辽南三家子地区南辽河群里尔峪组变沉积岩中碎屑锆石U-Pb年代学研究  

Detrital zircon U-Pb geochronology of metasedimentary rocks from the Li 'eryu Formation of the South Liaohe Group in Sanjiazi area,the South Liaoning Province

作　　者：王舫[1] 刘建辉[1] 刘超辉[1] WANG Fang LIU JianHui Liu ChaoHui(Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China)

机构地区：[1]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2017年第9期2785-2791,共7页Acta Petrologica Sinica

基　　金：国家自然科学基金重点项目(41430210);中国地质调查局项目(DD20160121);中国地质科学院基本科研业务费项目(YYWF201703;J1614)联合资助

摘　　要：南辽河群里尔峪组主要分布在华北克拉通胶-辽-吉活动带的大石桥-岫岩-凤城-宽甸一带,主要岩性为各类长英质粒状岩石(浅粒岩-变粒岩组合)。通过前人长期深入研究,在区域构造、地球化学、同位素年代学研究、变质作用以及构造演化等方面积累了大量资料,取得了一系列重要进展。但是,有关其变质作用特征、沉积时代、源区特征以及辽河群乃至整个胶-辽-吉活动带的大地构造属性和形成的构造演化过程长期以来存在着裂谷开启-闭合模式、弧-陆碰撞模式和陆-陆碰撞模式的争论。本文在辽南地区1∶5万变质岩区专题填图的基础上,选择三家子地区南辽河群里尔峪组的疙瘩状长英质粒状岩石、黑云斜长片麻岩和含黑云母长英质粒状岩石为重点研究对象。通过锆石阴极发光图像特征和锆石LA-ICP-MS U-Pb年代学测试,综合限定研究区南辽河群里尔峪组变质沉积岩的物质来源和原岩形成时代,进而探讨其形成的构造背景。3件样品中锆石阴极发光图像显示核-边结构,核部具振荡环带,Th/U比值较高(Th/U=0.12~4.95),表明其岩浆来源;U-Pb年代学测试分别得到2140Ma、2170Ma和2150Ma的年龄峰值。综合前期研究成果,锆石U-Pb年代学测试结果在年龄直方图中显示明显的2137Ma的峰值。该组年龄与区域上大量出露的辽吉花岗岩的年龄具有一致性,表明南辽河群里尔峪组的物质来源于辽吉花岗岩,其沉积时限应晚于古元古代。The Li＇ eryu Formation of the South Liaohe Group is widely distributed within Dashiqiao-Xiuyan-Fengcheng-Kuandian, the Jiao-Liao-Ji mobile belt in the North China Craton. It mainly consists of quartzo-feldspathic rocks （leptite-leptynite unit）. After a long-term study in depth, extensive structural, geochemical, isotopic geochronological, metamorphic and tectonic investigations have been carried out and produced abundant of new data and interpretations. However, their metamorphic types, depositional time, protolith characteristics and tectonic evolution are still matter of hot debates. The debates focus on three major tectonic models for the evolution of the Liaohe assemblage, which include continent-arc collision, continent-continent （terranes） collision and rifting models. The pimple-shaped quartzo-feldspathic, Bt-P1 paragneiss and Bt-bearing quartzo-feldspathic rocks in Sanjiazi area were selected to be the objects of this paper, based on the new data of 1 ： 50,000 regional geological mapping. Cathodoluminescence （CL） imaging and LA-ICP-MS U-Pb zircon data are linked to unravel the origin, depositional time and tectonic setting of meta-sedimentary rocks of the Li＇eryu Formation, the South Liaohe Group. Zircon grains separated from three samples show core-rim structure. The zircon cores show oscillatory zoning and have high Th/U ratios （Th/U = 0. 12 ~ 4. 95）, indicating the magmatic crystallization age. U-Pb analysis spots yielded age peaks at 2140Ma, 2170Ma and 2150Ma, respectively. The population of detrital zircons from both previous research and this study display age peak at 2137Ma. This age population is completely consistent with the age range of the Liaoji granitoids, suggesting the major sediments of the Li＇ eryu Formation and the depositional time after Paleoproterozoic.

关 键 词：锆石U-Pb年龄 变沉积岩 里尔峪组 南辽河群 胶-辽-吉构造带 

分 类 号：P588.3[天文地球—岩石学]