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K-Ar age of the Similkameen Batholith and Kruger Alkalic Complex, Washington and British Columbia

Journal of Research of the U.S. Geological Survey
By: , , and 

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Abstract

Twelve K-Ar age determinations from the Similkameen batholith and the contiguous Kruger Alkalic Complex, including seven newly reported here, range from 69.9 m.y. to 177.2 m.y. Ages of coexisting hornblende and biotite show discordancies ranging from about 72 m.y. to 106 m.y., with hornblende consistently showing the greater analytical age. The hornblendes, with one exception, show increasing analytical age with increasing potassium content and approximately fit a 191.0-m.y. 40Ar (radiogenic )/K isochron. The isochron shows a negative intersection with the 40Ar (radiogenic) axis, indicating partial argon loss. The large negative deviation from the isochron of one low-potassium sample suggests that the isochron is biased to older ages. If so, the Similkameen and Kruger rocks probably crystallized between roughly 177 m.y. and 191 m.y. ago. The discordancies between hornblende and coexisting biotite are attributed to argon loss during one or possibly more episodes of thermal metamorphism, the most recent of which was probably between about 50 and 70 m.y. ago. This bracket is based on the age of apparently unmetamorphosed sedimentary deposits containing detritus from the Similkameen and Kruger bodies and the analytical age of the youngest biotite.

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Publication type Article
Publication Subtype Journal Article
Title K-Ar age of the Similkameen Batholith and Kruger Alkalic Complex, Washington and British Columbia
Series title Journal of Research of the U.S. Geological Survey
Volume 3
Issue 1
Year Published 1975
Language English
Publisher U.S. Geological Survey
Description 5 p.
First page 39
Last page 43
Country Canada, United States
State British Columbia, Washington
Other Geospatial Similkameen batholith and the contiguous Kruger Alkalic Complex
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