LATE-OROGENIC GRANITOIDS OF THE TERVU AGMATITIC ZONE IN THE SOUTHEASTERN PART OF THE SVECOFENNIAN BELT (THE NORTHERN LADOGA AREA, RUSSIA)

Abstract

The formation of breccia zones was taking place with the simultaneous healing of them by granitic materials at the final stages of the Late Proterozoic magmatic and metamorphic activity in the region 1.86 Ga ago. The Tervu breccia zone with granitic agmatites has a sublatitude orientation, which is discordant in relation to the early structures and Kurkieki enderbite and Lauvatsari-Impiniemi diorite-tonalite complexes in the Svecofennian rocks of the Ladoga region. There are the largest granitic bodies in this area – Tervu and Peltola intrusions located in the Tervu breccia zone. The U–Pb age of monazite from granites of the Peltola intrusion is determined as 1859 ± 4 Ma, and coincides with the age of the granites of the Tervu intrusion (1859 ± 3 Ma). This assumes that the granites of both intrusions and some surrounded smaller bodies were intruded simultaneously into the tectonically weakened space when plastic deformations turned to elastic-plasticity ones during at the late-orogenic stage. The results obtained reveal the features of the tectonic development of the joint zone of the two largest blocks of the Fennoscandinavian shield – the Karelian craton and the Svecofennian belt.