The Research On 1:200000 Lead-zinc Geochemical Anomaly Information Processing In Lhasa, Tibet

How to reasonably determine and identify the geochemical anomalies areas has been a core question in exploration geochemical data processing. To find the geochemical information relevant with mineralization from a large number of geochemical raw data is the important purpose of geochemical data processing and research. However, ore-forming elements can form big ore in low background values areas, while in the high background region are not necessarily metallogenic. It is said that in the low background values region it willa also exists abnormal information. How to reasonably traps the geochemical anomalies in a low background value area has have also become a core issue of geochemical exploration.This paper adopts the traditional method, the fractal theory, the trend surface method and geochemical mineralization energy field method to trap the lead-zinc deposit geochemical anomaly in Lhasa - TseDang area. Through the contrast of these methods, we discover that the geochemical mineralization field method is suitable in this area. There are these reasons below:①In the geochemical mineralization field method the variation functions has been the basic tools, and it has not only considered the randomness of geochemical data, but also considered the relevance of geochemical data;②The abnormal sphere of influence has been determined and the space structure and spatial distribution characteristics of geochemical data has been studied by variation functions;③This method can process and reflect ore abnormal information for maximization in low background values region or concealed ore district.④In exceptional classification we combine anomaly map and background image, will not miss the high background value area and can response the low background value abnormal region effectively.Through fitting the variorums'curve of lead-zinc mineralization energy in the district, we get the below conclusion :①The existence of the base station value for semivariable function curves reflects that the"nugget effect"of lead-zinc deposit in Lhasa - TseDang area is widely spread;②The differences between base station value of the lead-zinc deposit semivariable function curves in different directions shows that the lead-zinc deposits appears the"ribbon anisotropic structure"in the space;③The base station values of the lead-zinc semivariable function are small; this reflects that the random phenomenon of the "nugget effect" of lead-zinc deposit is weaker and the spatial structure of lead-zinc deposit is very strong;④Through the structure suits of semivariable function curves in different directions, it shows that the abnormalities exhibition of lead- zinc deposits in the area is basically the same in NE-SW. The structure suit variable distance of lead is 11.85 Km while the zinc's is 13.94 Km. This suggests that the abnormalities area of lead and zinc is basically consistent and the scale of mineralization is large. It is also accord with the actual situation of the concomitant of lead and zinc.According to the geochemical anomalies trapped by the geochemical mineralization energy field method and with the actual geology of Lhasa– TseDang area, we give the reasonable explanation and proceed a metallogenic prospective forecasts. Based on all the above, we get the below conclusion:Judging from the geological aspects, there are some relationship between the mineralization and the hydrothermolite, subprime fracture and magmatic rocks of Himalayan– yanshanian. This is consistent with the mineralization range trapped with geochemical mineralization field method. Based on the above, we forecast the metallogenic with the anomaly and get the conclusion:①We trapped 6 grade vision zone in levelⅠ, 9 grade vision zone in levelⅡ, 10 grade vision zone in levelⅢfor the lead; and we trapped 5 grade vision zone in levelⅠ, 8 grade vision zone in levelⅡ, 9 grade vision zone in levelⅢfor the zinc.②The lead-zinc anomaly is distributed in YeBa group, LinBuZong group takena group and ChuMuLong group, and these formations all are good ore formation for lead-zinc deposit.