| 滇西漕涧地区崇山杂岩带始新世花岗岩的发现及其地质意义 |
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| 关键词:Chongshan complex belt Eocene Pale granite Himalayan period late orogeny Caojian area western Yunnan |
| 基金项目:中国地质调查局地质调查项目“云南区域地质调查片区总结与服务产品开发”(编号: DD20160345-02);“云南1:5万归州;宝丰;漕涧;功果街幅区域地质调查”(编号: DD20160016-11);云南省地勘基金项目“云南1:5万马鸣村幅纳章幅越州幅陆良县幅区域地质调查”(编号: D201901) |
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| The Discovery of the Eocene Granite in the Chongshan Complex Belt of Caojian Area in Western Yunnan and Its Geological Significance |
| The Chongshan complex belt is an important boundary structure of the Sanjiang orogenic system in western Yunnan and belongs to the southeast edge of the Tibetan Plateau orogenic belt. Magmatic activities within the belt is strong, which was regarded by previous researchers as being mainly composed of granite in Late Proterozoic and Mesozoic magmatism. However, according to the geological survey, Cenozoic magmatism in the belt is well developed. In this paper, the newly discovered grayish white biotite granite in the belt, with the zircon U-Pb LA-ICP-MS ages being 34.88 Ma and 35.25 Ma, indicates that it intruded in Eocene of Paleogene. Rock geochemical studies show that the biotite granites belong to the peraluminous leucogranites series of potassium-high-potassium calc-alkaline nature, and the REE distribution curve is right-inclined. In the biotite granites, LREE is obviously enriched, HREE is depleted to varying extent with obvious negative Eu anomaly, Rb, Th, Ce, Sm are enriched but K, Ba, Ta, Hf, Y and other elements are depleted. According to zircon Hf isotope test and analysis, εHf(t) values are –2.35 ~ +2.33 and TDM2 values are 962~1259 Ma, indicating that the magma source area of granite was the product of crust-mantle mixing, and the source rock mainly came from the partial melting of Mesoproterozoic continental crust basement material. According to comprehensive research, the Eocene biotite monzogranite was formed in the transition stage from Himalayan collision orogeny to late orogeny, and it was a set of typical pale granites with “ultra-thick crust” partially melted and experienced crust-mantle interaction. The emplacement time represents the completion of Himalayan collision orogeny and the beginning of late orogeny in Caojian area, and the transition time is about 35 Ma. |
| HUANG Liang,PU Tao,LIU Jun-ping,WANG Xiao-lin,LIU Xiao-chun,XIONG Bo,SONG Dong-hu.2021.The Discovery of the Eocene Granite in the Chongshan Complex Belt of Caojian Area in Western Yunnan and Its Geological Significance[J].Acta Geoscientica Sinica,42(5):579-592. |
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