Geochemical Indicators Of Large-sized Ore Deposits In Inner Mongolia

Geologically, Inner Mongolia is great potential for mineral resources. Based on the Regional-Geochemistry National Reconnaissance project data and the Sino-Mongolian Boundary Geochemical Mapping project data, the Geochemical Indicators are established to predict large-sized Ag-Pb-Zn polymetallic deposits and porphyry copper-gold deposits. Potential resources are predicted based on the indicators. The main results are as following:1. On the GIS platform of Geoexpl,312 geochemical maps have been produced using Weighted index method grid Cumulative frequency method.2 Statistical studies show that almost all of the large ore deposits are located in the geochemical provinces, most of the large and medium-sized deposits are hosted by the regional geochemical anomalies. This fact shows that a huge amount of element acumulation is adequate sources for formation of large-sized deposits.3. Based on the known large-sized deposits of Bairendaba-weilasituo-yindou, Erentaolegai-chaganbulagen-jiawula and Xiaoyinzi-Huanggutui polymetallic ore districts, geochemical indicators for large-sized Ag-Pb-Zn pollymetallic deposits are hierarchical geochemical patterns including geochemical province, regional and local anomalies hosting a large-sized ore deposit, an area of a geochemical province and a regional anomaly larger than 500km2 and 100 km2 respectively, enrichment coeffecientindex greater than 1.5, normalized areal productivity (NAP) larger than 1000, direct indicators of associated elements of Ag, Pb and Zn to ore forming, indirect indicators of As, Sb and Hg to hydrothermal activity and V, Co, Fe2O3, Ti to source bed.4 Based on large-sized Wunugetushan and Bainaimiao porphyry copper deposits, geochemical indicators are as follows:element association of Cu, Mo and Ag, anomalous area larger than 100 km2, enrichment coefficient greater than 1.8, associated elements of K2O,SiO2,Y,Th for mineralization environments related to pophyry intrusions.5 At a scale of 1:1000000,31 anomalies promising for silver-lead-zinc polymetallic ore deposits were delineated and 253 anomalies of Cu-Au-Ag were delineated and at a scale of 1:200000,1533 Ag-Pb-Zn anomalies were delineated. Among these,12 anomalies are consistent with geochemical indicators to large-sized Ag-Pb-Zn ore depsots.2115 anomalies of Cu-Au-Ag were delineated and 5 areas consistent with geochemical indicators to large-sized porphyry ore deposits.