Regional speculations about a pyrrhotite-hearing calc-silicate rock from Odivelas dam (Alentejo)

Abstract

A Pyrrhotite-hearing calc-silicate rock from Odivelas dam (Beja igneous complex) is briefly described. A comparision is made with similar lithofacies knoen in Portel and Alvito mining districts, leading to some speculations on a much wider scale. The Cambrian period could represent a sort of trabsition between the two great Cadomian and Hereynian cycles, testifying the end of acredtion between the Ossa-Morena and the Central-Iberian terranes. The Mombeja mafic complex in Beja massif probably represents a Silurian-Devonian oceanic crust that can be correlated with one: it does not seem necessary to postulate a Petite Sole - Cordoue transform fault in order to link Western Europe to Southern Appalaches. The Mombeja-Acebuches ophiolitic complex represents an Early-Middle Paleozoic oceanic lithosphere. A primitive Beja-Aracena-Castilblanco massif is not a bad candidate to the Carboniferous limit between the Ossa-Morena and South-POrtuguese zones: the picture ois obscured by the lack of a global, unified study of the entire massif, wich has been dismembered by many wrench-faults, mainy ENE-WSW.