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本文对印度南部卡纳塔克邦中晚元古代(10-20亿年前)Kaladgi群、Badami群与Bhima群的沉积碳酸盐建造的同位素进行了研究.Kaladgi群中白云岩与灰岩的δ~(18)C值(0.3±1.2‰[PDB])与先前根据地质学和沉积学所得出的结论相一致,即这套岩系为正常的海相碳酸盐沉积.而上覆的Badami群与Bhima群中的白云岩的δ~(13)C平均值却明显增高,其平均值为3.4±0.5‰[PDB],显示出与原始高盐度(蒸发)环境的成因联系.但是这两种碳酸盐的δ~(18)O值非常相似(分别为21.7±1.3‰和21.1±1.2‰[SMOW]),呈现出前寒武纪碳酸盐岩贫δ~(18)O的特征.
In this paper, the sedimentary carbonate isotopes of the Kaladgi, Badami and Bhima groups in the Middle and Late Proterozoic (10-20 billion years ago) in the state of Karnataka, southern India, were studied. The isotopic composition of dolomite and limestone in the Kaladgi Group The δ ~ (18) C value (0.3 ± 1.2 ‰ [PDB]) is consistent with previous conclusions based on geology and sedimentology that the suite is normal marine carbonate deposition, while overlying The δ ~ (13) C average values of the dolomites in the Badami group and the Bhima group increased significantly, with an average value of 3.4 ± 0.5 ‰ [PDB], indicating a genetic relationship with the original high salinity (evaporative) The δ 18 O values of the two carbonates are very similar (21.7 ± 1.3 ‰ and 21.1 ± 1.2 ‰ [SMOW], respectively), showing that the Precambrian carbonates are depleted in δ 18 O feature.