Showing papers on "Ankerite published in 1977"
01 Dec 1977
TL;DR: In this paper, the crystal structures of a dolomite and of an iron rich ankerite were refined from three-dimensional X-ray data by least squares methods toR∼0.03.
Abstract: The crystal structures of a dolomite and of an iron rich ankerite were refined from three-dimensional X-ray data by least squares methods toR∼0.03. The angle of rotation of the CO3 group is 6.35(5)o in dolomite but only 5.28(5)o in ankerite, a consequence of the different sizes of the (Mg, Fe)O6 octahedra. The carbonate group deviates very slightly from planarity in both minerals. The Ca−O distances are somewhat larger in both minerals than in calcite; the Mg−O distance in dolomite, on the contrary, is somewhat smaller than in magnesite.
33 citations
TL;DR: In this article, variable atmosphere differential thermal analysis (DTA) was used to detect the presence of anhydrous carbonate minerals in mixtures with other types of minerals using dynamic furnace atmospheres of CO2.
Abstract: GREATLY improved detection limits for the presence of anhydrous carbonate minerals in mixtures with other types of minerals can be obtained by variable atmosphere differential thermal analysis (DTA) using dynamic furnace atmospheres of CO2 (flow rate 100 ml min−1)1. Details will be published elsewhere2,3 (see ref. 1 for details of the Du Pont unit and conditions of analysis). These carbonates fall into two groups; those which decompose in CO2 with single, or multiple4 endothermic dissociation reactions liberating CO2. The first group contains, calcite CaCO3, magnesite MgCO3, smithsonite ZnCO3, and siderite FeCO3 (ref. 5); while the second includes dolomite CaMg(CO3)2, ankerite Ca(MgFe)(CO3)2 and cerussite PbCO3 (ref. 4). Here calcite and dolomite are taken as typical examples and their behaviour described.
25 citations
TL;DR: In this paper, the chemical compositions of 15 fissure ankerite crystals from the Steirische Erzberg were studied and the observed FeCO3-content of 33 mol% in several of the crystals lies, according to Rosenberg (1967), near the upper limit of the Fe-content possible for the Ankerite phase and requires a formation temperature of at least 450°C (at 2 − 3 kbar pressure).
Abstract: Conclusions concerning the minimum formation temperatures can be drawn from the chemical compositions of the 15 fissure ankerite crystals from the Steirische Erzberg which were studied. The observed FeCO3-content of 33 mol% in several of the crystals lies, according to Rosenberg (1967), near the upper limit of the Fe-content possible for the ankerite phase and requires a formation temperature of at least 450°C (at 2 – 3 kbar pressure). Of particular interest is the occurrence of zonal concentration gradients in the individual ankerite crystals.
7 citations