秦岭造山带中部存在太古宙岩块——陕西商南县湘河地区楼房沟斜长角闪岩-浅粒岩锆石SHRIM PU-Pb年龄及其意义  

An Archean block in the Central Qinling orogenic belt:zircon SHRIMP U-Pb ages of the Loufanggou amphibolite-leucogranulitite (leptite) in the Xianghe area,Shangnan,Shaanxi,and their implications

作　　者：张宗清[1] 刘敦一[1] 宋彪[1] 张寿广[1] 张维吉[2] 杨永成 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]长安大学地球科学与国土资源学院,陕西西安71005 [3]陕西省区调研究院,陕西咸阳712000

出　　处：《中国地质》2005年第4期579-587,共9页Geology in China

基　　金：国家自然科学基金项目(40072071)资助

摘　　要：秦岭造山带是中朝克拉通华北板块和扬子克拉通板块结合区域。其基底组成为广大地质学家所关注。笔者报道了秦岭造山带中部陕西省商南县湘河地区楼房沟古变质结晶岩片斜长角闪岩-浅粒岩和黑云二长石英片岩的SHRIMP锆石U-Pb年龄数据,讨论了其地质意义。斜长角闪岩-浅粒岩为同一岩浆连续分异变质火山岩,锆石Pb严重丢失,207Pb/206Pb年龄≥(2488±8)Ma。年龄值与已获得的Sm-Nd等时年龄值在误差范围内一致。黑云二长石英片岩为副变质岩,锆石U-Pb年龄(978±13)Ma。秦岭造山带中部老于太古宇岩片(块)的发现表明,秦岭造山带下部可能存在过太古宙结晶基底。The Qinling orogenic belt is the junction between the North China plate of the Sino-Korean craton and the Yangtze cratonic plate and its basement arouses attention of many geologists. This paper reports the zircon SHRIMP U-Pb age data for the Loufanggou metamorphic crystalline rock sheet amphibolite-leptite and biotite- bearing monzonitic quartz schist in the Xianghe area, Shangnan, Shaanxi, in the central part of the Qinling orogenic belt and discusses their geological significance. Arnphibolite-leptite is meta-volcanic rocks resulting from continuous differentiation of the same magma. Zircon Pb loss is serious and the ^207Pb/^206Pb age is ≥2488±8 Ma. This age is consistent with the available Sm-Nd isochron age with the error limits. Biotite-bearing monzonitic quartz schist is parametamorphite with a zircon U-Pb age of 978±13 Ma. The discovery of an Archean sheet （block） in the central part of the Qinling orogenic bek suggests that the Archean crystalline basement may have existed in the lower part of the Qinling orogenic bek.

关 键 词：同位素年代学 变质岩 秦岭造山带 

分 类 号：P588.125[天文地球—岩石学] P597.3[天文地球—地质学]