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Complex zoning in clinopyroxenes from Marion Island
Dissertation (MSc)--University of Pretoria, 2013.
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| Format: | Thesis |
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University of Pretoria
2013
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| _version_ | 1867613688250236928 |
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| access_status_str | Open Access |
| author2 | Roberts, R.J. (James) |
| author_browse | Roberts, R.J. (James) |
| author_facet | Roberts, R.J. (James) |
| collection | Thesis |
| dc_rights_str_mv | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria |
| description | Dissertation (MSc)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/24752 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:40:07.413Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/24752 Complex zoning in clinopyroxenes from Marion Island Roberts, R.J. (James) upetd@up.ac.za Botha, Andries Eliza Johannes Clinopyroxenes Complex zoning Marion Island UCTD Dissertation (MSc)--University of Pretoria, 2013. Euhedral clinopyroxene mega-crystals have been retrieved from Marion Island, a volcanic island situated on an inactive transform fault near the mid oceanic ridge on Antarctic tectonic plate and part of the Prince Edward Island group. The island is considered to be the product of hotspot- related volcanism. Clinopyroxene megacrysts were sampled from the southern side of the island on a scoria cone named Pyroxene Hill. Several analytical methods including Energy Dispersive Spectrometry (EDS), Electron Probe Microanalysis (EPMA) and EPMA-mapping were utilized in investigating the zoning found within these 5-10 cm large crystals. The zoning found was “patchy”, in that it did not conform to commonly described zoning such as normal, reverse, sector or oscillatory, but rather consisted of chemically distinct areas with either diffuse or sharp boundaries, not orientated parallel to the grain boundaries or crystal lattice. The chemistry of the crystals indicates that they have formed from an evolved basaltic melt, and are likely to have crystallised at a depth of 15- 30 km. A model is postulated for the formation of these crystals in which the megacrysts crystallise rapidly from a supersaturated melt. Pre-existing crystalline material undergoes imperfect diffusion at high temperature to create a patchwork of compositional zones. Supersaturation likely requires a volatile-rich melt, which undergoes rapid degassing owing to an external trigger. The presence of a transform fault directly below Marion Island may provide a seismic trigger for such a degassing event. Geology unrestricted 2013-09-06T18:16:34Z 2013-05-24 2013-09-06T18:16:34Z 2013-04-17 2013-05-24 2013-05-16 Dissertation Botha, AEJ 2013, Complex zoning in clinopyroxenes from Marion Island, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/24752 > E13/4/498/gm http://hdl.handle.net/2263/24752 http://upetd.up.ac.za/thesis/available/etd-05162013-170024/ © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria application/pdf University of Pretoria |
| spellingShingle | Clinopyroxenes Complex zoning Marion Island UCTD Complex zoning in clinopyroxenes from Marion Island |
| title | Complex zoning in clinopyroxenes from Marion Island |
| title_full | Complex zoning in clinopyroxenes from Marion Island |
| title_fullStr | Complex zoning in clinopyroxenes from Marion Island |
| title_full_unstemmed | Complex zoning in clinopyroxenes from Marion Island |
| title_short | Complex zoning in clinopyroxenes from Marion Island |
| title_sort | complex zoning in clinopyroxenes from marion island |
| topic | Clinopyroxenes Complex zoning Marion Island UCTD |
| url | http://hdl.handle.net/2263/24752 http://upetd.up.ac.za/thesis/available/etd-05162013-170024/ |