Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
The Geelwal Karoo heavy mineral deposit: a modern day beach placer
Thesis (MSc)--Stellenbosch University, 1996.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | en_ZA |
| Published: |
Stellenbosch : Stellenbosch University
2011
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867614112395034624 |
|---|---|
| access_status_str | Open Access |
| author | MacDonald, William Graham |
| author2 | Rozendaal, Abraham
|
| author_browse | MacDonald, William Graham Rozendaal, Abraham |
| author_facet | Rozendaal, Abraham
MacDonald, William Graham |
| author_sort | MacDonald, William Graham |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 1996. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/11122 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:51.765Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2011 |
| publishDateRange | 2011 |
| publishDateSort | 2011 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/11122 The Geelwal Karoo heavy mineral deposit: a modern day beach placer MacDonald, William Graham Rozendaal, Abraham Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Geology, Stratigraphic -- Paleozoic Geology, Stratigraphic -- Precambrian Metamorphic rocks -- South Africa -- Namaqualand Heavy minerals -- Geelwal Karoo Ore deposits -- South Africa -- Namaqualand Placer deposits -- South Africa -- Namaqualand UCTD Thesis (MSc)--Stellenbosch University, 1996. ENGLISH ABSTRACT: The Geelwal Karoo heavy mineral placer is situated in an active beach environment along the rugged southern Namaqualand coast of South Africa. The geomorphology of the coast is controlled by resistant Precambrian and Palaeozoic basement rocks which also dictate the narrow, elongate geometry and limited 10 km strike length of this strandline deposit. Ore reserves are small compared to the multi-million tonne analogous Quaternary sands elsewhere in the world. However, the locally high total heavy mineral content and favourable ore to gangue mineral ratio, coupled with the possibility of replenishment style mining, make this a potential resource. Garnet and ilmenite are the dominant heavy minerals, followed by pyroxene, zircon, rutile and titaniferous alteration products after ilmenite. These mineral proportions are reflected in palaeostrandline, and aeolian deposits occurring on Geelwal Karoo and at Graauwduinen, although the total heavy mineral content may vary as a result of local environmental influences. The ilmenite grains contain on average between 48 and 51 % TiO₂. Alteration products of ilmenite do not contribute significantly to the total heavy mineral content of the Geelwal Karoo beach sands. This factor, along with the low rutile and zircon content of the sands, adversely affects the economic value of the Geelwal Karoo beach deposit. The titanium content of ilmenite (48 - 51 % TiO₂) and predominantly almandine garnet suggest metamorphic source rocks, most likely part of the Namaqualand Metamorphic Complex. These rocks are considered to be the primary source of the heavy minerals occuring on Geelwal Karoo. Radiometric analysis of samples indicates a common source for the heavy minerals found in the Geelwal Karoo beach sands as well as the palaeoplacers occurring on Geelwal Karoo and Graauwduinen. The light minerals on the present-day Geelwal Karoo beach, however, display different radiometric signatures to the palaeoplacers as a result of sediment supply from modern rivers. Large quantities of heavy minerals are concentrated in the 35 m palaeostrandline occurring on Geelwal Karoo. This palaeostrandline acts as a point source, which supplies vast quantities of heavy minerals to the present coastal environment. The prominent headland to the south results in the formation of a J-bay environment on Geelwal Karoo. Sediment supplied to the beach is sorted, and the heavy minerals concentrated on the backshore, by cross-shore sediment sorting. The light minerals are transported northward by the dominant northward longshore drift. This combination of cross-shore sorting followed by longshore transport of the light minerals has resulted in the formation of an exceptionally high grade placer on the present day beach at Geelwal Karoo. AFRIKAANSE OPSOMMING: Die Geelwal Karoo swaar mineraalafsetting is in 'n aktiewe strandgebied aan die onherbergsame suidelike Namakwalandse kus van Suid-Afrika gelee. Die geomorfologie van die kus word beheer deur weerstandbiedende Precambriese en Paleozoiese vloergesteentes. Laasgenoemde bepaal ook die smal, lang, en beperkte (10 km) strekking van hierdie strandt afsetting. Die ertsreserwe is relatief klein, vergeleke met soortgelyke Kwaternere swaar mineraalafsettings elders ter wereld. Daarteenoor moet egter genoem word dat die plaaslike hoe swaarmineraalinhoud, gunstige erts/afval verhouding, en moontlike aanvullings mynboutegniek, hierdie 'n aantreklike minerale hulpbron maak. Granaat en ilmeniet is die oorheersende swaarminerale, gevolg deur piroksene, sirkoon, rutiel en titaandraende verweringsprodukte van ilmeniet. Hierdie mineraal verhoudings word in paleostrandlyne en aeoliese afsettings by beide Geelwal Karoo en Graauwduinen gevind, hoewel die totale swaar mineraalinhoud as gevolg van plaaslike omstandighede kan wissel. Die titaan inhoud van die ilmeniet is gemiddeld tussen 48 en 51 % TiO₂. Verweringsprodukte van ilmeniet dra nie betekenisvol by tot die totale swaarmineraalinhoud van die Geelwal Karoo afsetting nie. Tesame met die lae rutiel-, en sirkooninhoud, het hierdie faktore 'n negatiewe invloed op die ekonomiese potensiaal van die Geelwal Karoo strandafsetting. Die titaaninhoud van ilmeniet (48-51%) en hoofsaaklik almandien endlid van die granaat populasie, dui 'n metamorfe terrein as moontlike provenans gebied, heelwaarskynlik die Namakwalandse Metamorfe Kompleks Radiometriese monsterontleding dui op 'n gemeenskaplike bron vir sowel die swaarminerale in Geelwal Karoo strandsand as die paleoafsettings wat op Geelwal Karoo en Graauwduinen voorkom. Die ligte minerale fraksie van die hedendaagse Geelwal Karoo strand toon 'n radiometriese karakter wat verskil van paleoafsettings op Geelwal karoo en Graauwduinen. Dit dui op die invloed van sediment toevoer tot die Geelwal Karoo strand vanaf huidige riviere. Groot hoeveelhede swaar minerale Is gekonsentreer In die 35m strandlyn op Geelwal Karoo. Die paleostrandlyn dien as puntbron, en voorsien swaarminerale aan die huidige kusstrook. Die groot landpunt suid van Geelwal Karoo vorm 'n J vormige baai wat 'n belangrike invloed op die vorming van die afsetting het. Sediment wat by die strand aankom word gesorteer en swaar minerale word deur middel van dwarsstrome agter op die strand gekonsentreer, terwyl ligter minerale noordwaards gevoer word deur die heersende seestroom. Die gekombineerde invloede van dwars-strand sortering, en langstrandse noordwaartse vervoer van ligter minerale, lui tot 'n besondere hoe konsentrasie swaarminerale op die huidige strand by Geelwal Karoo. Masters 2011-05-15T15:59:20Z 2011-05-15T15:59:20Z 1996-12 Thesis http://hdl.handle.net/10019.1/11122 en_ZA Stellenbosch University 319 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Geology, Stratigraphic -- Paleozoic Geology, Stratigraphic -- Precambrian Metamorphic rocks -- South Africa -- Namaqualand Heavy minerals -- Geelwal Karoo Ore deposits -- South Africa -- Namaqualand Placer deposits -- South Africa -- Namaqualand UCTD MacDonald, William Graham The Geelwal Karoo heavy mineral deposit: a modern day beach placer |
| title | The Geelwal Karoo heavy mineral deposit: a modern day beach placer |
| title_full | The Geelwal Karoo heavy mineral deposit: a modern day beach placer |
| title_fullStr | The Geelwal Karoo heavy mineral deposit: a modern day beach placer |
| title_full_unstemmed | The Geelwal Karoo heavy mineral deposit: a modern day beach placer |
| title_short | The Geelwal Karoo heavy mineral deposit: a modern day beach placer |
| title_sort | geelwal karoo heavy mineral deposit a modern day beach placer |
| topic | Geology, Stratigraphic -- Paleozoic Geology, Stratigraphic -- Precambrian Metamorphic rocks -- South Africa -- Namaqualand Heavy minerals -- Geelwal Karoo Ore deposits -- South Africa -- Namaqualand Placer deposits -- South Africa -- Namaqualand UCTD |
| url | http://hdl.handle.net/10019.1/11122 |
| work_keys_str_mv | AT macdonaldwilliamgraham thegeelwalkarooheavymineraldepositamoderndaybeachplacer AT macdonaldwilliamgraham geelwalkarooheavymineraldepositamoderndaybeachplacer |