大兴安岭中段上二叠统林西组核形石的发现及其地质意义  

Discovery of oncolitic in the Upper Permian Linxi Formation in central Great Xing’an Mountains and its geological significances

作　　者：梁天意 刘敬党[1,2] 李猛猛 王刚[2] 朱玺 张海龙 LIANG Tianyi;LIU Jingdang;LI Mengmeng;WANG Gang;ZHU Xi;ZHANG Hailong(Mining Institute,Liaoning Technical University,Fuxin,Liaoning,123000;Chemical Geological Prospecting Institute of Liaoning Province Co.LTD,Jinzhou,Liaoning,121000;Liaoning Provincal Institute of Geological Exploration Co.LTD,Dalian,Liaoning,116100)

机构地区：[1]辽宁工程技术大学矿业学院,辽宁阜新123000 [2]辽宁省化工地质勘查院有限责任公司,辽宁锦州121000 [3]辽宁省地质勘查院有限责任公司,辽宁大连116000

出　　处：《地质论评》2021年第3期593-611,共19页Geological Review

基　　金：中国地质调查局《内蒙古1∶5万钓鱼台等四幅区域地质调查》项目(编号:DD20160201-07)的成果。

摘　　要：林西组是大兴安岭地区晚二叠世重要的沉积地层,其研究程度也直接影响古亚洲洋闭合、两大板块拼接、沉积环境转变等重大地质问题。本次研究区主要位于大兴安岭中段,根据实际调查,首次在扎赉特旗巴彦乌兰地区晚二叠系林西组发现了海相的核形石灰岩。根据岩石学、地球化学和古生物学等研究手段,并根据元素比值等确定该核形石灰岩产生于碳酸盐台地边缘温暖、动荡的浅滩环境,具有明显的海相特征,并在林西组中—下部发现了具有明显陆相沉积特征的双壳类Palaeanodonta sp.—Palaeomutela sp.组合。说明该地区在晚二叠世早期存在海相或海陆交互相的沉积环境,随着环境的改变,林西组逐渐向陆地河湖相沉积环境转变。这一发现不仅完善了兴蒙地区林西组地层的结构,也为以后研究兴蒙海槽在晚古生代—中生代的过渡时期的沉积演化提供可靠资料。Objectives:The Linxi Formation is a improtent sedimentary strata of the Permaian in Great Hinggan Mountains,and the degree of study is also directly affect the reaserch about close of the paleo-Asian ocean,the joint of two plates,transformation of depositional environment and other major geological problems.The research area is mainly located in the central part of Great Hinggan Mountains,based on field investigation,the marine oncolitic limestone of the Upper Permian Linxi Formation has been found for the first time in Bayanwulan area,Zhalaite Banner,Inner Mongolia.Methods:Base on the study methods of petrology,geochemistry,paleontology,and also element geochemistry.Results:It confirms that the oncolitic limestone grow out of the warm and turbulent shoal environment of edge of carbonate platform,which has obvious marine facies characteristics,and found the combination of palaeanodonta sp.—palaeomutela sp.fossils,which have obvious characteristics of continental deposition in lower—middle part of the Linxi Formation.This shows that this area existed the sedimentary environment of marine facies or paralic facies in early Late Permian,with the environment changed,the Linxi Formation turned to the sedimentary environment of river and lucustrine facies gradually.Conclusions:This discovery not only improved the structure of the Linxi Formation in the Xingmeng area(Great Hinggan—Inner Mongolia area),but also provides reliable datas of the research on the sedimentary evolution of the Xingmeng Trough during the transitional period from late Paleozoic to Mesozoic.

关 键 词：上二叠统林西组 核形石灰岩 环境演化 兴蒙海槽 大兴安岭 

分 类 号：P534.46[天文地球—古生物学与地层学] Q911.1[天文地球—地质学]