GEOLOGIC SETTING AND U-PB AGE OF THE SHCHUCH'IA BAY GRANITOIDS, KOLA PENINSULA

Abstract

U-Pb age values were obtained on an intrusion of alkaline quartz diorite in the northwestern closing of the Paleoproterozoic Imandra-Varzuga sedimentary-volcanic structure in the Kola Peninsula. The diorite is hosted by volcanics of the Kukshinskaya Formation, which were produced early in the evolution of the structure, and the Late Archean Arvarechka Formation. According to our data, the rocks have an age of 2048 ± 8 Ma and mark the switch from an early to a late rifting environment in the evolution of the structure. This period is characterized by an increase in the magma generation depths and was associated with a significant heating of the upper crust and the development of secondary magmatic chambers.