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Showing papers on "Ankerite published in 2018"


Journal ArticleDOI
TL;DR: In this paper, the surface interactions and adsorption mechanism of alkyl hydroxamic acid bearing collectors and sodium silicate depressant on common carbonatite gangue minerals, including calcite, dolomite and ankerite in flotation were investigated.

75 citations


Journal ArticleDOI
TL;DR: In this paper, the authors employed petrographic, mineralogical, and stable isotopic analyses on two different onshore core successions to investigate the composition and texture, the diagenetic history, and the impact of lithology and diagenesis on reservoir quality.

55 citations


Journal ArticleDOI
TL;DR: In this paper, the mineralogical, geochemical, and microbial functional composition were examined in seep carbonate deposits collected from the west slope of the northern section of the Okinawa Trough (OT).

45 citations


Journal ArticleDOI
TL;DR: The upper Permian Shiqianfeng sandstones, located in the Dongpu Depression, Bohai Bay Basin, China, are fluvio-lacustrine deposits and have high content of pore-filling volcanic dust.

35 citations


Journal ArticleDOI
TL;DR: In this paper, As−1 substitutes for S−2 as indicated by the correlation of high As with low S concentrations and the newly constrained partition coefficients for As help to explain the large heterogeneity in natural CTGD pyrite compositions which is caused by changes in the fluid composition due to the strong partitioning of As into the forming pyrites.

32 citations


Journal ArticleDOI
TL;DR: The Mesoarchaean Pongola supergroup of stromatolitic carbonate successions as discussed by the authors contains dolomite and ankerite, and the carbonate samples in this group have variable 87Sr/86Sr isotopic ratios from as low as 0.708 to 0.777.

31 citations


Journal ArticleDOI
TL;DR: In this paper, two core samples from the Cooper Basin Roseneath-Epsilon-Murteree (REM) sequence were geochemically characterised in detail, and the results confirmed the dissolution of siderite, pyrite, sphalerite, and also ankerite from Murteree shale.

31 citations


Journal ArticleDOI
TL;DR: In this paper, a variety of methods were applied to the mudstones in the middle of the third member of the Shahejie Formation (Es3z), which were formed in a lacustrine basin during 43.7-38.2 Ma.

29 citations


Journal ArticleDOI
TL;DR: The results related to these, have been linked with geochemical modelling using the PHREEQC code as mentioned in this paper, which lend support to the view that Pentalofos and Tsotyli sandstone formations of the Mesohellenic Trough are suitable for the long-term storage of CO2 produced in the neighbouring lignite-fired power plants, at least in terms of mineralogy and geochemistry.

26 citations


Journal ArticleDOI
TL;DR: Czaja et al. as discussed by the authors presented new Fe concentrations and isotope compositions of carbonate and mudrock samples from the Neoarchean Campbellrand-Malmani carbonate platform (CMCP) in South Africa.
Abstract: The deposition of large amounts of mixed-valence Fe minerals in iron formations during the Archean and Paleoproterozoic indicates that the Fe(II)aq (aqueous) content of coeval anoxic seawater was likely several hundred μM, compared to ca. 1 to 20 nM of the modern oxygenated ocean. It has been suggested that oxygen production along shallow marine continental shelves, which probably started several hundred million years before the rise of atmospheric oxygen, effectively oxidized Fe(II)aq from deeper seawater and removed it as Fe(III)ppt (poorly soluble precipitates). However, the reconstruction of the marine Fe cycle during the Archean is still incomplete, partly because of diagenetic redox processes that challenge the interpretation of Fe concentration and isotope signatures of sedimentary archives. In this study, we present new Fe concentrations and isotope compositions of carbonate and mudrock samples from the Neoarchean Campbellrand-Malmani carbonate platform (CMCP) in South Africa. These samples are from the shelf facies of the CMCP and in combination with previously published data of Czaja and others (2012) from carbonates and mudrocks of the slope facies, we show that different depositional settings and conditions resulted in different data distributions. Coupled δ56Fe values (−3.685 to +0.083 ‰) and iron concentrations (861–27672 μg g−1) of pure carbonates deposited during open marine conditions, can be explained by partial Fe(II) oxidation between ferruginous deeper water and oxygenated shallow water, leaving the residual Fe(II)aq pool isotopically light, although Fe(II) oxidation by anoxygenic phototrophy cannot be ruled out. Pure carbonates deposited in a peritidal setting, with less exposure to open ocean water, show a smaller Fe isotope variability with δ56Fe values of −1.207 to −0.204 permil and Fe concentration range from 388 to 5413 μg g−1, respectively. We propose that the Fe systematics of peritidal carbonates were dominated by early diagenetic Fe cycling between carbonates and adjacent mudrocks. Synchrotron based X-ray adsorption spectroscopy reveals a change in Fe speciation, where Fe(II)-bearing ankerite and Fe-sulfide dominate the carbonates in the lower part of the CMCP, whereas carbonates of the upper part of the CMCP mainly contain Fe(III)-(oxyhydr)oxides. The fact that Fe(III) phases are still preserved argues for a higher oxidation state on the shelf of the upper CMCP. This is likely because of a lower content of reductants in those settings, in particular organic carbon, sulfide species, as well as restricted influx of reducing species from the anoxic open ocean due to the formation of a rimmed margin. Nevertheless, more studies of similar carbonate settings are necessary to verify our model. We propose that unfractionated Fe(II)aq in seawater was about two to three times lower on the shelf (30–310 μM) than along the slope (61–928 μM), which implies that Fe(II)aq was removed from the water column closer to the continent, likely by oxidation and precipitation. Overall, the Fe isotope composition and Fe speciation of CMCP sediments support the presence of molecular oxygen in the shallow-marine system and emphasize the utility of Ca-Mg carbonates as proxies for iron cycling in the aqueous environment.

25 citations


Journal ArticleDOI
TL;DR: Wang et al. as mentioned in this paper used a combination of thin sections, SEM, BSE, EDS, XRD, and fluid inclusion analyses to study the petrology, paragenesis, and diagenetic processes and implications for reservoir quality.
Abstract: Upper Triassic sandstones in the Ordos Basin, northern-central China, comprise tight oil reservoirs. Using a combination of thin sections, SEM, BSE, EDS, XRD, and fluid inclusion analyses, 24 core samples from 13 wells were collected to study the petrology, paragenesis, and diagenetic processes and implications for reservoir quality. Quartz cement usually occurs as overgrowths or euhedral quartz. Extensive dissolution and albitization of K-feldspar can be observed. Five types of carbonate cements, ferrocalcite, ankerite, dolomite, calcite, and siderite, occur during different diagenetic stages. Two main types of illite and 5 main habits of chlorite are observed in this study. Kaolinite mainly occurs as booklets and vermicular aggregates. Diagenetic illite, chlorite, biotite, mixed-layer illite/smectite (I/S), and other minor minerals are also observed. The diagenetic processes include compaction, alteration of volcanic materials and mica, clay mineral transformation, cementation (silica, aluminosilicate, and carbonate), and dissolution of feldspars and rock fragments. Compaction was a significant porosity-reducing agent, and the presence of carbonate cement exerts a dominant impact on the reduction of porosity. Quartz cement and authigenic clays are less important; however, it is worth mentioning that pore-lining clays are conducive to porosity preservation. In this study, most of the porosity variation is caused by a combination of compaction, carbonate cements, quartz cement, and authigenic clays. This study gives insights into diagenetic alterations within tight sandstones and has implications for reservoir quality prediction in similar settings.

Journal ArticleDOI
TL;DR: In this paper, a study of well cores using petrographic microscope and scanning electron microscopy suggests an otherwise complex hydrovolcanic and hydrothermal origin of profundal shales in the Santanghu rift basin.

Journal ArticleDOI
TL;DR: In this paper, the diagenetic evolution of the lower Eocene red-bed high-quality reservoirs in the Dongying Depression was systematically investigated through an integrated petrographic, petrophysical, fluid evolution and thermal history analysis.

Journal ArticleDOI
TL;DR: The No.2-1 coal (Early Permian-Shanxi Formation) in the Lugou Mine, Xinmi coalfield, Northern China, is a characteristic tectonically deformed coal as mentioned in this paper.

Journal ArticleDOI
Ming Chen1, Jinfu Shu, Xiande Xie1, Dayong Tan1, Ho-kwang Mao 
TL;DR: Discovery of the subsolidus carbonate self-reduction mechanism indicates that diamonds could be ubiquitously present as a dominant host for carbon in the Earth’s lower mantle.
Abstract: Formation of natural diamonds requires the reduction of carbon to its bare elemental form, and pressures (P) greater than 5 GPa to cross the graphite–diamond transition boundary. In a study of shocked ferromagnesian carbonate at the Xiuyan impact crater, we found that the impact pressure–temperature (P-T) of 25–45 GPa and 800–900 °C were sufficient to decompose ankerite Ca(Fe2+,Mg)(CO3)2 to form diamond in the absence of another reductant. The carbonate self-reduced to diamond by concurrent oxidation of Fe2+ to Fe3+ to form a high-P polymorph of magnesioferrite, MgFe3+2O4. Discovery of the subsolidus carbonate self-reduction mechanism indicates that diamonds could be ubiquitously present as a dominant host for carbon in the Earth’s lower mantle.

Journal ArticleDOI
TL;DR: In this paper, the authors present a conceptual model for the formation of Pb Zn MVT deposits in the Irankuh-Emarat district, and suggest that the hydrothermal fluid originated from the dehydration of an oceanic subduction slab, which liberated Pb, Zn, and other metals, and may have removed metals from rocks and organic material of the continental crust.

Journal ArticleDOI
08 Feb 2018-Minerals
TL;DR: In this article, a rare earth element (REE) concentrate was produced through a combination of gravity and magnetic separation, which was then submitted for kinetic testing (weathering cell) in order to investigate the REE leaching potential.
Abstract: Geochemical characterization including mineralogical measurements and kinetic testing was completed on samples from the Montviel carbonatite deposit, located in Quebec (Canada). Three main lithological units representing both waste and ore grades were sampled from drill core. A rare earth element (REE) concentrate was produced through a combination of gravity and magnetic separation. All samples were characterized using different mineralogical techniques (i.e., quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), X-ray diffraction (XRD), and scanning electron microscopy with X-ray microanalysis (SEM-EDS)) in order to quantify modal mineralogy, liberation, REE deportment and composition of REE-bearing phases. The REE concentrate was then submitted for kinetic testing (weathering cell) in order to investigate the REE leaching potential. The mineralogical results indicate that: (i) the main REE-bearing minerals in all samples are burbankite, kukharenkoite-Ce, monazite, and apatite; (ii) the samples are dominated by REE-free carbonates (i.e., calcite, ankerite, and siderite); and (iii) LREE is more abundant than HREE. Grades of REE minerals, sulfides and oxides are richer in the concentrate than in the host lithologies. The geochemical test results show that low concentrations of light REE are leached under kinetic testing conditions (8.8–139.6 µg/L total light REE). These results are explained by a low reactivity of the REE-bearing carbonates in the kinetic testing conditions, low amounts of REE in solids, and by precipitation of secondary REE minerals.

Journal ArticleDOI
Shuang Zhao1, Li Liu1, Na Liu1
TL;DR: Dawsonite-bearing sandstones in the Lishui sag, East China Sea Basin, China, have been investigated as a natural occurrence for CO2-induced diagenesis using petrography, X-ray diffraction and stable isotopes as discussed by the authors.

Journal ArticleDOI
01 Mar 2018
TL;DR: Solomatova et al. as mentioned in this paper calculated the relative enthalpies up to 80 GPa for a set of carbonate phases including Fe-bearing solutions and endmembers, using the generalized gradient approximation and a Hubbard U parameter calculated through linear response theory.
Abstract: It has been proposed that iron has a significant effect on the relative stability of carbonate phases at high pressures, possibly even stabilizing double-cation carbonates (e.g., dolomite) with respect to single-cation carbonates (e.g., magnesite, aragonite and siderite). X-ray diffraction experiments have shown that dolomite transforms at ~35 GPa to a high-pressure polymorph that is stable to decomposition; however, there has been disagreement on the structure of the high-pressure phase (Mao et al. in Geophys Res Lett 38, 2011. doi: 10.1029/2011GL049519; Merlini et al. in Proc Natl Acad Sci 109:13509–13514, 2012. doi: 10.1073/pnas.1201336109). Ab initio calculations interfaced with an evolutionary structure prediction algorithm demonstrated that a C2/c polymorph of pure CaMg(CO_3)_2 dolomite is more stable than previously reported structures (Solomatova and Asimow in Am Mineral 102:210–215, 2017, doi: 10.2138/am-2017-5830). In this study, we calculate the relative enthalpies up to 80 GPa for a set of carbonate phases including Fe-bearing solutions and endmembers, using the generalized gradient approximation and a Hubbard U parameter calculated through linear response theory to accurately characterize the electronic structure of Fe. When calculated with a constant U of 4 eV, the spin transition pressure of (Mg,Fe)CO_3 agrees well with experiments, whereas an internally consistent U overestimates the spin transition pressure by ~50 GPa. However, whether we use constant or internally consistent U values, a higher iron concentration increases the stability field of dolomite C2/c with respect to single-cation carbonate assemblages, but iron-free dolomite is not stable with respect to single-cation carbonates at any pressure. Thus, high-pressure polymorphs of Fe-bearing dolomite could in fact represent an important reservoir for carbon storage within oxidized sections of Earth’s mantle.

Journal ArticleDOI
29 Jun 2018
TL;DR: In this paper, a calcite cemented drill core sample (Evergreen Formation, Surat Basin) was experimentally reacted with formation water and CO2 containing SO2 and O2 at 60 °C and 120 bar.
Abstract: Cap-rock integrity is an important consideration for geological storage of CO2. While CO2 bearing fluids are known to have reactivity to certain rock forming minerals, impurities including acid gases such as SOx, NOx, H2S or O2 may be present in injected industrial CO2 streams at varying concentrations, and may induce higher reactivity to cap-rock than pure CO2. Dissolution or precipitation of minerals may modify the porosity or permeability of cap-rocks and compromise or improve the seal. A calcite cemented cap-rock drill core sample (Evergreen Formation, Surat Basin) was experimentally reacted with formation water and CO2 containing SO2 and O2 at 60 °C and 120 bar. Solution pH was quickly buffered by dissolution of calcite cement, with dissolved ions including Ca, Mn, Mg, Sr, Ba, Fe and Si released to solution. Dissolved concentrations of several elements including Ca, Ba, Si and S had a decreasing trend after 200 h. Extensive calcite cement dissolution with growth of gypsum in the formed pore space, and barite precipitation on mineral surfaces were observed after reaction via SEM-EDS. A silica and aluminium rich precipitate was also observed coating grains. Kinetic geochemical modelling of the experimental data predicted mainly calcite and chlorite dissolution, with gypsum, kaolinite, goethite, smectite and barite precipitation and a slight net increase in mineral volume (decrease in porosity). To better approximate the experimental water chemistry it required the reactive surface areas of: (1) calcite cement decreased to 1 cm2/g; and, (2) chlorite increased to 7000 cm2/g. Models were then up-scaled and run for 30 or 100 years to compare the reactivity of calcite cemented, mudstone, siderite cemented or shale cap-rock sections of the Evergreen Formation in the Surat Basin, Queensland, Australia, a proposed target for future large scale CO2 storage. Calcite, siderite, chlorite and plagioclase were the main minerals dissolving. Smectite, siderite, ankerite, hematite and kaolinite were predicted to precipitate, with SO2 sequestered as anhydrite, alunite, and pyrite. Predicted net changes in porosity after reaction with CO2, CO2-SO2 or CO2-SO2-O2 were however minimal, which is favourable for cap-rock integrity. Mineral trapping of CO2 as siderite and ankerite however was only predicted in the CO2 or CO2-SO2 simulations. This indicates a limit on the injected O2 content may be needed to optimise mineral trapping of CO2, the most secure form of CO2 storage. Smectites were predicted to form in all simulations, they have relatively high CO2 sorption capacities and provide additional storage.

Journal ArticleDOI
TL;DR: In this paper, the results of a visible, near-infrared and short wave infrared (V-NIR-SWIR) spectroscopic study of the Nechalacho rare earth element (REE)-Nb-Zr deposit (Canada), associated rare metal pegmatites and select samples from other REE deposits are reported.

Journal ArticleDOI
TL;DR: Thermodynamical equilibrium calculations suggest that the precipitation of secondary REE minerals may control the REE mobility.
Abstract: Several rare earth element (REE) mine projects around the world are currently at the feasibility stage. Unfortunately, few studies have evaluated the contamination potential of REE and their effects on the environment. In this project, the waste rocks from the carbonatites within the Montviel proterozoic alkaline intrusion (near Lebel-sur-Quevillon, Quebec, Canada) are assessed in this research. The mineralization is mainly constituted by light REE (LREE) fluorocarbonates (qaqarssukite-Ce, kukharenkoite-Ce), LREE carbonates (burbankite, Sr-Ba-Ca-REE, barytocalcite, strontianite, Ba-REE-carbonates), and phosphates (apatite, monazite). The gangue minerals are biotites, chlorite, albite, ankerite, siderite, and calcite. The SEM-EDS analyses show that (i) the majority of REE are associated with the fine fraction (< 106 μm), (ii) REE are mainly associated with carbonates, (iii) all analyzed minerals preferably contain LREE (La, Ce, Pr, Nd, Sm, Eu), (iv) the sum of LREE in each analyzed mineral varies between ~ 3 and 10 wt%, (v) the heavy REE (HREE) identified are Gd and Yb at < 0.4 wt%, and (vi) three groups of carbonate minerals were observed containing variable concentrations of Ca, Na, and F. Furthermore, the mineralogical composition of REE-bearing minerals, REE mobility, and REE speciation was investigated. The leachability and geochemical behavior of these REE-bearing mine wastes were tested using normalized kinetic testing (humidity cells). Leachate results displayed higher LREE concentrations, with decreasing shale-normalized patterns. Thermodynamical equilibrium calculations suggest that the precipitation of secondary REE minerals may control the REE mobility.

Journal ArticleDOI
TL;DR: In this article, the authors focused mainly on the post-depositional changes that occurred during shallow to deep burial diagenetic evolution and subaerial weathering of the Geirud Formation in the Alborz Mountain Range, north of Iran.

Journal ArticleDOI
TL;DR: The Oligocene Huagang Formation sandstone reservoir is now in Period B of mesodiagenesis, which has undergone significant diagenetic alterations such as mechanical compaction, Porelining chlorite cement, feldspar dissolution, quartz cementation and dissolution, and carbonate cementation.
Abstract: The Oligocene Huagang Formation is the main sandstone reservoir in the Xihu Sag, situated in the east of the East China Sea Shelf Basin. With an integrated approach of thin-section petrography, ultra-violet fluorescence microscopy, scanning electron microscopy, and isotope geochemistry, the different diagenetic features were identified, the typical diagenetic parasequences were established, and the diagenetic fluids evolution history were reconstructed for the Oligocene Huagang Formation sandstone reservoir in the south of Xihu Sag. The Huagang Formation sandstone reservoir is now in Period B of the mesodiagenesis, which has undergone significant diagenetic alterations such as mechanical compaction, Pore-lining chlorite cement, feldspar dissolution, quartz cementation and dissolution, and carbonate cementation. Three types of carbonate cements (early siderite, medium ferrocalcite and late ankerite) were identified in the Huagang Formation sandstone reservoir. The carbon and oxygen isotopic compositions of carbonate cements show that the early calcite precipitate from alkaline lacustrine environment whereas the late carbonate cements were closely related to the organic acids. To the Huagang Formation sandstone reservoir, it has experienced two main episodes of dissolution during diagenesis. The early dissolution is that unstable components such as feldspar, lithic fragments, and carbonate cement were dissolved by acidic water. The second dissolution is that quartz and other silicate minerals were dissolved under the alkaline condition. Two main phases of hydrocarbon charging occurred in this study area. The first hydrocarbon emplacement was prior to the medium carbonate cementation but posterior to feldspar dissolution and the onset of quartz cementation at the end of the Miocene. The second hydrocarbon charging occurred in the Quaternary period after the late carbonate precipitation.

Journal ArticleDOI
TL;DR: In this paper, a batch chemical model was established using the numerical simulation program ToughREACT V3.0-OMP to evaluate chemical impacts of SO2 impurity on reservoir rock during CO2 capture and storage in deep saline aquifers.

Journal ArticleDOI
TL;DR: In this article, a range of petrological techniques, the petrology, diagenesis, pore characteristics, and controlling factors on the regional variations of reservoir quality of the Chang 7 sandstones were studied.
Abstract: Through a range of petrological techniques, the petrology, diagenesis, pore characteristics, and controlling factors on the regional variations of reservoir quality of the Chang 7 sandstones were studied. These sandstones, mainly arkoses, lithic arkoses, and feldspathic litharenites, were deposited in a delta front and turbidites in semi-deep to deep lacustrine. The detrital constituents were controlled by the provenance and sedimentary condition, which resulted in a spatially variable composition; e.g., high biotite and feldspar contents in the northeast (NE) of the study area, and high contents of rock fragments, especially dolomite, matrix, and quartz in the southwest (SW). Diagenesis includes intense mechanical compaction, cementation, and dissolution of unstable minerals. Diagenetic minerals which were derived internally include quartz, ankerite, ferrous calcite, albite, illite, kaolinite, and chlorite. Thus the original sandstone composition hadfirm control over the development and distribution of cement. Mechanical compaction and late-stage cementations contribute to the porosity loss of sandstones of Chang7 member. The dissolution porosity in major sandstone, slightly higher than primary porosity is principally dependent on the accessibility of acid fluid. The high content of plastic component facilitated the reduction of primary porosity and limited the mineral dissolution. The best reservoir sandstones are found in W, and partly from NE, M districts, with porosity are primary. The relatively high textural maturity of these sandstones reduces the impact of compaction on primary pores, and commonly existed chlorite rims limited the precipitation of pore filling quartz and carbonate cementation in late stage.

Journal ArticleDOI
06 Mar 2018-Minerals
TL;DR: In this article, the mineralogical and geochemical compositions of the Lopingian coals from an exploratory drill core (ZK4-1) in the Zhongliangshan Coalfield, southwestern China are reported.
Abstract: The mineralogical and geochemical compositions of the Lopingian coals from an exploratory drill core (ZK4-1) in the Zhongliangshan Coalfield, southwestern China are reported in this paper. The Zhongliangshan coals are medium volatile bituminous in rank (random vitrinite reflectance, average 1.38%), characterized by a medium-ash yield (26.84%) and high sulfur content (3.38%). Minerals in the Zhongliangshan coals are mainly composed of clay assemblages (kaolinite, the illite/smectite mixed layer (I/S) and chamosite), pyrite, quartz, carbonate minerals (calcite, marcasite, ankerite, and dolomite), and anatase, followed by rutile, jarosite, natrojarosite, bassanite, gypsum and K-feldspar, with traces of apatite, rhabdophane and barite. Compared with the average concentrations of the world hard coals, some trace elements including Li, V, Co, Cu, Se, Y, Zr, Nb, rare earth elements (REE), Cd, Ta, Hf and Hg, are enriched in the Zhongliangshan coals. The modes of occurrence of chamosite, barite, rhabdophane, quartz and calcite in the Zhongliangshan coals indicate that the coals have probably been affected by the injection of low-temperature hydrothermal fluids. Based on the concentrations of Sc, V, Cr, Co, Ni, Cu and Zn, the ratios of Al2O3/TiO2 and the upper continental crust-normalized rare earth element and yttrium (REY) distribution patterns of the Zhongliangshan coals, the dominant sediment source regions are the Leshan–Longnvsi Uplift, Hannan Upland, and Dabashan Uplift, with a small proportion of terrigenous materials from the Kangdian Upland. The K7 and the upper portion of K1 coals have the potential as raw materials for the recovery of REY.

Journal ArticleDOI
TL;DR: In this article, the authors examined discharge from the abandoned Gem Mine in the Coeur d'Alene Mining District of northern Idaho for the presence of metal nanoparticles from weathering of an ore body of galena [PbS] and sphalerite [(Zn,Fe)S] with associated carbonate zones of siderite [FeCO3] and ankerite [Ca(Fe,Mg,Mn)(CO3)2] in intruded quartz veins.

Journal ArticleDOI
TL;DR: In this article, Li et al. showed that the different types of dolomite have characteristics consistent with a penecontemporaneous metasomatic origin before hydrothermal fluid in a medium-low temperature condition reformed them.
Abstract: Comprehensive research into core and micro-structure characteristics, petrology, trace elements, and carbon and oxygen isotope geochemical characteristics led to the initial discovery of a rare dolomite reservoirs reformed by hydrothermal fluid in the Yingxi area of Qaidam Basin; however, the degree of hydrothermal alteration is weak. The evidence mainly includes the following aspects: (1) the main rock reservoirs are dense, mainly developed ankerite and calcite with a micritic structure. Albite, pyrite, barite, celestite, and other hydrothermal minerals are occasionally found in fractures. (2) Trace amounts of FeO and MnO enriched with carbonate minerals with an average amount of 4.112 and 0.186%, respectively, are present. They were significantly higher than penecontemporary metasomatism dolomites. The amount of Ca2+ and Mg2+ also saw increases, indicating the hydrothermal fluid is an alkaline brine rich in Ca2+, Fe2+, Sr2+, Mn2+, and some Mg2+. (3) REE has a large range of changes and some of them have higher ΣREE values, which suffered from hydrothermal alteration. Clear Eu negative anomalies appeared on REE distribution model curves. It reflected the REE composition characteristics of the lake environment’s specific hydrothermal fluid. It formed in a deep lake with an alkaline brine environment. (4)The change to the range of δ 18OPDB values is −6.8 to −3.6‰, with an average of −5.2‰. The values are between hydrothermal dolomite and penecontemporaneous metasomatism dolomite. This shows that the different types of dolomite have characteristics consistent with a penecontemporaneous metasomatic origin before hydrothermal fluid in a medium–low temperature condition reformed them. The degree of hydrothermal alteration is dependent upon the degree fractures developed as well as the distance between the sample and the hydrothermal channel. In short, the initial discovery of dolomite reservoirs reformed by hydrothermal fluid opens up new horizons for deep tight oil and gas exploration in Qaidam Basin’s Yingxi area in China. These results are substantial in the search for quality “desert” reservoirs present in deep stratum in the Yingxi area.

Journal ArticleDOI
TL;DR: The Mukodek gold field is located in the Yana zone of the Baikal-Muya fold belt (northern Transbaikalia) and its orebodies are gold-bearing metasomatites confined to the fault of NE strike as discussed by the authors.