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Title: Geothermobarometry of Precambrian metamorphic rocks from the Tobacco Root Mountains of southwestern Montana

Abstract

Upper amphibolite facies metamorphic rocks of Precambrian age, located in the Spuhler Peak area of the Tobacco Root Mountains of southwestern Montana, provide the basis for comparative geothermobarometry. Twenty three samples were chosen for microprobe analyses from a stratified sequence of metapelites interlayered with amphibole schists and gneisses exposed in a cirque headwall (less than one square mile sampling area). The garnet-biotite geothermometry of Indares and Martignole (1985), for three metapelite samples, indicates an average temperature 710 [+-] 35 C at a pressure of 6,530 bars (one sample) using the modified GASP geobarometer of Newton and Haselton (1981). Geothermobarometry on the amphibole schist and gneiss samples using the hornblende-plagioclase geothermometer of Blundy and Holland (1990), for twenty samples, indicates an average temperature of 751 [+-] 47 C. The hornblende-garnet geothermometer of Graham and Powell (1984), for fifteen samples, indicates an average temperature of 628 [+-] 59 C. The total aluminum content of hornblendes from nineteen samples indicates an average pressure of 4,826 [+-] 682 bars (Johnson and Rutherford, 1988) and 6,182 [+-] 793 bars (Blundy and Holland, 1990). Variation of temperature and pressure may be explained by closure temperatures for element exchange between the minerals used in the various geothermobarometers.

Authors:
 [1]
  1. Univ. of Akron, OH (United States). Dept. of Geology
Publication Date:
OSTI Identifier:
7140931
Report Number(s):
CONF-9404217-
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: 26:5; Conference: 27. annual conference of the North-Central Section of the Geological Society of America (GSA), Kalamazoo, MI (United States), 28-29 Apr 1994; Journal ID: ISSN 0016-7592
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; AMPHIBOLITES; GEOBAROMETRY; GEOTHERMOMETRY; GEOLOGIC DEPOSITS; MONTANA; GEOLOGIC HISTORY; DEVELOPED COUNTRIES; METAMORPHIC ROCKS; NORTH AMERICA; ROCKS; USA; 580000* - Geosciences

Citation Formats

Friberg, L M. Geothermobarometry of Precambrian metamorphic rocks from the Tobacco Root Mountains of southwestern Montana. United States: N. p., 1994. Web.
Friberg, L M. Geothermobarometry of Precambrian metamorphic rocks from the Tobacco Root Mountains of southwestern Montana. United States.
Friberg, L M. 1994. "Geothermobarometry of Precambrian metamorphic rocks from the Tobacco Root Mountains of southwestern Montana". United States.
@article{osti_7140931,
title = {Geothermobarometry of Precambrian metamorphic rocks from the Tobacco Root Mountains of southwestern Montana},
author = {Friberg, L M},
abstractNote = {Upper amphibolite facies metamorphic rocks of Precambrian age, located in the Spuhler Peak area of the Tobacco Root Mountains of southwestern Montana, provide the basis for comparative geothermobarometry. Twenty three samples were chosen for microprobe analyses from a stratified sequence of metapelites interlayered with amphibole schists and gneisses exposed in a cirque headwall (less than one square mile sampling area). The garnet-biotite geothermometry of Indares and Martignole (1985), for three metapelite samples, indicates an average temperature 710 [+-] 35 C at a pressure of 6,530 bars (one sample) using the modified GASP geobarometer of Newton and Haselton (1981). Geothermobarometry on the amphibole schist and gneiss samples using the hornblende-plagioclase geothermometer of Blundy and Holland (1990), for twenty samples, indicates an average temperature of 751 [+-] 47 C. The hornblende-garnet geothermometer of Graham and Powell (1984), for fifteen samples, indicates an average temperature of 628 [+-] 59 C. The total aluminum content of hornblendes from nineteen samples indicates an average pressure of 4,826 [+-] 682 bars (Johnson and Rutherford, 1988) and 6,182 [+-] 793 bars (Blundy and Holland, 1990). Variation of temperature and pressure may be explained by closure temperatures for element exchange between the minerals used in the various geothermobarometers.},
doi = {},
url = {https://www.osti.gov/biblio/7140931}, journal = {Geological Society of America, Abstracts with Programs; (United States)},
issn = {0016-7592},
number = ,
volume = 26:5,
place = {United States},
year = {Fri Apr 01 00:00:00 EST 1994},
month = {Fri Apr 01 00:00:00 EST 1994}
}

Conference:
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