皖南及邻区燕山期A_2型花岗岩地球化学特征及岩石成因  

Geochemical characteristics and lithogenesis of A_2-type granite in Yanshanian in South Anhui and its neighboring areas

作　　者：翁望飞[1] 支利庚[1] 徐生发[1] 蔡连友[1] 

机构地区：[1]安徽省地质矿产勘查局332队地调院,安徽黄山245000

出　　处：《地质学刊》2011年第2期134-142,共9页Journal of Geology

基　　金：安徽省国土资源厅公益性地质调查基金项目"闪里幅(H50E013014)1:5万区域地质矿产调查"(2010-g-11)

摘　　要：皖南及邻区早白垩世中—晚期酸性岩浆岩产于扬子陆块江南古隆起东段,岩体类型为花岗岩、碱长花岗岩及钾长花岗岩。岩体含有丰富的锆石、富F的萤石及富含稀土的磷钇矿、独居石、褐帘石等矿物。主量元素具较高含量的SiO2和K2O,较低含量的TiO2、MgO、CaO,高(Na2O+K2O)/Al2O3值,高FeOT/MgO比;富集REE(Eu亏损),HREE亏损不严重,稀土配分模式表现为海鸥型;明显富集Zr、Nb、Rb、Ta、Y、Yb,显著亏损Cr、Co、Ni、V、Ba、Sr。地化特征分析认为早白垩世中—晚期花岗岩为A2型花岗岩,产生于造山后的伸展环境,是正常安山质地壳在皖南印支期加厚地壳熔融结束之后继续受地幔物质底侵部分熔融所形成。The acidic magmatic rocks in middle to late period in Early Cretaceous in South Anhui and its neighboring areas were indigenous to eastern part of Jiangnan paleouplift on Yangtze landmass,and their types included granite,alkali feldspar granite and K-feldspar granite.The granites were rich in zircon,fluorite with F and monazite,allanite and hussakite with rare earth elements.The granites belonged to alkaline series with geochemical characteristics of much higher SiO2,K2O,lower contents of TiO2,MgO,CaO,higher values of（Na2O＋K2O） /Al2O3and FeOT/MgO ratio,and with enriched REE（Eu loss）,less depletion in HREE,and the distribution pattern of rare earth elements were sea gull-shaped.The trace elements were obviously rich in Zr,Nb,Rb,Ta,Y and Yb,and obviously loss in Cr,Co,Ni,V,Ba,and Sr.An analysis of geochemical characteristics of the granites in middle to late period of Early Cretaceous showed they were A2-type granites,formed in extensional environment after orogenesis,resulting from partial melting of andesitic crust after the formation of adakite.A-type granite played a big role in the enrichment of rare earth elements of W,Zr,Nb,Ta and U.Therefore,strengthening researches on A-type granite in South Anhui and its neighboring areas might provide a newidea and direction for the exploration of rare earth elements and rare metal deposits.

关 键 词：A型花岗岩 地球化学 岩石成因 构造环境 燕山期 皖南 

分 类 号：P581[天文地球—岩石学]