Crustal thickening prior to 220 Ma in the East Kunlun Orogenic Belt: insights from the Late Triassic granitoids in the Xiao-Nuomuhong pluton

Xia, Rui, Wang, Changming, Deng, Jun, Carranza, John, Li, Wneliang, and Qing, Min (2014) Crustal thickening prior to 220 Ma in the East Kunlun Orogenic Belt: insights from the Late Triassic granitoids in the Xiao-Nuomuhong pluton. Journal of Asian Earth Sciences, 93. pp. 193-210.

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The East Kunlun Orogenic Belt (EKOB) played an important role in plate tectonics, magma generation, and crustal evolution. Late Triassic granodiorites and their mafic micro-granular enclaves (MMEs) from Xiao-Nuomuhong in the EKOB were studied for geochemistry and geochronology to constrain their petrogenesis. Zircon LA-ICP-MS dating indicates that the Xiao-Nuomuhong granodiorites are coeval with their MMEs (~222 Ma). The granodiorites are high-K calc-alkaline rocks that are enriched in Rb, Th, U and LREE, and depleted in Cr, Ni and HFSE, with high Sr/Y ratios (82.2–85.3) and geochemically resemble the lower crust-derived adakites. The MMEs are also high-K calc-alkaline rocks, with high Al2O3 (16.8–18.8 wt.%), low Mg# (30–40), Nb, Zr and Hf, with weak negative Eu anomalies (Eu/Eu# = 0.8–0.9). We suggest the MMEs are mafic magmatic globules that were injected into the felsic host magma. The adakitic rocks from the Xiao-Nuomuhong pluton were generated by partial melting of thickened crust, while the primitive compositions of the MMEs were most likely from the lithospheric mantle beneath the EKOB. The Late Triassic Xiao-Nuomuhong pluton is important evidence that crustal thickening in the EKOB occurred prior to 220 Ma. The pluton is interpreted as the result of mixing between thickened lower crust-derived melts and lithospheric mantle-derived mafic melts and the protracted magmatic response to the break-off of the Paleo-Tethys oceanic slab at ~232 Ma.

Item ID: 35005
Item Type: Article (Research - C1)
ISSN: 1878-5786
Keywords: geochronology; geochemistry; adakite; mafic microgranular enclave; paleo-tethys; East Kunlun
Funders: National Basic Research Program of China (NBRP), Fundamental Research Funds for the Central Universities (FRFCU), China Geological Survey Program (CGSP), Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT), 111 Project
Projects and Grants: NBRP No. 2009CB421008, FRFCU No. 2652013034, CGSP No. 1212011220665, 111 Project No. B07011
Date Deposited: 24 Sep 2014 02:25
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040202 Inorganic Geochemistry @ 40%
04 EARTH SCIENCES > 0403 Geology > 040303 Geochronology @ 50%
04 EARTH SCIENCES > 0403 Geology > 040304 Igneous and Metamorphic Petrology @ 10%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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