Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica
Includes bibliographical references. Includes illustrations and maps. Basaltic rocks of the Hut Point Peninsula, Ross Island, Antarctica, are a part of a linear trend of volcanic occurrences which parallel the Transantarctic Mountains for 2000 km. Structural relations suggest the tensional nature o...
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Northern Illinois University
1974
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ftnorthillinuni:oai:commons.lib.niu.edu:10843/24857 2023-05-15T13:37:34+02:00 Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica Hunter, William Clay Stuckless, John S. Department of Geology 1974 v, 91 pages application/pdf https://commons.lib.niu.edu/handle/10843/24857 eng eng Northern Illinois University https://commons.lib.niu.edu/handle/10843/24857 NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors. Basalt Petrology--Antarctica Text Dissertation/Thesis 1974 ftnorthillinuni 2022-01-29T23:33:03Z Includes bibliographical references. Includes illustrations and maps. Basaltic rocks of the Hut Point Peninsula, Ross Island, Antarctica, are a part of a linear trend of volcanic occurrences which parallel the Transantarctic Mountains for 2000 km. Structural relations suggest the tensional nature of the region, a feature also indicated by the abundance of volcanic occurrences. The basanitoid (silica-undersaturated, alkali-rich olivine basalt lacking phenocrystal nepheline but with greater than 5% normative nepheline) of this study is of interest because it carries an abundant suite of ultramafic inclusions and therefore provides a look at upper mantle mechanisms of generation and transport of basaltic magmas. The Twin Crater-Helo Pad flow extends for 1350 m with an average width of 175 m. The flow is massive to scoriaceous, moderately to extremely vesicular, and has a minimum thickness of 3.6 m. The intergranular matrix holds porphyritic mega- crysts of olivine, titanaugite, and kaersutite. Xenolithic material is abundant and includes dunitic or peridotitic nodules, gabbroic or granulitic crustal fragments, and metasedimentary basement inclusions. The flow exhibits broad variation within narrow limits, but most variation has been obscured by turbulence produced by the rapid and violent eruption of this basanitoid. Two other basanitoid occurrences of the immediate area may be included in a petrogenetic model for the Twin Crater flow, but neither can be correlated with the flow. Chemical analyses indicate that the magma originated by low degrees of partial melting of primitive peridotitic (previously undepleted) mantle material at substantial depth. Rare earth element anomalies suggest that garnet was a residual phase, thus placing the melting zone at a depth greater than 100 km. Ultramafic inclusions further support an origin at this depth. Primary crystallization occurred at depths of 45 to 75 km probably under conditions of low water content and low initial oxygen fugacity and involved olivine, titan- augite, and titanomagnetite as major phases. Secondary crystallization at shallow levels was insignificant. The suite of ultramafic xenoliths and xenocrysts of kaersutite and two clinopyroxenes complicated definition of the cognate solidus assemblage for comparison to experimental results but had no apparent effect on the chemistry of the melt. The magma ascended rapidly from depth, as indicated by abundant mantle-origin xenoliths and a lack of primary plagioclase crystallization. Eruption and cooling were violent and tapid. Weathering processes have not affected the flow to any great degree, and alteration is restricted to xenolithic material reacting to magmatic or near-surface conditions. Secondary mineralization or hydrothermal alteration have had no significant effect on the Twin Crater-Helo Pad flow. M.S. (Master of Science) Thesis Antarc* Antarctica Ross Island Northern Illinois University (NIU): Huskie Commons Repository Hut Point ENVELOPE(166.850,166.850,-77.767,-77.767) Hut Point Peninsula ENVELOPE(166.850,166.850,-77.767,-77.767) Ross Island Titan ENVELOPE(-68.733,-68.733,-72.083,-72.083) Transantarctic Mountains Twin Crater ENVELOPE(166.683,166.683,-77.833,-77.833) |
institution |
Open Polar |
collection |
Northern Illinois University (NIU): Huskie Commons Repository |
op_collection_id |
ftnorthillinuni |
language |
English |
topic |
Basalt Petrology--Antarctica |
spellingShingle |
Basalt Petrology--Antarctica Hunter, William Clay Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica |
topic_facet |
Basalt Petrology--Antarctica |
description |
Includes bibliographical references. Includes illustrations and maps. Basaltic rocks of the Hut Point Peninsula, Ross Island, Antarctica, are a part of a linear trend of volcanic occurrences which parallel the Transantarctic Mountains for 2000 km. Structural relations suggest the tensional nature of the region, a feature also indicated by the abundance of volcanic occurrences. The basanitoid (silica-undersaturated, alkali-rich olivine basalt lacking phenocrystal nepheline but with greater than 5% normative nepheline) of this study is of interest because it carries an abundant suite of ultramafic inclusions and therefore provides a look at upper mantle mechanisms of generation and transport of basaltic magmas. The Twin Crater-Helo Pad flow extends for 1350 m with an average width of 175 m. The flow is massive to scoriaceous, moderately to extremely vesicular, and has a minimum thickness of 3.6 m. The intergranular matrix holds porphyritic mega- crysts of olivine, titanaugite, and kaersutite. Xenolithic material is abundant and includes dunitic or peridotitic nodules, gabbroic or granulitic crustal fragments, and metasedimentary basement inclusions. The flow exhibits broad variation within narrow limits, but most variation has been obscured by turbulence produced by the rapid and violent eruption of this basanitoid. Two other basanitoid occurrences of the immediate area may be included in a petrogenetic model for the Twin Crater flow, but neither can be correlated with the flow. Chemical analyses indicate that the magma originated by low degrees of partial melting of primitive peridotitic (previously undepleted) mantle material at substantial depth. Rare earth element anomalies suggest that garnet was a residual phase, thus placing the melting zone at a depth greater than 100 km. Ultramafic inclusions further support an origin at this depth. Primary crystallization occurred at depths of 45 to 75 km probably under conditions of low water content and low initial oxygen fugacity and involved olivine, titan- augite, and titanomagnetite as major phases. Secondary crystallization at shallow levels was insignificant. The suite of ultramafic xenoliths and xenocrysts of kaersutite and two clinopyroxenes complicated definition of the cognate solidus assemblage for comparison to experimental results but had no apparent effect on the chemistry of the melt. The magma ascended rapidly from depth, as indicated by abundant mantle-origin xenoliths and a lack of primary plagioclase crystallization. Eruption and cooling were violent and tapid. Weathering processes have not affected the flow to any great degree, and alteration is restricted to xenolithic material reacting to magmatic or near-surface conditions. Secondary mineralization or hydrothermal alteration have had no significant effect on the Twin Crater-Helo Pad flow. M.S. (Master of Science) |
author2 |
Stuckless, John S. Department of Geology |
format |
Thesis |
author |
Hunter, William Clay |
author_facet |
Hunter, William Clay |
author_sort |
Hunter, William Clay |
title |
Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica |
title_short |
Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica |
title_full |
Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica |
title_fullStr |
Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica |
title_full_unstemmed |
Petrography and petrology of a basanitoid flow from Hut Point Peninsula, Antarctica |
title_sort |
petrography and petrology of a basanitoid flow from hut point peninsula, antarctica |
publisher |
Northern Illinois University |
publishDate |
1974 |
url |
https://commons.lib.niu.edu/handle/10843/24857 |
long_lat |
ENVELOPE(166.850,166.850,-77.767,-77.767) ENVELOPE(166.850,166.850,-77.767,-77.767) ENVELOPE(-68.733,-68.733,-72.083,-72.083) ENVELOPE(166.683,166.683,-77.833,-77.833) |
geographic |
Hut Point Hut Point Peninsula Ross Island Titan Transantarctic Mountains Twin Crater |
geographic_facet |
Hut Point Hut Point Peninsula Ross Island Titan Transantarctic Mountains Twin Crater |
genre |
Antarc* Antarctica Ross Island |
genre_facet |
Antarc* Antarctica Ross Island |
op_relation |
https://commons.lib.niu.edu/handle/10843/24857 |
op_rights |
NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors. |
_version_ |
1766094308785520640 |