Gravity signature and physical properties of copper deposit in the Curaca Valley, northern Bahia/Brazil - case study

This paper aims at analysing the application of the gravimetric method in the search for copper ore in the Valley of Curaca River in northern Bahia, Brazil. The area where this study was carried out is known as Angico Farm, one of the claims of Caraiba S.A., a copper producer in the northern Bahia, Brazil. There are 18 drill holes at the Angico Farm target, drilled in order to investigate the mineralizations in depth. We have obtained information such as geographic coordinates and chemical results from the company in order to test the geophysical response and the correlation with geology. A 3D inverse gravimetric model was generated in order to verify the validity of the method in exploring for copper ore associated with hydrothermally altered mafic and ultramafic. Both mafic/ultramafic rocks and copper ore present high density, therefore the gravity method may not be effective for identification. We have shown, however, that copper ore from the Curaca Valley presents a fairly good gravity response, and 3D inverse mathematical model pointed out a well-delimited copper orebody in the regions where drill holes intersect the ore and coincide with the positive gravity anomaly. The ore contents were overlapped on cross-sections of density extracted from the inverse model and such information helped us to check out the consistency of the gravimetric method in mapping and modelling mineralized bodies associated with mineral occurrence. Additionally, magnetic susceptibility and gammaspectrometric data were acquired along 18 drillcores to investigate their possible correlation with orebodies.