Permian-Triassic Magmatism in the Qin-Fang Tectonic Belt, SW China: New Insights into Tectonic Evolution of the Eastern Paleo-Tethys

IF 4.1 2区地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Journal of Earth Science Pub Date : 2023-12-12 DOI:10.1007/s12583-020-1111-6

Yun Zhou, Yongshan Zhao, Yongfeng Cai, Qiaofan Hu, Ce Wang

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Abstract

The granites of ambiguous geodynamic mechanism in the Qin-Fang tectonic belt (SW China) were studied in detail based on petrological, element geochemical, zircon U-Pb geochronological, and Hf isotopic data. LA-ICPMS U-Pb analyses on zircon yield ages of 248–245 Ma for the granites from the Qin-Fang tectonic belt. The geochemical data show that they are high-K, calc-alkaline, and peraluminous series. Their ε_Hf(t) values are from −14.01 to −7.75 with two-stage model ages of 1.74–1.43 Ga. These data, integrated with low Al₂O₃/TiO₂, Rb/Sr, Rb/Ba, and (Na₂O + K₂O)/(FeO^T + MgO + TiO₂) ratios, and high CaO/Na₂O ratios for the granite, suggest an origin from psammite source which was contaminated by mantle-derived components. These observations, in combination with the age data and stratigraphic records in the Jinshajiang, Ailaoshan, and Hainan Island areas suggest that the granites were formed in a post-collision tectonic setting. The Qin-Fang tectonic belt was likely a branched ocean basin of the eastern Paleo-Tethys.

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中国西南秦方构造带的二叠纪-三叠纪岩浆活动：东部古特提斯构造演化的新见解

基于岩石学、元素地球化学、锆石U-Pb地质年代和Hf同位素数据，对秦-坊构造带（中国西南部）中地球动力学机制不明确的花岗岩进行了详细研究。对锆石进行的 LA-ICPMS U-Pb 分析得出秦房构造带花岗岩的年龄为 248-245 Ma。地球化学数据表明，它们是高K、钙碱性和过铝系列。它们的εHf(t)值从-14.01到-7.75，两阶段模型年龄为1.74-1.43 Ga。这些数据与花岗岩中较低的Al2O3/TiO2、Rb/Sr、Rb/Ba和（Na2O + K2O）/（FeOT + MgO + TiO2）比率以及较高的CaO/Na2O比率相结合，表明花岗岩起源于被地幔成分污染的松散岩源。这些观察结果与金沙江、老山和海南岛地区的年龄数据和地层记录相结合，表明花岗岩是在碰撞后的构造环境中形成的。秦方构造带很可能是古泰西东部的一个分支洋盆。

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来源期刊

Journal of Earth Science 地学-地球科学综合

CiteScore

5.50

自引率

12.10%

发文量

128

审稿时长

4.5 months

期刊介绍： Journal of Earth Science (previously known as Journal of China University of Geosciences), issued bimonthly through China University of Geosciences, covers all branches of geology and related technology in the exploration and utilization of earth resources. Founded in 1990 as the Journal of China University of Geosciences, this publication is expanding its breadth of coverage to an international scope. Coverage includes such topics as geology, petrology, mineralogy, ore deposit geology, tectonics, paleontology, stratigraphy, sedimentology, geochemistry, geophysics and environmental sciences. Articles published in recent issues include Tectonics in the Northwestern West Philippine Basin; Creep Damage Characteristics of Soft Rock under Disturbance Loads; Simplicial Indicator Kriging; Tephra Discovered in High Resolution Peat Sediment and Its Indication to Climatic Event. The journal offers discussion of new theories, methods and discoveries; reports on recent achievements in the geosciences; and timely reviews of selected subjects.