GEOLOGY AND STRUCTURAL EVOLUTION OF THE MURUNTAU GOLD DEPOSIT, KYZYL-KUM DESERT, UZBEKISTAN

The Muruntau gold deposit in the Kyzylkum desert of Uzbekistan is the largest single deposit (much greater than 1100 tonnes of gold) of the class of low-sulfide syndeformation/synigenous gold deposits formed in the brittle/ductile transition zone of the crust within transpression al shear zones. Hosted by the Cambrian to Ordovician Besopan Suite, th e ores were deposited in pre-existing thrust-fault- and metamorphism-r elated permeabilities and in synmineralization dilational zones create d in a large fault-related fold. The Besopan Suite is a 5,000-m-thick sequence of turbiditic siltstones, shales and sandstones. The ore is p rimarily localized at the base of the Besopan-3 unit, which is a 2,000 -m-thick series of carbonaceous shales, siltstones, sandstones and che rts. Initial gold deposition took place within the Sangruntau-Tamdytau shear zone, which was developed along the stratigraphic contact betwe en the Besopan-3 and Besopan-4 units. During the mineralization proces s, folding of the Besopan Suite and a left-step adjustment in the Sang runtau-Tamdytau shear zone were caused by two concurrent events: (1) t he activation of the left-lateral Muruntau-Daugyztau shear zone that d eveloped at nearly a 90 degrees angle to the preceding shear zone and (2) the intrusion of granitoid plutons. These structural events also r esulted in the refocusing of hydrothermal fluid flow into new zones of permeability.