Undergoing research dealing with palynostratigraphy and magmatism (physical volcanology and geochemistry) provided new insights to the Portuguese part of the Iberian Pyrite Belt geology. These are particularly relevant for the stratigraphic, magmatic and structural knowledge. The work was concentrated on the Albernoa, Serra Branca and Mina de São Domingos antiforms that belong to the so-called north branch (Oliveira, 1990) and geological comparisons are made with the better understood structures of Pomarão and Neves Corvo mine.
Felsic and mafic volcanic episodes are intercalated in fine terrigenous and volcanogenic sediments. Purple shales, usually used as marker beds for mapping purposes appear having distinct stratigraphic positions and ages in the VSC. The volcanic episodes are restricted to the late Famennian in the north branch, while in the south branch they have younger ages reaching the late Viséan. Dolerites are intrusive at several levels in the stratigraphic sequence of both branches. At a first glance, it seems that the volcanism progressed southward in time, as already suggested by Oliveira, 1990. However, owing to the still scarce existing ages, this conclusion must be seen has preliminary.
In terms of physical volcanism, research was mostly concentrated in the felsic rocks. The Albernoa volcanic sequence consists of rhyodacitic lavas or domes represented by coherent and their autoclastic equivalents, grading upwards to bedded volcanogenic sediments. The age of this volcanism is placed between the early and the late Famennian.
At the Neves Corvo mine region three distinct volcanic facies associations, with intrabasinal and near vent characteristics, constitute the VSC. The pumice-rich facies constitute the V1 felsic volcanic episode of late Famennian age while the rhyolitic coherent and autoclastic facies correspond to the V2 felsic episode of Strunian age. Autoclastic rhyodacitic facies may correspond to the V3 volcanic episode.
The volcanic architecture at Serra Branca is composed of rhyodacitic lavas intercalated with deposits containing abundant pyroclasts and relatively small cryptodomes and partly extrusive cryptodomes. The dates obtained for the enclosing sedimentary facies suggest a similar age for this and the Albernoa volcanic successions.
In the Mina de São Domingos antiform the felsic volcanism has not been studied in detail. Nevertheless indications from one borehole and several outcrops suggest that rhyolitic autoclastic facies and volcaniclastic rocks deposited by gravity flows dominate the sequence. Late Famennian ages have been determined.
The more recent lithogeochemistry results supports a geotectonic setting for the IPB involving extension and not subduction, with apparent arc signatures in mafic rocks being caused by crustal assimilation and apparent arc signatures in felsic rocks being, partially at least, caused by anomalous HFSE systematics. Furthermore, studies into the causes for the anomalously low HFSE contents of felsic rocks has confirmed that they are caused by relatively low temperatures of crustal fusion. Additionally, the temperatures of crustal fusion, indicated by zircon and monazite solubility models, may have exploration implications in this world-class VMS province.
Lithostratigraphic units identified in the studied boreholes and their ages, together with outcrop data confirm that the antiforms of Albernoa and Serra Branca are true tectonic windows where the VSC stratigraphic succession is truncated by overthrust nappes. These were generated during a first NE-SW compressional episode of latest Viséan age, refolded in the same sense in the Upper Carboniferous (late Moscovian). The Mina de São Domingos antiform has the same style of tectonic deformation but shows in detail structural complications which are still under investigation.