Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T.
The layered series of the Muskox Intrusion can be divided into four megacyclic units on the basis of field mapping, each beginning with a thick olivine cumulate and succeeded up section by a variety of pyroxenitic and gabbroic cumulates. A systematic change in the order of appearance of orthopyroxen...
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McGill University
1992
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ftcanadathes:oai:collectionscanada.gc.ca:QMM.22495 2023-05-15T17:13:40+02:00 Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T. DesRoches, Valérie Master of Science (Department of Geological Sciences.) 1992 application/pdf http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22495 en eng McGill University alephsysno: 001291063 proquestno: MM74498 Theses scanned by UMI/ProQuest. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22495 All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. Geology Electronic Thesis or Dissertation 1992 ftcanadathes 2014-02-16T00:56:53Z The layered series of the Muskox Intrusion can be divided into four megacyclic units on the basis of field mapping, each beginning with a thick olivine cumulate and succeeded up section by a variety of pyroxenitic and gabbroic cumulates. A systematic change in the order of appearance of orthopyroxene in the pyroxenite units of the layered series is correlated with a decrease in Mg no. (Mg/Mg + $ Sigma$Fe in cation units) at which clinopyroxene joins olivine on the liquidus, and spike-like increases in LIL/HFS ratios, which require that the composition of the magma of the Muskox Intrusion changed through time across the layered series. Mixing of residual liquid with primary liquids replenishing the chamber can explain the upsection decrease in the Mg no. of clinopyroxene at the base of successive pyroxenite units, but this mechanism cannot account for increased ratios of LIL to HFS incompatible elements observed in the olwebsterite of Megacycle #3 and the first websterite of Megacycle #4, because these ratios are not significantly fractionated by closed-system crystal fractionation. Contamination of the parental magma with melts from the paragneiss country rocks can reproduce the observed increase in the ratios of K/Ti and K/Zr. The gabbroic layers of Megacycle #1, #2, and #3 are especially enriched in LIL/HFS ratios, indicating the presence of a highly contaminated magma layer above the uncontaminated magma which crystallized much of the ultramafic series. The spike-like enrichment in LIL/HFS ratios in the pyroxenites suggests that episodic events of mixing occurred between an evolving uncontaminated magma and a highly contaminated magma, accumulated at the roof of the magma chamber. Thesis muskox Theses Canada/Thèses Canada (Library and Archives Canada) The Spike ENVELOPE(-37.317,-37.317,-54.017,-54.017) |
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Theses Canada/Thèses Canada (Library and Archives Canada) |
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ftcanadathes |
language |
English |
topic |
Geology |
spellingShingle |
Geology DesRoches, Valérie Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T. |
topic_facet |
Geology |
description |
The layered series of the Muskox Intrusion can be divided into four megacyclic units on the basis of field mapping, each beginning with a thick olivine cumulate and succeeded up section by a variety of pyroxenitic and gabbroic cumulates. A systematic change in the order of appearance of orthopyroxene in the pyroxenite units of the layered series is correlated with a decrease in Mg no. (Mg/Mg + $ Sigma$Fe in cation units) at which clinopyroxene joins olivine on the liquidus, and spike-like increases in LIL/HFS ratios, which require that the composition of the magma of the Muskox Intrusion changed through time across the layered series. Mixing of residual liquid with primary liquids replenishing the chamber can explain the upsection decrease in the Mg no. of clinopyroxene at the base of successive pyroxenite units, but this mechanism cannot account for increased ratios of LIL to HFS incompatible elements observed in the olwebsterite of Megacycle #3 and the first websterite of Megacycle #4, because these ratios are not significantly fractionated by closed-system crystal fractionation. Contamination of the parental magma with melts from the paragneiss country rocks can reproduce the observed increase in the ratios of K/Ti and K/Zr. The gabbroic layers of Megacycle #1, #2, and #3 are especially enriched in LIL/HFS ratios, indicating the presence of a highly contaminated magma layer above the uncontaminated magma which crystallized much of the ultramafic series. The spike-like enrichment in LIL/HFS ratios in the pyroxenites suggests that episodic events of mixing occurred between an evolving uncontaminated magma and a highly contaminated magma, accumulated at the roof of the magma chamber. |
format |
Thesis |
author |
DesRoches, Valérie |
author_facet |
DesRoches, Valérie |
author_sort |
DesRoches, Valérie |
title |
Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T. |
title_short |
Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T. |
title_full |
Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T. |
title_fullStr |
Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T. |
title_full_unstemmed |
Petrogenesis of the pyroxenite units in the Muskox intrusion, N.W.T. |
title_sort |
petrogenesis of the pyroxenite units in the muskox intrusion, n.w.t. |
publisher |
McGill University |
publishDate |
1992 |
url |
http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22495 |
op_coverage |
Master of Science (Department of Geological Sciences.) |
long_lat |
ENVELOPE(-37.317,-37.317,-54.017,-54.017) |
geographic |
The Spike |
geographic_facet |
The Spike |
genre |
muskox |
genre_facet |
muskox |
op_relation |
alephsysno: 001291063 proquestno: MM74498 Theses scanned by UMI/ProQuest. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22495 |
op_rights |
All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
_version_ |
1766070855462289408 |