Geochronological and geochemical features of magmatic gold- and silverbearing complexes in the Chukotka sector of the Russian Arctic coast

Abstract

Research subject. This study was devoted to magmatic complexes in Northwestern Chukotka associated with the largest gold and silver deposits across Kupol’skii (Kupol field) and Ilirnei (Dvoinoe and September fields) ore junctions. Materials and methods. The petrogenic elements of ore-containing igneous rocks were determined using a spectrometer ICAP 6500Duo (USA). An elemental analysis of igneous and ore samples was performed by inductively coupled plasma spectrometry (ICP-MS). The age was determined by zircons (SHRIMP-II, VSEGEI isotope research center, St. Petersburg) using a laser ablation system NWR-213 (USA). Results. New information concerning the dating of magmatic complexes and gold-bearing magmatic systems in the ore junctions under study was obtained. It was established that the manifestations of magmatism in the Kupol and Ilirnei ore junctions differ in terms of the main phase formation age. The age of the Ilirnei ore junction, which is represented by large-volume intrusions of granitoids, leucogranites and volcanites of medium-basic composition, was determined to be 124–114 Ma. The age of mineralization, which is associated with later magmatism phases – small intrusions and a dike complex of predominantly granodiorite composition –, was estimated to be (93– 92) ± 2.0 Ma. In the Kupol ore junction, the magmatism associated with mineralization was dated 91.0 ± 1.4 Ma, while the age of rhyolite dikes containing mineralization was estimated to be 88.9–89.0 Ma.Conclusion. The results of the RMS analysis of the Kupol and Ilirney ore junctions suggest that ore formation in this region was connected with a single stage of activation of deep processes and mantle-crust interaction with participation of deep (mantle) fluids.

Keywords

• magmatism
• mineralization
• circumpolar western chukotka
• shrimp-dating
• rms generation features