内蒙古白音查干银多金属矿化区地质特征及找矿方向

Geological features and prospecting directions of Bayanchagan silver polymetallic mineralized area in Xi Ujmqin Banner,central-eastern Inner Mongolia

白音查干银多金属矿化区是近两年来在内蒙古中东部找到的一处大型构造-蚀变岩型银-铅-锌矿预查区,大规模找矿勘查和综合性研究工作正在进行中。野外地质调查和钻(坑)探结果表明,在白音查干地区及外围存在有数条长千余米、宽几十米到百余米的银多金属矿化带。钻孔中所见矿化体以厚度大、连续性好和品位高为特征,银含量变化范围为(22.4～2270)×10-6,平均值为502.68×10-6;最高值为3775×10-6;铅为0.46%～5.40%,平均值为0.69%,最高值为6.19%;锌1.34%～18.5%,平均值为2.64%,最高值为32.11%。综合性研究结果表明,海西期中酸性岩浆活动为矿化带的形成提供了动力和物质来源,北北西向构造破碎带为成矿物质的堆积提供了空间条件,二叠系泥质粉砂岩为成矿流体的沉淀起到了圈闭作用。根椐上述成矿理论,结合地质和物化探资料数据,认为在白音查干银多金属矿化区及外围实现更大的找矿突破是完全有可能的。

Located at the northwestern corner of Xi Ujmqin Banner in the central-eastern part of Inner Mongolia, Bayanchagan is a newly-d{scovered silver polymetallic mineralized area. Large-sized mineralizations occur as veins, veinlets, and disseminated and massive blocks within pelitic siltstone and sandy slate of Lower Permian Dashizhai Formation. Up till now, a number of mineralized zones have been identified, varying from several hundred of meters to more than 1000 m in length and from tens of meters to more than 100 m in width. Four drill holes （ZK-3, ZK-5, ZK-8 and ZK-9） were operated along the mineralization zones, among which the ZK- 9 shows the best result. Twenty-one silver polymetallic ore layers have been identified, with a total thickness of 83.27m. In addition, the total thicknesses of ore layers in the ZK-8 hole and ZK-3 hole are 23.79m and 20. 9m, respectively. The silver polymetallic layer consists mainly of massive, stockwork and disseminated-veinlet sulfide ores. Metallic minerals include pyrite, galena, sphalerite, chalcopyrite, argentite and native silver. Gangue minerals are quartz, fluorite, calcite and sericite. The silver contents of these drilling samples range from 22.4 ×10^-6 to 2 270 ×10^-6 with an average of 502.68 ×10^-6（up to 3 375 ×10^-6）, lead from 0.46% to 5.40 % with an average of 0.69 % （up to 6.19 % ） and zinc from 1.34 % to 18.5 %, with an average of 2.64 % （up to 32.11%）. Field observations show that the Hercynian granitoid magma activity, the NNW-trending fractured zone and the carboniferous siltstone played important roles in the formation of these silver polymetallic mineralized zones in Bayanchagan. All these ore-forming materials, dynamic forces and fluids might have been provided by the Hercynian granitoid magma. Moreover, the accumulation conditions of the ore-forming materi- als were provided by the NNW-trending fractured zone, carboniferous siltstone and sandy slate. Recent studies, combined with newly-obtained geochemical and geophysical data, indicate that systematic exploration is likely to result in more new discoveries of silver polymetallic zones in Bayanchagan.