Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite
The ca. 1315 Ma Hosenbein massif-type anorthosite pluton (Nain, Labrador) shows complete exposure of a vertical section, described here for the first time, comprising a ~2000 m-thick Main Zone bound by a ~200 m-thick Marginal Zone. The pluton as a whole consists mostly of monocumulate leucogabbronor...
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Atlantic Geoscience Society
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ftuninewbrunojs:oai:ojs.journals.lib.unb.ca:article/12430 2023-05-15T17:13:58+02:00 Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite Voordouw, Ronald J. 2010-03-10 text/html application/pdf https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003 eng eng Atlantic Geoscience Society https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003/atlgeol.2010.003html https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003/atlgeol.2010.003pdf https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003 Copyright (c) 2015 Atlantic Geology Atlantic Geoscience; Vol. 46 (2010); Pages 19 - 35 2564-2987 Igneous petrology massif anorthosite Nain info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion research-article 2010 ftuninewbrunojs 2022-07-11T11:42:06Z The ca. 1315 Ma Hosenbein massif-type anorthosite pluton (Nain, Labrador) shows complete exposure of a vertical section, described here for the first time, comprising a ~2000 m-thick Main Zone bound by a ~200 m-thick Marginal Zone. The pluton as a whole consists mostly of monocumulate leucogabbronorite, leuconorite, and anortho-site (~94 vol% of all rocks) with elevated abundances of gabbronorite–ferrodiorite (~27 vol%) in the Marginal Zone. Parental magma likely comprised a plagioclase-phyric basaltic melt, containing ~15–45 vol% plagioclase phenocrysts. Crystallization of this magma produced predominantly massive adcumulate–mesocumulate with less abundant, but regular, occurrences of (in order of relative abundance) gabbronorite–ferrodiorite segregations, mottled texture, foliation, pyroxenite aggregates, and modal layering. Additional key petrographic and compositional features include high-T deformation microstructures in plagioclase, vertically consistent mineral compositions, and enrichment of Fe-Ti-P-HFSE-REE in ferrodiorite. Parts of the Marginal Zone show gneissic–mylonitic fabrics that developed parallel to magma conduits. Collectively these features suggest that the textural and structural evolution of the pluton was controlled by: (a) emplacement of plagioclase-phyric magma, (b) establishment of vast cumulus crystal frameworks, (c) porous flow of intercumulus melt, (d) compaction, and (e) synplutonic deformation. These interpretations contrast with previous work emphasizing the importance of magmatic flow and crystal settling/flotation. RÉSUMÉ Un pan vertical des roches d’anorthosite plutonique de Hoseinbein de massif dont la formation remonterait à environ 1 315 Ma (de Nain, au Labrador) semble entièrement exposé et il est décrit ici pour la première fois. Il s’agit en l’occurrence d’une zone principale de plus ou moins 2 000 m d’épaisseur, ceinturée par une zone marginale de plus ou moins 200 m d’épaisseur. Dans son ensemble, la roche plutonique observée se compose principalement de monocumulat de ... Article in Journal/Newspaper Nain University of New Brunswick: Centre for Digital Scholarship Journals Nain ENVELOPE(-61.695,-61.695,56.542,56.542) Atlantic Geology 46 0 19 35 |
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Open Polar |
collection |
University of New Brunswick: Centre for Digital Scholarship Journals |
op_collection_id |
ftuninewbrunojs |
language |
English |
topic |
Igneous petrology massif anorthosite Nain |
spellingShingle |
Igneous petrology massif anorthosite Nain Voordouw, Ronald J. Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite |
topic_facet |
Igneous petrology massif anorthosite Nain |
description |
The ca. 1315 Ma Hosenbein massif-type anorthosite pluton (Nain, Labrador) shows complete exposure of a vertical section, described here for the first time, comprising a ~2000 m-thick Main Zone bound by a ~200 m-thick Marginal Zone. The pluton as a whole consists mostly of monocumulate leucogabbronorite, leuconorite, and anortho-site (~94 vol% of all rocks) with elevated abundances of gabbronorite–ferrodiorite (~27 vol%) in the Marginal Zone. Parental magma likely comprised a plagioclase-phyric basaltic melt, containing ~15–45 vol% plagioclase phenocrysts. Crystallization of this magma produced predominantly massive adcumulate–mesocumulate with less abundant, but regular, occurrences of (in order of relative abundance) gabbronorite–ferrodiorite segregations, mottled texture, foliation, pyroxenite aggregates, and modal layering. Additional key petrographic and compositional features include high-T deformation microstructures in plagioclase, vertically consistent mineral compositions, and enrichment of Fe-Ti-P-HFSE-REE in ferrodiorite. Parts of the Marginal Zone show gneissic–mylonitic fabrics that developed parallel to magma conduits. Collectively these features suggest that the textural and structural evolution of the pluton was controlled by: (a) emplacement of plagioclase-phyric magma, (b) establishment of vast cumulus crystal frameworks, (c) porous flow of intercumulus melt, (d) compaction, and (e) synplutonic deformation. These interpretations contrast with previous work emphasizing the importance of magmatic flow and crystal settling/flotation. RÉSUMÉ Un pan vertical des roches d’anorthosite plutonique de Hoseinbein de massif dont la formation remonterait à environ 1 315 Ma (de Nain, au Labrador) semble entièrement exposé et il est décrit ici pour la première fois. Il s’agit en l’occurrence d’une zone principale de plus ou moins 2 000 m d’épaisseur, ceinturée par une zone marginale de plus ou moins 200 m d’épaisseur. Dans son ensemble, la roche plutonique observée se compose principalement de monocumulat de ... |
format |
Article in Journal/Newspaper |
author |
Voordouw, Ronald J. |
author_facet |
Voordouw, Ronald J. |
author_sort |
Voordouw, Ronald J. |
title |
Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite |
title_short |
Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite |
title_full |
Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite |
title_fullStr |
Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite |
title_full_unstemmed |
Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite |
title_sort |
igneous structure and texture of the ~1.3 ga hosenbein anorthosite pluton (nain, labrador) and implications for the crystallization of massif-type anorthosite |
publisher |
Atlantic Geoscience Society |
publishDate |
2010 |
url |
https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003 |
long_lat |
ENVELOPE(-61.695,-61.695,56.542,56.542) |
geographic |
Nain |
geographic_facet |
Nain |
genre |
Nain |
genre_facet |
Nain |
op_source |
Atlantic Geoscience; Vol. 46 (2010); Pages 19 - 35 2564-2987 |
op_relation |
https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003/atlgeol.2010.003html https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003/atlgeol.2010.003pdf https://journals.lib.unb.ca/index.php/ag/article/view/atlgeol.2010.003 |
op_rights |
Copyright (c) 2015 Atlantic Geology |
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Atlantic Geology |
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46 |
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0 |
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19 |
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35 |
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