The Recognition Of Rock Geochemical Anomalies And Metallogenic Prognosis In Mawudigou Area,Wushan,Gansu Province

Mawudigou area is located in eastern part of the Min-Li gold metallogenic belt in the western Qinling.The tectonic movement in this region is intense while the intrusive rocks are widespread.This area is surrounded by many gold deposits and belongs to the scope of Liba type gold deposit.It has good prospects for gold prospecting.Recognition of rock geochemical anomalies and metallogenic prognosis in Mawudigou area is of important theoretical and practical significance to find the gold deposit.The study area is located in the North subbelt of middle Qinling belt in the western Qinling orogenic belt,and it is close to the intermediate-acid intrusive rocks which formed in the Indosinian-Yanshanian.The major strata in this area include the Hejiadian formation and the Heigou formation which belong to the Middle Devonian Shujiaba Group.Based on the 1:10000 geological mapping and 1:2000 rock geochemical surveys in the study area,combined with the previous data and much interior work,the paper studied the metallogenic geological conditions and geochemical characteristics in this region systematically.Faults and folds developed well in the region.There are three major faults(F1,F2,F3)being identified in the study area,together with many inter-layer fracture zones and small folds.Rocks in the region were suffered regional low metamorphism.The alteration types mainly include sericite,pyrite,limonite and carbonation.Metallogenic geological characteristics are similar to that of the Liba type gold deposit and the study area has a good prospect to find gold deposits.The geochemical exploration work area in this article includes two parts:No.? and No.?geochemical exploration area.The amount of geochemical samples is 1038,with the analyzed elements comprising Au,Ag,Bi,Cu,As,Hg,Pb,Sb,Zn.The elements combination features of the study area is similar to the typical Liba type gold deposit such as Liba,Mawu and Zhuzigou goldmine.The No.? and No.? exploration areas are located in two different parts of the study area.They located in different strata.Besides,their geological and geochemical characteristics are significantly different.So a unified method is not a good choice to delineate geochemical anomalies.According to the actual situation of the two exploration areas,we used fractal concentration-area method and trend analysis method to delineate single element anomalies.Based on the grouping of 9 elements,we superposed single element anomalies or use the factor score method to delineate comprehensive anomaly.Then combined with metallogenic geological features,we explained the reasons of anomalies.The results show that the most promising mineralization anomalies are No.1-2 Au-As-Sb-Bi-Cu comprehensive anomaly in the No.?exploration area and the No.?-1 and No.II-2 Au-As-Bi comprehensive anomalies in the northern and northwest part of No.? exploration area.According to geological characteristics and the result of geochemical anomalies identification and interpretation,we made metallogenic prediction and delineated 3 prospecting target areas.They are No.1 target area in No.I geochemical exploration area;No.2 and No.3 target area in No.II geochemical exploration area,respectively.It is possible to find a small or medium Liba type gold deposit if further work on these areas will be made.