New chronostratigraphic constraints on the emplacement of Miocene high-K calc-alkaline igneous rocks from West Edough-Cap de Fer, NE Algeria

Miocene K-rich calc-alkaline magmatic rocks are exposed over a 150km(2) area in Cap de Fer and West Edough, along the NE Algerian Mediterranean coast. They include andesitic pyroclastic and lava flows, small dioritic plutons, and large microgranodioritic intrusions that intrude and/or overlie Miocene sediments. New K-40-Ar-40 ages obtained on the igneous rocks range from 16.84 +/- 0.58 to 12.91 +/- 0.31Ma and define three successive magmatic pulses at 16.5, 15, and 13Ma. These data are in good agreement with biostratigraphic data obtained on the Miocene marls that yielded Langhian (N8 biozone) to Late Langhian-Serravallian ages (N9-N10 biozones). This consistency suggests that the time span (3.5m.y.) deduced from K-Ar datings is not due to perturbations of the K-Ar clock; it is more likely related to long-lasting tectono-magmatic processes. According to the regional context (no-slab area), these processes result from the uprise of hot asthenospheric mantle through the tear generated by the detachment of the oceanic part of the African slab beneath the Algerian margin that triggered the partial melting of the overlying metasomatized lithospheric mantle of the Kabylides.