中国金的地球化学省及其成因的微观解释

Gold Geochemical Provinces in China:A Micro-and Nano-scale Formation Mechanism

利用全国1:20万区域化探扫面600×104km2和东天山、中蒙边界1:100万地球化学填图86×104km2的金分析数据,在全国圈定了15处金的地球化学省集中区,并发现与金矿成矿带或大型矿集区有关的地球化学省都具有多层套合结构特征。这种具有多层套合特征的地球化学省的形成是由高背景岩石、成矿作用和矿床风化产生的次生分散相互叠加的结果。高背景岩石提供了成矿元素的初始物源,成矿过程使得元素的进一步活化和富集,矿床风化产生元素的点源分散进一步形成叠加异常浓集中心,最后形成了具有多层套合的地球化学异常。通过使用微米和纳米观测手段发现地球化学样品中存在大量微米至纳米级金微粒,这种金微粒具有极强的活动性,能被各种营力作长距离搬运,形成了大规模具有多层套合特征的金地球化学省。

Fifteen geochemical provinces of gold were delineated based on the geochemical data of 1：200000 Regional Geochemistry-National Reconnaissance（RGNR） project covering about 6000000 km2,and 1：1000000 geochemical mapping projects in eastern Tianshan,Sino-Mongolian border and eastern Heilongjiang totaling about 860000 km2,in China.It was found that all gold geochemical provinces related to gold metallogenic provinces or ore districts have nested hierarchical geochemical patterns.The patterns are induced by rocks with high background values of gold,mineralization processing and secondary dispersion by ore deposit weathering.Rocks have provided initial endorment accumulation for the gold provinces,mineralization processing led to the further enrichment of gold,and the secondary dispersion of ore body weathering form concentration centers of the anomalies.Micro-and nano-particles of gold widely observed in geochemical samples play important role in the formation of large-scale geochemical anomalies,because micro-and nano-particles of gold are mobile to be transported by various forces.