High-resolution 40Ar/39Ar chronology of multiple intrusion igneous complexes
Foland, K. A. ; Chen, J. -F. ; Linder, J. S. ; Henderson, C. M. B. ; Whillans, I. M.
Springer
Published 1989
Springer
Published 1989
| ISSN: |
1432-0967
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|---|---|
| Source: |
Springer Online Journal Archives 1860-2000
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| Topics: |
Geosciences
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| Notes: |
Abstract The Mount Brome complex of the Monteregian province of southern Quebec, Canada, consits of several major intrusions ranging compositionally from gabbro to syenite. The relative ages of these intrusives have been investigated with high-resolution 40Ar/39Ar analyses, including a specially designed irradiation configuration to cancel the effects of fluence gradients. Small yet distinct apparent age differences are observed. While a number of analytical and geological factors could be proposed to explain the small variations, evaluation of these suggests the age differences reflect those in emplacement times. The gabbro and nepheline diorite were emplaced within a short span 123.1 Ma ago. Generally more evolved lithologies (biotite monzodiorite, pulaskite, nordmarkite) appear to have been emplaced within a restricted interval 1.4±0.3 Ma later. Whole-rock Rb-Sr systematics do not give acceptable isochrons because of significant scatter interpreted to reflect initial 87Sr/86Sr heterogeneities resulting from crustal contamination. Considering the variations in initial ratio, the Rb-Sr data are consistent with the 40Ar/39Ar age.
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| Type of Medium: |
Electronic Resource
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| URL: |