Ankerite

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

Rietveld Structure Refinement of the Stibnite Crystals from Herja (Romania) using X-ray Powder Diffraction Data

Abstract: The Herja area is located between Chiuzbaia Valley and Firiza Valley, about 5km NW of Baia Sprie town. From geological point of view the Herja perimeter belongs to the Neogene vulcanite zone of Eastern Carpathians, locally being situated in the Gutâi Mountains. The Herja ore deposit belongs to the Baia Mare Neogene metallogenetic district and is associated to a complex stock of Pannonian age [1]. In the Herja area are known sedimentary tertiary and Neogene magmatic formations. The sedimentary formations belong to the Eocene, Sarmatian and Pannonian. The Neogene magmatites are represented by volcanic products and by intrusive bodies. The volcanic products are represented by lava flows and subordinately, pyroclastic rocks. The vulcanites are represented by pyroxene and quartz andesites [1]. This ore deposit represented by hydrothermal veins oriented NE-SW, is located in andesitic eruptions from the Neogene period. The polymetallic mineralized veins contains a wide variety of metallic minerals: sphalerite, galena, pyrite, pyrrhotite, stibnite, chalcopyrite, arsenopyrite, jamesonite, tetrahedrite, semseyite, and nonmetallic minerals: quartz, siderite, ankerite, calcite, gypsum, baryte and vivianite. The hydrothermal veins show different types of structures: massive, rubanate, brecciated and concentric [2].

Elemental Gains and Losses during Hydrothermal Alteration in Awak Mas Gold Deposit, Sulawesi Island, Indonesia: Constraints from Balanced Mineral Reactions

Abstract: Hydrothermal gold mineralization is commonly associated with metasomatic processes resulting from interaction of hostrock with infiltrating hot aqueous fluids. Understanding of the alteration mechanism requires quantification of element changes in altered rock, relative to the unaltered or least-altered rock, representing the protolith. Balanced mineral reactions are used to gain quantitative insight into the alteration process associated with gold mineralization at the Awak Mas deposit. Three representative samples were carefully selected from the least-altered pyllite and the two alteration zones bordering the mineralization. Mineral mode, textural features, and mineral compositions were studied by microscopy and electron microprobe analyzer (EMPA). Quantitative modal analysis was performed with a Quanta 650 F QEMSCAN® system. The hydrothermal alteration sequence around the mineralization starts with the proximal albite–ankerite–pyrite alteration zone via the distal albite–chlorite alteration zone to the least-altered phyllite wall-rock. Balanced mineral reaction calculations were performed to evaluate elemental gains and losses. Most noticeable is the addition of Si, Na and Ca to each alteration zone. This alteration is represented by the almost complete replacement of muscovite by albite. The addition of Fe and S was highest in the albite–ankerite–pyrite alteration zone. Alteration of the least altered phyllite to the albite–chlorite zone involved a mass increase of 14.5% and a neglectable volume increase of 0.6%. The mass and a volume increase from the least altered phyllite to the albite–ankerite–pyrite zone was 40.5% and 0.47%, respectively. The very low volume change during alteration is also corroborated by the textural preservation indicating isovolumetric metasomatic reactions. The replacement of muscovite by albite may have had an important effect on the change of the rock failure mode from ductile to brittle, with consequences for the focusing of fluid flow.

Reactive Transport Modeling of CO2-Brine–Rock Interaction on Long-Term CO2 Sequestration in Shihezi Formation

Abstract: Carbon Capture and Storage (CCS) is attracting increasing scientific attention. Although experiments can explore the chemical process of CO2 sequestration, they are limited in time. CO2 geological storage will last hundreds and thousands of years, even much longer, so the numerical simulation method is used to conduct kinetic batch modeling and reactive transport modeling. The geochemical simulation tool—TOUGHREACT—is used to imitate CO2-brine–rock interactions at the Shihezi Formation in the Ordos basin. The mechanisms of CO2-brine–rock interaction and their effects on the reservoir are discussed, especially the change in structure and properties. K-feldspar and albite will dissolve as the main primary minerals. However, calcite and quartz will dissolve first and precipitate last. In addition, siderite and ankerite also appear as precipitation minerals. Mineral dissolution and precipitation will alter the formation of petrophysical parameters, such as porosity and permeability, which play significant roles in the geological storage environments. Although the CO2-brine–rock interaction rate may be small, it is an ideal way of geological storage. Regardless of what minerals dissolve and precipitate, they will improve the dissolution of CO2. The interaction between rock and brine with dissolved CO2 can promote the amount of mineralization of CO2, called mineral trapping, which has a positive effect on the long-term feasibility of CO2 storage.

Mossbauer spectroscopic study of iron minerals in coal near liquid helium temperature

Abstract: The method of using low-temperature Mossbauer spectroscopy to identify the iron species in coal is illustrated for sub-bituminous (AA5) and semi-anthracite (BZ) coals. The 4K spectrum of the AA5 sample exhibits besides pyrite and rozenite a magnetically split ferric component compatible with jarosite (H = 485 kOe). However, set of low-temperature spectra of the BZ sample, taken respectively at 9, 20, 30, and 40 K, indicate besides pyrite and szomolnokite other two relaxation sextets belonging to siderite and ankerite. Furthermore, analysis of iron by the method of atomic absorption spectroscopy and according to ASTM methods for coal showed the presence of organically bound iron (0.133% Fe) in the BZ sample. The existence of an organic iron in a coal sample is of a great importance, which will be inevitably discussed in this work.