Identifying geochemical anomalies according to the content and coefficient variance of trance elements
Zhou Shuguang1,2,3,4, Zhou Kefa1,3, Cui Yao1,3, Wang Jinlin1,3, Ding Jianli2
1. Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Ürümqi 830011;
2. College of Resource and Environment Sciences, Xinjiang University, Ürümqi 830046;
3. Xinjiang Key Laboratory of Mineral Resources and Digital Geology, Ürümqi 830011;
4. University of Chinese Academy of Sciences, Beijing 100049
Identifying of geochemical anomalies from geochemical data is one of the most important tasks, and which is the reason why it is get extensive attention in the field of mineral resource exploration. Most of the geochemical anomaly identification methods pay more attention to the calculation of anomaly threshold, however, there is no one method which is widely accepted yet. To get more reliable and reasonable geochemical anomalies from geochemical data, the 1: 200 000 geochemical exploration data, which comes from Karamay area, at the west of Zungar, Xinjiang, are selected to identify geochemical anomalies. The data are mainly collected from stream sediment, and the content of 39 elements are determined from every sample. In this study, silver(Ag), arsenic(As), gold(Au)and antimony(Sb)are selected as trace elements of gold deposits. ArcGIS software package is used to produce the raster maps of Ag, As, Au and Sb, then Matlab software package is used to get the coefficient variance maps of Ag, As, Au and Sb with window-based method based on the four raster maps. The synthetic anomaly maps of Ag, As, Au and Sb are produced according to their content and coefficient variance, then the synthetic anomaly maps are compared with the anomaly maps from conventional method. The result shows that the synthetic anomalies can indicate the known gold deposits in this area more clearly than conventional method. The synthetic geochemical anomalies are more reasonable and interpretable according to the theory of the formation of dispersion halo of geochemical element. At last, principal component analysis technique is used to get the multi-element geochemical anomaly map. The multi-element geochemical anomaly map can be helpful for further exploration task in this area, and the technique in this study may be explored and used in other places.