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Title: Multiple generations of monazite growth in metapelites of the Wepawaug Schist, southern Connecticut

Abstract

The Wepawaug Schist, part of the Orange Milford Belt of southern Connecticut, consists dominantly of micaceous phyllites and schists. A progression in metamorphic zonation from chlorite through kyanite grade occurs within 3 km. There were previously no constraints on either the depositional age of the Wepawaug Schist or the time of metamorphism. Concordant U-Pb sphene ages of 457 [+-] 3 Ma for the Woodbridge granite, which cuts the Wepawaug Schist, mean that the metapelites are older than late Ordovician. Kyanite grade rocks contain two distinct monazite populations within a single outcrop: (1) Crystals from a graphitic schist are clear, round, and xenoblastic. They have [approximately]0.9 wt.% Th, Sm/Nd = 0.12--0.14, and display pronounced chemical zonation. These give normality discordant U-Pb ages that define an upper intercept age of 420 [+-] 12 Ma. (2) In a less graphitic schist they are light yellow, idioblastic, tabular crystals that cut muscovites. They have Sm/Nd = 0.16 and [approximately] 2.6 wt.% Th and give concordant U-Pb ages of 377 [+-] 3 Ma. The authors suggest that the Wepawaug Schist is older than 457 Ma and was affected by two events which resulted in monazite growth, one during the Middle Devonian (377 Ma) and onemore » in the Late Silurian (420 Ma).« less

Authors:
;  [1]
  1. State Univ. of New York, Stony Brook, NY (United States). Dept. of Earth and Space Sciences
Publication Date:
OSTI Identifier:
5809438
Report Number(s):
CONF-921058-
Journal ID: ISSN 0016-7592; CODEN: GAAPBC
Resource Type:
Conference
Journal Name:
Geological Society of America, Abstracts with Programs; (United States)
Additional Journal Information:
Journal Volume: 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; Journal ID: ISSN 0016-7592
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CONNECTICUT; GEOLOGIC FORMATIONS; AGE ESTIMATION; METAMORPHISM; DEVONIAN PERIOD; ISOTOPE DATING; LEAD; MONAZITES; SCHISTS; SILURIAN PERIOD; URANIUM; ACTINIDES; DEVELOPED COUNTRIES; ELEMENTS; GEOLOGIC AGES; MATERIALS; METALS; METAMORPHIC ROCKS; MINERALS; NORTH AMERICA; PALEOZOIC ERA; PHOSPHATE MINERALS; RADIOACTIVE MATERIALS; RADIOACTIVE MINERALS; RARE EARTH COMPOUNDS; ROCKS; THORIUM MINERALS; USA; 580000* - Geosciences

Citation Formats

Lanzirotti, A, and Hanson, G N. Multiple generations of monazite growth in metapelites of the Wepawaug Schist, southern Connecticut. United States: N. p., 1992. Web.
Lanzirotti, A, & Hanson, G N. Multiple generations of monazite growth in metapelites of the Wepawaug Schist, southern Connecticut. United States.
Lanzirotti, A, and Hanson, G N. 1992. "Multiple generations of monazite growth in metapelites of the Wepawaug Schist, southern Connecticut". United States.
@article{osti_5809438,
title = {Multiple generations of monazite growth in metapelites of the Wepawaug Schist, southern Connecticut},
author = {Lanzirotti, A and Hanson, G N},
abstractNote = {The Wepawaug Schist, part of the Orange Milford Belt of southern Connecticut, consists dominantly of micaceous phyllites and schists. A progression in metamorphic zonation from chlorite through kyanite grade occurs within 3 km. There were previously no constraints on either the depositional age of the Wepawaug Schist or the time of metamorphism. Concordant U-Pb sphene ages of 457 [+-] 3 Ma for the Woodbridge granite, which cuts the Wepawaug Schist, mean that the metapelites are older than late Ordovician. Kyanite grade rocks contain two distinct monazite populations within a single outcrop: (1) Crystals from a graphitic schist are clear, round, and xenoblastic. They have [approximately]0.9 wt.% Th, Sm/Nd = 0.12--0.14, and display pronounced chemical zonation. These give normality discordant U-Pb ages that define an upper intercept age of 420 [+-] 12 Ma. (2) In a less graphitic schist they are light yellow, idioblastic, tabular crystals that cut muscovites. They have Sm/Nd = 0.16 and [approximately] 2.6 wt.% Th and give concordant U-Pb ages of 377 [+-] 3 Ma. The authors suggest that the Wepawaug Schist is older than 457 Ma and was affected by two events which resulted in monazite growth, one during the Middle Devonian (377 Ma) and one in the Late Silurian (420 Ma).},
doi = {},
url = {https://www.osti.gov/biblio/5809438}, journal = {Geological Society of America, Abstracts with Programs; (United States)},
issn = {0016-7592},
number = ,
volume = 24:7,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1992},
month = {Wed Jan 01 00:00:00 EST 1992}
}

Conference:
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