Mafic dikes at Kahel Tabelbala (Daoura, Ougarta Range, south-western Algeria): New insights into the petrology, geochemistry and mantle source characteristics

Abstract

New petrological, geochemical and Sr–Nd isotopic data of the Late Triassic and Early Jurassic Kahel Tabelbala (KT) mafic dikes (south-western Algeria) offer a unique opportunity to examine the nature of their mantle sources and their geodynamic significance. An alkaline potassic Group 1 of basaltic dikes displaying relatively high MgO, TiO2, Cr and Ni, La/YbN 15, coupled with low 87Sr/86Sri 0.7037 and relatively high eNd(t) +3, indicates minor olivine and clinopyroxene fractionation and the existence of a depleted mantle OIB source. Their parental magma was generated from partial melting in the garnet–lherzolite stability field. A tholeiitic Group 2 of doleritic dikes displaying low MgO, Cr and Ni contents, La/YbN 5, positive Ba, Sr and Pb anomalies, the absence of a negative Nb anomaly coupled with moderate 87Sr/86Sri 0.7044 and low eNd(t) 0 (BSElike), indicates a contamination of a mantle-derived magma that experienced crystal fractionation of plagioclase and clinopyroxene. This second group, similar to the low-Ti tholeiitic basalts of the Central Atlantic Magmatic Province (CAMP), was derived from partial melting in the peridotite source within the spinel stability field. Lower Mesozoic continental rifting could have been initiated by a heterogeneous mantle plume that supplied source components beneath Daoura, in the Ougarta Range. C 2017 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved