TWO STAGES OF FORMATION OF THE YAKHTON TUNGSTEN-POLYMETALLIC-GOLD DEPOSIT (SOUTHERN TIEN SHAN, UZBEKISTAN): FIRST ISOTOPIC U-Pb AGE DATA ON ZIRCON (LA-ICP-MS METHOD) FROM THE INTRUSIVE ROCKS OF THE YAKHTON STOCK

The paper presents first isotopic U-Pb zircon data (LA-ICP-MS method) on the intrusive rocks from the Yakhton stock, which is spatially and probably genetically related to the Yakhton tungsten skarn (tungsten-polymetallic-gold) deposit. This deposit, together with the other W and Au deposits, is part of the largest Au-W metallogenic belt of Tien Shan. The deposit is represented by zones of hydrothermally-altered skarn with scheelite and sulfides (pyrrhotite, chalcopyrite), and later (overprinting) near- and within-intrusive stockworks of veins and veinlets of late metasomatites (propylitic and phyllic alteration) with scheelite-gold and Ag-polymetallic mineralization. The concordant isotopic zircon U-Pb data obtained (305 ± 2 Ma for the early monzonite-quartz monzonite, 304 ± 2 Ma for the granodiorite of the main phase, and 285.4 ± 1.8 Ma for granite) indicate the intrusion emplacement in the Late Carboniferous-Early Permian. This is similar to the dates of the intrusions at the large Jialu Au-W deposit, which is situated in the same metallogenic zone and comprises, together with the early scheelite skarn, also late metasomatites with intense Au-W mineralization corresponding to a large Au deposit. Such age, geological and metallogenic proximity to the Jilau deposit highlights a potential of discovery of significantly greater, than it is currently known, Au-W mineralization at the Yakhton deposit.