Relating petrogenesis and duration of magmatism with mineralization in the Neves- Corvo VMS deposit (Iberian Pyrite Belt)

Cravinho, André

http://hdl.handle.net/10400.5/100697

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Autores

Cravinho, André

Orientador(es)

Relvas, Jorge

Solá, Rita

Resumo(s)

As other VMS deposits in the Iberian Pyrite Belt, the orebodies that form the giant Neves-Corvo deposit are hosted within a lithostratigraphic sequence dominated by siliciclastic sediments from the Phyllite-Quartzite Group and the Volcano-Sedimentary Complex and show a spatial relationship to felsic volcanism. By combining zircon and monazite petrochronology, quartz and garnet trace elements, whole-rock geochemistry and other geological, geochemical and chronological constraints, this project investigated the petrogenesis of felsic magmatism in the Neves-Corvo area and its relationship to ore-forming processes. Zircon and monazite petrochronology, and quartz and garnet geochemistry show that the felsic volcanism that precedes the formation of the Neves-Corvo massive sulfides comprise high-temperature felsic magmas, generated by the high-temperature (>820 ºC) partial melting of a metasedimentary crustal protolith. The felsic magmas in Neves-Corvo also transported numerous zircon xenocrysts, as recognized in other areas of the IPB. Their ages indicate that these are related to the metasedimentary source (<400 Ma), with a Meguma-like affinity, but also to previous episodic emplacement of medium-high temperature felsic magmas in the upper-crust (ca. 360-390 Ma). This indicates that the upper crustal emplacement and extrusion of high-temperature felsic magmas comprise a key heat source for triggering hydrothermal circulation and the formation of VMS deposits. The reduced S-type nature of felsic magmatism and cassiterite trace-element geochemistry provide unequivocal evidence for a granite-derived magmatic-hydrothermal origin of the tin ores found in this deposit. Furthermore, the Ti-in-zircon crystallization temperatures overlap with the maximum temperatures calculated from zircon saturation models, suggesting these may be useful additional criteria for mineral exploration. The results from this thesis offer new in-depth insights into the nature and petrogenesis of felsic volcanism, the volcanic-plutonic relationship, and the multi-stage and protracted evolution of ore-forming processes in Neves-Corvo, with important implications for the knowledge of the magmatism and metallogeny in the IPB.