| 黔西北毕节地区中二叠统碳酸盐岩岩石学、地球化学特征及意义 |
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| 关键词:carbonate rocks elemental and isotope geochemistry diagenetic alteration sedimentary environment Qixia–Maokou Formation Bijie area |
| 基金项目:贵州省科技计划项目(编号: 黔科合基础[2017]1407);贵州省高校优秀科技创新人才支持计划(编号: 黔教合KY字[2015] 504);贵州工程应用技术学院高层次人才科研启动基金项目(编号: 院科合字G2017006号);贵州省普通高等学校青年科技人才成长项目(编号: 黔教合KY字[2018]404; 黔教合KY字[2022]124);创新创业项目(编号: 202010668007) |
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| Petrological and Geochemical Characteristics and Their Significance of Middle Permian Carbonate Rocks in Bijie Area, Northwestern Guizhou |
| Based on field observations, thin section identification, and cathodoluminescence analysis, combined with elemental and isotope geochemical analysis, the petrological and geochemical characteristics of the Middle Permian carbonate rocks in northwestern Guizhou were studied. The results show that: 1) Grainstone and micritic limestone dominate the Middle Permian strata, and the rock samples exhibit weak to no luminescence. Dolomitization mainly occurs in the upper part of Qixia Formation and the first member of Maokou Formation; the dolomites have dark rose cathodoluminescence. 2) The carbonate rocks of Qixia–Maokou Formation are relatively rich in Ni, V, Cr and U, and poor in chalcophile elements. They generally have a left-leaning REE distribution pattern with low total REE (∑REE 2.11~8.10 μg/g), relative deficit of LREE, and relative enrichment of HREE. 3) The contents of elements such as Ti, Al, Zr, and Th, which are easily enriched in terrigenous components, are low. The low Mn content (<50×10–6) and Mn/Sr ratio (<1), combined with the characteristics of cathodoluminescence and REE composition, indicate that the Middle Permian carbonate samples in the study area are less affected or modified by terrigenous materials. The extremely low Re, Cd, Mo, U, Cu content and obvious negative Ce anomaly indicate that the environment of the study area was dominated by oxidation conditions during the Middle Permian. 4) The δ13CPDB and δ18OPDB ranges from 1.2‰ to 4.6‰ (mean 3.6‰), and from –7.4‰ to –10.1‰ (mean –9.08‰), respectively. There is no obvious correlation between δ13CPDB and δ18OPDB. The variation of carbon isotope is consistent with the transgression-regression cycle in the area, while the negative oxygen isotope is mainly the result of burial diagenesis. |
| LAN Ye-fang,REN Chuan-jian,LI Xiao-cai,REN Shu-ming,GAO Zhu.2022.Petrological and Geochemical Characteristics and Their Significance of Middle Permian Carbonate Rocks in Bijie Area, Northwestern Guizhou[J].Acta Geoscientica Sinica,43(3):309-324. |
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