RESOLVING THE AERO ELECTROMAGNETIC (AEM) AND AEROMAGNETIC SIGNATURE OF THE BRUNSWICK NO 12 SULPHIDE DEPOSIT FROM ADJACENT FORMATIONAL ANOMALIES

Resumo

The Bathurst Mining Camp (BMC), Canada, hosts 46 volcanogenic-sedimentary massive sulphide deposits (VHMS), including the world-class Brunswick No. 12 deposit. The magnetic signature of this deposit is masked by the magnetic response of a nearby basaltic formation. A reliable 3D model may contribute significantly to a better understanding of the nature of the Brunswick No. 12 deposit at depth and provide an important vector for exploration. Locally abundant pyrrhotite in the deposit generates a strong magnetic anomaly. 3D modeling of the magnetic data using the geological and drill hole data available in the literature as constraints produced a model that could be compared with previously established geological models. This comparison pointed to a very good correlation of the vertical behavior of the 3D model with a previously derived geological section. Although continuous at depth, the model displays differences between the northern and southern portions of the upper region of the body. This “bifurcate” aspect is consistent with the presence of two magnetic anomalies associated with the deposit. Independent geological interpretations of the sulphide body indicate a greater discontinuity of the body in the E-W direction compared to N-S discontinuities in the magnetic model. The magnetic model was then compared with the deposit aero electromagnetic (AEM) signature, which also indicated a bifurcation between the northern and southern portions. The correlation of the interpretation of two geophysical methods based on very different physical properties helps to confirm the reliability of the 3D model obtained. The results of this study contribute to a better characterization of the geophysical signatures associated with the Brunswick No. 12 deposit and help understanding its petrophysical composition. The geophysical characteristics provide a benchmark for comparison with other (partially) masked anomalies in BMC area or elsewhere.