Publication Date:
2013-01-30
Description:
K-Ar ages of authigenic illite from two drill-core gouge samples of a fault in the Paleoproterozoic basement of Finland record two distinct faulting events. The older sample yields apparent ages from 1240 ±26 to 1006 ±21 Ma for four grain size fractions between 6 to 〈 0.1 μm. The second sample is structurally younger and yields statistically distinct ages ranging from 978 ±20 to 886 ±18 Ma. We interpret the ages of the 〈0.1μm fractions, which are the youngest, as representing the actual time of faulting. Age modelling excludes significant age contamination of the dated fractions with inherited host rock components. These results provide therefore an example of meaningful isotopic dating of illite-type clay material formed during Precambrian faulting, demonstrate and constrain fault reactivation and give evidence for brittle Sveconorwegian Mesoproterozoic shortening and Neoproterozoic extension in Fennoscandia. © 2013 Blackwell Publishing Ltd
Print ISSN:
0954-4879
Electronic ISSN:
1365-3121
Topics:
Geosciences
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