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Reimar Seltmann, Natural History Museum (United Kingdom)
Robin Armstrong, Natural History Museum (United Kingdom)
Alla Dolgopolova, Natural History Museum (United Kingdom)
Alexander Yakubchuk, Natural History Museum (United Kingdom)
Dmitry Konopelko, St Petersburg State University (Russian Federation)
Robert A. Creaser, University of Alberta (Canada)
Ryan Morelli, University of Alberta (Canada)
Xiaofan Zhang, Xinjiang University (China)
Chuan Chen, Xinjiang University (China)
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Major porphyry Cu-Au and Cu-Mo deposits (e.g. Oyu Tolgoi in Mongolia >2.3 Gt @ 1.16% Cu, 0.35 g/t Au and Kal'makyr-Dalnee in Uzbekistan >5 Gt @ 0.5% Cu, 0.4 g/t Au) are distributed across central Eurasia [1]. These deposits were formed during a range of magmatic episodes from the Ordovician to the Jurassic [2]. They are associated with magmatic arcs within the extensive subduction-accretion complex of the Altaides, Mongolides and Baikalides Orogenic Collages that developed from the late Neoproterozoic, through the Palaeozoic to the Jurassic intra-cratonic extension, predominantly on the palaeo-Tethys Ocean margin of the proto-Asian continent, but also associated with the closure of two rifted back-arc basins behind that ocean facing margin. The complex now comprises collages of fragments of sedimentary basins, island arcs, accretionary wedges and tectonically bounded terranes composed of Neoproterozoic to Cenozoic rocks. Moreover, although belonging to two different terrane settings, the giant Cu-Au porphyries of the Chatkal-Kurama range (Almalyk district, Valerianov-Beltau-Kurama magmatic arc, Middle Tien Shan) and the giant orogenic Au mineralisation hosted by black-shale series of the Central Kyzylkum slate belt (Southern Tien Shan, Khanty-Mansi accretionary complex) have some striking similarities. This hints at crust-mantle interaction and dominance of a deep-seated regime during emplacement. They are temporally close (315 to 287 Ma [3]), their isotope signatures reveal the incorporation of a moderate mantle component, and geophysical patterns from the middle crust in the region exhibit zones of low reflection indicating the existence of extended mafic bodies just beneath both giant ore-magma systems. This research was supported through NHM's CERCAMS programme and the National Basic Research Program of China - 973 Program (No. 2007CB411301, No. 2007CB411308).
[1] Seltmann R. & Porter M. (2005), Super Porphyry Copper & Gold Deposits, PGC Publ. 2, 467-512
[2] Yakubchuk A. (2004) J. Asian Earth Sci. 23, 761-779
[3] Morelli R. et al. (2007) Geology 35, 795-798
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