【作者】 高金尉；

【导师】 何登发；

【作者基本信息】 中国地质大学(北京) ， 矿产普查与勘探， 2012， 硕士

【摘要】 四川盆地属于扬子地块，位于青藏高原东南缘，是在中上扬子克拉通基础上发展起来的经历了多期构造演化过程的叠合盆地。其前新生代的构造沉积演化受华南板块、华北板块演化及其碰撞拼合后陆内俯冲作用的控制，新生代以来，明显又受到青藏高原隆升的制约。四川盆地西南地区则是二者相互作用最为强烈、表现最为清楚的地区。这些板块的碰撞拼合和高原隆升造成了四川盆地西南地区不同于盆地中部和北部的复杂构造特征，形成了一系列构造，反映了四川盆地在整体运动的过程中内部也发生着复杂的构造变化。另外，研究区内发育了不连续的侏罗系、白垩系、古近系和新近系沉积，这也反映了构造环境的转变以及构造隆升对本区的强烈影响。然而，这些构造隆升发生的时间、经历的若干阶段以及隆升速率等，都没有得到很好的解决，而这些问题恰恰对于四川盆地西南地区的构造变形时间、变形速率和变形机制等的限定，具有非常关键的约束作用。本文以构造年代学、断层相关褶皱理论、构造地质学和临界锥顶角构造楔理论等为基础，综合应用最新的地质、地震和钻井资料，结合野外地质剖面，对四川盆地川西南地区的构造变形时间进行约束，对研究区内地震剖面进行较为精确的限定和精细的分析，研究区内构造平面展布和几何学特征，定量分析不同构造的变形时间和缩短量等，建立区内地质结构剖面，为四川盆地西南地区的地质结构的解析提供合理的解释方案，为川西南地区油气的勘探提供有效的参考，并为青藏高原东南缘的动力学背景提供一定的信息和约束。论文主要取得了以下成果和认识：（1）区内构造在平面上成排出现，在平面上自北西到南东可分为龙门山山前带、大兴背斜（隐伏构造）、熊坡-东瓜场背斜带、龙泉山背斜、威远背斜、孔滩-邓井关背斜带和青山岭背斜。剖面上以震旦系软弱层和下三叠统嘉陵江组-中三叠统雷口坡组膏盐滑脱层为界分为浅、中、深三层构造样式。不同层次上各构造带的变形特征有差异。（2）区内浅、中、深三层总的缩短量分别为19.1km、5.8km和15.4km，这说明四川盆地西南地区存在分层滑脱现象。（3）根据磷灰石裂变径迹结果，龙门山南段、熊坡背斜和威远背斜等不同构造带在隆升时间、隆升阶段和隆升速率等方面表现出了一定的差异性。龙门山从晚白垩世以来开始快速崛起，而且至少是在30Ma开始加速，并在5Ma以来强烈隆升。表明青藏高原对四川盆地的影响可能是从30Ma开始，并在5Ma以来更加显著。（4）研究区存在两个临界锥顶角构造楔，分别为以震旦系基底软弱层与地表斜坡组成的深部临界锥顶角构造楔和以下三叠统嘉陵江组-中三叠统雷口坡组膏盐滑脱层与地表斜坡组成的浅部临界锥顶角构造楔。两个构造楔的强度可靠范围为0.5-1.0，底部滑脱层强度的范围分别为0.018-0.03和0.025-0.042，说明两个构造楔的滑脱层极其软弱。（5）深部构造楔的流体压力比要大于浅部构造楔的流体压力比，说明深层滑脱层要比浅层滑脱层更加软弱。（6）深部构造楔未达到临界状态，浅部构造楔则已经达到了临界状态。深部锥顶角构造楔的次临界状态是造成龙门山冲断带地震多发的原因。更多还原

【Abstract】 Sichuan Basin belongs to Yangtze Plate, and lies on southeast margin ofQinghai-Tibet Plateau. It is a kind of superposed basin based on the Middle and UpperYangtze Craton and having undergone multi-stage evolution. Its tectono-deposintionalevolution was controlled by evolution of South China Plate, North China Plate andintracontinental subduction caused by collision of the two plates before Cenozoic.During Cenozoic, uplifting of Qinghai-Tibet Plateau had an apparent effect onformation of Sichuan Basin. Particularly, the southwest region of Sichuan Basin wasthe most obvious and the strongest area which was interacted by collision anduplifting. Moreover, this region had a lot of complex structures which were differentfrom other structures in the middle and north basin. These differences reflecte thatthere had been a complex structural changing in the basin. In addition, this region alsodeposited Jurassic System, Cretaceous System, Paleogene System and NeogeneSystem discontinuous in horizon, and this phenomenon reflectes the changing oftectonic environment and strong effect of structural uplifting. However, thesestructures’ uplifting time, rate and stages are not well answered, and the problemshave a key role in constraining structural deformational time, rate and mechanism.Therefore, based on structural chronology, fault related folds, structural geologyand critical taper wedge, and generally taking advantage of geologic maps, fieldgeologic section, seismic reflection profiles and drilling data, this paper wellinterprets and analyzes seismic reflection profiles in order to study distribution andgeometrics of the structures in region of interest and to calculate quantitativelystructures’ deformational time and shortening and to build the regional geologicconfiguration section. The information can provide rational interpretation scheme forgeologic configuration and valid references for the oil and gas exploration in region ofinterest, and also provide some indications to uplifting settings of southeast margin ofQinghai-Tibet Plateau. The results and conclusions are as following:(1)The structures of region of interest distribute in rows in geologic map, and canbe divided into seven belts from northwest to southeast. They are Longmen Mountains frontier belt, Daxing Anticline (buried structure), Xiongpo-DongguachangAnticline belt, Longquanshan Anticline, Weiyuan Anticline, Kongtan-DengjingguanAnticline belt and Qingshanling Anticline, respectively. The geologic section can alsobe divided into three zones in vertical through the Sinian System weakness layer andLower Triassic Jialingjiang Formation-Middle Triassic Leikoupo Formation saltdetachment, which is shallow zone, middle zone and deep zone structural patterns.And different zones have different structural deformational features.(2)The shallow zone, middle zone and deep zone of region of interest have total19.1km,5.8km, and15.4km shortening, respectively, which reflect that there aremulti-detachment layers with different structural deformation.(3)According to the apatite fission track results, the south Longmen Mountains,Xiongpo Anticline and Weiyuan Anticline have some differences in uplifting time,stages and rate. Longmen Mountains begins to form quickly from Cretaceous, andrises more quickly from30Ma at least than ever before, and uplifts strongly from5Ma.This means that effect of Sichuan Basin which Qinghai-Tibet Plateau has had maybegin to be from30Ma, and be more obviously from5Ma.(4)The region of interest has two critical taper wedges. One is a deep critical taperwedge which is constituted by Sinian System weakness layer and surface slope. Andthe other one is a shallow critical taper wedge which is made up of Lower TriassicJialingjiang Formation-Middle Triassic Leikoupo Formation salt detachment andsurface slope. The reliable field of two wedges’ strength is0.5-1.0, and the reliablefields of their basement detachment strength are0.018-0.03and0.025-0.042,respectively, which reflect detachment of two wedges is extremely weak.(5)The fluid pressure ratio of deep wedge is larger than shallow wedge’s, whichmeans that the deep detachment is much weaker than shallow detachment.(6)The deep wedge is still not reaching to critical taper, but the shallow wedge hadreached. Therefore, the unstable, sub-critical deep taper wedge resulted in manyearthquakes in Longmenshan Mountains thrust belts.更多还原