胶莱盆地蛇窝泊地区白垩纪林寺山组沉积时代与物源特征:来自碎屑锆石U-Pb测年与稀土元素组成的新证据  

Depositional Timing and Provenance Characteristics of the Cretaceous insishan Formation in the Shewopo Area, Jiaolai Basin: New Evidence from Detrital Zircon U-Pb Dating and REE Composition

作　　者：张连祥 刘平华[2] 王义龙 周万蓬[3] 张宇佳 张传恒[1] Zhang Lianxiang;Liu Pinghua;Wang Yilong;Zhou Wanpeng;Zhang Yujia;Zhang Chuanheng(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院地质研究所,北京100037 [3]东华理工大学地球科学学院,江西南昌330013

出　　处：《地球科学》2021年第3期1119-1132,共14页Earth Science

基　　金：国家自然科学基金项目(Nos.41972205,41672191);中国地质调查局二级项目(Nos.DD20190003,DD20190037)。

摘　　要：林寺山组是胶莱盆地莱阳群底部重要的地层单元之一.准确限定其沉积时代与物源性质对于客观重建华北陆块东部晚中生代大地构造格局以及周缘造山带/前寒武纪变质基底晚中生代的折返过程具有重要的制约作用.以莱阳盆地蛇窝泊地区莱阳群林寺山组细砾岩为研究对象,对其开展了野外地质调查、岩相学观察、锆石U-Pb测年与锆石稀土元素分析等综合研究,并获得了如下初步认识.(1)林寺山组细砾岩中最小一组碎屑锆石加权平均年龄分别为129±1 Ma与127±5 Ma,结合区域上不整合于莱阳群之上青山群火山岩锆石谐和年龄为119±1 Ma,推测蛇窝泊地区林寺山组沉积时代介于127~119 Ma.(2)蛇窝泊地区林寺山组细砾岩的碎屑锆石年龄变化于2 858~126 Ma之间,并以新太古代晚期与白垩纪早期碎屑锆石为主.前古元古代的碎屑锆石主要来源于胶北前寒武纪变质岩,表明胶北太古宙-古元古代变质岩至少在白垩纪早期已折返至近地表.(3)160~120 Ma岩浆型碎屑锆石主要来源于胶东同时代的中酸性侵入体,暗示在白垩纪早期至少部分160~120 Ma中酸性侵入体已抬升至地表.(4)林寺山组发育少量的二叠纪(280 Ma)和印支期(213 Ma)变质锆石,表明胶东地区可能存在二叠纪约280 Ma区域变质-变形事件,同时暗示早白垩世苏鲁超高压变质岩已经折返到地表.Linsishan Formation is one of the important stratigraphic units at the bottom of the Early Cretaceous Laiyang Group in the Jiaolai basin. The accurate determination of depositional timing and provenance characteristics of the Linsishan Formation is of great importance for the objective reconstruction of the Late Mesozoic tectonic framework in the eastern part of the North China Block and the Late Mesozoic exhumation process of the surrounding orogenic belt/Precambrian basement. In this paper, we present an integrated study involving detailed field geological investigation, petrographic observation, zircon and U-Pb dating and in situ trace element analysis of the fine-grade conglomerates from the Linsishan Formation in the Laiyang Group, and the following conclusions are suggested:(1) The weighted mean age of the youngest group of detrital zircons in the fine-grade conglomerates of Linsishan Formation are 129±1 Ma and 127±5 Ma, combining with the zircon concordant age of 119±1 Ma yielded by magmatic zircons in the volcanic rocks from the Qingshan Group. It is speculated that the depositional timing of the Linsishan Formation in the Shewopo area is 127-119 Ma.(2) The detrital zircon ages of the fine-grade conglomerate of the Linsishan Formation in the Shewopo area range from 2 858 to 126 Ma, respectively, and are marked by the occurrence of the Late Neoarchean and Early Cretaceous ages. The pre-Paleoproterozoic detrital zircons are mainly derived from Precambrian metamorphic rocks of the Jiaobei terrane, indicating that the Archean-Paleoproterozoic metamorphic rocks of the Jiaobei terrane have exhumated to the near surface at least in the Early Cretaceous.(3) The 160-120 Ma magmatic detrital zircons are mainly derived from the synchronous intermediate acid intrusions in Jiaodong, suggesting that at least part of the 160-120 Ma intermediate acid intrusions have returned to the surface during the Early Cretaceous.(4) Permian(280 Ma) and Late-Triassic(213 Ma) metamorphic zircons which are identified in the Linsisha

关 键 词：胶莱盆地 林寺山组 沉积时代 锆石U-PB测年 岩石学 

分 类 号：P581[天文地球—岩石学]