Metallogenic processes that formed the Cu-Au-Mo porphyry and epithermal Au-Ag-Te deposits in the Almalyk ore district

The geologic setting of the Kurama mining district is controlled by its assignment to the structures of the eastern part of the extended Beltau–Kurama volcanoplutonic belt in the Middle Tien Shan. This district of Paleozoic age exemplify unique deposits with perfectly preserved characteristic features of Cu-Au-Mo porphyry, epithermal Au–Ag–Te, Ag–Pb–Zn, as well as numerous occurrences of Au, Ag, Cu, Pb, Zn, Bi, and Sn mineralization. Intense magmatic processes occurred in this region throughout the whole Paleozoic, reaching a maximum at its end. The very high concentration of ore occurrences is related to the confinement of the region to the intersection of deep tectonic structures. Another unique feature of this region is that it is a rare example of paleovolcanic areas with well preserved epithermal deposits of Late Paleozoic age. Here we compile published and some new geodynamic, mineralogical and geochemical data, including regional geological features and ore characteristics, sequence of the mineral formation, main mineral assemblages and discuss factors controlling the enrichment mechanism of huge amounts of Cu, Au, Mo, Ag, Re, Pd, Pb, Zn and other elements in the Almalyk ore-field through field and laboratory investigation. We will present summary of the geological, geochronologic and geochemical characteristics of porphyry, scarn and epithermal gold-silver deposits to establish a series of discriminant indicators, which can provide reference for future research on the genetic connection of different deposits in the porphyry copper system. The occurrence of mafic dikes, post-dating the porphyry mineralization and high Re concentrations in the molybdenite may be attributed to a direct involvement of mantle in an arc-subduction environment. But it is becoming more obvious that the problem of sources of ore and rare elements forming cannot be solved only by their introduction with magma. In many specific examples of the formation of the largest and unique concentrations, their confinement to the underlying and enclosing sedimentary rocks, sharply enriched in valuable impurities, is observed. These rocks include organogenic dolomites or dolomitic limestones. During intrusion of igneous bodies, the presence of reactive carbonate rocks (limestone, dolomite, marl) led to the formation of gold-bearing Au-Cu- and Pb-Zn-skarn deposits. The integrated results of this study are used to discuss the metallogenic processes that formed the unique Cu-Au-Mo porphyry, epithermal Au–Ag–Te, Ag–Pb–Zn deposits in the largest porphyry copper-polimetallic ore Almalyk district in the Central Asian Orogenic Belt.