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- 3D Magnetic Inversion in Angola: Serra da Neve Alkaline Complex and Jamba Itabirites case studiesPublication . Machadinho, Ana; Represas, Patricia; Alves, Daniela; Cordeiro, Domingos; Carvalho, João; Lopes, R.; Caessa, Paulo; Pereira, L. F; Osório, A.ABSTRACT: Demanding and speculative economies make it imperative to search for new areas of mineral exploration. Angola’s geological diversity presents an enormous potential for mineral resources. This potential can be assessed by applying different methods, such as geophysical prospecting, to discover new potential targets of areas to explore. For many years, the magnetic method has been successfully used in mineral exploration. In this work we apply a 3D magnetic inversion technique to aeromagnetic data in two different study areas. The Serra da Neve alkaline complex (SNAC) represents a potential source for rare earth elements (REE) and the Jamba itabirites provides metallic mineral deposits with iron and gold mineralizations. In both case studies, whether concerning alkaline intrusions or itabirites deposits, their magnetic properties are characterized by strong magnetic anomalies clearly delineated on magnetic anomaly maps. The high magnetic susceptibility (k) contrast between these target structures and the host rocks allowed us to obtain a coherent three-dimensional geometry for the SNAC structures and the itabirites deposits. The magnetic inversion technique also provided magnetic vector inversion (MVI)susceptibility values estimation for constituent lithologies, as well as the shape and size of the studied structures and deposits. The results demonstrate the effectiveness of the magnetic method for the detection and characterization of target areas, offering an innovative technique to identify potential areas in mineral resources exploration.
- Preliminary Ornamental Classification of Biotitic Granites from Cubal (SW of Angola)Publication . Lisboa, Jose; Caessa, Paulo; Lopes, R.; Oliveira, Álvaro; Silva, Paulo Bravo; Fernández, J.; Rodrigues, José Feliciano; Manuel, JoséABSTRACT: In the Cubal region between Benguela and Huambo (SW of Angola), grey biotite granites of middle Paleoproterozoic age occur on a planation surface as residual reliefs, either of inselberg or inselgbirge type. The objective of this work is to carry out the preliminary classification of the grey granites of the Cubal region (SW of Angola), ranking the areas in relation to their potential in granites as ornamental rocks. Six granite lithotypes were identified, which can be grouped into 3 sets according to their textural characteristics. The petrographic analysis reveals that from a mineralogical point of view, granitic lithotypes are very similar with a significant content of plagioclase. The samples chemical analysis shows a homogeneous acidic composition in the granite composition range. Tests were carried out to determine real and apparent density, total and open porosity, water absorption at atmospheric pressure, compressive strength, and bending strength. The results show that the Cubal granites have the characteristics of quality ornamental stones, which in general can be used in all types of applications, in interior and exterior environments. Based on a set of variables, an empirical classification of the ornamental potential of the granites was made, where 4 levels of increasing potential in the study area are established.