Ankerite

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

Metal concentrations and concomitant metal mobility in unsaturated mine and mill wastes

Abstract: The shallow sediments in the Smelterville Flats portion of the Coeur d'Alene River Valley in north Idaho consist of a heterogeneous mixture of mine wastes and alluvium reworked during flood events. The wastes cover an area of approximately eight square kilometres. Atomic Absorption Spectroscopy and Inductively-Coupled Plasma analyses on mine waste-sediment samples collected to the depth of the water table show maximum metal concentrations of about 20% Fe, 12% Pb, 10% Zn, 3% Mn, 2.8% Al, 0.13% Cu, 0.1% Cd, 370 ppm As, 170 ppm Ag, 150 ppm Sb, and 70 ppm Ni. The positive correlation between Fe, Ca, and Mg concentrations and sample pH suggests that the carbonate gangue minerals (siderite, ferrodolomite, and ankerite) control the pH. Other metals that exhibit a positive correlation with sample pH also may be present in the carbonate minerals. Identification of factors that govern metal mobility suggests that: (a) the pH of the water in the uppermost aquifer plays a minor role in controlling the solubility of most metals in the solid waste samples; b) the carbonate gangue minerals buffer the ground water pH and hence the solubility of metal sulfides; c) solubility of the carbonate gangue minerals decreases under anaerobic conditions, thereby allowing the ground water pH to decrease; d) solubility of Pb, Zn, and Cd correlates directly to anaerobic conditions as opposed to aerobic conditions.

Geochemistry of the Dome Mine Ankerite Veins: Insights into the Multi-Stage Enrichment of a World-Class Orogenic Gold Deposit

Abstract: ii Co-Authorship Statement iii Dedication iv Acknowledgments v Table of

Mineralogical and geochemical characteristics of the Zaccar Fe-(Ba-Pb-Zn-Cu) deposit in Ain Defla, Algeria (Northwestern Algeria)

Abstract: The Zaccar metasomatic-type iron deposit in Northwestern Algeria is hosted in Jurassic carbonate sequences proximal to Neogene volcanic rocks. The deposit consists of iron carbonates and oxides, associated with minor polymetallic sulfide and sulfate minerals. Microscopic observation, X-ray diffractometry (XRD), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS), fluid inclusion microthermometry, atomic absorption spectrometry (AAS), and inductively coupled plasma mass spectrometry (ICP-MS) were conducted on ores and host rocks to clarify mineralogical and geochemical the Zaccar iron deposit. Analyses indicate that the carbonate rocks show light rare-earth element (LREE)-enriched REE patterns with a Eu negative anomaly and almost no negative Ce anomaly, suggesting a shallow submarine depositional environment less than 100 m deep. Country limestone is partly replaced by the original epigenetic metasomatic ore of ankerite and siderite, associated with minor pyrite, chalcopyrite, galena, and barite. Abundant hematite was formed by supergene enrichment of iron carbonates controlled by groundwater level at low to medium temperature. The iron oxide mineralization indicates the positive Eu anomaly, lack of Ce anomaly, high Nd/Yb ratio, and high Eu/Sm ratio, which suggests a hydrothermal signature of iron carbonates as epigenetic mineralization, confirming replacement phenomena. The genesis of this kind of iron mineralization is likely related to basinal brines; a second type of iron oxide is represented by specularite (=high temperature variety of hematite) hosted in rhyolite of Miocene age. The microthermometry conducted on fluid inclusions trapped in quartz associated with specularite indicates high temperature and salinities (300 to 320 °C, 38 to 40 wt% NaCl eq), suggesting that specularite was formed by hydrothermal activity related to Neogene volcanism, evolved from the mixing of magmatic and meteoric waters.

Ferroan dolomites in Miocene sediments of the Xisha Islands and their genetic model

Abstract: Carbonate rocks are important reservoirs for global petroleum exploration. The largest oilfield in the South China Sea, Liuhua 11-1, is distributed in the massive carbonate reef area of the Zhujiang (Pearl) River Mouth Basin. Previous studies showed that one 802.17-m-long core from well Xichen-1 in the South China Sea mainly consisted of white and light gray-white organic reefs. Recently, a Miocene whole core (161.9 m long) of well Xiyong-2, near well Xichen-1, was found to contain six layers of yellowish brown, light yellowish gray, iron black, or light yellowish gray-white organic reefs. Scanning electron microscope images of these layers reveal a typical ferroan dolomite rich in Fe (up to 29%), with the high concentrations of Mn, Cu, W, Zn, Cr, Ni, and Co. Systematic X-ray powder diffraction analysis yields a 1.9–6.1 match in phase ratio with ankerite, 5.4–26.9 with dolomite, and zero with calcite, which indicate that the samples can be classified as ferroan dolomite. The iron and heavy metals are inferred to be originated from multiple volcanic eruptions of Gaojianshi Island in the Dongdao Atoll during the middle-late Miocene. These elements were dissolved in seawater, likely as a sol, and carried to Yongxing Island in the Xuande Atoll by sea currents and tides enhanced by prevailing winds, and deposited as a part of the sedimentation process in the study area. The ferroan dolomite has Sr content of (125–285)×10-6, which is lower than the accepted Sr boundary value of dolomite. This finding suggests that dolomitization occurred during large-scale global glacial regression in the late Miocene. The isolated Xisha carbonate platform, exposed to air, underwent freshwater leaching and dolomitization induced by mixed water, and caused the extensive Fe-Mg exchange along the organic reef profile to form ankerite and ferroan dolomite. These results may help to understand paleoceanographic environmental changes in the South China Sea during the Miocene.