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Impact spherules from Karelia, Russia: possible ejecta from the 2.02 Ga Vredefort impact event

Huber, Matthew S., Črne, Alenka E., McDonald, Iain, Hecht, Lutz, Melezhik, Victor A. and Koeberl, Christian 2014. Impact spherules from Karelia, Russia: possible ejecta from the 2.02 Ga Vredefort impact event. Geology 42 (5) , pp. 375-378. 10.1130/G35231.1

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Abstract

Spherule beds of possible impact origin have been discovered in two drill cores in the Paleoproterozoic Zaonega Formation, Karelia, northwest Russia. Spherules are found within the dolomite matrix of in-situ brecciated sedimentary dolostones. Spherules are millimeter size and generally round, although teardrop and dumbbell morphologies are present. Spherules contain up to 0.75 ppb Ir, with a Ru/Ir of 2, indicating a mixing of target rocks with a minor chondritic component. The age of the Zaonega Formation is constrained between limits of 1.975 ± 0.024 Ga (Sm-Nd) and 1.980 ± 0.057 Ga (Pb-Pb), and 2.050 Ga (Re-Os), which brackets the age of the 2020 Ma Vredefort impact structure in South Africa, and suggests that the spherule beds could represent ejecta from that event. If the link is confirmed, the size of the spherules and thickness of the beds suggest that the distance from the impact site was <2500 km, thereby constraining the paleogeographic distance between the Fennoscandian Shield and Kaapvaal craton during the late Paleoproterozoic.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Publisher: Geological Society of America
ISSN: 0091-7613
Date of Acceptance: 4 February 2014
Last Modified: 27 Feb 2019 15:31
URI: http://orca.cf.ac.uk/id/eprint/68655

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