甘南地区加甘滩金矿床主矿体特征及其与区域典型矿床对比分析

Characteristics of Main Orebody of Jiagantan Gold Deposit and Comparative Analysis with Regional Typical Gold Deposit in Gannan Area

甘南地区是甘肃省重要的金矿集中分布区,经过30多年的地质勘查,分别形成了以早子沟、加甘滩、以地南等金矿床为代表的夏河—合作金矿富集区和以大水、辛曲等金矿床为代表的忠曲—大水金矿富集区。采用典型矿床解剖和金矿富集区区域类比的方法,通过系统总结加甘滩特大型金矿床主矿体特征,并对比分析2个金矿富集区勘查程度达到详查或勘探的5个大中型典型金矿床主矿体特征及其控矿因素,以期为甘南地区大中型金矿床地质研究提供范例。加甘滩金矿床主矿体规模以中型为主,金平均品位为2.20×10^(-6)~3.77×10^(-6),查明金资源量占矿区总资源量的57.27%;对比可知,5个金矿床的矿带规模大,其长度大于1000 m,控制斜深大于400 m,主矿体数量占矿区全部矿体数量的1.98%~7.14%,除加甘滩金矿之外,其余矿床查明金资源量占矿区总资源量的75%~79%,单个主矿体资源量大于1.5 t,且特大型、大型和中型金矿床分别圈出大型、中型和小型资源量规模的主矿体;夏河—合作矿集区主矿体规模为大中型,金平均品位小于3.5×10^(-6),忠曲—大水矿集区主矿体规模为中型,金平均品位大于5×10^(-6),即后者矿体规模相对较小但品位较富。研究表明:2个金矿富集区主矿体的控矿因素主要为断裂和中酸性岩脉。研究认为加甘滩金矿仍具有很大的勘查空间和找矿前景,若加大矿区近外围及深部探矿力度,有望大幅提升矿区金资源量。

Gannan area is an important gold concentration distribution area in Gansu Province.Through more than 30 years of gold prospecting and large-scale exploration since the 1990s,three super-large gold deposits with gold resources of 100 t have been investigated or explored in detail,including Dashui gold deposit in Maqu County,Zaozigou gold deposit in Hezuo City and Jiagantan gold deposit in Xiahe County.Among them,Jiagantan gold deposit has identified 153 t of gold resources.The gold deposits in Gannan area have the cha-racteristics of agglomeration distribution,forming two basically mature gold enrichment areas,namely Xiahe-Hezuo gold enrichment area in the northwest of Gannan area,and Zhongqu-Dashui gold enrichment area in the southwest of Gannan area.The exploration and research degree of Jiagantan gold deposit,Zaozigou gold deposit and Dashui gold deposit in Gannan area are relatively high.In the past,comparative analysis on characteristics of main orebodies of different degrees have been carried out,which provided a good basis for the study of main orebodies of Jiagantan gold deposit and its gold enrichment area.Based on the brief introduction of the distribution characteristics of gold deposits in two gold enrichment areas and the geological characteristics of Jiagantan gold deposit in Gannan area,the characteristics of main orebody of Jiagantan gold deposit were systematically summarized from the aspects of the spatial distribution,scale,shape,grade and resource distribution of the main orebody.Jiagantan gold belt is more than 1500 m in length and 300~500 m in width.The 17 main ore bodies are roughly parallel distributed in echelon shape,530~1480 m in length and 200~350 m in control slope depth.The scale of the main orebody is mainly medium-sized,and the resources of single main orebody are 1.8~12.7 t,and the scale of resources are mainly small,accounting for 2.04%~14.42%of the identified resources in the mining area.It provides an example for the study of the main orebodies of the superlarge gold deposits.The main ore-controlling factors and main orebody characteristics of five large and mediumsized typical gold deposits in the two gold enrichment areas were compared and analyzed from four aspects of ore-bearing strata,ore-controlling faults,the relationship between intermediate-acidic dikes and gold mineralization,and surrounding rock alteration.It is considered that the main ore-controlling factors are fault structure and intermediate-acid dikes dominated by quartz diorite(porphyrite)dike and granodiorite(porphyrite)dike.Through the comparative study of the main orebodies characteristics of five typical gold deposits,it is considered that compared with the other four gold deposits in the two enrichment areas,the main orebody of Jiagantan gold deposit is larger,but the average grade is 2.70×10^(-6),the proportion of 57.27%of the main orebody is lower than that of 75.34%~79.37%of other deposits.The above understanding further deepens the study of main orebody characteristics of Jiagantan gold deposit and its regional typical gold deposits,and provides an example for the comparative study of the characteristics of the main orebody in gold enrichment areas.The exploration depth of Jiagantan gold deposit is generally shallow and the exploration degree is generally low,the main orebody resource proportion is not more than 75%of the average of Gannan area.The single main orebody resources have not been a large scale orebody,the ore belt and the main orebody group has not yet been fully controlled,and the main orebody of deep stability to extension.It edicates that Jiagantan gold deposit still has great exploration space and prospecting prospect.If the near peripheral and deep prospecting is increased,the scale of the deposit and the amount of gold resources in the mining area will be greatly increased.