Abstract In the Central Asian copper province seven copper belts each host at least one large (>5 million metric tons (Mt)) Cu deposit or deposit cluster; three other copper belts each host at least one medium-size (∼4 Mt) Cu deposit, with copper resources likely to increase during ongoing exploration. Of these, eight copper belts host porphyry deposits, including four giant (>10 Mt Cu) porphyries (Oyu Tolgoi, Almalyk, Aktogai, and Erdenet); one belt contains sediment-hosted deposits (including giant Dzhezkazgan); and one belt hosts volcanogenic massive sulfide (VMS) deposits. The deposits formed in seven periods between 510 and 240 Ma, with ∼30- to 50-m.y. intervals between porphyry emplacements occurring mostly between the major tectonic events, whereas formation of the sediment-hosted deposits was coeval with the major collisional tectonic event in the Tien Shan and Urals at 290 Ma. The greatest metal endowment and largest number of individual deposits fall into the period 320 to 340 Ma (Almalyk, Aktogai), followed by the second most important period at 385 to 370 Ma (Oyu Tolgoi and Magnitogorsk), and third most important event at 295 Ma (Dzhezkazgan). Individual copper belts are typically several hundreds of kilometers long, dominated by a single deposit type, and commonly have only one large to giant deposit in a belt (this may partially be a function of preservation but also of exploration maturity). Most copper belts were generated under transpressional tectonic regimes in either arc or backarc settings. Local structural controls include terrane boundaries and crustal-scale arc-oblique or arc-parallel faults. The immature arc terranes generally host deposits with 3- to 5-Mt Cu endowments in porphyry or VMS deposits. Deposits with giant, >10-Mt Cu endowments were discovered in regions of tectonic overlap; giant porphyry deposits occur in mature, overlapping magmatic arcs, and sediment-hosted deposits are present in 3- to 6-km-thick, overlapping sedimentary basins. Plate tectonic reconstructions suggest a strong correlation of higher grade (>0.6 wt % Cu) porphyry copper deposits with peri-oceanic magmatic arcs, whereas lower grade (0.35–0.5 wt % Cu) porphyry deposits occur in magmatic arcs that formed in relationship to subduction in backarc oceanic basins. Based on distance to the respective ophiolitic sutures, which indicate the traces of the former subduction zones, we have estimated the approximate dip of the paleosubduction zone. We propose a correlation between a low (∼30°) angle dip of the reconstructed subduction zone and the larger copper endowment of related porphyry deposits.

Abstract The richest gold province in central Eurasia, containing about two-thirds of the region's gold reserves, occurs in the late Paleozoic fold and thrust belts of the Tien Shan, a component of the giant Altaid orogenic collage. Extending through Uzbekistan, Tajikistan, Kyrgyzstan, and continuing into western China, the Tien Shan hosts an array of world-class gold deposits. Principally, these include late Paleozoic orogenictype gold deposits, such as Muruntau and Kumtor, two of the world's 10 biggest gold resources. Such deposits are often temporally and spatially associated with syntectonic granitoid intrusions that were emplaced into a terrane of metamorphosed terrigenous carbonaceous rocks of Late Proterozoic to middle Paleozoic age. In addition, many gold deposits are also related to world-class Cu porphyry, epithermal, and skarn systems formed earlier during early-middle Carboniferous magmatic-arc activity. Similar, but smaller and older, deposit types occur throughout the entire Altaids. This orogenic collage consists of several Vendian to late Paleozoic magmatic arcs, which were first rifted off the eastern European and Siberian cratons. The clockwise rotation of Siberia relative to eastern Europe during middle and late Paleozoic caused several collisional episodes of these arcs, both with each other and with the cratons, as well as their gradual oroclinal bending. The formation of porphyry and epithermal deposits in the magmatic arcs coincides with the episodes of their oroclinal bending, whereas each collisional episode coincides with the formation of orogenic gold deposits. The giant gold deposits, however, formed during the final amalgamation of the collage in the Tien Shan province. Although the Tien Shan has been actively studied during the Soviet era, it remains relatively underexplored, and the regionally extensive gold mineralization indicates that considerable potential for major new discoveries still exists in the province. It is a highly prospective terrane for orogenic gold deposits especially, but also for skarn, Carlin-like, and epithermal gold occurrences, which may represent a broad-scale telescoping of hydrothermal systems. Conceptual models of orogenic gold mineralization in the belt invoke interaction between imbricated thrusts, deep-seated high-angle reverse and strike-slip faults, synorogenic granitoid intrusions, and metalliferous black shales during late Paleozoic arc-continent collision and deformation. These factors represent the main geologic criteria that provide the maximum potential for the formation of gold deposits in the Tien Shan and can be extrapolated to assist exploration elsewhere in the Altaids.

Abstract The Baikalide–Altaid, Transbaikal–Mongolian and North Pacific orogenic collages consist of several oroclinally bent magmatic arcs separated by accretionary complexes and ophiolitic sutures located between the major cratons. The tectonic and metallogenic patterns of these collages are principally similar as they were formed as a result of rotation of the surrounding cratons and strike-slip translation along the former convergent margins.