The initial stage of Early Carboniferous rifting in the Southern Urals: fi rst results of zircon U-Pb dating from granitoids of Neplyuevka complex

Abstract

Zircons from the Early Carboniferous granitoids of the Neplyuevkа massif of the South Urals have been dated (SHRIMP). Two different age groups are distinguished among the studied zircons: 1 — from 334 to 342 Ma; 2 — from 354 to 356 Ma. The older ages probably correspond to the time of zircon crystallization from the melt, while the younger ages resulted from a partial loss of radiogenic lead by zircon during the cooling of the massif or from thermal impact of Early Carboniferous or even Early Permian intrusions. The formation of the Neplyuevkа complex at the very beginning of the Carboniferous marks the most important stage in the geodynamic evolution of the Southern Urals — a rapid transition from island arc magmatism, which continued during Devonian, to riftogenic magmatism, which ended only in middle Visean.