Emplacement of the Zindeng phonolitic lava flow (West-Cameroon) in the Cameroon volcanic line: Constraints from the anisotropy of magnetic susceptibility (AMS)

Abstract

The Zindeng phonolitic flow forms a NW-SE elongated body located on the SE flank of Mount Bambouto (West-Cameroon), along the Cameroon Volcanic Line. It covers basalt emplaced on top of the Dschang biotite megacrystic granite. The magnitude of the magnetic susceptibility (Km) in the phonolitic lava flow varies between 196 μSI and 15769 μSI, indicating a dominantly ferromagnetic sensus lato behavior (Km > 1000 μSI; 89% of the stations) due to the presence of pseudo-single to multi-domain magnetite grains as deduced from hysteresis data. The low values of the degree of magnetic anisotropy, the dominantly oblate shape of the AMS ellipsoids and the concordance between lava plane and magnetic foliation point to flow-related magnetic fabrics. The pattern of the magnetic foliations and lineations indicate that the SE part of the phonolite was emplaced as a dome, whereas the NW part corresponds to a flow domain sensus stricto. It is suggested that the viscous phonolitic magma rose from a feeding conduit below the southeastern part of the lava flow and propagated laterally towards the NW.