Rodinia超大陆裂谷裂陷高潮与裂-坳转换:来自塔里木西北缘阿克苏地区碎屑锆石的制约  

The climax of the taphrogenesis stage and the taphrogenesis-depression transition of the Rodinia supercontinent rift:evidence from detrital zircons in the Aksu area,northwestern Tarim basin

作　　者：刘博 张文高[1] 陈正乐[1] 袁峰[2] 韩凤彬[1] 霍海龙 李季霖 LIU Bo;ZHANG Wengao;CHEN Zhengle;YUAN Feng;HAN Fengbin;HUO Hailong;LI Jilin(Key Laboratory of Paleomagnetism and Tectonic Reconstruction of Ministry of Natural Resources,Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;School of Resources and Environmental Engineering,Hefei University of Technology,Anhui,Hefei 230009,China)

机构地区：[1]中国地质科学院地质力学研究所自然资源部古地磁与古构造重建重点实验室,北京100081 [2]合肥工业大学资源与环境工程学院,安徽合肥230009

出　　处：《地质学报》2021年第8期2361-2379,共19页Acta Geologica Sinica

基　　金：国家科技支撑计划项目(编号2018YFC0604005、2015BAB05B04);中国地质调查局基本科研业务费(编号JYYWF20183702、JYYWF20180602、DZLXJK201904);国家自然科学基金项目(编号41902214)联合资助的成果。

摘　　要：阿克苏地区位于塔里木地块西北缘,是研究Rodinia超大陆裂谷裂解过程的关键地区。在阿克苏地区裂谷序列中,发育有不整合面。通过对阿克苏地区巧恩布拉克组、尤尔美那克组和苏盖特布拉克组碎屑锆石的LA-ICP-MS U-Pb年龄测定,对Rodinia超大陆裂谷期不整合面的形成时间、不整合面上下地层的物源变化以及不整合面的构造意义进行了讨论。碎屑锆石测年结果显示:尤尔美那克组于708 Ma后开始沉积,苏盖特布拉克组于577 Ma后开始沉积,被剥蚀的阿克苏群为尤尔美那克组和苏盖特布拉克组提供了局部物源。结合前人资料分析表明:(1)巧恩布拉克组与尤尔美那克组之间角度不整合面形成于717~708 Ma之间,苏盖特布拉克组与下伏地层间不整合面形成于580~577 Ma之间;(2)阿克苏地区724~717 Ma之间发生了一次幕式裂陷作用,这次幕式裂陷作用可能代表了Rodinia超大陆裂谷裂陷期的高潮;(3)苏盖特布拉克组与下伏地层间不整合面是Rodinia超大陆裂谷裂-坳转换界面,这个界面时限为580~577 Ma;(4)"雪球地球"事件显著地促进了不整合面形成时的剥蚀作用,巧恩布拉克组与尤尔美那克组之间的角度不整合面、苏盖特布拉克组与下伏地层之间的不整合面的形成分别受到了Sturtian冰期、Gaskiers冰期的影响。在本文中,不仅阿克苏地区裂谷期不整合面的成因机制得到了探讨,也一并完善了阿克苏地区裂谷的演化模式。The Aksu area is located in the northwestern margin of the Tarim Block,and is a key area to study the breakup process of the Rodinia supercontinent rift.Unconformities are found in the rift sequence of the Aksu area.Based on LA-ICP-MS U-Pb dating of detrital zircons from the Qiaoenbrak Formation,the Yuermeinak Formation,and the Sugetbrak Formation in the Aksu area,the formation time of the unconformities,the provenance of strata both below and above the unconformities and the tectonic significance of the unconformities are discussed.Detrital zircon dating results show that depositional periods of the Yuermeinak and the Sugetbrak formations began after 708 Ma and 577 Ma respectively,and that the Aksu Group was the possible source for both these formations.Combined with previous studies,our analysis shows that:(1)The angular unconformity between the Qiaoenbrak Formation and the Yuermeinak Formation was formed between 717 Ma and 708 Ma,and the unconformity between the Sugetbrak Formation and the underlying strata was formed between 580 Ma and 577 Ma.(2)An episodic taphrogenesis occurred between 724 Ma and 717 Ma in the Aksu area,which may represent the climax of the taphrogenesis stage of the Rodinia supercontinent rift.(3)The unconformity between the Sugetbrak Formation and the underlying strata was the taphrogenesis-depression transition interface of the Rodinia supercontinent rift,and the interface was formed between 580 Ma and 577 Ma.(4)The"snowball Earth"event significantly promoted the formation of the unconformities.The formation of the angular unconformity between the Qiaoenbrak and the Yuermeinak formations,and the formation of the unconformity between the Sugetbrak Formation and the underlying strata were affected by the Sturtian glaciation and the Gaskiers glaciation,respectively.Not only the formation mechanism of the unconformities during rifting in the Aksu area is discussed,but also the rift evolution model in the Aksu area is proposed.

关 键 词：碎屑锆石 不整合 裂陷高潮 裂-坳转换 RODINIA 塔里木 阿克苏 

分 类 号：P597.3[天文地球—地球化学] P548[天文地球—地质学]