Localization patterns of mineralization, age, and sources of substance of the Malomyr gold ore field (Eastern part of the Mongolian–Okhotsk fold belt)

To the best of our knowledge, this study is the first to reliably assess the age of gold mineralization in the Malomyr field (eastern part of the Mongolian-Okhotsk fold belt), one of the best known deposits in the Far East. The obtained data confirmed that the age of the hydrothermal ore process that resulted in the formation of the Malomyr deposit was ~ 134–130 million years and that the age of the postore dykes was 110–104 million years. Data related to the occurrence of magmatism within the region under consideration were not available, which made it impossible to link the ore mineralization of the Malomyr deposit with the magmatic processes. Based on the data obtained in this investigation, the dislocation processes accompanied by the hydrothermal activity that was confirmed using the structural examinations results evidently played a significant role in ore mobilization and redistribution as well as the formation of the Malomyr deposit. The first Rb-Sr and δ34S results of this research indicated that both the “crust” and “mantle” sources were available among the ore sources.