Personeelslijst
Jean-Paul Liégeois
Aardwetenschappen
Geodynamica en minerale rijkdommen
Geodynamica en minerale rijkdommen
Beschrijving
Decrée, S., Marignac, C., Liégeois, J.P., Yans, J., Ben Abdallah, R. & Demaiffe, D. 2014. ‘Miocenemagmatic evolution in the Nefza district (Northern Tunisia) and its relationship with the genesis of polymetallic mineralizations’. Lithos. Amsterdam : Elsevier. DOI: http://dx.doi.org/10.1016/j.lithos.2014.02.001. I.F. 3.246.
Article in a scientific Journal / Article in a Journal
The Nefza mining district in Northern Tunisia comprises late Miocene (Serravallian toMessinian)magmatic
rocks belonging to the post-collisional magmatism of the Mediterranean Maghreb margin. They are mainly
made up of Serravallian granodiorite (Oued Belif massif), Tortonian rhyodacites (Oued Belif and Haddada
massifs) and cordierite-bearing rhyodacites (Ain Deflaia massif) in addition to rare Messinian basalts.
They are all characterized by LILE and LREE enrichment and strong enrichment in Pb and W. The Messinian
basalts, which are also enriched in LILE, exhibit transitional characteristics between calc-alkaline and alkaline
basalts.
Geochemical (major and trace elements) and Sr, Nd and Pb isotopic compositions indicate that: (1) granodiorite
is linked to the differentiation of ametaluminous calc-alkaline magma derived froma lithospheric enrichedmantle
source and contaminated by old crustal materials; (2) rhyodacites result from the mixing of the same
metaluminous calc-alkaline magma with variable proportions of melted continental crust. Cordierite-bearing
rhyodacite, characterized by the highest 87Sr/86Sr isotopic ratios, is the magma comprising the highest crustal
contribution in themetaluminous–peraluminous mixing and is close to the old crustal end-member; (3) late basalts,
transitional between the calc-alkaline and alkaline series, originated froman enrichedmantle source at the
lithosphere–asthenosphere boundary.
In the Nefza mining district, magmatic rock emplacement has enhanced hydrothermal fluid circulation,
leading to the deposition of polymetallic mineralizations (belonging to the Iron–Oxide–Copper–Gold
and the sedimentary exhalative class of deposits, among others). Magmatic rocks are also a source for the
formation of lead (and probably other metals) in these deposits, as suggested by their Pb isotopic
compositions.
Magmatic rock emplacement and connectedmineralization events can be related to the Late Mio-Pliocene reactivation
of shear zones and associated lineaments inherited from the Variscan orogeny.