New U-Pb baddeleyite age, and AMS and paleomagnetic data for dolerites in the Lake Onega region belonging to the 1.98-1.95 Ga regional Pechenga-Onega Large Igneous Province

摘要

A new U-Pb baddeleyite age of 1970 +/- 3Ma for the Unoi dolerite sill of the Onega structure of Karelia craton matches other 1.98-1.95Ga units across the Kola craton (Pechenga) and widely separated parts of the Karelian craton, including the Lake Onega sill area and a extensive NW-trending dolerite dyke swarm. Herein these coeval units are combined into the Pechenga-Onega Large Igneous Province. The sills in the Lake Onega area exhibit similar geochemical patterns, although the Unoi dolerite sills appear less contaminated and less differentiated than the Pudozhgora intrusion, Gabnev sill and Koikary-Svatnavolok and Palieyeozero sills but are similar to other doleritic sills in the northern part of the Onega structure. New AMS data from sills are consistent with emplacement along the same NW-SE trend as the dykes, consistent with the dykes acting as their feeder system. Paleomagnetic data obtained on 1.98-1.95Ga magmatic rocks result in a new robust paleopole for the Karelian craton and accentuate its variable paleolatitude and paleoorientation during the Paleoproterozoic.