Ti remobilization and sulphide/sulphoarsenide mineralization in amphibolites: effect of granite intrusion (the Karkonosze-Izera Massif, SW Poland)

Abstract

Our studies focus on ore mineralization in a contact-metamorphic aureole, using the Variscan Karkonosze Granite pluton as an example. The Karkonosze intrusion is enveloped by an Early Palaeozoic (about 500 Ma) metamorphic complex of the Izera-Kowary Unit composed of a diverse assemblage of gneisses, granitic gneisses, schists, amphibolites and marbles. The Budniki ore mineralization site was discovered in the early 1950's at the SE margin of the pluton. The uneconomic Ti-oxide/silicate, Fe-Cu-Ni-Co-sulphide-sulphoarsenide, and uranium mineral deposits are hosted within amphibolites which were subjected to regional metamorphism followed by contact metamorphism. The Ti mineralization includes an ilmenite-titanite assemblage that originated from regional-metamorphic transformation of igneous Ti-bearing minerals, such as ilmenite and tschermakite, of the basic protoliths of amphibolites. During subsequent contact metamorphism, ilmenite was decomposed and, afterwards, Al-rich titanite and rutile were formed. The Ti remobilization was coeval with an early stage of superimposed Fe-Cu-Ni-Co-sulphide/sulphoarsenide mineralization (pyrrhotite, pyrite, pentlandite, arsenopyrite, chalcopyrite, sphalerite and Fe-Ni-Co-As-S phases), related to the activity of the Karkonosze Granite hydrothermal system. The ore minerals formed successively within a wide range of temperatures (625-250°C).