北秦岭造山带武关岩群年代学研究及其地质意义

Geochronology of the Wuguan Complex in the North Qinling orogen and its geological significance

武关岩体位于北秦岭武关镇,侵入于丹凤岩群之中,为原泥盆系刘岭群北侧解体出来的变质沉积-火山岩系岩体。锆石阴极发光(CL)及LA-ICP-MS同位素测年分析显示,武关岩体中斜长角闪岩锆石U-Pb年龄为(349±10) Ma,该年龄代表岩体的岩浆结晶年龄,即形成年龄。石榴子石黑云斜长片岩中碎屑锆石峰值年龄为850 Ma,最小年龄为324 Ma,反映武关岩群沉积岩的沉积时代应该晚于早古生代。

The Wuguan rock mass located in Wuguan Town of North Qinling Mountains intruded into the Danfeng Complex,which is a metamorphic sedimentary-volcanic rock series disintegrated from the northern side of the original Devonian Liuling Group. Zircon cathodoluminescence( CL) imaging and LA-ICP-MS isotopic dating show that the zircon U-Pb age of amphibolite from the Wuguan rock mass is( 349 ± 10) Ma,which represents the age of magmatic crystallization of the intrusion,namely,the formation age. The peak age of clastic zircon in garnet biotite plagioclase schist is 850 Ma and the minimum age is 324 Ma,which indicates that the sedimentary age of the Wuguan group sedimentary rocks should be later than that of the Early Paleozoic.