Selenium minerals in gold-bearing veins of the North Urals

Abstract

148Selenium referred to as a scattered element com monly is included in different minerals as an admix ture. It is also occasionally observed in native form or as selenides and oxides [1]. Elevated selenium con tents are noted for copper, copper-nickel, lead-zinc, silver, and uranium ores. Selenium minerals proper are rather rare in occurrence, and thus, these selenium findings are of special interest. Some Ural, largely South Ural gold and polymetallic deposits, contain wittite, clausthalite, palladseite, kawazulite, eucairite, ferroselite, Se bearing galena, and selenium sulfur [2]. When studying the gold bearing quartz veins in one of the ore occurrences in the North Urals, we identified a number of new micromineral selenium phases closely associated with tellurium and bismuth minerals.The Kozhym'yu gold-sulfide-quartz occurrence containing selenides is located in the western part of the Man' Khambo Anticlinorium within the Central Ural Uplift, in the watershed of the Kozhym'yu River and Upper Kozhymvozh Creek. The region comprises the Late Riphean-Early Vendian stratified volcanic and sedimentary-volcanic rocks of the lower and upper subformations of the Sablegorsk Formation and Vendian-Cambrian Arian Shor sequence, which are overlain with ravinement by terrigenous rocks of the Early Ordovician Telpos Formation. Intrusive rocks occur as metadolerites forming the Sablegorsk subvol canic rocks and also as their young analogues of Late Devonian age. Small metagabbro and metadiorite bodies are also observed. In the northern and south eastern parts of the region, there are the quite large Il'ya Iz and Man' Khambo granitoid plutons.Chlorite-sericite-quartz schists in the lower sub formation of the Sablegorsk Formation contain numer ous hydrothermal quartz and chlorite-calcite-quartz veins with superimposed pyrite, pyrite-chalcopyrite, galena-chalcopyrite, and chalcopyrite-bornite-chal cocite mineralization. The veins are 0.5 m in thickness. Contacts of the veins with the host rocks are sharp, often interrupted. Rocks near the veins are chloritized and sericitized. The sulfide distribution is irregular dis seminated, disseminated-stringer, and cluster within the quartz veins. Secondary minerals such as limonite, cerrusite, malachite, azurite, and chrysocolla are wide spread. According to the atomic absorption analysis data, the Au content in grab and trench samples from the vein segments enriched in sulfides varies from 1.2 to 7.6 g/t. Along with Au, high Ag, Bi, and Cu concentra tions were noted.The most widespread sulfide of the veins is pyrite, which commonly occurs as cubic grains of 3 mm in size at most. Pyrite is often accompanied by chalcopy rite, more rarely, by chalcocite and bornite. Chalcocite and bornite are nearly always closely conjugated and form linear oriented platy structures similar to exsolu tion textures. In the course of microprobe analyses, we identified Co (rarely, up to 1.9 wt %) in pyrite and Bi (up to 1.5 wt %), Te (0.7 wt %), Se (0.7 wt %), and Ag (1.3 wt %) in chalcocite and bornite.Gold...

On the matildite–bohdanowiczite solid-solution series

“…There are two possible substitutions for Se in bohdanowiczite: S (1.86 wt.% on average, with a maximum of 5.73 wt.% at the Moldava fluorite deposit, Czech Republic; Sejkora and Skacha 2015) and Te (an average of 0.96 wt.% with a maximum of 2.40 wt.% recorded at two deposits in Russia; Kovalenker and Plotinskaya 2005 and Kuznetsov et al ., 2012).…”

“….There are two possible substitutions for Se in bohdanowiczite: S (1.86 wt% on average, with a maximum of 5.73 wt% at the Moldava fluorite deposit, Czech Republic; Sejkora and Skacha 2015) and Te (an average of 0.96 wt% with a maximum of 2.40 wt% recorded at two deposits in Russia;Kovalenker andPlotinskaya 2005 andKuznetsov et al 2012). Matildite literature data compilationThe literature data compilation reveals that matildite contains on average 52.94 wt% Bi, 27.02 wt% Ag, and 16.29 wt% S (Table1).…”