Geodynamics and metallogeny of the central Eurasian porphyry and related epithermal mineral systems: A review

Abstract Major porphyry Cu–Au and Cu–Mo deposits are distributed across almost 5000 km across central Eurasia, from the Urals Mountains in Russia in the west, to Inner Mongolia in north-eastern China. These deposits were formed during multiple magmatic episodes from the Ordovician to the Jurassic. They are associated with magmatic arcs within the extensive subduction–accretion complex of the Altaid and Transbaikal-Mongolian orogenic collages that developed from the late Neoproterozoic, through the Palaeozoic, to the Jurassic intracratonic extension. The arcs formed predominantly on the Palaeo-Tethys Ocean margin of the proto-Asian continent, but also within two back-arc basins. The development of the collages commenced when slivers of an older Proterozoic subduction complex were rifted from an existing cratonic mass and accreted to the Palaeo-Tethys Ocean margin of the combined Eastern Europe and Siberian cratons. Subduction of the Palaeo-Tethys Ocean beneath the Karakum and Altai-Tarim microcontinents and the associated back-arc basin produced the overlapping late Neoproterozoic to early Palaeozoic Tuva-Mongol and Kipchak magmatic arcs. Contemporaneous intra-oceanic subduction within the back-arc basin from the Late Ordovician produced the parallel Urals-Zharma magmatic arc, and separated the main Khanty-Mansi back-arc basin from the inboard Sakmara marginal sea. By the Late Devonian, the Tuva-Mongol and Kipchak arcs had amalgamated to form the Kazakh-Mongol arc. By the mid Palaeozoic, the two principal cratonic elements, the Siberian and Eastern European cratons, had begun to rotate relative to each other, “drawing-in” the two sets of parallel arcs to form the Kazakh Orocline between the two cratons. During the Late Devonian to Early Carboniferous, the Palaeo-Pacific Ocean began subducting below the Siberian craton to form the Sayan-Transbaikal arc, which expanded by the Permian to become the Selanga-Gobi-Khanka arc. By the Middle to Late Permian, as the Kazakh Orocline continued to develop, both the Sakmara and Khanty-Mansi back-arc basins were closed and the collage of cratons and arcs were sutured by accretionary complexes. During the Permian and Triassic, the North China craton approached and docked with the continent, closing the Mongol-Okhotsk Sea, an embayment on the Palaeo-Pacific margin, to form the Mongolian Orocline. Subduction and arc-building activity on the Palaeo-Pacific Ocean margin continued to the mid Mesozoic as the Indosinian and Yanshanian orogens. Significant porphyry Cu–Au/Mo and Au–Cu deposits were formed during the Ordovician in the Kipchak arc (e.g., Bozshakol Cu–Au in Kazakhstan and Taldy Bulak porphyry Cu–Au in Kyrgyzstan); Silurian to Devonian in the Kazakh-Mongol arc (e.g., Nurkazgan Cu–Au in Kazakhstan and Taldy Bulak-Levoberezhny Au in Kyrgyzstan); Devonian in the Urals-Zharma arc (e.g., Yubileinoe Au–Cu in Russia); Devonian in the Kazakh-Mongol arc (e.g., Oyu Tolgoi Cu–Au, and Tsagaan Suvarga Cu–Au, in Mongolia); Carboniferous in the Kazakh-Mongol arc (e.g., Kharmagtai Au–Cu in Mongolia, Tuwu-Yandong Cu–Au in Xinjiang, China, Koksai Cu–Au, Kounrad Cu–Au and the Aktogai Group of Cu–Au deposits, in Kazakhstan); Carboniferous in the Valerianov-Beltau-Kurama arc (e.g., Kal’makyr–Dalnee Cu–Au in Uzbekistan; Benqala Cu–Au in Kazakhstan); Late Carboniferous to Permian in the Selanga-Gobi-Khanka arc (e.g., Duobaoshan Cu–Au in Inner Mongolia, China); Triassic in the Selanga-Gobi-Khanka arc; and Jurassic in the Selanga-Gobi-Khanka arc (e.g., Wunugetushan Cu–Mo and Jiguanshan Mo in Inner Mongolia, China). In addition to the tectonic, geologic and metallogenic setting and distribution of porphyry Cu–Au/Mo mineralisation within central Eurasia, the setting, geology, alteration and mineralisation at each of the deposits listed above is described and summarised in Table 1 .