Типоморфизм хромшпинелидов из голоценовых псефитов Кыввожского золотороссыпного поля (Вольско-Вымская гряда, Средний Тиман)

Abstract

The results of the study of accessory chrome spinels from heavy mineral concentrates of gold-bearing psephites of the Kyvvozhsky gold-placer field (Volsko-Vymskaya ridge, Middle Timan) are presented. As a result of the study of the typochemistry of chromspinelides, their genetic relationship with rocks of mainly alkaline-ultrabasic composition — analogues of Timanian Late-Riphean-Vendian ultramafites and Early-Middle Devonian alnoites is substantiated. The formation of magmatic sources of chrome spinels occurred in a wide range of geotectonic settings — from passive (platform) to active (island-arc subduction zones), which are more characteristic of the bulk of chrome spinels. The crystallization of chrome spinels, found as microinclusions in lherzolite pyropes in the same shlich samples of the Kyvvozhskaya gold-bearing area, is associated with the conditions of rift zones (spreading of the seabed). We made a conclusion about probable local (intra-valley) position of main magmatic sources of chrome spinels. The revealed chrome spinels, containing microinclusions of nickel and copper sulfides, are considered by the authors as indicators of igneous rocks containing platinum group minerals.