从陕、甘、川三省接壤地区砂金矿矿质来源看在该区寻找岩金矿的可能性

本区6个砂金富集区与6个岩金集中区的空间分布完全相吻合;新构造运动频繁,地质环境动荡,金的次生富集作用效果较差;一部分砂金金粒与石英、蚀变岩石等脉石连生在一起;一部分砂金金粒的成色偏低;有的砂金矿体中部分砾石含金,有的高达3×10^-6~10×10^-6.据此认为研究区内砂金物质来源是以高含金地质体——岩金矿床(点)补给为主,低含金地质体补给为辅.碧口群、志留系、泥盆系作为矿源层,构造条件、岩浆活动均有利于本区岩金矿的形成,而且在矿源层的出露区已有近百处岩金矿床点分布.研究区化探异常、重砂异常30多处且分布较密集,异常峰值较高.研究认为本区确已具备形成更多更大的岩金矿床的地质条件,为此笔者提出勉县-平武找矿远景区.

POSIBILITY OF SEARCHING GOLD DEPOSITS IN THE JUNCTION AREA OF SHAANXI,GANSU AND SICHUAN PROVINCES

The junction area of Shaanxi, Gansu and Sichuan Provinces, where broadly distributed gold deposits and gold placers, is one of the most important gold concentrated region in China. The 6 placer gold concentrated areas spacially coincide with the 6 gold deposit concentrated areas. Neotectonism in the region is frequent, so the secondary enrichment of gold is less efficient. Some placer gold grains intergrow with quartz and/or altered rocks. The fineness of some placer gold is relatively low. Some of gravels in gold placer are gold containing, up to 3×10-6～10×10-6. From above, it is concluded that the source material for the placer is majorly the high-Au containing geologic bodies, i.e. , the gold deposits in the region; and minorly the low-Au containing geologic bodies, i. E. , strata and magmatite. Presinian Bikou group, Silurian and Devonian strata are the source beds. The structural condition and magmatic activity are favorable for the forming of gold deposits. Nearly 100 gold deposits/spots are distributed in the source bed cropped areas. There are densely distributed more than 30 geochemical and heavy mineral anomalous areas, with high peak values. After all, this region is qualified for forming more and larger gold deposits. The author then proposes the Mianxian-Wuping potential area for gold deposit searching.