综合物探方法在坦桑尼亚西嘎山地区金矿勘查中的应用

Application of the geophysics method to the exploration of a mining area on the Siga Hills,Tanzania

坦桑尼亚西嘎山(Siga Hills)地区位于坦桑尼亚西北部苏库马兰德绿岩带东南端,20世纪初在该绿岩带内发现了一系列世界级金矿床,如盖塔(Geita)金矿和布鲁扬葫芦(Bulyanhulu)金矿.由于该地区金矿床多属于绿岩带条带状铁建造型金矿,具有明显的强磁异常特征,因此可以通过航磁及地面高精度磁测来查明目标体的规模和大小,但受磁测方法限制以及大部分金矿体为半隐伏或全隐伏状态,因此无法对靶区内宽度仅为几米或十几米的隐伏含矿构造体进行更细致的研究.本文以西嘎山地区某一隐伏金矿区为研究对象,通过开展地面高精度磁测、岩样物性测量、激电剖面和断面测量等综合物探工作手段,取得了较丰富的异常信息.缩小了找矿靶区;了解了区内金矿体与围岩的物性差异;查明了含矿构造的平面和断面电性特征,并通过钻探工程得到了验证,提交区内(333)+(334)?金金属量9 t,结合区域成矿背景总结规律,为西嘎山地区今后的隐伏金矿区找矿工作提供经验.

The Siga Hills of Tanzania is located at the southeastern end of the Sukumaland Greenstone Belt in the northwestern Tanzania.Many world-class gold deposits,such as the Geita gold deposit and the Bulyanhulu gold deposit,were discovered in the greenstone belt in the early 20th century.Most of the gold deposits in this area belong to banded iron formation type gold deposit,on account of it has obvious characteristics of strong magnetic anomaly,the size of the target can be determined by aeromagnetic and ground high precision magnetic survey.But smaller ore-bearing structures cannot be detected in the region due to the limitations of magnetic measurements and the fact that most gold ore bodies are concealed underground.In this paper,one concealed mining area of the Siga Hills is taken as the research object.Abundant abnormal information is obtained by means of integrated geophysical exploration such as ground high-precision magnetic survey,measurement of magnetic and electrical physical properties of rock samples,the four-pole sounding symmetrical array method of time domain induced polarization section survey and the central gradient array method of time domain induced polarization profiling survey.Through these measurements,the ore-prospecting area in the study area is reduced.The differences physical properties of magnetic and electrical are investigated between the gold ore bodies and surrounding rocks in the area.The characteristic anomalies of the apparent resistivity and the apparent chargeability of concealed orebearing structures in plane space and section space are found out.The measured anomalies were validated by the drilling engineering,more than 9 tons of gold metal(333+334)has been submitted in this area.Combined with the study of regional geological oreforming background,the regularity of geophysical changes rule is summarized to provide experience for the future prospecting work of hidden gold deposits in the Siga Hills area.