Geochemistry of I- and A-type granites of the Qingyang-Jiuhuashan complex, eastern China: Insights into early cretaceous multistage magmatism |
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The Lower Yangtze River Belt in eastern China preserves evidence for widespread Mesozoic magmatism. Geochronological and geochemical studies have been conducted on the magmatic rocks and their associated mineral deposits; however, the relationships and melting conditions of spatially associated I- and A-type granites remain poorly constrained. The Qingyang-Jiuhuashan granitic complex in southern Anhui Province, eastern China, comprises primarily hornblende-bearing granodiorite, monzogranite, alkali-feldspar granite, and granitic porphyry, which yield zircon U-Pb ages of 142.2 +/- 1.3,134.6 +/- 1.2,126.4 +/- 1.9, and 125.9 +/- 1.2 Ma, respectively. Zircon grains from an enclave in the monzogranite yield an age of 134.5 +/- 1.1 Ma, similar to that of the host rock. The ages are consistent with the timing of regional magmatic events in southern Anhui Province. Whole-rock geochemical compositions indicate that the granodiorite and monzogranite represent I-type granites, whereas the alkali-feldspar granite and granitic porphyry display A-type signatures. The I- and A-type granites yield similar whole-rock Sr-Nd isotopic compositions, but distinct zircon delta O-18 values. We infer that the I-type granites were produced through water-fluxed melting of Mesoproterozoic basement during subduction of the paleo-Pacific plate. The A-type granites were generated through partial melting of the lower crust, triggered by extensional upwelling of mantle-derived magmas that provided heat and alkali-rich fluids. We identify three stages of Cretaceous tectono-magmatic activity that occurred in response to ridge subduction and subsequent slab rollback beneath eastern China. (C) 2018 Elsevier B.V. All rights reserved. Publication name | LITHOS, 316 278-294; 10.1016/j.lithos.2018.07.025 SEP 2018 | Author(s) | Jiang, Xiao-Yan; Luo, Jin-Cheng; Guo, Jia; Wu, Kai; Zhang, Zhe-Kun; Sun, Wei-Dong; Xia, Xiao-Ping | Corresponding author(s) | JIANG Xiaoyan jiangxy@gig.ac.cn Chinese Acad Sci, Guangzhou Inst Geochem, CAS Key Lab Mineral & Metallogeny, Guangzhou 510640, Guangdong, Peoples R China. SUN Weidong weidongsun@qdio.ac.cn Qingdao Natl Lab Marine Sci & Technol, Lab Marine Mineral Resources, Qingdao 266237, Peoples R China. | Author(s) from IGCAS | LUO Jincheng | View here for the details
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