地质学报2017，Vol.91Issue(2)：315-333,19.
西大别芳畈花岗岩锆石U-Pb年龄、地球化学特征及其构造意义
Zircon U-Pb Age and Geochemistry of the Fangfan A-Type Granite in Western Dabie Mountains and Their Tectonic Significance
摘要
Abstract
Geochemical analysis and zircon LA-ICP-MS U-Pb dating for the Fangfan granites from two granitic bodies in western Dabie Mountains were conducted in this study.The geochemical characteristics of biotite granite and quartz syenite are generally similar,characterized by high SiO2 (ave.77.2％),peraluminous (A/CNK value between 1.03～ 1.13),alkalinity ratio (AR value between 5.43～7.23).REE analysis show that granites have an average ∑REE content of 62.4 × 10-6,an average (Ce/Yb)N of 0.67,an average (La/Yb)N of 0.97 and an average δEu of 0.20,an average Ga/A1 of 3.16 and an average Zr-+-Nb+ Ce + Y of 578.The chondirte-normalized REE pattern displays flat curves.The large ion lithophile elements,such as Rb,Th,U,K are relatively enriched,whereas high HFSE such as Nb,Ta,Sr and Ti are relatively depleted,which indicate residual plagioclase in the granite source area.Temperatures of zircon saturation and REE saturation concentration are around 833～877℃ and 773～862℃ respectively,indicating a high initial temperature of initial magma.These characteristics show that the Fangfan granites are typical of A-type granite formed in the intraplate extensional setting of middle-upper crust.LA-ICP-MS U-Pb dating analysis for zircons from two types of samples yielded an age of 773.0±1.6 Ma (MSWD =0.96,n=33) for biotite granite and 759.8±2.3 Ma (MSWD=1.6,n=28) for quarz syenite,indicating they formed in a tectonic background of Neoproterozoic ocean-continent subduction in the Nothern Yangtze block and was probably the product of magmatism of continental marginal arc.The Fangfan granites,which formed earlier than that of their wall rocks,is the transformed m lange belt by late tectonic,with its magmatism no direct relation with copper mineralization.关键词
芳畈花岗岩/锆石U-Pb年龄/西大别/扬子北缘/芳畈铜矿Key words
Fangfan granites/zircon U-Pb/LA-ICP-MS/western Dabie Mountains/northern Yangtze block/Fangfan copper ore引用本文复制引用
武昱东,王宗起,刘成新,贾少华,张玉涛,吴波,王刚..西大别芳畈花岗岩锆石U-Pb年龄、地球化学特征及其构造意义[J].地质学报,2017,91(2):315-333,19.基金项目
本文为国家自然科学基金项目(编号41402180)和国土资源部中国地质调查局项目(编号12120113069000)资助的成果. （编号41402180）
