Textural and Rb-Sr isotopic evidence for late Paleozoic mylonitization within the Honey Hill fault zone southeastern Connecticut

Journal Article · Thu Sep 01 04:00:00 EDT 1983 · Am. J. Sci.; (United States)

DOI:https://doi.org/10.2475/ajs.283.7.762· OSTI ID:6481007

O'Hara, K D; Gromet, L P

A petrographic and Rb-Sr isotopic study of rocks within and near the Honey Hill fault zone places important constraints on its history of movement. Rb-Sr apparent ages for micas and plagioclase from these rocks have been reset and range from Permian to Triassic, considerably younger than the minimum stratigraphic age (Ordovician) of the rocks studied or of Acadian (Devonian) regional metamorphism. Permian Rb-Sr ages of dynamically recrystallized muscovite date the development of mylonite fabric. An older age is precluded by the excellent preservation of unrecovered quartz, which indicates that these rocks did not experience temperatures high enough to anneal quartz or thermally reset Rb-Sr isotopic systems in muscovite since the time of mylonitization. Metamorphic mineral assemblages and mineral apparent ages in rocks north of the fault zone indicate recrystallization under similar upper greenschist-lower amphibolite grade conditions during Permian to Triassic time. Collectively these results indicate that the Honey Hill fault zone was active during the Late Paleozoic and that ductile deformation and metamorphism associated with the Alleghanian orogeny extend well into southern Connecticut. An Alleghanian age for mylonitization within the Honey Hill fault zone suggests it should be considered as a possible site for the major Late Paleozoic strike-slip displacements inferred from paleomagnetic studies for parts of coastal New England and maritime Canada.

• Research Organization: Brown Univ., Providence, RI
• OSTI ID: 6481007
• Journal Information: Am. J. Sci.; (United States), Journal Name: Am. J. Sci.; (United States) Vol. 283:7; ISSN AJSCA
• Country of Publication: United States
• Language: English

Related Subjects

510101* -- Environment
Terrestrial-- Basic Studies-- Radiometric Techniques-- (-1989)
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
580100 -- Geology & Hydrology-- (-1989)
580300 -- Mineralogy
Petrology
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AGE ESTIMATION
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMISTRY
CONNECTICUT
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION I
GEOCHEMISTRY
GEOLOGIC AGES
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
MAGNETISM
METAMORPHIC ROCKS
NORTH AMERICA
NUCLEI
ODD-EVEN NUCLEI
OROGENESIS
PALEOMAGNETISM
PALEOZOIC ERA
PETROGRAPHY
RADIOISOTOPES
ROCKS
RUBIDIUM 87
RUBIDIUM ISOTOPES
STABLE ISOTOPES
STRONTIUM 80
STRONTIUM 86
STRONTIUM 87
STRONTIUM ISOTOPES
TECTONICS
USA
YEARS LIVING RADIOISOTOPES