Skip to Main Content
Book Chapter

Geology and Rb-Sr Age of Lower Proterozoic granitic rocks, northern Wisconsin

By
P. K. SIMS
P. K. SIMS
Search for other works by this author on:
Z. E. PETERMAN
Z. E. PETERMAN
Search for other works by this author on:
Published:
January 01, 1980

Granitic rocks ranging in composition from granite to tonalite and associated metavolcanic-metasedimentary rocks compose an east-trending belt as much as 180 km wide and 300 km long in northern Wisconsin. The granitic rocks have an initial 87Sr/86Sr of 0.7025 ± 0.0005 and a Rb-Sr whole-rock isochron age of 1,885 ± 65 m.y., which is interpreted as the time of crystallization of the granitic rocks. Rb-Sr whole-rock mineral secondary isochrons for two samples give ages of 1,655 ± 55 m.y. and 1,545 ± 55 m.y.; K-Ar ages of biotite from these samples are 1,615 ± 55 m.y. and 1,598 ± 54 m.y., respectively. These mineral ages are interpreted as resulting from isotopic resetting caused by a thermal event about 1,600 m.y. ago. The granitic rocks and associated metavolcanic-metasedimentary rocks constitute lower Proterozoic greenstone-granite complexes that are remarkably similar in pattern to the Archean greenstone-granite complexes in the Superior province of the Canadian Shield.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Special Papers

Selected Studies of Archean Gneisses and Lower Proterozoic Rocks, Southern Canadian Shield

G. B. Morey
G. B. Morey
Search for other works by this author on:
Gilbert N. Hanson
Gilbert N. Hanson
Search for other works by this author on:
Geological Society of America
Volume
182
ISBN print:
9780813721828
Publication date:
January 01, 1980

References

Related

Citing Books via

Related Articles
Related Book Content
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal