摘要
本文在阐述郯庐断裂带北延重要分支密山—抚顺断裂带西南段基本特征的基础上,从动力学角度对该断裂带中、新生代不同尺度构造形迹分别进行研究。分折了与该断裂带有成因联系的大、中型伴随构造反映主干断裂活动时限及应力场方向的情况。并结合节理统计、岩组分析资料,得到一个统一的、有联系的区域构造应力场演化规律。即燕山早期该断裂带区域构造应力场最大主压应力σ_1方向为近 SN 向(NE10°±10°);燕山晚期σ_1为北东向(NE50°±10°);喜山期σ_1为近 EW 向(NE90°±10°)。作者认为该断裂带古构造应力场的演化规律与板块运动存在着联系。
The NE—trending Mishan—Fushun fault is a major branch of Tancheng—Lujiang wrench fault zone spreading northwards.Based on information from field investigation including the da macro-,meso-,and micro-structures,this paper discusses the geodynamic evolution of the fault.The nature of the fault zone has changed in consecutive episodes since late Triassic Period.The large sinistral strike-slip displacement started probably in Indosinian orcgeny and intense movement took place in the earlier Yanshanian orogeny.The fault zone had turned to a tension graben from late stage of Early cretaceous to Eogene. From Neogene to present the zone has changed to both compressive reverse faults with small dextral displacement. A series of the associated structures produced on both sides of the fault zone, such as vortex structures,lambda-type struc-tures and so on,all of these indicate that the maximum principal compr essive stress axis of regional stress field in NE10° ±10° in J_2-K_1.A large number of structural basins developed in K_2 -E along the fault zone or parallel it.The basins show that the stress orientation was NE50° ±10° during that time.After that,a few of basins, which orientation is close to E-W,and some right-lateral-reverse-slip phenomena occurred in Neogene.These faults mean that the fault must be compressed by stress of near E-W. According to dynamic analysis methods,the auther studied the data from statistics of regional joints and petrofabric(especially in c-axis).It is considered that the main content of tectonic stress field is based on the determination of point stress states,i.e.the orientation of principal stress axes and the study of the distruibution of tectonic stress of different tectonic stages in the working area.The time and orientation of the tectonic stress field is determined at three tectonic stages.They are NE10° ±10°(Pre-K_1,)NE50° ±10° (K_2-E)and 90° ±10°(from N to present,respectively). The evolution of tectonic stress field orientation is considerd to be related to the evolution history of the relative move ment between Eurasian Plate and the adjacent plates.
