阿尔金-西昆仑加里东中晚期构造作用在塔里木盆地塘古兹巴斯凹陷中的响应

Manifestation of the Middle-Late Caledonian tectonic movement along the Altun-West Kunlun orogenic belt in the Tangguzibas depression,Tarim basin

对塔里木盆地塘古兹巴斯凹陷志留系与奥陶系(S/O3)、上泥盆统与志留系(D3d/S)2个区域角度不整合的三层结构特征及属性进行详细研究,分析了不整合面下构造变形特征、不整合面结构类型分布、不整合面上初始沉积砾岩成分及其物源。发现加里东中期该区形成了塔里木盆地独特的不整合结构,构造不整合(S/O3)明显地受北东东-南西西走向逆冲断裂系控制,在凹陷北部逆冲断裂系上盘发育中等角度单斜不整合和褶皱不整合,沿断裂带形成了多个角度不整合带;加里东晚期不整合(D3d/S)区域上呈现由南向北的剥蚀特征,局部受继承性再活动的断裂控制存在北东东向的中角度单斜不整合带,且构成了加里东中期及晚期的叠合不整合。两期不整合面上的初始沉积砂砾岩有明显差异,加里东中期不整合面上初始沉积以近源的沉积岩为主、物源来自被动大陆边缘;晚期不整合面上的初始沉积砾岩主要为硅质岩和变质岩,物源主要来自较远的被动大陆边缘及大陆岛弧。综合分析表明,晚奥陶世末塘古兹巴斯凹陷主要受到阿尔金、西昆仑的构造作用;中志留世-晚泥盆世主要受到西昆仑及阿尔金碰撞造山活动共同作用。在加里东构造运动中晚期,凹陷中控制不整合发育的NEE向逆冲断裂系与南阿尔金断裂在活动时限、强度、区域应力场上具有可比性。加里东中、晚期不整合的三层结构及其属性是反映阿尔金-西昆仑早古生代构造运动发生、发展、终结动态演化过程的良好证据。

Based on regional seismic profiles,core and drill data of well in Tangguzibas depression,Tarim basin,we research the three-layer configuration of two unconformities,the one occurred between Early Silurian to Late Ordovician（S/O3,T70 seismic reflection horizon）,the others emerged between Late Devonian to Silurian（D3d/S,T60 seismic reflection horizon）.The structure deformation underlying unconformities,the distribution of configuration type of unconformities,the compositions and provenance of elementary sediment gravels overlying unconformities have been analyzed.Three-layer configuration studies have established that the unconformity of Middle Caledonian（S/O3） was an area angular unconformity,presented middle angle monocline or fold between unconformities to its underlying strata on obduction slabs of thrust faults,and the distribution of configuration type of unconformities were controlled by a series of thrust faults with NEE-SWW trending.It＇s unique to Tangguzibas depression,difference to the other tectonic units in Tarim basin.The unconformity configuration of Late Caledonian（D3d/S） was also an angular ones,formed angular unconformity with northward erosion mainly,the part influenced by thrust fault with NEE-SWW trending and inherited development,to form superimpose unconformities.The sandstones and gravels of early deposits overlying on two unconformities had obvious differences,the former deposited varies of sedimentary gravel from passive margin and near provenance and,the later deposited gavels are far provenance relatively,from passive margin and continental island arc.During Late Ordovician,tectonic of Tangguzibas controlled mainly by Altun and West Kunlun collision orogenic action,response more to Altun orogenic action,while affected by West Kunlun and Altun collision orogenic action from Middle Silurian to Late Devonian.The fault system trending NEE which controlled configuration of unconformities has been comparability to South Altun Fault（SAF） on regional stress field,active phase and intensity.The three-layer configuration of unconformity on Middle and Late Caledonian movement responded on dynamic process of Early Paleozoic tectonic movement,and provide evidences for that Altun and West Kunlun orogenic action happened,developed and ended off.