ASSOCIATION OF NATIVE LEAD AND ANTIMONY WITH PLATINUM METALS IN PLACER COMPLEXES OF THE CENTRAL ALDAN

Abstract

We found natural lead-antimony alloys with very little or no tin, in heavy mineral concentrates from the Yukhotochka and the Tayezhka Creeks in the southeastern part of the Yukhta fault zone, central Aldan. The streams here drain the Malaya Yukhta volcanic field, which includes dikes, sills and small stocks of alkalic and alkaline-earth rocks, intruding Lower Cambrian limestones and Jurassic sandstones. This area is devoid of plutons of the dunite-periodotite association, although there are wide-spread alkalic, mafic and ultramafic dikes and stocks of the leucitite-alkalic syenite association. Rocks of the same bodies within the Malaya Yukhta volcanic field belong to the lamproite series. The natural origin of the native lead and antimony found by us is unequivocally indicated by their intergrowths with rock-forming silicates and by the composition of minerals trapped within them as inclusions. Platinum metals are also present, represented by isoferroplatinum, iridosmine, native iridium and sulfides like erlichmanite and laurite.