| 西藏羌塘盆地双湖地区毕洛错黑色页岩稀土元素特征及地质意义 |
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| 关键词:Qiangtang Basin black shale rare earth element organic matter enrichment |
| 基金项目:国家自然科学基金青年科学基金项目(编号: 41902107)和甘肃省油气资源研究重点实验室开放基金(编号: SZDKFJJ2022002) |
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| REE Characteristics and Geological Implications of the Bilong Co Black Shale in the Shuanghu Area, Qiangtang Basin, Southern Tibet |
| The Bilong Co black shales in the Shuanghu area are most representative high-quality source rock in the southern Qiangtang Basin. They draw significant substantial attention in oil and gas exploration within the basin. This study focuses on the rare earth elements geochemical research present in the strata, where or-ganic matter originally accumulated at the base of the Bilong Co section. The findings reveal that the av-erage value of rare earth element (ΣREE) in the Bilong Co section amounts to 61.97 ?g/g. This value is significantly lower than that of the continental crust and North American Shale Composite. The ΣLREE/ΣHREE average ratio is 8.44, with the (La/Yb)N ratio averaging at 1.27. This indicates an enrich-ment in the light rare earth elements while experiencing a shortage of heavy rare earth elements. The δCe is 0.77–0.95, with a mean of 0.85, demonstrating a weak negative anomaly. The δEu is 0.90–1.11, with a mean of 1.00, indicating almost no anomaly. The NASC normalized pattern of black shale and the diagram of La/Th-La/Yb, Co/Th-La/Sc, La/Yb-ΣREE, and La/Th-Hf jointly suggest that the source rocks are mainly sedimentary rocks and felsic volcanic rocks. The changes in ΣREE, ΣLREE/ΣHREE, Al, Ti, and CIA demonstrate the enhancement of weathering and the increase of terrigenous input with the beginning of organic matter enrichment. The δEu, δCe,Ceanom, V/(V+Ni), and MoXS/UXS demonstrate the suboxic environment in the entire strata. (La/Yb)N, Nd/La, and ΣREE/P2O5 parameters reflect stable and high depo-sition rates. The major factor for organic matter enrichment is the increase in terrigenous input caused by enhanced weathering, as revealed from the analysis of the correlation between the deposition environ-ment index and TOC. Meanwhile, it is speculated that in the warm and humid climate of the Early-Middle Jurassic periods, nutrient influx from rivers fosters algae proliferation and provides organic matter. Simul-taneously, the high deposition rate and suboxic conditions favor the burial and preservation of organic matter, culminating in its enrichment. |
| SUN Yuqi,YI Fan,YI Haisheng,XIA Guoqing,LI Gaojie,XU Hongbin.2025.REE Characteristics and Geological Implications of the Bilong Co Black Shale in the Shuanghu Area, Qiangtang Basin, Southern Tibet[J].Acta Geoscientica Sinica,46(3):544-560. |
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