The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites
Abstract The Orestes Melt Zone (OMZ) is a massive contact melt zone (∼20 m thick by several kilometers long), located in the McMurdo Dry Valleys of Antarctica. The OMZ formed at shallow crustal depths by melting of the A-type Orestes Granite owing to intrusion of the underlying, doleritic Basement S...
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croxfordunivpr:10.1093/petrology/egz065 2024-01-28T10:01:43+01:00 The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites Currier, R M Flood, T P National Science Foundation University of Wisconsin Green Bay 2019 http://dx.doi.org/10.1093/petrology/egz065 http://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egz065/31885062/egz065.pdf http://academic.oup.com/petrology/article-pdf/60/11/2077/33557908/egz065.pdf en eng Oxford University Press (OUP) https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model Journal of Petrology volume 60, issue 11, page 2077-2100 ISSN 0022-3530 1460-2415 Geochemistry and Petrology Geophysics journal-article 2019 croxfordunivpr https://doi.org/10.1093/petrology/egz065 2023-12-29T09:29:40Z Abstract The Orestes Melt Zone (OMZ) is a massive contact melt zone (∼20 m thick by several kilometers long), located in the McMurdo Dry Valleys of Antarctica. The OMZ formed at shallow crustal depths by melting of the A-type Orestes Granite owing to intrusion of the underlying, doleritic Basement Sill. The OMZ can be divided broadly into two melting facies. The upper melting facies is distal from the contact and formed by melting at low temperature and water-saturated, or near water-saturated, conditions. The lower melting facies is proximal to the contact and formed by melting at high temperature and water-undersaturated conditions. Separate melting reactions occurred in both of the melting facies, resulting in distinct textures and melt compositions. Melting in the distal facies generated melts with compositions that plot near a predicted eutectic composition. Melting in the proximal facies was accomplished in part by replacement reactions in restitic feldspars. These reactions resulted in the development of plagioclase mantles on both restitic plagioclase and K-feldspar, and melt compositions that diverged from predicted minimum melt along an unexpected path, towards enrichment in orthoclase component. Thermal modeling indicates that this melt zone was active for a minimum of ∼150 years, with a contact temperature of ∼900 °C. Upon cooling, recrystallization generated ocellar textures around restitic quartz, as well as faceted albite as a late-stage product. Observations of the OMZ, combined with thermal modeling, provide new insights into the origin of rapakivi and albite granites. This study has implications for the origin of these two associated granite types in other geological settings. Article in Journal/Newspaper Antarc* Antarctica McMurdo Dry Valleys Oxford University Press (via Crossref) McMurdo Dry Valleys Orestes ENVELOPE(161.917,161.917,-77.467,-77.467) Journal of Petrology 60 11 2077 2100 |
institution |
Open Polar |
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Oxford University Press (via Crossref) |
op_collection_id |
croxfordunivpr |
language |
English |
topic |
Geochemistry and Petrology Geophysics |
spellingShingle |
Geochemistry and Petrology Geophysics Currier, R M Flood, T P The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites |
topic_facet |
Geochemistry and Petrology Geophysics |
description |
Abstract The Orestes Melt Zone (OMZ) is a massive contact melt zone (∼20 m thick by several kilometers long), located in the McMurdo Dry Valleys of Antarctica. The OMZ formed at shallow crustal depths by melting of the A-type Orestes Granite owing to intrusion of the underlying, doleritic Basement Sill. The OMZ can be divided broadly into two melting facies. The upper melting facies is distal from the contact and formed by melting at low temperature and water-saturated, or near water-saturated, conditions. The lower melting facies is proximal to the contact and formed by melting at high temperature and water-undersaturated conditions. Separate melting reactions occurred in both of the melting facies, resulting in distinct textures and melt compositions. Melting in the distal facies generated melts with compositions that plot near a predicted eutectic composition. Melting in the proximal facies was accomplished in part by replacement reactions in restitic feldspars. These reactions resulted in the development of plagioclase mantles on both restitic plagioclase and K-feldspar, and melt compositions that diverged from predicted minimum melt along an unexpected path, towards enrichment in orthoclase component. Thermal modeling indicates that this melt zone was active for a minimum of ∼150 years, with a contact temperature of ∼900 °C. Upon cooling, recrystallization generated ocellar textures around restitic quartz, as well as faceted albite as a late-stage product. Observations of the OMZ, combined with thermal modeling, provide new insights into the origin of rapakivi and albite granites. This study has implications for the origin of these two associated granite types in other geological settings. |
author2 |
National Science Foundation University of Wisconsin Green Bay |
format |
Article in Journal/Newspaper |
author |
Currier, R M Flood, T P |
author_facet |
Currier, R M Flood, T P |
author_sort |
Currier, R M |
title |
The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites |
title_short |
The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites |
title_full |
The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites |
title_fullStr |
The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites |
title_full_unstemmed |
The Orestes Melt Zone, McMurdo Dry Valleys, Antarctica: Spatially Distributed Melting Regimes in a Contact Melt Zone, with Implications for the Formation of Rapakivi and Albite Granites |
title_sort |
orestes melt zone, mcmurdo dry valleys, antarctica: spatially distributed melting regimes in a contact melt zone, with implications for the formation of rapakivi and albite granites |
publisher |
Oxford University Press (OUP) |
publishDate |
2019 |
url |
http://dx.doi.org/10.1093/petrology/egz065 http://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egz065/31885062/egz065.pdf http://academic.oup.com/petrology/article-pdf/60/11/2077/33557908/egz065.pdf |
long_lat |
ENVELOPE(161.917,161.917,-77.467,-77.467) |
geographic |
McMurdo Dry Valleys Orestes |
geographic_facet |
McMurdo Dry Valleys Orestes |
genre |
Antarc* Antarctica McMurdo Dry Valleys |
genre_facet |
Antarc* Antarctica McMurdo Dry Valleys |
op_source |
Journal of Petrology volume 60, issue 11, page 2077-2100 ISSN 0022-3530 1460-2415 |
op_rights |
https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model |
op_doi |
https://doi.org/10.1093/petrology/egz065 |
container_title |
Journal of Petrology |
container_volume |
60 |
container_issue |
11 |
container_start_page |
2077 |
op_container_end_page |
2100 |
_version_ |
1789327046014402560 |