Mineralization Characteristics And Gold Fractal Of Chang'an Gold Deposit In Southwest Tethys

The Chang'an gold deposit is one of the largest deposits located at the southern section of the Ailaoshan metallogenic belt in westsouthern Tethys.Previous studies on changan mining area mainly focus on material source and metallogenic age but he specific distribution of gold elements has not been studied.The study on the spatial distribution of gold concentration and its controlling factors is insufficient.Fouced on fractal technology,basing on the detailed geological investigation and microscopic identification,we find the factors of gold mineralization intensity in Chang'an gold deposit,and summarize the distribution of gold mineralization with Numerical-scale fractal model and Multifractal model,which helps the metallogenic prediction in Chang'an.Through the field observation and the chart data reorganization discovery,all kinds of rocks in changan mining area had undergone varying degrees of alteration.Such as pyritization,arsenopyrite,sericitization,silicification,carbonation and so on.Pyritization occurred mainly in the gap of minerals or the fracture contact zone.The chang'an ore body was controlled by NW trending main fault and multiple groups of WWS and NW fractures developed in the fracture zone.Aa a certain distance away from chang'an main fault,the fault trend and dip Angle were changed,also the tectonic stress changed.The strong mineralization area of gold corresponded to the extension of chang 'an main fault.Statisticing of a large number of perforation data,in order to seek the regularity and characteristics of gold enrichment,all perforations are divided into three grades: strong mineralization perforation,medium mineralization perforation and weak mineralization perforation and combining the numerical-scale model and multifractal model researches come to the following conclusions:(1)with the increases of mineralization,the threshold value increases,the fractal dimension becomes less,the spectral width ?? value is low,and the gold in the strongly mineralized areas is uniformly distributed.(2)Gold mineralization distribution in the mining area is dominated by low value.(3)Going down with the depth of the platform,the ?? value in intensely mineralized area tends to be low,and the gold mineralization area is close to chang 'an main fault,also strongly influenced by water-rock reaction.(4)The fractal dimension has no obvious relation with the thickness of ore body.And the formation of gold is not determined by a single factor.Overview,Chang'an gold deposit was controlled by tectonic-water-rock reaction.The ore-forming fluid rose along the fracture zone and reacted with the surrounding strata.In the part of local extensional structure,it shows the strike change of chang 'an fault,which increased the microcracks on the scale of contact of the veins,format new extensive fluid migration channels,and promoted the water-rock reaction.In the end,the gold was precipitated and more concentrated.