Special issue “Metallogeny of intraplate magmatism”

Abstract

Orogenic gold deposits are one of the most important gold deposits in the world. However, it is controversial that orogenic gold deposits are only generated at subduction-accretion or both in collisional setting. The Altai Orogen experienced a complex subduction accretion–collision history, including magmatism and metamorphism, and forming giant gold deposits. The Tokuzbay gold deposit consists of quartz vein ores and disseminated ores hosted in dikes. The ore bodies are controlled by secondary shear zone of the NW-, NNW-trending Ma’erkakuli Fault and occurred in meta-sediments, i.e., meta-sandstone and phyllite of Devonian Altai Formation, and diorite dikes and granite porphyritic dikes. Wall rock alteration is represented by silicification, pyritization, and muscovite alteration. The ores are restricted by ductile and brittle deformation in the shear zone. Large amounts of native gold and auriferous tellurium were precipitated during a transition from ductile to brittle regime. These characteristics indicate that the Tokuzbay gold deposit is an orogenic gold deposit in the Altai Orogen. The zircon LA-ICP-MS U-Pb ages of the ore-bearing granite porphyritic dikes and diorite dikes are 390 ± 2.5 Ma (MSWD = 0.87) and 378 ± 4 Ma (MSWD = 0.21), respectively, indicating that the magmatic rocks were emplaced during subduction of the Paleo Asian Ocean beneath Altai Orogen. Muscovite samples associated with gold from the auriferous quartz vein and disseminated ores hosted in diorite dikes returned Ar-Ar ages of 292.7 ± 1 Ma (MSWD = 1.3) and 293.9 ± 1.2 Ma (MSWD = 0.7), indicating that gold mineralization in quartz vein is synchronized with disseminated ores. The gold mineralization is restricted to the Early Permian and overlaps with the collision between Altai Orogen and Junggar Plate. The ore-hosting magmatic rocks related to subduction are more than 100 million years earlier than the ore-forming events. Combined with the regional tectonic evolution and the shear characteristics of the gold district, it is well proved that sinistral shearing trigged by the collision of Junggar Plate and Altai Orogen contributed to gold mineralization of the Tokuzbay deposit. Considering the Altai gold deposits in Kazakhstan, it is revealed that Permian collision between Junggar Plate and Altai Orogen triggered a large number of orogenic gold mineralization.