LA-ICP-MS zircon U-Pb age of the Jinge plagiogranite in northern Fuyun of Xinjiang and its geological implications

LA-ICP-MS zircon U-Pb dating of the Jin'ge plagiogranite in northern Fuyun of Xinjiang shows that it was formed at 402.7±2.9Ma (MSWD=0.17). This age reveals that the rocks of the Jinge Plagiogranite were formed in the Early Devonian. The igneous petrotectonic assemblage of the Jin'ge rocks was probably related to oceanic subduction and belonged to TTG series of tonalite-trondhjemite-granodiorite. The granites show high-SiO₂, rich Na₂O and poor K₂O characteristics, with SiO₂ content ranging from 72.55% to 77.41%, Na₂O from 4.94% to 6.63%, K₂O from 0.24% to 0.95%. Al₂O₃ from 12.11% to 15.30% and A/CNK from 0.94 to 1.04, suggesting a suite of low-K calc-alkaline series rocks, being quasi-sialuminous-wearly per-aluminous Ⅰ-type granites. The Jin'ge plagiogranite is characterized by enrichment of LREE, depletion of HREE, and strong light and heavy REE fractionation, with weak to moderate Eu negative anomalies. The trace element geochemical characteristics of the pluton show enrichment of Rb, Th, U (LILE) and La, Ce, Sm and depletion of Nb, Zr(HFSE) and Sr, P, Ti, exhibiting features of magmatic rocks related to subduction. In combination with previous studies, the authors hold that the Jin'ge pluton was formed in a continental arc under an active continental margin setting, which was related to the oceanic crust subduction, and this area was locally extensional in the Early Devonian period.