Geochemistry of the Central Atlantic Magmatic Province (CAMP) in south-western Algeria

Abstract

In south-western Algeria, dolerite sills and dykes and scarce basalt lava flows occur in the Tindouf, Reggane, Hank basins and Bechar area, and are part of the large Central Atlantic Magmatic Province (CAMP). They represent the north-easternmost witnesses of this province into the African continent. Here, we report the first geochemical data (major, trace and rare-earth elements) for those rocks. Petrographical and chemical compositions of the studied dolerites and basalts are homogeneous and characteristic of continental tholeiites. They are moderately evolved (Mg# 0.66–0.42) quartz-normative low-Ti tholeiites (TiO 2 = 0.86–1.55 wt.%), displaying slight yet variable enrichment in LILE and LREE [(La/Yb) N = 2.18–5.51] and a negative Nb anomaly. Trace element modelling can reproduce the observed variations by non-modal batch melting of a slightly enriched source via various degrees (4–15%) of melting. A similar evolution is displayed by the neighbouring lava flows from Morocco and Ksour Mountains (North Algeria) and by the dyke swarm from Taoudenni (Mali), arguing for a common source presumed to reside within the sub-continental lithospheric mantle. The magmas were probably generated in response to mantle global warming underneath the Pangea supercontinent, and to edge-driven convection between the thick Reguibat craton and adjacent Pan-African mobile belts.