Petrogenesis and Tectonic Implications of the Paiku Leucogranites, Northern Himalaya
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The Himalayan leucogranites provide insights into the partial melting behavior of relatively deeper crustal rocks and tectono-magmatic history of the Himalayan Orogen. The Paiku leucogranites of northern Himalaya can be subdivided into two-mica leucogranite (TML), garnet-bearing leucogranite (GL), cordierite-bearing leucogranite (CL), and tourmaline-bearing leucogranite (TL). All of them are high-K, peraluminous, calc-alkalic to alkali-calcic rocks. They are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), and show pronounced negative anomalies of Sr, Ba, K and Ti, but positive anomalies of Nb and Rb. LA-ICP-MS U-Pb zircon dating of one TML, one GL and two CL samples yielded variable 206Pb/238U ages ranging from 23.6 to 16.1 Ma, indicating the Paiku leucogranites underwent a low degree of partial melting process. Combining with previous studies, we suggest the Paiku leucogranites were derived from partial melting of metasedimentary rocks of the Higher Himalayan Sequence (HHS). The GL and TL mainly resulted from the muscovite-dehydration melting, whereas the TML and CL were mainly derived from the biotite-dehydration melting. Finally, it is concluded that the Paiku leucogranites were probably formed during the subduction of the Indian crust.
Key WordsPaiku leucogranites petrochemistry U-Pb geochronology dehydration melting tectonic implications northern Himalaya
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This study was supported by the National Natural Science Foundation of China (Nos. 41872070, 41802071, 41773026 and 41303028), and the China Geological Survey (No. DD20190053). We thank Zuolin Tian, Wangchao Li and Lei Tang for sample collecting. We thank two anonymous reviewers for constructive and critical reviews that helped to improve the manuscript significantly. The final publication is available at Springer via https://doi.org/10.1007/s12583-019-1219-8.
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