甘肃北山音凹峡地区水系沉积物测量地球化学特征及找矿靶区优选

Geochemical Characteristics of Stream Sediment Survey and Prospecting Target Selection in the Yinwaxia Area,Beishan,Gansu Province

音凹峡地区位于北山南带,是甘肃北山地区重要的成矿带,目前地质工作程度较低。通过对音凹峡地区开展1/5万水系沉积物地球化学测量,初步总结了区域地球化学特征,圈定了地球化学异常,为下一步找矿工作部署和成矿规律研究提供了基础资料。运用多元素富集系数累加化探方法,圈定找矿靶区16个。通过对找矿靶区开展概略检查和重点检查工作,在9个靶区中发现矿化线索。研究结果表明:在工作程度较低地区多元素富集系数累加化探方法可以快速缩小找矿范围,确定找矿目标,有助于提高找矿工作效率。

As an important method of geological prospecting,the geochemical survey focuses on the acquisition,interpretation,and evaluation of geochemical data.At present,the main geochemical measurement methods of mineral prospect surveys include stream sediment survey,soil survey,and rock survey.After obtaining the regional geochemical data,extraction of geological information will be the biggest difficulty for geological prospecting.The conventional geochemical data processing method is relatively mature at present,but its efficacy in delineating abnormal areas and locating concentration centers has been drew back by the huge workload of large-scale geological verification.Using geochemical data reasonably to delineate prospecting target areas has become an important task of current geochemical data processing.Yinwaxia area,located in the southern belt of Beishan,Gansu Province,is an important metallogenic belt in Beishan,Gansu Province,with a low degree of geological work.During the 1∶50000 mineral prospect survey,the stream sediment survey was carried out simultaneously,and the content information of 16 elements such as Au,Ag,Cu,Pb,Zn,W,Sn,Mo,As,Sb,Bi,Cr,Ni,Co,Ba and Hg was obtained.And then through conventional geochemical data processing methods,geochemical anomaly maps and comprehensive anomaly maps were compiled,and 32 comprehensive anomalies were delineated.However,there is an urgent problem to be solved here,that is,the number of anomalous areas is large and the area is also large,which leads to excessive workload and individual anomalies that can’t be verified in the field.In order to further determine the prospecting target area accurately,this paper uses the multi-element enrichment coefficient accumulation method to further process the geochemical data.That is,according to the element enrichment characteristics,the enrichment coefficients of each element in the same sample were accumulated to obtain a new variable-enrichment coefficient accumulation value.The accumulation value of the enrichment coefficient was used to draw the anomaly map and the new prospecting target area will also be re-delineated by the cumulative frequency method to delineate three-level anomalies.The anomaly centers with three-level concentration zones or some large-area secondary concentration zones were selected as prospecting targets(16 in total).In each target area,the enrichment coefficient was utilized to determine the main ore-forming elements.The different exploration approaches were adopted to check the prospecting target area with different main ore-forming elements.Through the verification of the target area,ore(mineralization)points were found in 9 prospecting target areas,and the ore-finding rate was 56.25%.The orefinding rate of the prospecting target area with three-level concentration zoning is 61.54%,which shows very good ore-finding effect.The results show that the enrichment coefficient accumulation can make the delineation of prospecting target area more accurately and efficiently,which remarkably improves the probability of successful prospecting.Therefore,it is instructive in 1∶50000 mineral prospect investigation.