The Origin and Evolution of DMM-Like Lithospheric Mantle Beneath Continents - Mantle Xenoliths from the Oku Volcanic Group in the Cameroon Volcanic Line, West Africa

Aug 26, 2026

Continental lithospheric mantle sampled by peridotite xenoliths may resemble the source of mid-ocean ridge basalts (MORB), yet whether this resemblance is primary or overprinted by secondary processes remains debated. Age, origin, and thermochemical evolution of fertile continental mantle are constrained using mineral chemistry in spinel-facies lherzolite and websterite xenoliths from the Oku Volcanic Group and in-situ clinopyroxene Sr isotopes, combined with EBSD fabric data. Textures and isotopes distinguish three lherzolite groups and link websterite formation to reactive percolation and later water-driven amphibole crystallization, with formation in the Paleoproterozoic and limited Pan-African overprint.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages25

Reading Time1 h 3 min

AccessFree to download

Abstract

Introduction

Journal of Petrology, 2023, 64, 1–25 [https://doi.org/10.1093/petrology/egad049](https://doi.org/10.1093/petrology/egad049) Advance access publication date 30 June 2023 Original Manuscript The Origin and Evolution of DMM-Like Lithospheric Mantle Beneath Continents: Mantle Xenoliths from the Oku Volcanic Group in the Cameroon Volcanic Line, West Africa Jacek Puziewicz 1 , *, Sonja Aulbach 2 , Mary-Alix Kaczmarek3 , Theodoros Ntaflos4 , Axel Gerdes2 , Hubert Mazurek1 , Anna Kukuła5 , Magdalena Matusiak-Małek1 , Sylvin S. T. Tedonkenfack1 and Małgorzata Ziobro-Mikrut1 1 Faculty of Earth Sciences and Environmental Management, Institute of Geological Sciences, University of Wroclaw, Wroclaw, Poland 2 Goethe University Frankfurt am Main, Institute for Geosciences and Frankfurt Isotope and Element Research Center (FIERCE), Frankfurt, Germany 3 Géosciences Environnement Toulouse (GET), Observatoire Midi-Pyrénées CNRS-CNES-IRD-Université Toulouse III, Toulouse, France 4 Department of Lithospheric Research, University of Vienna, Vienna, Austria 5 Polish Academy of Sciences, Institute of Geological Sciences, Warsaw, Poland *Corresponding author: [E-mail: jacek.puziewicz@uwr.edu.pl](E-mail: jacek.puziewicz@uwr.edu.pl) Abstract The lithospheric mantle as sampled by peridotite xenoliths in some continental settings resembles the source of mid-ocean ridge basalts (MORB). Whether this resemblance is a primary feature or the result of post-formation secondary processes remains controversial. Here, the age, origin and thermochemical evolution of fertile continental mantle are constrained based on the chemical composition of minerals in spinel-facies lherzolite and websterite xenoliths from the Wum maar and Befang cinder cone of the Oku Volcanic Group (Cameroon Volcanic Line, West Africa), combined with in-situ Sr isotope compositions of clinopyroxene and fabric investigation by Electron Backscatter Diffraction (EBSD) . The majority of lherzolites (here assigned to Group I) consist of minerals with fertile composition (olivine Fo89, Al-rich pyroxenes, spinel Cr\# 0 .08–0.10) . Clinopyroxene is LREE-depleted and has depleted 87 Sr/86 Sr (0 .7017– 0.7020). Crystal-preferred orientation determined by EBSD reveals that clinopyroxene, and sporadically both clino-and orthopyroxene, post-date the olivine framework. Subordinate Group II lherzolites also contain secondary clinopyroxene which is LREE-enriched and has higher 87 Sr/86 Sr (0 .7033) . In contrast, the scarce lherzolites of Group III are more refractory: they contain 72–78 vol.% olivine, Alpoor pyroxenes, and spinel with Cr\# 0 .18. Clinopyroxene (87 Sr/86 Sr 0 .7021) is texturally coeval with olivine and orthopyroxene. Few lherzolites contain amphibole (87 Sr/86 Sr 0 .7031) which post-dates the nominally anhydrous minerals. Most of the websterites (Group A) are aluminous (spinel Cr\# 0 .04–0.06) with LREE-depleted clinopyroxene having depleted 87 Sr/86 Sr ratios (0 .7017–0.7020) similar to Group I lherzolites. Chemical characteristics of minerals coupled with the crystal-preferred orientation data suggests that Group Ilherzolites originated in the spinel stability field by reactive intergranular percolation of an incompatible element-depleted MORB-like melt. Group A websterites likely formed as cumulates from that melt. The Group II lherzolites supposedly occur close to lithosphereasthenosphere boundary and record interaction with lavas of the Cameroon Volcanic Line, whereas Group III lherzolites occur in the shallow part of the mantle profile and represent the protolith from which the Group I lherzolites were formed. Local crystallization of amphibole and concomitant recrystallization of the host lherzolite were driven by supply of water in an event post-dating the formation of LREE-depleted rejuvenated rocks. Migration of alkaline melts of the CVL apparently did not significantly affect the mineral and chemical composition of the lithospheric mantle, which allowed

FAQs

What materials and methods are used to study the continental lithospheric mantle beneath continents?

The study uses peridotite xenoliths (spinel-facies lherzolites and websterites) from the Oku Volcanic Group, mineral chemistry, in-situ Sr isotope compositions of clinopyroxene, and EBSD-based crystal-preferred orientation analyses.

How do the authors distinguish different lherzolite groups and what do they imply?

Three groups are defined by fertility, mineral chemistry, and Sr isotope signatures, including whether clinopyroxene is LREE-depleted or LREE-enriched and whether crystallization post-dates olivine. These group differences are used to infer distinct origins and degrees of post-formation modification.

What processes are proposed for the origin and later evolution of the mantle xenoliths?

The Group I lherzolites are suggested to form in the spinel stability field via reactive intergranular percolation of a MORB-like depleted melt, while Group A websterites likely form as cumulates from that melt. Later, water supply drives amphibole crystallization and associated recrystallization.

Aug 26, 2026

Uploaded by Caleb Sterling