龙门山北段唐王寨—仰天窝向斜沉积-构造演化与动力学成因机制研究

Tangwangzhai –yangtianwo(T-Y) syncline is a large klippen in the northern section of the Longmen Mountain, and is north-east trending, which is showing that an elongated shape of isolated geological block consisted of Devonian and Carboniferous stratum left on the large tracts of Silurian strata. The formation evolution of T–Y structure is closely related with the rise of the northern section of the Longmen Mountain and the uplift of Songpan-Ganzi plateau. This project is to be carried out research on the following aspects..1) Sedimentary and tectonic background of stratum thickness differences between two sides of T-Y Syncline . .2) Timing and mechanism of overstepping klippe in the T-Y Area.3) structural characteristics of T-Y Syncline and its linkages with regional tectonic controlling..4) Seismic and geological profiles of the `T-Y Area and their structural modeling.5) the study on the formation evolution and dynamics of T-Y structure..By these studies above, the relationships in different periods between the T-Y structure and the leading edge of fault which is called Pengguan fault, and between the T-Y structure and the central fault which is called Yingxiu-Beichuan Fault, can be found out. Meanwhile, the activity time and periods of the T-Y structure and contacting relationship between it and abdominal structure fragments can be clear. And then the formation evolution process and genetic mechanism of T-Y structure can be revealed, which can provide a scientific basis for the further study on the rise of the northern section of the Longmen Mountain and on the uplift of the Tibetan Plateau.

唐王寨—仰天窝向斜是龙门山北段一大型飞来峰，呈北东走向，表现为在志留系之上残留一块由泥盆系、石炭系构成的长条形孤立状地质体。唐王寨构造的形成演化与龙门山北段崛起、松潘甘孜高原的隆升息息相关。本次拟从以下5个方面进行研究：.1、.唐王寨—仰天窝向斜两翼地层厚度差异沉积-构造背景研究.2、.唐王寨—仰天窝 “叠覆式”飞来峰形成机制与时限研究.3、.唐王寨—仰天窝向斜构造特征及与周边构造依控关系研究.4、.唐王寨—仰天窝构造地震-地质大剖面及形成演化构造物理模拟研究.5、.唐王寨—仰天窝构造形成演化与构造动力学成因机制研究.通过以上研究，搞清唐王寨构造在不同地史时期与龙门山前缘断裂（彭灌断裂）、龙门山中间断裂（映秀北川断裂）的构造依控关系，明确唐王寨构造活动时间、活动期次及与下腹构造断片的接触关系，揭示唐王寨构造的形成演化过程与成因机制，为进一步研究龙门山北段的崛起、青藏高原的隆升提供科学依据。

通过野外地表地质调查，结合钻井资料和地震剖面精细解释，并运用平衡剖面技术与构造物理模拟实验，对研究区的构造特征及其演化规律进行研究，分析唐王寨-仰天窝复式向斜的成因机制。得到以下认识：.（1）唐王寨-仰天窝复式向斜呈北东-南西向展布，轴面倾向南东。显示出极不对称的特点，向斜两翼变形变位强度差异较大。北西翼地层变形较弱；泥盆系倾向南东，倾角较缓，地层发育完整且厚度巨大。南东翼地层变形较强；泥盆系倾向北西，倾角陡立，地层残缺且厚度较薄。.（2）研究区的构造样式具有分层分带特征。平面上，地表构造以马角坝断裂、T/J不整合界面为界，可分为逆冲推覆体、山前断褶带及四川盆地。剖面上，以①号断裂为界，山前断褶带又可划分为上盘复杂断褶带、下盘复杂断层转折背斜带。研究区的滑脱层主要为寒武系长江沟组砂泥岩、志留系泥页岩和三叠系中下统膏岩层。根据滑脱层的分布特征，地腹构造可划分为三个构造变形层：寒武系滑脱层以下，地层构造形态相对简单，构造稳定；寒武系滑脱层与三叠系滑脱层之间，构造变形复杂，断层极其发育；三叠系滑脱层以上地层，断层发育少，表现为被动变形。.（3）通过平衡剖面恢复，认为研究区主要经历了以下构造演化阶段：a、加里东期至海西期，主要表现为拉张动力学背景，发育小型同沉积正断层；b、印支期，为拉张背景下的差异隆升阶段，形成唐王寨-仰天窝复式向斜及其前缘的逆冲构造雏形；c、喜山期，构造动力学背景由拉张转变为挤压。构造特征以逆冲推覆为主，前期形成的构造样式在该时期得以改造，最终成型。.（4）通过构造物理模拟实验，认为研究区复杂构造的形成是由于印支期造陆运动过程中的差异隆升，形成高原-斜坡-盆地的盆岭耦合关系，斜坡带表现为剪切动力学环境，盆地区表现为挤压动力学环境。位于斜坡带和盆地过渡部位的唐王寨-仰天窝复式向斜及其前缘的逆冲推覆构造就是在此构造环境下形成的，后经喜山期北西-南东向挤压作用对先期构造进行改造，最终成型。