U-Pb dating of zircon, Hf isotope composition and tectonic significance of the albite-leptite of the Lancang Group in the Shuangjiang area of western Yunnan, China

被引：0
|
作者：
Han W. [1 ]
Peng Z. [2 ]
Zhang J. [1 ]
Guan J. [2 ]
Hu J. [1 ]
Liu Y. [1 ]
机构：
[1] Institute No.280, CNNC, Guanghan, 618300, Sichuan
[2] Chengdu Institute of Geology & Mineral Resources, China Geological Survey, Chengdu
来源：
Dizhi Xuebao/Acta Geologica Sinica | 2020年 / 94卷 / 04期
关键词：
Changning-Menglian combined belts; Hf isotope; Shuangjiang area of western Yunnan; The island-arc granite; The Lancang Group; U-Pb dating;
D O I：
10.19762/j.cnki.dizhixuebao.2020038
中图分类号：
学科分类号：
摘要：
The Lancang group, an important part of the Tethys orogenic belt, is located in the Changning-Menglian combined belt in the Sanjiang area of western Yunnan, China. In this paper, we have conducted zircon U-Pb dating, Hf isotope analyses and petrogeochemistry of albite-leptite to determine the genesis, chronology, and geotectonic evolution of the rocks in the Shuangjiang area. The detrital zircons with strongly oscillatory zoning employed for dating are of magmatic origin from albite-leptite. The U-Pb date, weighted average of 206Pb/238U, is 476.5±1.6 Ma, which is Early Ordovician (O1). The εHf(t) from the in-situ analysis of Hf isotopes is -5.6~-2.2 and the TDM c Age is 1591~1802 Ma indicating that the materials in the source area were formed by partial melting of ancient crustal materials from the terminal Early-Proterozoic to the early Middle-Proterozoic. According to petrogeochemical analysis, the original rock of albite-leptite is granitic diorite which is a peraluminous S-type granite with high SiO2=67.89%~68.91%, aluminum-rich Al2O3=14.48%~15.14% and high potassium calc-alkaline. The characteristics i.e. enrichment in LREE, the overall tilt to "right", δEu(0.60~0.64)and strong negative Eu, indicated that plagioclase has separated from the magma. The analysis shows that the original rock of albite-leptite is island-arc granite, which formed in the continent-arc collision stage around Changning-Menglian Tethys, has the same tectonic background as the volcanic rocks of the Huimin Formation in the Ordovician. As Tethys entered intracontinental subduction-grinding stage, the island-arc granite is a subduction accretionary complex, between the Changning-Menglian combined belts and the Lincang Batholith, forming tectonic sheet of the Lancang group. © 2020, Science Press. All right reserved.
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页码：1282 / 1294
页数：12
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