Pressure, temperature and C-O-H fluid fugacities across the amphibolite-granulite transition, Northwest adirondack mountains, New York

R. Lawrence Edwards; E. J. Essene

doi:10.1093/petrology/29.1.39

Pressure, temperature and C-O-H fluid fugacities across the amphibolite-granulite transition, Northwest adirondack mountains, New York

R. Lawrence Edwards
, E. J. Essene

Earth and Environmental Sciences-Twin Cities

Research output: Contribution to journal › Article › peer-review

45 Scopus citations

Abstract

Pressures, temperatures, water activities (a_H2O) and fugacities of the other C-O-H fluid species have been estimated on a traverse across the amphibolite-granulite facies boundary in the Major Paragneiss, northwest Adirondacks, N.Y. Two-feldspar pairs give temperatures ranging from 650°C in the central portion of the unit to 760°C towards the northeast. Biotite-garnet pairs give erratic temperatures compared to two-feldspar temperatures. This discrepancy appears to be due to retrograde resetting as determined from compositional zoning patterns in biotites and garnets. Some of the discrepancy may also be due to non-ideality of pyrope-almandine mixing or to non-ideality from other components. Pressures ranging from 5·4 kb for the southwestern portion of the unit to 8·0 kb in the northeast were determined from anorthite-grossular-sillimanite-quartz barometry. Minimum pressures ij of 5·8 kb were also determined from coexisting garnet + rutile. Values of a_H2O of 0·08-0·5 estimated from biotite and muscovite dehydration reactions show no correlation with grade. The variability in a_H2O suggests that it is locally controlled and that a homogeneous, pervasive fluid was not present during high grade metamorphism. Graphite equilibria indicate that f_O2 was less than 0·5 log units below QFM and that if a fluid was present, it was rich in CO₂ and H₂O. P-T-a_H2O values suggest that partial melting did not occur during metamorphism. Pervasive flooding with CO₂ does not appear to have occurred. The amphibolite-granulite transition at this locality is characterized by increasing temperature and pressure.

Original language	English (US)
Pages (from-to)	39-72
Number of pages	34
Journal	Journal of Petrology
Volume	29
Issue number	1
DOIs	https://doi.org/10.1093/petrology/29.1.39
State	Published - Feb 1988

Bibliographical note

Funding Information:
We would like to thank S. R. Bohlen and J. W. Valley who assisted in many aspects of this project. This work has been strengthened by discussions with A. L. Albee, E. M. Stolper and V. J. Wall. J. R. Bowman graciously offered to analyze the biotites for H content. Critical reviews by R. J. Arculus, S. K. Sen, R. J. Tracy, S. M. Wickham, and the editor, B. W. Evans, improved the manuscript considerably. We thank W. C. Bigelow who supervises the electron microprobe facilities at the University of Michigan and A. A. Chodos for assistance with microprobe analyses at Caltech. A. H. Gough assisted with fieldwork. The senior author thanks G. J. Wasserburg and A. L. Albee for support in completing this project at Caltech. This project has been supported by NSF grant EAR 78-23568 to E.J.E. and a GSA Penrose Grant (2615-80), a Sigma Xi Grant, a University of Michigan Turner Fund Grant, and an NSF Graduate Fellowship to R.L.E. This is Contribution No. 435 from the Mineralogical Laboratory, University of Michigan and Division Contribution No. 4495 from the California Institute of Technology.

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title = "Pressure, temperature and C-O-H fluid fugacities across the amphibolite-granulite transition, Northwest adirondack mountains, New York",

abstract = "Pressures, temperatures, water activities (aH2O) and fugacities of the other C-O-H fluid species have been estimated on a traverse across the amphibolite-granulite facies boundary in the Major Paragneiss, northwest Adirondacks, N.Y. Two-feldspar pairs give temperatures ranging from 650°C in the central portion of the unit to 760°C towards the northeast. Biotite-garnet pairs give erratic temperatures compared to two-feldspar temperatures. This discrepancy appears to be due to retrograde resetting as determined from compositional zoning patterns in biotites and garnets. Some of the discrepancy may also be due to non-ideality of pyrope-almandine mixing or to non-ideality from other components. Pressures ranging from 5·4 kb for the southwestern portion of the unit to 8·0 kb in the northeast were determined from anorthite-grossular-sillimanite-quartz barometry. Minimum pressures ij of 5·8 kb were also determined from coexisting garnet + rutile. Values of aH2O of 0·08-0·5 estimated from biotite and muscovite dehydration reactions show no correlation with grade. The variability in aH2O suggests that it is locally controlled and that a homogeneous, pervasive fluid was not present during high grade metamorphism. Graphite equilibria indicate that fO2 was less than 0·5 log units below QFM and that if a fluid was present, it was rich in CO2 and H2O. P-T-aH2O values suggest that partial melting did not occur during metamorphism. Pervasive flooding with CO2 does not appear to have occurred. The amphibolite-granulite transition at this locality is characterized by increasing temperature and pressure.",

author = "Edwards, \{R. Lawrence\} and Essene, \{E. J.\}",

note = "Funding Information: We would like to thank S. R. Bohlen and J. W. Valley who assisted in many aspects of this project. This work has been strengthened by discussions with A. L. Albee, E. M. Stolper and V. J. Wall. J. R. Bowman graciously offered to analyze the biotites for H content. Critical reviews by R. J. Arculus, S. K. Sen, R. J. Tracy, S. M. Wickham, and the editor, B. W. Evans, improved the manuscript considerably. We thank W. C. Bigelow who supervises the electron microprobe facilities at the University of Michigan and A. A. Chodos for assistance with microprobe analyses at Caltech. A. H. Gough assisted with fieldwork. The senior author thanks G. J. Wasserburg and A. L. Albee for support in completing this project at Caltech. This project has been supported by NSF grant EAR 78-23568 to E.J.E. and a GSA Penrose Grant (2615-80), a Sigma Xi Grant, a University of Michigan Turner Fund Grant, and an NSF Graduate Fellowship to R.L.E. This is Contribution No. 435 from the Mineralogical Laboratory, University of Michigan and Division Contribution No. 4495 from the California Institute of Technology.",

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doi = "10.1093/petrology/29.1.39",

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AU - Edwards, R. Lawrence

AU - Essene, E. J.

N1 - Funding Information: We would like to thank S. R. Bohlen and J. W. Valley who assisted in many aspects of this project. This work has been strengthened by discussions with A. L. Albee, E. M. Stolper and V. J. Wall. J. R. Bowman graciously offered to analyze the biotites for H content. Critical reviews by R. J. Arculus, S. K. Sen, R. J. Tracy, S. M. Wickham, and the editor, B. W. Evans, improved the manuscript considerably. We thank W. C. Bigelow who supervises the electron microprobe facilities at the University of Michigan and A. A. Chodos for assistance with microprobe analyses at Caltech. A. H. Gough assisted with fieldwork. The senior author thanks G. J. Wasserburg and A. L. Albee for support in completing this project at Caltech. This project has been supported by NSF grant EAR 78-23568 to E.J.E. and a GSA Penrose Grant (2615-80), a Sigma Xi Grant, a University of Michigan Turner Fund Grant, and an NSF Graduate Fellowship to R.L.E. This is Contribution No. 435 from the Mineralogical Laboratory, University of Michigan and Division Contribution No. 4495 from the California Institute of Technology.

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N2 - Pressures, temperatures, water activities (aH2O) and fugacities of the other C-O-H fluid species have been estimated on a traverse across the amphibolite-granulite facies boundary in the Major Paragneiss, northwest Adirondacks, N.Y. Two-feldspar pairs give temperatures ranging from 650°C in the central portion of the unit to 760°C towards the northeast. Biotite-garnet pairs give erratic temperatures compared to two-feldspar temperatures. This discrepancy appears to be due to retrograde resetting as determined from compositional zoning patterns in biotites and garnets. Some of the discrepancy may also be due to non-ideality of pyrope-almandine mixing or to non-ideality from other components. Pressures ranging from 5·4 kb for the southwestern portion of the unit to 8·0 kb in the northeast were determined from anorthite-grossular-sillimanite-quartz barometry. Minimum pressures ij of 5·8 kb were also determined from coexisting garnet + rutile. Values of aH2O of 0·08-0·5 estimated from biotite and muscovite dehydration reactions show no correlation with grade. The variability in aH2O suggests that it is locally controlled and that a homogeneous, pervasive fluid was not present during high grade metamorphism. Graphite equilibria indicate that fO2 was less than 0·5 log units below QFM and that if a fluid was present, it was rich in CO2 and H2O. P-T-aH2O values suggest that partial melting did not occur during metamorphism. Pervasive flooding with CO2 does not appear to have occurred. The amphibolite-granulite transition at this locality is characterized by increasing temperature and pressure.

AB - Pressures, temperatures, water activities (aH2O) and fugacities of the other C-O-H fluid species have been estimated on a traverse across the amphibolite-granulite facies boundary in the Major Paragneiss, northwest Adirondacks, N.Y. Two-feldspar pairs give temperatures ranging from 650°C in the central portion of the unit to 760°C towards the northeast. Biotite-garnet pairs give erratic temperatures compared to two-feldspar temperatures. This discrepancy appears to be due to retrograde resetting as determined from compositional zoning patterns in biotites and garnets. Some of the discrepancy may also be due to non-ideality of pyrope-almandine mixing or to non-ideality from other components. Pressures ranging from 5·4 kb for the southwestern portion of the unit to 8·0 kb in the northeast were determined from anorthite-grossular-sillimanite-quartz barometry. Minimum pressures ij of 5·8 kb were also determined from coexisting garnet + rutile. Values of aH2O of 0·08-0·5 estimated from biotite and muscovite dehydration reactions show no correlation with grade. The variability in aH2O suggests that it is locally controlled and that a homogeneous, pervasive fluid was not present during high grade metamorphism. Graphite equilibria indicate that fO2 was less than 0·5 log units below QFM and that if a fluid was present, it was rich in CO2 and H2O. P-T-aH2O values suggest that partial melting did not occur during metamorphism. Pervasive flooding with CO2 does not appear to have occurred. The amphibolite-granulite transition at this locality is characterized by increasing temperature and pressure.

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Pressure, temperature and C-O-H fluid fugacities across the amphibolite-granulite transition, Northwest adirondack mountains, New York

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