A comment on diffusion and the displacement of atoms in metamorphic transformations
Abstract Experimental data on diffusion in olivine , are used to define certain terms – diffusion coefficient, jump frequency, characteristic distance, random walk – that are useful in a discussion of atom displacements under natural conditions. Examples of atom displacements in two metamorphic terr...
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crwiley:10.1111/jmg.12104 2024-06-23T07:57:27+00:00 A comment on diffusion and the displacement of atoms in metamorphic transformations Kretz, R. 2014 http://dx.doi.org/10.1111/jmg.12104 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fjmg.12104 https://onlinelibrary.wiley.com/doi/pdf/10.1111/jmg.12104 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Journal of Metamorphic Geology volume 32, issue 9, page 1005-1017 ISSN 0263-4929 1525-1314 journal-article 2014 crwiley https://doi.org/10.1111/jmg.12104 2024-06-04T06:41:00Z Abstract Experimental data on diffusion in olivine , are used to define certain terms – diffusion coefficient, jump frequency, characteristic distance, random walk – that are useful in a discussion of atom displacements under natural conditions. Examples of atom displacements in two metamorphic terranes of the Canadian Precambrian Shield are then examined, as follows. (i) In a high‐grade metamorphic terrane in the Mid‐Proterozoic Grenville Province (Otter Lake Area), Mg concentration gradients about dolomite microcrystals in calcite and Na gradients about albite microcrystals in K‐feldspar are viewed as stranded Mg–Ca and Na–K interdiffusion gradients, formed by exsolution during slow cooling from ~700 to ~400 °C. (ii) In the Archean Slave Province (Yellowknife area), the crystallization of sillimanite, near andalusite but within crystals of quartz, possibly occurred by coupled Al–Si and oxygen–vacancy interdiffusion in quartz at ~550 °C. And the crystallization of garnet from chlorite occurred by the two‐way crystal‐boundary diffusion of several kinds of atoms across distances ranging to 3 mm. (iii) In the Otter Lake area, the crystallization of orthopyroxene–hornblende–spinel reaction zones at boundaries between crystals of olivine and plagioclase in metagabbro, evidently occurred by the mechanism of interstitial diffusion, that transported Mg, Fe, Mn and O atoms across the reaction zone from olivine to the plagioclase–(hornblende+spinel) boundary, and Si, Al, Ca and Na atoms from plagioclase to the olivine–orthopyroxene boundary, accompanied by NaSi–CaAl interdiffusion in plagioclase, and the addition of hydrogen and minor Ti, Zn, F, Cl and K from beyond the reaction zone. Also, centimetric reaction zones, with abundant biotite and plagioclase, at boundaries between K‐feldspar gneiss and deformed amphibolite dykes, evidently formed by the reaction, strained hornblende (in amphibolite) + K‐feldspar (in gneiss)→biotite (in amphibolite) + plagioclase (in gneiss), with crystal‐boundary diffusion of (Na + Ca) ... Article in Journal/Newspaper Yellowknife Wiley Online Library Nasi ENVELOPE(-23.036,-23.036,66.336,66.336) Yellowknife Journal of Metamorphic Geology 32 9 1005 1017 |
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Abstract Experimental data on diffusion in olivine , are used to define certain terms – diffusion coefficient, jump frequency, characteristic distance, random walk – that are useful in a discussion of atom displacements under natural conditions. Examples of atom displacements in two metamorphic terranes of the Canadian Precambrian Shield are then examined, as follows. (i) In a high‐grade metamorphic terrane in the Mid‐Proterozoic Grenville Province (Otter Lake Area), Mg concentration gradients about dolomite microcrystals in calcite and Na gradients about albite microcrystals in K‐feldspar are viewed as stranded Mg–Ca and Na–K interdiffusion gradients, formed by exsolution during slow cooling from ~700 to ~400 °C. (ii) In the Archean Slave Province (Yellowknife area), the crystallization of sillimanite, near andalusite but within crystals of quartz, possibly occurred by coupled Al–Si and oxygen–vacancy interdiffusion in quartz at ~550 °C. And the crystallization of garnet from chlorite occurred by the two‐way crystal‐boundary diffusion of several kinds of atoms across distances ranging to 3 mm. (iii) In the Otter Lake area, the crystallization of orthopyroxene–hornblende–spinel reaction zones at boundaries between crystals of olivine and plagioclase in metagabbro, evidently occurred by the mechanism of interstitial diffusion, that transported Mg, Fe, Mn and O atoms across the reaction zone from olivine to the plagioclase–(hornblende+spinel) boundary, and Si, Al, Ca and Na atoms from plagioclase to the olivine–orthopyroxene boundary, accompanied by NaSi–CaAl interdiffusion in plagioclase, and the addition of hydrogen and minor Ti, Zn, F, Cl and K from beyond the reaction zone. Also, centimetric reaction zones, with abundant biotite and plagioclase, at boundaries between K‐feldspar gneiss and deformed amphibolite dykes, evidently formed by the reaction, strained hornblende (in amphibolite) + K‐feldspar (in gneiss)→biotite (in amphibolite) + plagioclase (in gneiss), with crystal‐boundary diffusion of (Na + Ca) ... |
format |
Article in Journal/Newspaper |
author |
Kretz, R. |
spellingShingle |
Kretz, R. A comment on diffusion and the displacement of atoms in metamorphic transformations |
author_facet |
Kretz, R. |
author_sort |
Kretz, R. |
title |
A comment on diffusion and the displacement of atoms in metamorphic transformations |
title_short |
A comment on diffusion and the displacement of atoms in metamorphic transformations |
title_full |
A comment on diffusion and the displacement of atoms in metamorphic transformations |
title_fullStr |
A comment on diffusion and the displacement of atoms in metamorphic transformations |
title_full_unstemmed |
A comment on diffusion and the displacement of atoms in metamorphic transformations |
title_sort |
comment on diffusion and the displacement of atoms in metamorphic transformations |
publisher |
Wiley |
publishDate |
2014 |
url |
http://dx.doi.org/10.1111/jmg.12104 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fjmg.12104 https://onlinelibrary.wiley.com/doi/pdf/10.1111/jmg.12104 |
long_lat |
ENVELOPE(-23.036,-23.036,66.336,66.336) |
geographic |
Nasi Yellowknife |
geographic_facet |
Nasi Yellowknife |
genre |
Yellowknife |
genre_facet |
Yellowknife |
op_source |
Journal of Metamorphic Geology volume 32, issue 9, page 1005-1017 ISSN 0263-4929 1525-1314 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/jmg.12104 |
container_title |
Journal of Metamorphic Geology |
container_volume |
32 |
container_issue |
9 |
container_start_page |
1005 |
op_container_end_page |
1017 |
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1802651085947535360 |