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首页> 外文期刊>Journal of structural chemistry >COMPOSITION AND STRUCTURE OF LOW-TEMPERATURE NATURAL CARBONATES OF THE CALCITE-DOLOMITE SERIES
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COMPOSITION AND STRUCTURE OF LOW-TEMPERATURE NATURAL CARBONATES OF THE CALCITE-DOLOMITE SERIES

机译：方解石-白云母系列低温天然碳酸盐的组成与结构

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摘要

Mineralogical and crystallochemical studies of endogenic carbonates from bottom sediments of some shalllow saline lakes of Western Transbaikalia are performed. X-ray diffraction (XRD), IR spectroscopy, electron microscopy, elemental analysis (SR XFA), analysis of stable δ~(18)O and δ~(13)С isotopes, and other methods are applied. By modeling the complex XRD profiles by means of the Pearson VII function Mgcalcites with different Mg concentrations and Сa-excess dolomites are found in the assemblage of carbonate minerals. It is shown that in a series of Mg-calcites there is a gap in the region 2θ CuK_α = 30°, which is caused by a transition from the structures representing true solid solutions to the structures of layered “domain” nanosized crystals. The idea of excess-Са dolomite as the extreme member of the Mgcalcite series is substantiated. The carbonate record containing data on the stratigraphical distribution of endogenic carbonates of the calcite–dolomite series is obtained. The amount and ratio of phases with different Mg concentrations in this series are determined by the value of the Mg/Ca ratio, the total salinity and alkalinity of lake waters in the past, changing in accordance with climate cycles and fluctuations of the lake level.
机译：进行了西拜拜卡利亚西部一些须洛盐湖底部沉积物中内生碳酸盐的矿物学和晶体化学研究。应用了X射线衍射（XRD），红外光谱，电子显微镜，元素分析（SR XFA），稳定的δ〜（18）O和δ〜（13）С同位素分析等方法。通过利用Pearson VII函数对复杂的XRD分布图进行建模，可以在碳酸盐矿物的组合物中发现具有不同Mg浓度的Mg方解石和过量的α-a白云石。结果表明，在一系列的Mg-方解石中，在2θCuK_α= 30°区域存在一个间隙，这是由于从代表真实固溶体的结构过渡到层状“畴”纳米晶体的结构而引起的。过量钙白云石作为Mgcalcite系列的极端成员的想法得到了证实。获得了包含方解石-白云石系列内生碳酸盐地层分布数据的碳酸盐记录。该系列中镁含量不同的相的数量和比例取决于Mg / Ca比值，过去湖水的总盐度和碱度，并随气候周期和湖面波动而变化。

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