The gravimetric method for the study of basic-ultrabasic plutonic complex in the SW Angola: geometry of the intrusions and their relation to metallic mineralization

Congreso realizado en Toledo del 28 de noviembre al 1 de diciembre de 2022.[EN] Angola is worldwide known as being one of the countries with the highest mineral resources, mainly diamonds, iron and gold. In the southwestern area, close to Lola, Quilengues and Lubango cities, distinct outcrops of Palaeoproterozoic (eburnean) igneous rocks, basic-intermediate in composition (gabbros, diorites and quartz-diorites), are found together with scarce ultrabasic (dunites, peridotites and hornblendites) bodies, which presumably contain Ni, Cr, Co and/or Platinum elements. We use gravity data in three selected structures (Quilengues, Cacimbas and Lola), with similar characteristics (diorites and quartz-diorites bodies with some hornblenditic units) with the aim to study the deep geometry and to evaluate the ore potential. Each structure has been studied with a series of gravimetric profiles, ca. 400 m apart and 100 m separation in between stations, achieving 997 gravity stations. We use the new Czech gravimeter Galileo LG1 (this survey serves to implement it during fieldwork). We use differential GPS by setting a base in each of the structures and connecting the GPS with radio connection, thus calculating the coordinates in real time. With this instrumentation and methodology, we achieve accuracies in accordance with the ranges established in this type of campaign. After obtaining the Bouguer anomaly map, residual anomaly maps have been deduced by adjusting a regional trend; they depict some relative maximum in areas where the ultramafic bodies (bearing base metals) draw sparse outcrops, suggesting higher volumes in depth. 2.5D gravimetric models show laccolithic intrusions, about 5 km of mainly dioritic bodies, with some scarce ultramafic rocks up to 3 km depth.Peer reviewe