Caractéristiques pétrologiques et géochimiques des roches magmatiques d’El Aouana, NE algérien = Petrological and geochemical characteristics of the magmatic rocks from El Aouana, NE Algeria

Hamlaoui, H., Laouar, R., Bouhlel, S. and Boyce, A. J. (2020) Caractéristiques pétrologiques et géochimiques des roches magmatiques d’El Aouana, NE algérien = Petrological and geochemical characteristics of the magmatic rocks from El Aouana, NE Algeria. Estudios Geológicos, 76(1), e124. (doi: 10.3989/egeol.43391.510)

Abstract

The El Aouana igneous rocks are part of the Miocene magmatic suite that extends from Northern Tunisia to Morocco through the Algerian coast in the Maghrebin chain. These rocks are composed of volcanic (andesites and dacites) and subvolcanic (micodiorites and microgranodiorites) lithologies that intruded both the Cretaceous and Oligo-Miocene nappes, and the Miocene post-nappe sediments. The andesites are composed of plagioclase, amphibole and pyroxene phenocrysts that are set in a microlithic groundmass. The dacites are plagioclase-rich and rare, highly altered ferromagnesian minerals. The microdiorites and microgranodiorites are hornblende-bea- ring rocks with plagioclase, pyroxene and rare biotite phenocrysts that are set in a microcrystalline groundmass. Geochemical observations show that the rocks are calc-alkaline with I-type affinity. They are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) compared to high field strength elements (HFSE) and heavy rare earth elements (HREE). The negative Nb, P and Ti anomalies observed on the multi-element patterns are imprints of magmas originated from subduction zones. Field, petrological and geochemical investi- gations show that the El Aouana Miocene igneous rocks are emplaced in a post-collisionnal setting. These rocks show similarities with the metaluminous, post-collisionnel granitoids of north-eastern Algeria which are thought to have been derived from a metasomatized mantle source as a consequence of ‘slab break-off’ underneath the North African margin.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Boyce, Professor Adrian
• Authors: Hamlaoui, H., Laouar, R., Bouhlel, S., and Boyce, A. J.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Estudios Geológicos
• Publisher: Consejo Superior de Investigaciones Científicas
• ISSN: 0367-0449
• ISSN (Online): 1988-3250
• Published Online: 09 July 2020
• Copyright Holders: Copyright © 2020 CSIC
• First Published: First published in Estudios Geológicos 76(1): e124
• Publisher Policy: Reproduced under a Creative Commons License