Apatite U-Pb geochronology and geochemistry of the Ighir Amellal-Tanna Izem monzogabbro (Moroccan Meseta): Implications for early Variscan magmatism

El Haouiti I, Boutsougame A, Moussaid A, Mezougane H, Vermeesch P, Aassine H, Aissa M, Voudouris P, Keith M, Ouahmad H, Elabouy M, Kouraich A (2027)

Publication Type: Journal article

Publication year: 2027

Journal

Journal of African Earth Sciences

Book Volume: 245

Article Number: 106378

DOI: 10.1016/j.jafrearsci.2026.106378

Abstract

The Ighir Amellal–Tanna Izem area is located in the southwestern part of the Tighza–Jbel Aouam polymetallic district within the Moroccan Central Meseta, a region characterized by significant Variscan magmatism and Pb–Zn–Cu–Sb mineralization. Although numerous studies have focused on the late Variscan granitoids of the district (≈295–280 Ma), the petrogenesis and chronology of earlier magmatic events remain poorly constrained. In this study, we combined whole-rock geochemistry and U–Pb apatite geochronology (LA-ICP-MS) to characterize a mafic dyke exposed in the area. Geochemical data recalculated on a 100% anhydrous basis (correcting for Loss on Ignition, LOI ≈ 10 wt%; SiO2 ≈ 47.02–47.26 wt%, raw 41.59–42.28 wt%; Na2O + K2O ≈ 5.52–5.61 wt%; high Ba and Sr contents) formally classify the intrusion as a metaluminous monzogabbro with a strong alkaline, potassic affinity. Its trace-element signatures display prominent, diagnostic negative Nb and Ti anomalies coupled with a sharp positive Pb anomaly, indicating a geochemical heritage derived from the partial melting of a metasomatized sub-continental lithospheric mantle (SCLM) during lithospheric extension. U–Pb analyses on apatite yielded early Carboniferous ages of 338 ± 25 Ma (representing primary magmatic cooling) and 313 ± 20 Ma (recording a late hydrothermal overprint contemporaneous with the regional mineralizing events). This within-plate signature indicates that this early Variscan magmatism was emplaced during a transitional extensional or transtensional tectonic regime, allowing the ascent of SCLM-derived, alkali-rich mafic melts through deep-seated crustal discontinuities.

Authors with CRIS profile

Manuel Keith Lehrstuhl für Endogene Geodynamik (LEG)

Involved external institutions

Université Sultan Moulay Slimane MA Morocco (MA) Université Moulay Ismail de Meknes MA Morocco (MA) University College London (UCL) GB United Kingdom (GB) National and Kapodistrian University of Athens GR Greece (GR)

How to cite

APA:

El Haouiti, I., Boutsougame, A., Moussaid, A., Mezougane, H., Vermeesch, P., Aassine, H.,... Kouraich, A. (2027). Apatite U-Pb geochronology and geochemistry of the Ighir Amellal-Tanna Izem monzogabbro (Moroccan Meseta): Implications for early Variscan magmatism. Journal of African Earth Sciences, 245. https://doi.org/10.1016/j.jafrearsci.2026.106378

MLA:

El Haouiti, Issmail, et al. "Apatite U-Pb geochronology and geochemistry of the Ighir Amellal-Tanna Izem monzogabbro (Moroccan Meseta): Implications for early Variscan magmatism." Journal of African Earth Sciences 245 (2027).

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