浙江安吉多金属矿区石英二长斑岩岩石化学特征和锆石U-Pb年龄及其地质意义  

Geochemical Characteristics and Zircon LA-ICP-MS U-Pb Ages of Quartz-Monzonite Porphyry in Anji Polymetallic Ore District of Zhejiang and Their Geological Implications

作　　者：唐燕文[1] 谢玉玲[1] 李应栩[1] 邱立明[1] 刘保顺[1] 李媛[1] 张欣欣[1] 姜研岑[1] 韩宇达[1] 周俊杰[1] 

机构地区：[1]北京科技大学土木与环境工程学院,北京100083

出　　处：《现代地质》2012年第4期647-655,共9页Geoscience

基　　金：科技部公益性行业基金项目(201011011-01);"十二五"国家科技计划项目(2011BAB04B02)

摘　　要：为了解浙江安吉多金属矿区岩浆作用的性质及其与成矿作用的关系,对区内石英二长斑岩的地球化学和年代学展开研究。地球化学结果表明,该岩脉高硅(w(SiO2)=65.91%～66.72%)、富碱(w(K2O+Na2O)=7.82%～8.26%)、高钾(w(K2O)/w(Na2O)=1.58～1.82),铝饱和指数A/CNK=0.86～0.91,轻稀土元素和大离子亲石元素Rb、Th、K相对富集,铕弱负异常,Ba、Sr和高场强元素Nb、Ti、P相对亏损,属准铝质―钾玄岩系列。铝饱和指数及结晶分异指数显示,该岩脉属I型花岗岩系列。年代学结果表明,该岩脉锆石U-Pb年龄为(137.3±1.6)Ma,与区内杂岩体同期。据野外证据,该岩脉的侵位时代指示北东向湖州―学川大断裂在(137.3±1.6)Ma左右再次活动,且该时间也为北西向孝丰―三门湾大断裂再度活跃的最早年龄。区内岩浆作用、成矿作用基本同期,岩体与矿化又具有密切的空间关系,表明区内成矿作用和岩浆活动密切相关。In order to get further understanding about the magmatism and its relationship with mineralization,the geochemical characteristics and zircon U-Pb age of quartz-monzonite porphyry in Anji polymetallic ore district in western Zhejiang have been studied.Quartz-monzonite porphyry is characterized by high SiO2（65.91%-66.72%）,alkali-rich（Na2O＋K2O=7.82%-8.26%）,potassium-high（K2O/Na2O=1.58-1.82） and A/CNK=0.86-0.91.Based on the results from A/CNK-A/NK and SiO2-K2O diagrams,quartz-monzonite porphyry belongs to the quasi-aluminous rock and shoshonite series.In chondrite normalized REE distribution patterns,all the samples are LREE-enriched and with weak negative anomaly in Eu（δEu=0.75-0.81）.In primitive mantle normalized trace elements spider diagram,the large-ion lithophile elements（e.g.Rb,Th and K） are high concentrations,but Ba,Sr and the high field strength elements（e.g.Nb,Ti and P） are relatively depleted.The aluminized indexes（A/CNK） of all the samples are less than 1.1 and all the differentiation indexes（DI） are about 77,so quartz-monzonite porphyry belongs to I-type granite.Zircon U-Pb dating by LA-ICP-MS shows this porphyry emplaced at（137.3±1.6） Ma of Early Cretaceous and has a similar age with the Wushanguan complex.Considering that quartz-monzonite porphyry exists along Huzhou-Xuechuan fault and is cut off by Xiaofeng-Sanmenwan fault,this age indicates that Huzhou-Xuechuan fault was activated in Early Cretaceous and also constrains the earliest time when Xiaofeng-Sanmenwan fault activated.The magmatism formed in the same time with mineralization,and mineralization also has a close relationship with the complex body in space,so it is believed that the mineralization is related to the magmatism in this study area.

关 键 词：浙西 Pb-Zn多金属矿床 孝丰―三门湾大断裂 湖州―学川大断裂 锆石U-Pb定年 成矿时代 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]