کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10119968 | 1638615 | 2018 | 56 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Insights into the origin of coexisting A1- and A2-type granites: Implications from zircon Hf-O isotopes of the Huayuangong intrusion in the Lower Yangtze River Belt, eastern China
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
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چکیده انگلیسی
The origin of A-type granites has been the subject of great debate, especially the enigmatic synchronous A1- and A2-type granites. Cretaceous (~125â¯Ma) A1- and A2-type granites are common throughout the Lower Yangtze River Belt (LYRB), eastern China. However, their genesis still remains unclear. In this study, in-situ zircon Oisotopic data and chemical compositions of the Huayuangong (HYG) A-type granites in Anhui province, provide new insights into the origin and evolution of A-type granites in the LYRB, as well as the genetic link for synchronous A1- and A2-type granites. The HYG granites include syenogranite (75.9â¯wt%-76.6â¯wt% SiO2) and quartz syenite (66.1â¯wt%-66.9â¯wt% SiO2). Both are metaluminous and belong to ferroan series. They are characterized by high alkalis (K2Oâ¯+â¯Na2Oâ¯=â¯8.36â¯wt%-8.55â¯wt% and 11.7â¯wt%-11.9â¯wt%), high field strength elements (Zrâ¯+â¯Nbâ¯+â¯Ceâ¯+â¯Yâ¯=â¯909â¯ppm-1269â¯ppm and 1092â¯ppm-1329â¯ppm) and high Ga/Al ratios (10,000â¯ââ¯Ga/Alâ¯=â¯4.91-4.96 and 2.64-2.68). The zircon saturation thermometer results indicate high magmatic temperatures (896-964â¯Â°C and 860-882â¯Â°C). All those geochemical features show an A-type granite affinity. They can be further classified into A1-and A2-type granites, corresponding to reduced and oxidized A-type granites, respectively. Additionally, the in-situ zircon O-Hf isotope compositions are also distinctly different, with δ18Oâ¯=â¯4.7â°-6.0â° and εHf(t)â¯=â¯â1.5 to â3.6 for A1-type granites, and δ18Oâ¯=â¯7.0â°-7.8â° and εHf(t)â¯=â¯â3.3 to â6.9 for A2-type granites. The geochemical signatures and newly discovered δ18O and εHf(t)values of the two A-type granite subgroups, indicate that they were derived from different source components and under disparate physicochemical conditions (e.g.,temperature, redox state and water contents). Lithospheric mantle-like isotopic data from zircons of A1-type granites suggest fractional crystallization of reduced, anhydrous basaltic magmas resulting in the formation of A1-type granites. In contrast, A2-type granites with relatively high δ18O and negative εHf values were generated from partial melting of the lithospheric mantle which was metasomatized by slab-derived melts/fluids. The coexisting A1- and A2-type granites were formed under the extensional setting where lithospheric thinning and asthenosphere upwelling occurred.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volumes 318â319, October 2018, Pages 230-243
Journal: Lithos - Volumes 318â319, October 2018, Pages 230-243
نویسندگان
Xiao-Yan Jiang, Ming-Xing Ling, Kai Wu, Zhe-Kun Zhang, Wei-Dong Sun, Qing-Lin Sui, Xiao-Ping Xia,