Research On Geochemical Anomaly Information Extraction And Multi-fractal Method In Delhi Region, Qinghai Province

The study area is located in the southern area of Yeniuji Mountains in Qinghai. This area is rich in resources, and has good metallogenic conditions. How to quickly and accurately identify, screen and evaluate anomaly is the key determining the effectiveness and economic efficiency of mineral prospecting.Through analyzing measurement data of1:50000stream sediments from a certain area in Qinghai by traditional method and multi-fractal method, the lowest limited anomaly value of each element was calculated in this thesis. The lowest limited anomaly value determined by traditional method was usually lower than that by multi-fractal method. Most of the main ore-forming elements in the area did not subject to normal or lognormal distribution, but took on multi-fractal feature with double or more peaks, or high cluster grouping. Most geochemical fields of main ore-forming elements had multi-fractal feature with over two non-scale regions. Multi-fractal method dose not suffer the limitation of normal or lognormal distribution, and it can consider the spatial distribution features of geochemical data, so that it is an effective method to study geochemical fields.This paper used cluster analysis and principal factor analysis to study the paragenetic association law of14elements in the study area, and used scoring anomalies of main factors to represent the association anomaly of main ore-forming elements. According to the correlation coefficient of0.5, the elements were divided into5groups:group of Co, Ni, Cu, Cr, Zn, Mo, Sb, Ag, group of Pb, Bi, Sn, group of As, group of W, and group of Au. When feature value of initial factors’loading matrix over1(λ>1) as selection criteria, the first three factors were chosen, the total variance contribution of which was68.838%and could basically represent the main information of14elements in the study area. Use variation maximum method to make orthogonal rotation transform of initial factors’s loading matrix. When orthogonal factor loading over0.5as standard, the F1factor was mainly the association of Cr, Co, Ni, Cu, Zn, Mo, Ag and Sb, which was correlated with intermediate-acid magmatism, and the high cores area of this factor was mainly near the contact zone of granite and Silurian stratum. The F2factor was mainly the association of W, Pb, Bi and Sn, which was correlated with magmatic hydrothermal process, and the high cores area of this factor was mainly distributed in the granite and Silurian strata in the northwestern of the study area, with a NS-direction zonal distribution. The F3factor was Au, and the igh cores area of this factor was mainly located in the fracture zone in the northeastern of the study area.According to classification and evaluation of anomalies,25comprehensive anomaly fields were circled out in the study area, including2anomaly fields of Class A,8anomaly fields of Class B,15anomaly fields of Class C. The contact zone of granite and Silurian stratum to the west of Yikedaban and nearby in the whole area was the favorable region to prospect gold deposit and granite type tungsten-tin ore. The zone nearby Yeniuji Mountain was the best favorable region to prospect gold ore of tectonic altered rock type.