Postcollisional Age of the Kumtor Gold Deposit and Timing of Hercynian Events in the Tien Shan, Kyrgyzstan

摘要

We report here ~(40)Ar/~(39)Ar whole-rock and sericite data for host-rock (sericite-quartz altered rock) and gold ore (pyrite-quartz-feldspar-carbonate) from the giant Kumtor gold deposit in the Tien Shan fold and thrust belt of Kyrgyzstan, one of the largest orogenic gold belts on Earth. Plateau ages for whole-rock samples of sericite-quartz altered rock and sericite-bearing gold ore are 285.5 + - 1.2 and 288.4 + - 0.6 Ma. Sericite concentrates gave plateau ages of 284.3 + - 3.0 (host rock) and 285.4 + - 0.2 (ore) Ma. The age of mineralization is slightly younger than a U-Pb zircon age of 296.7 + - 4.2 Ma obtained for the post-collisional Djangart granite, about 80 km southeast of Kumtor, and slightly older than two published U-Pb ages of 268 + - 1 and 280 + - 9 Ma on a postcollisional granite intrusion about 10 km west of Kumtor. These ages also overlap with data from the other major gold deposits of the 2,000-km-long southern Tien Shan fold and thrust belt. The ages define a late Paleozoic event of gold mineralization related to regional-scale fluid flow and granite magmatism controlled by transcrustal shear zones during the postcollisional stage.