Subducting sediment-derived arc granitoids: evidence from the Datong pluton and its quenched enclaves in the western Kunlun orogen, northwest China |
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| Authors: | Shi-Yong Liao Yao-Hui Jiang Shao-Yong Jiang Wan-Zhi Yang Qing Zhou Guo-Dong Jin Peng Zhao |
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| Institution: | 1. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210093, China
2. Xinjiang Institute of Geological Survey, Urumqi, 830000, China
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| Abstract: | This paper presents detailed SHRIMP zircon U–Pb chronology, mineral chemistry, major and trace element, and Sr–Nd–Hf isotope geochemistry of the Datong pluton and its quenched enclaves from the western Kunlun orogen, northwest China, in an attempt to achieve a better understanding on the origin of diverse arc magmas. The Datong host granitoids are intermediate to acid in composition (SiO2?=?57.5?~?73.1 wt.%), and exhibit high-K calc-alkaline to shoshonitic affinities. The quenched enclaves are silica-rich ultrapotassic rocks. Detailed SHRIMP zircon U–Pb dating indicates that the Datong pluton was emplaced in Ordovician time (473.4–447.7 Ma), which places the Datong pluton in an active continental margin setting, rather than a syn-collision setting of Early Silurian age. The Datong host granitoids were derived by partial melting of subducted sediments, with the subsequent melt interacting with the overlying mantle wedge during its ascent. Partial melting of the veined mantle wedge hybridized by sediment-derived melts generated the silica-rich ultrapotassic magma, which was injected into the Datong granitoid magma chamber and quenched, resulting in enclaves hosted by granitoids. This contribution provides evidence that arc magmas can be derived directly by partial melting of subducted sediments, which is helpful to further understand the origin of diverse arc magmas. |
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