本文将参加年度优秀论文评选,如果您觉得这篇文章很好,请投下您宝贵的一票,谢谢! 支持(80)   不支持(17)

狼山发现蛇绿混杂岩——华北克拉通与中亚造山带碰撞边界的关键证据
    点此下载全文
引用本文:吕洪波,冯雪东,王俊,朱晓青,董晓朋,张海春,章雨旭.2018.狼山发现蛇绿混杂岩——华北克拉通与中亚造山带碰撞边界的关键证据[J].地质论评,64(4):777-805,[DOI]:.
LU Hongbo,FENG Xuedong,WANG Jun,ZHU Xiaoqing,DONG Xiaopeng,ZHANG Haichun,ZHANG Yuxu.2018.Ophiolitic Mélanges Found in Mount Langshan as the Crucial Evidence of Collisional Margin between North China Craton and Central Asian Orogenic Belt[J].Geological Review,64(4):777-805.
DOI:
摘要点击次数: 2882
全文下载次数: 2054
作者单位E-mail
吕洪波 1) 中国石油大学地球科学与技术学院 山东青岛266580 luhongbogeo@163.com 
冯雪东 1) 中国石油大学地球科学与技术学院 山东青岛2665806) 内蒙古地震局乌加河地震台 内蒙古巴彦淖尔市乌拉特中旗015331  
王俊 2) 香港大学地球科学系 香港  
朱晓青 3) 青岛海洋地质研究所 山东青岛266071  
董晓朋 4) 中国地质科学院地质力学研究所 北京100081  
张海春 5) 中国科学院南京地质古生物研究所 南京210008  
章雨旭 7) 中国地质科学院 北京100037  
基金项目:本文为中陕核工业集团委托项目“测老庙地区区域地质研究与铀矿有利区带预测”和国家自然科学基金资助项目(编号: 41072074)的成果。
中文摘要:通过对内蒙古西部狼山地区进行野外调查,笔者等在狼山南缘的一系列构造逆冲片露头中发现了蛇绿混杂岩。根据野外观测、岩石薄片鉴定、岩石地球化学分析和锆石U Pb定年等综合研究,确定了蛇绿混杂岩的基质为绿泥石片岩,而混杂岩块包括:紫红色硅质岩、石英角斑岩、玄武岩、蚀变辉绿岩和变质辉长岩等。其中,绿泥石片岩、玄武岩、蚀变辉绿岩中年轻的岩浆锆石年龄将岩浆喷发时代锁定在早白垩世晚期到晚白垩世早期,而且该三种岩石都具有高铝(Al2O3>17%)玄武岩的特征,指示了本区白垩纪与俯冲带相关的构造环境。依据狼山白垩纪蛇绿混杂岩的发现笔者等尝试重新厘定华北克拉通与中亚造山带之间的碰撞时间和边界:作为华北克拉通西北重要组成部分的鄂尔多斯地块在晚白垩世向北俯冲并最终与中亚造山带碰撞拼合,从而造成了阴山造山带西段狼山的隆起。根据构造地貌相似性原理,华北克拉通北部边界可能要从白云鄂博至西拉木伦河一带向南移到阴山—燕山一带,而最后的碰撞时间则由晚古生代推迟到晚白垩世。华北克拉通与西伯利亚克拉通之间的中亚造山带的宽度也进一步向南加宽为整个蒙古南部与内蒙古高原区,构成新的中亚造山带。这一认识为华北克拉通和中亚造山带中新生代构造演化研究以及重要成矿带成因机制探讨提供了新的大地构造模型,也为促进华北克拉通中生代破坏理论的改进提供新的信息和思路。
中文关键词:内蒙古  狼山  蛇绿混杂岩  华北克拉通  中亚造山带  碰撞边界  晚白垩世
 
Ophiolitic Mélanges Found in Mount Langshan as the Crucial Evidence of Collisional Margin between North China Craton and Central Asian Orogenic Belt
NameInstitution
LU Hongbo1)School of Geosciences, China University of Petroleum, Qingdao, Shandong, 266580
FENG Xuedong1)School of Geosciences, China University of Petroleum, Qingdao, Shandong, 266580;6) Wujiahe Station, Earthquake Agency of Inner Mongolia Autonomous Region, Bayannur, Inner Mongolia, 015331
WANG Jun2) Department of Earth Sciences, University of Hong Kong, Hong Kong
ZHU Xiaoqing3) Qingdao Institute of Marine Geology, Qingdao, Shandong, 266071
DONG Xiaopeng4) Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, 100081
ZHANG Haichun5) Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing, 210008
ZHANG Yuxu7) Chinese Academy of Geological Sciences, Beijing, 100037
Abstract:Objective: Mount Langshan is the western section of Yinshan Mountain in the southern Inner Mongolia, north of China. Yinshan Mountain, being treated as a typical intra plate orogenic belt, has been regarded as the northern margin within the North China Craton by former geologists. However, our new discovery in Mount Langshan has attributed it to collisional orogeny. Our study indicates that Yinshan Mountain should be the Late Cretacous collision margin between North China Craton (NCC) and Central Asian Orogenic Belt (CAOB).Methods: We found the outcrop of ophiolitic mélanges in Mount Langshan, west of Inner Mongolia, in a geologic expedition in 2015. To confirm our discovery we conducted more field investigation in 2016 and collected ample rock samples for laboratory tests. We examined the textures and mineral compositions of major ophiolitic mélanges through microscopic petrology, analyzed the chemical compositions (major oxides and trace elements) of key rock types, dated the geological times of important igneous rocks through U Pb zircon ages.Results: Geological fieldwork reveals that there are a series of thrust sheets in the southern flank of Mount Langshan. All the thrust sheets incline northward, and the ophiolitic mélanges are enclosed within one thrust sheet. The high Aluminum basalts and related igneous rocks (Al2O3>17%) indicate that the major ophiolitic mélanges were originated in the subduction setting, representing the relics of the oceanic crust. The youngest ages of basalts and diabases imply their cooling time in the Late Cretaceous.Discussion and Conclusion: The authors of this article found the outcrops of ophiolitic mélanges in the southern piedmont of Mount Langshan, western part of Inner Mongolia. Our study reveals the following achievements: The ophiolitic mélanges are enclosed in a large thrust sheet of more than 500m in width and 3km in length. The thrust sheet extended in east—west direction and inclined northward, and there are many thrust sheets of other rock types connected to the south with the same inclination toward north. The ophiolitic mélanges are composed of two parts: matrix and tectonic blocks. The matrix is mainly chlorite schists and metamorphic basalts in dark gray to green colors. The tectonic rock blocks include red cherts, quartz keratophyres, meta diabases, basalt and metamorphic gabbros etc. Geochemical analysisand U Pb zircon dating show that chlorite schists, basalts, and meta diabases should have been originated from a high aluminum basaltic arc magma closely related to subduction setting during the Late Cretaceous. The ophiolitic mélangesare the remains of the fossil oceanic crust connected to the North China Craton trapped in the orogenic belt during the northward subduction of Ordos Block beneath the southern margin of Central Asian Orogenic Belt. Thus, the ophiolitic mélanges imply the latest collision between CAOB and NCC in the Late Cretaceous. Mount Langshan is the western section of Yinshan Mountain.According to the similarity principle of tectonic landforms that similar landforms are the results of similar tectonic events, we can infer that the whole scope of Yinshan Mountain and Yanshan Mountain should be the result of the same tectonic event——the latest collision between NCC and CAOB during the Late Cretaceous. We suggest that the northern margin of NCC should be removed from Bayan Obo—Xar Moron River to Yinshan—Yanshan Mountains. Because we have found the Cretaceous ophiolitic mélanges in Mount Langshan (the western section of Yinshan Mountain), Yinshan Mountain is no longer the “intra plate orogenic belt” but a collisional orogenic belt between the North China Craton and the southern margin of Central Asian Orogenic Belt in which its southern margin, Yinshan Mountain, was uplifted by the end of the Late Cretaceous. The discovery of ophiolitic mélanges can also provide new tectonic regime clues for the exploration of Cu—Pb—Zn sulfide minerals in the Mount Langshan and the other similar places alongYinshan Mountain, Yanshan Mountain and even the Great Khingan Ranges. Furthermore, our researchalso suggests that the tectonic process of North China Plate during the whole Mesozoic time might not be a process of “North China Craton breakup” but a series of collision events between many small terranes in northern Asia and Siberia.
keywords:〗Inner Mongolia, Mount Langshan, Ophiolitic mélanges, North China Craton, Central Asian Orogenic Belt, Collision margin, Yinshan—Yanshan Mountains, the Late Cretaceous
查看全文  查看/发表评论  下载PDF阅读器
WeChat
s