Mineral Chemistry of Wehrlite Xenoliths Hosted in Basalts from the SW of Hosséré Dammougalré (Adamawa Plateau, Cameroon): Thermobarometric Implications
Wehrlite
samples (size: ~4 cm) hosted in basaltic lavas from the SW of Hosséré Dammougalré are
located in the western Adamawa Plateau. Porphyritic
and allotriomorphic texture characterizerespectively
host Basalt and wehrlite xenoliths. The phenocrysts of olivine (Fo68−74),
and Ti-magnetite are scattered in host basalt. Wehrlite xenoliths (~4 cm size)
contain Cr-rich clinopyroxene (diopise-augite), olivine (Fo76−88)
and chromiferous spinel. Equilibrium temperatures calculated from Fe/Mg
exchange reaction for olivine/spinel vary between 944°C and 1102°C. The
wehrlite olivine crystals with low Fo (<90) indicate a re-equilibration of
Fe-Mg in the host basalt at low temperatures. All the analyzed wehrlite
clinopyroxenes have crystallized at high pressures as evidenced by the Alvi and Aliv contents. The studied spinel-bearing
wehrlite xenoliths represent probably the residual portions of the upper
mantle, which are an important source of information about lithospheric
composition and thermal evolution beneath the Adamawa Plateau.
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