Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume
Thesis (MSc)--Stellenbosch University, 2012.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | en_ZA |
| Published: |
Stellenbosch : Stellenbosch University
2012
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613943941300224 |
|---|---|
| access_status_str | Open Access |
| author | Mukosi, Ndivhuwo Cecilia |
| author2 | Miller, Jodie A. |
| author_browse | Miller, Jodie A. Mukosi, Ndivhuwo Cecilia |
| author_facet | Miller, Jodie A. Mukosi, Ndivhuwo Cecilia |
| author_sort | Mukosi, Ndivhuwo Cecilia |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2012. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/71665 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:44:10.803Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/71665 Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume Mukosi, Ndivhuwo Cecilia Miller, Jodie A. Macey, Paul Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Geology -- Madagascar Petrogenesis -- Madagascar Ambohiby Complex (Madagascar) Volcanic plumes -- Madagascar Dissertations -- Earth sciences Theses -- Earth sciences Thesis (MSc)--Stellenbosch University, 2012. ENGLISH ABSTRACT: The Cretaceous Ambohiby Complex is an alkaline ring complex located in the central part of Madagascar and covers a mountainous area of approximately 225km2. The complex intrudes into Precambrian basement gneisses and consists of the following rock types in a chronological order; gabbros, monzonite, alkali-syenite, micro-granite and granites. Both mafic and felsic rocks are dominated by sodic mineralogies. Pyroxenes are generally aegirine, aegirine-augite, and hedenbergite and commonly occur in granites, micro-granites, syenites and monzonite. In gabbros and mafic dykes, augite is the more common composition. Amphiboles are represented by bluish to brownish-green varieties with arfvedsonite to eckermannite compositions in granites, and magnesia-arfvedsonite compositions in micro-granites. Ferro-edenite is present in some alkali-syenites and monzonite. Feldspars are usually single phase and are therefore hypersolvus. In granites, micro-granites and alkali-syenites, path and string perthite is very common. Graphic intergrowth of quartz and alkali feldspars is also common in granites and some alkalisyenites. Major elements variation diagrams plotted against SiO2 indicate that the mafic and felsic rocks of the Ambohiby Complex were formed by processes similar to those of Fractional crystallization. Chondrite normalised mafic rocks have slightly positive Eu anomalies while the felsic rocks have negative Eu anomalies, indicating fractionation of plagioclase feldspars. The Chondrite normalised gabbroic rocks shared similar trends of heavy rare earth with Chondrite normalised Marion Hotspot data. This suggests that the basaltic parent magma for the Ambohiby Complex, possibly related to the Marion hotspot plume. The Fractional crystallization model with an inclusion of olivine in the mineral assemblage seems to fit very well with the actual Ambohiby felsic end member rocks (i.e. granites). It is therefore clear that differentiation mainly occurred by fractional crystallization but variable initial Sr and Nd values indicate the magmas assimilated crustal material during emplacement. The Rb-Sr geochronology gave an age of 90±2.4 Ma for the intrusion of the Ambohiby Complex, which confirms that the Ambohiby Complex is associated with the Gondwana break-up. In addition the Marion Hotspot plume is believed to have been located in the southern tip of the island at around 90 Ma ago. 2012-10-16T12:23:39Z 2012-12-12T08:08:36Z 2012-10-16T12:23:39Z 2012-12-12T08:08:36Z 2012-12 Thesis http://hdl.handle.net/10019.1/71665 en_ZA Stellenbosch University 126 p. : ill., maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Geology -- Madagascar Petrogenesis -- Madagascar Ambohiby Complex (Madagascar) Volcanic plumes -- Madagascar Dissertations -- Earth sciences Theses -- Earth sciences Mukosi, Ndivhuwo Cecilia Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume |
| title | Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume |
| title_full | Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume |
| title_fullStr | Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume |
| title_full_unstemmed | Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume |
| title_short | Petrogenesis of the Ambohiby Complex, Madagascar and the role of the Marion Hotspot Plume |
| title_sort | petrogenesis of the ambohiby complex madagascar and the role of the marion hotspot plume |
| topic | Geology -- Madagascar Petrogenesis -- Madagascar Ambohiby Complex (Madagascar) Volcanic plumes -- Madagascar Dissertations -- Earth sciences Theses -- Earth sciences |
| url | http://hdl.handle.net/10019.1/71665 |
| work_keys_str_mv | AT mukosindivhuwocecilia petrogenesisoftheambohibycomplexmadagascarandtheroleofthemarionhotspotplume |