摘要
参阅近千件文献建立中国金矿数据库(ACCESS)及构造格架、地层、火成岩等图层与属性表(ArcInfo、ArcView),对其进行时空分析。中国砂金矿主要形成在第四纪,而原生金矿则主要形成在侏罗—白垩纪(占原生金总储量64.6%)。空间分析发现,超过半数的原生金矿金储量(52.5%)分布在砂金矿0～40km缓冲域中,其中5～25km缓冲域中为33.2%,而0～5km缓冲域中仅3%,表明原生金矿主要为5～25km内砂金矿提供矿质。此外,中国砂金矿金储量916.9t,占总储量的11.6%,明显少于澳大利亚的25.2%,认为与后者原生金矿主要形成在太古代和古生代有关;中国东部中新生代(尤其第三纪)地壳减薄导致此前形成原生金矿的掩埋,可能是造成砂金较少的另一原因,这两种推测与中国缺乏古砂金相吻合。量化分析结合地质背景研究表明,西秦岭、松潘-甘孜地块、拉萨附近为依据砂金找原生金的远景区。
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.
关键词
GIS
原生金矿
砂金矿
中国
GIS
primary gold deposits
gold placers
buffer zone
China
Qinling
Songpan-Ganzi
