豫西北太行山奥陶系露头区裂缝发育特征及主控因素

在总结前人研究资料和实地观测豫西北太行山奥陶系5处露头区的基础上，运用地质统计学与构造应力场分析的方法，对豫西北太行山奥陶系露头区裂缝发育特征及其主控因素进行了研究。结果表明：研究区以高角度裂缝为主，可分为北北西、北西西、北北东和北东东向4组，裂缝切深变化较大，野外可见的切深多为0.15～1.4 m，裂缝线密度为1～10条/m，裂缝张开度一般介于0.1～3 cm之间；裂缝充填程度包括未充填、半充填和全充填3种，以未充填裂缝为主，半充填和全充填裂缝次之；裂缝充填物以方解石为主，灰泥质充填和铁质充填次之。通过对研究区裂缝主控因素和成因机制分析，认为其主要形成于古近纪、中新世、上新世至更新世早期、中更新世以来4个时期；构造作用、岩性和岩层厚度是影响其发育的最主要因素，其中构造作用对裂缝的倾向、倾角、张开度、切深、充填状况等影响较大，岩性及层厚与裂缝线密度关系密切，岩层内白云质含量愈高裂缝越发育，且裂缝线密度平均值与岩层厚度平均值具有良好线性关系。

Fracture Characteristics and Main Controlling Factors of Ordovician Outcrop Zones of Taihang Mountains in the North-west of Henan Province

Based on the summarizing of previous studies and the field observation of five outcrop zones of Taihang Mountains in the north-west of Henan Province, the fracture characteristics and main controlling factors were studied by using methods of geostatistics and tectonic stress analysis. The results show that high-angle fractures are the main type in the research area, which can be divided into four groups, i.e.NNW, NWW, NNE and NEE directions. The down-cutting depth of fractures changes greatly from 0.15 m to 1.4 m. The linear density is 1 to 10 per meter and the fracture opening width is usually between 0.1 cm and 3 cm. The fracture filling degree includes unfilled, half-filled and completely filled types, which is characterized by the dominance of unfilled type. The fracture fillings include calcite, plaster mass and irony materials, which are mainly calcites. By analyzing the main controlling factors and the genetic mechanism, it is deduced that the fractures formed in four periods, i.e.Paleogene, Miocene epoch, Pliocene epoch to Early Pleistocene, later Middle Pleistocene. Tectonism, lithology and layer thickness are three main factors that affect the fracture development; the tectonism has a significant influence on the trend, dip, opening width, down-cutting depth and filling condition; the linear density is closely related to lithology and layer thickness; the fractures is developed with the growth of dolomitic content, and the mean value of linear density has a good linear relationship with the mean value of layer thickness.