东秦岭镇平县南湾组碎屑锆石U-Pb年代学及地质意义

U-Pb Dating and Geological Significance of Detrital Zircons from the Nanwan Formation,Zhenping County,East Qinling Mountains

东秦岭位于秦岭造山带与大别造山带的结合部位,其构造演化对于了解华北陆块与扬子陆块的碰撞拼合起着至关重要的作用;而南湾组是了解东秦岭构造过程的一个重要窗口,目前却少有关于其区域物质组成差异的研究.对东秦岭镇平县望火楼一带南湾组碎屑锆石进行了LA-ICP-MS U-Pb年代学研究.结果表明,锆石年龄峰值主要集中于2757~2500 Ma、2500~2400 Ma、2150~1800 Ma、1800~1700 Ma、1520~1165 Ma、1100~1000 Ma、1000~880 Ma、840~630 Ma、550~471 Ma,原岩物质主要来源于华北陆块、北秦岭构造带和南秦岭构造带.对比镇平县南湾组、秦岭地区刘岭群、信阳地区南湾组及大别山造山带北侧佛子岭群的年龄峰值及物质组成,结果显示均存在一定的差异.因此,四者是否具有真正意义上的可对比性需要进一步研究.

The East Qinling Mountains,located at the junction of the Qinling Orogenic Belt and the Dabie Orogenic Belt,had undergone complex tectonic evolution,and plays an important role in understanding the collision of the North China Block and the Yangtze Block.The Nanwan Formation plays an important role in understanding the tectonic process of the East Qinling Mountains,however,few studies have been done to analyze the regional differences in material composition.In this paper,the LA-ICP-MS U-Pb geochronology analyses of the detrital zircons from the Nanwan Formation in the Wanghuolou,Zhenping County,East Qinling,show that the zircon age peaks are mainly concentrated in 2757-2500 Ma,2500-2400 Ma,2150-1800 Ma,1800-1700 Ma,1520-1165 Ma,1100-1000 Ma,1000-880 Ma,840-630 Ma and 550-471 Ma,respectively.The original rock material is mainly from the North China Block and the North Qinling Orogenic Belt and South Qinling Orogenic Belt.There are some differences among the age peaks and material composition of the Nanwan Formation in Zhenping County,the Liuling Group in the Qinling Mountains,the Nanwan Formation in the Xinyang area,and the Foziling Group in the North Dabie Orogenic Belt.Therefore,further studies should be carried out to evaluate whether the four can be compared.