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Geology and Rb-Sr age of lower Proterozoic granitic rocks, northern Wisconsin

P. K. Sims and Z. E. Peterman
Geology and Rb-Sr age of lower Proterozoic granitic rocks, northern Wisconsin (in Selected studies of Archean gneisses and lower Proterozoic rocks, southern Canadian Shield, G. B. Morey (editor) and Gilbert N. Hanson (editor))
Special Paper - Geological Society of America (1980) (182): 139-146

Abstract

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 N Wisconsin. The granitic rocks have an initial (super 87) Sr/ (super 86) Sr ratio of 0.7025 + or - 0.0005 and a Rb/Sr isochron age of 1885 + or - 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 1655 + or - 55 m.y. and 1545 + or - 55 m.y.; K/Ar ages of biotite from these samples are 1615 + or - 55 m.y. and 1598 + or - 54 m.y., respectively. These mineral ages are interpreted as resulting from isotopic resetting caused by a thermal event about 1600 m.y. ago.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Issue: 182
Title: Geology and Rb-Sr age of lower Proterozoic granitic rocks, northern Wisconsin
Title: Selected studies of Archean gneisses and lower Proterozoic rocks, southern Canadian Shield
Author(s): Sims, P. K.Peterman, Z. E.
Author(s): Morey, G. B.editor
Author(s): Hanson, Gilbert N.editor
Affiliation: U. S. Geol. Surv., Denver, CO, United States
Affiliation: Minn. Geol. Surv., Saint Paul, MN, United States
Pages: 139-146
Published: 1980
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 0-8137-2182-2
References: 33
Accession Number: 1982-024807
Categories: Geochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 anals., 2 tables, geol. sketch map
N45°00'00" - N46°00'00", W91°00'00" - W89°00'00"
Secondary Affiliation: State Univ. N.Y., USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 1982
Program Name: USGSOPNon-USGS publications with USGS authors
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