首页|Geochemistry and Zircon U-Pb and Hf Isotopes of Early Devonian Hardawu Granites in the Eastern Segment of the Ultrahigh-Pressure Metamorphic Belt, Northern Qaidam Basin
Geochemistry and Zircon U-Pb and Hf Isotopes of Early Devonian Hardawu Granites in the Eastern Segment of the Ultrahigh-Pressure Metamorphic Belt, Northern Qaidam Basin
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The Hardawu granites in the eastern segment of the ultrahigh-pressure metamorphic belt, the northern Qaidam Basin, were studied by whole-rock major and trace elements and in-situ zir-con U-Pb geochronology and Hf isotopes to discuss the petrogenesis and tectonic evolution. Geochrono-logical results show that the granites have a crystallization age of 401 ± 3 Ma, suggesting that they were formed in the Early Devonian. The granites have SiO2 contents of 75.32 wt.％-76.05 wt.％, total alkali contents of 8.23 wt.％-8.36 wt.％, and K2O/Na2O ratios of 1.62-1.91. They were rich in K2O, poor in TiO2, MnO, MgO, and P2O5, and have A/CNK values of 1.05-1.07, Rittmann index δ values of 2.05-2.14, and differentiation index (DI) values of 92.85-94.18. They are high potassium calc-alkaline, weak-peraluminum, and highly differentiated I-type granites. The granites also show enrichment of large ion lithophile elements (LILE) such as Rb, Ba, and Th, and depletion of high field strength elements (HFSE) such as Nb, Ta, and Ti. The total REE concentrations range from 169 ppm to 232 ppm, with en-richments of light rare earth elements and negative Eu anomalies (δEu = 0.39-0.55). The zircon εHf(t) values range from -0.65 to -2.29, and the two-stage model ages (tDM2) changed within a small range of 1.44 to 1.54 Ga, indicating that the magma of the Hardawu granites was originated from the partial melting of Mesoproterozoic lower crustal materials. Combined with previous studies, we suggest that the Hardawu granites were formed in the extensional tectonic setting after the collision between the Qa-idam Block and the central and southern Qilian Block in the Early Devonian.
Technology Innovation Center for Exploration and Exploitation of Strategic Mineral Resources in Plateau Desert Region, Ministry of Natural Resources, Xining 810000, China
Qinghai Geological Survey Institute, Xining 810000, China
School of Earth Science, China University of Geosciences, Wuhan 430074, China
Geological Exploration Institute of Shandong Zhengyuan, Jinan 271000, China
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Qinghai Provincial Geological Exploration Fund ProjectQinghai Provincial Geological Exploration Fund ProjectQinghai Provincial Geological Exploration Fund ProjectWestern Light Talent Program of China
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