Sm/Nd and 40Ar/39Ar Isotope-Geochronological Studies of Amphibolite of the Khanmeikhoi Formation of the Kharbei Metamorphic Complex (Polar Urals)

The first Sm/Nd and 40Ar/39Ar isotope-geochronological studies of amphibolite of the Khanmeikhoi Formation of the Kharbei metamorphic complex (Kharbei Block, Polar Urals) showed that metamorphism reaching the conditions of the amphibolite facies of moderate and high pressures occurred in the Devonian (367 +/- 40 Ma (amphibole, plagioclase, whole rock), 392 +/- 23 Ma (amphibole, garnet, whole rock), Sm/Nd method) and is consistent with the age estimates of high-pressure and regressive metamorphism within the Marunkeu Block. They correspond to the stage of radical restructuring of subduction processes that began in the Silurian to the east of the Baltica, associated with the subduction of the paleocontinent edge beneath the island arc and wedging of the subduction zone. The regressive stage and the beginning of the exhumation of the Kharbei metamorphic complex occurred in the Early Carboniferous (346 +/- 5 Ma, amphibole, 40Ar/39Ar method). Judging from the model age of amphibolite (T(DM2) of 1.07 and 1.13 Ga) corresponding to the Middle-Late Riphean boundary, the Khanmeikhoi Formation is not older than that time.