塞拉利昂Mabonto地区BIF型铁矿航磁异常特征及找矿效果

Mabonto地区位于塞拉利昂苏拉山—坎格瑞丘陵弧形构造带(新太古代绿岩带内),由NNE向NNW向的转折部位,区内盛产BIF型金、铁矿。通过对该区航磁异常特征的分析,负磁异常对应铁矿体的投影位置,负磁异常面积越大、强度越高,对应的条带状铁建造的规模越大。在对区内航磁异常进行筛选的基础上,推测NHC2~NHC6等5处航磁异常具有较好的找矿前景,经过异常查证,发现了Gpafaya、Sokoya、Malump铁矿,探获铁矿石资源量近48亿t。通过多手段综合勘探,并以钻探进行验证发现的Gpafaya、Sokoya铁矿勘查成果为例,探讨航磁异常在绿岩带建造中寻找BIF型铁矿的有效性。

Aeromagnetic anomaly characteristics and prospecting effect of BIF type iron deposit in the Mabonto, Sierra Leone

The Mabonto area is located in the turning point from NNE to NNW in the Sula-Kangrui arc structural belt (Neoproterozoic greenstone belt) of Sierra Leone, where BIF type gold and iron deposits are abundant. Based on the analysis of the characteristics of aeromagnetic anomaly in this area, the negative magnetic anomaly corresponds to the projection position of iron ore body. The larger the scale of BIF type iron deposit is distinguished by the larger the area and strength of negative magnetic anomaly. Based on the screening of aeromagnetic anomalies in the region, it is speculated that five aeromagnetic anomalies of NHC2-NHC6 have good prospecting prospects. After the verification of anomalies, Gpafaya, Sokoya and Malump iron deposit have been found, and nearly 4.8 billion tons of iron deposit resources have been detected. Combined with comprehensive research, the effectiveness of aeromagnetic anomaly in finding BIF type iron deposit in greenstone belt construction is discussed through multi-means comprehensive exploration and the results of Gpafaya and Sokoya iron deposit exploration verified by drilling.