DISCUSSION ON THE APPLICATION OF THE ROCK MAGNETIC FABRIC METHOD IN RESUMING PALEOTECTONIC STRESS FIELD IN SEDIMENTARY BASIN

The quantitative resumption of the paleotectonic stress field in the sedimentary basin has long been a difficult problem due to the shortage of the stress symbols.In order to probe the feasibility of using rock magnetic anisotropy to resume the direction of the maximum principle stress of the paleotectonic stress field in sedimentary basin,an experiment has been made at first to investigate the change of the magnetic anisotropy before and after the rock is slowly pressurized and deformed.After the rock is pressurized,the magnetic anisotropy parameters of H,P and q increase accordingly,the maximum and the minimum principal axes of the magnetic susceptibility also change significantly,indicating that the tectonic deformation process in the shallow formation may exert obvious influences on the rock magnetic anisotropy.A comparison analysis between the direction of the maximum principal compression stress determined by the minimum principal axis of magnetic susceptibility and that determined by the tectonic deformation analysis were then carried out in the northern Tarim Basin.The results show that the two is roughly consistent,suggesting that,in the area with strongly deformed structures,it is feasible to use the direction of the minimum principle axis of magnetic susceptibility in determing the direction of the maximum principal compression stress of the magnetic susceptibility of the paleotectonic stress field in the sedimentary basins.At last,some related issues such as the applicable scope of this method and the stage division of the tectonic stress field have been discussed.