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LI Bing-shuai YAN Mao-du ZHANG Wei-lin YANG Yong-peng ZHANG Da-wen CHEN Yi GUAN Chong 《地震地质》2019,41(2):300-319
The giant sinistral Altyn Tagh Fault(ATF)is the northern boundary of the Tibetan Plateau. It has been playing important role in adjusting the India-Eurasia collision and the tectonic evolution of the northeastern Tibetan Plateau. Knowledge of the evolution of the ATF can provide comprehensive understanding of the processes and mechanisms of the deformation of the Tibetan Plateau. However, its timing of commencement, amount of displacement and strike-slip rate, as well as the tectonic evolution of the region are still under debate. South of the ATF, there exist a series of oroclinal-like arcuate structures. Knowledge of whether these curved geometries represent original curvatures or the bending of originally straight/aligned geological units has significant tectonic implications for the evolution of the ATF. The Yingxiongling arcuate belt in the western Qaidam Basin and the northern Qaidam marginal thrust belt(NQMTB)north of the Qaidam Basin are the two typical arcuate thrust belts, where the former has a "7-types" structure, and the latter has a reverse "S-type" structure. Successive Cenozoic sediments are well exposed and magnetostratigraphically dated in both belts.
Paleomagnetic declination has great advantage to reveal vertical-axis rotations of geological bodies since they become magnetized. Recently conducted paleomagnetic rotation studies in different parts of these two thrust belts revealed detailed Cenozoic rotation patterns and magnitudes of the region. By integrating these paleomagnetic rotation results with regional geometric features and lines of geological evidence, we propose that these two arcuate thrust belts were most likely caused by different rotations in different parts of these curvatures, due to the sinistral strike-slip faulting along the ATF, rather than originally curved ones. The Yingxiongling arcuate belt was shaped by the significant counterclockwise(CCW)rotations of its northwestern half(the Akatengnengshan anticline)near the ATF during~16~11Ma BP, while its southeastern half(the Youshashan anticline)had no significant rotations since at least~20Ma BP. The geometry of the NQMTB was developed firstly by remarkable clockwise rotations of its middle part during~33~14Ma BP, and later possibly CCW rotations of its northwestern part during the Middle to Late Miocene, similar to that of the northwestern part of the Yingxiongling arcuate belt. The characteristics of two-stage strike-slip evolution of the ATF since the Early Oligocene were enriched:1)During the Early Oligocene to mid-Miocene, fast strike-slip faulting along the ATF was proposed to accommodate the eastward extrusion of the northern Tibetan Plateau with its sinistral shear confined to the fault itself. While in the NQMTB and farther east area in the Qilian Shan, its sinistral shear was transferred to the interior of the plateau and was accommodated by deformation of differential crustal shortenings and block rotations in these regions. Thus, the displacement along the ATF west of the NQMTB is larger than that east of the NQMTB. 2)Since the mid-late Miocene, sinistral shear of the ATF was widespread distributed within the northern Tibetan Plateau, instead of concentrated to the fault itself. Its sinistral offsets were partially absorbed by the shortening deformation within the Qaidam Basin and the Qilian Shan, leading the offsets along the ATF decreasing to the east. With the sinistral frictional drag of blocks(the Tarim Basin and the Altyn Tagh Range)on the other side during the second stage evolution of the ATF, a transitional zone south of the ATF was likely developed by remarkable CCW rotations during the Middle to Late Miocene, which is probably confined to east of the Tula syncline. Combining the sinistral offsets along the ATF derived from the paleomagnetic rotations during the Early Oligocene to mid-late Miocene and that by piercing points since the Late Miocene, the post Oligocene strike-slip offsets were constrained as at least~350~430km for the reference in the western Qaidam Basin and~380~460km for the reference in the NQMTB, with an average slip rate of at least~10.6~13.9mm/a. The post Early Oligocene offsets are consistent with the widely accepted offsets of~300~500km obtained by piercing point analyses. 相似文献
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巨型左旋走滑的阿尔金断裂是青藏高原的北部边界,在印度-欧亚板块碰撞过程中起重要的调节作用,控制着青藏高原东北部的构造演化,认识其活动演化对理解青藏高原的构造变形过程和机制具有重要意义。阿尔金断裂南侧存在一系列弧形地貌单元,知晓这些弧形带是原始弧形弯曲还是后期由于阿尔金断裂左旋走滑拖曳而形成的,对认识阿尔金断裂的构造演化具有重要意义。文中在前期阿尔金断裂南侧柴西英雄岭和柴北缘2条弧形带不同部位已开展的精细古地磁旋转变形研究的基础上,综合研究区和阿尔金断裂附近已有的古地磁旋转变形研究结果和弧形带几何形态学等其它地质证据,分析发现这2条弧形带的几何学特征是由其不同部位发生旋转变形所导致的,且旋转变形与该时段阿尔金断裂的快速左旋走滑活动密切相关。通过上述工作,更加全面地了解了阿尔金断裂新生代2阶段的走滑特征,进一步限定了阿尔金断裂早渐新世以来左旋滑移量,以柴西段为参照系滑移量至少约350～430km,以柴北缘段为参照系至少约380～460km,平均滑移速率至少约10. 6～13. 9mm/a。 相似文献
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为总结柴英雄岭构造带油气藏地质特征和主控因素,以该区深层和浅层油气藏为研究对象,对油气藏的构造、储层、油气源和成藏演化模式等方面进行了对比研究。结果表明:(1)英雄岭构造带构造样式自西向东变化显著,英西—英中纵向上表现为“双层结构”,而英东构造样式相对简单;(2)英西—英中碳酸盐岩储层主要储集空间为白云岩晶间孔,局部发育溶蚀孔和裂缝集中区,英东碎屑岩储层,主要发育粒间孔、少量粒间溶孔和裂缝;(3)油源对比表明,下干柴沟组上段为区内主力烃源岩;(4)天然气组分及同位素指标表明英西和英中的CH4主要来源于原油伴生气,而英东为凝析油伴生气;(5)由于岩盐层封盖作用,英西—英中深层形成自生自储的异常高压油气藏,而英东虽缺乏盐岩盖层,由深至浅地表现为幕式充注成藏。 相似文献
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