Petrology of spinel lherzolite xenoliths from Youkou volcano, Adamawa Massif, Cameroon Volcanic Line: mineralogical and geochemical fingerprints of sub-rift mantle processes

Mantle metasomatic influence on water contents in continental lithosphere: New constraints from garnet pyroxenite xenoliths (France & Cameroon volcanic provinces)

“…In conclusion, FMC pyroxenites were metasomatized by a carbonatitic agent (Wittig et al, 2007;Gu et al, 2018) and AVP pyroxenites by a hydrous silicate one (Njombie et al, 2018). These interactions modified their major and trace element compositions and the carbonatitic melt likely dehydrated the FMC pyroxenites, seemingly from a specific structural site, resulting in their unusual spectral signatures.…”

“…The Cameroon lithospheric mantle, especially beneath the AVP, experienced metasomatism during the early break-up of Pangea around 200 Ma, which accounts for the incompatible element enrichments in related peridotites (Lee et al, 1996;Temdjim et al, 2004;Njombie et al, 2018). The studied AVP pyroxenites are similarly enriched in LREEs, U, and Th relative to MREEs and other incompatible trace elements, and therefore also experienced metasomatism (France et al, 2015).…”

“…11b). The whole-rock enrichments in LREEs relative to MREEs in these samples might be related to the widespread metasomatic stage that affected the Cameroon lithospheric domain (Lee et al, 1996;Temdjim et al, 2004;France et al, 2015;Njombie et al, 2018).…”

“…The studied AVP pyroxenites are similarly enriched in LREEs, U, and Th relative to MREEs and other incompatible trace elements, and therefore also experienced metasomatism (France et al, 2015). Two types of mantle-melt interactions are recorded in lherzolites from the AVP: (i) cryptic metasomatism and trace element enrichments are attributed to a regional mantle plume and the percolation of hydrous silicate melts, whereas (ii) enrichments in CaO relative to Al 2 O 3 during refertilization are attributed to the percolation of carbonatite or carbonated silicate melts (Njombie et al, 2018).…”

Petrography and Geochemistry of the Harzburgite Xenoliths of Lake Guinnadji and Ngao Djalsoka Volcano from the Dibi Area (Adamawa Plateau - Cameroon)

“…Geophysical studies carried out on the Adamawa plateau have shown that Pan African faults have cut the crust down to the mantle [2,3] and thus have served as natural passage for the magma to reach the surface [1], probably after the mantle melting through adiabatic decompression process [4]. Adamawa uprising could have break up the crust-mantle equilibrium system [5], leading to the evolution of the subcontinental mantle with the modification of its nature, structure and composition [6, 7,5]. This evolution is ascertained by previous studies on mantle materials brought to the surface by Mio-Pliocene basaltic lavas flows, which have shown that the nature of subcontinental mantle beneath the Adamawa plateau seems rather complex [8,6,7] due to it heterogeneous composition, not yet cleared up.…”