Ankerite

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

Evidence for superstructuring in ankerite

Abstract: Ankerite from the Radmer-Buchegg and Erzberg mines, Austria, were studied by high resolution electron microscope imaging and selected area diffraction. Electron diffraction data suggest the presence of a periodic antiphase structure. The unit cell of the periodic antiphase structure of ankerite consists probably of three units: CaMg(CO3)2 as a basal unit, CaFe(CO3)2 and CaCO3. The last CaCO3 unit is connected with excess of Ca in ankerite. The upper size limit of CaFe(CO3)2 domains is 20–40 nm according to dark-field image study. Other rhombohedral dicarbonates (Zn-dolomites, Fe-poor ankerites) have probably also domain structure. The size of domains seems to be controlled by the value of misfit of domain lattice to the host lattice and by the value of octahedral distortion of units of the periodic antiphase structure.

An Isotope Study of the Dzhida Mo–W Ore Field (Western Transbaikalia, Russia)

Abstract: The Dzhida ore field includes Pervomaika (Mo), Inkur (W) and Kholtoson (W) deposits. This article presents stable and radiogenic isotopic data (O, C, D, S, Sr and Nd) in an attempt to better understand the petrogenetic processes and the problem concerning the sources of ore-forming fluids. Granites from the Pervomaika deposit, which includes Mo-ores, as well as the syenite dikes that precede W-mineralization, have low δ18O values (about 5‰ and 4‰ respectively), and low initial ratios 87Sr/86Sr (0.704–0.705). The eNd (T) values (+0.9–−1.1) in granites and syenites are close to the evolution trend of the mantle-derived source. It was determined that a mantle-derived source was involved in ore-forming processes. It was also confirmed that δ34S values in sulfide minerals (molybdenite, pyrite, sphalerite, galena, and chalcopyrite) were close to the meteoric standard (from −2‰ to +2‰). The δ13C and δ18O values in carbonate minerals (rhodochrosite and ankerite) of the Kholtoson deposit are located within the primary igneous carbonatite (PIC)-square, as a possible juvenile source of CO2. This was also confirmed by the δ18O and δD values in muscovite from greisens (4.2‰–6.5‰ δ18O, –78.8‰ … –84.0‰ δD). The δ18O values calculated in a fluid equilibrated with hydrothermal minerals indicated a meteoric origin.

Phosphorite from the upper continental slope off Kachchh, northwest coast of India

Abstract: Flat slabs and irregular lumps (1 to 3 cm) of brown, grey, black phosphorites and creamy white limestone (2 ta 4 cm) were recovered from 473 and 501 m depths from the upper continental slope off Kachchh. Phosphorites contain phosphatised skeletal fragments of shallow water origin, calcitic patches and phosphatised black peloids set in dark brownish microsphorite. Limestone contains fragments of foraminifera set in micrite. Carbonate fluorapatite, carbonate hydroxylapatite, ankerite, calcite in phosphorites and high magnesium calcite in limestone are the major minerals. Electron microprobe studies indicate the presence of Ca, P, Mg, Si, Al, K, Fe, S and Ti in phosphorites. P 2 O 5 content ofphosphorites and limestone are 29.42% and 11.76% respectively. It is suggested that the phosphatization is an early diagenetic process took place in shallow water condition most likely during the Quaternary period. Subsequently, tectonic changes brought them to the present site and thus occurring as relict phosphorites.

Spoiwa węglanowe skał klastycznych czerwonego spągowca w kujawsko-pomorskim segmencie strefy T-T

Abstract: Wypelnienia przestrzeni porowych, w piaskowcach i zlepiencach przez mineraly weglanowe, stanowią jeden z wazniejszych skladnikow spoiw skal czerwonego spągowca. Najpospolitszymi mineralami weglanowymi są kalcyt i dolomit, sporadycznie ankeryt. Analiza katodoluminescencyjna i zastosowanie mikrosondy elektronowej pozwolilo na wyroznienie dwoch odmian kalcytu (ryc. 2–5): czysty — nie wykazujący luminescencji i nie zawierający domieszek innych pierwiastkow oraz kalcyt manganonośny. Wyniki oznaczen izotopowych w tych mineralach pozwolily określic przyblizone temperatury ich krystalizacji:26°–38°C i 40°–62°C. Sugerują one istnienie co najmniej dwoch epizodow cementacji badanych osadow czerwonego spągowca. Rowniez spoiwo dolomitowe (ryc. 6–9) tworzylo sie glownie w dwoch przedzialach temperatur: 1) 39°–44°C i 2) 58°–82°C. Dolomity krystalizujące w wyzszych temperaturach zaliczono do poźnodiagenetycznych, co wydaje sie potwierdzac obecnośc dolomitu barokowego w osadach z otworu wiertniczego Budziszewice IG1. Cement ankerytowy powstawal rowniez w poźnej fazie cementacji weglanowej. CARBONATE CEMENTS OF THE ROTLIEGEND CLASTIC ROCKS IN THE KUJAVIAN-POMERANIAN SEGMENT OF THE T-T ZONE. Summary Carbonate filling of the pore space in sandstones and conglomerates represents one of the most important constituents of cements in the Rotliegend rocks. The following minerals are the most common: calcite and dolomite, sporadically ankerite. Two calcite varieties (Figs. 2-5) have been distinguished as a result of the cathodoluminescence analysis and microprobe studies, namely: pure calcite - nonluminescent and without impurities; Mn-bearing calcite. Isotope determinations allowed to indicate approximate temperatures of mineral crystaltization which were: 26°- 38°C; 40°- 62°C. These facts suggest at least two cementation episodes of the Rotliegend rocks. In general, the dolomite cement (Figs. 6-9) also formed in two temperature ranges: 39°-44°C and 58° -82°C. The dolomites that crystallized in the higher temperatures are late diagenetic. This is confirmed by the presence of a baroque dolomite in the rocks recorded in the Budziszewice IG 1 borehole. The ankerite cement formed in the late phase of carbonate cementation, too.