Application Of GIS In Geochemical Anomaly Evaluation, Southeastern Yunnan Province

The southeastern Yunnan is located in "Yunnan-Guizhou-Guangxi Golden Delta" which is known all over the world by it is one of concentration areas of Carlin-type gold deposit. But now people only find one medium-large gold deposit named Laozhaiwan, that is mean in the number of gold deposit, Yunnan is much less than Guangxi and Guizhou. The phenomenon is mostly because of its special geological landscape conditions.The study indicates that the element supergene mobility in southeastern Yunnan is controlled by not only geologic setting but also landscape conditions. So the elements have different state and grain if they enrich in different landscape conditions, all these make the geochemical background of this area huge difference. In the hilly area of karst, geochemical background on the high side and in the medium hill area of flowing water, geochemical background is on the low side.Under the circumstances, according to the new idea of appraising regional geochemical anomaly, we use the space analysis technology of GIS to choose anomaly. Firstly, handle geochemical data by different methods of the region, including traditional data processing, lining value processing and filtering processing method. We find that if using the unified background, unified anomaly threshold to delineate anomaly, the effect is not good, but if we handle the data by lining value processing or filtering processing method, and then delineate anomaly, it can effectively solve the problem of bad comparability because of both geologic setting and landscape conditions, especially extrude the weak anomaly in low geochemical background. Secondly, build a Carlin-type gold deposit model according to the geochemical conditions. At last, use the result of data processing and the space model by the space analysis technology of GIS, and then use the method of arithmetic weighted superposition to do geochemical integrated forecast of Au. We delineate7gold target areas that more promising in the southeastern Yunnan in all.