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Early Proterozoic activity on Archean faults in the western Superior province - evidence from pseudotachylite

Geology

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Abstract

Major transcurrent faults in the Superior province developed in the Late Archean at the close of the Kenoran orogeny. Reactivation of some of these faults late in the Early Proterozoic is indicated by Rb-Sr analyses of pseudotachylite from the Rainy Lake-Seine River and Quetico faults in the Rainy Lake region of Minnesota and Ontario. Fault veins of pseudotachylite and immediately adjacent country rock at two localities yielded subparallel isochrons that are pooled for an age of 1947??23 Ma. K-Ar and Rb-Sr biotite ages register earlier regional cooling of the terrane at about 2500 Ma with no evidence of younger thermal overprinting at temperatures exceeding 300??C. Accordingly, the 1947??23 Ma age is interpreted as dating the formation of the pseudotachylite. Reactivation of existing faults at this time was caused by stresses transmitted from margins of the Superior province where compressional tectonic events were occurring. -Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Early Proterozoic activity on Archean faults in the western Superior province - evidence from pseudotachylite
Series title:
Geology
Volume
17
Issue:
12
Year Published:
1989
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
1089
Last page:
1092