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Russian Geology and Geophysics

2006 year, number 12

METALLOGENY OF THE POLYACCRETIONARY ALTAI-SAYAN OROGENIC AREA

E.G. Distanov, A.S. Borisenko, A.A. Obolensky, V.I. Sotnikov, and V.I. Lebedev*
Institute of Geology and Mineralogy, Siberian Branch of the RAS,
3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
* Tuvinian Institute of Complex Exploration of Natural Resources, Siberian Branch of the RAS,
177a ul. Internatsional'naya, Kyzyl, 667007, Russia
Keywords: Metallogeny, terrane analysis, ore deposits, geodynamic settings
Pages: 1232-1250

Abstract

A general metallogenic analysis and metallogenic zoning of the Altai-Sayan orogenic area (ASOA) were carried out in terms of the modern plate tectonics and mantle geodynamics concepts. The Altai-Sayan folded area is an example of a polyaccretionary orogenic system that resulted from the long evolution of the Paleoasian ocean. The main metallogenic belts have been recognized, in which typical ore associations (model types of mineral deposits) and their ages and geodynamic settings of formation have been established. A total of 48 metallogenic belts including 450 mineral deposits of 70 model types were studied. These belts are related to four time spans (metallogeny epochs) corresponding to the cycles of geodynamic processes that led to the formation of the polyaccretionary orogenic area: Riphean-Vendian (1200-620 Ma); Vendian-Silurian (620-410 Ma); Devonian-Early Carboniferous (410-320 Ma); and Late Permian-Triassic (260-205 Ma). Study was also given to typical geodynamic settings in which ore-forming productive systems originated. It is shown that the metallogenic evolution of the ASOA was determined mainly by the multistage formation of active continental margins and island-arc systems in the Riphean-Vendian and Early (V-S) and Middle (D-C1) Paleozoic.
At the postorogenic stage, the ASOA evolution was the most productive in the Triassic. The geodynamic and metallogenic events in this period were determined by the tectonothermal activity on the periphery of the Permo-Triassic Siberian superplume in the interblock zones of the orogenic collage, which led to serious shifts along the plate and block boundaries, the formation of near-fault troughs and grabens, appearance of rift structures, and development of anorogenic granitoid magmatism (manifested as alkali and subalkalic rare-metal granites) and alkali-basaltoid magmatism.
Transpression settings (oblique subduction) and plume magmatism are shown to have played a key role in the formation of mantle and mantle-crustal ore-forming systems. For the Middle Paleozoic and Mesozoic stages, new geochronological evidence has been obtained, and spatial and temporal correlations for the formation of the main types of mercury, gold, and rare-metal deposits have been made.