Crustal Structure Beneath the Cameroon Volcanic Line and Surrounding Area: Insights from Markov Chain Monte Carlo and Evolutionary Algorithm Based Shear Wave Velocity Inversion
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geospatialType de record:
paper
Créateur:
SatSim
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Hôte:
The Cameroon Volcanic Line (CVL) and other tectonic features in Cameroon remain enigmatic, prompting ongoing debates about their detailed structure, composition, and geodynamic evolution. To shed light on these complexities, we leverage the ambient noise tomography (ANT) method to invert shear wave velocity (Vs) and image subsurface structures, providing crucial insights into both subsurface geology and deep crustal processes. Specifically, we employed two different methods: Markov chain Monte Carlo (MCMC) and Evolutionary Algorithm (EA) inversions to robustly constrain the Vs velocity structure, Vp/Vs ratio, and density beneath the CVL and its surrounding area.Our results reveal a prominent high-velocity structure at depths of 25 to 35 km, which precisely aligns with the CVL. Within this region, Vs velocities reach up to 4.0 km/s, accompanied by a Vp/Vs ratio ranging between 1.85 and 1.88 and density varying from 2.9 to 3.1 g/cm3. These characteristics suggest the presence of cooled mafic material that has intruded the crust. Our 2D depth cross-sections along the CVL indicate that these cooled mafic intrusions are ubiquitous along the entire volcanic line. However, they are spatially separated from the upper crust's volcano-plutonic structure by a thin intermediate structure exhibiting a Vp/Vs ratio of 1.68 to 1.71 and an average Vs velocity of 3.8 km/s, indicative of felsic to intermediate crust, which may be linked to the Pan-African Orogeny.The high Vp/Vs ratio and Vs velocity structures are found closer to the surface in the recently active volcanic provinces, accompanied by a thinner low Vp/Vs structure. We posit that this thinned low Vp/Vs structure may have facilitated the ascent of mafic material, contributing to recent volcanic activity in the region. Conversely, beneath the Oubanguides belt and Congo craton, these low Vp/Vs structures appear thicker, with mafic intrusions present at depth > 35 km. This observation suggests a dynamic process involving the pushing and exhumation of lower crustal material by the mafic material.Our crustal imaging results hold significant implications for our understanding of the region's geodynamic evolution, suggesting an interaction with deeper structures, may be responsible for the crustal intrusions and volcanism observed along the CVL.
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