南西天山晚新生代沉积序列磁组构特征及其构造意义  

Anisotropy of magnetic fabrics of the Late Cenozoic sedimentary succession in the southern West Tianshan Mountain and their tectonic implications

作　　者：陈新伟 陈汉林[2,3] 林秀斌[2,3] 程晓敢[2,3] 聂梅[1] CHEN Xinwei;CHEN Hanlin;LIN Xiubin;CHENG Xiaogan;NIE Mei(Key Laboratory of Tectonic Controls on Mineralisation and Hydrocarbon Accumulation of Ministry of Land and Resource,School of Earth Sciences,Chengdu University of Technology,Chengdu,610059;School of Earth Sciences,Zhejiang University,Hangzhou,310027;Research Center for Structures in Oil-and Gas-Bearing Basins,Ministry of Educution,Hangzhou,310027)

机构地区：[1]构造成矿成藏国土资源部重点实验室,地球科学学院,成都理工大学,成都610059 [2]地球科学学院,浙江大学,杭州310027 [3]含油气盆地构造研究中心,教育部,杭州310027

出　　处：《地质学报》2020年第6期1675-1688,共14页Acta Geologica Sinica

基　　金：国家自然科学基金(编号:41702205和41720104003);国家科技重大专项(编号:2017ZX05008-001,2016ZX05003-001和2016ZX05007-002)资助的成果。

摘　　要：喀什凹陷西部位于塔里木盆地、帕米尔构造带和南西天山构造带的交接处,在新生代以来接受了大量来自于南天山和帕米尔的沉积物,并记录了新生代以来南西天山构造抬升的信息。本文选择了位于南西天山山前的铁热克萨孜晚新生代剖面开展磁组构研究。铁热克萨孜剖面晚新生代沉积序列自下而上为一套整体上粒度逐渐变粗的陆相沉积,由河流湖泊相逐渐变为扇三角洲相,并最终变为冲积扇相和洪积扇相。岩石磁学结果的分析表明剖面晚新生代沉积序列中的主要磁性矿物为赤铁矿,仅在帕卡布拉克组下部为以磁铁矿为主。磁组构结果表明该剖面的磁组构为早期的同沉积弱变形磁组构,指示了当时构造应力的方向和变化。在22.1Ma以来南西天山山前晚新生代磁组构所反映的构造应力整体上为N-S向挤压,这与帕米尔和南天山的南北向持续汇聚作用相一致。在安居安组和西域组时期,应力方向由N-S向挤压变为NNE-SSW向挤压,这一变化可能是由塔拉斯-费尔干纳断裂的活动所导致的。塔拉斯-费尔干纳断裂(Talas-Fergana Fault,TFF)的右行走滑活动可能吸收了南西天山晚新生代的部分应变量,使得南西天山山前的构造应变量相对TFF以东的南天山山前地区要更小,使得TFF以东的晚新生代山前冲断带活动相对TFF以西地区更为发育和活跃。The western part of Kashi Depression lies in the conjunction area of the Tarim Basin,the Pamir Syntax,and the south West Tian Shan.The thick sediments accumulated in this depression were derived from and preserve a record of late Cenozoic tectonic uplift of the south West Tian Shan.This paper presents results of anisotropy of magnetic susceptibility(AMS)analysis of the late Cenozoic Tierekesazi section in the foreland of the south West Tian Shan.The late Cenozoic successions of the Tierekesazi section are continental sediments with a general upward increase in particle size and show a progressive change from fluvial-lacustrine facies to fan delta facies,alluvial fan facies and diluvial fan facies.Rock magnetic results of the late Cenozoic successions indicate that the magnetic minerals are mainly hematite,except for the lower Pakabulake Formation,which is dominated by magnetite.Results of the late Cenozoic AMS suggest a syn-sedimentary fabric with weak-deformation.Since 22.1 Ma directions of tectonic strain in the foreland of the south West Tian Shan are mainly N-S directed compressional stress,which is consistent with the continuous convergence of the Pamir and the south West Tian Shan in the late Cenozoic.At the time of deposition of the Anjuan Formation and the Xiyu Formation,directions of compressional strain changed from N-S directed to NNE-SSW directed,likely reflecting the activities of the Talas-Fergana fault.Right slip of the Talas-Fergana fault(TFF)might absorb part of the deformation amount of the south West Tian Shan in the late Cenozoic,leading to smaller deformation in the foreland of the southern West Tian Shan than in the foreland area of the South Tian Shan in the east of the TFF.As a result,late Cenozoic foreland thrustings in the area east of the TFF were more active and better developed than in the foreland area west of the TFF.

关 键 词：南西天山 喀什凹陷 塔拉斯-费尔干纳断裂 晚新生代 磁组构 

分 类 号：P618.13[天文地球—矿床学]