Magmatic Telescoping as a Reflection of the Shift in Geodynamic Circumstances and Patterns of Formation of Gold Ore Manifestations in the Example of the Uskalin Granitoid Massif (Russia)

This paper considers the spatial distribution of gold occurrences, their geochemical anomalies, and late Mesozoic igneous complexes within the framing of the eastern flank of the Mongol–Okhotsk orogenic belt (EF MOOB). It is established that elevated gold concentrations are associated with telescoped igneous complexes formed in different geodynamic regimes. The southern framing of the EF MOOB (Russia) was chosen as the key study area due to its well-preserved superposition of multi-stage igneous events. These stages are considered using the example of the Uskalin intrusive massif. It is a representative example where three geodynamic phases are recorded, namely initial supra-subduction (149–138 Ma), subduction (140–122 Ma), and collision (119–97 Ma). It is shown that the massif is composed of granitoids aged 145 Ma, 129 Ma, and 112 Ma, which correspond to the distinguished geodynamic stages. Geochemical characteristics of the rocks of the first two stages completely coincide with those of the rocks corresponding to the geodynamic stages. The exception is the formations from the collision process. At this stage, differences appear in the rocks, which are manifested in the Sr/Y ratio. These values are comparable with those in the granitoids of the adakite series. Such differences were established only within gold-bearing areas. The formation of the Uskalin massif was accompanied by extensive mineralization zones with gold-bearing veins. Gold concentrations in granitoids of the adakite series (145 Ma) exceed the crustal Clarke value by 2.25 times, which directly links mineralization with magmatic processes. It is assumed that the presence of collision-stage rocks with signs of the adakite signature may be one of the signs of detection of epithermal gold ore objects in the zones of magmatic telescoping. Taking into account the evolution of the MOOB associated with the closure of the MOB and with the accompanying magmatic events, an analog of which is considered using the example of the southern framing of the EF MOOB, it is possible to assume the use of the obtained results in conducting exploration work for ore gold in this region.