Insights Into the Source of Magmatic Hot-Lines: Forty Years of Geophysical Studies of the Cameroon Volcanic Line

Aubreya Adams

doi:10.3389/feart.2022.838993

Abstract

The Cameroon Volcanic Line (CVL) of west Africa poses many challenges to common models of mantle processes and volcanic system genesis. Although the CVL superficially resembles the hot-spot trace of a mantle plume, there is no evidence for age progression of initiation or cessation of volcanic activity, making the CVL one of several hot-lines observed on Earth, which exhibit asynchronous volcanism along each line. This unusual form of volcanic system, together with the complexity of the surrounding geology, which includes a Mesozoic rift, an Archean Craton, a Proterozoic mobile belt, and a major continental-scale shear zone, have fueled numerous geophysical investigations of the crust and upper mantle structure within the region. This review highlights major findings from geophysical studies, including controlled source and passive source seismic studies and gravimetric modeling, conducted in the late 20th and early 21st centuries. Potential geodynamic models for the formation of the CVL are examined and evaluated based on the body of geophysical evidence. Finally, several key outstanding questions about the structure and formation of the CVL are highlighted, potentially guiding future studies of this region.

Highlights

The Cameroon Volcanic Line (CVL) in west Africa is a geologic enigma that challenges many current models for mantle dynamics, tectonics, and volcanism
The linear nature of the CVL has led many studies to describe it as a classic Wilson-Morgan hot spot trail created by a mantle plume, in which a linear chain of age-progressive volcanoes are produced (e.g., Morgan, 1972; Morgan, 1983; Van Houten, 1983; Duncan and Richards, 1991; O’Connor and Le Roex, 1992; Lee et al, 1994; Burke, 2001)
The CVL, displays several firstorder characteristics that fundamentally differ from those that define a hot spot trail, leading other studies to conclude that the CVL is inherently inconsistent with its formation by a mantle plume (e.g., Poudjom Djomani et al, 1995; Reusch et al, 2010; Adams et al, 2015)

Summary

Introduction

The Cameroon Volcanic Line (CVL) in west Africa is a geologic enigma that challenges many current models for mantle dynamics, tectonics, and volcanism. Fundamental patterns in crustal thickness estimates from both gravity-based models are similar to those from seismic imaging, exhibiting thicker crust beneath the Congo Craton and thinner crust, with limited variability in thickness, beneath the southern CVL, the Oubangides Belt, and the Adamawa Plateau (Goussi Ngalamo et al, 2018; Kemgang Ghomsi et al, 2020).

Results

Conclusion