Zircon U-Pb geochronology,rock geochemical characteristics and genetic types of the Yucangshan—Pengxi alkali feldspar granite in Southeastern Zhejiang
Objectives:The Yucangshan—Pengxi pluton is geographically located in the southeastern part of Zhejiang Province,at the northern end of the granite belt along the eastern coast of China.Magmatic activity is constrained by the subduction of the Pacific Plate,and is also controlled by the Wenzhou Zhenhai Fault in the region,trending northeast.Methods:Based on the field investigation,We conducted microscopic observations,whole-rock geochemical analysis,and LA-ICP-MS zircon U-Pb dating for the Yucangshan—Pengxi alkali feldspar granite.Results:Two sets of high-precision dating data were obtained,with weighted average ages of 96.50±1.81 Ma and 98.27±0.39 Ma,respectively,indicating that the rock mass is a product of Late Cretaceous magmatic activity.Under the microscope,the main mineral composition of the rock mass is potassium feldspar(60％～69％),quartz(25％～35％),as well as a small amount of plagioclase(＜5％),biotite(＜2％),etc.,presenting a medium to fine-grained granite structure.The rock mass exhibits high Si,rich alkali,low Al;depleted in Mg,Ca,P,Ti,Fe.The samples are enriched in large ion lithophilic elements such as Rb,K,etc;as well as high field strength elements such as Th,U,Zr,and Hf,are enriched.The content of ferrophilic elements such as Co,Ni,Cr,and V is relatively low;The K/Rb ratio is low,while the Rb/Sr and Rb/Ba ratios are high;The total amount of rare earth elements is high,and the enrichment degree of light rare earth elements is much higher than that of heavy rare earth elements.At the same time,it has obvious europium negative anomalies and a high differentiation index;This reflects the strong crustal characteristics of the rock mass,and the high degree of differentiation in magma evolution during its formation.Conclusions:During the diagenesis process,minerals such as plagioclase and apatite were separated and crystallized,belonging to the peraluminous high potassium calcium alkaline granite series.Through exploration of the rock type and tectonic environment,it is believed that the rock mass belongs to A-type granite,which was formed by the upwelling of the asthenosphere mantle and partial melting of the crust in the late Cretaceous intraplate extensional tectonic environment.
zircon U-Pb datingrock geochemistrygranite typeconstruct the environmentYucangshansoutheastern Zhejiang
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维普
