地质学报2017，Vol.91Issue(2)：334-361,28.
浙北湖(州)-安(吉)火山岩盆地:锆石U-Pb年代学、地球化学与岩浆成因
Huzhou-Anji Volcanic Basin of Northern Zejiang Province: Zircon U-Pb Dating, Geochemistry and Magma Genesis
摘要
Abstract
Located in the Huzhou-Anji volcanic basin in the northeastern margin of Zhejiang-Ganzhou volcanic rock belt,the volcanic/subvolcanic rocks consist dominantly of intermediate-felsic to felsic rocks with minor intermediate component and lack of mafic component,and represent a intermediate-felsic magmatic rocks series.The rocks are lithochemically characterized by high-K and rich alkali,suggesting that intermediate rocks belong to shoshonite series and the intermediate-felsic and felsic rocks belong to high potassium calc-alkaline series.In geochemistry,the volcanic rocks in the basin are enriched in large-ion lithophile elements (LILE) and light rare earth elements (LREE) and depleted in high field strong elements (HFSE) such as Nb,Ta and Ti.Major and trace elements variation regulation of the volcanic rocks reveals that fractional crystallization is the main mechanism of the magma evolution in the basin.Different mineral facies is produced at different stage of magma evolution,with plagioclase being the key mineral of fractionation and crystallization.Hornblende may be an important fractionation mineral during the intermediate to intermediate-feslic magma evolution,and K-feldspar and biotite minerals also play an important role in the fractionation of intermediate-felsic to felsic rocks.Our dating results show that the LA-ICP-MS zircon U-Pb ages of three episodes of volcanic activities in the basin are around 128～130 Ma,which fall within the error range,indicating that the main volcanic activities lasted for very short time.The SHRIMP zircon U-Pb dating yields an age of 136±1 Ma for the trachyandesite agglomerates,probably indicating small-scale weak mafic volcanic activities at the initial stage of the basin.It can be speculated that the Huzhou-Anji volcanic basin developed in a post-orogenic environment in the active continental margin,the magma formation was probably controlled by lithosphere delamination or subduction slab breakoff,with parent magma formed by partial melting of mafic lower crust material and with barely mantle material involvement,and the resulting andesitic-dacitic magma experienced strong fractional crystallization at the shallow magma chamber.关键词
锆石U-Pb定年/高钾钙碱性系列/橄榄玄粗岩系列/后造山环境/岩石圈拆沉/莫干山Key words
zircon U-Pb dating/high-K calc-alkaline series/shoshonite series/post-orogenic environment/lithosphere delamination/Mogan mountains引用本文复制引用
马芳,薛怀民..浙北湖(州)-安(吉)火山岩盆地:锆石U-Pb年代学、地球化学与岩浆成因[J].地质学报,2017,91(2):334-361,28.基金项目
本文为地质矿产调查评价专项项目(编号12120113094000,1212011121116)资助成果. （编号12120113094000,1212011121116）
