Geochronology,Geochemical Characteris-tics and Tectonic Setting of the Early Jurassic Qincaitang Pluton in Xinfeng,Northern Guang-dong Province
To further study the characteristics of the Early Jurassic tectono-magmatic activities in South Chi-na,this paper conducts geochemical analysis and zircon U-Pb age dating on the Qincaitang pluton in the Xin-feng area of Northern Guangdong province.The SHRIMP zircon U-Pb dating result for the Qincaitang grano-diorite is 191.8±2.3 Ma,and the LA-ICP-MS zircon U-Pb dating result for the dioritic porphyrite veins devel-oped in the outer contact zone is 190.4±3.3 Ma,both of which belong to the Early Jurassic period.Geochemi-cal studies suggest that the rocks are characterized by quasi-alumina,high potassium calc-alkaline,with en-richment of large iron lithophile elements such as Rb and Th,as well as rare earth elements La,Ce and Nd.The rocks are relatively depleted in Ba,Sr,Nb,Ta,P and Ti with obvious Th-U peak,La-Ce peak and Ta-Nb trough,showing that rocks experienced magma crystallization differentiation during the diagenetic process,forming I-type granite from the basaltic rock melting in the lower crustal tectonic environment.This research indicates that the ancient Pacific plate subduction was probably initiated in the Early Jurassic,and therefore,South China was influenced by the Pacific tectonic domain during the Early Mesozoic,making the"intermit-tent period"of magmatic activity unlikely occur during the two major tectonic regime transitions in the Early Mesozoic.
Early Jurassic magmatic rockU-Pb geochronologygeochemistryQincaitang intrusionNorth-ern Guangdong Province
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