ХРОМШПИНЕЛИДЫ В УЛЬТРАМАФИТАХ, РУДАХ И НАДРУДНЫХ ОТЛОЖЕНИЯХ ИШКИНИНСКОГО КОБАЛЬТ-МЕДНОКОЛЧЕДАННОГО МЕСТОРОЖДЕНИЯ (ЮЖНЫЙ УРАЛ)

Abstract

The paper analyzes spatial distribution, morphology and composition of chromites occurring in massive sulfide ores, host rocks and overlapping sediments of Ishkininskoye massive sulfide ore deposit. The analysis has revealed distinct similarity in distribution and composition of chromites from ultramafic rocks and ores, that means the residual nature of chromites in sulfide ores and confirms conclusion about their metasomatic origin. Compositions of chromites in serpentinites vary from medium up to the high chromium ones, with insignificant variations of Mg and Fe2+ contents. 100Cr/(Cr + Al) ratio (Cr#) changes there from 69.31 to 81.52 %, and 100Mg/(Mg + ¥e2+) ratio (Mg#) keeps within limits 41.03-64.56 %. In the whole, there is a Cr-Al trend in their composition changing - trend typical for the alpine-type ultramafic chromites, while chromites in massive sulfide ores are characterized by the wider variation of Mg# (30.08-45.62 %) with minimum Cr# changing (49.71-52.01 %). It was also revealed mat compositions of chromites from overlapping sediments of Baymak-Buribaisky and Ishkininsky complexes correspond mostly to chromites from ultramafic rocks and ores. The Cr# values of the Baymak-Buribaisky complex chromites are 59.29-75.12 % and Mg# 41.24-65.25 %, whereas in Ishkininsky complexe they have Cr# 60.28-82.90 % and Mg# 58.29-62.65 %, respectively. It testifies that the sources of chromites were the domestic rocks and sulfide ores formed before volcanic rocks of Baymak-Buribaisky complex.