Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer
Abstract Mafic phyllosilicates in metabasites affected by low‐grade regional metamorphism from Wales and eastern North Greenland show variations in their structure and chemistry. These variations are related to four mineral zones in these metabasites, which are recognized on the presence/absence of...
Published in: | Journal of Metamorphic Geology |
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crwiley:10.1111/j.1525-1314.1991.tb00560.x 2024-09-15T18:10:01+00:00 Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer BEVINS, R. E. ROBINSON, D. ROWBOTHAM, G. 1991 http://dx.doi.org/10.1111/j.1525-1314.1991.tb00560.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1991.tb00560.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1991.tb00560.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Journal of Metamorphic Geology volume 9, issue 6, page 711-721 ISSN 0263-4929 1525-1314 journal-article 1991 crwiley https://doi.org/10.1111/j.1525-1314.1991.tb00560.x 2024-07-09T04:10:17Z Abstract Mafic phyllosilicates in metabasites affected by low‐grade regional metamorphism from Wales and eastern North Greenland show variations in their structure and chemistry. These variations are related to four mineral zones in these metabasites, which are recognized on the presence/absence of various key calc‐silicate minerals and also actinolite. Zones 1 and 2 equate with the zeolite facies, zone 3 with the prehnite–pumpellyite facies (or prehnite–actinolite facies in rocks with appropriate bulk rock composition) and zone 4 with the greenschist facies. Whilst variations in Fe/(Fe + Mg) in chlorite correlate closely with Fe/(Fe + Mg) ratios in the whole‐rock, other chemical variations are clearly unrelated to whole‐rock compositions. Contents of Al iv are seen to increase systematically in samples from zone 1 through to zone 4, which relate to an increase in temperature. Calibration of alteration temperatures, calculated using the chlorite geothermometer (based on Al iv contents) developed for meta‐andesites in the Los Azufres geothermal system (Mexico), against x values (an estimate of the proportion of chlorite to swelling component in the mafic phyllosilicates) shows a decrease in the swelling component in passing from zone 1 to zone 4, i.e. with an increase in temperature. Calculated temperatures compare favourably with published stability estimates for the various key calc‐silicates and actinolite. These data indicate that the chlorite geothermometer, although developed for meta‐andesites from a hydrothermal system, does show a correlation with temperatures estimated from calc‐silicate assemblages in metabasites affected by low‐grade metamorphism developed on a regional scale. Article in Journal/Newspaper Greenland North Greenland Wiley Online Library Journal of Metamorphic Geology 9 6 711 721 |
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Abstract Mafic phyllosilicates in metabasites affected by low‐grade regional metamorphism from Wales and eastern North Greenland show variations in their structure and chemistry. These variations are related to four mineral zones in these metabasites, which are recognized on the presence/absence of various key calc‐silicate minerals and also actinolite. Zones 1 and 2 equate with the zeolite facies, zone 3 with the prehnite–pumpellyite facies (or prehnite–actinolite facies in rocks with appropriate bulk rock composition) and zone 4 with the greenschist facies. Whilst variations in Fe/(Fe + Mg) in chlorite correlate closely with Fe/(Fe + Mg) ratios in the whole‐rock, other chemical variations are clearly unrelated to whole‐rock compositions. Contents of Al iv are seen to increase systematically in samples from zone 1 through to zone 4, which relate to an increase in temperature. Calibration of alteration temperatures, calculated using the chlorite geothermometer (based on Al iv contents) developed for meta‐andesites in the Los Azufres geothermal system (Mexico), against x values (an estimate of the proportion of chlorite to swelling component in the mafic phyllosilicates) shows a decrease in the swelling component in passing from zone 1 to zone 4, i.e. with an increase in temperature. Calculated temperatures compare favourably with published stability estimates for the various key calc‐silicates and actinolite. These data indicate that the chlorite geothermometer, although developed for meta‐andesites from a hydrothermal system, does show a correlation with temperatures estimated from calc‐silicate assemblages in metabasites affected by low‐grade metamorphism developed on a regional scale. |
format |
Article in Journal/Newspaper |
author |
BEVINS, R. E. ROBINSON, D. ROWBOTHAM, G. |
spellingShingle |
BEVINS, R. E. ROBINSON, D. ROWBOTHAM, G. Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer |
author_facet |
BEVINS, R. E. ROBINSON, D. ROWBOTHAM, G. |
author_sort |
BEVINS, R. E. |
title |
Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer |
title_short |
Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer |
title_full |
Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer |
title_fullStr |
Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer |
title_full_unstemmed |
Compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer |
title_sort |
compositional variations in mafic phyllosilicates from regional low‐grade metabasites and application of the chlorite geothermometer |
publisher |
Wiley |
publishDate |
1991 |
url |
http://dx.doi.org/10.1111/j.1525-1314.1991.tb00560.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1991.tb00560.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1991.tb00560.x |
genre |
Greenland North Greenland |
genre_facet |
Greenland North Greenland |
op_source |
Journal of Metamorphic Geology volume 9, issue 6, page 711-721 ISSN 0263-4929 1525-1314 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/j.1525-1314.1991.tb00560.x |
container_title |
Journal of Metamorphic Geology |
container_volume |
9 |
container_issue |
6 |
container_start_page |
711 |
op_container_end_page |
721 |
_version_ |
1810447613253648384 |