金矿化探

GEOCHEMICAL EXPLORATION OF GOLD

使用地球化学方法找寻金矿床近年来在我国取得突破性进展。这是因为我国将金列为区域化探全面扫面必分析的元素,将金的分析捡出限降至百亿分之几,并研制了高效率的能达到这样捡出限要求的分析方法。但今后要使化探找金的效果继续提高,还需加强研究工作,包括综合研究已发现的大量金与其伴生元素的区域异常,金在表生环境中的行为及金矿床的原生晕并探索找金的地球化学新技术。

In recent years, outstanding achievements have been gained in China in the exploration of gold using geocliemical methods. From 1980 to 1986, 81 new gold occurrences wore found, many of Which have been developed into economic deposits.Comparison of the philosophy and strategy of gold geochemical exploration in China and abroad has found that the effective use of geochemical methods for gold exploration in China relies heavily on the direct determination, of subtrace gold rather than the determination of pathfinder elements or discrete gold in mineral concentrate. China's Regional Geochemistry-National Reconnaissance Project is one among the few national geochemical mapping projects which puts gold in its list of elements that ought to be analyzed.Several sensitive, rapid and low-cost analytical methods were developed to bring down the detection limit of gold to 0.3 ppb.The result is that more than 90% samples could yield reportable data, end the local high background values end the regional end local anomalies of gold could all be clearly displaged oa a geochemical map.The amount of information obtained is unparalleled comparing with whatsoever gold maps generated in other countries.It was found that large gold deposits or gold fields are always encicled by conspicuous regional gold anomalies with areal extension of several hundreds of square kilometers and threshold values of only a few ppb. These regional gold anomalies not only enlarge the scope of exploration targets but also provide a powerful means for discrimination large economic gold deposits from small gold occurrences during interpretation of geochemical maps. Another important feature in geochemical gold exploration in China is the extensive use of seven geochemical standard reference samples GAn 1-7 to monitor the gold analysis, thus makes the gold data of this national project comparable over the whole country.The highlight of gold exploration activities and the vast amount of information accumulated put forward new problems, end offer new opportunities for exploration geochemists.Several suggested research topics are listed below.1. Comprehensive study of the rsgiortal multi-element anomalies associated with gold minaralization. The vast amount of data obtained all over China are standardized and hence comparable.So it offers a chance unprecedented before for the systematic study of element association and element zoning of different types of gold mineralization and for the establishment of creiteria for interpretation, classi- fication and sorting of regional multi-element fnomalies ssociated with gold mineralization.2. The behavior of gold in surfacial environment, the study of the behavior of gold in the bio-chemical system of surfacial environment has attracted the interest of scientists from different disciplinss. The development of gold exploration techniques in the past including sampling, analysis and interpretation has deen largely based on the assumption that gold migrates in surfacialenvironment chiefly as discrete particles. The new idea that gold could migrate as ions, colloids or organic complexes will certainly innovate gold geochemical exploration techniques.3. Primary halos around gold deposits. Element association end element zoning of primary halos around gold deposits have not been studied as throughly as that around polymetallic, copper or tin and tungsten ore deposits. This kind of research must be strengthened to meet the great demand in detailed geochemical study of the targets sorted out after regional survey, in order to evaluate the potential of the anomalies and the erosion level of the predicted ore bodies and to discriminate between scattered and industrial gold mineralizations.4. New techniques in gold geochemical exploration. Because of the establishment of the hydromorphic migration of gold and the important role of vegetation end bacteria in transfering gold into soluble forms, we could see in the years to come the increased application of biogeocheinical and hydrogeochemical methods in the exploration of gold, especially