Improving Mineral Resource Estimation Using Domaining: A Case Study

The Obuasi Mine gold orebody is structurally controlled exhibiting dextral strike-slip duplex structures with numerous faulting and fissures. Various geologically homogeneous lithological and structural zones are identifiable on the mine. Structurally, straight faults, points of inflection, metavolcanic-caps and fissure junctions do occur. The mineralization is either free milling gold in quartz veins or gold in sulphide ore. Historically, Obuasi resource evaluation was done across heterogeneous zones (domains): free milling gold in quartz veins and gold bearing sulphide zones. This practice did not recognize the different styles of the mineralization in these domains; thereby resulting in unsatisfactory reconciliation between estimated grades and mined grades. This paper presents the study that reviewed the resource estimation methodology taking into account the two important domains (free milling gold in quartz veins and gold bearing sulphide zones). The new model improved reconciliation between estimated and mined grades.