超大型金矿床成矿流体某些特征及其找矿

具有重要意义的金─石英脉型矿床可作为研究超大型金矿床成矿流体特征及其找矿问题的良好实例。研究和对比分析表明：（１）在超大型和非超大型金─石英脉型矿床间，在成矿流体包裹体方面尚未发现有意义的区别。似乎不存在能形成上述类型的超大型金矿的任何独特流体。（２）有利的大地构造和区域地质背景，良好的导矿、配矿和容矿构造，适宜的围岩，丰富的成矿物质，大量富含ＣＯ＿２的流体活动，多期、多次、多成因的地质作用的叠加，强烈而又广泛的围岩蚀变是形成某些内生超大型金矿的必要条件。系统扎实的基础地质工作、先进的科学手段和物化等方法的综合运用以及宏观和微观的结合对寻找超大型金矿十分必要。

CHARACTERESTIC AND PROSPECTING PROBLEMS OF ORE-FORMING FLUID OF SUPERLARGE GOLD DEPOSITS

The general characteristics of the Au-quartz vein type deposits in the world, in-cluding some large and medium-small deposits in China, have been well studied. The fol-lowing conclusions can be made by comparing the physico-geochemical conditions and themineralizing characteristics of the superlarge gold deposits with those of some medium tosmall sized gold deposits:(1) There is no significant difference of ore-forming fluids be-tween the superlarge and middle or small Au-quartz vein deposits.It seems there was noany unique ore-forming fluid formed the superlarge gold deposits metioned above. (2)Benefical geotectonic,tectonic and regional geological settings,good structure for thetransportation, distribution and deposition of ore-forming materials, suitable wall rocks,plentiful ore-forming materials, activities of vast amount of fluids rich in Au and CO_2, su-perimposition of the multiple periods,times and types of metallogenical geological process-es and,strong and extensive alteration of wall rocks are the essential conditions for theformation of some endogenous superlarge gold deposits. (3) Generally, polygenesis,mul-tiple stage activities and superimposition of ore-formation are the notable characteristics ofsome superlarge gold deposits.The geneses of some such large ore deposits are very com-plex.Fluid inclusion study would solve some very difficult problems about the evolutionproesses of the ore-forming fluid and the prospecting criteria.Systematic,intensive and basic geological work,advanced scientific methods, multi-ple application of geophysical and geochemical methods as well as the link of macroscopicand microcosmic studies are essential for the study and prospecting of the superlarge de-posits.The discoveries of the Olympic Dam Cu-U-Au deposit and the Carlin gold depositare good examples.