伊舒地堑基底花岗岩的锆石U-Pb年代学及其构造意义  

Zircon U-Pb Age from Basement Granites in Yishu Graben and Its Tectonic Implications

作　　者：许文良[1] 裴福萍[1] 高福红[1] 杨德彬[1] 卜永吉[2] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]中国石油吉林油田分公司,吉林松源138000

出　　处：《地球科学（中国地质大学学报）》2008年第2期145-150,共6页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(No40672033);国家油气专项(NoXQ-2004-07)

摘　　要：为了探讨伊舒地堑与松辽盆地基底的构造演化历史,对位于伊舒地堑中的2个基底花岗岩进行了锆石LA-ICP-MSU-Pb定年研究,并与松辽盆地基底花岗岩进行了对比.研究结果表明,伊舒地堑基底花岗岩中的锆石呈自形或半自形,并具有典型的岩浆生长环带,个别发育有核边结构,锆石的Th/U比值介于0.32～2.76,暗示其岩浆成因.CH11井花岗岩中锆石18个测点206Pb/238U加权平均年龄为162±2Ma,X13井花岗岩中锆石13个测点206Pb/238U加权平均年龄为159±3Ma,其核部存在176±1Ma的谐和年龄.上述结果表明,伊舒地堑中基底花岗岩形成于中侏罗世晚期或晚侏罗世早期,它们与松辽盆地基底中最晚期花岗岩的形成时间相同.这暗示伊舒地堑与松辽盆地自燕山期以来具有类似的基底演化历史.176±1Ma继承锆石的存在也证明了上述认识.LA-ICP-MS zircon U-Pb dating was carried out for two basement granites from the Yishu graben to compare the tectonic evolutionary history between the Yishu graben and Songliao basin. The results indicate that most of zircons from the basement granites are euhedral to subhedral in shape and show the typical oscillatory zoning with magmatic origin, some of which display the core-rim structure. Their Th/U ratios range from 0.32 to 2.76, implying that they should be from crystallization of magma. The dating results indicate that a weighted mean ^206 pb/^238 U age is 162±2 Ma for the basement granite from CHll well （sample No. CHll）, and that weighted mean ^206Pb/^238U ages are 159±3 Ma and 176± 1 Ma for rims and cores of zircons from the granite in X13 well （sample No. X13）, respectively. It is suggested that the basement granites were formed in late stage of the Middle Jurassic or the beginning of the Late Jurassic, which is consistent with ones of the latest basement granites from the Songliao basin. Therefore, it is proposed that the Yishu graben displays similar evolutionary history with the Songliao basin since the Yanshannian movement, which is also proved by the occurrence of the inherited zircons with age of 176±1 Ma.

关 键 词：伊舒地堑 基底 花岗岩 锆石 LA—ICP—MS U—Pb定年 松辽盆地 

分 类 号：P597[天文地球—地球化学]