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Petrologic and (super 40) Ar/ (super 39) Ar geochronological constraints on the middle to late Paleozoic thermotectonic history of the southern Connecticut Valley zone, New England Appalachians

David P. Moecher, Michael A. Cosca and Gilbert N. Hanson
Petrologic and (super 40) Ar/ (super 39) Ar geochronological constraints on the middle to late Paleozoic thermotectonic history of the southern Connecticut Valley zone, New England Appalachians
Geological Society of America Bulletin (February 1997) 109 (2): 164-175

Abstract

New (super 40) Ar/ (super 39) Ar data from The Straits Schist and interlayered formations in the southernmost Connecticut Valley zone of the northern Appalachian orogen, together with published (super 40) Ar/ (super 39) Ar and U-Pb data, are used to account for relatively rapid Devonian (post-Acadian) cooling of gneisses and schists near the Waterbury dome and slower Devonian through Permian cooling in structurally higher schists south of the dome. Metamorphic hornblende (super 40) Ar/ (super 39) Ar cooling ages range from 374 Ma 10 km south of the Waterbury dome to 324 Ma 15 to 40 km south of the dome. Muscovite (super 40) Ar/ (super 39) Ar cooling ages also decrease to the south, from 318 to 254 Ma. The ages from the southernmost Connecticut Valley zone are as much as 50 and 100 m.y. younger than hornblende and muscovite, respectively, from the Waterbury dome. The difference in cooling histories between the Waterbury dome and southern Connecticut Valley zone is interpreted to be a result of relatively slower cooling in the southern Connecticut Valley zone following Acadian metamorphism and/or a static Pennsylvanian (Alleghanian) thermal event that reset the muscovite K/Ar system, promoted growth of fine-grained monazite, and resulted in partial melting of the crust beneath the southern Connecticut Valley zone. Such a thermal event would have been contemporaneous with Alleghanian orogenesis in Appalachian terranes in southeastern New England, but the mechanism for generating a Pennsylvanian thermal pulse is still unknown.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 109
Serial Issue: 2
Title: Petrologic and (super 40) Ar/ (super 39) Ar geochronological constraints on the middle to late Paleozoic thermotectonic history of the southern Connecticut Valley zone, New England Appalachians
Affiliation: University of Kentucky, Department of Geological Sciences, Lexington, KY, United States
Pages: 164-175
Published: 199702
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 58
Accession Number: 1997-022071
Categories: GeochronologyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 9701
Illustration Description: illus. incl. 6 tables, geol. sketch map
N41°04'60" - N41°34'60", W73°19'60" - W73°00'00"
Secondary Affiliation: University of Lausanne, Institute for Mineralogy, Lausanne, CHE, SwitzerlandState University of New York at Stony Brook, Department of Earth and Space Sciences, Stony Brook, NY, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199708
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