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40Ar/39Ar and K-Ar data bearing on the metamorphic and tectonic history of western New England.

Geological Society of America Bulletin

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Abstract

40Ar/39Ar ages of coexisting biotite and hornblende from Proterozoic Y gneisses of the Berkshire and Green Mt massifs, as well as 40Ar/39Ar and K/Ar mineral and whole-rock ages from Palaeozoic metamorphic rocks, suggest that the thermal peaks for the dominant metamorphic recrystallization in western New England occurred 465 + or - 5 m.y. (Taconian). 40Ar/39Ar age data from a poorly-defined terrain along the eastern strip of the area suggests that the area has been retrograded during a metamorphism that peaked at least 376 + or - 5 m.y. (Acadian). Available age and petrological data from western New England indicate the presence of at least three separate metamorphic-structure domains of Taconic age: 1) a small area of relict high-P and low-T metamorphism, 2) a broad area of normal Barrovian metamorphism from chlorite to garnet grade characterized by a gentle metamorphic gradient and, 3) a rather narrow belt of steep-gradient, Barrovian series metamorphic rocks. Areas of maximum metamorphic intensity within the last domain coincide with areas of maximum crustal thickening in the later stage of Taconic orogeny. -L.di H

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
40Ar/39Ar and K-Ar data bearing on the metamorphic and tectonic history of western New England.
Series title:
Geological Society of America Bulletin
Volume
96
Issue:
1
Year Published:
1985
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geological Society of America Bulletin
First page:
123
Last page:
136
Number of Pages:
14