北秦岭宽坪岩群变质沉积岩年代学及地质意义  

Chronology of metasedimentary rocks from Kuanping Group Complex in North Qinling Belt and its geological significance

作　　者：李承东[1] 赵利刚[1] 许雅雯[1] 常青松[1] 王世炎[2] 许腾 LI Chengdong;ZHAO Ligang;XU Yawen;CHANG Qingsong;WANG Shiyan;XU Teng(Tianjin Institute of Geology and Mineral Resources,Tianjin 300170,China;Henan Institute of Geological Survey,Zhengzhou 450001,Henan,China)

机构地区：[1]天津地质矿产研究所,天津300170 [2]河南省地质调查院,河南郑州450001

出　　处：《中国地质》2018年第5期992-1010,共19页Geology in China

基　　金：中国地质调查局"中条-熊耳山成矿区地质矿产调查"项目(DD20160043);"豫西关键地区地质调查"项目(12120113060900);国家自然科学基金(41272065)联合资助~~

摘　　要：宽坪岩群位于北秦岭造山带,主要由广东坪岩组斜长角闪岩、四岔口岩组云母石英片岩及谢湾岩组的大理岩组成。通过LA-MC-ICPMS锆石U-Pb测年研究,宽坪岩群谢湾岩组碎屑锆石年龄为400～3502 Ma,其中最年轻一组的^(206)Pb/^(238)U年龄在380～418 Ma,结合黑云母^(40)Ar/^(39)Ar (370.9±2.0)Ma的变质年龄,表明谢湾岩组形成在晚泥盆世。四岔口岩组碎屑锆石年龄介于512～3598 Ma,最年轻的一组锆石^(206)Pb/^(238)U年龄在512～549 Ma,其黑云母^(40)Ar/^(39)Ar变质年龄为(370.4±1.8)Ma,表明该组形成于512 Ma(早寒武世)之后,晚泥盆世之前,主体很可能形成于早古生代。宽坪岩群是由不同时代的地层和岩片构成,应该进一步解体。宽坪岩群物源来自华北陆块、秦岭造山带和扬子陆块。其变形变质时代为晚泥盆世,代表了北秦岭造山带碰撞造山的结束时代。Kuanping Group Complex is located in North Qinling orogenic belt and consists chiefly of amphibolite of Guangdongping Formation,mica-quartzose schist of Sichakou Formation and marble of Xiewan Formation.According to recent dating of the LA-MC-ICPMS U-Pb zircons from Kuanping Group Complex in Tanghe area of Henan,their ages of detrital zircons of mica-quartzose schist from Xiewan Formation Complex range from 400Ma to 3502 Ma with a group of youngest 206Pb/238U ages between 380 and 418 Ma.Combined with(370.9±2.0)Ma metamorphic age of 40Ar/39Ar of the biotite,it is concluded that Xiewan Formation Complex was formed in the Late Devonian.And the ages of detrital zircons from Sichakou Formation Complex range similarly from 512 Ma to 3598 Ma with a group of youngest 206Pb/238U ages between 512 and 549Ma,and its metamorphic age is(370.4±1.8)Ma from biotite 40Ar/39Ar.It is thus held that Sichakou Formation Complex was formed between Middle Cambrian and Late Devonian of early Paleozoic.So Kuanping Group Complex needs further disintegration due to great difference of stratigraphic ages.The sediments were probably derived from the North China Block,the Qinling orogenic belt and the Yangtze block.The ages of biotite 40Ar/39Ar show that Kuanping Group Complex was deformed in Late Devonian,indicating the end of collision orogeny of the North Qinling Belt during Paleozoic.

关 键 词：宽坪岩群 LA-MC-ICPMS 40AR/39AR 北秦岭 河南省 

分 类 号：P588.3[天文地球—岩石学] P597[天文地球—地质学]