西秦岭西段然果儿岗花岗闪长岩体锆石U-Pb定年及地质意义

摘要

对侵位于西秦岭造山带西段中下三叠统隆务河群中的然果儿岗花岗闪长岩进行年代学研究，探讨其形成环境。结果表明，花岗闪长岩中锆石Th/U比值较高，锆石内部发育振荡环带，具岩浆成因特点；花岗闪长岩的结晶年龄为（227±4）Ma (MSWD=2.0)，表明其形成时代为晚三叠世卡尼期。然果儿岗花岗闪长岩形成于后碰撞环境，或者至少是由同碰撞到后碰撞的转折阶段。%This paper studies the Ranguoergang granodiorite using zircon U-Pb geochronology methods in the Western Section of West Qinling,which emplaced in middle-upper Triassic of Longwuhe Group, discussions formation environ-ment of the rock body. The results show that the granodiorite’s zircons have higher Th/U ratios and the internal CL imag-es of have oscillatory zoning indicated that the zircons of the samples were igneous in origin.The LA-ICP-MS zircon U-Pb isotope concordia diagram age is(227±4) Ma (MSWD=2.0),indicated granodiorite rock body was formed in Late Tri-assic Carnian.The Ranguoergang granodiorite emplacement post-collision setting,or at least is from syn-collision to post-collision transition phase.