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Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa
Thesis (MSc)--Stellenbosch University, 2024.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613988224761856 |
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| access_status_str | Open Access |
| author | Christoffels, Casey Jade |
| author2 | Stevens, Gary |
| author_browse | Christoffels, Casey Jade Stevens, Gary |
| author_facet | Stevens, Gary Christoffels, Casey Jade |
| author_sort | Christoffels, Casey Jade |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2024.
|
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131618 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:44:52.743Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131618 Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa Christoffels, Casey Jade Stevens, Gary Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Magmas -- South Africa -- Peninsula Pluton -- Cape Granite Suite Intrusions (Geology) -- South Africa -- Millers Point Granite -- South Africa -- Camps Bay Magmas -- South Africa -- Cape Granite Suite -- Composition Pluton -- South Africa -- Western Cape UCTD Thesis (MSc)--Stellenbosch University, 2024. ENGLISH ABSTRACT: The size, frequency of arrival, composition, and temperature of magma batches that construct granite plutons are not well understood, although it is now well understood that all plutons intruded into the upper crust must be constructed incrementally. The S-type granites of the Peninsula pluton, South Africa, provide a unique opportunity to develop a deeper understanding of magma batches. The pluton is characterized by a coarse-grained porphyritic texture, dominated by K-feldspar phenocrysts. At Millers Point and Camps Bay, fine-grained leucocratic dykes and sills intruded the coarse-grained host while it was partially crystallized (20 to 5% melt) and carry significant information for understanding the emplacement of these plutons and evidence for the incremental assembly of granite magma chambers. Ti-in-zircon thermometry indicates that the host granite crystallized above 850 °C and the fine-grained granites intruded the coarse-grained host between 750 and 850 °C. Zr crystallization indicates that the magma was hotter than the crystal-mush at the time of injection, creating thermal reactivation of the pluton on a regional scale covering the entire Peninsula Pluton (10 000 km2) (Scheepers et al. 2006; Tankard et al. 1982). The earlier magma additions to the pluton homogenized through mixing and mingling to form the coarse-grained host granite and the late magma additions forming the fine-grained features were the last magmas to build the pluton. Crystal accumulation homogenizes magma compositions when the crystals settle, accumulate and re-melt (Scheepers et al. 2006). The major- and trace-element chemistry of these fine-grained rocks falls within the range defined by the coarse-grained pluton. Thus, these fine-grained granites might represent some of the magma batches that constructed the coarse-grained host granite. Phase equilibrium modelling constrains the pressure of crystallization for the host granite to approximately 0.75 kbar whereas the fine-grained rocks crystallized around 0.9 kbar. The volume of the magma batches forming the fine-grained features are very small as field evidence shows that the dykes are no greater than a few tens of meters, meaning these features formed from about 500 m3 of magma. This suggests that the pluton was assembled by multiple batches of small volumes of magma derived from a similar source by fluid absent melting at a temperature >800 °C. Furthermore, the magma batches ascended via dykes and intruded the pluton while it was in a crystal-mush state. The crystal-mush was much cooler than the intruding magma, which thereby cooled quickly after intrusion resulting in the fine-grained textures. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-01-29T10:42:49Z 2025-01-29T10:42:49Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131618 en Stellenbosch University 152 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Magmas -- South Africa -- Peninsula Pluton -- Cape Granite Suite Intrusions (Geology) -- South Africa -- Millers Point Granite -- South Africa -- Camps Bay Magmas -- South Africa -- Cape Granite Suite -- Composition Pluton -- South Africa -- Western Cape UCTD Christoffels, Casey Jade Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa |
| title | Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa |
| title_full | Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa |
| title_fullStr | Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa |
| title_full_unstemmed | Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa |
| title_short | Characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe Peninsula Pluton, Cape Granite Suite, South Africa |
| title_sort | characterisation of the compositions and conditions of intrusions of late magma batches that contributed tothe peninsula pluton cape granite suite south africa |
| topic | Magmas -- South Africa -- Peninsula Pluton -- Cape Granite Suite Intrusions (Geology) -- South Africa -- Millers Point Granite -- South Africa -- Camps Bay Magmas -- South Africa -- Cape Granite Suite -- Composition Pluton -- South Africa -- Western Cape UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131618 |
| work_keys_str_mv | AT christoffelscaseyjade characterisationofthecompositionsandconditionsofintrusionsoflatemagmabatchesthatcontributedtothepeninsulaplutoncapegranitesuitesouthafrica |