Characteristics and tectonic significance of the early Paleozoic syenite granite from Jinchuan, Gansu Province

被引：0
|
作者：
Zhang X. [1 ]
Su S. [1 ]
Liu M. [1 ]
Wang W. [1 ]
机构：
[1] School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing
来源：
Earth Science Frontiers | 2021年 / 28卷 / 04期
关键词：
A-type granite; Bimodal intrusive rock; Jinchuan Cu-Ni (PGE) sulfide deposit; Tectonic setting; Zircon U-Pb age;
D O I：
10.13745/j.esf.sf.2020.7.7
中图分类号：
学科分类号：
摘要：
In this paper, the petrology, zircon SHRIMP U-Pb age and whole rock geochemical data of the Jinchuan syenite granite in Gansu Province were examined in order to determine the formation age, petrogenesis and tectonic environment of the pluton. The SHRIMP U-Pb weighted average age of magmatic zircons from syenite granite samples is (425.7±2.5) Ma (MSWD=1.07), belonging to the early Paleozoic Silurian and similar to the age of the exposed dolerite dikes in the Jinchuan area. The syenite granite is low in silicon (SiO2, 66.71 to 70.05%), rich in alkalis ((Na2O+K2O), 10.00 to 10.70%; K2O/Na2O ratio, 1.88-2.41), high in total iron (FeOT, 1.79 to 2.62%), low in titanium (TiO2, 0.34 to 0.52%), and metaluminous (A/CNK ratio, 0.82-1.05). Its petrology and chemical composition show that it belongs to the quasi-aluminous alkaline series A1 type granite, with a relatively high zircon saturation temperature (TZr, 878-1015 ℃). It has high contents of rare earth elements (REE) (ΣREE, (374.4-529.4)×10-6, averaging 428.7×10-6). The REE distribution curve shows relative enrichment of light REE and depletion of heavy REE by the right-inclined distribution; (La/Yb)N ranges between 28.07 and 41.28, with negative Eu anomaly (δEu, 0.53-0.66). The standardized primitive mantle spider diagram shows depletions of Nb, Ta, Ti and P. The rocks have relatively high Rb/Sr (0.81-1.27, averaging 1) and Rb/Nb (4.72-9.75, averaging 7.15) ratios, showing the compositional characteristics of crust-derived magma. Combined with regional tectonic evolution and tectonic discrimination, it is considered that the Jinchuan syenite granite is formed from partial melting of felsic material in the upper crust at high temperature, and the bimodal intrusive rocks, composed of dolerite dikes of the same age, are formed in an extensional intraplate rift environment and related to the subduction plate break-up and exhumation and asthenosphere mantle upwelling caused by the ~426 Ma Alashan block and the Qilian-Qaidam block. The Jinchuan syenite granite is formed by partial melting of felsic material in the upper crust at high temperature, and the bimodal intrusive rocks is formed in the extensional intraplate rift environment. The structural activity and hydrothermal mineralization of the Jinchuan Cu, Pt-rich orebody may be related to this magmatic activity. © 2021, Editorial Office of Earth Science Frontiers. All right reserved.
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页码：283 / 298
页数：15
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