The trace and rare earth element contributions to the understanding of Chouichia iron-copper deposits in Northern Tunisia: metal sources interrelated with magmatism and metamorphism

Abstract

The Chouichia ore deposits are one of the most important polymetallic Cu-Fe-rich mineralizations located in the front of the thrust zone of the Tunisian Tellian belt. This mineral occurrence is carried by veins and breccias hosted by the Upper Cretaceous to Oligocene-Lower Miocene sediments in the Fej Et Tamer tectonic corridor. Geochemical work carried out on host rock and mineral samples shows an enrichment and fractionation of REEs with Eu negative anomalies due to interactions of hydrothermal fluids with Eu-depleted magmatic rocks presumably lying in the subsurface. Co/Ni ratios help distinguish three pyrite generations. Pyrite I disseminated in the host rock is sedimentary-syngenetic, formed at low temperature (Co/Ni 1 and confirmed by varying Y/Ho ratios (range 19.625 to 36.5). Trace element amounts normalized to the average contents of trace metals in primitive mantle testify to a metal source from the upper crust and upper mantle with high enrichments of ore bodies in As, Sb, Cu, Pb, Ag, Au, W, and Mo. Marked depletions in Hf, Zr, and Sc indicate their high fractionation degree in both mineralizing and magma fluids and/or igneous rock/fluid interaction effects in the subsurface. Positive anomalies of magmaphile trace element markers such as Mo and W support high-temperature mineralizing fluids driven by magmatism. These geochemical characters easily allow the classification of Chouichia veins as a hydrothermal affiliation deposit type where fluids are imprinted by magmatism and metamorphism. Deep-rooted faults in the Fej Et Tamer tectonic corridor have had an essential role in metal transfer, fluid conveying to the surface, and mineral formation.