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Ankerite
About: Ankerite is a research topic. Over the lifetime, 859 publications have been published within this topic receiving 23960 citations.
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TL;DR: In this paper, the development of a sequential extraction procedure for iron in modern and ancient sediments is presented, which recognizes seven operationally derived iron pools: (1) carbonate associated Fe (Fe carb ), including siderite and ankerite; (2) easily reducible oxides (Fe ox1 ), including ferrihydrite and lepidocrocite; and (3) reducible Oxides(Fe ox2 ), including goethite, hematite and akaganeite, (4) magnetite (Fe mag ); (5)
975 citations
TL;DR: In this paper, a diagenetic model is proposed which involves the breakdown of detrital K-feldspar and of some smectite layers in illite/smectite to convert other smectitite layers to illite.
Abstract: Sandstones and shales of the Wilcox Group (lower Eocene) in southwest Texas were examined by X-ray powder diffraction, electron microprobe, and petrographically to interpret their diagenetic history. Samples analyzed are from depths of 975 to 4650 m, representing a temperature range of 55°C to 210°C. No consistent trend of depositional environments is recognized with increasing depth, and mineralogic changes observed are interpreted as diagenetic. Major mineral distribution patterns are (1) disappearance of discrete smectite at temperatures >70°C, (2) gradation of mixed-layer illite/smectite to less expandable (more illitic) illite/smectite over the entire temperature range, (3) disappearance of kaolinite from 150-200°C accompanied by an increase in chlorite, and (4) replacement of calcite cement at about 117 120°C by ankerite. Calculations based on data of Hower and others (1976) indicate that the stability of smectite layers may be a function of composition. Smectites with high ratios of octahedral (Fe + Mg)/Al appear to resist conversion to illite until temperatures high enough to produce ordering are attained. A diagenetic model is proposed which involves the breakdown of detrital K-feldspar and of some smectite layers in illite/smectite to convert other smectite layers to illite. Silica and calcium released by the illitization of smectite is transferred from shales to sandstones to produce quartz overgrowths and calcite cements at temperatures as low as 60°C. Iron and magnesium released by the illitization reaction are transferred from shales to sandstones at temperatures >100°C and react with kaolinite to produce high-alumina chlorite and/or with calcite to produce ankerite.
833 citations
TL;DR: In this paper, an empirically derived relationship between the chemical composition of a carbonate in the CaCO3-(Ca, Mg)(CO3)2-FeCO3 system and the function 103 In α at 100°C is 103 ∆ α = 8.94XCaCO3 + 9.29XMgCO3+ 8.77XFeCo3 where Xi is the mole percent of component i in the carbonate.
768 citations
TL;DR: In this article, the authors analyzed the impact of CO2 immobilization through carbonate mineral precipitation in aquifers, and found that the amount of CO 2 that may be sequestered by precipitation of secondary carbonates is comparable with and can be larger than the effect of dissolution in pore waters.
549 citations
TL;DR: In this article, a conceptual model of CO2 injection in bedded sandstone-shale sequences has been developed using hydrogeologic properties and mineral compositions commonly encountered in Gulf Coast sediments.
443 citations