Aeromagnetic data interpretation for structural architecture modeling in the Boke region, Northwestern Guinea

Abstract

The Boke region, in north‑western Guinea, lies at the Atlantic margin of the West African Craton, where an Archean to Paleoproterozoic basement is largely concealed beneath the Paleozoic sedimentary cover of the Bowe Basin and a thick lateritic mantle. This setting hosts the Fouta Djallon‑Mandingo bauxite province, yet its concealed structure remains poorly documented. To characterize this structure aeromagnetic data were interpreted using an integrated workflow combining reduction to the equator, upward continuation, the analytic signal, the horizontal gradient amplitude, the tilt derivative, the tilt angle of the horizontal gradient (TAHG), and Euler deconvolution. The interpretation resolves three magnetic domains, two positive anomalies (PMA1 and PMA2), attributed to concealed mafic bodies deep Birimian or Archean mafic basement and shallow Mesozoic dolerite intrusions, respectively separated by a broad negative anomaly (NMA1) that corresponds to the weakly magnetic sedimentary fill of the Bowe Basin. Euler deconvolution yields source depths from about 400 m to 9,600 m, the deepest sources forming an arcuate band in the north and the shallowest contacts dissecting the central basin. The magnetic lineaments, classified by length into three orders, define a polyphase fault network in which the most frequent set trends WNW‑ESE to E‑W and reflects an inherited basement fabric, whereas the tectonically most significant set corresponds to the NE‑SW to ENE‑WSW transform system, with subordinate NW‑SE and N‑S structures. The multi‑level analysis reveals a depth‑stratified architecture in which a dense, shallow, brittle fabric passes downward into a few deep, curvilinear structures indicative of ductile shear, interpreted as an inherited Eburnean‑Pan‑African transcurrent framework overprinted by Mesozoic, rift‑related brittle faulting. Beyond refining the tectonic architecture of this segment of the craton margin, the delineated fault and fracture framework particularly the structural intersections provides a structural guide to the fault‑controlled development of the region’s lateritic bauxite.