青海省小圆山铁多金属矿区矿床地质特征及找矿方向

摘要

小圆山铁多金属矿区位于青海省重要的铁多金属成矿带——祁漫塔格蛇绿岩混杂岩带内.该区铁多金属矿勘查已圈定了多处与铁多金属矿化关系密切的磁异常,显示出该地区具有较强的成矿潜力.分析了区域成矿地质背景及矿区地质特征,并讨论了矿床地质特征及控矿因素,研究表明:①小圆山地区金水口岩群白沙河岩组(Pt1b)富含W、Sn、Cu等成矿元素,奥陶系—志留系滩间山群等地层中存在碳酸盐岩,为小圆山铁多金属矿床赋存提供了有利的围岩条件;②区内发现磁异常17处,总体呈NWW向分布,显示出构造对矿床的控制作用;③区内铁多金属矿床多分布于中—酸性侵入岩与围岩的接触带,晚华力西期—印支期及燕山期侵入岩岩体控制了造山型矿床的分布,区内铁矿体厚度0.90 ～5.91 m,TFe品位21.85％～44.34％,铅锌矿化体厚度0.10～5.45 m,Zn品位0.79％～13.60％,Pb品位0.63％ ～6.88％,具有较好的找矿前景;④小圆山铁多金属矿床成因为典型的与酸性岩浆有关的矽卡岩型矿床,受控于特定的碳酸盐岩容矿岩石、断裂构造部位和岩浆热液活动.在上述分析的基础上,进一步分析认为:地磁异常区和水系沉积物元素异常叠合区,奥陶系一志留系滩间山群、石炭系石拐子组,大断裂及其附近破碎带、岩浆岩侵入带等构造部位为矿区重要的找矿部位,值得进一步开展工作.%Xiaoyuanshan Fe-polymetallic mining area is located in the Qimantage ophiolite melange belt,which is one of the important Fe-polymetallic metallogenic belts in Qinghai Province.Many magnetic anomalies closely related to Fe-polymetallic mineralization are delineated in the mining area by conducting geological investigation work of Fe-polymetallic deposit,it is show that the metallogenic potential of the mining area is good.Based on the analysis of regional metallogenic geological background and geological characteristics of the mining area,the deposit geological characteristics and ore-controlling factors are discussed in depth.The study results show that:①the main surrounding rock formations are favorable for the formation of Fepolymetallic mineralization,the metallogenic elements of W,Sn and Cu are enriched in Baishahe Rock Formation (Pt1b) of Jinshuikou Rock Group,carbonate rocks is hosted in stratum rocks (such as Tanjianshan Group) of Ordovician-Silurian,so the favorable surrounding rock conditions of Fe-polymetallic occurrence in Xiaoyuanshan mining area is provided;②17 magnetic anomalies with the mainly NWW-direction in the mining area are delineated,which show that the geological structure is one of the main ore-controlling factors of the metallogenic of Xiaoyuanshan Fe-polymetallic deposit;③the Fe-polymetallic deposits are mainly distributed in the contact belts of intermediate-acidic intrusive rocks and surrounding rocks,the distribution of orogenic type deposit is controlled by the intrusive rock bodies of the Late Variscan and Indosinian-Yanshanian,thickness of the Fe orebodies is 0.90 ～5.91 m,the TFe grade is 21.85％ ～44.34％,thickness of the Pb-Zn mineralized bodies is 0.10 ～ 5.45 m,the grade of Zn is 0.79％ ～ 13.60％,the grade of Pb is 0.63％ ～ 6.88％,which show that the prospecting potential in the mining area is good;④genesis of Xiaoyuanshan Fe-polymetallic is the typical skarn type deposit closely related to acidic magma,and it is controlled by the specific carbonate ore-hosed rocks,fracture tectonic position and magmatic hydrothermal activities.Based on the above analysis results,the prospecting potential of the mining area is studied,the results show that the superimposed area of magnetic anomalies and stream sediments elements anomalies,Tanjianshan Formation of Ordovician-Silurian and the Shiguaizi Formation of Carboniferous,and the tectonic positions such as the large faults and its adjacent fracture belts,magmatic intrusion belt are the favorable prospecting areas of Xiaoyuanshan mining area.