楚雄盆地北部上三叠统一侏罗系裂缝发育期次

Development periods of fractures in the Late Triassic-Jurassic in the north Chuxiong Basin

运用露头描述，裂缝充填物稳定同位素分析，包裹体测温、石英自旋共振测年分析、定向样品声发射实验和岩石力学性质测定等方法，研究了楚雄盆地北部上三叠统一侏罗系裂缝的形成期次和控制因素。认为裂缝发育经历了5个时期：第一期裂缝形成于燕山早期，裂缝充填物包裹体均一温度约95℃；第二期裂缝形成于燕山晚期，均一温度为110～130℃；第三、第四、第五期裂缝舂别形成于喜马拉雅早期、早中期和中晚期，均一温度分别约为146℃、173℃和220℃，以喜马拉雅期中晚期构造活动最强烈，产生的破裂最强。研究区裂缝发育主要受两个因素控制：①构造应力强度决定的岩层构造变形程度，一般变形程度越大，构造裂缝越发育，如构造高部位，轴部等裂缝较发育。②岩石本身的力学性质及刚性岩石的分布情况、岩层厚度等，随着岩石密度降低，孔隙度增加，抗张强度减小，易产生破裂；砂层厚度越薄，裂缝越发育，二者具有幂函数关系。

The development periods and control factors of fractures in the Late Triassic-Jurassic in the north Chuxiong Basin were determined by using the outcrop description, stable isotope and inclusion thermometric analysis and ESR of fracture fillings, theacoustic emission of oriented specimen and the rock mechanics property survey. About 5 stages of fracture development have been identified as early Yanshan Period, in which the fracture fillings homogeneous temperature of inclusions was about 95℃; late Yanshan Period, the homogeneous temperature being 110-130℃; and the 3rd, 4th, and 5th fractures were developed in early, middle and late Himalayan Period, respectively, and the homogeneous temperatures were about 146℃, 173℃ and 220℃, respectively. The fracture development has been controlled by 2 factors:① the structure deformation degree was determined by tectonic stress intensity. Generally, the more deformities, the more tectonic fractures were developed.② the mechanical property of rock, the distribution of rigid rock and the thickness stratum are important. The formations have more fractures as petrological density and tensile strength decrease and porosity increase. The thinner the formation, the more are the fractures, conforming to a certain power function.