Petrology of amphibolites of northwestern part of the Kansk block (Eastern Sayan)

Amphibolites alongside with gneisses are the most widespread types of rocks of the metamorphic thick layers of the Kansk Block, which is one of the typical granite-greenstone areas of ancient cratons in terms of the set and structure of geological formations, character of magmatism and features of metallogeny. The considered granite-greenstone area includes northwest termination of the Kansk Block (Kirelsky area). The composition of supracrustal amphibolite units of the northwestern part of the Kansk Block is shown and their petrochemical comparison with amphibolites from other areas of the Kansk Block (Idarsky Ridge, Kingash and Kan Rivers) is made in this article. On the basis of geological and geo-chemical properties of the examined amphibolites, in particular, the rare-element composition (Rb, Ba, Sr, Th, U, Zr, Hf, Та, Nb, Y, Cr, Ni, Co, V) and REE range character, the protoliths composition of the volcanogenic-sedimentary rocks is reconstructed. The composition and geo-chemical parameters of the protoliths are comparable with continental-margin volcanogenic sedimentary formations of modern geodynamic settings of the type of ensialic marginal basin - island arc. Two types of mineralization (iron-titanium oxide and sulphite) have been recognised in amphibolites.

Keywords

Authors

References