Abstract：Dabeiwu gold deposit,where Au is the only useful element,belongs to sulfide-poor mylonite quartz vein type Natural gold is the dominant occurrence form,in which almost all Au component concentrate There is utmost small amount of electrum in the ore,and secondary micro-gold may be found in galena,but the content of gold is very little Quartz,pyrite and arsenopyrite are the main carriers of natural gold The fineness of the natural gold is quite high.Most of the gold occur as medium-macrograined crevice-gold,with minor intergranular gold and less inclusion gold Chalcopyrite,galena and sphalerite are closely related to natural gold,although their contents are low They are usually found intergrowing with natural gold in macrograined pyrite and arsenopyrite The mineralization of the three sulfides is the indicator to rich ores The Pb isotope result shows that the ore-forming material is derived from pre-Cambian metasedimentray rocks Mesoproterozoic Shuangqiaoshan group is the source bed of ore Au migrates as complex and precipitates as the decreasing of temperature (< 300℃) and prssure At the early stage of mineralization,the pH value of inclusion in quartz vein is 4.91, Eh 164.52 During the main stage of mineralization,the pH value gets up to 6.38~6.72,while the Eh value lowers down to 57.44 The lowered dissolubility of Au in solution makes the precipitation of Au
1999, Vol. 8 
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