湘西北奥陶系宝塔组灰岩龟裂纹构造特征、成因及其资源意义

湘西北上奥陶统宝塔组灰岩的龟裂纹构造在岩序上具有"下密上稀、过渡变形、不穿邻层、似泄水充填"的特点,是地史时期一种特殊的沉积构造.为了查明其成因机制及其与扬子海盆演化过程的内在联系,从湘西北龟裂纹灰岩的岩石学特征、裂缝特征、地球化学特征、盆地模型以及综合对比已知成因的"似龟裂纹构造"等诸多方面入手,经研究后认为龟裂纹构造属于一种受准同生期胶凝缩作用影响形成初始微缝,随后在构造挤压控制下、盆地快速下沉、盆内形成异常高压场的流体环境,驱使下伏富水岩层的灰泥物质向上挤入、充填、改造先期初始裂缝而形成.宝塔组龟裂纹构造的研究,为我们探究构造-流体-岩石多重作用机制提供了岩石学方面的资料;同时,该裂纹疏导功能良好,具有重要的成矿(油藏)意义.

Characteristics,Petrogenesis and Resource Significance of the Limestone with Polygonal Reticulate Structure of Pagoda Formation,in Northwestern Hunan Province

The limestone of the upper Ordovician Baota Formation in northwestern Hunan has a crack structure, bearing the characteristics of "decreasing cracks from top-bottom, no crossing between adjacent layers, multi-period deformation, water-like filling" in rock sequence, which is a special sedimentary structure in geological period. In order to find out its genetic mechanism and its internal relationship with the evolution of the Yangtze basin, the author does research from aspects including lithology, fracture characteristics, geochemical characteristics, basin model and comprehensive comparison of the known causes of crack-like polygonal reticulate structure. It is found that the crack structure is a kind of initial slit formed under the influence pen contemporaneous gel condensation. Then under the control of tectonic extrusion, the basin sinks rapidly, a fluid environment in an abnormal high pressure filed is formed in the basin, which leads to squeezing, filling and initial cracks reconstruction from the plaster material in underlying water-rich rocks. This study on the crack structure of the Baota Formation provides petrological data for the study on the mechanism of tectonic-fluid-rock interaction. Meanwhile, a good dredging function of the cracks has an important practical significance for the study on mineralization as well as oil and gas accumulation.