摘要
内蒙古北山造山带自北向南发育红石山-百合山、月牙山-洗肠井和帐房山-玉石山3条蛇绿构造混杂岩带。其中北部的2条蛇绿岩带揭示了北山造山带两阶段演化的历史:月牙山-洗肠井蛇绿混杂岩带洋壳形成于530~520 Ma,沿该带多处保存较完好的蛇绿岩洋壳残块(洋壳结构具向北变新特征),与北侧的早古生代公婆泉岩浆弧(由南向北岛弧成熟度变高)共同指示了北山洋向北俯冲消减的过程,即490 Ma初始俯冲,450~440 Ma为俯冲峰期,430~420 Ma为同碰撞阶段,400 Ma的双峰式岩浆岩组合指示了北山洋的消亡和后造山伸展的过程;红石山-百合山蛇绿混杂岩带是发育在雀儿山-圆包山岛弧基础上的SSZ型蛇绿岩,弧后开裂洋壳的形成与南侧最早发育的岛弧岩浆作用年龄接近(340~320 Ma),310~290 Ma俯冲峰期造成南侧白山岩浆弧大量的岩浆活动,早二叠世末期(275 Ma)的辉长岩和花岗岩侵位及早—中二叠世双堡塘组下部的角度不整合均反映了红石山洋盆的闭合。前人所划“石板井-小黄山蛇绿岩带”实为一条早古生代发育的深大断裂,沿带发育中基性侵入体及少量超基性岩,后期(志留纪末)叠加有较强的韧性剪切变形。中生代以来的走滑作用和逆冲推覆构造改造了古生代的构造格架,使红石山-百合山蛇绿混杂岩带向北左行切错了十余千米,北山南部的中—新元古界推覆至下古生界之上。对内蒙古北山造山带时空结构的厘定,有助于中亚造山带造山作用过程的理解及其对古生代地壳增生的深入研究,也对银额盆地晚古生代新层系油气资源勘查起到基础支撑。
The Beishan orogenic belt is composed of Late Paleozoic Hongshishan-Baiheshan ophiolite mélange belt,Early Paleozoic Yueyashan-Xichangjing ophiolite mélange belt and late Paleozoic Zhangfangshan-Yushishan ophiolite mélange belt from north to south in Inner Mongolia.The“Shibanjing-Xiaohuangshan ophiolite belt”defined by previous researchers is actually an Early Paleozoic trans-crustal fault zone,across which there are intermediate-mafic rocks and minor ultramafic rocks.At the end of the Silurian,intense ductile shear deformation was superimposed upon it.The two ophiolite belts in the north reveal the two-stage evolution history of Beishan orogenic belt:The Yueyashan-Xichangjing ophiolite mélanges belt was formed from 530 Ma to 520 Ma,and there exist many intact ophiolite oceanic crust fragments along the belt(the oceanic crust structure has the characteristics of becoming younger from south to north),which,together with the Early Paleozoic Gonpoquan magmatic arc(the maturity of island arc increased from south to north),indicates the process of northward subduction of the Beishan Ocean,which included the initial subduction of 490 Ma,the peak period of subduction ranging from 450 Ma to 440 Ma,and the syn-collision stage ranging from 430 Ma to 420 Ma.The 400 Ma bimodal magmatic rock assemblage indicates the extinction of Beishan Ocean and the beginning of a new tectonic cycle.The Hongshishan-Baiheshanophiolite mélange belt is a SSZ-type ophiolite developed on the basis of the Quershan-Yuanbaoshan island arc.The formation time of the back arc cracked oceanic crust approached the earliest developed island arc magmatism in the south,which happened from 340 Ma to 320 Ma.The period of 310~290 Ma subduction caused a lot of magmatic activities that formed the Baishan magmatic arc.The existence of gabbro and granite bimodal intrusions at the end of Early Permian(275 Ma)and the Early-Middle Permian angular unconformity events of the Shuangbaotang Formation commonly reflect the closure of the Hongshishan Ocean basin.The strike-slip and thrust nappe structures since Mesozoic have transformed the Paleozoic tectonic framework,resulting in the northward left-lateral slipping of Hongshishan-Baiheshanophiolite mélange belt for more than 10 kilometers and the thrusting of Middle-Upper Proterozoic strata on the Early Paleozoic strata.The authors determined the spatial and temporal structure of the Beishan orogenic belt,which is helpful to the further research on the orogenesis and crustal accretion process of the Central Asian Orogenic Belt,and also provides research basis for the exploration of the Late Paleozoic hydrocarbon resources in the Yin’e basin.
作者
辛后田
牛文超
田健
滕学建
段霄龙
XIN Houtian;NIU Wenchao;TIAN Jian;TENG Xuejian;DUAN Xiaolong(Tianjin Center,China Geological Survey,Tianjin 300170,China;North China Center for Geoscience Innovation,Tianjin 300170,China)
出处
《地质通报》
CAS
CSCD
北大核心
2020年第9期1297-1316,共20页
Geological Bulletin of China
基金
中国地质调查局项目《阴山成矿带小狐狸山和雅布赖地区地质矿产调查项目》(编号:DD20160039)。
关键词
北山造山带
构造单元划分
蛇绿构造混杂岩
洗肠井
百合山
中亚造山带
古亚洲洋
Beishan orogenic belt
division of tectonic units
ophiolite mélange
Xichangjing
Baiheshan
Central Asian Orogenic Belt
Paleo-Asian Ocean
