Zou, J.

    2010-01-01

    The No. 12 Coal (Late Permian) in the Songzao Coalfield, Chongqing, southwestern China, is characteristically high in pyrite and some trace elements. It is uniquely deposited directly above mafic tuff beds. Samples of coal and tuffs have been studied for their mineralogy and geochemistry using inductively coupled plasma-mass spectrometry, X-ray fluorescence, plasma low-temperature ashing plus powder X-ray diffraction, and scanning electron microscopy equipped with energy-dispersive X-ray analysis.The results show that the minerals of the No. 12 Coal are mainly composed of pyrite, clay minerals (kaolinite, chamosite, and illite), ankerite, calcite, and trace amounts of quartz and boehmite. Kaolinite and boehmite were mainly derived from sediment source region of mafic tuffs. Chamosite was formed by the reaction of kaolinite with Fe-Mg-rich fluids during early diagenesis. The high pyrite (Sp,d=8.83%) in the coal was related to marine transgression over peat deposits and abundant Fe derived from the underlying mafic tuff bed. Ankerite and calcite were precipitated from epigenetic fluids.Chemical compositions of incompatible elements indicate that the tuffs were derived from enriched mantle and the source magmas had an alkali-basalt character. Compared to other coals from the Songzao Coalfield and common Chinese coals, the No. 12 Coal has a lower SiO2/Al2O3 (1.13) but a higher Al2O3/Na2O (80.1) value and is significantly enriched in trace elements including Sc (13.5??g/g), V (121??g/g), Cr (33.6??g/g), Co (27.2??g/g), Ni (83.5??g/g), Cu (48.5??g/g), Ga (17.3??g/g), Y (68.3??g/g), Zr (444??g/g), Nb (23.8??g/g), and REE (392??g/g on average). Above mineralogical compositions, as well as similar ratios of selected elements (e.g., SiO2/Al2O3 and Al2O3/Na2O) and similar distribution patterns of incompatible elements (e.g., the mantle-normalized diagram for incompatible elements and chondrite-normalized diagram for rare earth elements) of coal and tuff, indicated that

  5. Diagenesis and reservoir quality evolution of palaeocene deep-water, marine sandstones, the Shetland-Faroes Basin, British continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    Mansurbeg, H. [Department of Earth Sciences, Uppsala University, Villavaegen 16, SE 752 36 Uppsala (Sweden); Morad, S. [Department of Earth Sciences, Uppsala University, Villavaegen 16, SE 752 36 Uppsala (Sweden); Department of Petroleum Geosciences, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Salem, A. [Faculty of Education at Kafr El-Sheikh, Tanta University, Kafr El-Sheikh (Egypt); Marfil, R.; Caja, M.A. [Departmento Petrologia y Geoquimica, Facultad de Geologia, UCM, 28040 Madrid (Spain); El-ghali, M.A.K. (Geology Department, Al-Fateh University, P.O. Box 13696, Libya); Nystuen, J.P. [Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, NO-0316 Oslo (Norway); Amorosi, A. [Department of Earth Sciences, University of Bologna, Via Zamboni 67, 40127 Bologna (Italy); Garcia, D. [Centre SPIN, Department GENERIC, Ecole Nationale Superieure des Mines de Saint Etienne 158, Cours Fauriel 42023, Saint-Etienne (France); La Iglesia, A. [Instituto de Geologia Economica (CSIC-UCM), Facultad de Geologia, UCM, 28040 Madrid (Spain)

    2008-06-15

    The Palaeocene, deep-water marine sandstones recovered from six wells in the Shetland-Faroes Basin represent lowstand, transgressive and highstand systems tract turbiditic sediments. Mineralogic, petrographic, and geochemical analyses of these siliciclastics are used to decipher and discuss the diagenetic alterations and subsequent reservoir quality evolution. The Middle-Upper Palaeocene sandstones (subarkoses to arkoses) from the Shetland-Faroes Basin, British continental shelf are submarine turbiditic deposits that are cemented predominantly by carbonates, quartz and clay minerals. Carbonate cements (intergranular and grain replacive calcite, siderite, ferroan dolomite and ankerite) are of eogenetic and mesogenetic origins. The eogenetic alterations have been mediated by marine, meteoric and mixed marine/meteoric porewaters and resulted mainly in the precipitation of calcite ({delta}{sup 18}O{sub V-PDB}=-10.9 permille and -3.8 permille), trace amounts of non-ferroan dolomite, siderite ({delta}{sup 18}O{sub V-PDB}=-14.4 permille to -0.6 permille), as well as smectite and kaolinite in the lowstand systems tract (LST) and highstand systems tract (HST) turbiditic sandstone below the sequence boundary. Minor eogenetic siderite has precipitated between expanded and kaolinitized micas, primarily biotite. The mesogenetic alterations are interpreted to have been mediated by evolved marine porewaters and resulted in the precipitation of calcite ({delta}{sup 18}O{sub V-PDB}=-12.9 permille to -7.8 permille) and Fe-dolomite/ankerite ({delta}{sup 18}O{sub V-PDB}=-12.1 permille to -6.3 permille) at temperatures of 50-140 and 60-140 C, respectively. Quartz overgrowths and outgrowth, which post- and pre-date the mesogenetic carbonate cements is more common in the LST and TST of distal turbiditic sandstone. Discrete quartz cement, which is closely associated with illite and chlorite, is the final diagenetic phase. The clay minerals include intergranular and grain replacive

  6. Petrography and geochemistry of Oligocene bituminous coal from the Jiu Valley, Petrosani basin (southern Carpathian Mountains), Romania

    Energy Technology Data Exchange (ETDEWEB)

    Belkin, Harvey E.; Tewalt, Susan J. [U.S. Geological Survey, 956 National Center, Reston, VA 20192 (United States); Hower, James C. [University of Kentucky Center for Applied Energy Research, 2540 Research Park Drive, Lexington, KY 40511 (United States); Stucker, J.D. [University of Kentucky Center for Applied Energy Research, 2540 Research Park Drive, Lexington, KY 40511 (United States); University of Kentucky Department of Earth and Environmental Sciences, Lexington, KY 40506 (United States); O' Keefe, Jennifer M.K. [Morehead State University, Morehead, KY, 40351 (United States); Tatu, Calin A. [University of Medicine and Pharmacy, Department of Immunology, Clinical Laboratory No. 1, Pta. E. Murgu No. 2, RO-1900 Timisoara (Romania); Buia, Grigore [University of Petrosani, Department of Geology, University St. 20, RO-2675 Petrosani (Romania)

    2010-05-01

    Belt samples of Oligocene (Chattian) bituminous coal from 10 underground mines located in the Jiu Valley, Hunedoara County, Petrosani basin, Romania, have been examined and analyzed for proximate and ultimate analysis, major-, minor- and trace-element chemistry, organic petrography, and vitrinite reflectance. The mineral chemistry and mode of occurrence of trace elements also have been investigated using SEM and electron microprobe techniques. Twenty coal beds occur in the Jiu Valley and most of the samples are from bed no. 3, the most productive bed of the Dilja-Uricani Formation of Oligocene age. The Petrosani basin, oriented SW-NE, is 48-km long, 10-km wide at the eastern part and 2-km wide at the western part. The coal mines are distributed along the center of the valley generally following the Jiu de Vest River. Reflectance measurements indicate that the rank of the coals ranges from high-volatile B to high-volatile A bituminous. Overall, rank decreases from the southwest to the northeast. In bed no. 3, R{sub max} varies from 0.75% in the northeast to 0.93% in the southwest. Although, most Oligocene coals in Romania and adjacent countries are lignite in rank, the Jiu Valley bituminous coals have been affected by regional metamorphism and attending hydrothermal fluids related to the Alpine orogenic event. The coals are all dominated by vitrinite; resinite and funginite are important minor macerals in most of the coals. Pyrite and carbonate generally dominate the mineral assemblages with carbonate more abundant in the northwest. Siderite occurs as nodules and masses within the macerals (generally vitrinite). Dolomite and calcite occur as fracture fillings, plant-cell fillings, and in other authigenic forms. Late-stage fracture fillings are siderite, dolomite, calcite, and ankerite. In one instance, two populations of siderite ({proportional_to} 35 and {proportional_to} 45 wt.% FeO) plus ankerite fill a large fracture. Late-stage pyrite framboid alteration is Ni

  7. Geochemistry of Precambrian carbonates: II. Archean greenstone belts and Archean sea water.

    Science.gov (United States)

    Veizer, J; Hoefs, J; Lowe, D R; Thurston, P C

    1989-01-01

    Carbonate rocks with geological attributes of marine sediments are a minor component of the Archean greenstone belts. Despite their relative scarcity, these rocks are important because they record chemical and isotopic properties of coeval oceans. The greenstones containing such carbonates appear to cluster at approximately 2.8 +/- 0.2 and approximately 3.5 +/- 0.1 Ga ago. The samples for the younger group are from the Abitibi, Yellowknife, Wabigoon (Steep Rock Lake), Michipicoten and Uchi greenstone belts of Canada and the "Upper Greenstones" of Zimbabwe. The older group includes the Swaziland Supergroup of South Africa, Warrawoona Group of Australia and the Sargur marbles of India. Mineralogically, the carbonates of the younger greenstones are mostly limestones and of the older ones, ferroan dolomites (ankerites); the latter with some affinities to hydrothermal carbonates. In mineralized areas with iron ores, the carbonate minerals are siderite +/- ankerite, irrespective of the age of the greenstones. Iron-poor dolomites represent a later phase of carbonate generation, related to post-depositional tectonic faulting. The original mineralogy of limestone sequences appears to have been an Sr-rich aragonite. The Archean carbonates yield near-mantle Sr isotopic values, with (87Sr/86Sr)o of 0.7025 +/- 0.0015 and 0.7031 +/- 0.0008 for younger and older greenstones, respectively. The best preserved samples give delta 13C of +1.5 +/- 1.5% PDB, comparable to their Phanerozoic counterparts. In contrast, the best estimate for delta 18O is -7% PDB. Archean limestones, compared to Phanerozoic examples, are enriched in 16O as well as in Mn2+ and Fe2+, and these differences are not a consequence of post-depositional alteration phenomena. The mineralogical and chemical attributes of Archean carbonates (hence sea water) are consistent with the proposition that the composition of the coeval oceans may have been buffered by a pervasive interaction with the "mantle", that is, with

  8. The Gifford Creek Ferrocarbonatite Complex, Gascoyne Province, Western Australia: Associated fenitic alteration and a putative link with the ~ 1075 Ma Warakurna LIP

    Science.gov (United States)

    Pirajno, Franco; González-Álvarez, Ignacio; Chen, Wei; Kyser, Kurt T.; Simonetti, Antonio; Leduc, Evelyne; leGras, Monica

    2014-08-01

    The Gifford Creek Ferrocarbonatite Complex (GFC), located in the Neoarchean-Palaeoproterozoic Gascoyne Province, Western Australia, comprises sills, dykes, and veins of ferrocarbonatite intruding the Pimbyana Granite and Yangibana Granite of the Durlacher Supersuite and metasedimentary rocks of the Pooranoo Metamorphics. The ferrocarbonatites are associated with complex and irregularly distributed zones of fenitic alteration. These ferrocarbonatites and fenites are also associated with a swarm of ironstone veins, containing magnetite, hematite and goethite. The GFC and associated fenite outcrops are distributed within a ~ 700 km2 area, north of the Lyons River Fault. Ferrocarbonatite sills and dykes are predominant in a northwest-trending belt, along the southern margin of the complex; whereas ferrocarbonatite veins tend to be distributed in a series of sub-parallel west-northwest-trending linear belts, generally associated with the Fe oxide veins with sinuous trends. These veins have margins of Fe-rich carbonates associated with zones of alteration that have a fenitic character. The fenitic haloes are characterised by the presence of Na-K-feldspars and/or Na-amphiboles and magnetite. In some cases monomineralic feldspar zones (orthoclasite) are present. Fenitic alteration is spatially associated with the carbonatites, but it can also form discrete veins and veinlets in basement granitic rocks (Pimbyana and Yangibana Granites). Petrographic, XRD and SEM analyses show that the ferrocarbonatites are dominantly composed of ankerite-dolomite, magnetite, arfvedsonite-riebeckite, and lesser calcite. Alkali amphibole has compositions ranging from potassian magnesio-arfvedsonite to magnesio-riebeckite. Sills and dykes north of the Lyons River, are characterised by a carbonate-rich matrix, containing > 50 vol.% ankerite-dolomite, with accessory quantities of apatite, barite, monazite, and phlogopite. In-situ U-Pb age determination of apatite grains by LA-ICP-MS on a sample

  9. ARCHAEOMETRICAL STUDIES ON WALL PAINTINGS OF ZEUGMA (GAZİANTEP ANCIENT SITEABSTRACT

    Directory of Open Access Journals (Sweden)

    Şahinde DEMİRCİ

    2011-06-01

    Full Text Available In this study, Zeugma wall paintings and related materials including sediment and stone/rock had been examined. Samples were examined to get their raw material characteristics, mineralogical and chemical compositions, and microstructural properties using various analytical techniques. Sediments were calcereous soils of Eocene. Rock types of stones were mainly limestone which had 3 subgroups: micritic, biomicritic and recrytallised micritic limestones. The source of the limestones should be from the local formation. Binder of mortar samples were lime, aggregate materials come from the river deposites of Euphrates. Mural painting samples have different layers; pigment layer at the top, intonaco layer underneat, and single or double rather coarse grained arriccio layer(s below intonaco layer. The mural painting technique was fresco technique. Calcite was common mineral identified for all pigments of different colours. The sources of white, black and green coloured pigments were found as vaterite, graphite and malachite respectively. The sources of yellow coloured pigments were identified as ankerite, siderite and goethite. The red colours were identified as hematite, jasper and red earth/ochre. Jasper and vaterite, jasper and calcite, red earth/ochre and calcite, and hematite were the colour forming minerals of pink coloured pigments.

  10. Mineralogical and Geochemical Characteristics of the Early Permian Upper No. 3 Coal from Southwestern Shandong, China

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    Xibo Wang

    2016-06-01

    Full Text Available The Upper No. 3 coal of the Early Permian age is a major workable seam in the southwestern Shandong coalfield, which is located in the eastern part of North China. From Early Jurassic to Neogene, the coalfield was subjected to intensive tectonic processes, leading to a significant rearrangement in depth of coal seams. In this paper, three Upper No. 3 coals occurring at −228, −670 and −938 m in the Luxi, Liangbaosi, and Tangkou mines, respectively, were collected to investigate their mineralogical and geochemical characteristics, with emphasis on modes of occurrence and origin of epigenetic minerals. The three coal seams are similar in vitrinite reflectance, volatile matter yield, and maceral components, suggesting insignificant influence from the tectonic activities on coal rank. Terrigenous minerals (e.g., kaolinite and quartz are comparable in both types and distribution patterns in the three coals. The presence of siderite and pyrite of syngenetic or penecontemporaneous origin indicate they were emplaced during peat accumulation. The distribution of epigenetic minerals (e.g., calcite, ankerite, and dolomite are associated with the underground water activities, which were Ca (Mg, Fe-bearing.

  11. Mineralization Zoning in Yindongzi—Daxigou Barite—Siderite,Silver—Polymetallic Deposits in the Qinling Orogen,China

    Institute of Scientific and Technical Information of China (English)

    方维萱; 胡瑞忠; 等

    2001-01-01

    The Yindongzi-Daxigou strata-bound barite-siderite,silver-polymetallic deposits discovered in the Qinling orogen are hosted within flysch facies in a deep-water fault-controlled basin on the passive northern margin of the Qinling microplate.The orebodies occur in a series of hydrothermal depositonal rocks.Mineralization zoning is characterized by Fe-Ba←Ba-Cu←Pb-Ab→Cu-Ag→Pb→Au.This is obviously a gradational transition mineralization from ventproximal mineralization to more distal mineralization.In this gradational transition between Chefanggou and Yindongzi,vent-proximal mineralization consists of silver-polymetallic orebodies(Pb-Ag),which is the center of hydrothermal mineralization.The Chefanggou Ba-Cu ore district in the west and the Yindongzi Cu-Ag ore district in the east represent vent lateral mineralization.Distal mineralization in the west is represented by the Daxigou Fe-Ba ore district while distal mineralization in te east is represented by the Pb ore district.Thick massive,laminated barren albite chert and jasperite,sometimes with minor silver-ploymetallic mineralization of commercial importance,and pyritization in rocks feature more distal mineralization.Geochemical anomalies of Au-As associations are found in ankerite phyllite and muddy sandstone.Actually,Au deposits are dominantly controlled by the late brittle-ductile shear zone.

  12. Mineralization Zoning in Yindongzi-Daxigou Barite-Siderite, Silver-Polymetallic Deposits in the Qinling Orogen, China

    Institute of Scientific and Technical Information of China (English)

    方维萱; 胡瑞忠; 黄转莹

    2001-01-01

    The Yindongzi-Daxigou strata-bound barite-siderite, silver-polymetallic deposits discovered in the Qinling orogen are hosted within flysch facies in a deep-water fault-controlled basin on the passive northern margin of the Qinling microplate. The orebodies occur in a series of hydrothermal depositional rocks. Mineralization zoning is characterized by Fe-Ba←Ba-Cu←Pb-Ag→Cu-Ag→Pb→Au. This is obviously a gradational transition mineralization from ventproximal mineralization to more distal mineralization. In this gradational transition between Chefanggou and Yindongzi, vent-proximal mineralization consists of silver-polymetallic orebodies (Pb-Ag), which is the center of hydrothermal mineralization. The Chefanggou Ba-Cu ore district in the west and the Yindongzi Cu-Ag ore district in the east represent vent lateral mineralization. Distal mineralization in the west is represented by the Daxigou Fe-Ba ore district while distal mineralization in the east is represented by the Pb ore district. Thick massive, laminated barren albite chert and jasperite, sometimes with minor silver-ploymetallic mineralization of commercial importance, and pyritization in rocks feature more distal mineralization. Geochemical anomalies of Au-As associations are found in ankerite phyllite and muddy sandstone.Actually, Au deposits are dominantly controlled by the late brittle-ductile shear zone.

  13. Hydrothermal Sedimentation Characteristics of the Dajiangping Superlarge Pyrite Deposit,Yunfu,Guangdong

    Institute of Scientific and Technical Information of China (English)

    陈多福; 陈光谦; 等

    1998-01-01

    The Dajiangping pyrite deposit is hosted in a carbonate-clastic rock series which is characterized by a bioreef-chert suite in its middle part.Conformable lenses of various sizes constitute the orebodies which often branch transitionally into the surroundings.Syngenetic deformation fabrics can be observed in orebody NO.3.Orebody No.4 is composed almost entirely of massive pyrite,with conspicuous hydrothermal sedimentation and bacterium-alga features.The hydrothermal sedimentation origin is also reflected by simple chemistry of the ore (predominated by quartz and pyrite),the presence of U and Th,and the REE compositions of pyrite and ankerite.The ores are rich in organic matter and the difference in organic content between the banded ores and the massive ores is mainly owing to the difference in the clastic components they contain rather than to the subsequent processes of reworking .Co/Ni rations in the ore may reflect the temperature pattern during hydrothermal sedimentation.

  14. A salt diapir-related Mississippi Valley-type deposit: the Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: fluid inclusion and isotope study

    Science.gov (United States)

    Bouhlel, Salah; Leach, David L.; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-08-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian-Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ˜110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the

  15. CO 2 degassing and trapping during hydrothermal cycles related to Gondwana rifting in eastern Australia

    Science.gov (United States)

    Uysal, I. Tonguç; Golding, Suzanne D.; Bolhar, Robert; Zhao, Jian-xin; Feng, Yue-xing; Baublys, Kim A.; Greig, Alan

    2011-10-01

    Intensive carbonate and clay mineral authigenesis took place throughout the Late Permian Bowen-Gunnedah-Sydney basin system in eastern Australia. We conducted isotopic and trace element analyses of carbonate and clay minerals from clastic sedimentary rocks of the Gunnedah Basin and the Denison Trough in the Bowen Basin. Rb-Sr isochron age data of the illitic clays are consistent with episodic hydrothermal fluid flow events that occurred in association with Gondwana rifting accompanied by alkaline magmatism at ˜85 Ma and ˜95 Ma. Stable isotope data of carbonate and clay minerals from the Gunnedah Basin are indicative of meteoric waters from a high-latitude environment as the main fluid source, whereas trace element, Sr and Nd isotope data highlight mixing of meteoric fluids with magmatic and/or crustal components, with a possible input from marine carbonates for some samples. Trace metals, oxygen and strontium isotopes of dawsonites from the Denison Trough are interpreted to have been mobilised by fluids that interacted with evolved clastic sedimentary and marine carbonate end members. According to the carbon isotope data, CO 2 for calcite and ankerite precipitation was sourced mainly from thermal degradation of organic matter and magmatism, whereas the CO 2 used for dawsonite formation is inferred to have been derived from magmatic and marine sources. In the low permeability environments (particularly in coal seams), the increasing accumulation and oversaturation of CO 2 particularly promote the precipitation of dawsonite.

  16. Formation mechanism of carbonate cemented zones adjacent to the top overpressured surface in the central Junggar Basin,NW China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Carbonate cemented zones are normally adjacent to the top overpressured surface in the central Junggar Basin,NW China.Stable carbon and oxygen isotopic compositions and petrological investigations of carbonate cements in the carbonate cemented zones indicate that:(1) carbonate cements are composed dominantly of ferrocalcite,ferroan dolomite,and ankerite;(2) carbonate cements are formed under a high temperature circumstance in the subsurface,and organic fluid migration has an important effect on the formation of them;and(3) carbon and oxygen ions in the carbonate cements migrate from the underlying overpressured system.This suggests that the occurrence of carbonate cemented zones in this region results from multiple phases of organic fluid expulsion out of the overpressure compartment through geological time.This study provides a plausible mechanism of the formation of carbonate cemented zones adjacent to the top overpressured surface in the clastic sedimentary basins,and has an important implication for understanding the internal correlation between the formation of carbonate cemented zones adjacent to top overpressured surface and geofluids expulsion out of overpressured system.

  17. Exploration for gold mineralization in the Arabo Nubian Shield: Using remote sensing Approach

    Science.gov (United States)

    Ramadan, Talaat

    2013-04-01

    In the southern part of the Eastern Desert of Egypt, Landsat Thematic Mapper (ETM+) data and fieldwork was combined with mineralogical and geochemical investigations in order to detect and characterize alteration zones within Pan-African rocks. The processing of Landsat ETM+ data using ratioing (bands 5/7,5/1,4/3 in Red, Green, Blue) showed two different types of alteration zones (type l and 2). Type 1 is close to the ophiolitic ultramafic rocks and type 2 is located within island-arc related metavolcanic rocks at the study areas. Both of these alteration zones are concordant with the main NW-SE structural trend. Mineralogical studies indicate that the alteration zones of type 1 consist mainly of calcite, ankerite, magnesite, dolomite and quartz. Chromian spinel, pyrite, and Ni-bearing sulphides (gersdorffite, pentlandite and polydymite) are the main ore minerals within this zone. Alteration zones of type 2 are strongly potassium-enriched and pyrophyllite, kaolinite, illite, gypsum and quartz occur. The brecciated quartz-veins associated with theses alteration zones consist of quartz, Fe-hydroxides, hematite and native gold. The gold content reaches up to 5 g/t in the alteration zone, while it extends up to 50 g/t in the quartz veins. This study presents a mineralogical characterization of such zones and demonstrates the utility of orbital remote sensing for finding unknown alteration zones in the Eastern Desert and other arid areas with similar host rock lithologies.

  18. Catalytic decarboxylations of fatty acids in immature oil source rocks

    Institute of Scientific and Technical Information of China (English)

    李哲; 张再龙; 孙燕华; 劳永新; 蔺五正; 吴卫芳

    2003-01-01

    Catalytic decarboxylations of fatty acids in immature oil source rock samples were examined in this study. The rock samples were obtained from seven oil fields in China. In order to clarify the effect of each mineral matter in the rock samples, both the Fe M?ssbauer effect and the X-ray diffraction (XRD) were used to determine the relative content of each mineral in the rock samples, and the catalytic activities of several minerals like clays, carbonates and pyrite were determined. The Fe M?ssbauer effect and the XRD studies show that clays are the main mineral components in the rock samples except for the samples from Biyang and Jianghan in which the main mineral component is ankerite. The other mineral components include calcite, plagioclase, quartz, feldspar, siderite, aragonite, pyrite, analcime, pyroxene and anhydrite. The studies of the catalytic decarboxylations of fatty acids suggest that carbonates and pyrite can make much greater contributions to the catalytic activities of the rock samples than clays. It is found that the overall catalytic activities of the rock samples are well related to the relative contents and the catalytic activities of clays, carbonates and pyrite in the rock samples.

  19. Fenitization of metabasic rocks by ferrocarbonatites at Haast River, New Zealand

    Science.gov (United States)

    Cooper, Alan F.; Palin, J. Michael; Collins, Alice K.

    2016-02-01

    Dolomite-ankerite-siderite ferrocarbonatite dykes of the Alpine Dyke swarm, Westland, New Zealand, intrude greenschist facies metabasites and produce carbonate-albite-muscovite-hematite-Nb-rutile and cancrinite-aegirine-carbonate fenites. The protolith foliation and metamorphic segregations are retained during fenitization despite complete mineralogical reconstitution. Quartz veins in metabasite are reconstituted to albite-aegirine-arfvedsonite/riebeckite assemblages. Geochemically the metabasites have been enriched in Na, C, Sr, Ba, Nb, Th and middle REE, and depleted in Fe, Ca, Mg, V, Cr, Ni, Zr and Hf, light- and heavy-REE. Si and Al show variable behaviour, with Si being consistently depleted in the generation of cancrinite fenite. The process approximates to an equal volume replacement. Field relationships of these dykes suggest that the carbonatites are the sole source of alkaline fenitizing fluids and that ferrocarbonatite magma was, therefore, considerably more sodic than the observed crystalline composition. Sr isotope ratios of fenite and carbonatite minerals indicate they have been partially modified by interaction with carbonatite-derived and schist-derived fluids respectively, and that fenitization, therefore, represents a two-way fluid infiltration. Carbonate minerals in fenite and carbonatite have been subsequently partially recrystallized during oxidation, highlighting the complex emplacement history involving carbonatite crystallization, fenitization and late-stage hydrothermal/carbothermal processes.

  20. 湖北庙垭碳酸岩地球化学特征及岩石成因探讨

    Institute of Scientific and Technical Information of China (English)

    李石

    1980-01-01

    The Miaoya carbonatite complex, occuring as lens, is located west of Wudon massif,Hupch Province, and consists of carbonatites and syenites associated with them. The carbonatites arc corapositionally classified into four types, i.e., sovite, alvikite, carbonbearing alvikitc and ankcritic carbonatite. Their average composition is in agreement with the abundance values for carbonatites compiled by Gokd (1966). Three stages can be recognized: the sevite and alvikite types are the earliest followed by carbonbearing alvikite type, while ankcritic carbonatite type is the latest. Some regularities are observed with respect to the distribution of major and rare elements during the evolution of carbonatites. For example, Nb is essentially enriched in sovite type.Except niobite and ilmenorutile, there are also pyrochlore, nioboesehynite and fersmite in it. RE is concentrated mainly in ankeritic carbonatite type, within which bastnasite,parisite and monazite are found. In general, Ca Nb, and Sr decrease, while Fe, Mg,Mn anal RE increase from earlier to later stages. It is suggested that the carbonatites were gew, geneticolly conneeted with syenitic magma.

  1. Automated mineralogical logging of coal and coal measure core

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Fraser; Joan Esterle; Colin Ward; Ruth Henwood; Peter Mason; Jon Huntington; Phil Connor; Reneta Sliwa; Dave Coward; Lew Whitbourn [CSIRO Exploration & Mining (Australia)

    2006-06-15

    A mineralogical core logging system based on spectral reflectance (HyLogger{trademark}) has been used to detect and quantify mineralogies in coal and coal measure sediments. The HyLogger{trademark} system, as tested, operates in the visible-to-shortwave infrared spectral region, where iron oxides, sulphates, hydroxyl-bearing and carbonate minerals have characteristic spectral responses. Specialized software assists with mineral identification and data display. Three Phases of activity were undertaken. In Phase I, carbonates (siderite, ankerite, calcite) and clays (halloysite, dickite) were successfully detected and mapped in coal. Repeat measurements taken from one of the cores after three months demonstrated the reproducibility of the spectral approach, with some spectral differences being attributed to variations in moisture content and oxidation. Also, investigated was HyLogger{trademark} ability to create a 'brightness-profile' on coal materials, and these results were encouraging. In Phase II, geotechnically significant smectitic clays (montmorillonite) were detected and mapped in cores of clastic roof and floor materials. Such knowledge would be useful for mine planning and design purposes. In Phase III, our attempts at determining whether phosphorus-bearing minerals such as apatite could be spectrally detected were less than conclusive. A spectral index could only be created for apatite, and the relationships between the spectrally-derived apatite-index, the XRD results and the analytically-derived phosphorus measurements were ambiguous.

  2. Tectonic hydrothermal gold mineralisation in the outboard zone of the Southern Alps, New Zealand

    International Nuclear Information System (INIS)

    Gold-bearing veins cut a belt of low-grade (pumpellyite-actinolite/greenschist facies) schist in the Ben Ohau Range to the east of the Main Divide, in the outboard zone of the Southern Alps continental collisional zone, New Zealand. The schist has been exposed along the currently active Ostler Fault system, which has had c. 5 km of reverse motion since the Pliocene. The veins consist of quartz, ankerite, calcite, chlorite, and pyrite, with minor chalcopyrite and galena. Hydrothermal chlorite contains about 490 ppm Zn, and the gold contains 3-5 wt% Ag. Hydrothermal alteration of host rock is minor apart from Sr enrichment (up to four times background). Fluid inclusions in quartz are aqueous with minor dissolved CO2 and salts (18O = +10 to +14; δ13C = -6 to -10 per thousand) are similar to data from economic metamorphogenic Au deposits of the nearby Otago Schist, but minor meteoric incursion may have occurred. Isotopic data are also similar to veins formed in the inboard zone of the Southern Alps orogen. The Ben Ohau veins demonstrate that gold can be concentrated in low-grade schists distant from the most active part of the hydrothermal system driven by continental collision. (author). 45 refs., 6 figs., 3 tabs

  3. Forms of Iron in the Phosphorites of Abu-Tartur Area, Egypt

    Institute of Scientific and Technical Information of China (English)

    BAIOUMY,H.M.

    2002-01-01

    The Campanian-Maastrichtian phosphatic deposits in Egypt, called the Duwi Formation, comprise a part of the extensive Middle East to North African phosphogenic province of Late Cretaceous to Paleogene age. The province holds the greatest accumulation of phosphorites in the geological history, possibly in excess of 70 billion metric tons. The phosphate resources in Egypt alone exceed 3 billion metric tons. Two-third of these three billions occur only in the Abu-Tartur area. Among the phosphorite deposits in Egypt, the phosphorites of the Abu-Tartur area are characterized by high contents of iron ranging from 3 % to 7% with an average of 5 %. The detailed mineralogical and geochemical studies on the Abu-Tartur phosphorites revealed that iron is found in the form of pyrite, ankerite, clay minerals, microinclusions, and iron oxide.Pyrite, which is the major fraction, occurs as filling cement and partial to complete replacement of phosphatic grains and confined to the fresh phosphorites while iron oxide occurs as cryptocrystalline aggregates of red to brown particles and is confined to the weathered outcrops. Exclusive relations between pyrite in the fresh phosphorite samples inside the Abu-Tartur mine and iron oxide in the equivalent horizon of the weathered exposure indicated that iron oxide was formed by the oxidation of pyrite as a result of weathering. All of these forms harm the quality of ore, manufacturing processes, and the produced phosphoric acid and fertilizers.

  4. Mineralogy and source rock evaluation of the marine Oligo-Miocene sediments in some wells in the Nile Delta and North Sinai, Egypt

    Science.gov (United States)

    El sheikh, Hassan; Faris, Mahmoud; Shaker, Fatma; Kumral, Mustafa

    2016-06-01

    This paper aims to study the mineralogical composition and determine the petroleum potential of source rocks of the Oligocene-Miocene sequence in the Nile Delta and North Sinai districts. The studied interval in the five wells can be divided into five rock units arranged from the top to base; Qawasim, Sidi Salem, Kareem, Rudeis, and Qantara formations. The bulk rock mineralogy of the samples was investigated using X-Ray Diffraction technique (XRD). The results showed that the sediments of the Nile Delta area are characterized by the abundance of quartz and kaolinite with subordinate amounts of feldspars, calcite, gypsum, dolomite, and muscovite. On the other hand, the data of the bulk rock analysis at the North Sinai wells showed that kaolinite, quartz, feldspar and calcite are the main constituents associated with minor amounts of dolomite, gypsum, mica, zeolite, and ankerite. Based on the organic geochemical investigations (TOC and Rock-Eval pyrolysis analyses), all studied formations in both areas are thermally immature but in the Nile delta area, Qawasim, Sidi Salem and Qantara formations (El-Temsah-2 Well) are organically-rich and have a good petroleum potential (kerogen Type II-oil-prone), while Rudeis Formation is a poor petroleum potential source rock (kerogen Type III-gas-prone). In the North Sinai area, Qantara Formation has a poor petroleum potential (kerogen Type III-gas-prone) and Sidi Salem Formation (Bardawil-1 Well) is a good petroleum potential source rock (kerogen Type II-oil-prone).

  5. A salt diapir-related Mississippi Valley-type deposit: The Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: Fluid inclusion and isotope study

    Science.gov (United States)

    Bouhlel, Salah; Leach, David; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-01-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian–Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ∼110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained

  6. Typomorpic Characteristics of the Major Minerals in the Puziwan Gold Deposit, Datong, Shanxi, China

    Institute of Scientific and Technical Information of China (English)

    QING Min; NIU Cuiyi; LEI Shibin

    2008-01-01

    Utilizing theories of minerageny and prospecting mineralogy, the authors studied theattitude, morphotype and chemical composition of metallic minerals of pyrite, gold, chalcopyrite,galena and sphalerite, non-metallic minerals of quartz, carbonate, dolomite and rutile in the Puziwangold deposit. The study shows the following results. (1) The mineral assemblage is complex and thespecies of sulfide are abundant with occurrences of sulfosalt minerals. (2) The composition in theminerals is complex and there rich micro elements, including As, Sb, Bi, Se, Te, Au, Ag, Cu, Pb, Zn, andCr, Ni, V. The typomorphic characteristics of the association of the elements and their specific valuesuggest that gold mineralization is associated with shallow magmatic hydrothermai activity, the ore-forming fluid is the mixture of abundant rising alkali magmatic water originating from the mantle orthe lower crust and the descending acid atmospheric water. (3) Ankerite, Fe-rich sphalerite, granularTi-rich rutile are widely distributed, which indicate great denudation depths, high mineralizationtemperature. The deposit is found in the middle and shallow positions of the porphyry series. The deeplayers are not favorable for gold mineralization. (4) Copper minerals are rich in the ores and sulfideshave high content of copper, suggesting possible porphyry-type Cu (Au) mineralization in deeppositions and the surrounding areas.

  7. Impact of depositional facies on the distribution of diagenetic alterations in the Devonian shoreface sandstone reservoirs, Southern Ghadamis Basin, Libya

    Science.gov (United States)

    Khalifa, Muftah Ahmid; Morad, Sadoon

    2015-11-01

    The middle Devonian, shoreface quartz arenites (present-day burial depths 2833-2786 m) are important oil and gas reservoirs in the Ghadamis Basin, western Libya. This integrated petrographic and geochemical study aims to unravel the impact of depositional facies on distribution of diagenetic alterations and, consequently, related reservoir quality and heterogeneity of the sandstones. Eogenetic alterations include the formation of kaolinite, pseudomatrix, and pyrite. The mesogenetic alterations include cementation by quartz overgrowths, Fe-dolomite/ankerite, and illite, transformation of kaolinite to dickite, illitization of smectite, intergranular quartz dissolution, and stylolitization, and albitization of feldspar. The higher energy of deposition of the coarser-grained upper shoreface sandstones combined with less extensive chemical compaction and smaller amounts of quartz overgrowths account for their better primary reservoir quality compared to the finer-grained, middle-lower shoreface sandstones. The formation of kaolin in the upper and middle shoreface sandstones is attributed to a greater flux of meteoric water. More abundant quartz overgrowths in the middle and lower shoreface is attributed to a greater extent of stylolitization, which was promoted by more abundant illitic clays. This study demonstrated that linking the distribution of diagenetic alterations to depositional facies of shoreface sandstones leads to a better understanding of the impact of these alterations on the spatial and temporal variation in quality and heterogeneity of the reservoirs.

  8. A salt diapir-related Mississippi Valley-type deposit: the Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: fluid inclusion and isotope study

    Science.gov (United States)

    Bouhlel, Salah; Leach, David L.; Johnson, Craig A.; Marsh, Erin; Salmi-Laouar, Sihem; Banks, David A.

    2016-01-01

    The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian-Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ˜110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the

  9. Palaeoredox indicators from the organic-rich Messinian early post-evaporitic deposits of the Apennines (Central Italy)

    Science.gov (United States)

    Sampalmieri, G.; Iadanza, A.; Cipollari, P.; Cosentino, D.; Lo Mastro, S.

    2009-04-01

    barren laminated sediments, hasn't been thoroughly clarified yet. The aim of the present study, dealing with messinian p-ev1 deposits from Marche and Maiella successions, is to provide more details in the definition of the environment developed during the early post-evaporitic phase. Since the lamination and the absence of benthic fauna suggest the occurrence of anoxic conditions, the following indirect proxies for the detection of organic matter have been investigated: 1) sedimentary fabric and microfacies; 2) framboidal pyrite size distribution; 3) natural radioactivity (authigenic uranium values, Th/U ratios). Natural radioactivity has been achieved through gamma spectrometry, with field and laboratory specific techniques. In the Maccarone section (Marche region), p-ev1 deposits are constituted by: barren greyish shales; laminated black shales interbedded with calcitic and ankeritic horizons; thin intercalations of sandstones. Organic-matter and framboidal pyrite commonly occur. Size analysis of framboids populations yielded a mean diameter of 4÷8 m, typical of disaerobic facies. Microfacies analysis yielded also the presence of crystals aggregates of barite, up to 50 m in size, and of isolated detrital (silicilastic) crystals. Without considering γ-ray values of the volcaniclastic layer (52-65 Cps) occurring within the p-ev1 interval, black shales horizons revealed the maximum natural radioactivity (NRD of about 50 Cps) recorded inthe studied section. Lower γ-activity characterizes the calcitic layers (i.e. "Colombacci") and the ankerites. Field NRD spectra acquired on different lithologies, showed variable contributions of 238U, 232Th and 40K. Both the blue-greyish shales and the black shales are characterized by total NRD related to the three main radioelements: 40K is associated to abundant 238U content (Thppm/Uppm 1). The 238U content is primarily referable to processes of organic matter enrichment (authigenic uranium) and secondarily to the input of

  10. Silver-rich telluride mineralization at Mount Charlotte and Au-Ag zonation in the giant Golden Mile deposit, Kalgoorlie, Western Australia

    Science.gov (United States)

    Mueller, Andreas G.; Muhling, Janet R.

    2013-03-01

    The gold deposits at Kalgoorlie in the 2.7-Ga Eastern Goldfields Province of the Yilgarn Craton, Western Australia, occur adjacent to the D2 Golden Mile Fault over a strike of 8 km within a district-scale zone marked by porphyry dykes and chloritic alteration. The late Golden Pike Fault separates the older (D2) shear zone system of the Golden Mile (1,500 t Au) in the southeast from the younger (D4) quartz vein stockworks at Mt Charlotte (126 t Au) in the northwest. Both deposits occur in the Golden Mile Dolerite sill and display inner sericite-ankerite alteration and early-stage gold-pyrite mineralization replacing the wall rocks. Late-stage tellurides account for 20 % of the total gold in the first, but for 30 g/t Au) is characterized by Au/Ag = 2.54 and As/Sb = 2.6-30, the latter ratio caused by arsenical pyrite. Golden Mile-type D2 lodes occur northwest of the Golden Pike Fault, but the Hidden Secret orebody, the only telluride bonanza mined (10,815 t at 44 g/t Au), was unusually rich in silver (Au/Ag = 0.12-0.35) due to abundant hessite. We describe another array of silver-rich D2 shear zones which are part of the Golden Mile Fault exposed on the Mt Charlotte mine 22 level. They are filled with crack-seal and pinch-and-swell quartz-carbonate veins and are surrounded by early-stage pyrite + pyrrhotite disseminated in a sericite-ankerite zone more than 6 m wide. Gold grade (0.5-0.8 g/t) varies little across the zone, but Au/Ag (0.37-2.40) and As/Sb (1.54-13.9) increase away from the veins. Late-stage telluride mineralization (23 g/t Au) sampled in one vein has a much lower Au/Ag (0.13) and As/Sb (0.48) and comprises scheelite, pyrite, native gold (830-854 fine), hessite, and minor pyrrhotite, altaite, bournonite, and boulangerite. Assuming 250-300 °C, gold-hessite compositions indicate a fluid log f Te2 of -11.5 to -10, values well below the stability of calaverite. The absence of calaverite and the dominance of hessite in the D2 lodes of the Mt Charlotte area

  11. Petrology And Geochemistry Of Barite Mineralisation Around Azara North Central Nigeria

    Directory of Open Access Journals (Sweden)

    Tanko

    2015-05-01

    Full Text Available ABSTRACT The Azara barite deposits formed parts of Middle Benue Trough which is located in an elongated rift or faulted-bounded mega structural depression trending NE-SW to a length of over 1000 km and a width of 100 km.Petrological and geochemical investigations of Azrara barite deposits were carried out. Eight 8 selected samples of barites were collected from the veins four from known veins V1V3V17 and V 18 and four from new veins VAVBVCand VD werecarried out with the aim of determining their mineralisation potentials using petrographic studies and gravimetric method of analyses. The Petrographic studies of some of the thin section of the samples conducted using a polarizing microscope to determine the contents distributions and textures of the various veins Table 1. The weight percentage composition of barite in the samples are V1 86.39 VC82.61 V1881.48 V3 81.17 V17 79.82 VA78.94 VB76.82 and VD 70.55 respectively. It is deduced from this work that the chemical weathering of the carbonates resulted in two distinct types of barites Barite associated with mainly quartz SiO2 and limonite FeOOH.nH2O as major gangue and barite with siderite Ferrous Carbonate with high amount of Mg ankerite Ca Fe Mg CO3 and Calcite CaCO3. The outcomes were compared with the barite specification of Weigal1937 of 95.00 and were found to be good for making drilling mud for use in the oil industry paints and other chemicals

  12. Microbial Mats in the Mesoproterozoic Carbonates of the North China Platform and Their Potential for Hydrocarbon Generation

    Institute of Scientific and Technical Information of China (English)

    Shi Xiaoying; Zhang Chuanheng; Jiang Ganqing; Liu Juan; Wang Yi; Liu Dianbo

    2008-01-01

    The well-preserved Mesoproterozoic succession in the North China platform consists mainly of three llthological associations including peritidal quartz sandstone, shallow marine and lagoonai dark to black shales, and shallow epeiric carbonates, with a total thickness of up to 8 000 m. In addition to well-documented microplants, macroalgae, and microbial buildups, abundant microbially induced sedimentary structures (MISS) and mat-related sediments have been recognized in these rocks. Intensive microbial mat layers and MISS are especially well preserved in the carbonates of the upper Gaoyuzhuang (高于庄) (ca. 1.5 Ga) and lower Wumishan (雾迷山) (ca. 1.45 Ga) formations, Indicating diversified microbial activities and a high organic production. In these petrified blomats, putative microbial fossils (both coccoidal and filamentous) and framboidal pyrites have been identified. The abundance of authigenic carbonate minerals in the host rocks, such as, acicular aragnnites, rosette barites, radial siderites, ankerites, and botryoidai carbonate cements, suggests authigenlc carbonate precipitation from anaerobic oxidation of methane (AOM) under anoxic/euxinic conditions. Warm climate and anoxic/euxinic conditions in the Mesoproterozoic oceans may have facilitated high microbial productivity and organic burial in sediments. Although authigenic carbonate cements may record carbonate precipitation from anaerobic methane oxidation, gas blister (or dome) structures may indicate gas release from active methanogenesls during shallow burial Bituminous fragments in mat-related carbonates also provide evidence for hydrocarbon generation. Under proper conditions, the Mesoproterozoic mat-rich carbonates will have the potential for hydrocarbon generation and serve as source rocks. On the basis of petrified biomats, a rough estimation suggests that the Mesoproterozoic carbonates of the North China platform might have a hydrocarbon production potential in theorder of 10×108t.

  13. Diagenesis and reservoir quality of the Lower Cretaceous Quantou Formation tight sandstones in the southern Songliao Basin, China

    Science.gov (United States)

    Xi, Kelai; Cao, Yingchang; Jahren, Jens; Zhu, Rukai; Bjørlykke, Knut; Haile, Beyene Girma; Zheng, Lijing; Hellevang, Helge

    2015-12-01

    The Lower Cretaceous Quantou Formation in the southern Songliao Basin is the typical tight oil sandstone in China. For effective exploration, appraisal and production from such a tight oil sandstone, the diagenesis and reservoir quality must be thoroughly studied first. The tight oil sandstone has been examined by a variety of methods, including core and thin section observation, XRD, SEM, CL, fluorescence, electron probing analysis, fluid inclusion and isotope testing and quantitative determination of reservoir properties. The sandstones are mostly lithic arkoses and feldspathic litharenites with fine to medium grain size and moderate to good sorting. The sandstones are dominated by feldspar, quartz, and volcanic rock fragments showing various stages of disintegration. The reservoir properties are quite poor, with low porosity (average 8.54%) and permeability (average 0.493 mD), small pore-throat radius (average 0.206 μm) and high displacement pressure (mostly higher than 1 MPa). The tight sandstone reservoirs have undergone significant diagenetic alterations such as compaction, feldspar dissolution, quartz cementation, carbonate cementation (mainly ferrocalcite and ankerite) and clay mineral alteration. As to the onset time, the oil emplacement was prior to the carbonate cementation but posterior to the quartz cementation and feldspar dissolution. The smectite to illite reaction and pressure solution at stylolites provide a most important silica sources for quartz cementation. Carbonate cements increase towards interbedded mudstones. Mechanical compaction has played a more important role than cementation in destroying the reservoir quality of the K1q4 sandstone reservoirs. Mixed-layer illite/smectite and illite reduced the porosity and permeability significantly, while chlorite preserved the porosity and permeability since it tends to be oil wet so that later carbonate cementation can be inhibited to some extent. It is likely that the oil emplacement occurred

  14. Linking mineral deposits to speleogenetic processes in Cova des Pas de Vallgornera (Mallorca, Spain

    Directory of Open Access Journals (Sweden)

    Bogdan P. Onac

    2014-05-01

    Full Text Available Cova des Pas de Vallgornera (CPV is the premier cave of the Balearic Archipelago. Over 74 km of passages develop within two carbonate lithofacies (reef front and back reef, which ultimately control the patterns of the cave and to some degree its mineral infilling. The diversity of speleothem-forming minerals is four times greater around or within hypogene-related features (vents, rims, cupolas, compared to any other vadose passages in the cave. The mineralogy of speleothems (crusts, nodules, crystals, earthy masses associated with hypogene features in the seaward upper maze of Sector F is characterized by the presence of aragonite, ankerite, huntite, clay minerals, and quartz. In the Tragus and Nord sectors, however, the dominant mineral is dolomite, along with aragonite, celestine, huntite, clay minerals, and quartz. Calcite is by far the most ubiquitous mineral throughout the cave. Detailed macroscopic and scanning electron microanalysis and imaging have permitted the investigation of textural relationships between the minerals associated with vents, rims, and vent’s roof and walls. These studies along with morphological and stable isotope analyses confirm that not all minerals are connected with a hypogene stage in the cave evolution, and furthermore, none of them appears to be sulfuric acid by-products. Instead, the mineral assemblages documented in speleothems from CPV clearly support at least three speleogenetic pathways, namely seacoast mixing, ascending of warm groundwaters, and meteoric recharge (vadose. Thus, cave minerals in Cova des Pas de Vallgornera hold the keys to reconstruction and understanding of processes and conditions under which they precipitated, allowing to establish their relationship with various speleogenetic pathways.

  15. Mineral matter in coals and their reactions during coking

    Energy Technology Data Exchange (ETDEWEB)

    Grigore, Mihaela; French, David [The Commonwealth Scientific and Industrial Research Organisation (CSIRO) - Energy Technology, Lucas Heights, NSW 2234 (Australia); Sakurovs, Richard [The Commonwealth Scientific and Industrial Research Organisation (CSIRO) - Energy Technology, Newcastle, NSW 2300 (Australia); Sahajwalla, Veena [School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia)

    2008-12-01

    Degradation of coke in the blast furnace is influenced by its inherent mineral matter, the formation of which is itself dependent upon the nature of the coal mineral matter. To date few studies have been made of coke mineralogy and its relationship to the mineralogy of the parent coal. In this study the effect of carbonisation on coal mineral matter has been investigated by a detailed quantitative mineralogical examination of nine cokes and their parent coals. The quantitative analysis was performed on X-ray diffraction patterns of the mineral matter of cokes and coals, using SIROQUANT {sup trademark}. Coke mineralogy and its composition varied strongly between cokes, more strongly than variations in elemental composition of the ash. The mineral matter in the studied cokes consisted of crystalline mineral phases and also significant levels of amorphous phase (ranging between 44 and 75%). Decomposition of clays such as kaolinite, montmorillonite, illite and chamosite produced the amorphous phase and some of the crystalline mineral phases such as mullite, {gamma}-alumina, spinel, cristobalite and leucite. The type of association of mineral matter in coals had an important role in how the clays decomposed. For example, association of kaolinite with silica-bearing minerals in intimate intermixture favoured formation of mullite over {gamma}-alumina. Akermanite and diopside result from reaction of kaolinite with associated calcium bearing minerals (calcite, dolomite or ankerite). Quartz, fluorapatite and the three polymorphs of TiO{sub 2} (anatase, brookite and rutile) were the coal minerals that were least affected during carbonisation, as they were also found in the cokes, yet even they were affected in some cases. (author)

  16. Processes of attenuation of dissolved arsenic downstream from historic gold mine sites, New Zealand.

    Science.gov (United States)

    Haffert, Laura; Craw, Dave

    2008-11-01

    Mine and processing sites in the mesothermal gold deposits of the Reefton gold field, New Zealand, generate extremely high dissolved As concentrations (up to 59 mg/L). Attenuation of these waters takes place by at least one of the three mechanisms: (1) precipitation of the secondary arsenic mineral scorodite, (2) chemisorption onto iron oxyhydroxide (HFO) and (3) dilution with regional catchment water. The presence and effectiveness of these mechanisms vary among the three studied catchments. A strong physiochemical control on arsenic attenuation was identified due to a chemical gradient within the gold field itself and processing methods, which can generate site specific arsenic minerals, such as arsenolite. Precipitation of scorodite only occurs in the presence of dissolving arsenolite, which is a roasting by-product present at two of the studied sites. Abundant HFO is generated in the pyritic mesothermal part of the gold field, and here chemisorption onto HFO is the dominant attenuation process. In the non-pyritic part of the gold field, HFO is mainly produced as a result of ankerite dissolution but only where sufficiently exposed mineralised rock is present. In the absence of significant adsorption sites, dissolved As is attenuated only via less effective dilution and ecosystem guidelines are exceeded over kilometres downstream from the mineralised zone until drainage waters are diluted by regional catchment water. Catchment morphology was identified as a major control on dilution. Despite the presence of strong As point sources upstream, mine-related As contributes <10% to the regional As river load in all three catchments. On a regional scale As mobility across a wide range of pH regimes reveals a strong control of scorodite, which has already been observed locally. PMID:18691740

  17. SHRIMP U-Pb ages of xenotime and monazite from the Spar Lake red bed-associated Cu-Ag deposit, western Montana: Implications for ore genesis

    Science.gov (United States)

    Aleinikoff, John N.; Hayes, Timothy S.; Evans, Karl V.; Mazdab, Frank K.; Pillers, Renee M.; Fanning, C. Mark

    2012-01-01

    Xenotime occurs as epitaxial overgrowths on detrital zircons in the Mesoproterozoic Revett Formation (Belt Supergroup) at the Spar Lake red bed-associated Cu-Ag deposit, western Montana. The deposit formed during diagenesis of Revett strata, where oxidizing metal-bearing hydrothermal fluids encountered a reducing zone. Samples for geochronology were collected from several mineral zones. Xenotime overgrowths (1–30 μm wide) were found in polished thin sections from five ore and near-ore zones (chalcocite-chlorite, bornite-calcite, galena-calcite, chalcopyrite-ankerite, and pyrite-calcite), but not in more distant zones across the region. Thirty-two in situ SHRIMP U-Pb analyses on xenotime overgrowths yield a weighted average of 207Pb/206Pb ages of 1409 ± 8 Ma, interpreted as the time of mineralization. This age is about 40 to 60 m.y. after deposition of the Revett Formation. Six other xenotime overgrowths formed during a younger event at 1304 ± 19 Ma. Several isolated grains of xenotime have 207Pb/206Pb ages in the range of 1.67 to 1.51 Ga, and thus are considered detrital in origin. Trace element data can distinguish Spar Lake xenotimes of different origins. Based on in situ SHRIMP analysis, detrital xenotime has heavy rare earth elements-enriched patterns similar to those of igneous xenotime, whereas xenotime overgrowths of inferred hydrothermal origin have hump-shaped (i.e., middle rare earth elements-enriched) patterns. The two ages of hydrothermal xenotime can be distinguished by slightly different rare earth elements patterns. In addition, 1409 Ma xenotime overgrowths have higher Eu and Gd contents than the 1304 Ma overgrowths. Most xenotime overgrowths from the Spar Lake deposit have elevated As concentrations, further suggesting a genetic relationship between the xenotime formation and Cu-Ag mineralization.

  18. Origin of carbonate concretions from mud mounds in the Gulf of Cadiz (SW Iberian Peninsula); Origen de las concreciones carbonatadas de los monticulos de fango en el Golfo de Cadiz (SO Peninsula Iberica)

    Energy Technology Data Exchange (ETDEWEB)

    Rejas, M.; Taberner, C.; Pueyo, J. J.; Giralt, S.; Mata, M. P.; Gibert, J. M. de; Diaz del Rio, V.

    2015-07-01

    The Gulf of Cadiz displays a number of structures that are associated with fluid circulation (mud volcanoes, mud mounds and pockmarks).This area has been used as natural laboratory for the sedimentological, bio- logical and biogeochemical studies of these environments. Analysis of the associated authigenic carbonates has been widely used as a proxy to yield insights into the circulation and chemical composition of these flu- ids. A study of carbonate concretions from the Iberico, Cornide and Arcos mud mounds in the Diasom Field was undertaken to better understand the origin and type of fluids from which these concretions precipitated. The concretions display varying morphologies, some of which correspond to bioturbation traces. X-ray dif- fractions revealed that these carbonate concretions are mainly composed of dolomite, Fe-rich dolomite, high magnesium calcite (HMC) and ankerite. The δ{sup 1}3 C values of carbonate minerals ranged between -48.3 and-10.9 V-PDB, which suggests that the main processes involved in their genesis are organic matter oxidation, bac- terial sulphate-reduction (BSR) and anaerobic methane oxidation (AOM). The origin of the methane is main- ly thermogenic, and only few concretions yielded δ{sup 1}3C values lower than -40 V-PDB, suggesting oxidation of microbial methane. Fluids involved in the carbonate precipitation are interpreted as being related to gas hydrate destabilisation (δ{sup 18}O fluid-V-SMOW values higher than +2%) and, to a lesser extent, modified seawater enriched in {sup 18}O due to rock-water interaction. Nevertheless, the highest δ{sup 1}8O fluid-V-SMOW values suggest that the influence of other deep-seated fluids due to clay-mineral dehydration cannot be ruled out. (Author)

  19. Vein mineralizations - record of paleo-fluid systems in the Thuringian basin (Germany)

    Science.gov (United States)

    Lepetit, Petra; Viereck, Lothar; Abratis, Michael; Fritsch, Stefanie

    2014-05-01

    Vein-related mineralizations within the Mesozoic sediments of the Thuringian basin (Germany) are investigated in analytical detail (petrography, XRD, XRF, EPMA, LA-ICP-MS, and isotope studies: O, C, S, Sr) in order to characterize paleo-fluid systems that intruded the basin and circulated within it millions of years ago. Samples from 55 outcrops, 34 quarries and 21 drill cores comprise mainly carbonates (calcite, dolomite, siderite, ankerite), additional sulfates (gypsum, celestine, barite,), and rarely sulfides. The mineralizations are almost exclusively restricted to WNW-ESE trending fault systems. First δ13C and δ18O isotope analyses of calcite mineralizations reveal differences between veins within Triassic sediments (Lower Muschelkalk: δ13C: 1.8 to 2.9 o, mean 2.3 o, δ18O: -7.3 to -10.4 o, mean -8.2 o) and Jurassic sediments (δ13C: -0.7 to -2.1 o, mean -1.4 o, δ18O: -9.3 to -10.6 o, mean -9.9 o), indicating intra-formational and extra-formational paleo-fluid transport. Also first δ34S and δ18O isotope analyses of gypsum mineralizations display differences between veins within Triassic and Permian sediments, respectively. These initial data are comparable with isotope analyses of vein-related host rocks and hydrochemical signatures of recent well waters in the Thuringian basin indicating intra-formational in addition to extra-formational paleo-fluid transport. Further isotope studies are in progress including high resolution in situ-Sr- isotope analysis. The present study is part of INFLUINS, a BMBF-funded project bundle, which is dedicated to the comprehensive description and understanding of the fluid systems within the Thuringian basin in time and space.

  20. River water quality in weathered limestone: A case study in upper Mahanadi basin, India

    Indian Academy of Sciences (India)

    B K Panigrahy; B C Raymahashay

    2005-10-01

    Stromatolitic limestone and calcareous shale belonging to Chattisgarh Supergroup of Proterozoic age dominate the upper part of the Mahanadi river basin.X-ray diffractogram (XRD)of limestone rocks show presence of a significant amount of calcite,dolomite and ankerite.Shales of various colours contain calcite and dolomite.It is observed that congruent dissolution of carbonate minerals in the Charmuria pure limestone has given rise to a typical karst topography.On the other hand, limestones are also seen to support red and black soil pro files.This indicates that the limestone bedrock undergoes a parallel incongruent weathering,which leaves a residue of decomposed rock. The XRD analyses reveal that the limestone soils thus formed contain an assemblage of quartz,clays and Fe-oxides.It is likely that the silicate component trapped during deposition of the stromatolitic limestone weathers incongruently resulting in diverse soil profiles.Carbonate and silicate mineral weathering schemes have been worked out to explain the soil formation,fixation of Al in clay minerals, and Fe in goethite.The water quality parameters such as Ca, Mg and HCO3 in the river water suggest under saturation with respect to calcite and dolomite.The mineral stability diagrams indicate that kaolinite and Ca-smectite are stable in the river water environment,hence they occur in suspended sediments and soils.The dominant influence of carbonate weathering on the water quality is observed even in the downstream part of the river outside the limestone terrain.

  1. Carrick Range Au and Sb mineralisation in Caples Terrane, Otago Schist, Central Otago, New Zealand

    International Nuclear Information System (INIS)

    Mineralised zones of the Carrick Range, bearing gold and stibnite veins, constitute one of the rare economically significant mineralised fields in the Caples Terrane. The mineralised zones have a polyphase hydrothermal history. Early low-angle shears are filled by milky quartz, with minor carbonate, sulphides, and gold. These are cut by steeply dipping hydrothermal breccias and veins with prismatic and fine-grained chalcedonic quartz ± carbonate (calcite and ankerite). Gold is associated with some high-angle mineralised zones, and stibnite with spatially separated but texturally similar high-angle zones. Fluid inclusions in early milky quartz homogenise mainly between 145 degrees C and 210 degrees C, with some higher temperature homogenisation up to 300 degrees C. Late prismatic quartz has inclusions that homogenise at 150-170 degrees C, and ice-melting temperatures suggest low salinity (2.4-4.8 wt% NaCl equivalent). Oxygen isotopic ratios of early milky quartz range from δ18O = +15.4 to +17.6 per mille, whereas fine-grained late quartz ranges from +13.4 to +22.8 per mille. Vein carbonates have δ18O between +13.8 and +19.9 per mille, and δ13C between -1.6 and -3.6 per mille. The isotopic data, combined with other geological and mineralogical evidence, imply that mineralisation occurred over a wide range of temperature (140-400 degrees C) with a fluid of constant isotopic composition similar to typical Otago Schist metamorphic fluid. Sulphide sulphur isotopic ratios fall in a narrow range of δ34S = -1.6 to +2.6 per mille, consistent with a homogenised crustal sulphur source. Late stage mineralisation occurred at shallow crustal levels (upper 2 km?), but earlier mineralisation was probably deeper. Mineralisation may have occurred sporadically, or as a continuous event during progressive uplift, during Cretaceous and/or early Miocene extensional tectonics. (author). 42 refs., 12 figs., 2 tabs

  2. Oscillation of mineral compositions in Core SG-1b, western Qaidam Basin, NE Tibetan Plateau

    Science.gov (United States)

    Fang, Xiaomin; Li, Minghui; Wang, Zhengrong; Wang, Jiuyi; Li, Jiao; Liu, Xiaoming; Zan, Jinbo

    2016-09-01

    Uplift of the Tibetan Plateau since the Late Miocene has greatly affected the nature of sediments deposited in the Qaidam Basin. However, due to the scarcity of continuously dated sediment records, we know little about how minerals responded to this uplift. In order to understand this response, we here present results from the high-resolution mineral profile from a borehole (7.3-1.6 Ma) in the Basin, which shows systematic oscillations of various evaporite and clay minerals that can be linked to the variation of regional climate and tectonic history. In particular, x-ray diffraction (XRD) analyses show that carbonate minerals consist mainly of calcite and aragonite, with minor ankerite and dolomite. Evaporates consist of gypsum, celesite and halite. Clay minerals are principally Fe-Mg illite, mixed layers of illite/smectite and chlorite, with minor kaolinite and smectite. Following implications can be drawn from the oscillations of these minerals phases: (a) the paleolake was brackish with high salinity after 7.3 Ma, while an abrupt change in the chemical composition of paleolake water (e.g. Mg/Ca ratio, SO42- concentration, salinity) occurred at 3.3 Ma; (b) the three changes at ~6.0 Ma, 4.5-4.1 Ma and 3.3 Ma were in response to rapid erosions/uplift of the basin; (c) pore water or fluid was Fe/Mg-rich in 7.3-6.0 Ma, Mg-rich in 6.0-4.5 Ma, and K-rich in 4.1-1.6 Ma and (d) evaporation rates were high, but weaker than today’s.

  3. Mineralogical and chemical analyses of ancient glass beads from Taiwan and their implications

    Science.gov (United States)

    Liou, Y. S.; Liu, Y. C.

    2015-12-01

    Large numbers of monochrome glass beads with different colors, shapes, and stylistics excavated from the archaeological sites of Taiwan, which were dated mainly from the 2nd century AD to the early Historical Period of Taiwan. Archaeologically, these glass beads were more prevalent in eastern and northern Taiwan and were generally believed to be non-native, as well as were brought into Taiwan through the maritime exchange and/or trade activities between Taiwan and Southeast Asia/China since the Neolithic Age. Nevertheless, ancient glass beads have been little studies in Taiwan, aspects of these glass beads are not well detailed. In this work, non-destructive micro-Raman spectroscopy and μXRF are used in combination to examine 56 ancient glass beads excavated from six archaeological sites, eastern Taiwan, to unravel the mineralogical and chemical compositions and to help decipher the raw materials used and the provenance of beads. Micro-Raman measurements indicate the presence of hematite, zincite, siderite, sphalerite, lead tin yellow type II, adularia, chalcedony, anatase, rutite, ankerite, graphite, calcite, etc. Hematite, zincite, siderite, sphalerite, lead tin yellow type II, and rutile were found to be colorants/opacifiers. Among these crystalline phases, lead tin yellow type II was first detected in the ancient glass bead unearthed from Taiwan, which is accordant with results of chemical analysis. The chemical results obtained by μXRF show SiO2, Al2O3, Na2O, K2O, MgO, CaO, and PbO as the most abundant oxides. It is found that Na2O, Na2O, K2O, Al2O3, and MgO are the main/minor fluxes. According to the results, the three most frequent types are mineral soda alumina glass, soda plant ash glass, and lead silicate glass. The provenance of ancient beads unearthed from archaeological sites of Taiwan is possibility of multiple sources.

  4. Structure and geochemistry of the Rise and Shine Shear Zone mesothermal gold system, Otago Schist, New Zealand

    International Nuclear Information System (INIS)

    The Rise and Shine Shear Zone is a late metamorphic deformation zone developed in biotite zone Textural Zone 4 schist in Central Otago. The shear zone has been hydrothermally altered, with addition of gold associated with replacement of schist minerals by pyrite and arsenopyrite. Hydrothermal alteration of schist during mineralisation involved replacement of titanite by rutile, recrystallisation of metamorphic quartz, muscovite and chlorite, and addition of ankerite. Mineralised schist has abundant microshears that have developed parallel and subparallel to the pervasive schist foliation, and these microshears contain much of the hydrothermal sulfides and gold. Microshears have been deformed locally by upright syn-mineralisation brittle reverse faults and angular folds that have a southerly axial trend. These more brittle deformation zones are confined to the Rise and Shine Shear Zone. Gold-bearing veins and mineralised breccias, made up of quartz, albite, pyrite, arsenopyrite, calcite, and chlorite, fill extensional sites associated with upright fold zones. Calcite delta18OVSMOW from these late-stage mineralised veins ranges from +7 to +15 per mille and δ13CPDB from -5.3 to -6.6 per mille, are similar to many other gold-bearing vein systems in Otago, but are distinctly different from the Macraes deposit. Mineralisation occurred near to the brittle/ductile transition, at 200-400 degrees C. The upper part of the shear zone was truncated by a shallow northeast-dipping normal fault, the Thomsons Gorge Fault, which juxtaposed shear zone rocks against unmineralised Textural Zone 3 chlorite zone rocks in the middle Cretaceous. The Rise and Shine Shear Zone has some structural and geochemical features in common with the Hyde-Macraes Shear Zone, but also some important differences, and is not a simple strike-extension of that structure. (author). 46 refs., 9 figs., 3 tabs

  5. Evolution of pores and fractures in an unconventional Upper Carboniferous reservoir analogue, Westphalian D, W-Germany

    Energy Technology Data Exchange (ETDEWEB)

    Hoehne, M.; Schurk, K.; Hilgers, C. [RWTH Aachen Univ. (Germany). Reservoir-Petrology, Energy and Mineral Resources Group (EMR); Koehrer, B. [Wintershall Holding GmbH, Barnstorf (Germany); Bertier, P. [RWTH Aachen Univ. (Germany). Inst. of Clay and Interface Mineralogy

    2013-08-01

    Uncertainties in reservoir characterization of tight gas sandstones can be significantly reduced by using quantitative data from outcrops. The active Piesberg quarry near Osnabrueck exposes Upper Carboniferous strata and therefore provides a reservoir outcrop analog to the gas-bearing tight gas fields in NW-Germany. This study focused on variations of sedimentary facies, porosity, diagenesis and structural inventory in the quarry. The Westphalian D strata at Piesberg consist of siliciclastic, coarse- to fine-grained sandstones with a strong cementation, intercalated with coal seams, siltstones and mudstones. Petrography shows shale-, mudstone and clay rip-up fragments squeezed into primary porosity during eodiagenesis. Sandstone types commonly show low porosities (<10 %) and very low permeabilities (<0.01 mD) mainly due to intense quartz cementation. Scarce authigenic carbonates are euhedral ankerites formed during burial. Secondary porosity resulted mostly from detrital carbonate leaching and limited dissolution of feldspars. Within a zone of up to several meters around faults, porosity is much higher. Feldspars are almost completely altered to illite and locally to kaolinite. Partly dissolved detrital carbonates show Fe-oxide margins around intragranular pores, indicative of Fe-rich compositions formed during telo-diagenesis. Both joints and faults were mapped throughout the quarry and strike, slip and throw of the latter were documented. Cemented fractures prevail around faults and may thus be associated with the structural and diagenetic evolution of the Upper Carboniferous of the Piesberg area. This study is embedded into a larger outcrop analog study of RWTH Aachen in cooperation with Wintershall. Its aim is to unravel the impact of structural diagenesis on the alteration and evolution of pore space and thus reservoir quality. Results can be used to develop datadriven exploration strategies and improved development options for analogous subsurface tight gas

  6. Forms of Iron in the Phosphorites of Abu—Tartur Area,Egypt

    Institute of Scientific and Technical Information of China (English)

    BAIOUM.H.M.

    2002-01-01

    The Campanian-Maastrichtian phosphatic deposits in Egypt,called the Duwi Forma-tion,comprise a part of the extensive Middle East to North African phosphogenic province of Late Cretaceous to Paleogene age.The province holds the greatest accumulation of phosphorites in the geological history,possibly in excess of 70 billion metric tons.The phosphate resources in Egypt alone exceed 3 billion metric tons.Two-third of these three billions occur only in the Abu-Tartur area.Among the phosphorite deposits in Egypt,the phosphorites of the Abu-Tartur area are characterized by high contents of iron ranging from 3% to 7% with an average of 5%.The detailed mineralogical and geochemical studies on the Abu-Tartur phosphorites revealed that iron is found in the form of pyrite,ankerite,clay minerals,microinclusions,and iron oxide.Pyrite,which is the major fraction,occurs as filling cement and partial to complete teplacement of phosphatic grains and confined to the fresh phosphorites while iron oxide occurs as cryp-tocrystalline aggregates of red to brown particles and is confined to the weathered outcrops.Ex-clusive relations between pyrite in the fresh phosphorite samples inside the Abu-Tartur mine and iron oxide in the equivalent horizon of the weathered exposure indicated that iron oxide was formed by the oxidation of pyrite as a result of weathering.All of these forms harm the quality of ore,manufacturing processes,and the produced phosphoric acid and fertilizers.

  7. Geochemistry and Age Dating of Ancient and Modern CO2 -rich Hydrothermal Systems as Natural Analogues for CO2 storage: Examples from Australia and Eastern Mediterranean

    Science.gov (United States)

    Uysal, I.; Golding, S.; Esterle, J.; Feng, Y.; Zhao, J.

    2008-12-01

    We investigated physico-chemical conditions during mineral authigenesis in CO2-rich ancient and recent hydrothermal environments in Eastern Australia (Gunnedah and Bowen Basins) and Turkey, respectively. We performed Rb-Sr and U-series dating of clay-carbonate associations and travertine veins respectively to evaluate the degassing and storage history of CO2. Intense carbonate veining and coal seam cleat mineralisation in the Gunnedah Basin took place as a result of heat and CO2 release associated with magmatism during the breakup of Gondwana in the Late Cretaceous. Widespread carbonate veining and cementation in the Bowen Basin occurred as products of basin-wide CO2 rich meteoric hydrothermal fluids during the Late Triassic extension. CO2 has largely been used for carbonate precipitation (calcite, siderite, ankerite and dawsonite) in eastern Australian basins; however, some high proportion of CO2 has been stored in coal seams as adsorbed molecules on coal. Significant CO2 degassing is common in geothermal fields in Turkey, as manifested by recent deposition of travertine pools and terraces as well as travertine vein networks in damage zones of active major fault systems. Trace element geochemistry indicates that transient ascent of CO2-bearing fluids during seismic strain cycles without significant interaction with basement and host rocks resulted in rapid precipitation of the vein travertine near the surface. Such veins and associated breccias formed by hydraulic fracturing in response to overpressure of CO2-rich fluids. Correlation of high-precision U-series ages with global/regional climate events indicates that late Quaternary climate variability may have controlled the geothermal water circulation that regulates CO2 accumulation and the generation of CO2 over-pressurised reservoirs and their behaviour during seismic events.

  8. Origin of carbonate concretions from mud mounds in the Gulf of Cadiz (SW Iberian Peninsula)

    International Nuclear Information System (INIS)

    The Gulf of Cadiz displays a number of structures that are associated with fluid circulation (mud volcanoes, mud mounds and pockmarks).This area has been used as natural laboratory for the sedimentological, bio- logical and biogeochemical studies of these environments. Analysis of the associated authigenic carbonates has been widely used as a proxy to yield insights into the circulation and chemical composition of these flu- ids. A study of carbonate concretions from the Iberico, Cornide and Arcos mud mounds in the Diasom Field was undertaken to better understand the origin and type of fluids from which these concretions precipitated. The concretions display varying morphologies, some of which correspond to bioturbation traces. X-ray dif- fractions revealed that these carbonate concretions are mainly composed of dolomite, Fe-rich dolomite, high magnesium calcite (HMC) and ankerite. The δ13 C values of carbonate minerals ranged between -48.3 and-10.9 V-PDB, which suggests that the main processes involved in their genesis are organic matter oxidation, bac- terial sulphate-reduction (BSR) and anaerobic methane oxidation (AOM). The origin of the methane is main- ly thermogenic, and only few concretions yielded δ13C values lower than -40 V-PDB, suggesting oxidation of microbial methane. Fluids involved in the carbonate precipitation are interpreted as being related to gas hydrate destabilisation (δ18O fluid-V-SMOW values higher than +2%) and, to a lesser extent, modified seawater enriched in 18O due to rock-water interaction. Nevertheless, the highest δ18O fluid-V-SMOW values suggest that the influence of other deep-seated fluids due to clay-mineral dehydration cannot be ruled out. (Author)

  9. Carbon and oxygen isotopic composition of carbonate cements of different phases in terrigenous siliciclastic reservoirs and significance for their origin: A case study from sandstones of the Triassic Yanchang Formation, southwestern Ordos Basin,China

    Institute of Scientific and Technical Information of China (English)

    WANG Qi; ZHUO Xizhun; CHEN Guojun; LI Xiaoyan

    2008-01-01

    Early carbonate cements in the Yanchang Formation sandstones are composed mainly of calcite with relatively heavier carbon isotope (their δ18O values range from -0.3‰-0.1‰) and lighter oxygen isotope (their ‰18O values range from -22.1‰--19.5‰). Generally, they are closely related to the direct precipitation of oversaturated calcium carbonate from alkaline lake water. This kind of cementation plays an important role in enhancing the anti-compaction ability of sandstones, preserving intragranular volume and providing the mass basis for later dissolution caused by acidic fluid flow to produce secondary porosity. Ferriferous calcites are characterized by relatively light carbon isotope with δ13C values ranging from -8.02‰ to -3.23‰, and lighter oxygen isotope with δ18O values ranging from -22.9‰ to -19.7‰, which is obviously related to the decarboxylation of organic matter during the late period of early diagenesis to the early period of late diagenesis. As the mid-late diagenetic products, ferriferous calcites in the study area are considered as the characteristic authigenic minerals for indicating large-scaled hydrocarbon influx and migration within the clastic reservoir. The late ankerite is relatively heavy in carbon isotope with δ13C values ranging from -1.92‰ to -0.84‰, and shows a wide range of variations in oxygen isotopic composition, with δ18O values ranging from -20.5‰ to -12.6‰. They are believed to have nothing to do with decarboxylation, but the previously formed marine carbonate rock fragments may serve as the chief carbon source for their precipitation, and the alkaline diagenetic environment at the mid-late stage would promote this process.

  10. Origin of alternate amphibole and quartz rich bands in amphibole bearing quartzite from North Khetri Copper Belt, Rajasthan, India

    Science.gov (United States)

    Paul, J.; Baidya, A. S.; Pal, D. D. C.

    2015-12-01

    form new carbonate minerals which are also common in this area in the form of ankerite/dolomite veins. The probable reaction will be [(1.5+x)Fe2+ + 0.5Fe3+ + 2OH-]fluid + [(3.5-x)Mg2+ +3Ca2++ 2CO32-]cb + [7Si4+ + 2Al3+ + 22O2-]qz-ab unit = [Ca2Mg2.5Fe2+1.5Fe3+0.5Al1.5Si7O22(OH)2]amp + [Ca(Mg1-x, Fe2+x)(CO3)2]ank/dol veins

  11. Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings

    Science.gov (United States)

    Huang, Longbin; Li, Xiaofang; Nguyen, Tuan A. H.

    2015-01-01

    Elevated inorganic phosphate (Pi) concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu)-lead (Pb)-zinc (Zn) mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7), the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5), EHM-TD (fresh Cu-stream, high magnetite content) and local soil (weathered shale and schist), respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed), oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2), ankerite (Ca(Fe Mg)(CO3)2 and siderite (FeCO3), as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,Fe)S, ZnS, (Zn,Cd)S)) may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal. PMID

  12. On the potential for CO2 mineral storage in continental flood basalts – PHREEQC batch- and 1D diffusion–reaction simulations

    Directory of Open Access Journals (Sweden)

    Van Pham Thi

    2012-06-01

    Full Text Available Abstract Continental flood basalts (CFB are considered as potential CO2 storage sites because of their high reactivity and abundant divalent metal ions that can potentially trap carbon for geological timescales. Moreover, laterally extensive CFB are found in many place in the world within reasonable distances from major CO2 point emission sources. Based on the mineral and glass composition of the Columbia River Basalt (CRB we estimated the potential of CFB to store CO2 in secondary carbonates. We simulated the system using kinetic dependent dissolution of primary basalt-minerals (pyroxene, feldspar and glass and the local equilibrium assumption for secondary phases (weathering products. The simulations were divided into closed-system batch simulations at a constant CO2 pressure of 100 bar with sensitivity studies of temperature and reactive surface area, an evaluation of the reactivity of H2O in scCO2, and finally 1D reactive diffusion simulations giving reactivity at CO2 pressures varying from 0 to 100 bar. Although the uncertainty in reactive surface area and corresponding reaction rates are large, we have estimated the potential for CO2 mineral storage and identified factors that control the maximum extent of carbonation. The simulations showed that formation of carbonates from basalt at 40 C may be limited to the formation of siderite and possibly FeMg carbonates. Calcium was largely consumed by zeolite and oxide instead of forming carbonates. At higher temperatures (60 – 100 C, magnesite is suggested to form together with siderite and ankerite. The maximum potential of CO2 stored as solid carbonates, if CO2 is supplied to the reactions unlimited, is shown to depend on the availability of pore space as the hydration and carbonation reactions increase the solid volume and clog the pore space. For systems such as in the scCO2 phase with limited amount of water, the total carbonation potential is limited by the amount of water present

  13. Authigenic carbonates related to active seepage of methane-rich hot brines at the Cheops mud volcano, Menes caldera (Nile deep-sea fan, eastern Mediterranean Sea)

    Science.gov (United States)

    Pierre, Catherine; Bayon, Germain; Blanc-Valleron, Marie-Madeleine; Mascle, Jean; Dupré, Stéphanie

    2014-06-01

    On the passive margin of the Nile deep-sea fan, the active Cheops mud volcano (MV; ca. 1,500 m diameter, ~20-30 m above seafloor, 3,010-3,020 m water depth) comprises a crater lake with hot (up to ca. 42 °C) methane-rich muddy brines in places overflowing down the MV flanks. During the Medeco2 cruise in fall 2007, ROV dives enabled detailed sampling of the brine fluid, bottom lake sediments at ca. 450 m lake depth, sub-surface sediments from the MV flanks, and carbonate crusts at the MV foot. Based on mineralogical, elemental and stable isotope analyses, this study aims at exploring the origin of the brine fluid and the key biogeochemical processes controlling the formation of these deep-sea authigenic carbonates. In addition to their patchy occurrence in crusts outcropping at the seafloor, authigenic carbonates occur as small concretions disseminated within sub-seafloor sediments, as well as in the bottom sediments and muddy brine of the crater lake. Aragonite and Mg-calcite dominate in the carbonate crusts and in sub-seafloor concretions at the MV foot, whereas Mg-calcite, dolomite and ankerite dominate in the muddy brine lake and in sub-seafloor concretions near the crater rim. The carbonate crusts and sub-seafloor concretions at the MV foot precipitated in isotopic equilibrium with bottom seawater temperature; their low δ13C values (-42.6 to -24.5‰) indicate that anaerobic oxidation of methane was the main driver of carbonate precipitation. By contrast, carbonates from the muddy lake brine, bottom lake concretions and crater rim concretions display much higher δ13C (up to -5.2‰) and low δ18O values (down to -2.8‰); this is consistent with their formation in warm fluids of deep origin characterized by 13C-rich CO2 and, as confirmed by independent evidence, slightly higher heavy rare earth element signatures, the main driver of carbonate precipitation being methanogenesis. Moreover, the benthic activity within the seafloor sediment enhances aerobic

  14. An integrated geochemical, geophysical and mineralogical study of river sediments in alpine area and soil samples near steel plant, in Austria

    Science.gov (United States)

    Irfan, M. I.; Meisel, T.

    2012-04-01

    , ankerite, corundum (anthropogenic), garnet, chlorite, titanium oxide minerals (ilmenite, rutile, titanite) and amphibole etc. The observed significant increase in heavy metal content from the source region of the Vordernberger Bach at 1500 m above sea level to the confluence of the Vordernberger Bach with the Mur River at 540 m AMSL can be attributed to anthropogenic influence. As expected, the anthropogenic input is more pronounced in the vicinity of historic and current iron and steel production.

  15. Optical microscope and SEM evaluation of roofing slate fissility and durability

    Directory of Open Access Journals (Sweden)

    Ward, C. R.

    2009-12-01

    Full Text Available The fissility and durability of representative samples of commercial roofing slates from ten deposits in the NW of Spain have been evaluated using transmitted and reflectedlight optical microscopy, scanning electron microscopy, chemical testing and geomechanical procedures. The dominant sulphides in the different slate samples are pyrite and pyrrhotite, the weathering potential of which can be highly variable. The dominant carbonate mineral is ankerite, which explains the low reactivity of these slates in acidic media. The minimum commercial plate thickness varies between 3.5 and 5 mm, depending on the microtexture of the rock. The methodology used in this paper is proposed in order to eliminate the subjectivity of input data that are used in current methods of evaluation and modelling of slate deposits, thus producing an improvement in the profitability of mining operations and a reduction in waste materials.Para evaluar la fisibilidad y la durabilidad de pizarras de techar comerciales, muestras representativas de diez yacimientos del NO de España han sido estudiadas mediante microscopía óptica de luz transmitida y reflejada, microscopía electrónica de barrido y ensayos tecnológicos. Los sulfuros dominantes en las diferentes pizarras estudiadas son pirita o pirrotina, por lo que la alterabilidad de estas es muy variable. La especie carbonatada dominante es ankerita, lo que explica la baja reactividad de estas pizarras en medios ácidos. El espesor comercial mínimo varía en función de la microtextura de la roca, oscilando entre 3,5 y 5 mm. Se propone el uso de la metodología desarrollada en este trabajo, con objeto de eliminar la subjetividad de los inputs de entrada utilizados en las metodologías actuales de evaluación y modelización de yacimientos, lo que incidiría en la mejora de los rendimientos de las explotaciones y en la minimización de la producción de estériles.

  16. Structural and Geochemical Characterization of Fault-related Deformation in the Northeastern Block of the Southern San Andreas Fault, Mecca Hills, Southern California

    Science.gov (United States)

    Keighley Bradbury, K.; Evans, J. P.; Moser, A. C.; Schulthies, S. A.

    2015-12-01

    We examine the structure and composition of several subsidiary NE-trending faults of the Southern San Andreas Fault (SSAF) within the Mecca Hills, southern California. The Hidden Springs, Platform, Eagle Canyon and related smaller faults are part of a positive flower structure that forms a broad zone of fault-related damage within the northeastern block of the SSAF. Here active creep is localized along the main trace of SSAF during the interseismic period. Exhumed exposures span a wide-range of rock types and fault-related rocks and juxtapose Tertiary to Quaternary sedimentary rocks against variable aged crystalline and meta-sedimentary rocks. Detailed characterization of the textural, compositional, and geochemical aspects of the fault-related rocks, and analyses of variations across the 2 faults and related damage zones use a combination of field, microstructural, XRD, XRF, SEM, and isotope methods. Evidence for multiple episodes of slip and fluid flow with a wide range of orientations and amounts of slip is recorded by the geometry and distribution of slip surfaces, cataclasite, reworked cataclasite, deformed and reworked veins, multiple generations of breccia, iron oxide stained gouge, and hematite coated fracture and slip surfaces. Alteration phases vary between fault surfaces and may include chlorite-serpentine, clays (±illite, ±palygorskite), quartz, calcite, ankerite, zeolites, iron oxides, and/or sulfides, or some combination thereof, suggestive of complex fluid-rock reactions. Millimeter-thin slip surfaces within the crystalline rocks consist of plastically deformed and highly sheared calcite. Major vein systems include a predominately north-northwest striking quartz set, a north-south striking calcite set, and an east-west striking calcite set, where locally these sets are complexly interwoven, finely interlayered with other minerals, and/or brecciated rocks. Slip lineations on fault surfaces 1-5 m2 with calcite±clay coated surfaces exhibit multiple

  17. In situ Sr isotope analysis of apatite by LA-MC-ICPMS: constraints on the evolution of ore fluids of the Yinachang Fe-Cu-REE deposit, Southwest China

    Science.gov (United States)

    Zhao, Xin-Fu; Zhou, Mei-Fu; Gao, Jian-Feng; Li, Xiao-Chun; Li, Jian-Wei

    2015-10-01

    Apatite is a ubiquitous accessory mineral in a variety of rocks and hydrothermal ores. Strontium isotopes of apatite are well known to retain petrogenetic information and have been widely used to investigate the origin of igneous rocks, but such attempts have rarely been made to constrain ore-forming processes of hydrothermal systems. We here report in situ LA-MC-ICPMS Sr isotope data of apatite from the ~1660-Ma Yinachang Fe-Cu-REE deposit, Southwest China. The formation of this deposit was coeval to the emplacement of regionally distributed doleritic intrusions within a continental-rift setting. The deposit has a paragenetic sequence consisting of sodic alteration (stage I), magnetite mineralization (stage II), Cu sulfide and REE mineralization (stage III), and final barren calcite veining (stage IV). The stage II and III assemblages contain abundant apatite, allowing to investigate the temporal evolution of the Sr isotopic composition of the ore fluids. Apatite of stage II (Apt II) is associated with fluorite, magnetite, and siderite, whereas apatite from stage III (Apt III) occurs intimately intergrown with ankerite and Cu sulfides. Apt II has 87Sr/86Sr ratios varying from 0.70377 to 0.71074, broadly compatible with the coeval doleritic intrusions (0.70592 to 0.70692), indicating that ore-forming fluids responsible for stage II magnetite mineralization were largely equilibrated with mantle-derived mafic rocks. In contrast, Apt III has distinctly higher 87Sr/86Sr ratios from 0.71021 to 0.72114, which are interpreted to reflect external radiogenic Sr, likely derived from the Paleoproterozoic strata. Some Apt III crystals have undergone extensive metasomatism indicated by abundant monazite inclusions. The metasomatized apatite has much higher 87Sr/86Sr ratios up to 0.73721, which is consistent with bulk-rock Rb-Sr isotope analyses of Cu ores with 87Sr/86Sri from 0.71906 to 0.74632. The elevated 87Sr/86Sr values of metasomatized apatite and bulk Cu ores indicate

  18. Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings.

    Science.gov (United States)

    Huang, Longbin; Li, Xiaofang; Nguyen, Tuan A H

    2015-01-01

    Elevated inorganic phosphate (Pi) concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu)-lead (Pb)-zinc (Zn) mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7), the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5), EHM-TD (fresh Cu-stream, high magnetite content) and local soil (weathered shale and schist), respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed), oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2), ankerite (Ca(Fe Mg)(CO3)2 and siderite (FeCO3), as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,Fe)S, ZnS, (Zn,Cd)S)) may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal. PMID

  19. Geology and geochemistry of the shear-hosted Julie gold deposit, NW Ghana

    Science.gov (United States)

    Amponsah, Prince Ofori; Salvi, Stefano; Béziat, Didier; Siebenaller, Luc; Baratoux, Lenka; Jessell, Mark W.

    2015-12-01

    The Leo Man Craton in West Africa is host to numerous economic gold deposits. If some regions, such as the SW of Ghana, are well known for world-class mineralizations and have been extensively studied, gold occurrences elsewhere in the craton have been discovered only in the last half a century or so, and very little is known about them. The Julie gold deposit, located in the Paleoproterozoic Birimian terrane of NW Ghana, is one such case. This deposit is hosted in a series of granitoid intrusives of TTG composition, and consists of a network of deformed, boudinaged quartz lodes (A-type veins) contained within an early DJ1 E-W trending shear zone with dextral characteristics. A conjugate set of veins (C-type) perpendicular to the A-type veins contains low grade mineralization. The main ore zone defines a lenticular corridor about 20-50 m in width and about 3.5 km along strike, trending E-W and dipping between 30 and 60°N. The corridor is strongly altered, by an assemblage of sericite + quartz + ankerite + calcite + tourmaline + pyrite. This is surrounded by a second alteration assemblage, consisting of albite + sericite + calcite + chlorite + pyrite + rutile, which marks a lateral alteration that fades into the unaltered rock. Mass balance calculations show that during alteration overall mass was conserved and elemental transfer is generally consistent with sulfidation, sericitization and carbonatization of the host TTG. Gold is closely associated with pyrite, which occurs as disseminated grains in the veins and in the host rock, within the mineralized corridor. SEM imagery and LA-ICP-MS analyses of pyrites indicate that in A-type veins gold is associated with bismuth, tellurium, lead and silver, while in C-type veins it is mostly associated with silver. Pyrites in A-type veins contain gold as inclusions and as free gold on its edges and fractures, while pyrites from C-type veins contains mostly free gold. Primary and pseudosecondary fluid inclusions from both

  20. Hydrothermal alteration styles in ancient and modern orogenic gold deposits, New Zealand

    International Nuclear Information System (INIS)

    Orogenic hydrothermal systems in the South Island of New Zealand were active during Mesozoic and late Cenozoic collisional deformation and metamorphism of greywacke/schist terranes. Observations on the currently active mountain-building environment yield insights on processes occurring in the upper 5-15 km of the crust, and observations on an adjacent lithologically identical exhumed ancient mountain belt provide information on processes at 10-20 km in the crust. Hydrothermal fluids were mainly derived from metamorphic dehydration reactions and/or circulating topographically driven meteoric water in these mountain belts. Three geochemically and mineralogically different types of hydrothermal alteration and vein mineralisation occurred in these orogenic belts, and gold enrichment (locally economic) occurred in some examples of each of these three types. The first type of alteration involved fluids that were in or near chemical equilibrium with their greenschist facies host rocks. Fluid flow was controlled by discontinuous fractures, and by microshears and grain boundaries in host rocks, in zones from metres to hundreds of metres thick. Vein and alteration mineralogy was similar to that of the host rocks, and included calcite and chlorite. The second type of alteration occurred where the fluids were in distinct disequilibrium with the host rocks. Fracture permeability was important for fluid flow, but abundant host rock alteration occurred as well. The alteration zones were characterised by decomposition of chlorite and replacement by ankeritic carbonate in zones up to tens of metres thick. The mineralising fluid was deep-sourced and initially rock-equilibrated, with some meteoric input. The third type of mineralisation was controlled almost exclusively by fracture permeability, and host rock alteration was minor (centimetre scale). This mineralisation type commonly involved calcite and chlorite as vein and alteration minerals, and mineralisation fluids had a major

  1. Injection of CO2 with H2S and SO2 and Subsequent Mineral Trapping in Sandstone-Shale Formation

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Apps, John A.; Pruess, Karsten; Yamamoto, Hajime

    2004-09-07

    Carbon dioxide (CO{sub 2}) injection into deep geologic formations can potentially reduce atmospheric emissions of greenhouse gases. Sequestering less-pure CO{sub 2} waste streams (containing H{sub 2}S and/or SO{sub 2}) would be less expensive or would require less energy than separating CO{sub 2} from flue gas or a coal gasification process. The long-term interaction of these injected acid gases with shale-confining layers of a sandstone injection zone has not been well investigated. We therefore have developed a conceptual model of injection of CO{sub 2} with H{sub 2}S and/or SO{sub 2} into a sandstone-shale sequence, using hydrogeologic properties and mineral compositions commonly encountered in Gulf Coast sediments of the United States. We have performed numerical simulations of a 1-D radial well region considering sandstone alone and a 2-D model using a sandstone-shale sequence under acid-gas injection conditions. Results indicate that shale plays a limited role in mineral alteration and sequestration of gases within a sandstone horizon for short time periods (10,000 years in present simulations). The co-injection of SO{sub 2} results in different pH distribution, mineral alteration patterns, and CO{sub 2} mineral sequestration than the co-injection of H{sub 2}S or injection of CO{sub 2} alone. Simulations generate a zonal distribution of mineral alteration and formation of carbon and sulfur trapping minerals that depends on the pH distribution. The co-injection of SO{sub 2} results in a larger and stronger acidified zone close to the well. Precipitation of carbon trapping minerals occurs within the higher pH regions beyond the acidified zones. In contrast, sulfur trapping minerals are stable at low pH ranges (below 5) within the front of the acidified zone. Corrosion and well abandonment due to the co-injection of SO{sub 2} could be important issues. Significant CO{sub 2} is sequestered in ankerite and dawsonite, and some in siderite. The CO{sub 2} mineral

  2. History of diagenetic fluids in a distant foreland area, Middle and Upper Pennsylvanian, Cherokee basin, Kansas, USA: Fluid inclusion evidence

    Science.gov (United States)

    Wojcik, Krzysztof M.; Goldstein, Robert H.; Walton, Anthony W.

    1994-02-01

    Analysis of fluid inclusion data in diagenetic cements from Pennsylvanian limestones and sandstones of the Cherokee basin in southeastern Kansas reveals the succession of diagenetic fluids in a distant foreland of the Arkoma-Ouachita system. This succession includes early low-salinity (0.0-2.4 wt% NaCl eq.) fluids of meteoric affinity (Fluid I) followed by low-temperature Na-Ca-Cl brines (Fluid II with salinities between 8.4 and 24.1 wt% NaCl eq.). Fluids I and II were present in the system during precipitation of early-stage calcite cements at temperatures less than about 50°C. Another Na-Ca-Cl brine (Fluid III with salinity up to 25 wt% NaCl eq.) was present in the system later, at temperatures of maximum burial (at least 80-85°C) and higher. Fluid III is followed by a Na-Cl brine (Fluid IV, with salinities about 19-21 wt% NaCl eq.) characterized by temperatures distinctly higher than maximum burial, up to 150°C. Fluid III and Fluid IV were entrapped during precipitation of late-stage baroque dolomite and Fe-dolomite in Pennsylvanian limestones, and late-stage Fe-dolomite and ankerite in Pennsylvanian sandstones. The record of progression from Fluid III to Fluid IV may have been partially obscured by thermal re-equilibriation of some inclusions during migration of Fluid IV. Fluids with Na-Ca-Cl chemistry (Fluid II and III) were either indigenous subsurface fluids of the Cherokee and Arkoma basins, or might have originated as reflux fluids in a Permian evaporitic basin of Central Kansas. Later Na-Cl brine (Fluid IV) originated in deeper parts of the Arkoma-Ouachita system and might have acquired their salinity by dissolution of hypothetical salts buried beneath the Ouachitas. Temperatures recorded by fluid inclusions in late-diagenetic carbonates are 20-60°C higher than those calculated for the maximum burial of the studied section. This thermal anomaly suggests an advective heat transfer from the Arkoma-Ouachita system onto the shelf of the Cherokee basin

  3. Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings.

    Directory of Open Access Journals (Sweden)

    Longbin Huang

    Full Text Available Elevated inorganic phosphate (Pi concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu-lead (Pb-zinc (Zn mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7, the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5, EHM-TD (fresh Cu-stream, high magnetite content and local soil (weathered shale and schist, respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed, oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2, ankerite (Ca(Fe Mg(CO32 and siderite (FeCO3, as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,FeS, ZnS, (Zn,CdS may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal.

  4. Reactive Transport Models with Geomechanics to Mitigate Risks of CO2 Utilization and Storage

    Energy Technology Data Exchange (ETDEWEB)

    Deo, Milind [Univ. of Utah, Salt Lake City, UT (United States); Huang, Hai [Univ. of Utah, Salt Lake City, UT (United States); Kweon, Hyukmin [Univ. of Utah, Salt Lake City, UT (United States); Guo, Luanjing [Univ. of Utah, Salt Lake City, UT (United States)

    2016-03-28

    Reactivity of carbon dioxide (CO2), rocks and brine is important in a number of practical situations in carbon dioxide sequestration. Injectivity of CO2 will be affected by near wellbore dissolution or precipitation. Natural fractures or faults containing specific minerals may reactivate leading to induced seismicity. In this project, we first examined if the reactions between CO2, brine and rocks affect the nature of the porous medium and properties including petrophysical properties in the timeframe of the injection operations. This was done by carrying out experiments at sequestration conditions (2000 psi for corefloods and 2400 psi for batch experiments, and 600°C) with three different types of rocks – sandstone, limestone and dolomite. Experiments were performed in batch mode and corefloods were conducted over a two-week period. Batch experiments were performed with samples of differing surface area to understand the impact of surface area on overall reaction rates. Toughreact, a reactive transport model was used to interpret and understand the experimental results. The role of iron in dissolution and precipitation reactions was observed to be significant. Iron containing minerals – siderite and ankerite dissolved resulting in changes in porosity and permeability. Corefloods and batch experiments revealed similar patterns. With the right cationic balance, there is a possibility of precipitation of iron bearing carbonates. The results indicate that during injection operations mineralogical changes may lead to injectivity enhancements near the wellbore and petrophysical changes elsewhere in the system. Limestone and dolomite cores showed consistent dissolution at the entrance of the core. The dissolution led to formation of wormholes and interconnected dissolution zones. Results indicate that near wellbore dissolution in these rock-types may lead to rock failure. Micro-CT images of the cores before and after the experiments

  5. Origin of the diagenetic carbonate crusts and concretions from the mud volcanoes of the Nile deep-sea fan

    Science.gov (United States)

    Gontharet, S.; Pierre, C.; Blanc Valleron, M.; Rouchy, J.; Fouquet, Y.; Bayon, G.

    2004-12-01

    During the NAUTINIL cruise (September -October 2003), 22 submersible dives have been realized in the Nile deep-sea fan area to investigate by a multidisciplinary approach, selected mud volcanoes which are very abundant and of various morphologies in the whole area (Loncke et al., 2004). The deepest site (3019 m) located in the western part of the deep-sea fan, corresponds to a large caldera (about 8 km of diameter) where brines are seeping along the flanks of the structure and are sometimes collected in pools and lakes. The other sites in the central and eastern parts of the Nile deep-sea fan correspond respectively to pock-marks located at 2120 m and to a mud volcano located at 1130 m where active fluid ventings were identified by the presence of living benthic organisms (mainly vestimentiferan worms; rarely bivalves). At these three sites, hard carbonate crusts cover irregularly the sea floor and are sometimes present as dispersed fragments within the topmost sediments. The sediments from the venting areas are organic-rich and have a strong H2S smell which is indicative of active sulfate reduction. Petrographic observations and XRD analyses of the carbonate crusts indicate that aragonite, calcite, Mg-calcite are the dominant authigenic carbonate phases with a minor contribution of dolomite ; small concretions of ankerite occur occasionally in the sediments of the eastern delta. Millimeter sized barite concretions have also been discovered in the pock-marks sediments. The oxygen and carbon isotopic compositions of the bulk carbonate from crusts and concretions exibit large variations : -0.67 oxidized as CO2, either through bacterial sulfate reduction within the sediment, or via bacterial aerobic oxidation at the sea floor. Similar isotopic values were previously measured in the diagenetic carbonate crusts from the mud volcanoes of the Mediterranean Ridge area (Aloisi et al., 2000) as well as in other areas of cold seeps outside the Mediterranean sea (for instance

  6. Micro-Raman and micro-XRF analysis of glass beads from the Chungde site, Taiwan

    Science.gov (United States)

    Liou, Y. S.; Wang, S. C.; Liu, Y. C.

    2014-12-01

    A large number of ancient glass beads dating back from Late Neolithic Age to early Historical Period (ca. 2300-400 BP) of Taiwan have been uncovered from archaeological sites. These glass beads with variant colors, shapes, and stylistics have long been considered to possess socio-cultural significance. Due to the color and chemical composition of glass bead might be determined by raw materials, fluxing agents, colorants, opacifiers and stabilizers. In addition, ancient glass beads are rare and precious, non-destructive analysis has been employed to decipher about the provenances, manufacturing techniques, and exchange/trade routes. In this work, micro-Raman spectroscopy and micro X-ray fluorescent spectrometer (μ-XRF) were used to examine ten ancient glass beads excavated from the Chungde site, Hualien, Taiwan, dating back to 1500-800 BP, to unravel the mineralogical and chemical compositions. Micro Raman experimental results show that glass and anorthite glass are the main constituents accompanying with trace level of quartz, albite, siderite, ankerite, and amazonite. The Raman Index of Polymerization (Ip) indicate that the sintering temperature of the glass beads is in the range of 1000~1400°C. Furthermore, the chemical compositions are corresponding to the maximum stretching vibration peak wave number (νmax Si-O Stretching) and the maximum bending vibration peak wave number (δmax Si-O Bending), which are essentially consistent with that of the India-Pacific beads. The μ-XRF results indicate the presence of oxides including SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, SnO2, TiO2, CuO, etc., and could be classified to high aluminum of soda-lime glass system. According to ternary phase diagram analysis of CaO-K2O-Na2O and K2O-Al2O3-CaO, the ancient glass beads analyzed could be attributed to the India-Pacific beads, and is in accordance with that of Raman spectra. The combination of these facts leads to the conclusion that glass beads obtained from the Chungde

  7. Reactive Transport Models with Geomechanics to Mitigate Risks of CO2 Utilization and Storage

    Energy Technology Data Exchange (ETDEWEB)

    Deo, Milind; Huang, Hai; Kweon, Hyukmin; Guo, Luanjing

    2015-12-31

    Reactivity of carbon dioxide (CO2), rocks and brine is important in a number of practical situations in carbon dioxide sequestration. Injectivity of CO2 will be affected by near wellbore dissolution or precipitation. Natural fractures or faults containing specific minerals may reactivate leading to induced seismicity. In this project, we first examined if the reactions between CO2, brine and rocks affect the nature of the porous medium and properties including petrophysical properties in the timeframe of the injection operations. This was done by carrying out experiments at sequestration conditions (2000 psi for corefloods and 2400 psi for batch experiments, and 600C) with three different types of rocks – sandstone, limestone and dolomite. Experiments were performed in batch mode and corefloods were conducted over a two-week period. Batch experiments were performed with samples of differing surface area to understand the impact of surface area on overall reaction rates. Toughreact, a reactive transport model was used to interpret and understand the experimental results. The role of iron in dissolution and precipitation reactions was observed to be significant. Iron containing minerals – siderite and ankerite dissolved resulting in changes in porosity and permeability. Corefloods and batch experiments revealed similar patterns. With the right cationic balance, there is a possibility of precipitation of iron bearing carbonates. The results indicate that during injection operations mineralogical changes may lead to injectivity enhancements near the wellbore and petrophysical changes elsewhere in the system. Limestone and dolomite cores showed consistent dissolution at the entrance of the core. The dissolution led to formation of wormholes and interconnected dissolution zones. Results indicate that near wellbore dissolution in these rock-types may lead to rock failure. Micro-CT images of the cores before and after the experiments revealed that an initial high

  8. Chemical and mineralogical data of the metalliferous mineralization from S. Carlo mine (Peloritani mts, Ne Sicily, Italy

    Directory of Open Access Journals (Sweden)

    Pisacane, G

    2006-05-01

    Full Text Available The mineralization processes in the Peloritani Belt (Southern Sector of the Calabria- Peloritani Arc prevalently developed during the Variscan orogenesis producing Pb, Zn, Fe, As, Sb, Cu, Ag, W, etc. polymetalliferous ore-bearing horizons. This paper focuses on the polymetalliferous mineralization recognised in the ancient S. Carlo Mine, which has already been subject of some studies and is part of an important discordant vein deposits system that are widespread in the Mandanici Unit (MaU. This Unit is characterized by a Variscan low-P, polyphasic and plurifacial metamorphic basement, exhibiting a prograde zoning, from chlorite zone of greenschist facies to oligoclase-almandine zone of amphibolite facies. The Variscan main foliation (Fv2 is irregularly cut by mineralized veins of decimetric to metric width. They are also perpendicular to the Alpine mylonitic shear zones of metric thickness developing along the sub-horizontal tectonic contacts between the tectono-stratigraphic units. These vein deposits formed along late-Alpine systems of fractures and faults, after Peloritani nappe emplacement. Minerographic study reveals a metalliferous mineral association mainly composed of tetrahedrite associated with, in order of decreasing abundance, chalcopyrite, bournonite, pentlandite, stromeyerite, arsenopyrite, scheelite, galena, sphalerite, pyrite, bismuthinite, boulangerite, jamesonite, covellite, bornite and argentite. Quartz, siderite and ankerite among non-metalliferous minerals are predominant. This work has been supported by mineralogical studies and chemical analyses carried out by Atomic Absorption and Inductively Coupled Plasma-Mass Spectrometry on powdered and separated samples of minerals. Geochemical data (major and trace elements have allowed a detailed characterization of the minerals. They have revealed that the most significant minerals with Au contents around 1 ppm are tetrahedrite, sphalerite, chalcopyrite and bournonite. The

  9. Allogenic groundwater recharge to Erenhot Basin%外源地下水补给二连浩特盆地

    Institute of Scientific and Technical Information of China (English)

    陈建生; 王彦超; 谢飞; 徐燚; 陈亚飞; 詹泸成; 江巧宁

    2016-01-01

    In order to identify the source of groundwater recharge in Erenhot, the transforming relationships between atmospheric precipitation, surface water, soil water, and groundwater were studied through isotope geochemical analysis. Due to evaporation, the soil moisture remains lower than the maximum water holding capacity for a long period, and the infiltration of precipitation is not sufficient to change this situation. Compared with precipitation, the soil water is more depleted in deuterium and oxygen isotopes. Through comparison of deuterium and oxygen isotopes in soil water, groundwater, and local precipitation, it was found that the soil water is mainly recharged by groundwater. The isotopic composition of precipitation in the Qiangtang Basin, in Tibet, is similar to that of the groundwater in Erenhot, indicating that the groundwater in the Erenhot Basin is recharged by an allogenic water source. Ankerite, red clay, travertine, siliceous sinter, gypsum, and other minerals are widely distributed in the basalt eruption regions in the Erenhot Basin. Elements such as Fe, Mg, Ca, and Si in these minerals may come from deep-circulating groundwater. The formation of ankerite and red clay indicates that the deep-circulating groundwater goes through a high-temperature process. The allogenic water may come from the seepage of rivers and lakes in the Tibetan Plateau, and the deep-circulating groundwater recharges the groundwater of Erenhot ’ s volcanic basalt areas via volcanic lava pipes. Based on the principle of deep circulation of groundwater, four artesian wells have been drilled near the craters in Erenhot, with the flow capacity of a single well reaching 30 m3/h.%为了查明二连浩特地下水的补给来源,采用同位素地球化学分析方法,研究了二连浩特地区的大气降水、地表水、土壤水与地下水之间的转化关系。结果表明:土壤含水率在蒸发作用下长期处于亏缺状态,入渗降水不足以改变土壤含

  10. Assessing Biogenecity of Stromatolites: Return to the Facies

    Science.gov (United States)

    Shapiro, R. S.; Jameson, S.; Rutter, A.; McCarthy, K.; Planavsky, N. J.; Severson, M.

    2013-12-01

    The discovery of richly microfossiliferous cherty stromatolites near Schreiber and Kakabeka Falls, Ontario, in the 1.9 Ga Gunflint Iron Formation, firmly established the field of pre-Cambrian paleontology. In the half-century since this discovery, paradigm shifts in the ecology of the microfossils as well as the utility of stromatolites as biological markers has caused a re-evaluation of our understanding of the pre-Cambrian fossil record. This research summarizes facies evaluation of the two stromatolite marker beds in the Gunflint-correlative Biwabik Iron Formation of Minnesota. The centimeter-scale microstratigraphy of cores drilled through the central and eastern Mesabi Iron Range was coupled with field descriptions of outcrops and mines in both the Biwabik and Gunflint iron formations. Eight lithologic facies associated with the stromatolites are identified: A) Pebble conglomerate clasts ranging in size of 0.5-3 cm, syneresis cracks, and septarian nodules with medium to coarse grain matrix; B) siltstone with subparallel sub-mm to 5 cm magnetitic and non-magnetic bands; C) stromatolitic boundstone comprising stratiform, pseudocolumnar, domal, undulatory, flat-laminated, dendritic, columnar, and mico-digitate forms and oncoids 0.5 to 2 cm diameter; D) grainstone with medium to coarse siliceous and carbonate ooids and peloids; E) massive green crystalline beds with bands of magnetite, quartz, calcite, disseminated pyrite and localized ankerite; F) autobreccicated fabric of 0.3 to 10 mm clasts; G) medium to coarse sandstone; H) quartzite. Correlation between 11 cores near Hoyt Lakes and 9 cores through the basal stromatolite layer at the MinnTac Mine near Virginia revealed that stromatolites formed both on conglomerate and medium quartz sandstone. Multiple forms of stromatolite may occur in a vertical succession (flat-laminated to undulatory to psuedocolumnar to columnar) or a core may be dominated by one type, typically columnar-stratiform. Where stromatolites do

  11. The mangazeya Ag-Pb-Zn vein deposit hosted in sedimentary rocks, Sakha-Yakutia, Russia: Mineral assemblages, fluid inclusions, stable isotopes (C, O, S), and origin

    Science.gov (United States)

    Anikina, E. Yu.; Bortnikov, N. S.; Klubnikin, G. K.; Gamyanin, G. N.; Prokof'ev, V. Yu.

    2016-05-01

    The succession of mineral assemblages, chemistry of gangue and ore minerals, fluid inclusions, and stable isotopes (C, O, S) in minerals have been studied in the Mangazeya silver-base-metal deposit hosted in terrigenous rocks of the Verkhoyansk Fold-Thrust Belt. The deposit is localized in the junction zone of the Kuranakh Anticlinorium and the Sartanga Synclinorium at the steep eastern limb of the Endybal Anticline. The deposit is situated at the intersection of the regional Nyuektame and North Tirekhtyakh faults. Igneous rocks are represented by the Endybal massif of granodiorite porphyry 97.8 ± 0.9 Ma in age and dikes varying in composition. One preore and three types of ore mineralization separated in space are distinguished: quartz-pyrite-arsenopyrite (I), quartz-carbonate-sulfide (II), and silver-base-metal (III). Quartz and carbonate (siderite) are predominant in ore veins. Ore minerals are represented by arsenopyrite, pyrite, sphalerite, galena, fahlore, and less frequent sulfosalts. Three types of fluid inclusions in quartz differ in phase compositions: two- or three-phase aqueous-carbon dioxide (FI I), carbon dioxide gas (FI II), and two-phase (FI III) containing liquid and a gas bubble. The homogenization temperature and salinity fall within the ranges of 367-217°C and 13.8-2.6 wt % NaCl equiv in FI I; 336-126°C and 15.4-0.8 wt % NaCl equiv in FI III. Carbon dioxide in FI II was homogenized in gas at +30.2 to +15.3°C and at +27.2 to 29.0°C in liquid. The δ34S values for minerals of type I range from-1.8 to +4.7‰ (V-CDT); of type II, from-7.4 to +6.6‰; and of type III, from-5.6 to +7.1‰. δ13C and δ18O vary from-7.0 to-6.7‰ (V-PDB) and from +16.6 to +17.1 (V-SMOW) in siderite-I; from-9.1 to-6.9‰ (V-PDB) and from +14.6 to +18.9 (V-SMOW) in siderite-II; from-5.4 to-3.1‰ (V-PDB) and from +14.6 to +19.5 (V-SMOW) in ankerite; and from-4.2 to-2.9‰ (V-PDB) and from +13.5 to +16.8 (V-SMOW) in calcite. The data on mineral assemblages, fluid

  12. Numerical modeling of injection and mineral trapping of CO2 withH2S and SO2 in a Sandstone Formation

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Apps, John A.; Pruess, Karsten; Yamamoto, Hajime

    2004-09-07

    Carbon dioxide (CO{sub 2}) injection into deep geologic formations could decrease the atmospheric accumulation of this gas from anthropogenic sources. Furthermore, by co-injecting H{sub 2}S or SO{sub 2}, the products respectively of coal gasification or combustion, with captured CO{sub 2}, problems associated with surface disposal would be mitigated. We developed models that simulate the co-injection of H{sub 2}S or SO{sub 2} with CO{sub 2} into an arkose formation at a depth of about 2 km and 75 C. The hydrogeology and mineralogy of the injected formation are typical of those encountered in Gulf Coast aquifers of the United States. Six numerical simulations of a simplified 1-D radial region surrounding the injection well were performed. The injection of CO{sub 2} alone or co-injection with SO{sub 2} or H{sub 2}S results in a concentrically zoned distribution of secondary minerals surrounding a leached and acidified region adjacent to the injection well. Co-injection of SO{sub 2} with CO{sub 2} results in a larger and more strongly acidified zone, and alteration differs substantially from that caused by the co-injection of H{sub 2}S or injection of CO{sub 2} alone. Precipitation of carbonates occurs within a higher pH (pH > 5) peripheral zone. Significant quantities of CO{sub 2} are sequestered by ankerite, dawsonite, and lesser siderite. The CO{sub 2} mineral-trapping capacity of the formation can attain 40-50 kg/m{sup 3} medium for the selected arkose. In contrast, secondary sulfates precipitate at lower pH (pH < 5) within the acidified zone. Most of the injected SO{sub 2} is transformed and immobilized through alunite precipitation with lesser amounts of anhydrite and minor quantities of pyrite. The dissolved CO{sub 2} increases with time (enhanced solubility trapping). The mineral alteration induced by injection of CO{sub 2} with either SO{sub 2} or H{sub 2}S leads to corresponding changes in porosity. Significant increases in porosity occur in the acidified

  13. Solid-Fluid Interaction in Glutenite Reservoirs of the Upper Submember, Fourth Member,Shahejie Formation in Northern Slope of Dongying Sag%东营凹陷北部陡坡带沙四上亚段砂砾岩储层固体-流体相互作用研究

    Institute of Scientific and Technical Information of China (English)

    董果果; 黄文辉; 万欢; 王华军

    2013-01-01

    fluid and solid is characterized by quartz dissolution, feldspar overgrowth and the precipitation of ferrocalcite,ankerite and anhydrite,which largely infill pores and destroy the reservoirs.There are two hydrocarbon expulsion episodes,namely,the deposition period from the second member of Shahejie Formation to Dongying Formation,and the latest one of Guantao Formation.These two events are in correspondence with the development of two secondary pore zones.

  14. Mass transfer and fluid evolution in late-metamorphic veins, Rhenish Massif (Germany): insight from alteration geochemistry and fluid-mineral equilibria modeling

    Science.gov (United States)

    Marsala, Achille; Wagner, Thomas

    2016-08-01

    Element mobility and fluid-rock interaction related to the formation of late-metamorphic quartz veins have been studied by combination of mineral chemistry, whole-rock geochemistry, mass balance analysis and fluid-mineral equilibria modeling. The quartz veins are hosted by very low-grade metasedimentary rocks of the fold-and-thrust belt of the Rhenish Massif (Germany). The veins record two stages of evolution, a massive vein filling assemblage with elongate-blocky quartz, chlorite, apatite and albite, and a later open space filling assemblage with euhedral crystals of quartz, ankerite-dolomite and minor calcite and sulfides. Detailed mass balance analysis of an alteration profile adjacent to a representative quartz vein demonstrates that element mobility is restricted to the proximal zone. The most important element changes are gain of Ca, Fe, Mg, Mn, P and CO2, and loss of Si, K and Na. The data demonstrate that wall-rock carbonation is one of the main alteration features, whereas mobility of Si, K and Na are related to dissolution of quartz and destruction of detrital feldspar and muscovite. The whole-rock geochemical data, in conjunction with fluid composition data and pressure-temperature estimates, were used as input for fluid-mineral equilibria modeling in the system Si-Al-Fe-Mg-Ca-Na-K-C-S-O-H-B-F-Cl. Modeling involved calculation of rock-buffered fluid compositions over the temperature interval 100-500 °C, and reaction-path simulations where a rock-buffered high-temperature fluid reacts with fresh host-rocks at temperatures of 400, 300 and 200 °C. Calculated rock-buffered fluid compositions demonstrate that retrograde silica solubility is a strong driving force for quartz leaching in the temperature-pressure window of 380-450 °C and 0.5 kbar. These conditions overlap with the estimated temperatures for the initial stage of vein formation. Reaction-path models show that high-temperature alteration can produce the observed silica leaching, suggesting that

  15. Analysis of a intra-Carixian clay horizon into carbonate platform of the Ouarsenis (Algeria): composition, dynamic and paleo-climatic implication

    Energy Technology Data Exchange (ETDEWEB)

    Benhamou, M.; Salhi, A. [Oran Univ., Faculte des Sciences de la Terre et de l' Amenagement du Territoire, Dpt. de Geologie (Algeria)

    2005-07-01

    During the Late Sinemurian a carbonate platform has developed on the Ouarsenis area (external Tell o f the Algerian Alpine belt) with setting deposits of the Kef Sidi Amar Carbonate Formation. A first maximum flooding materialized by a brachiopods (Zeilleriids) layer, is occurring during the Late Carixian. The Late Carixian deepening has been followed by a sea-level fall documented by several meters incisions filled by transgressive breccia and conglomerates. After this episode, this material was sealed by a pedogenic bed (0,05 to 0,20 m) which corresponds to a yellow clay deposit containing well rounded particles interpreted as pedo-genetic globules. These corpuscles are composed of reddish and hardened clay, corroded quartz grains, rhombic and zoned dolomite crystals and ankerite, monocrystalline and xeno-morphous detrital quartz grains (1-2 mm). The observed characteristics allow to recognize a typical calcrete. They are the result of pedo-genetic diagenesis developed inside the phreatic water-table near the surface: this is an alteration profile. The mineralogic fraction has been analyzed by X-Ray which show results of association clay mineral as a predominance of illite (85%) and mixed-layer illite-montmorillonite (I-M, 10%) associated with a low ration of chlorite (5%) and kaolinite trace (1%). This mineralogic clay association indicates a shallow water (hydro-morphic zone). Among these clay minerals, the illite reveals the precious indications in a source area. In this case, it comes from the decomposition of the schist paleo-relief located in the internal domain. This rock was transformed by acid leaching (action of the sour humus) into kaolinite with the presence of the quartzification. The origin of the mixed-layer clay I-M (10%) is the result of the active pedogenesis. The simultaneous presence of the illite, chlorite, kaolinite and the mixed-layer clay I-M seems to be result from the erosion exercised on the alteration product or arenitisation of the

  16. The interplay of evolved seawater and magmatic-hydrothermal fluids in the 3.24 Ga panorama volcanic-hosted massive sulfide hydrothermal system, North Pilbara Craton, Western Australia

    Science.gov (United States)

    Drieberg, Susan L.; Hagemann, Steffen G.; Huston, David L.; Landis, Gary; Ryan, Chris G.; Van Achterbergh, Esmé; Vennemann, Torsten

    2013-01-01

    The ~3240 Ma Panorama volcanic-hosted massive sulfide (VHMS) district is unusual for its high degree of exposure and low degree of postdepositional modification. In addition to typical seafloor VHMS deposits, this district contains greisen- and vein-hosted Mo-Cu-Zn-Sn mineral occurrences that are contemporaneous with VHMS orebodies and are hosted by the Strelley granite complex, which also drove VHMS circulation. Hence the Panorama district is a natural laboratory to investigate the role of magmatic-hydrothermal fluids in VHMS hydrothermal systems. Regional and proximal high-temperature alteration zones in volcanic rocks underlying the VHMS deposits are dominated by chlorite-quartz ± albite assemblages, with lesser low-temperature sericite-quartz ± K-feldspar assemblages. These assemblages are typical of VHMS hydrothermal systems. In contrast, the alteration assemblages associated with granite-hosted greisens and veins include quartz-topaz-muscovite-fluorite and quartz-muscovite (sericite)-chlorite-ankerite. These vein systems generally do not extend into the overlying volcanic pile. Fluid inclusion and stable isotope studies suggest that the greisens were produced by high-temperature (~590°C), high-salinity (38–56 wt % NaCl equiv) fluids with high densities (>1.3 g/cm3) and high δ18O (9.3 ± 0.6‰). These fluids are compatible with the measured characteristics of magmatic fluids evolved from the Strelley granite complex. In contrast, fluids in the volcanic pile (including the VHMS ore-forming fluids) were of lower temperature (90°–270°C), lower salinity (5.0–11.2 wt % NaCl equiv), with lower densities (0.88–1.01 g/cm3) and lower δ18O (−0.8 ± 2.6‰). These fluids are compatible with evolved Paleoarchean seawater. Fluids that formed the quartz-chalcopyrite-sphalerite-cassiterite veins, which are present within the granite complex near the contact with the volcanic pile, were intermediate in temperature and isotopic composition between the greisen

  17. Quantitative mineral proxies of fluid chemistry and geothermal gradients in the Kumano Transect, Nankai Trough, Japan

    Science.gov (United States)

    Sample, James; Weeks, Sarah; Fisher, Andrew; Defliese, Will; Tripati, Aradhna; IOPD Expedition 348 Science Party

    2016-04-01

    The Nankai Trough subduction margin is capable of generating tsunamigenic earthquakes with M>8. The physical properties of materials involved in faulting and the magnitude of fluid overpressures exert important controls on the nature of seismicity. We present data from diagenetic carbonates constraining the temperature and chemistry of fluids passing through the accretionary system during deformation. Reference drill sites C0011 and C0012 sampled the sedimentary section and part of basaltic crust. Both sites comprise hemipelagic mud, silty and sandy turbidites with significant ash and volcaniclastic sediment. Carbonates are dominantly calcite or ankerite with varying substitutions of primarily Mn and Fe for Ca. The minimum δ18O values of carbonate samples show a steady trend of decreasing values with depth, and although multiple factors contribute to isotope signatures, at a first order the isotopes are consistent with recent carbonate formation at temperatures following along a geotherm. Temperatures of carbonate formation determined from carbon clumped geothermometry at both sites confirm formation in equilibrium with the modern geothermal gradients, although showing some scatter, consistent with recent and active cementation. Cuttings and cores from Site C0002 in the Kumano Basin, from depths up to ~3 km, suggest increased faulting and carbonate formation with depth. Sample below 2100 mbsf include numerous carbonate slickenfibers. Carbonates are dominantly calcite or low-Mn calcite, with minor Fe substitution. Veined samples show a steady of trend of decreasing δ18O values with depth that could be attributed to vein formation at increasing burial temperatures. No temperature measurements are available from this interval and temperatures have to be estimated by extrapolation of measurements from the shallow Kumano Basin, and using thermal conductivity measurements of well cuttings. The preliminary clumped isotope temperature estimates, mainly from a cored fault

  18. Organic petrology and geochemistry of mudrocks from the lacustrine Lucaogou Formation, Santanghu Basin, northwest China: Application to lake basin evolution

    Science.gov (United States)

    Hackley, Paul C.; Fishman, Neil; Wu, Tao; Baugher, Gregory

    2016-01-01

    inertinite is present in the upper section, indicating greater terrestrial influx and consistent with higher quartz and plagioclase content (dominantly authigenic chalcedony and albite). Laminated mudstones in the upper section indicate anoxia prevented bioturbation from benthic grazing, also indicating stratified water column conditions. A decrease upsection in authigenic dolomite with reciprocal increase of ankerite/siderite is consistent with decreasing salinity, as is an overall decrease in gammacerane index values. These observations suggest evolution from a shallow, stratified evaporative (saline) setting to a deeper, stratified freshwater basin with higher water input during Lucaogou deposition. The evolution from an under-filled to balance-filled lake in Santanghu Basin is similar to Lucaogou deposition in Junggar Basin, suggesting similar tectonic and climatic controls. Paleoclimate interpretations from other researchers in this area suggested an evolution from semi-arid to humid conditions during the Roadian; we interpret that the evolution from an under-filled to balanced-filled lake seen in our data is in response to climate change, and may represent increased groundwater delivery to the Santanghu Basin.

  19. Mass transfer and fluid evolution in late-metamorphic veins, Rhenish Massif (Germany): insight from alteration geochemistry and fluid-mineral equilibria modeling

    Science.gov (United States)

    Marsala, Achille; Wagner, Thomas

    2016-01-01

    Element mobility and fluid-rock interaction related to the formation of late-metamorphic quartz veins have been studied by combination of mineral chemistry, whole-rock geochemistry, mass balance analysis and fluid-mineral equilibria modeling. The quartz veins are hosted by very low-grade metasedimentary rocks of the fold-and-thrust belt of the Rhenish Massif (Germany). The veins record two stages of evolution, a massive vein filling assemblage with elongate-blocky quartz, chlorite, apatite and albite, and a later open space filling assemblage with euhedral crystals of quartz, ankerite-dolomite and minor calcite and sulfides. Detailed mass balance analysis of an alteration profile adjacent to a representative quartz vein demonstrates that element mobility is restricted to the proximal zone. The most important element changes are gain of Ca, Fe, Mg, Mn, P and CO2, and loss of Si, K and Na. The data demonstrate that wall-rock carbonation is one of the main alteration features, whereas mobility of Si, K and Na are related to dissolution of quartz and destruction of detrital feldspar and muscovite. The whole-rock geochemical data, in conjunction with fluid composition data and pressure-temperature estimates, were used as input for fluid-mineral equilibria modeling in the system Si-Al-Fe-Mg-Ca-Na-K-C-S-O-H-B-F-Cl. Modeling involved calculation of rock-buffered fluid compositions over the temperature interval 100-500 °C, and reaction-path simulations where a rock-buffered high-temperature fluid reacts with fresh host-rocks at temperatures of 400, 300 and 200 °C. Calculated rock-buffered fluid compositions demonstrate that retrograde silica solubility is a strong driving force for quartz leaching in the temperature-pressure window of 380-450 °C and 0.5 kbar. These conditions overlap with the estimated temperatures for the initial stage of vein formation. Reaction-path models show that high-temperature alteration can produce the observed silica leaching, suggesting that

  20. Investigations using Laboratory Testbeds to Interpret Flight Instrument Datasets from Mars Robotic Missions

    Science.gov (United States)

    Ming, D. W.; Morris, R. V.; Sutter, B.; Archer, P. D., Jr.; Achilles, C.

    2012-12-01

    high (725-820 °C) temperature and an endothermic reaction in concert with the high temperature release. The high-temperature thermal decomposition is consistent with calcite, dolomite, or ankerite, (3-6 wt.%) or any combination of these phase based upon laboratory testbed experiments. Recent laboratory experiments suggest that the low temperature CO2 release was caused by a reaction between calcium carbonate and hydrated magnesium perchlorate; although, CO2 release by the oxidation of organic materials and Fe-/Mg-rich carbonates cannot be ruled out. MSL landed in Gale crater on August 5, 2012. Although numerous analog samples have been analyzed on the JSC laboratory testbeds, no SAM, CheMin, or ChemCam analyses have been acquired by MSL to date. The JSC SAM laboratory testbed consists of a thermal analyzer coupled with a MS configured to operate under total pressure (30 mbar), heating rate (35 °C/min), and purge gas composition (He) analogous to the flight SAM. The CheMin and ChemCam laboratory testbeds were developed and built by inXitu, Inc. and Los Alamos National Laboratory, respectively, to acquire datasets relevant to the MSL CheMin and ChemCam flight instruments.

  1. 湖南醴陵肖家山金矿地质特征及成矿条件研究%Geological characteristics and metallogenic conditions of Xiaoj iashan gold deposit in Liling of Hunan

    Institute of Scientific and Technical Information of China (English)

    陶诗龙; 赖健清; 宋维国; 查道函

    2015-01-01

    肖家山金矿属于醴陵金矿田的一个典型金矿床。矿区主要出露的地层为中元古界冷家溪群,系一套巨厚的绿片岩相浅变质碎屑岩,为矿床的矿源层。区域岩浆活动强烈,主要出露中生代的花岗岩,为成矿提供了热源和动力。矿区褶皱、断裂构造发育,其中三斗田脆-韧性剪切带和雁林寺韧性剪切带为矿区主要的控矿容矿构造。矿脉主要产于断裂中,呈似脉状。矿床以热液成矿作用为主,成矿期可分为石英―黄铁矿阶段,含金石英―硫化物阶段,石英―铁白云石阶;矿区流体包裹体均为富液相的气液两相包裹体,流体均一温度介于180℃~360℃之间,盐度为3.12%~9.84%(wt%NaCl equiv),流体的密度介于0.67 g/cm3~0.92g/cm3。综合分析矿床是一中高温热液叠加改造型金矿床。%Xiaojiashan gold deposit was a typical gold deposit in Liling gold ore field.The main outcropped strata in the mining area were Mesoproterozoic Lengjiaxi Group,which was a set of thick green schist facies epimetamorphic clastic rock and was the ore source bed of the deposit.With the intensive magmatic activities in this area,mainly outcropped Mesozoic granite provided heat source and dynamic force for mineralization. Among the developed folds and faulted structures,Sandoutian brittle-ductile shear zone and Yanlinsi ductile shear zone were the primary ore-controlling and host structures in the mining area.Vein ores mainly oc-curred in the fractures in veinlike form.The deposit was mainly formed by hydatogenesis,and the minerali-zation periods included quartz-pyrite phase,gold-bearing quartz-sulfide phase and quartz-ankerite phase.The liquid inclusions in the mining area were rich-liquid phase gas-liquid inclusions,while the homogenization temperature of fluid ranged between 180℃ and 360℃ and the salinity ranged between 3.12% and 9.84%(wt%NaCl equiv)and the density of fluid ranged between 0.67g/cm3 and 0

  2. Importance of micro-scale oxygen isotopic study in Gunflint cherts (1.9 Ga): new constraints on paleo-temperatures reconstructions

    Science.gov (United States)

    Marin, J.; Chaussidon, M.; Robert, F.; Marty, B.

    2008-12-01

    Isotopic composition of sedimentary Precambrian cherts contains a record of the Precambrian environment through their oxygen isotopes (δ18O). Indeed, their δ18O values may reflect their temperature of formation, hence the temperature of the ocean provided the seawater δ18O remained constant around 0 ± 3 permil (Holmden and Muehlenbachs, 1993) during these last 3.5 Ga (Knauth and Lowe, 1978; Robert and Chaussidon , 2006). However, this temperature record can be modified by isotopic exchange with hydrothermal or metamorphic fluids. For a given age, the δ18O values of cherts show large variations (Knauth and Lowe, 2003; Perry and Lefticariu, 2003; Robert and Chaussidon, 2006) which complicates the paleo-temperatures reconstructions. To better understand the origin of these local variations, we have analyzed with SIMS, µm-scale δ18O variations in five cherts from the 1.9 Ga old Gunflint iron-formation (Canada) that stands among the least metamorphosed Precambrian cherts. Five chert samples, containing different types of silica (microcrystalline quartz, drusy quartz, megaquartz, and quartz veins), minor carbonates (siderite and ankerite), hematite and pyrite, were analysed (> 100 spots per sample) by multicollector CAMECA ims 1270 ion microprobe (CRPG-CNRS in Nancy). The external reproducibility on quartz standards was of ± 0.17 permil (1 σ, n=65). The Gunflint cherts show (i) detrital quartz with δ18O 10-12 permil lower than microcrystalline quartz, (ii) a typical 3-6 permil, δ18O range for microcrystalline quartz and (iii) quartz veins with δ18O 5-7 permil, lower than microcrystalline quartz. Variations in the proportion of the different types of silica appear to explain the isotopic heterogeneity observed the whole rock sample scale (i.e. sample 4 of 06/30/84; bulk = 22.75 ± 0.3 permil as compared with a mean δ18O calculated from the measured δ18O values of the different phases of silica = 23.18 ± 0.8 permil). Isotopic mapping of quartz veins shows

  3. Petrophysical, Lithological and Mineralogical Characteristics of the Shale Strata of the Volga- Ural Region

    Science.gov (United States)

    Morozov, Vladimir P.; Plotnikova, Irina N.; Pronin, Nikita V.; Nosova, Fidania F.; Pronina, Nailya R.

    2014-05-01

    The objects of the study are Upper Devonian carbonate rocks in the territory of South-Tatar arch and Melekess basin in the Volga- Urals region. We studied core material of Domanicoid facies from the sediments of Mendymski and Domanik horizons of middle substage of Frasnian stage of the Upper Devonian. Basic analytical research methods included the following: study of the composition, structural and textural features of the rocks, the structure of their voids, filter and reservoir properties and composition of the fluid. The complex research consisted of macroscopic description of the core material, optical microscopy analysis, radiographical analysis, thermal analysis, x-ray tomography, electron microscopy, gas-liquid chromatography, chromate-mass spectrometry, light hydrocarbons analysis using paraphase assay, adsorbed gases analysis, and thermal vacuum degassing method. In addition, we performed isotopic studies of hydrocarbons saturating shale rocks. Shale strata are mainly represented by carbonate-chert rocks. They consist mainly of calcite and quartz. The ratio of these rock-forming minerals varies widely - from 25 to 75 percent. Pyrite, muscovite, albite, and microcline are the most common inclusions. Calcareous and ferruginous dolomite (ankerite), as well as magnesian calcite are tracked down as secondary minerals. While performing the tests we found out that the walls of open fractures filled with oil are stacked by secondary dolomite, which should be considered as an indication moveable oil presence in the open-cut. Electron microscopy data indicate that all the studied samples have porosity - both carbonates and carbonate-siliceous rocks. Idiomorphism of the rock-forming grains and pores that are visible under a microscope bring us to that conclusion. The analysis of the images indicates that the type of reservoir is either porous or granular. The pores are distributed evenly in the volume of rock. Their size is very unstable and varies from 0.5 microns

  4. An experimental study on mineral sequestration of CO{sub 2} in basics and ultra basics rocks; Etude experimentale des reactions de carbonatation minerale du CO{sub 2} dans les roches basiques et ultrabasiques

    Energy Technology Data Exchange (ETDEWEB)

    Dufaud, F

    2006-11-15

    percents per hour in high temperature experiments. In all cases, carbonation is shown to proceed according to dissolution/precipitation mechanisms. A quasi stoichiometric coupling is evidenced between carbonation and (proto) serpentinization in high-temperature experiments. Newly formed carbonates are mostly magnesite MgCO{sub 3} with Fe and Ca in solid solution. In low temperature samples, the silicates are covered with a thin silica layer and with carbonate spherules consisting of ankerite CaFe(CO{sub 3}){sub 2} - dolomite CaMg(CO{sub 3}){sub 2} - siderite cores surrounded by magnesite overgrowth. In CO{sub 2}-saturated water, peridotites are more reactive than serpentinite and basalts, in accordance with thermodynamic modelling whereas serpentinites are the most reactive in the supercritical CO{sub 2} phase, showing stronger reactivities in this latter phase than in CO{sub 2}-saturated water. In high temperature experiments, the rate of mineral storage is larger at 400 C than at 500 C, in agreement with thermodynamic modelling of the system. High water fugacities and high fluid salinities are shown to have a positive effect on mineral storage rates. Isotopic mass balance of carbon have evidenced that about 15% of the mineral storage consist of a reduced carbon phase, also identified by transmission electron microscopy as an ill-organized graphite phase. (author)

  5. Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland

    Directory of Open Access Journals (Sweden)

    Nykänen, J.

    1997-12-01

    Full Text Available This paper provides for the first time extensive petrological, mineralogical and geochemical data on the early Proterozoic Kortejärvi and Laivajoki carbonatites, northern Finland, which form metamorphosed and highly strained bodies 2 and 4 km long within a Svecokarelian shear zone in central Fennoscandian Shield. They are not exposed, but have been penetrated by a couple of deep drill holes. In terms of modal mineralogy, both intrusions contain calcite carbonatite and dolomite-calcite carbonatite as their main rock types, but Kortejärvi also contains dolomite carbonatite and calcite-dolomite carbonatite, some glimmerite and olivine-magnetite rock and Laivajärvi tremolite-calcite carbonatite, tremolite-dolomite carbonatite, serpentine-talc-dolomite rock and glimmerite. The main country rock is an amphibolite which is not fenitized. No alkaline rocks have been detected in these intrusions. Calcite is most common mineral in both occurrences. Other carbonate minerals include dolomite with minor ankerite and occassional siderite. In addition to low-Ti phlogopite, tetraferriphlogopite is also encountered. Fresh olivine is rare, and its alteration products include titaniferous clinohumite. The amphiboles are mainly calcic amphiboles, including actinolite, tremolite and edenite. The only sodic-calcic amphibole is accessory richterite. Other essential minerals are Ti-poor magnetite with ilmenite exsolutions, fluorapatite (3.95-4.89 wt. % F, monazite, and allanite-(Ce. Geochemically, the Kortejärvi rocks are mostly magnesiocarbonatites, whereas those of Laivajärvi, due to their higher magnetite content, are ferrocarbonatites. Of the trace elements, Nb is much lower (8-30 ppm in proper carbonatites than the average for carbonatites and U and Th (<0.9 ppm and<2.4 pm, respectively lower than average. Sr is typical, but not high (1830-3480 ppm, and Ba is rather low (27-348 ppm. The REEs are hosted by allanite and monazite and their concentrations in the

  6. 鄂尔多斯盆地陇东地区延长组砂岩成岩作用及孔隙演化%Diagenesis and porosity evolution of sandstones in Longdong Area, Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    钟大康; 祝海华; 孙海涛; 蔡超; 姚泾利; 刘显阳; 邓秀芹; 罗安湘

    2013-01-01

    Researches based on the pore casting thin sections, scanning electron microscopy (SEM) and X-ray diffraction, combined with the analysis of physical properties, have shown that the types of the sandstone reservoirs of Triassic Yanchang Formation in Longdong Area, Ordos Basin, are lithic arkose sandstone, feldspathic lithic sandstone and arkose with low compositional and low structural maturities. The high quality reservoirs were mainly developed in some coarse grained sandstones rich in rigid grains. The primitive porosity of this sandstone is approximately 39% from some empirical formula. During burring, its porosity decreased to 18. 5% due to the fast burial and richness in the shale, slate and phyllite debris. Afterwards, the porosity continually decreased in some extent (3. 5%) as a result of the overgrowth of quartz and chlorite cementation. Constantly, the calcite and dolomite cementation contributed a porosity loss of about 5%. Afterwards, the dissolutions of carbonate cement, feldspar and debris made a contribution to the increase of porosity by about 4%-8%. Finally, the dissolution pores and some primary pores were infilled by ferrocalcite and ankerite cement.%大量岩石薄片、孔隙铸体薄片、扫描电镜与X衍 射以及常规物性等分析资料研究表明,鄂尔多斯盆地陇东地区三叠系延长组砂岩主要为成分成熟度及结构成熟度较低的长石质岩屑砂岩、岩屑砂岩和长石砂岩.优质储层主要发育于粗粒富含刚性颗粒的砂岩中,这类砂岩在埋藏过程中由于早期快速埋藏加之泥岩、板岩及千枚岩岩屑含量高,经历了强烈的压实作用,使其由原始孔隙度大约为39%降低至18.5%;此后发生石英颗粒次生加大及绿泥石胶结,使孔隙有一定程度的损失(大约3.5%);紧随其后的是方解石及白云石碳酸盐胶结,损失孔隙度5%;后来出现碳酸盐胶结物与长石及岩屑的溶蚀作用,新增加孔隙度4%~8%,

  7. Reservoir quality and petrophysical properties of Cambrian sandstones and their changes during the experimental modelling of CO2 storage in the Baltic Basin

    Directory of Open Access Journals (Sweden)

    Kazbulat Shogenov

    2015-08-01

    Full Text Available The objectives of this study were (1 to review current recommendations on storage reservoirs and classify their quality using experimental data of sandstones of the Deimena Formation of Cambrian Series 3, (2 to determine how the possible CO2 geological storage (CGS in the Deimena Formation sandstones affects their properties and reservoir quality and (3 to apply the proposed classification to the storage reservoirs and their changes during CGS in the Baltic Basin. The new classification of the reservoir quality of rocks for CGS in terms of gas permeability and porosity was proposed for the sandstones of the Deimena Formation covered by Lower Ordovician clayey and carbonate cap rocks in the Baltic sedimentary basin. Based on permeability the sandstones were divided into four groups showing their practical usability for CGS (‘very appropriate’, ‘appropriate’, ‘cautionary’ and ‘not appropriate’. According to porosity, eight reservoir quality classes were distinguished within these groups. The petrophysical, geochemical and mineralogical parameters of the sandstones from the onshore South Kandava and offshore E6 structures in Latvia and the E7 structure in Lithuania were studied before and after the CO2 injection-like alteration experiment. The greatest changes in the composition and properties were determined in the carbonate-cemented sandstones from the uppermost part of the South Kandava onshore structure. Partial dissolution of pore-filling carbonate cement (ankerite and calcite and displacement of clay cement blocking pores caused significant increase in the effective porosity of the samples, drastic increase in their permeability and decrease in grain and bulk density, P- and S-wave velocity, and weight of the dry samples. As a result of these alterations, carbonate-cemented sandstones of initially ‘very low’ reservoir quality (class VIII, ‘not appropriate’ for CGS, acquired an ‘appropriate’ for CGS

  8. 合川地区须二段砂岩储层成岩作用及其对储层的影响%The diagenesis of the 2nd Member reservoirs of Xujiahe Formation and its influence on reservoirs of Hechuan area

    Institute of Scientific and Technical Information of China (English)

    杜红权; 朱如凯; 何幼斌; 盘昌林; 刘柳红; 白斌

    2012-01-01

    dissolution of feldspars and the cutting of grains rich in feldspar during the middle diagenetic stage A. In addition, the metasomatism-filling of iron-bearing calcite and ankerite caused the tightness of the reservoir during the middle diagenetic stage B. The compaction and cementation seem to be the main diagenetic types which destroyed the primary pores. The dissolu- tion was the main diagenetic action to form the induced pores. Controlled by diagenesis and diagenetic phase, there exist many types of reservoir space in the 2nd Member of Xujiahe Formation in Hechuan area: intragranu-lar dissolving pores, intergranular dissolving pores and remnant intergranular pores are well developed, and the induced pores growing belt abnormally appears in the 2nd Member of Xujiahe Formation in Hechuan area, resulting from the corrosion of feldspars and the cutting of grains rich in feldspar.

  9. The Main Geological Events of the Kangdian Proterozoic Eon and Response from to the La-La IOCG Deposit%康滇地轴元古代重大地质事件与拉拉IOCG矿床成矿响应

    Institute of Scientific and Technical Information of China (English)

    王奖臻; 李泽琴; 黄从俊

    2012-01-01

    Precambrian deposits are the dominant members of the IOCG group in terms of both copper and gold resources.These giant IOCG deposits are located in intracratonic settings within about 100 km of the margins of Archean or Paleoproterozoic cratons or other lithospheric boundaries.Their tectonic setting at formation was most likely anorogenic,with magmatism and associated hydrothermal activity driven by mantle underplating and/or plumes.Based on a review of isotopic dating data from the Kangdian Proterozoic rocks/minerals,three major geological events are suggested: the formation of the Kangdian basement of the Yangtze craton,2486-1884 Ma,which would be as a part of Kenorland supercontinent;the Kangdian Continental Rifting located along the west margin of Yangtz craton,1725-1466 Ma,which happened during the anorogenic period of Columbia supercontinent;metamorphism-magmatism events(1100-721 Ma) were the response to assembling and rifting of Rodinia supercontinent.The La-La IOCG deposit is hosted by the Kangdian basement of the western margin of Yangtze craton.The host rocks of the deposits are Proterozoic metamorphic rocks,Hekou Group,the protolith of which was the products of the Kangdian Rifting during 1712-1680 Ma,which contributed Stage I meneralization of the Lala IOCG deposit: Iron-P-REE.StageII(1000-900 Ma),with chalcopyrite(I) + magnetite(II) + molybdenite+purple fluorite + ankerite ± pyrite ± cobaltite ± quartz ±biotite(II) ± garnet(II) ± sericite,and StageIII(~850 Ma),with dolomite/calcite+chalcopyrite±quartz,followed assembling of Rodinia supercontinent.%有关IOCG最新研究成果建议,将IOCG矿床限定于资源量大于1 Mt的大型/超大型矿床。对世界上已知的大型/超大型IOCG矿床的成矿背景和成矿作用进行分析对比,发现前寒纪大型/超大型IOCG矿床均位于前寒纪超大陆的边缘、形成于非造山期,与壳幔相互作用有关,与板底垫托、地幔柱等相关的重大地质事件关系密切。

  10. Origin of lacustrine dolostones of the Middle Permian Lucaogou Formation in Santanghu Basin of Xinjiang%新疆三塘湖盆地中二叠统芦草沟组湖相白云岩成因

    Institute of Scientific and Technical Information of China (English)

    李红; 柳益群; 梁浩; 周小虎; 焦鑫; 刘洪福; 杨锐; 雷川

    2012-01-01

    .48. Morphologically, the dolomite was divided into micro-rhombohedra, xenomorphic crystal, microsphere, and microtubule types under the SEM. Part of the micro-rhombohedra dolomite was ferric dolomite. The other kind of dolostone was named analcime-sanidine dolostone which was composed of fine grained analcime with the granularity of 0. 08 ~ 0. 35 mm, micrite potash feldspar ( almost sanidine ) , micrite dolomite, ankerite, and few coarse crystalline dolomite. This kind of dolomite also showed weak ordering with degree of 0.58. Compared with the dolomites in silt-micrite dolostone, the dolomites in analcime-sanidine dolostone which were almost subhedral rhombohedras under the SEM were characterized as high iron and manganese. The similarities between these two dolostones were that they were poor ordering dolomites, abundant in strontium, and lacking of the evidence in replacement during the buried period. Although these two dolostones were deposited in the similar shallow and semi-deep lake anoxic reduction environment, their differences in composition, trace elements and stable isotopes indicated that they had great diversity in their genesis. The silt-micrite dolostone revealed the features of primary precipitation. The microbe was likely to play a formative role in the precipitation of the microspheroidal and microtubular dolomites. Moreover, the micro-rhombohedrala and xenomorphic dolomites were directly precipitated from lake water. Contrastly, the dolomites in analcime-sanidine dolostone were precipitated by the hydrothermal exhalative processes of the sublacustrine hotsprings.

  11. Mg replacement at the Gemerská Poloma talc-magnesite deposit,Western Carpathians,Slovakia%斯洛伐克西喀尔巴阡山脉Gemerská Poloma滑石-菱镁矿矿床中镁的交代作用

    Institute of Scientific and Technical Information of China (English)

    Martin RADVANEC; Peter KOD(E)RA; Walter PROCHASKA

    2004-01-01

    Gemerska Poloma deposit is an important talc deposit (20 Mt of talc), located in the Gemeric unit within Western Carpathians. The partly steatizated Mg-carbonatic carbonate body was formed inside Early Paleozoic volcano-sedimentary complexes (black schist, metapelite) , regionally metamorphosed during Variscan metamorphic event (M1) in chlorite-biotite zone. The body,originally limestone, consists of white-grey and/or grey-black coarse-grained magnesite and dolomite 1 that is cut by veins of younger dolomite 2 and talc. Several successive mineral assemblages within two major metamorphic events M1 and M2 have been recognized.Earliest assemblage consists of ankerite, Mg-siderite and siderite (accompanied by schorl, Fe-chlorite, apatite and illite-muscovite) ,occurring as very small relicts in magnesite and dolomite 1 and probably preceding the peak of M1 metamorphism. The peak of the M1 is represented by the assemblage F-rich phlogopite, Mg-chlorite 1, dravite (the rim of schorl) and quartz. During retrograde part of the M1 successive Mg replacement occurred starting with the crystallisation of dolomite 1, followed by magnesite and terminating by formation of Fe-magnesite along cracks. Based on carbonate geothermometry, the peak of M1 occurred at 460 ~490℃, which is supported by metamorphic mineral assemblage. The M2 metamorphism, related to the younger Alpine orogeny, was responsible for the formation of talc, dolomite 2 and Mg-chlorite 2 along the faults in the host Mg carbonate body.Fluid inclusion study in magnesite showed the presence of fluids with very complex composition, probably MgCl2 dominated brines of evolved evaporitic origin. In primary brine inclusions the salinity reached up to ~35 wt% MgCl2 eq. and homogenisation temperature (Th) occurred in the range 216 to 235 ℃. Fluid inclusion in quartz showed also the presence of MgCl2 dominated brines of similar composition, however, with a higher range of Th values (248 to 313℃). If assuming that