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
30
Citation
69
Reference
10
Related Paper
Citation Trend
Abstract:
A new U–Pb baddeleyite age of 1970 ± 3 Ma for the Unoi dolerite sill of the Onega structure of Karelia craton matches other 1.98–1.95 Ga 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 1.98–1.95 Ga magmatic rocks result in a new robust paleopole for the Karelian craton and accentuate its variable paleolatitude and paleoorientation during the Paleoproterozoic.Keywords:
Sill
Baddeleyite
Large igneous province
Swaging
Dike
Geochronology
Dikes in which two different liquids flowed simultaneously, usually called composite dikes, naturally fall into two classes depending on which lithology forms the contact with the country rock, and hence, which liquid was the first to enter the fracture. In these two kinds of dikes, the structures formed by the mingling of the two liquids differ. Dikes in which the more basic liquid entered first have contacts between the two lithologies that are nearly planar, and parallel to the dike walls, whereas the more basic lithology forms discrete pillows in those dikes in which the more silicic liquid entered first. Experiments indicate that these pillows probably form from a flow-front instability that develops when a liquid invades another of higher viscosity between two parallel rigid walls. We provide scalings for the critical flow rate for the onset of this instability, the time required for the instability to develop, and the wavelength that is selected. These scalings are consistent with field observations.
Sill
Dike
Cite
Citations (7)
Dike
Sill
Large igneous province
Magma chamber
Cite
Citations (27)
Dike
Sill
Cite
Citations (175)
Baddeleyite
Sill
Dike
Baltic Shield
Large igneous province
Cite
Citations (5)
The Koolau dome, forming the east half of the island of Oahu, is notably elongate, built about a linear rift zone in which numerous feeder dikes occur in a dike complex over 30 miles long. Scattered dikes and sills occur in the leeward parts of the dome, the concentration being progressively reduced with the distance away from the dike complex. There are secondary rift zones and subcomplexes with increased concentrations of dikes and sills, which trend at right angles to the main rift zone. The dikes and sills show three stages and patterns of columnar jointing which are related to the cooling history. Shallow intrusives are vesicular and banded but not columnar jointed. Dikes with a thickness of about 2 feet are preponderant to such an extent as to suggest that this is an optimum determined by the amount of lateral crowding-together of contracted lava formations which can be achieved by the pressures of invading lava.
Dike
Sill
Dome (geology)
Rift zone
Cite
Citations (23)
Dike
Sill
Flood basalt
Large igneous province
Cite
Citations (63)
Sill
Dike
Magma chamber
Cite
Citations (233)