Ankerite

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

Regional and Local Controls of Diagenesis Driven by Basin-Wide flow System: Pennsylvanian Sandstones and Limestones, Cherokee Basin, Southeastern Kansas

Abstract: The Cherokee basin in southeastern Kansas is a shallow cratonic downwarp adjacent to the Arkoma basin to the south and the Ozark uplift to theeast Nearbypre carbonates of theOzarks host several MVT leaddeposits that provide evidence of late Paleozoic basinal fluid invasion These carbonates constitute a prominent regional aquifer which extends into the Cherokee basin where it is confined by Pennsylvanian mud clastics and carbonates Thelate assemblage in Pennsylvanian sandstones and limestones is char acterized by a widespread dissolution event baroque ankerite orFe Ba sulfates and kaolinite Such an assemblage normally forms under 3 to 4 km of burial but the investigated strata have never been buried more than 1km This anomalous late diagenesis is interpreted to have been caused by regional fluid invasion and related advective heating which advanced the zone of extensive diagenesis towards the depths where alterations of the described type are not expected to be found Fluid inclusion studies indicate that the succession of late diagenetic fluids includes an earlierNa with salinities up to 25 wt NaCl eq and temperatures of80or higher followed by alater Na brine with salinities of about 19wt NaCl eq and temperatures up to 150Paragenetic trends defined byCa Mn Sr and stable isotopic composition oflate carbonate cements indicate early replacement of preexisting carbonates followed by dissolution of framework grains and earlier replacive phases and precipitation of several generations of baroque carbonates The overall progression from a morerock to a more water dominated system corresponds to the identified succession of late fluids and may reflect the regional evolution of the flow system Compositional differences between cements in sandstones and limestones reflect local lithologic control Late carbonate cements in limestones utilized local sources of Mg and Ca whereas cements in sandstones utilized local sources of Fe Mn and 12C bicarbonate The original chemistry of the incoming fluids was strongly modifiedby water interaction with local components therefore separation of local and regional signatures is akey in unraveling the evolution of basin flow systems

Alkali alteration styles and mechanisms, and their implications for a ‘brine factory’ source of base metals in the rift‐related McArthur group, Australia

Abstract: McArthur Group alkali metasomatism occurred in several phases, none of which fit a classic model of alkali‐mineral zonation towards an evaporitic basin centre as previously proposed. They comprise: (i) trough‐margin alteration along the Emu Fault Zone, formed by gravity‐driven meteoric‐evaporitic brines sourced from adjacent shelves, and focused up to 3.5 km out into the adjacent deeper water clastic succession of the Barney Creek Formation; these formed zoned albite‐microcline assemblages, variably overprinted by B‐bearing illite; (ii) ore‐related alteration at the HYC Zn‐Pb‐Ag deposit, which overprinted trough‐margin alteration in places, adding disseminated ankerite, adularia and base‐metal sulfides to some feldspathised beds; (iii) early diagenetic alkali metasomatism that was associated with descending/advecting brines sourced from overlying evaporite sequences, and transmitted through porous clastic sediments (e.g. parts of the Lynott Formation, Mara Dolomite and Tatoolla Sandstone); and (iv) extens...

Détermination des conditions de précipitation des carbonates dans une zone d'altération du granite de Soultz (soubassement du fossé Rhénan, France) : l'enregistrement des inclusions fluides

Abstract: A fluid inclusion study was carried out in quartz and ankerite veins (drillhole EPS-1, depth 1 641 m) of the Soultz-sous-Forets granite (geothermal exchanger). Homogenisation temperatures in quartz and ankerite lie in a narrow similar range and are consistent with the present-day in situ temperature measured in the well. Ankerite and quartz have precipitated in the same conditions, which appear to be general at the site scale in all observed alteration facies. Quartz and ankerite are likely to precipitate at present. The data suggest that the fluid probably has a pulsated mode of circulation.

Alteration and mineralization styles of the orogenic disseminated Zhenyuan gold deposit, southeastern Tibet: Contrast with carlin gold deposit

Abstract: Orogenic disseminated and Carlin gold deposits share much similarity in alteration and mineralization. The disseminated orogenic Zhenyuan Au deposit along the Ailaoshan shear zone, southeastern Tibet, was selected to clarify their difference. The alteration and mineralization from the different lithologies, including meta-quartz sandstone, carbonaceous slate, meta-(ultra)mafic rock, quartz porphyry and lamprophyre were researched. According to the mineral assemblage and replacement relationship in all types of host rocks, two reactions show general control on gold deposition: (1) replacement of earlier magnetite by pyrite and carbonaceous material; (2) alteration of biotite and phlogopite phenocrysts in quartz porphyry and lamprophyre into dolomite/ankerite and sericite. Despite the lamprophyre is volumetrically minor and much less fractured than other host rocks, it contains a large portion of Au reserve, indicating that the chemically active lithology has played a more important role in gold precipitation compared to structure. LA-ICP-MS analysis shows that Au mainly occurs as invisible gold in fine-grained pyrite disseminated in the host rocks, with Au content reaching to 258.95 ppm. The diagenetic core of pyrite in meta-quartz sandstone enriched in Co, Ni, Mo, Ag and Hg is wrapped by hydrothermal pyrite enriched in Cu, As, Sb, Au, Tl, Pb and Bi. Different host rock lithology has much impact on the alteration and mineralization features. Carbonate and sericite in altered lamprophyre show they have higher Mg than those developed in other of host rocks denoting that the carbonate and sericite incorporated Mg from phlogopite phenocrysts in the primary lamprophyre during alteration. The ore fluid activated the diagenetic pyrite in meta-quartz sandstone leading the hydrothermal pyrite enriched in Cu, Mo, Ag, Sb, Te, Hg, Tl, Pb and Bi, but the hydrothermal pyrite in meta-(ultra)mafic rock is enriched in Co and Ni as the meta-(ultra)mafic rock host rock contain high content of Co and Ni. However, Au and As shear similar range in both types of host rocks indicating that these two elements most likely come from the deep source fluid rather than the host rocks. It was shown in the disseminated orogenic gold deposit that similar hydrothermal alteration with mineral assemblage of carbonate (mainly dolomite and ankerite), sericite, pyrite and arsenopyrite develops in all types of host rocks. This is different from the Nevada Carlin type, in which alteration is mainly dissolution and silicification of carbonate host rock. On the other hand, Au mainly occur as invisible gold in both disseminated orogenic and Carlin gold deposits.

Genesis of the iron ores of the Pretoria series, South Africa

Abstract: Precambrian iron formations contain both banded and oolitic ores. Associated rocks include argillaceous and arenaceous beds, and volcanics. Detailed microscopic study suggests that ores were deposited as gelatinous iron hydroxides, iron-aluminum silicates, iron carbonate, and clastic quartz. Both shallow-and deeper-water environments are recognized. Diagenesis and metamorphism produced goethite, lepidocrocite, hematite, magnetite, chamosite, kaolinite, prochlorite, and ankerite. On the assumption that the atmosphere was oxidizing, solutions from terrestrial weathering are considered an inadequate source of dissolved iron, and a theory of submarine volcanic exhalations is favored.