关键词: 太行山脉, 奥陶系, 碳酸盐岩, 裂缝, 主控因素

Abstract:

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.

Key words: Taihang Mountains, Ordovician, carbonate rock, fracture, main controlling factor