地质论评2025，Vol.71Issue(5)：1473-1494,22.DOI:10.16509/j.georeview.2025.01.015
浙东南望州山破火山口中A-型花岗岩的厘定及地质意义
Determination and geological significance of A-type granite from Wangzhoushan caldera in southeastern Zhejiang
摘要
Abstract
Objectives:The Wangzhoushan caldera is located in Cangnan,southeastern Zhejiang,and the main eruption products are Late Cretaceous rhyolites and rhyolitic pyroclastic rocks.The central intrusive body in the caldera is the typical alkaline granite,containing typical alkaline ferromagnesian minerals such as arfvedsonite and aegirine,and develop micrographic texture and miarolitic structure. Methods:Based on the field work,we conducted mineralogy,petrology,zircon U-Pb geochronology,whole-rock geochemistry,whole-rock Nd isotope and zircon Hf isotope studies for the Wangzhoushan alkaline granite. Results:LA-ICP-MS zircon U-Pb dating results show that the crystallization ages of alkaline granites are 91.30±1.10～90.43±0.76 Ma.The alkaline granites have high SiO2 contents(76.9％～77.9％),and alkalis contents(Na2O+K2O=7.80％～8.51％),and low CaO,MgO,Al2O3.They are rich in large ionic lithophile elements(LILE;e.g.Rb,K)and high field strength elements(HFSE;e.g.Nb,Ta,Zr,Hf),poor in Ba,Sr,P,Ti,and show high 10000Ga/Al values(3.82～4.28)and high zircon saturation temperature(798～889 ℃).Different samples of the Wangzhoushan alkaline granites have similar whole-rock Nd isotopic compositions[εNd(t)=-4.2～-3.8]and zircon Hf isotopic compositions[εHf(t)=-6.4～-1.7],indicating that the Wangzhoushan alkaline granites may be mainly derived by partial melting of crustal materials with minor contributions from mantle-derived components. Conclusions:The Wangzhoushan alkaline granites belong to the typical peralkaline A-type granite,which is another example found in the coastal areas of Zhejiang and Fujian Provinces.The magma generation of the Wangzhoushan alkaline granites and the contemporaneous coastal alkaline granites(101～86 Ma)in Zhejiang-Fujian is controlled by the subduction and rollback of the paleo-Pacific plate in the Late Cretaceous.Under the strong extensional tectonic setting,the depleted mantle-derived magma upwelled,resulting in the partial melting of the middle and lower crustal materials,and the magma of the high-silica peralkaline A-type granites were formed by the magma mixing and fractional crystallization processes.关键词
望州山破火山/碱性花岗岩/地球化学/岩石成因/中国东南沿海Key words
Wangzhoushan caldera/alkaline granite/geochemistry/petrogenesis/SE China引用本文复制引用
张志,褚平利,赵凯,贺振宇,徐夕生..浙东南望州山破火山口中A-型花岗岩的厘定及地质意义[J].地质论评,2025,71(5):1473-1494,22.基金项目
本文为国家自然科学基金重点项目(编号:41930214)的成果. This study was supported by the Key Projects of the National Natural Science Foundation of China(No.41930214) （编号:41930214）
