| 四川理塘地区二叠—三叠纪硅质岩的地球化学特征及地质意义 |
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| 关键词:paleofossils geochemistry sedimentary environment siliceous rocks Ganzi–Litang ophiolite melange belt |
| 基金项目:中国地质调查局项目(编号: 12120115041701) |
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| Geochemical Characteristics and Geological Significance of Permian–Triassic Siliceous Rocks in Litang Area, Sichuan Province |
| Located on the eastern margin of the "Three Rivers" region in Southwest China, the Ganzi–Litang ophiolite melange belt is an important part of the Yidun–Litang arc basin system, where a large number of siliceous rocks of different ages and types are developed. In this study, lots of conodonts in Middle Permian to Late Permian strata were found in the intercalated mudstone and marl of the siliceous rocks from Lijie Highway in Litang County, and Radiolaria in Middle Triassic strata was found in the siliceous rocks near Charichadong Village. Based on the study of the petrological and geochemical characteristics of siliceous rocks in the study area, the authors investigated the genetic type and sedimentary environment of siliceous rocks. The results show that the SiO2 content is 66.13%～85.89%, Al2O3 content is 4.69%～7.85%, Al/(Al+Fe+Mn) value is between 0.44 and 0.73, U/Th ratio is 0.10～0.19, and δCe value is 1.00～1.63, which indicates that the siliceous rocks are biogenetic. Al2O3/(Al2O3+Fe2O3) mass ratio is 0.52～0.79, MnO/TiO2 mass ratio is 0.05～0.27, ΣREE is (49.26～165.41)×10–6, 94.37×10–6 on average, (La/Yb)N ratio is 0.78～2.32, and (La/Ce)N ratio is 0.72～1.26, indicating that the rocks might have been formed in a continental marginal environment. The determination of Permian–Triassic continental margin siliceous rocks from Lijue Highway and Charichadong Village in Litang area not only enriches the material composition of the Ganzi–Litang ophiolite melange belt but also provides new evidence for the Permian–Triassic geological evolution of the Ganzi–Litang Ocean basin. |
| YAN Song-tao,TAN Chang-hai,QIN Meng,LI Hu,DUAN Yang-hai.2020.Geochemical Characteristics and Geological Significance of Permian–Triassic Siliceous Rocks in Litang Area, Sichuan Province[J].Acta Geoscientica Sinica,41(4):504-514. |
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