Abstract

Wide variations of ⁸⁷Sr/⁸⁶Sr (0.70825‒0.70924) have been established at the Porozhinsk deposit in manganese ores and carbonates ascribed to the Pod’’emsk Formation. These data, together with variations in the carbon (δ¹³C = –14.6…2.0‰, PDB) and oxygen (δ¹⁸О = 19.4…28.3‰, SMOW) isotope composition indicate different conditions of the formation of the studied rocks. The ⁸⁷Sr/⁸⁶Sr values in the studied dolomites of the Porozhinsk deposit are much higher than those of carbonate rocks (dolomites, limestones) of the Pod’’emsk Formation from the Chapa River section. The position of the ⁸⁷Sr/⁸⁶Sr values of dolomites from the Porozhinsk deposit on the secular ⁸⁷Sr/⁸⁶Sr variation curve for Late Proterozoic ocean (Kuznetsov et al., 2014) suggests that the carbonate rocks attributed to the Pod’’emsk Formation at the Porozhinsk deposit have younger age than carbonates of the Pod’’emsk Formation from the Chapa River section. The Mn/Sr values usually taken as a criterion for the degree of secondary alteration of carbonates (in interpreting ⁸⁷Sr/⁸⁶Sr variations and discussing the suitability of the material for chemostratigraphic constructions) are not suitable for rocks formed in manganese ore sedimentation basins.

中文翻译：

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波罗津斯克矿床（叶尼塞海脊，克拉斯诺亚尔斯克地区）岩石和矿石的锶同位素组成

摘要

在 Pod'emsk 组的锰矿石和碳酸盐中，波罗津斯克矿床的⁸⁷ Sr/ ⁸⁶ Sr (0.70825‒0.70924) 的变化很大。这些数据，连同碳（δ ¹³ C = –14.6…2.0‰，PDB）和氧（δ ¹⁸ О = 19.4…28.3‰，SMOW）同位素组成的变化表明研究岩石形成的不同条件。波罗津斯克矿床研究的白云岩的⁸⁷ Sr/ ⁸⁶ Sr 值远高于查帕河段 Pod'emsk 组的碳酸盐岩（白云岩、石灰岩）。⁸⁷ Sr/ ⁸⁶的位置^{晚元古代海洋长期87} Sr/ ⁸⁶ Sr 变化曲线上波罗津斯克白云岩的 Sr 值（Kuznetsov 等，2014）表明波罗津斯克矿床 Pod'emsk 组的碳酸盐岩年龄更小比来自查帕河段的 Pod'emsk 组的碳酸盐。Mn/Sr 值通常作为碳酸盐次生蚀变程度的标准（在解释⁸⁷ Sr/ ⁸⁶ Sr 变化和讨论材料对化学地层结构的适用性时）不适用于锰矿沉积盆地中形成的岩石。