Progressive low pressure metamorphism of metapelitic rocks from the Casco Bay area, southwestern Maine

Grover, T W; Lang, H M; Gordon, T M

Title: Progressive low pressure metamorphism of metapelitic rocks from the Casco Bay area, southwestern Maine

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Abstract

A prograde sequence of metapelitic rocks occurs in the Casco Bay area, southwestern Maine. Excellent exposure along the coast of Orrs Island, Harpswell Neck, and Small Point have allowed for the delineation of several metamorphic zones which show an increase in metamorphic grade from west to east across the area. These zones are, in order of increasing metamorphic grade, a garnet zone, a staurolite zone, a staurolite + andalusite zone and a sillimanite [plus minus] andalusite [plus minus] staurolite zone. The widespread occurrence of coexisting andalusite + sillimanite in the highest grade portion of the area, along with the presence of andalusite [plus minus] sillimanite veins on Hermit Island suggest peak metamorphism was near the andalusite-sillimanite transition. Staurolite is also found in apparent textural equilibrium in many of the sillimanite-bearing samples. Metamorphic pressures and temperatures were determined using the approach of Gordon. Peak temperatures range from [approx] 440C in garnet zone rocks to [approx] 510C in sillimanite [plus minus] andalusite zone rocks. Metamorphic pressures are [approx] 3-3.5 kbars. These P-T estimates are consistent with those determined using GeO-Calc. In contrast with the static style of metamorphism reported in central and western Maine, metamorphism in the Casco Bay area, located eastmore »« less

Authors:

Grover, T W ^[1]; Lang, H M ^[2]; Gordon, T M ^[1]

Univ. of Calgary, Alberta (Canada). Dept. of Geology and Geophysics
West Virginia Univ., Morgantown, WV (United States). Dept. of Geology and Geography

Publication Date:: Mon Mar 01 00:00:00 EST 1993

OSTI Identifier:: 5934672

Report Number(s):: CONF-9303211-
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: 25:2; Conference: 28. annual Geological Society of America (GSA) Northeastern Section meeting, Burlington, VT (United States), 22-24 Mar 1993; Journal ID: ISSN 0016-7592

Country of Publication:: United States

Language:: English

Subject:: 58 GEOSCIENCES; GEOLOGIC DEPOSITS; GEOBAROMETRY; GEOTHERMOMETRY; PARAGENESIS; MAINE; METAMORPHIC ROCKS; BAYS; DEFORMATION; GARNETS; GEOLOGIC HISTORY; METAMORPHISM; MINERALOGY; PETROGENESIS; COASTAL WATERS; DEVELOPED COUNTRIES; GEOLOGY; MINERALS; NORTH AMERICA; OXYGEN COMPOUNDS; PETROLOGY; ROCKS; SILICATE MINERALS; SILICATES; SILICON COMPOUNDS; SURFACE WATERS; USA; 580000* - Geosciences

Citation Formats


                    Grover, T W, Lang, H M, and Gordon, T M. Progressive low pressure metamorphism of metapelitic rocks from the Casco Bay area, southwestern Maine.  United States: N. p., 1993. 
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                    Grover, T W, Lang, H M, & Gordon, T M. Progressive low pressure metamorphism of metapelitic rocks from the Casco Bay area, southwestern Maine.  United States.

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                    Grover, T W, Lang, H M, and Gordon, T M. 1993.  
        "Progressive low pressure metamorphism of metapelitic rocks from the Casco Bay area, southwestern Maine".  United States.

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@article{osti_5934672,

  title        = {Progressive low pressure metamorphism of metapelitic rocks from the Casco Bay area, southwestern Maine},

  author       = {Grover, T W and Lang, H M and Gordon, T M},

  abstractNote = {A prograde sequence of metapelitic rocks occurs in the Casco Bay area, southwestern Maine. Excellent exposure along the coast of Orrs Island, Harpswell Neck, and Small Point have allowed for the delineation of several metamorphic zones which show an increase in metamorphic grade from west to east across the area. These zones are, in order of increasing metamorphic grade, a garnet zone, a staurolite zone, a staurolite + andalusite zone and a sillimanite [plus minus] andalusite [plus minus] staurolite zone. The widespread occurrence of coexisting andalusite + sillimanite in the highest grade portion of the area, along with the presence of andalusite [plus minus] sillimanite veins on Hermit Island suggest peak metamorphism was near the andalusite-sillimanite transition. Staurolite is also found in apparent textural equilibrium in many of the sillimanite-bearing samples. Metamorphic pressures and temperatures were determined using the approach of Gordon. Peak temperatures range from [approx] 440C in garnet zone rocks to [approx] 510C in sillimanite [plus minus] andalusite zone rocks. Metamorphic pressures are [approx] 3-3.5 kbars. These P-T estimates are consistent with those determined using GeO-Calc. In contrast with the static style of metamorphism reported in central and western Maine, metamorphism in the Casco Bay area, located east of the Norumbega Fault, was synchronous with deformation. The same sequence of porphyroblast growth reported for the Orrs Island-Harpswell Neck area is also found in the Small Point area, suggesting the same metamorphic event affected the entire region. However, coarse grained muscovite pseudomorphs after andalusite or staurolite in rocks with stable andalusite and staurolite are found in the Small Point area suggesting these rocks have a polymetamorphic history. Evidence for polymetamorphism is not found elsewhere in the area.},

  doi          = {},

  url          = {https://www.osti.gov/biblio/5934672},
  journal      = {Geological Society of America, Abstracts with Programs; (United States)},

  issn         = {0016-7592},

  number       = ,

  volume       = 25:2,

  place        = {United States},

  year         = {Mon Mar 01 00:00:00 EST 1993},

  month        = {Mon Mar 01 00:00:00 EST 1993}

}

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