Formation environment of whiteschists from the Ti-N-Eggoleh region (Serouenout terrane, Central Hoggar): Petrographic, Mineralogical study and Estimation of P-T conditions

A. Bitam-Derridj, Z. Adjerid, K. Ouzegane


Coarse-grained whiteschists (talc-kyanite rocks), containing the high-pressure environment talc-kyanite-quartz ± phengite assemblage (~ 20 kbar and 600°C) are abundant in the Ti-N-Eggoleh region.

Texturally these whiteschists show breakdown of talc + kyanite + quartz to cordierite in silica-rich samples during decreasing pressure (~ 10 kbar and ~ 700°C), whereas kyanite + talc react to allow the growth of cordierite-sapphirine symplectites with increasing temperature (8-10 kbar and ~ 800°C), or cordierite + corundum in silica-poor microdomains during the cooling stage (~ 600°C).

The metamorphic evolution of these M(F)ASH rocks are consistent with the closure of an oceanic basin that likely occurred during the Pan-African orogeny that developed during the assembly of the supercontinent Gondwana between 750 and 500 Ma.

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