The
Akhtala copper deposit is located 12 km NE of Alaverdi (20 km by road)
in the Lori Province of northern Armenia. Akhtala forms an ore field
with the nearby Shamlug deposit.
The 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 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 occur in river valleys.
Akhtala is a metal zoned system of submarine “exhalational” orebodies
that are close to the Japanese kuroko VMS model. Hosted by Middle-Upper
Jurassic submarine andesitic pyroclastrics and volcaniclastics
(propylitized tuff breccias, tuff, andesite porphyry flows and dikes)
the silicified, sericitized and chloritized rocks contain lenticular or
domal bodies of internally brecciated to massive pyrite >>
chalcopyrite, sphalerite > galena that are conformable with the host
supracrustals. This is topped by lenses of red (hematite-pigmented) and
white barite, and hematite. Barite and silicified or quartz-veined
breccias contain scattered crystals of pyrite, chalcopyrite, sphalerite
and galena.
The Akhtala deposit was worked by underground mining during the Soviet
era.
As of 2010 no tonnage information was available. Estimated
endowment is of the order of 100 Kt of barite, 50 Kt Zn, 20 Kt Pb and
Cu.
(Source: Peter Laznicka, September 2012)
