塔东北库鲁克塔格地区中上寒武统白云岩类型与孔隙演化*

对塔东北库鲁克塔格隆起的乌孜里塔格剖面中上寒武统白云岩的岩石学、成岩作用、裂隙—孔隙发育与充填等特征研究认为：可划分为有序度逐渐增加的粉晶白云岩、粉细晶白云岩、中细晶白云岩和中粗晶白云岩及晶洞中的中粗晶、巨晶和鞍形白云石等4种类型；分别对应于早期准同生—浅埋、中浅埋藏、中等埋藏和构造断裂—热液（热卤水）作用4期的成岩阶段；其中，沿走滑断裂—裂隙带、呈不规则的“侵入体” 具有斑点状、条纹—条带、雁行状—斑马、角砾状和不规则状结构的中粗晶、粗晶、巨晶（部分为鞍形）白云岩（石），一般不发光或呈昏暗的暗红色，具有与加拿大西部盆地典型的热液白云岩相似的特征；中上寒武统白云岩存在4～5期构造裂隙和3期以上的充填作用；热液白云岩中以晶间孔、晶间溶孔（洞）、裂隙及沿裂隙的扩溶孔洞为主，主要有二世代的白云石和方解石和少量沥青、石英、微量硬石膏和重晶石等多期充填作用。与西加盆地寒武系部分或全部交代充填缝洞及角砾构造、受来自落基山造山带的晚白垩世至古近系拉腊米（Laramide）构造的被排驱的热液流体交代形成的典型热液白云岩稍有不同，海西晚期（晚二叠世）及燕山—喜马拉雅期（晚白垩世—第四纪）沿挤压—走滑断裂排驱的地层热卤水循环—扩散与交代作用可能是本区热液白云岩的主要成因，储集空间主要由中、晚期构造断裂—裂隙（溶蚀）所致，但不排除成岩早期埋藏或晚期大气水作用对其影响。

Types of dolostones and pore evolution of the Middle and Upper Cambrian in Kuruk Tag area of northeastern Tarim Basin

In a geological analogous study，the Middle and Upper Cambrian rocks from the northern Xingde fault of the Kuruk Tag area，northeastern Tarim Basin，were systematically investigated.These rocks consist of shallow marine platform carbonate rocks，with extensive dolomitization，and show significant differences from the Cambrian hydrothermal dolostones(HTD) in the Western Canada Basin.The Canadian dolostones are genetically related to fractures and breccia zones partially to completely including the fractures and presumably formed due to hydrothermal fluids expelled from the Rocky Mountain fold-and-thrust belt during the Laramide orogen.In contrast，the hydrothermal dolostones(HTD) in the studied Tarim Basin were formed as the result of hydrothermal fluid infiltration and alteration associated with deep-burial diagenesis，possibly controlled by recirculation of formation water in the strike-slip fault zones during the Late Permian(Late Hercynian)in northeastern Tarim Basin.According to the texture，six types of dolostones can be differentiated，including：（1）silt-sized dolostone，（2）fine-medium crystalline dolostone，（3）medium-coarse crystalline dolostone，（4）fine-crystalline dolostone with bright rims and dark cores，（5）saddle dolostone and（6）fracture and vug-lining dolostones，coarse or saddle dolostones.These dolostones form a complete sequence of diagenesis，starting with dolomicrite，and fine-medium crystalline dolostone as the early replacement of calcilutite at shallow-burial，followed by coarse and heterogeneous medium-coarse crystalline dolostone as the result of recrystallization at elevated temperatures in deep-burial，and then saddle dolostone and fracture and vug-lining coarse or saddle dolomite precipitated directly from re-circulated hot formation water.The HTD identified in the Tarim Basin samples display distinct coarse non-planar sucrosic textures，with few intracrystalline pores，intercrystalline dissolution pores.At least four period of fissures，dissolution，cementation，or filling，have been recognized，with the earlier fractures being filled with the late dolostone，partly precipitated dolostone，quartz，bitumen-bearing barite and anhydrite.While the pore development during deep burial has been controlled by original-bedding，fault-fissure，diagenesis，infiltration and hydrothermal alteration process，the later exposure to meteoric water may have been important for the late diagenetic pore system related to dolomitization.