贺兰山北段牛头沟金矿区围岩的原岩恢复、时代及其地质意义  

Original rocks,ages,and its significance for the wall rock of Niutougou gold deposit in northern Helan Mountains

作　　者：宋新华[1,2] 李红宇 郭合伟 张连昌[4] 孙文坤 谷守江 陈志广[4] 张晓静[4] 

机构地区：[1]中国地质大学,北京100083 [2]宁夏地质矿产勘查开发局,银川750021 [3]宁夏有色金属地质勘查院,银川750200 [4]中国科学院地质与地球物理研究所,北京100029

出　　处：《岩石学报》2010年第5期1625-1632,共8页Acta Petrologica Sinica

基　　金：国家973规划项目(2006CB403506);中央财政补助项目(691号)联合资助

摘　　要：牛头沟金矿区位于华北陆块鄂尔多斯地块西缘贺兰山北段之基底杂岩带,赋矿地层为一套古元古界宗别立群第二亚群(Pt1Z2)中-深程度变质岩系,主要岩石类型是黑云斜长片麻岩和变粒岩。岩石地球化学特征分析及原岩恢复说明,蚀变岩型金矿体的围岩由正、副变质岩类共同组成,其中变粒岩的原岩为沉积碎屑岩,黑云斜长片麻岩的原岩为花岗闪长质侵入岩。离子探针锆石U-Pb定年表明,表壳岩的形成时代小于2120Ma,花岗闪长岩锆石U-Pb年龄为1950±8.9Ma,辉绿岩脉的侵入与花岗闪长岩属同期。综合研究表明,矿区变质岩的原岩形成时代不是前人认为的晚太古代,而是古元古代。同时应将属于正变质岩类黑云斜长片麻岩(原岩为花岗闪长岩)从宗别立群(Pt1Z)地层中分离出来,作为侵入岩单元考虑。The Niutougou gold deposit is located in the western margin of Ordos block and the northern Helan Mountains. The ore-bearing wall-rocks are a set of medium-deep level metamorphic rocks of the second subgroup of Zongbili Group ( Pt1Z2 ) in Paleo-Proterozoic. Main types of the metamorphic rocks include granulite and biotite-plagioclase-gneiss. Petrochemical study shows that the original rock of the granulite is clastic rock and the original rock of the biotite-plagioclase-gneiss is granodiorite. SIMS zircon U-Pb dating shows that the age of the metasedimentary rock is < 2120Ma,biotite-plagioclase-gneiss and diabase are of 1950 ± 8. 9Ma. Authors suggest that the granodiorite should be taken as an intrusive unit apart from metasedimentary system.

关 键 词：锆石U-PB定年 原岩恢复 牛头沟金矿区 古元古代 宁夏贺兰山 

分 类 号：P597.3[天文地球—地球化学]