The Kapan Shahumyan Ag-Au deposit is located 2-3 km E of Kapan in the Syunik Province of southern Armenia. In contrast with the Zangezur porphyry Cu-Mo province west of Kapan dominated by Eocene through Miocene continental margin magmatic arc activity, the Kapan area is a part of the Somkhet-Karabagh “eugeoclinal” zone of Middle Jurassic submarine andesitic to bimodal volcanism and sedimentation, the result of magmatism produced by subduction of the leading edge of Gondwana beneath Laurasia. This metallogenic zone contains several VMS deposits (Kuroko-style Akhtala with barite) as well as Cu veins, stockworks and replacements (Alaverdi, Kapan-Central) in andesites believed associated with the submarine metallogenesis and possibly part of the feeder (plumbing) system of the missing (eroded?) VMS lenses.
The Somkhet-Karabagh zone can be traced, with interruptions, from Georgia (Bolnitsi district) through NE Armenia (Alaverdi, Shamlug; see LT 5032 and 5033) to the Kapan area and farther south to Iran. It is a thick sequence of repeatedly alternating andesite with local Na-altered basalt units (“spilite”) and sodic felsic volcanics (“keratophyre”) and with units of volcaniclastics and limestone on top. It is intruded by several comagmatic massifs of gabbro, diorite, monzonite and granodiorite, and by dike swarms and it is believed that the Kapan ore field is in the roof of buried Late Jurassic intrusion. Several erosional relics of Quaternary basalt flows are in Kapan area.
The Shahumyan deposit is a system of numerous subparallel fault and fissure veins in andesites with sericite, clay or quartz altered selvages within a regional propylitic alteration (chlorite, epidote, albite, calcite). The multistage veins have early quartz and pyrite; later sphalerite > chalcopyrite, galena; latest sparry calcite and Mn carbonates. The veins contain mainly scattered sulfides with variable gold values and local rich shoots with galena, Ag-sulfosalts and tellurides. Several thicker veins are now selectively mined from underground but there is an extensive resource in the form of thinner, closely spaced veins amenable to bulk mining - this would require official blessing difficult to obtain in the present climate of local opposition to mining (although this is the only industry in the area). Most of the veins are blind, without outcrop expression, hence lacking supergene modified tops.
In 2010, active underground mining of the Shahumyan deposit was being carried out by Dena Gold.
The Shahumyan resource figures released by Dena Gold (2010) are 17.7 Mt @ 2.81 g/t Au, 50 g/t Ag, 2.72% Zn, 0.66% Cu. The resource of the potentially bulk mineable ore in proposed open pit are 336 Mt @ 0.48 g/t Au, 8.39 g/t Ag, 0.41 % Zn, 0.11% Cu for the total endowment of ~211 t Au, ~3,700 t Ag, 1.85 Mt Zn and ~490 kt Cu.
(Source: Peter Laznicka, September 2012)
