Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica
In the Pan-African belt of the Dronning Maud Land, Antarctica, crystallized melt inclusions (nanogranitoids) occur in garnet from ultramafic granulites. The granulites contain the peak assemblage pargasite+garnet+clinopyroxene with rare relict orthopyroxene and biotite, and retrograde symplectites a...
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ftubpotsdam:oai:kobv.de-opus4-uni-potsdam:53173 2023-05-15T13:48:06+02:00 Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica Ferrero, Silvio (Dr.) Godard, Gaston Palmeri, Rosaria Wunder, Bernd (Dr.) Cesare, Bernardo 2018-04-25 https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/53173 https://doi.org/10.2138/am-2018-6214 eng eng https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/53173 https://doi.org/10.2138/am-2018-6214 info:eu-repo/semantics/closedAccess ddc:550 Institut für Geowissenschaften article doc-type:article 2018 ftubpotsdam https://doi.org/10.2138/am-2018-6214 2022-07-28T20:51:10Z In the Pan-African belt of the Dronning Maud Land, Antarctica, crystallized melt inclusions (nanogranitoids) occur in garnet from ultramafic granulites. The granulites contain the peak assemblage pargasite+garnet+clinopyroxene with rare relict orthopyroxene and biotite, and retrograde symplectites at contacts between garnet and amphibole. Garnet contains two generations of melt inclusions. Type 1 inclusions, interpreted as primary, are isolated, < 10 mu m in size, and generally have negative crystal shapes. They contain kokchetavite, kumdykolite, and phlogopite, with quartz and zoisite as minor phases, and undevitrified glass was identified in one inclusion. Type 2 inclusions are < 30 mu m in size, secondary, and contain amphibole, feldspars, and zoisite. Type 2 inclusions appear to be the crystallization products of a melt that coexisted with an immiscible CO2-rich fluid. The nanogranitoids were re-homogenized after heating in a piston-cylinder in a series of four experiments to investigate their composition. The conditions ranged between 900 and 950 degrees C at 1.5-2.4 GPa. Type 1 inclusions are trachytic and ultrapotassic, whereas type 2 melts are dacitic to rhyolitic. Thermodynamic modeling of the ultramafic composition in the MnNCKFMASHTO system shows that anatexis occurred at the end of the prograde P-T path, between the solidus (at ca. 860 degrees C-1.4 GPa) and the peak conditions (at ca. 960 degrees C-1.7 GPa). The model melt composition is felsic and similar to that of type 1 inclusions, particularly when the melting degree is low (< 1 mol%), close to the solidus. However the modeling fails to reproduce the highly potassic signature of the melt and its low H2O content. The combination of petrology, melt inclusion study, and thermodynamic modeling supports the interpretation that melt was produced by anatexis of the ultramafic boudins near peak P-T conditions, and that type 1 inclusions contain the anatectic melt that was present during garnet growth. The felsic, ultrapotassic composition of ... Article in Journal/Newspaper Antarc* Antarctica Dronning Maud Land University of Potsdam: publish.UP Dronning Maud Land American Mineralogist 103 4 610 622 |
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University of Potsdam: publish.UP |
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ftubpotsdam |
language |
English |
topic |
ddc:550 Institut für Geowissenschaften |
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ddc:550 Institut für Geowissenschaften Ferrero, Silvio (Dr.) Godard, Gaston Palmeri, Rosaria Wunder, Bernd (Dr.) Cesare, Bernardo Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica |
topic_facet |
ddc:550 Institut für Geowissenschaften |
description |
In the Pan-African belt of the Dronning Maud Land, Antarctica, crystallized melt inclusions (nanogranitoids) occur in garnet from ultramafic granulites. The granulites contain the peak assemblage pargasite+garnet+clinopyroxene with rare relict orthopyroxene and biotite, and retrograde symplectites at contacts between garnet and amphibole. Garnet contains two generations of melt inclusions. Type 1 inclusions, interpreted as primary, are isolated, < 10 mu m in size, and generally have negative crystal shapes. They contain kokchetavite, kumdykolite, and phlogopite, with quartz and zoisite as minor phases, and undevitrified glass was identified in one inclusion. Type 2 inclusions are < 30 mu m in size, secondary, and contain amphibole, feldspars, and zoisite. Type 2 inclusions appear to be the crystallization products of a melt that coexisted with an immiscible CO2-rich fluid. The nanogranitoids were re-homogenized after heating in a piston-cylinder in a series of four experiments to investigate their composition. The conditions ranged between 900 and 950 degrees C at 1.5-2.4 GPa. Type 1 inclusions are trachytic and ultrapotassic, whereas type 2 melts are dacitic to rhyolitic. Thermodynamic modeling of the ultramafic composition in the MnNCKFMASHTO system shows that anatexis occurred at the end of the prograde P-T path, between the solidus (at ca. 860 degrees C-1.4 GPa) and the peak conditions (at ca. 960 degrees C-1.7 GPa). The model melt composition is felsic and similar to that of type 1 inclusions, particularly when the melting degree is low (< 1 mol%), close to the solidus. However the modeling fails to reproduce the highly potassic signature of the melt and its low H2O content. The combination of petrology, melt inclusion study, and thermodynamic modeling supports the interpretation that melt was produced by anatexis of the ultramafic boudins near peak P-T conditions, and that type 1 inclusions contain the anatectic melt that was present during garnet growth. The felsic, ultrapotassic composition of ... |
format |
Article in Journal/Newspaper |
author |
Ferrero, Silvio (Dr.) Godard, Gaston Palmeri, Rosaria Wunder, Bernd (Dr.) Cesare, Bernardo |
author_facet |
Ferrero, Silvio (Dr.) Godard, Gaston Palmeri, Rosaria Wunder, Bernd (Dr.) Cesare, Bernardo |
author_sort |
Ferrero, Silvio (Dr.) |
title |
Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica |
title_short |
Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica |
title_full |
Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica |
title_fullStr |
Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica |
title_full_unstemmed |
Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica |
title_sort |
partial melting of ultramafic granulites from dronning maud land, antarctica |
publishDate |
2018 |
url |
https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/53173 https://doi.org/10.2138/am-2018-6214 |
geographic |
Dronning Maud Land |
geographic_facet |
Dronning Maud Land |
genre |
Antarc* Antarctica Dronning Maud Land |
genre_facet |
Antarc* Antarctica Dronning Maud Land |
op_relation |
https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/53173 https://doi.org/10.2138/am-2018-6214 |
op_rights |
info:eu-repo/semantics/closedAccess |
op_doi |
https://doi.org/10.2138/am-2018-6214 |
container_title |
American Mineralogist |
container_volume |
103 |
container_issue |
4 |
container_start_page |
610 |
op_container_end_page |
622 |
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1766248581645205504 |