Barremian Magmatism of the Northwest of the Tytylveem Depression (Western Chukotka)

The article presents new data on the isotopic geochronology and geochemistry of magmatic complexes on the northwestern periphery of the Tytylveem Depression, Western Chukotka. U-Pb ages obtained for the emplacement of monzonite stocks of the Chukotka complex (124±1 Ma) and for the onset of effusive activity associated with the flood basaltic andesites of the Tytylveem formation (124±1 Ma) are the oldest known ages of post-collisional magmatism within the Chukotka region. Granitoids of the Chukotka complex are dated for the first time. Dolerites of the Tytylveem subvolcanic complex differ from the host Tytylveem volcanic rocks by lower MgO, higher K contents, and affilation with the oxidized magnetite series. Monzonites of the Chukotka complex and subvolcanic dolerites derive from sources with a higher proportion of depleted mantle component then the younger (122–117 Ma) rocks of the Tytylveem volcano-plutonic belt. Mineralogical and geochemical characteristics of the monzonites indicate that the Chukotka complex magmatic rocks may belong to the core of a porphyry epithermal system that includes the Dvoinoye and Sentyabrskoye deposits.