NATIVE MANGANESE SILICIDE IN ALLUVIAL CONCENTRATES OF THE CENTRAL ALDAN REGION

Abstract

We investigated alluvial deposits generated by the Tayezhka Brook as well as the Malaya and Bol'shaya Yukhta Brooks. The deposits lie in zones of strongly eroded igneous rock represented by sills of alkalic and alkaline-earth syenite, eruptive breccias, as well as by series of alkalic gabbro and ultramafite dikes. The heavy fraction of the deposits contains pyroxene, amphibole, olivine, garnet, magnetite, chromite, ilmenite, sulfide, native lead, lead-antimony alloys, copper, platinum-group metals, gold, and metallic manganese. Our data are still insufficient to allow a confident identification of the bed-rock sources of the compounds. Gold-bearing skarns and hydrothermal quartz-polysulfide ores do occur in the area, as do alkalic-ultramafite complexes, in which platinum-group metals and lead-antimony alloys with platinum-group inclusions have been found. But natural manganese alloys are found in the alluvium only in association with platinum-group minerals and are never found with gold alone. This fact, together with the high quenching temperature, suggests that the minerals originated in an alkalic-ultramafic igneous complex.