Metallogenic Regularity And Prediction To Gold Deposits In Western Liaoning Province

Western Liaoning District is located in the northern margin of North China plate,which is the intersection position between North China plate and Tianshan-Xingmengorogenic belt. The district experienced several-times tectonic movements fromNeoarchean when initial continental nucleus formed to Yanshanian when tectonicmagmatic highly developed. Meanwhile, the main stress direction changed fromEW-direction in Pre-Yanshanian to NE-direction resulted in Peri-Pacific system. Theprotracted nature and repeatability of tectonic movements resulted in additive andcumulative gold mineralization, which created good geological metallogenic conditonfor Western Liaoning District. A group of gold deposits with regional characteristicsfromed.Using the working and research results of previous researchers’ and combiningthe newest research progress in our project, the paper started comprehensive researchon gold in Western Liaoning District. The research thinking is as follows: research ongeological background of Western Liaoning-monographic researches on geophysicalfield, geochemical field, heavy-sand and remote-sensing of Western Liaoning—researches on typical gold deposits—research on metallogenic regularity in eachmetallogenic unit—research on metallogenic regularity in Western Liaoning—research on gold deposits in Western Liaoning with comprehensive information—delineation to ore-prospecting targets in Western Liaoning. Reserch process andresults are as follows: （1）Preliminary analysis on tectonic units in Western Liaoning: The study areamainly covers two big one-class tectonic units, which are North China plate andTianshan-Xingmeng orogenic belt. On the basis of this, Western Liaoning District isdivided into four-class tectonic units, which mainly include the residual Neoarcheantectonic units, the residual Mesoproterozioc tectonic units, the residual Paleozoictectonic units, the Yanshanian tectonic units（mainly fault basins）, Jurassic tectonicmagmatic units. All the above works lay the theorectical foundation of tectonicsurrounding to the division of metallogenic units.（2）We got a macroscopic grasp on the division of geological bodies in WesternLiaoning after researches on formations, magmatic rocks and metamorphic rocks inthe district. It makes clear to the division of structures related to gold mineralizationafter researches on regional structures. On the basis of this and combining the resultsof previous researchers’, we straightened out the tectonic evolution process in WesternLiaoning.（3）Datas and materials collected in the project, including1/500000gravity,areomagmatic, gold geochemical, heavy sands and remote sensing materials, wereprocessed and analysised. Then, the relevant maps were made. Using materials ofgravity, areomagmatic and remote sensing, structures were interpreted. Using goldgeochemical and heavy sands anomaly, anomaly areas of gold were delineated. All theabove works laid the geochemical foundation for the division of gold metallogenicunits.（4）Considering the distribution characteristics of tectonic units, formations,magmatic rocks and metamorphic rocks comprehensivly, and combining researchresults of geophysical, geochemical, heavy sands and remote sensing, we dividedWestern Liaoning District into6metallogenic units. They are Yebaishou-Jiumiaometallogenic unit in Neoarchean magmatic arc, Jizhou-Fuxin metallogenic unit inNeoarchean metamorphic intrusive rock, Suizhong metallogenic unit in Neoarcheangranite, Kazuo metallogenic unit in Changcheng Period depression basin, Yanshanianfault basin metallogenic unit in center of Western Liaoning, Jianping back-arc basinmetallogenic unit in the southern margin of Tianshan-Xingmeng orogenic belt. （5）Choose found gold deposits which could represent the metallogeniccharacteristics of each unit as typical deposits on the basis of division of metallogenicunits. The following gold deposits were chosen as typical deposits in the abovemetallogenic units:（1-1）Sanshimudi gold deposit；（1-2）Dongwujiazi gold deposit；（1-3）Erdaogou gold deposit；（1-4）Houmeilingao gold deposit；（2-1）Dayingtaogougold deposit；（2-2）Paishanlou gold deposit；（2-3）Shuangyang gold deposit；（3-1）Dashitougou gold deposit；（3-2）Shuiquan gold deposit；（4-1）Baizhangzi golddeposit；（5-1）Hongshilazi gold deposit；（6-1）Huojiadi gold deposit. Some golddeposits were researched the first time.（6）On the basis of research results to typical deposits, gold metallogenicregularity of each unit was researched from the view of gold metallogeniccharateristics, metallogenic epoch, provenance and distribution position. Metallogenicmodel maps of Yebaishou-Jiumiao metallogenic unit in Neoarchean magmatic arc,Jizhou—Fuxin metallogenic unit in Neoarchean metamorphic intrusive rock andSuizhong metallogenic unit in Neoarchean granite were made.（7） Investigate deep reason why two adjacent metallogenic units,Yebaishou-Jiumiao metallogenic unit in Neoarchean magmatic arc and Jizhou-Fuxinmetallogenic unit in Neoarchean metamorphic intrusive rock, have big differences inminerallization from the view of regional tectonic evolution. Divide metallogenic typeof gold deposits in Western Liaoning. Classify gold deposits into two metallogenicseries：gold metallogenic series of metamorphic hydrothermal in Hercynian and goldmetallogenic series of magmatic hydrothermal in Yanshanian. Determine geologicalore-preospecting symbols to each metallogenic unit.（8）In the course of research on comprehensive information to gold deposits inWestern Liaoning, extract geophysical or geochemical forcast factors matching totypical deposits firstly, and then, turn them to factors matching to metallogenic units.Finally, establish comprehensive ore-prospecting model for the above metallogenicunits, which layed the foundation for the delineation of ore-prospecting targets.（9）Begin the whole gold forecasting work to each metallogenic unit in WesterenLiaoning with results got in comprehensive information research, and finally delineate targets. Two forcasting model tools in MRAS are used, and they are ComprehensiveForecasting Model for deposits and Weights of Evidence Model. TakeYebaishou-Jiumiao metallogenic unit in Neoarchean magmatic arc as an example tointroduce how Comprehensive Forecasting Model for deposits was used. TakeJizhou-Fuxin metallogenic unit in Neoarchean metamorphic intrusive rock as anexample to introduce how Weights of Evidence Model was used. Other units areresearched with Weights of Evidence Model because of small difference inclassfication to deposit grade.（10）Considering characteristics of ore-prospecting targets in Western Liaoning,determine unified posterior probability for targets delineation in the whole study area.The probabilities are the follows: P≥0.9，the key investigation zone；0.9＞P≥0.623207，the favorable metallogenic zone；0.623207＞P≥0.376544，the probablemetallogenic zone. As a result, we got4key investigation zones,12favorablemetallogenic zones and13probable metallogenic zones.（11）Besides targets with high posterior probability, such as DongjingziAtargetand Wanshouzhen A target, we should focus on targets with big distance between thenumber of found gold deposit in it up to now and the posterior probability. As a result,T08（Waziyu target） and T09（West of Pingdingshan target） have big probabilityin mineralization.