Showing papers on "Ankerite published in 2012"

On the potential for CO 2 mineral storage in continental flood basalts – PHREEQC batch- and 1D diffusion–reaction simulations

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 for hydration of basalt.

Primary dolostone formation related to mantle-originated exhalative hydrothermal activities, Permian Yuejingou section, Santanghu area, Xinjiang, NW China

Abstract: The Permian Lucaogou Formation is an important hydrocarbon source rock in the Junggar, Turpan, and Santanghu basins in Xinjiang, NW China. For the first time, dolostones associated with mantle-originated exhalative hydrothermal fluid flows are discovered in Yuejingou section in the Santanghu Basin area. They include dolomicrite, doloarenite, and a small amount of dolorudite, and are finely (0.05–0.15 cm thick) interlaminated with lime micrite and dolomicritic analcime laminites. Alkali feldspar and analcime grains are common in doloarenite and are interpreted as having been derived from analcime phonolites and peralkaline magmatic rocks. These magmatic fragments were brought up from subsurface by hydrothermal fluid flow and had experienced exhalative brecciation, transport, and deposition on the lake floor. The matrix consists dominantly of dolomite and ankerite smaller than 0.01 mm. The dolostones can be subdivided into four types on the basis of mineral composition and content. The detrital analcime and alkaline feldspar grains and tuff lithics are interpreted as intraclasts, which were deposited in an under-filled starved lake basin. The δ 18 OPDB values of dolostones are −5‰ to −21.1‰, and −11.9‰ on average; the 87Sr/86Sr ratios of dolostones are 0.70457 to 0.706194, and 0.705005 on average. These values, in combination with evidence of multi-episodes of peralkaline extrusion, suggest a mantle origin of the hydrothermal fluids, which may have promoted primary dolomite formation. The fluid from the upper mantle caused serpentinization of ultramafic rocks that intruded into the lower crust to obtain Mg2+ and Fe2+, and injected the ions into the lake water as the Mg and Fe sources for dolomite and ankerite. Hydrothermal fluids associated with peralkaline magmatic rocks also provided Ca2+, Mg2+, Fe2+, and CO3 2−. Explosive breccias formed and dolostones were convoluted near the vent of hydrothermal fluid exhalation, whereas laminated dolostones formed farther away from the vent. The dolostones are primary dolomite deposition in an intracontinental rift basin and associated with mantle-originated hydrothermal fluids. They provide an insight into the origin of dolomite formation in the geologic history and clues to understand the sedimentary environments and tectonic conditions in northern Xinjiang during the late Paleozoic.

Origin of saponite-rich clays in a fossil serpentinite-hosted hydrothermal system in the crustal basement of the hyblean plateau (sicily, italy)

Abstract: A diapiric intrusion of clays in the Carlentini Formation (Tortonian) was discovered in a quarry at S. Demetrio High (Hyblean Plateau, Sicily, Italy). Seven clay samples were analyzed by different analytical methods, including X-ray powder diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, to determine the composition and mechanism of formation (sedimentary vs. hydrothermal) of these clays. Ferric saponite, carbonates (calcite and traces of ankerite), quartz, pyrite, and zeolites (phillipsite and harmotome) were detected using XRD and FTIR. This mineral assemblage, dominated by Fe-rich saponite, and the abundance of light rare-earth elements (LREE), Eu, fluid-mobile elements (FME > 10 × primordial mantle: Li, Be, B, As, Sb, Pb, U, Ba, Sr, Cs), and other incompatible elements (Zr = 169 ppm, Nb = 46 ppm, Th = 11 ppm, on average) imply that S. Demetrio clays precipitated from a mixture of hot Si-rich hydrothermal fluids (350–400°C) and cold seawater. The evidence is in accord with the affinity of clays for hydrothermally modified mafic and ultramafic rocks, forming the Hyblean lower crust, based on multi-element comparisons, and on the occurrence of trace amounts of chrysotile 2Mc1 and sepiolite. The association of long-chain aliphatic-aromatic hydrocarbons (intensity ratios I2927/I2957 > 0.5) with hydrothermal clays, the lack of fossils, and the similarity of the IR absorption bands with those of organic compounds detected previously in some metasomatized Hyblean gabbroic xenoliths suggest a possible abiogenic origin of hydrocarbons via a Fischer-Tropsch-type reaction. The S. Demetrio clay diapir was emplaced at shallow crustal levels in the Late Miocene as a consequence of the interaction, at a greater depth, of an uprising basalt magma and the products of an early, serpentinite-hosted hydrothermal system.

HYDROTHERMAL CARBONATES OF THE SCHWARZWALD ORE DISTRICT, SOUTHWESTERN GERMANY: CARBON SOURCE AND CONDITIONS OF FORMATION USING δ18O, δ13C, 87Sr/86Sr, AND FLUID INCLUSIONS

Abstract: Diagenetic carbonates, metamorphic carbonates, primary hydrothermal carbonates, and secondary remobilized carbonates (including sinters) from the Schwarzwald ore district in SW Germany formed in various tectonic settings and hydrothermal environments over a period of almost 300 Ma. They were investigated in order to define sources of carbon, dispersion of carbon during fluid-rock interaction processes and, where possible, to specify geochemical fingerprints for carbonates formed during different processes and in different geochemical and tectonic environments. For this purpose, 335 samples of calcite, ankerite, dolomite, siderite, and strontianite from 92 localities in 46 mining areas in the Schwarzwald were analyzed for their carbon and oxygen stable isotope, radiogenic strontium isotope, and trace element (including REE) concentrations and compared to analyses from all potential carbon sources available in this region. These include graphite and rare marbles of the crystalline basement, Permian calcrete from redbed sedimentary rocks (Rotliegend) overlying the crystalline basement, and Triassic carbonates from sediments of higher stratigraphic levels (Muschelkalk). Hydrothermal carbonates mostly formed due to fluid-mixing of hot ascending brines with cool sediment-sourced formation water. Fluid inclusions record temperatures of formation between 100 and 150 °C for most primary calcites. The mixed fluid from which they formed was a highly saline brine of around 25 wt.% salinity, containing NaCl and CaCl 2 in similar proportions. Before mixing, the deep brine was in equilibrium with graphite of the basement and contained, as main carbon species, H 2 CO 3 of very low C-isotopic values [around −16‰, Vienna Pee Dee Belemnite (V-PDB)], whereas the sediment-sourced formation water contained HCO 3 − with higher C-isotopic values (around +2‰, V-PDB). We find that graphite and Triassic carbonates in variable proportions (which are mainly related to variations during the fluid mixing process) are the carbon sources for primary calcite, dolomite of the Permian calcrete for primary ankerite, and the Triassic carbonate sediments for the primary ankerite mineralization of the area between Waldkirch and Feldberg. At some localities, remobilization and reprecipitation appears to have taken place without addition of external solutes, as Sr and C show no difference in their isotopic composition between primary and secondary carbonates. The oxygen isotopic composition of secondary carbonates is invariably more positive than that of primary ones, reflecting lower formation temperatures. One very conspicuous type of secondary calcite, which forms olive-green stubby scalenohedra, was dated for the first time using the U-Pb isochron method. Its Neogene age represents uplift and erosional denudation of the Schwarzwald and corresponds well with its remobilized C and O isotope signature. The carbonates in the Schwarzwald hence reflect discontinuous addition of carbon from surface sediments to the crystalline basement through time involving fluid-rock interaction and fluid mixing processes.

Hydrogeochemical numerical simulation of impacts of mineralogical compositions and convective fluid flow on trapping mechanisms and efficiency of carbon dioxide injected into deep saline sandstone aquifers

Abstract: [1] A series of numerical simulations, which consider density-dependent (convective) groundwater and carbon dioxide (CO2) flow, is performed using a multiphase hydrogeochemical reactive transport numerical model to evaluate impacts of mineralogical compositions on the trapping mechanisms and efficiency of CO2 injected into a deep saline sandstone aquifer (reservoir rock). The results of the numerical simulations show that the mineralogical compositions of the sandstone aquifer have significant impacts on hydrogeochemical behavior of injected CO2 and thus its trapping mechanisms and efficiency. Injected CO2 is accumulated as a free fluid phase beneath the caprock (i.e., hydrodynamic trapping), then dissolved as aqueous phases such as bicarbonate and carbonate anions into groundwater (i.e., solubility trapping), and finally precipitated as carbonate minerals (i.e., mineral trapping). Mineral trapping of injected CO2 takes places as precipitation of a primary carbonate mineral such as calcite and secondary carbonate minerals such as dawsonite, siderite, ankerite, and magnesite. The patterns of hydrogeochemical reactions depend significantly on the initial presence and absence of chlorite in the sandstone aquifer. For mineral trapping of injected CO2, ankerite is the most dominant mineral when chlorite is initially present, whereas dawsonite is the most dominant mineral when chlorite is initially absent in the sandstone aquifer. Mg2+ and Fe2+, which are essential chemical components of such secondary carbonate minerals (i.e., siderite, ankerite, and magnesite) for mineral trapping of injected CO2, are mainly supplied by dissolution of chlorite. As a result, the precipitation amounts of the secondary carbonate minerals and thus the efficiency of mineral trapping of injected CO2 increase significantly as the volume fraction of chlorite increases in the sandstone aquifer. A series of additional numerical simulations, which consider density-independent (non-convective) multiphase fluid flow, is also performed using the same numerical model, and then its results are compared with those of the above-mentioned numerical simulations, which consider density-dependent (convective) multiphase fluid flow, to evaluate impacts of convective fluid flow on the trapping mechanisms and efficiency of injected CO2. The comparison of the results of both numerical simulations shows that convective fluid flow also has significant impacts on hydrogeochemical behavior of injected CO2 and thus its trapping mechanisms and efficiency. Convective fluid flow reduces the free fluid phase of CO2 (i.e., hydrodynamic trapping) and thus enhances the aqueous and solid phases of CO2 (i.e., initially solubility trapping and then mineral trapping).

Origin of carbonate cements in the overpressured top seal and adjacent sandstones in Dongying depression

Abstract: The burial depth of the overpressured top boundary ranges from 2 200～2 800 m in the Dongying Depression.Interacted by overpressured fluids that flow beneath,the overpressured top boundary is generally characterized by well-developed carbonate mineralization,commonly with carbonate content between 15%～40%.The statistical analysis on in-situ electron-microprobe compositional data of 101 carbonate cements from 53 sandstone samples indicated that carbonate minerals could be basically subdivided into three groups,i.e.penecontemporaneous dolomite,calcite and ankerite.Integrated with X-ray diffraction and cathodoluminescence data,their diagenetic sequence was determined as penecontemporaneous dolomite→calcite→ankerite.On the basis of observation of primary inclusions in carbonate cements,the precipitation of carbonate minerals in the overpressured top seal and adjacent sandstones was accompanied with overpressured fluids,with a minimum paleopressure coefficient ranging between 1.29～1.62 and a precipitation temperature obviously higher than the background temperature,which suggested a significant influence by overpressured thermal fluid invasion.Thus,based on previous study results,we proposed that the precipitation of calcite and ankerite cements might be related to activities of overpressured fluids since the deposition at the terminal Dongying stage and the Minghuazhen stage,respectively.Furthermore,this hypothesis was tested by measured oxygen isotopic values that fluctuate from-16.86‰ to-12.29‰ PDB for calcite and from-12.20‰ to-10.20‰ PDB for ankerite.Further investigations suggested that the calcite should precipitate at 90～120℃ for the δ18OSMOW of its homochronous overpressured fluid is around 0.00‰ and the ankerite should precipitate at 110～135℃ for the δ18OSMOW of its homochronous overpressures fluid is 0.25‰.δ13C values of carbonate cements formed at the late diagenesis show a positive shift,ranging from-0.9‰ to +3.58‰,which indicates an origin mainly from the dissolution-reprecipitation process of the Es4 lacustrine carbonate,or an influence of intramolecular carbon isotopic fractionation within carboxylic acids,though the latter seems to play a relatively minor role.

The temperature and compositional dependence of disordering in Fe-bearing dolomites

Abstract: Dolomite occurs in a wide range of rock compositions, from peridotites to mafic eclogites and metasediments, up to mantle depths of more than 200 km. At low-temperatures dolomite is ordered ( R 3), but transforms with increasing temperature into a disordered higher symmetry structure ( R 3 c ). To understand the thermodynamics of dolomite, we have investigated temperature, pressure, kinetics, and compositional dependence of the disordering process in Fe-bearing dolomites. To avoid quench effects, in situ X-ray powder diffraction experiments were performed at 300–1350 K and 2.6–4.2 GPa. The long-range order parameter s , quantifying the degree of ordering, has been determined using structural parameters from Rietveld refinement and the normalized peak area variation of superstructure Bragg peaks characterizing structural ordering/disordering. Time-series experiments show that disordering occurs in 20–30 min at 858 K and in a few minutes at temperatures ≥999 K. The order parameter decreases with increasing temperature and X Fe. Complete disorder is attained in dolomite at ~1240 K, 100–220 K lower than previously thought, and in an ankeritic-dolomites.s. with an X Fe of 0.43 at temperatures as low as ~900 K. The temperature-composition dependence of the disorder process was fitted with a phenomenological approach intermediate between the Landau theory and the Bragg-Williams model and predicts complete disorder in pure ankerite to occur already at ~470 K. The relatively low-temperature experiments of this study also constrain the breakdown of dolomite to aragonite+Fe-bearing magnesite at 4.2 GPa to temperature lower than ~800 K favoring an almost straight Clapeyron-slope for this disputed reaction.

Petrology, Geochemistry, and Stable Isotope Studies of the Chehelkureh Cu-Zn-Pb Deposit, Zahedan, Iran

Abstract: The Chehelkureh base metal deposit in southeast Iran is in an abandoned historic copper district that is fault controlled and hosted in a sequence of slightly Eocene interbedded graywackes, siltstones, and shales. Several stocks and dikes of Oligo-Miocene granodiorite to quartz monzodiorite and granite composition, oriented parallel to the dominant northwest-southeast fault system, intruded into the sedimentary sequence. The sedimentary rocks were metamorphosed to the hornfels facies in some outcrops. The intrusions are spatially and temporally related to mineralized faults. The deposit consists of numerous irregular lenses and veins located along faults that cover an area 1,500 m long by 80 to 280 m wide. There are two periods of primary Cu-Zn-Pb mineralization that crosscut each other. The first stage includes quartz, calcite, dolomite, ankerite, siderite, ilmenite, rutile, molybdenite, pyrrhotite, arsenopyrite, pyrite, and chalcopyrite. The second stage consists of quartz, dolomite, ankerite, siderite, chalcopyrite, sphalerite, pyrite, galena, selenian galena, marcasite, nevskite, and paraguanajuatite. The gangue minerals are dominated by quartz and various carbonates, locally associated with chlorite. Hypogene alteration consists of silicification, carbonatization (ankerite, magnesite, siderite, and dolomite), chloritization, kaolinitization, sulfidation, and, less commonly, sericitization. The intrusive rocks at Chehelkureh are calc-alkaline and have chemical features typical of I-type granitoids. Based on Nb-Y and Ta-Yb discrimination diagrams, the geotectonic environment of Chehelkureh granitoids is an intracontinental volcanic arc (Nb/Y ~ 0.4), which is the same setting as that in the multiphase granitoid batholiths of Zahedan, located southeast of Chehelkureh. Granitoids of the Chehelkureh area have moderate REE (rare-earth element) contents (∑REE = 110–174 ppm; average 153 ppm), moderate light REE/heavy REE ((La/Lu)cn = 7–8), and strong negative Eu anomalies (Eu/Eu* ~ 0.2), but no Eu anomaly is evident in monzodiorites. Spider diagram patterns for samples of igneous rocks show Nb and Ta, Sr, and Ti-V negative anomalies, with high amounts of Cu, U, and Th. Fluid inclusion studies of quartz intergrown with sulfides in quartz veins show three main types of fluid inclusions: type 1 inclusions consist of liquid + vapor + daughter crystal (solid); type 2 inclusions are composed of liquid + minor vapor, with vapor/liquid ratios of 0.1 to 0.4; and type 3 inclusions are vapor rich with liquid/vapor ratios up to 0.05 (liquid phase is minor or absent). Homogenization temperatures (Th) for type 2 inclusions vary between 330° and 480°C, whereas their salinities range from 5 to 15 wt % NaCl equiv. The δ 18Owater values of quartz in sulfide-bearing veins are 8.8 to 11‰, with an average of 10‰. Most of the δ 18Owater values of quartz veins are in the range of typical magmatic, metamorphic, and connate waters, so the source of the ore fluids cannot be distinguished based on oxygen isotopes alone. The δ 18Owater and δ Dwater values calculated from chlorite range from 5.6 to 10.6‰ and −31 to −23‰, respectively. These data lie in the metamorphic water box, in the formation water box, or about midway between the magmatic water field and typical seawater. For kaolinite at ~200°C, the calculated δ 18Owater varies from 4.2 to 10.7‰ and the δ Dwater values range from −88 to −49‰. The carbon isotope values (Pee Dee Belemnite) of carbonates vary between −5.7 and −0.9‰, whereas the δ 18O values (Standard Mean Ocean Water) are between 12.4 and 14.9‰. The coupled oxygen and carbon isotope values shift from magmatic values and can be related to metasedimentary decarbonation reactions and metasomatic exchange of oxygen with magmatic fluid. The range of δ 34S values of sulfide minerals is small (2.0–4.2‰, with a mean value of 3‰), consistent with a magmatic origin for sulfur. Isotope thermometry, based on quartz-carbonate pairs, yields an average of 450°C, which is consistent with fluid inclusion temperatures. Isothermal f O2-pH diagrams constructed at 450°C and 1 kbar suggest that the ore formed in the H2S-predominant field with f O2 and pH ranging from 10−29 to 10−24 and 5.0 to 6.2, respectively. The petrogenetic model proposed for the Chehelkureh deposit suggests that during the Oligocene a quartz-monzodiorite stock intruded the Eocene turbidites and provided a magmatic component to the ore-forming system, but also acted as the heat source for hydrothermal convection cells, although metamorphic and connate waters may also have contributed to the ore-forming fluids. In this model, magma is the main source of sulfur, base metals, and carbon, although Eocene turbidites also contributed some metals and carbon.

Mineral compositional trends and their correlations with petrophysical and well-logging parameters revealed by quanta + bestmin analysis: miocene of the carpathian foredeep, poland

Abstract: This study uses the data from Miocene rocks of the Carpathian Foredeep to test the performance of the computer programs QUANTA and BESTMIN in aiding the interpretation of geophysical log data. These programs were designed to help trace trends in the mineral composition of rocks, the chemical composition of minerals, and the effects of these data on petrophysical and geophysical logging parameters. Chemical and X-ray diffraction data for 65 samples of shales, sandstones, and carbonates taken from cored wells in the molasse basin of the Carpathian Foredeep were processed. Compositional differences were detected between rocks sourced from the platform and rocks sourced from the Carpathians. Quartz, K-feldspar, and zircon were more abundant in the coarse-grained rocks (sandstones), while calcite, ankerite, siderite, pyrite, barite, halite, celestite, apatite, anatase, chlorite, 2:1 minerals, and organic matter were more abundant in the fine-grained rocks (shales). Plagioclase reached its maximum in coarse shales. Ankerite, chlorite, and dioctahedral 2:1 minerals had more Fe in the coarse-grained rocks. The dioctahedral 2:1 minerals in fine-grained rocks had a greater concentration of smectitic layers. This information permitted the precise calculation of grain density, porosity, adsorbed water, and some geophysical logging parameters. It also permitted the calibration of well-log response, in particular, the macroscopic neutron absorption cross-section (Σa) combined with the photoelectric absorption factor (P{e}) or with Pe + Ca (calcium content, measurable in wells by spectroscopic techniques) with porosity and cation exchange capacity (CEC). The NaCl concentration in the pore waters was found to range from the values typical for seawater in shales to the freshwater level in clean sandstones.

Abnormal Transformation of the Clay Minerals in Yinggehai Basin and Its Significances

Abstract: Yinggehai Basin is a Cenozoic marine sedimentary basin with total sediment of 17 km,occupying an area of 11 104 km2,located in the continental shelf of South China SeaThe basin is structurally composed of Yingdong Slope,Yingxi Slope and Central DepressionDue to the existence of the overpressures and the movements of geothermal fluids,there are various unusual geological phenomena in Yinggehai BasinThere exist three types of clay mineral transformations in the basin,normal transformation,faster transformation and slower transformationThe Cenozoic group in Yingdong Slope develops hydrostatic pressure,and the clay minerals transform regularilyWith the increase of buried depth and temperature,smectite transforms into illite by illite/smectite mixed layer,and smectite layer content S% in illite/smectite mixed layer decreases graduallyThere exist overpressures in the Cenozoic group of Central DepressionDST measured pressure coefficient even reaches 24 in LD30-1-1A well district located in the southeast of the depressionAs the measured S% in I/S data show that the overpressures retard the transformation of clay minerals,the clay minerals transform more slowly in the overpressure formation,and the S% in I/S mixed layer is 10%~30% higher than that of formations with a hydrostatic pressure at the same depth in Yingdong SlopeOverpressure's retardation also resulted in the put-off of the expulsion of H+,interlayer water and various cations,which lead the dissolution and cementation of the contiguous reservoirs to be weakenedThe cements of Cenozoic group reservoirs in LD30-1-1A well are lower 50% than that of Yingdong Slope at the same depthDuring Neocene,a large scale of diapirism developed,and geothermal fluids richer in CO2 with a temperature of 200℃were active in Central DepressionThe activity of geothermal fluids accelerated the transformation of clay mineralsThe S% in I/S mixed layer jumped to zone R2 or R3 from zone R0 abruptly,without going through zone R1Meanwhile,chlorite turned to kaolinite unusually in the acid environment,which is confirmed by the Gibbs free energy increment computationsThe quick transformation of clay minerals lead to a large amount of such cations as Na+,Ca2+,Mg2+,Fe3+,Si4+ expelled from the mudstonesThese cations entered the adjacent sandstones and precipitated to form siderite,ankerite,dolomite and ferrocalcite,which filled the pores of the reservoirs and reduced the porosity of the reservoirs

Geochemical characteristics of different iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia

Abstract: Pulverized limonite ore from a Pleistocene–Quaternary lake deposit and compact limonite ore from the Olistostrome member of the Javorik flysch formation, in the Southern Tomasica iron ore deposit, were investigated and compared with different types of siderite and ankerite, limestone and carbonate shale from the same location in order to determine their possible protolith. Two limonite types display a notably distinct REE pattern, REE fractionations, Eu anomalies and other trace element and main oxide content. The REE pattern of compact limonite is characterized by relatively low light ((La/Sm) N = 2.87), heavy ((Gd/Yb) N = 0.98) and total ((La/Yb) = 3.19) REE fractionations, a strong positive Eu anomaly (Eu/Eu* = 2.11) and weakly expressed negative Ce anomaly (Ce/Ce* = 0.82). The compact limonite and siderite REE patterns almost overlap suggesting a common REE source. The same is valid for their Zr/TiO2 N ratios (0.040 in the compact limonite, 0.033–0.053 in the siderites). Pulverized limonite shows remarkably different REE patterns and the highest REE concentrations, (up to 6 to 13 times higher relatively to the other samples). Its REE fractionation pattern ((La/Sm) N = 3.68, (Gd/Yb) N = 1.58, (La/Yb) N = 9.41, Eu/Eu* = 1.10 and Ce/Ce*= 0.81) is very similar to those in the carbonate shale, identifying it as the possible protolith of pulverized limonite. The same is valid for the Zr/TiO ratios (0.025 in pulverized limonite and 0.017 in carbonate shale). The REE pattern of fine grained ankerite ((La/Yb) 2 N = 2.15, Eu/Eu* = 1.95, Ce/Ce* = 0.78) and its Zr/TiO ratio (0.030) are similar to those in siderite, and could, assuming extensive contamination of pulverized limonite, also represent its protolith. However, the REE patterns of coarse grained ankerite exhibit remarkable depletion of LREE over HREE and a strong reverse LREE pattern ((La/Yb) N =0.05–0.20, (La/Sm) N = 0.04–0.10, (Gd/Yb) N 2 = 1.77–1.91). They have (similar to the other studied samples), a positive Eu anomaly (Eu/Eu* = 2.16–2.75) and negative Ce anomaly (Ce/Ce* = 0.32–0.83). Their Zr/TiO ratio (0.004–0.010) excludes coarse grained ankerite as the possible protolith of pulverized limonite.

Age and origin of quartz-carbonate veins associated with the coeur d’alene mining district, idaho and western montana: insights from isotopes and rare-earth elements

Abstract: Sm-Nd, Pb, and Sr isotope and rare-earth element (REE) analyses of quartz-carbonate veins associated with the Coeur d’Alene mining district, Idaho and western Montana, constrain the age and origin of Coeur d’Alene veining. An Sm-Nd isochron age of siderites from ore-bearing veins (1511 ± 45 Ma) and a Pb-Pb isochron age of siderites, ankerites, and calcites from ore-barren veins (1523 ± 41 Ma) are similar to the model age of Coeur d’Alene-type Pb (~1450 Ma) and constrain Mesoproterozoic events in the earliest history of the Belt-Purcell Basin. Xenotime, an accessory mineral found in all veins, is zoned with a core laser ablation age of 1420 ± 90 Ma, confirming vein emplacement early in the diagenetic and/or metamorphic history of the Belt-Purcell Basin, and an overgrowth age of 990 ± 130 Ma results from later, Grenville-age metamorphism. Pb isotope ratios of carbonates from both ore-bearing and ore-barren veins define a single linear array resulting from Mesoproterozoic vein emplacement with an initial Pb isotope ratio similar to that of Coeur d’Alene-type Pb observed in galena, while moderately radiogenic Pb isotope ratios originate from variable amounts of accompanying xenotime. This array is similar to the previously determined “more radiogenic” array of Leach et al. (1998a). Ore-barren veins are characterized by initial 143 Nd/ 144 Nd and 87 Sr/ 86 Sr ratios of 0.5108 and 0.769, respectively, which may be partially inherited from Belt-Purcell Supergroup and/or Archean rocks. In contrast, initial 143 Nd/ 144 Nd and 87 Sr/ 86 Sr ratios of 0.5083 and 1.146 of ore-bearing veins require a source with highly unradiogenic Nd and highly radiogenic Sr, most likely Archean crust. Ore minerals may result from interaction of hydrothermal fluids from Archean sources with potential Belt-Purcell Basin sedimentary exhalative (sedex) deposits. REEs are concentrated in carbonate fractions of veins. Siderite and ankerite are light REE depleted and heavy REE enriched, resulting in significant Sm/Nd fractionation from the dual effects of REE complexation in carbonate fluids and mineralogical control, which in the case of siderite and ankerite favors the heavy REEs. Positive Eu anomalies characterize ore-bearing veins, whereas ore-barren veins retain negative Eu anomalies. Normalization of REE patterns of ore-barren veins to those of adjacent Belt-Purcell wall rocks results in a near-zero anomaly, implying that REEs from Belt-Purcell metasediments were locally scavenged by carbonate-rich fluids responsible for ore-barren veins. In contrast, leaching of Archean gneisses followed by probable interaction with sedex deposits produced fluids that formed ore-bearing deposits. Further faulting and deposition from successive fluxes of carbonate-rich solutions derived in part from leaching Belt-Purcell metasediments generated ore-barren siderite-, ankerite-, and, finally, calcite-dominant veins.

Mineralogical characterization of tailing dams: incidence of abandoned mining works on soil pollution (Linares, Jaén)

Abstract: The metallogenic district of Linares-La Carolina (Jaen, Spain) consists of dyke mineralizations mainly of galena, accompanied by blende, chalcopyrite and barite. Associated to these abandoned mines, relatively extensive areas occupied by spoil heaps and tailing impoundments exist and constitute potential sources of soil pollution by metals and semimetals. In order to analyze the pollution potential of these mining wastes, we have carried out a mineralogical and geochemical study of seven tailing dams and surrounding soils in the area. The mineralogy of the samples was studied by x-ray diffraction (XRD) and scanning electron microscope (SEM). In addition, the total metal content of samples was determined by inductively coupled plasma mass spectrometry (ICP-MS) analysis. Samples were taken from the first 30 cm of the waste piles and soil deposits and white efflorescences were also obtained from the surface of the tailings. In all analyzed heaps, high to very high total contents in Pb (1220-22890 mg/kg), Zn (150-51280 mg/kg), Mn (2658-4160 mg/kg), Ba (1026-19610 mg/kg) and Fe (19400-138000 mg/kg) were observed. The concentrations for these same elements in the studied soils range from 527-9900 mg/kg for Pb, 27-1700 mg/kg for Zn, 506-2464 mg/kg for Mn, 2832-4306 for Ba and 8642-29753 mg/kg for Fe, and these figures indicate a contamination of the soils, according to the guidelines established by the Spanish law. The XRD and SEM results indicate that the tailings are primarily constituted by gangue of the exploited mineralization: quartz, calcite, ankerite, feldspars and phyllosilicates. They are inherited, primary mineral phases. Galena, also primary, appears in low proportion, as well as lepidocrocite, melanterite and cerussite, being these three last secondary minerals and indicating a certain remobilization of metal cations, especially lead and iron. On the other hand, quartz and phyllosilicates predominate in the soils, in which, in addition, is identified a little proportion of galena (primary mineral) and ferro-hexahydrite, also indicating mobilization of Fe. As regarding white surface blooms, they are formed mostly of magnesium sulphate with different hydration states. The morphology of these mineral precipitates reveals that they have been subject to cycle of washing and subsequent dehydration, which indicates that these phases present a great mobility in the environment, and they may be contributing to the transport of metals from the tailings into the surroundings soils.

Charakterystyka mineralogiczno-chemiczna i teksturalna odpadów poflotacyjnych z przemysłu Zn-Pb pod kątem dalszych rozważań wykorzystania ich jako sorbentów

Abstract: The aim of this study was a preliminary characterization (mineralogical, chemical, textural) of flotation wastes - which are the by-product of zinc-lead concentrate extraction - from the standpoint of their further prospective (experimental) use as sorbents of acid gases (SO2 and CO2). The landfill sourced for the wastes used in this study was owned by ZGH “Boles³aw” in Bukowno. The research material consisted of a sample of flotation wastes taken from alluvial pond No. 1, lying in the southern part of the Western Pond. Characterization of the material selected for testing included the following: basic mineralogical (XRD, SEM-EDS) and chemical analysis (determination of analytical moisture content, loss on ignition, basic chemical composition, and content of trace elements), as well as the identification of basic textural parameters (BET specific surface area and pore size distribution). Mineralogical studies showed that the waste material consisted mainly of carbonate minerals (primarily calcite, dolomite, ankerite) and minerals present in the residuum after ore flotation (primarily galena and sphalerite). The chemical analysis indicated that in analyzed samples, calcium, magnesium, and iron components are predominant. They are conditioned by carbonate minerals which predominate in the studied waste. The most significant trace elements were arsenic, followed by manganese, and then bar - present only in quantities not exceeding 1%. Textural analysis showed that the test material has a low surface area and large particle size. The research suggests that the analyzed materials have poor adsorption properties, although they could be used in desulfurization as well as the neutralization of carbon dioxide (carbonation). However, it is necessary for this purpose to conduct additional studies of heavy metals’ leaching in an acidic environment, in addition to applying the admixture of other ingredients to the flotation wastes, such as cement or zeolites, to immobilize hazardous waste components.

Diagenesis of Sandstone and Genesis of Compact Reservoirs in the EastII Part of Sulige Gas Field,Ordos Basin

Abstract: Based on the experimental methods of slice identification,casting slice,scan electron microscope and X-ray diffractions,characteristics of petrology and diagenesis on reservoir in Shan1 section of Shanxi Formation and He 8 section of Shihezi Formation of Permian system in the east Ⅱ part of Sulige gas field were studied.The result shows that the main lithology of sandstone in this area is dominated by lithic sandstone and lithic silicarenite with low grade of maturity.Diagenesis of sandstone in this area mainly include compaction,cementation,corrosion and alteration.Diagenetic minerals mainly include siliceous mineral(chalcedony,quartz secondary overgrowth,and authigenic quartz small crystal),clay minerals(chlorite,illitesmectite formation,kaolinite,illite) and carbonate minerals(calcite,ferrocalcite,ankerite) etc.The highest diagenetic stage reach to period B of middle diagenetic stage on the basis of maturity of organic matter,diagentic minerals,homogenisation temperature of fluid inclusion etc.diagenetic symbols.Diagenesis of sandstone in the east Ⅱ part of Sulige gas field underwent syndiagenetic stage,early diagenetic stage and middle diagenetic stage.Diagenetic environment succession went through faintly acidic environment in period A of early diagenetic stage,relative highly acidic environment in period B of early diagenetic stage,highly acidic environment in period A of middle diagenetic stage,and faintly alkaline environment in period B of middle diagenetic stage. Fast decreasing of porosity could be seen in evolution curve of porosity caused by cementation from period B of early diagenetic stage to period A of middle diagenetic stage. The early diagenetic compaction is one of main factors to decreasing porosity of Shan1 section of Shanxi Formation and He 8 section of Shihezi Formation by means of quantitative calculation.Cementation is the most important factor to decreasing porosity in the studied area.Cementation in period B of middle diagenetic stage is the most important factor leading to poor physical property of sandstone reservoirs especially.The secondary pore formed by corrosion in acidity medium condition in period A of middle diagenetic stage can distinctly ameliorate poor reservoir capability of sandstone.Consequently,erosion play a key role in promoting of physical property of sandstone reservoirs in the east Ⅱ part of Sulige gas field.Secondary pore formed by corrosion of calc-alkali volcanics rock,feldspar and calcite cements in acidity medium condition in period A of middle diagenetic stage is main reserving space in the studied area.Corrosion of quartz particle was discovered in this area for the first time,which implies properties of fluid medium transferred gradually from acidity to alkaline since period B of middle diagenetic stage.

New Flotation Technology Research on Carbonate-Containing Hematite

Abstract: A new flotation technology of carbonate-containing hematite was introduced in this paper, The results show that iron minerals are mainly composed of hematite, siderite, magnetite, limonite, ankerite, quartz, hornblende, and a small amount of chlorite, etc. The increase of iron carbonate can deteriorate the normal flotation of hematite, but now a new flotation technology can weaken the negative influence of iron carbonate on flotation, by which we can obtain the iron concentrate with grade of Fe 66.26 %, recovery of Fe 70.23%. It has been comprehensively demonstrated that the dispersant plays an important role in the selective separation of hematite from iron carbonate and iron silicate.

An experimental study on water-rock interaction during water flooding in formations saturated with CO_2

Abstract: In order to explore the short-term changes in reservoir lithology and physical properties,the process of mineral corrosion,dissolution and precipitiation and the permeability variation of reservoir rocks after CO2 injection,the interation process between CO2-saturated rocks and formation water was studied in detail through core flooding laboratory experiment carried out under simulated reservoir conditions(100℃ and 24 MPa).Changes in ion compositions of the reaction solution in pre-and post-CO2-flooding experiments as well as core scanning electron microscopic and whole-rock X-ray diffraction(XRD) analyses showed that dissolution and corrosion phenomena of carbonate minerals can be observed after the experiment,among which calcite dissolution is the strongest,followed by dawsonite,while ankerite the weakest.The concentration of K+ in the reaction solution varies mainly due to the dissolution of detrital K-feldspar grains.A small amount of kaolinite and intermediate products were generated after the experiment.The composition of intermediate products is mainly composed of C,O,Na,Cl,Al and Si,which have a trend to change into carbonate minerals.New minerals(Kaolinite and intermediate products) and the particles released by the dissolution of the carbonate cement were moved to pore throats and blocked the path of pore,which was the main reason that caused the core permeability reduction.The experiment results have reproduced the short-term process of corrosion of feldspar and dissolution of carbonate minerals as well as precipitation of new minerals after CO2 injection,revealed reasons of permeability variation,and provided geochemical evidence for CO2 trapping mechanisms underground.

Discussion on the Genesis of Baixintu Uranium Deposit in Sonliao Basin

Abstract: Baixintu uranium deposit is with the following major features:(1) well developed low temperature hydrothermal alteration of kaolinization,carbonation,pyritization,hydromicazation,sericitization,hematization et al,and uranium mineral coexisted with hydrothermal pyrite and ankerite and hematite in colloid,mass,strawberry;(2) vein orebody with coffinite as main mineral and a little pitchblende and titanium;(3) complicated isotopes feature of Carbon(δ13C is-268‰～-1049‰),oxygen(δ18O is-1074‰～-171‰),sulfur(δ34S is 1224‰～1433‰ and-3306‰) which are related to atmosphere water,magma,biological transformation and the dissolution of carbonate and sulfateThe above feature shew obvious oxidization and hydrothermal action,and the synthesyzed results of shallow-oxidization and deep fluid actionIn other word,the deposit has "double-open metallogenic system" characteristics of infiltration-type and exudation-type

Mineralogy of Iron-Rich Sediments of Benavi Area in Kurdistan Region—Northern Iraq

Abstract: Benavi iron-rich sediments (BIRS) is located about 20 km N–NW of Amadia district in Duhok Governorate – Northern Iraq. It occurs as an elongated E–W body within the Jurassic–Cretaceous sequences and extends about 2 km. The true thickness of BIRS outcrop ranges from 2.5 m to 12.8 m enclosed within highly fractured carbonate beds. Forty-eight samples collected from 10 sections represent the whole BIRS body. The sampling was systematic according to variations in color, hardness, texture, and iron content. Mineralogical study using instrumentations such as XRD, SEM, EDS, and TGA besides petrography showed that BIRS is composed of mineral assemblages: carbonates (calcite, siderite, ankerite), iron oxides/hydroxides (hematite, magnetite, goethite), sulphides (pyrite and arsenopyrite), silicates (kaolinite, chamosite, glauconite, quartz), and phosphates (collophane and apatite). Calcite is the predominant mineral in the whole BIRS, whereas siderite and ankerite are minor, and dolomite is trace. Shifts of the main real peaks values of calcite about the theoretical value in its d-space in all BIRS samples gave the indication that there is no pure calcite in most studied samples, but in a few samples it appears to be pure. Impure calcite presence is most likely due to Mg2+ and Fe2+ substitutions in the space lattice of the calcite crystals; this is supported by the EDS analysis which showed the presence of these elements in the calcite spectra. XRD results also showed that there is a negative relationship between calcite and iron oxides/hydroxides in BIRS. This is attributed to the loss of carbonate that took place during the oxidation of Fe2+ to Fe3+ and release of H1+ where the initial calcite had been dissolved and replacement of iron oxides/hydroxides occurred, frequently, yielding interpretation for partial and complete replacements of calcareous constituents by iron minerals. The main iron minerals are hematite and goethite. The former is higher at the upper part of BIRS; contrarily, the latter is higher at the middle part. This study proved that different goethites coexist. They differ in crystallization and Al3+ content; these are Al-poor and Al-rich goethites, supported via the wide range of decomposition temperature by TGA (263oC–350oC); besides the peaks shifts to higher 2O angles indicating Al3+ substitution for Fe3+. Most of the primary Al-poor goethite altered to Al-poor hematite (by dehydration), hence the prevailing of the latter at the upper part, whereas Al-rich goethite which dominated at the middle of BIRS is a secondary and it is produced by goethitization of pyrite, siderite, and chamosite under surface weathering circumstances. High specific surface area of iron oxides/hydroxides probably acted as important sorbents to dissolve species: particularly heavy metals, phosphates, and arsenate, then under reduction conditions most of the adsorbed species released from iron oxides/hydroxides surfaces. This may give a clue about the presence of phosphate minerals, as well as the presence of arsenopyrite in the lower part of BIRS. Clay minerals of BIRS were represented by kaolinite and chamosite as well as a trace of glauconite noted in some samples. Paragenetically, kaolinite may have recrystallized or transformed to chamosite under reducing conditions in the availability of Mg2+ and iron oxides. Arsenopyrite, which has not been mentioned before, was confirmed by EDS and it is found restricted at the base of BIRS. The presence of arsenopyrite mineral in BIRS may give vital evidence to hydrothermal activations in this area. Frequently, finding other ores in the study area is promising.

Diagenetic carbonates in clay-rich marine formations

Abstract: Diagenetic carbonate minerals reflect the evolution of the Ca/Fe/Mg ratios of porewaters in clay-rich formations over geological time. Existing models consider equilibrium reactions with pure carbonates: calcite (for Ca), dolomite (for Mg) and siderite (for Fe) (Pearson et al., 2003; Gaucher et al., 2009). However, studies provide evidence that the chemical compositions of carbonates is complex. Their understanding remains a challenge but is needed to improve geochemical porewater models over a range of temperatures. Here, we present petrological investigations on four marine, reducing clay formations: Callovian-Oxfordian (COx) Clay at Bure (France), Toarcian Clay at Tournemire (noted Tournemire Clay, France), Opalinus Clay at Mont Terri and Benken (Switzerland) and Rupelian Boom Clay at Mol (Belgium), to characterise the stability and composition of diagenetic carbonates over a range of temperatures. The four clay formations differ from one to another by their age, their maximum burial and their geological history (Table 1). Boom Clay and COx Clay underwent limited burial and diagenetic processes (T 0.5 were identified in rare grains of Opalinus Clay and Tournemire Clay. δ18O of bulk dolomite/ankerite measured in COx Clay (~+27.5 ‰SMOW) and in Tournemire Clay (+21 to 22 ‰SMOW) suggest that they formed from a marine fluid at temperatures corresponding to the maximal burials attained by the units (~45°C for COx Clay and ~80-120°C for Tournemire Clay). Siderite occurs in two textural types: concretions in Opalinus Clay and in Boom Clay, and disseminated grains in the matrix of COx Clay, Opalinus Clay and Tournemire Clay. Textures of concretions strongly suggest that siderite formed early but only once the bacterially mediated sulfate reduction ceased. δ18O values for disseminated siderite in COx Clay (+26 to +29 ‰SMOW) and in Tournemire Clay (+19 to +22 ‰SMOW) indicate that siderite, like dolomite/ankerite, formed at temperatures corresponding to the maximal burial attained by these units. These data indicate that siderite may precipitate at different stages during diagenesis. In summary, it is evident that calcite is the major authigenic carbonate mineral that formed at different stages during burial. Calcite that formed later than the end of bacterial sulfate reduction has a Fe/(Fe+Mg) ratio up to 0.7-0.8, irrespective of the temperature at which it formed. This suggests that its composition remained essentially constant with increasing temperature. Formation processes of dolomite and ankerite are not well understood. According to oxygen isotopes, dolomite/ankerite formed until the time of maximal burial. It appears that ankerite may precipitate over a large range of temperatures (~50-110°C). The essentially homogeneous composition of siderite in the four clay formations, irrespective of formation temperature (~20-110°C), indicates that 1) siderite saturation is attained at different times during the diagenesis of the four studied formations, and 2) its composition is stable over a large range of temperatures.

Geochemistry and Diagenetic Pattern of Ore-Bearing Rocks about Two Types of Gold Deposit in Fengxian-Taibai Basin, South Qinling

Abstract: Baguamiao and Shuangwang gold deposit are two important gold types in Fengxian-Taibai basin. The gold deposits are all located at the bottom of the Upper-Devonian Xing-hongpu Formation. However the ore-bearing rocks are different between them. The ore-bearing rock of Baguamiao gold deposit is ankerite rocks, which is concordant with the strata by bedded or stratoid and assume rhythmic layering form. The ore-bearing rock of Shuangwang gold deposit is albite breccias, which are mostly lens-shaped. The data of petrochemistry show that both of them are poor in Fe2O3 and K2O, which are different from normal sedimentary rocks. The elements contents of Cu, Pb and Zn are close to Clarke value. But the content of dispersed element Ge is rich in rocks, which reflect hydrothermal sedimentary origin. The characteristic of REE are different between them. The REE contents of ankerite rocks are low and elements of Ce and Eu are positive anomaly. The REE contents of albite breccias are close to regional strata and elements of Ce and Eu are middle negative. The chondrite-normalized REE patterns are also alike. It’s shown that the diagenetic fluid are high-density which been mixed by sea water slightly. So the ankerite rocks hold the REE characteristic of thermal fluid. The diagenetic fluid of albite breccias are low-density thermal fluid which been mixed by sea water intensively. It has same REE characteristic to normal sedimentary rocks.

The Importance of Mineral Surface Areas Exposed to Open Pores in Rotliegend Sandstones for Modelling CO2 Water-rock Interactions

Abstract: Rotliegend reservoir rocks from the northern Netherlands were analysed in terms of mineralogical features, diagenetic mineral types and mineral surface areas which are exposed to open pores (effective mineralogy). The consideration of the effective mineralogy in comparison to the volumetric bulk rock composition of sandstones and the integration into CO2-water-rock simulation has shown that the mineral reactions are sensitive according to the initial data set. For the test scenario the results show that during CO2 storage especially long-term carbonate and silica reactions are affected. For the effective mineralogy data Mg-smectite stays in equilibrium with the solution which is caused by a higher initial amount of hematite and the release of iron for siderite precipitation. This reaction lowers the bicarbonate content in the solution and forces dolomite and ankerite to dissolve consequently. On the other hand Mg-smectite is unstable and carbonate minerals stay in equilibrium at the end of the simulation according to the volumetric mineralogy data.

Simulation of long-term geochemical behavior and mineral trapping of CO 2 in saline aquifer

Abstract: Geochemistry plays a significant role in CO 2 storage, especially when considering on long term behavior of injected CO 2 . In this work, reactive transport modeling of supercritical CO 2 in a multilayered saline aquifer was performed. After injection for 30 years, the long-term behavior of the CO 2 by considering its geochemical reaction for 5,000 years was investigated. Result shows that mineral trapping occurs mainly within the shale layers. Mineralization becomes the dominant trapping mechanism after 1,000 years. Significant amounts of ankerite precipitate due to the mineralization of the injected CO 2 . Calcite dissolved rather than precipitated because of the decrease in pH. Because of the compensation effect among mineral species, precipitation/dissolution around the injection region does not play a significant role to change in porosity and permeability under the geologic conditions employed in this work. The results of this study will be applied to the CCS project that is underway in South Korea.

Изотопный состав углерода и кислорода в рудах золотого месторождения Чертово Корыто (Патомское нагорье)

Abstract: Isotopic composition of carbon, oxygenised in carbonates and deoxidated in kerogen, as well as oxygen of the Chertovo Koryto gold deposit has been studied; the deposit was formed in the early-Proterozoic black-shale series. The isotopic composition of carbon in kerogen has meaning 26.2 and 24.6‰. The ankerite from beresite and quartz veins characterised weighted mean 18.5…18.2‰ and 18.4…17.4‰ respectively. The isotope relations of oxygen ankerite keep within a narrow range ƒ18О (14.2…15.1‰). It is supposed that weighting of isotope composition of carbon of carbonates is caused by the mixture of isotopically light carbon kerogen in the course of its oxidation with isotopically heavy carbon, arriving in the system with metal-bearing fluids generated in the mantle reservoirs. A number of facts testify to the possibility of existence of deep fluids: confinedness of ore deposits to the upper wall of a deep fracture, which carries out ore-control and fluid-supplying functions; presence of inter-mineral dolerite dikes; presence of contrasting anomalies of phemophile elements (P, Ti, Mg, Ca, Fe, Mn) in beresite nearly frame ore-control a deep break; affinity of isotope composition of sulphur early metasomatic and late (in quartz veins) sulphides of ores to the meteoric standard (+1,8 …+4,7‰). The similar facts are fixed in the deposits localised in shale (Sukhoy Log, Muruntau, Charmitan, Kedrovsky, Sovetskoe, etc.) and crystal (Irokinda, Berikulsky, etc.) substance. Isotope ratios of carbon of hydrothermal carbonates close to the mantle marks (-4.5 ‰) in many mesothermal gold deposits are consistent with the conclusion of the operation of the underlying metal-bearing solutions in systems of mineralization. In the Chertovo Koryto ankerite deposits carbon isotope ratios correspond to values intermediate between isotopically light carbon of kerogen and relatively heavy mantle carbon. Possibly, addition of carbon to the area of mineralization occurred with solutions as a part of deep carbonic acid. The isotope of carbon increased from early ankerite of beresites to late ankerite of quartz veins and veinlets, which may be due to partial mixture of deep oxidised carbon with deoxidised carbon of kerogen slates in the course of its oxidation accompanied by beresite bleaching. The isotope composition of ankerite oxygen is thus common in magmatic hydrothermal carbonates. In other mesothermal deposits, such as the Sukhoy Log, the effect of mixture is absent. In contrast to the Chertovo Koryto deposit the deficit of bleached (excluding kerogen) beresites here shows the functioning of deoxidised solutions unable to oxidise the carbon of kerogen.

The identification of iron in a Spanish coal using low temperature Mossbauer spectroscopy (4.2°-40K)

Abstract: The method of using low temperature Mossbauer spectroscopy to identify the iron species in coal is illustrated for sub bituminous (AA5) and semi-anthracite (BZ) coals. The 4K spectrum of the AA5 sample exhibits besides pyrite and rozenite a magnetically split ferric component compatible with jarosite (H=485 kOe). Whilst, set of low temperature spectra of the BZ sample, taken respectively at 9K, 20K, 30K and 40K indicate besides pyrite and szomolnokite other two relaxation sextets belong to siderite and ankerite. Furthermore, analysis of iron by the method of atomic absorption spectroscopy and according to ASTM methods for coal showed the presence of organically bound iron (0.133 % Fe.) in the BZ sample. The existent of an organic iron in a coal sample is of a great importance, which will be inevitably discussed in this work.

The predicted fate of CO2 injected into basaltic rock.

Abstract: A number of recent studies have advocated the injection of CO2 into basaltic rocks to promote mineral carbonation due to their abundance in divalent metal cations and their high reactivity. This study assesses this possibility through a set of reactive path modeling calculations. Two gas mixtures were considered 1) pure CO2 and 2) a 75%-24.2%-0.8% mixture of CO2-H2S-H2. It is assumed that these gases are dissolved into a representative basaltic groundwater prior to their injection into the subsurface. The injected water is assumed to have a temperature of ~25 °C and is equilibrated with ~25 bar pressure of the CO2 gas, and ~14 bar pressure of the CO2-H2S-H2 mixture. The injected fluid will have a total CO2 concentration of ~0.8 and a pH of 3.7 for the pure CO2 gas and total CO2 concentration of ~0.42 and a pH of 4.0 for the gas mixture. Model calculations reacted these fluids with basaltic glass, the most abundant constituents of many basalts. Reaction path modelling shows that 1-2 moles of basaltic glass are needed to lower the CO2 concentration of each liter down to natural pre-injection concentrations, but less than 1 mole is needed for the H2S rich fluid. Major carbonates formed were Ca-Mg-Fe-carbonate and dolomite at pH <5, whereas ankerite and calcite formed later at higher pH. Associated minerals at lower pH were chalcedony, kaolinite and iron hydroxide, followed by smectite and zeolites at higher pH. Modelling result suggest that the first sulfur bearing phase to precipitate is elemental sulfur, followed by greigite and mackinowite upon further basaltic glass dissolution.