APPLICATION OF GIS TO TEMPORAL AND SPATIAL ANALYSES OF PRIMARY AND PLACER GOLD DEPOSITS OF CHINA

Gold databases of China, including 1,500 gold deposits, were built under ACCESS and nation-wide map layers with their attribute tables, concerning the tectonic framework, stratigraphy and igneous rocks, were also created under ARCINFO and ARCVIEW on the basis of nearly a thousand of references. The temporal analysis shows that Chinese gold placers were formed in the Quaternary whereas lode gold reserves are mainly of Jurassic-Cretaceous age, forming 64.6% of the national total (based on 246 Au-only and associated lode Au deposits with available age data). The spatial analysis reveals that 52.5% of lode gold reserves of the national total (ca 1,000 Au deposits) are distributed within the 0～40km buffer zone of gold placers and those in the 5～25km buffer zone amount to 33.2%, indicating that in general lode gold deposits principally provided gold for placers within their 5～25km distance. The total placer gold reserves of China (around 500 placer deposits) amount to 916.9 t (contributing 11.6% of the total Au reserves from both lode and placer deposits) and are notably less than that of Australia (25.2%), which is inferentially ascribed to that Australian lode gold deposits are primarily of Archaean and Palaeozoic age and eastern China, as a major gold producer, experienced large-scale crust thinning in the Mesozoic and Cenozoic (particularly in Tertiary) after the Jurassic-Cretaceous gold veining peak. The 5～25 km buffer zone of gold placers and possible deeper buried depth of lode gold deposits as a whole in eastern China should be macroscopically considered in the gold exploration though why there are less lode gold reserves in the 0～5km buffer zone of placers is still uncertain. Through quantitatively evaluating and geological setting analyzing of 24 gold placer concentration areas in China Western Qinling, the Songpan-Ganzi Block and the Lhasa Region are selected as a prospecting area for further studies of gold placers in order to locate unknown lode gold resources there.