Geochemical characteristics of late ordovician granodiorite in gouli area, eastern kunlun orogenic belt, Qinghai Province: implications on the evolution of proto-tethys ocean

被引：48

作者：

Chen J. ^{[1
]}

Fu L. ^{[1
]}

Wei J. ^{[1
]}

Tian N. ^{[1
]}

Xiong L. ^{[1
]}

Zhao Y. ^{[1
]}

Zhang Y. ^{[2
]}

Qi Y. ^{[3
]}

机构：

[1] Faculty of Earth Resources, China University of Geosciences, Wuhan

[2] Qinghai Institute of Geology and Mineral Resources, Xining

[3] No.8 Geological Team of Qinghai Nonferrous Metals Geological Exploration Bureau, Xining

来源：

Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2016年 / 41卷 / 11期

关键词：

Bidirectional subduction; Eastern Kunlun; Geochemistry; Kunzhong suture belt; Late Ordovician; Low-Mg adakitic granodiorite; Proto-Tethys Ocean;

D O I：

10.3799/dqkx.2016.129

中图分类号：

学科分类号：

摘要：

The Aowade granodiorited in the east-end of Kunnan terrain, a part of Kunlun Orogenic belt, belongs to Proto-Tethyan tectonic domain. Detailed study of the granodiorite can offer important information to constrain the evolution of the Proto-Tethys Ocean. Detailer study of the granodiorite can offer important information to constrain the evolution of the Proto-Tethys Ocean. In this study, LA-ICP-MS zircon U-Pb dating yields a weighted mean age of 454±2 Ma for the intrusion. It is characterized by low K2O/Na2O (0.92-2.68) and Mg# (39-43), and the A/CNK is between 1.00 and 1.03. The REE exhibits right-dipping patterns with negative anomalies of Eu/Eu*(0.48-0.96) and high (La/Yb)N ratios. LILE(Rb, Ba, K, La, Sr) is enriched in this intrusion, while HFSE(Nb, Ta, P, Ti) is depleted relative to the primitive mantle, and the concentrations of transition elements such as Cr and Ni are low. The ratios of Sr/Y (average of 55) are relatively high. All the samples have high initial 87Sr/86Sr values (0.705 9-0.706 3) and εHf(t) (+5.4 to +9.2), but with relatively low εNd(t)(-4.1 to -1.9) and old two stage model age (T2DMNd=1.3-1.5 Ga). In combination with the lithology, geochemical signature and isotopic compositions of the intrusion, we propose that the Aowade granodiorite was derived from melting of the subducted oceanic crust with minor involvement of continent crust. The possible residual of the source region is garnet amphibolite. Fractional crystallization of pyroxene, amphibole and plagioclase may have also occurred during the evolution of magma. Integrating evidences from the geodynamic setting of the Aowade granodiorite, the ophiolites in the Kunzhong structure zone, and the metamorphic rocks, arc-related igneous rocks on either side of the Kunzhong structure zone, it is concluded that the Aowade granodiorite was formed during the subduction of Proto-Tethys Ocean, which further reveals the nature of bidirectional subduction of the Proto-Tethys in the Late Ordovician. © 2016, Editorial Department of Earth Science. All right reserved.

引用

页码：1863 / 1882

页数：19

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