Gravity Data Interpretation in the Northern Edge of the Congo Craton, South-Cameroon

Gravity data in the southern Cameroon are interpreted to better understand the organization of underlying structuresthroughout the northern edge of the Congo craton. The Bouguer anomaly maps of the region are characterized by an elongated trending trending negative gravity anomaly which correspond to a collapsed structure associated with a granitic intrusion beneath the cente center of the region r of the region of the region and limited by fault systems. �e applied 3�D gravity modelling and inversion in order to obtain the 3D density structure of the area. Our result demonstrated that observed gravity anomalies in the region are associated to tectonic structures in the subsurface. The resulting model agrees with the hypothesis of the existence of a major continental collision zone between the Congo Craton and the Pan�African belt. The presence of deep granulites structures in the northern part of the region expresses a continental collision

Interpretação gravimétrica na Borda Norte do Cráton do Congo, Sul de Camarões

Gravity data in the southern Cameroon are interpreted to better understand the organization of underlying structures throughout the northern edge of the Congo craton. The Bouguer anomaly maps of the region are characterized by an elongated SW-NE trending negative gravity anomaly which correspond to a collapsed structure associated with a granitic intrusion beneath the center of the region and limited by fault systems. We applied 3-D gravity modelling and inversion in order to obtain the 3-D density structure of the area. Our result demonstrated that observed gravity anomalies in the region are associated to tectonic structures in the subsurface. The resulting model agrees with the hypothesis of the existence of a major continental collision zone between the Congo Craton and the Pan-African belt. The presence of deep granulites structures in the northern part of the region expresses a continental collision.Um conjunto de dados gravimétricos, provenientes do sul de Camarões, foram interpretados para o melhor entendimento das estruturas em sub superfície na borda norte do Cráton do Congo. Os mapas de anomalia Bouguer desta região foram caracterizados por uma anomalia gravimétrica negativa de direção SW-NE, que corresponde a uma estrutura de colapso associada com uma intrusão granítica, abaixo do centro desta região, e que está limitada por um sistema de falhas. Foram utilizados métodos de modelagem gravimétrica 3 D e inversão, para se obter uma estrutura densa 3-D desta área. Os resultados demonstraram que as anomalias gravimétricas observadas na região estão associadas com estruturas tectônicas em sub superfície. O modelo resultado está em consonância com a hipótese de existência de uma zona de colisão continental principal entre o Cráton do Congo e o Cinturão Pan-Africano. A presença de estruturas granulíticas profundas na borda norte desta área indica uma colisão continental

Identifikacija tektonskih lineamenata korištenjem aeromagnetskih podataka za područje jugoistočnog Kameruna

The subsurface structures in a part of the Congo Craton in south-eastern Cameroon, between the latitudes 2° to 3° N and longitudes 13° to 15° E, has been estimated by the interpretation of aeromagnetic data. Magnetic survey is used to delineate magnetic lineaments, analyze its relationship to the tectonic fabric and to estimate the depth of perturbing body source, probably granitic intrusion along one profile selected on the total magnetic intensity reduced to the equator (TMI–RTE) map by means of forward modelling and inversion constrained by surface geology and results from Euler deconvolution analysis method. Determination of the magnitude maxima of the first vertical derivative (FVD) of the residual field reduce to the equator allowed a map to be produced showing various aeromagnetic lineaments interpreted as the fault system of the studied area. Particularly, looking at the center of the structural map, we find that these structures are associated to long-wavelength anomalies, suggesting that its should be connected with large-scale structural deformation. The pseudo-gravity map shows the extension of the tillitic formations on the geological map. Our results confirms the morphological difference and the tectonical subdivision into two tectonic sectors corresponding to the Congo Craton in the south, Pan-African in the north and also helped identify the tectonic boundary separating them at depth.Pomoću interpretacije aeromagnetskih podataka procijenjene su strukture ispodpovršine tla u dijelu Kongoanskog kratona u jugoistočnom Kamerunu, između zemljopisnih širina 2° i 3° N i dužina 13° i 15° E. Magnetski premjer korišten je za prepoznavanje magnetskih lineamenata duž izabranog profila na karti ukupne jakosti magnetskog polja reduciranog na ekvator (TMI-RTE), za analizu njihova odnosa prema tektonskoj građii za procjenu dubine izvora perturbacija, vjerojatno granitnih intruzija. Korišteno je izravno modeliranje te inverzija ograničena površinskom geologijom i rezultatima dobivenim metodom Eulerove dekonvolucije. Određivanje iznosa maksimuma prve vertikalne derivacije (FVD) rezidualnog polja reduciranog na ekvator omogućilo je izradu karte kojapokazuje različite aeromagnetske oblike interpretirane kao sustav rasjeda u razmatranompodručju. Pobliže, gledajući strukturne karte nalazimo da su ove strukture povezane sdugoperiodičnim anomalijama, sugerirajući da one moraju biti povezane sa strukturnimdeformacijama na velikoj skali. Naši rezultati potvrđuju morfološke razlike i tektonsku potpodjelu u dva tektonska sektora koji se podudaraju s Kongoanskim kratonom na jugu i Pan-afričkim strukturama na sjeveru, te pomažu u identificiranju tektonskih granica koji ih razdvajaju u dubini

Is good policy unimplementable? Reflections on the ethnography of aid policy and practice

Despite the enormous energy devoted to generating the right policy models in development, strangely little attention is given to the relationship between these models and the practices and events that they are expected to generate or legitimize. Focusing on the unfolding activities of a development project over more than ten years as it falls under different policy regimes, this article challenges the assumption that development practice is driven by policy, suggesting that the things that make for ‘good policy ’ — policy which legit-imizes and mobilizes political support — in reality make it rather unimple-mentable within its chosen institutions and regions. But although development practice is driven by a multi-layered complex of relationships and the culture of organizations rather than policy, development actors work hardest of all to maintain coherent representations of their actions as instances of authorized policy, because it is always in their interest to do so. The article places these observations within the wider context of the anthro-pology of development and reflects on the place, method and contribution of development ethnography