Geodynamic Setting, Age, and Petrogeochemical Features of Granitoids in the Chimalga Pluton, Main Batholith Belt (Verkhoyan–Kolyma Fold Area).

New U‒Pb SIMS and 40Ar‒39Ar geochronological, petrogeochemical, and isotope geochemical data for the granitoids of the Chimalga pluton in the central part of the Main batholith belt of the Chersky Range within the Verkhoyan–Kolyma fold area are presented. It is shown that the zircon crystallization ages of 150 and 152 Ma for granodiorites and leucogranites coincide within the error with the 40Ar‒39Ar amphibole age of 148.6 ± 5.6 Ma for the granodiorites of the pluton, as well as the ages of the felsic and intermediate volcanic host rocks of the Uyandina–Yasachnaya volcanic belt (150–152 Ma) and the peak of granitoid intrusion within the Main batholith belt (150 ± 3 Ma). The granitoids of the Chimalga pluton have petrogeochemical characteristics, which provide a possibility to classify them into I-type as well as S‑type granites. They are similar to I-type granites in the presence of biotite, hornblende, and clinopyroxene among mafic minerals; the absence of primary muscovite; and the prevalence of calc-alkalic and metaluminous varieties. Like S-type granites, the highly silicic compositions are characterized by the presence of ferroan and magnesian varieties. The granitoids contain high-alumina mineral aggregates associated with potassium feldspar, albite, and spinel, which suggest the presence of granulite-facies metapelites in magma source area. The Sr‒Nd isotope characteristics of the granitoids of the Chimalga pluton, as well as the interrelationship of certain rock-forming oxides indicate a heterogeneous source of granite melts. Negative εNd(Т) values that vary from –2.98 to –6.23, high primary 87Sr/86Sr values from 0.7073 to 0.7091, and the Mesoproterozoic model ages of the granitoids attest to the contribution of fairly mature continental crustal material to their petrogenesis. The granitoids are assumed to have formed in a marginal continental setting during the activity of the Uyandina–Yasachnaya volcanic arc. [ABSTRACT FROM AUTHOR]