Ankerite

About: Ankerite is a research topic. Over the lifetime, 859 publications have been published within this topic receiving 23960 citations.

Covariance of C- and O-isotopes with magnetic susceptibility as a result of burial diagenesis of sandstones and carbonates: an example from the Lower Devonian La Vid Group, Cantabrian Zone, NW Spain

Abstract: The burial diagenesis of sandstones, limestones, and dolostones of the Lower Devonian La Vid Group in the Cantabrian Zone (NW Spain) reveal a covariance of carbon and oxygen isotope values with magnetic susceptibility. Also, strontium isotopes, and to a minor degree Fe, follow this trend. The main carriers of the magnetic susceptibility appear to be diagenetic Fe-carbonates, i.e., siderite, ferroan dolomite, and ankerite, which occur as cements in primary and secondary voids, as well as in fractures. In some layers, especially at the top of the succession there occurs additionally secondary Fe-chlorite and pyrite. The Fe-carbonates were formed during upward migration of a reducing, iron-bearing, petroliferous fluid that was depleted in 13C and carried radiogenic Sr. Similar geochemical covariance and/or correlations can be expected in other sedimentary successions affected by the migration of petroliferous formation fluids.

Mineralogical and Geochemical Compositions of the Lopingian Coals in the Zhongliangshan Coalfield, Southwestern China

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.

Comparison of the microbial community composition of pristine rock cores and technical influenced well fluids from the Ketzin pilot site for CO 2 storage

Abstract: Two geological formations at the CO2 storage pilot site in Ketzin (Germany) were geochemically and microbiologically characterized to further evaluate changes resulting from CO2 injection. Well fluids were collected from both Stuttgart (storage formation, ~650 m depth) and Exter Formations (~400 m depth, overlying the caprock) either through pump tests or downhole samplings. Rock samples were retrieved during a deep drilling into the Exter Formation and primarily comprised quartz, ferrous dolomite or ankerite, calcite, analcime, plagioclase and clay minerals, as determined through X-ray diffraction analyses. In the rocks, the total organic carbon (TOC), which potentially contributes to microbial growth, was mostly below 1000 mg kg−1. The geochemical characterization of fluids revealed significant differences in the ionic composition between both formations. The microbial characterization was performed through fluorescence in situ hybridization and 16S rRNA gene fingerprinting. In the fluids obtained from the Stuttgart Formation, the microbial activity was affected by the relatively high TOC, introduced by the organic drill mud. The total cell counts were approximately 106 cells mL−1. The microbial community was characteristic of a saline deep biosphere environment enriched through increased carbon availability, with sulfate-reducing bacteria as the most abundant microorganisms (up to 60 % of total cells). Species belonging to halophilic/halotolerant Proteobacteria and Firmicutes were primarily detected. In Exter Formation rocks, Proteobacteria and Actinobacteria were detected. These data provide an explicit reference to further evaluate environmental changes and community shifts in the reservoir during CO2 storage and provide information for evaluating the storage efficiency and reliability.