Potentially commercial Alapayevsk-Sukhoy Log porphyry copper zone (the Middle Urals)

Abstract

NS-trending Alapayevsk-Sukhoy Log zone of porphyry-copper mineralisation in the Middle Urals is located 75 km to the east of Yekaterinburg and extends for 100 km from Alapayevsk to Sukhoy Log towns. Sulphide inclusions in rocks are pervasive, and there are numerous ore manifestations and small deposits. Like the commercial Mikheyevskoye porphyry copper deposit (over 1.7 million tonnes of Cu) in the Southern Urals, the zone is associated with the eastern part of East Urals volcanic megazone. It consists of several ore-producing NS-trending volcano-plutonic belts which represent the tectonic blocks. Rejuvenation from north to south of granitoid magmatism has been identified (U-Pb SHRIMP-II and LA ICP-MS zircon dating) in First magmatic stage (million years): from 412 (diorite-plagiogranodiorite-plagiogranite of Yaluninogorsk massif) to 404-406 (diorite-granodiorite-granite of Altynai-Artyomovsk intrusion), and then to 397 (plagiorhyodacite-porphyre of Shata area). Volumetrically sericitized and sulphidized quartz diorite of East-Artyomovsk massif was probably established during Second magmatic stage (369 ± 39 million years, Rb-Sr dating). All granitoids are of arc-island geochemical type, and have feature near-mantle isotopic signatures: (87Sr/86Sr)t = 0.7038-0.7049, (εNd)t = 6.6-8.7. Systemic and comprehensive study of Alapayevsk-Sukhoy Log zone should result in discovery of commercial large scale porphyry copper deposits (assuming current cut-off grade of Cu 0.15-0.20 wt %). The most attractive in terms of potential for high capacity stockworks is the East Artyomovsk massif which is similar in many respects to ore-magmatic system of Mikheyevsk deposit