Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite

Magmatic Na-rich phlogopite (1–5 wt% Na2O) is present as a late-crystallizing mineral in two groups of texturally and mineralogically distinct gabbroic xenoliths at Volcán San Pedro (36°S, Chile), an Andean arc volcano. Phlogopites are characterized by high 100·Mg/(Mg + Fe) (up to 83) and high Cr2O3...

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Main Authors: Costa, Fidel, Dungan, Michael, Singer, Brad S.
Other Authors: School of Physical and Mathematical Sciences
Format: Article
Language:English
Published: 2012
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Online Access:https://hdl.handle.net/10356/95483
http://hdl.handle.net/10220/8721
http://ammin.geoscienceworld.org.ezlibproxy1.ntu.edu.sg/content/86/1-2.toc
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spelling sg-ntu-dr.10356-954832019-12-06T19:15:48Z Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite Costa, Fidel Dungan, Michael Singer, Brad S. School of Physical and Mathematical Sciences DRNTU::Science::Geology Magmatic Na-rich phlogopite (1–5 wt% Na2O) is present as a late-crystallizing mineral in two groups of texturally and mineralogically distinct gabbroic xenoliths at Volcán San Pedro (36°S, Chile), an Andean arc volcano. Phlogopites are characterized by high 100·Mg/(Mg + Fe) (up to 83) and high Cr2O3 contents (up to 0.4 wt%), and they are always found surrounding variably resorbed olivine, pyroxenes, Cr-spinel, and in some cases, plagioclase. We interpret these micas as the result of open-system processes involving infiltration of water-rich evolved melts [with high Na/(Na + K)] and reaction with refractory minerals. The highest 100·Na/(Na + K) (~70) and Na2O concentrations (~5 wt%) in phlogopite appear to require reaction with liquids of unrealistically high Na/(Na + K) if no other factor is considered. This, together with the observation that phlogopites consist of alternating Na-rich and Na-poor cleavage-parallel bands, can be best interpreted by the presence of a solvus between the aspidolite (Na) and phlogopite (K) end-members. The high proportions (up to 15 vol%) of Na-rich phlogopite in two different groups of gabbroic xenoliths suggest that it might be a more common and abundant mineral than has been previously recognized, and that it may be used as an indicator of open-system processes. 2012-10-08T06:17:13Z 2019-12-06T19:15:48Z 2012-10-08T06:17:13Z 2019-12-06T19:15:48Z 2001 2001 Journal Article Costa, F., Dungan, M., & Singer, B. S. (2001). Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes: evidence for a solvus relation between phlogopite and aspidolite. American Mineralogist, 86(1-2), 29-35. 0003-004X https://hdl.handle.net/10356/95483 http://hdl.handle.net/10220/8721 http://ammin.geoscienceworld.org.ezlibproxy1.ntu.edu.sg/content/86/1-2.toc en American mineralogist © 2001 Mineralogical Society of America.
institution Nanyang Technological University
building NTU Library
country Singapore
collection DR-NTU
language English
topic DRNTU::Science::Geology
spellingShingle DRNTU::Science::Geology
Costa, Fidel
Dungan, Michael
Singer, Brad S.
Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite
description Magmatic Na-rich phlogopite (1–5 wt% Na2O) is present as a late-crystallizing mineral in two groups of texturally and mineralogically distinct gabbroic xenoliths at Volcán San Pedro (36°S, Chile), an Andean arc volcano. Phlogopites are characterized by high 100·Mg/(Mg + Fe) (up to 83) and high Cr2O3 contents (up to 0.4 wt%), and they are always found surrounding variably resorbed olivine, pyroxenes, Cr-spinel, and in some cases, plagioclase. We interpret these micas as the result of open-system processes involving infiltration of water-rich evolved melts [with high Na/(Na + K)] and reaction with refractory minerals. The highest 100·Na/(Na + K) (~70) and Na2O concentrations (~5 wt%) in phlogopite appear to require reaction with liquids of unrealistically high Na/(Na + K) if no other factor is considered. This, together with the observation that phlogopites consist of alternating Na-rich and Na-poor cleavage-parallel bands, can be best interpreted by the presence of a solvus between the aspidolite (Na) and phlogopite (K) end-members. The high proportions (up to 15 vol%) of Na-rich phlogopite in two different groups of gabbroic xenoliths suggest that it might be a more common and abundant mineral than has been previously recognized, and that it may be used as an indicator of open-system processes.
author2 School of Physical and Mathematical Sciences
author_facet School of Physical and Mathematical Sciences
Costa, Fidel
Dungan, Michael
Singer, Brad S.
format Article
author Costa, Fidel
Dungan, Michael
Singer, Brad S.
author_sort Costa, Fidel
title Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite
title_short Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite
title_full Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite
title_fullStr Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite
title_full_unstemmed Magmatic Na-rich phlogopite in a suite of gabbroic crustal xenoliths from Volcán San Pedro, Chilean Andes : evidence for a solvus relation between phlogopite and aspidolite
title_sort magmatic na-rich phlogopite in a suite of gabbroic crustal xenoliths from volcán san pedro, chilean andes : evidence for a solvus relation between phlogopite and aspidolite
publishDate 2012
url https://hdl.handle.net/10356/95483
http://hdl.handle.net/10220/8721
http://ammin.geoscienceworld.org.ezlibproxy1.ntu.edu.sg/content/86/1-2.toc
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