EPOCHS OF LATE PALEOZOIC ORE FORMATION IN HERCYNIAN OROGENIC STRUCTURES, CENTRAL KAZAKHSTAN

Analysis of recent radiometric ages of host rocks, ore-related metasom atites and ore minerals from the most economically significant deposit s located in various Hercynian orogenic structures of Central Kazakhst an is presented. The following productive ore-forming epochs have been recognized: 370 - 360 Ma, 315 - 300 Ma, and 290 - 260 Ma. The same ty pe of metal deposits commenced to form at different times in neighbori ng magmatogenic and sedimentogenic structures. Large deposits formed o ver dozens and even hundreds of millions of years. This is most pronou nced in porphyry copper and barite-base metal deposits. Ore matter app eared here long before the main stage of deposit formation. There was a considerable interruption between this stage and the emplacement of ore-forming plutons. Rare metal deposits are characteristic of a short er period of formation and a closer association in time with emplaceme nt of intrusions. Subsequent repeated processes of ore deposition and ore transformation simultaneous with the formation of younger deposits are inherent in many cases.