福州盆地断层擦痕构造解析及其应力场反演

STRUCTURAL STRIATION ANALYSIS AND INVERSION OF STRESS FIELD IN FUZHOU BASIN

本文通过野外测量众多的断层擦痕,经过计算机反演应力场,并结合地质资料分析,认为本区自中生代末至第四纪存在着四期构造应力场。

Fuzhou basin is one of the typical basins on southeastern margin of China continent In the basin two groups of faults have been found. There are NNW-NW-and NNE-NE-trending faults. The NNW-trending Ba'yi reservoir-Wangjuan fault is active and also is a well-known heat-flow anomaly zone.The calculation of striats along the faults on the bedrock outcrops within the basin and its boundaries by using Etchecopar's computerized method shows that there were four important stress fields since Yanshanian phase. The first stress field was compressive in NW-SE orientation, which caused reverse fault, schistosity and mylonite zone to be formed. The second was compressive in SN or NNE orientation, but in the state of compression which produced Paleogene diabase dykes along NNE-trending faults. The third was compressive in nearly EW or WNW orientation, R = 1, σ2=σ3, but in a extension state. The evidence for the third stress field is tension-shear horizontal striation on the walls of the basic dyke formed from Neogene to Quarternary. For the fourth stress field maximum principal compressive stress was vertical, indicating that the basin is in an exten-sional tectonic environment.