Study On Accuracy Of Geological Structure Delineation By Magnetic Anomaly Derivative

In this paper, the study area is located in a Tibetan county, in the middle of mountain-nyenchen tanglha board,its a brittle fracture controled inverse, originated in the inside of the granodiorite quartz vein type molybdenum deposit. The area has a ductile shear zone through the east-west, a fault was affected by the shear zone,which was later filling it with containing ore vein.Finally it formed a type of quartz vein molybdenum ore body. The fault is the main ore-controlling construct. In addition to the quaternary system, other strata are mainly composed of metamorphic hydrothermal contact metamorphic type, which mainly distributed in the intermediate-acid intrusive contact with wall rocks, intermediate-acid intrusive rocks are closely associated with mineralization.At that, the area may have other ore-controlling structure, so we can use geophysical techniques to determine other ore-controlling structures.Tibetan areas have high altitude and poor terrain, compared with other geophysical prospecting method, high-precision magnetic survey and EH4 are good at data acquisition and the precision of data interpretation. Magnetic survey work not only find out the mining area within the magnetic characteristics of delineating magnetic anomaly body, we also can use magnetic anomaly derivative to delineation structure:(1) by the magnetic data processing maps, it can be seen in the north west to the construction of the line is relatively clear and well continuity. From the magnetic survey on 100 m contour map and vertical second derivative, the mining area divided into four structure named F1, F2, F3 and F4; EH4 is relatively mature in the delineated structure, it has a certain accuracy, so the result is relatively reliable:(2) through the 10 profiles, we can delineated 7 structures, and got the location and rough form; The structure of the use of magnetic anomaly derivative speculation and audio magnetotelluric sounding method to determine the structure, can verify accuracy of magnetic anomaly derivative in the delineation of constructing:(3) by comparing the verification, the fault F1, F2 and F3 which was delineated by magnetic anomaly is consistent with the fault F7, F8, F9(which was delineated by EH4),caused by a lack of line length, failed to validate the F4 accuracy. Overall, the derivative of magnetic anomaly in the delineation of structure has a certain accuracy.