Copper and phosphate mineralization in the lower Proterozoic mobile belt of Bakhuis mountains, Upper Nickerie, Western Suriname, Guiana shield

Abstract

Bornite and apatite mineralizations are found in a granulite facies secton of the Trans-Amazonian Central Guiana mobile belt. The copper and phosphate mineralizations are associated with monzonitic to syenitic metavolcanic rocks, which in part occur interbanded with gabbronorite gneiss. The country rocks include banded charnockitic granulites of the basement, granulites and gneisses of a Proterozoic supracrustal cover, and metamorphosed mafic to ultramafic intrusive rocks in basement and cover. Mineralization was located by a geochemical follow-up of coinciding aeromagnetic and electromagnetic anomalies, the latter with considerable in-phase components. The peculiar association of copper and phosphate mineralizations on the West flank of the Bakhuis granulite dome in the Central Guiana mobile belt shows aspects of volcanosedimentary phosphorus and copper accumulations in an intracratonic rift basin. The supracrustal sequence of volcanics, clastic and chemical sediments in the basin was intruded by mafic magmas, which assimilated phosphorus- and copper-rich supracrustal rocks and on crystallization gave rise to copper- and phosphate mineralized mafic-ultramafic rocks. The subsequent mobile belt-style deformation and granulite to amphibolite facies metamorphism of the Central Guiana mobile belt have given rise to copper-mineralized monzonitic-syenitic and clinopyroxene-apatite rocks, representlng a layered sequence of granulite facies metamorphosed cupriferous felsic volcanics and intercalated phoçhatic siliceous carbonate sediments of the supracrustal sequence. The copper- and phosphate mineralizations of this volcano-sedimentary association occur associated with the similarly metamorphosed and deformed copper- and phosphate-mineralized rocks of the mafic plutonic association.