Abstract

The Neoarchean–Early Paleoproterozoic section of the Eastern Sarmatia Kursk Block contains different formations: terrigenous-carbonate (Ignateevo Formation), terrigenous (Stoilo Formation), and banded iron (Korobki Formation). The Kursk Block sequences have obvious similarities to the coeval terrigenous-carbonaceous-ferriferous formations of the Kaapvaal and Pilbara cratons. The Ignateevo Formation dolomites are correlated with the Campbellrand–Malmani and Wittenoom–Carawine carbonate platforms. Carbonate rocks of all three cratons are silicified and show no evidence of clastic contamination. They are characterized by low Sr concentrations and are enriched in Fe and Mn. The REE distribution in carbonate rocks is characteristic of Neoarchean marine sediments: flat profiles on spider diagrams, positive La anomalies, absence of Ce anomaly, and increased Y/Ho ratios relative to the chondrite value. The values of δ¹³C (0.3–0.9‰ PDB) and δ¹⁸O (–10.1 to –13.0‰ PDB) in the Ignateevo Formation dolomites fall within the range of the Late Archean and Early Paleoproterozoic marine carbonate sediments. The ⁸⁷Sr/⁸⁶Sr ratio in the Ignateevo Formation dolomites (0.7101–0.7195) is higher than that in the Neoarchean marine carbonates, which implies either isolation of the paleobasin or disturbance of the Rb–Sr isotope systems during metamorphism. The Ignateevo Formation dolomites and calc-silicate rocks (intensively silicified dolomites) are closest in their isotope-geochemical characteristics to shallow-water dolomites of the Campbellrand–Malmani Platform (South Africa). Probably, the Ignateevo Formation dolomites and partly the formations composing the Campbellrand–Malmani Platform formed in the most isolated part of the paleobasin, which facilitated to their complete dolomitization and partial silicification.

中文翻译：

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东部Sarmatia（前寒武纪Ignateevo组，Kursk区块）的碳酸盐矿床：沉积条件和古大陆相关性

摘要

东萨马斯蒂亚库尔斯克块体的新古宙—早古元古代部分包含不同的地层：陆源碳酸盐岩（Ignateevo组），陆源碳酸盐（Stoilo组）和带状铁（Korobki组）。库尔斯克区块序列与Kaapvaal和Pilbara克拉通的同期陆源碳碳亚铁质地层具有明显相似性。Ignateevo组白云岩与Campbellrand–Malmani和Wittenoom–Carawine碳酸盐台地相关。所有三个克拉通的碳酸盐岩均被硅化，没有碎屑污染的迹象。它们的特征在于低的Sr浓度，并富含铁和锰。碳酸盐岩中的REE分布是新陈代谢海相沉积物的特征：蜘蛛图上的剖面平坦，La异常正，Ce异常不存在，以及相对于球粒陨石值增加的Y / Ho比。δ值¹³ C（0.3-0.9‰PDB）和δ ¹⁸ O（-10.1 -13.0到‰PDB）在Ignateevo形成白云石落入晚太古代和早古元海相碳酸盐沉积物的范围内。在⁸⁷ SR / ⁸⁶Ignateevo组白云岩中的Sr比（0.7101-0.7195）高于新古宙海洋碳酸盐，这意味着在变质过程中古巴辛的分离或Rb-Sr同位素系统的扰动。伊格纳特沃组白云岩和钙硅酸盐岩（强烈硅化的白云岩）的同位素地球化学特征最接近坎贝尔兰德-马尔马尼平台（南非）的浅水白云岩。Ignateevo地层的白云岩和部分由Campobarand-Malmani平台组成的地层可能形成于古巴辛的最孤立部分，这有助于其完全白云石化和部分硅化。