TIN MINERALIZATION IN PRECAMBRAIN CRYSTALLINE ROCKS OF THE KOLYMA MEDIAN MASSIF

Abstract

Tin-ore deposits are localized in the northeastern USSR within Mesozoic clastic rocks of the Verkhoyansk-Chukotka fold zone and partly within Palezoic carbonate rocks in marginal horst anticlinoria of the Kolyma median massif [1, 2]. The uplifted fault blocks of this massif, composed of Archean and Proterozoic gneisses, amphibolites, marbles and crystalline schists, are traditionally regarded as tin-free areas. That is why the detection of tin mineralization in crystalline rocks here is so suprising. The tin-ore occurrence detected in 1983 crops out among Proerozoic rocks on the right side of the Talyndya River, a right tributary of the Uyandina. The ore bodies are exposed as a series of quartz-carbonate-sulfide veins with cassiterite. The specific features of the Talyndya ore occurrence are the unusual order of mineral formation and the wide extent of stannite in the ore. The cassiterite in cassiterite-sulfide deposits usually is the earliest ore mineral, formed before sulfides and sulfosalts. Data on cassiterite-sulfide relationships show that early sulfide-rich mineralization gradually changed to the oxide variety. Additional aspects of the subject are discussed.