Thesis (MSc.)--Stellenbosch University, 1994. / ENGLISH ABSTRACT: The NAD deposit forms part of the A-Mine Complex in the Rooiberg tin field in
the north-western Transvaal. Mining started in 1986 and the mine was closed
recently following a decline of tin prices and metallurgical problems with ore
recovery.
The deposit is hosted by the Boschoffsberg Quartzite Member of the Pretoria
Group sediments and is structurally controlled within the so-called Tin Zone.
Extensive alteration of the original host rocks occurred during the
mineralisation event. Potassic remobilisation and redistribution appear to
have taken place pervasively. The nature of the original host rock was
altered to such an extent that it cannot be classified correctly. Previous
workers refer to the host rock as an arkose because of its feldspathic nature.
Wall rock alteration in the hanging- and foot wall of the different ore lodes
(fractures) is generally similar. Very little change is observed in whole rock
chemistry away from the lodes.
The mineral chemistry of the ore lode minerals is indicative of fluid
composition and mineralising conditions in the NAD deposit. The FeO/(FeO +
MgO) ratio of tourmalines indicates deposition at a distance from the source
of the mineralising fluids. Pyrite trace element chemistry differs from that of
the Leeuwpoort deposit, indicating changing fluid chemistry. Contrary to
previous assumptions that the carbonate present is ankerite, abundant
siderite occurrences were found. Pyrite may co-precipitate with siderite under
specific physico-chemical conditions. Cassiterite is generally trace element
poor and relatively enriched in Fe.
Hydraulic brecciation of the fractures as well as the tourmaline chemistry are
strong indicators of a hydrothermal origin for the NAD deposit. However, the
origin of the hydrothermal fluids is still uncertain. / AFRIKAANSE OPSOMMING: Die NAD- tinafsetting vorm dee/ van die A-Myn-kompleks in die Rooiberg
tinveld in die noord-wes Transvaal. Die myn is in 1986 geopen en is onlangs
gesluit weens swak tinpryse en metallurgiese ertsherwinningsprobleme.
Die tinafsetting kom voor in die Boschoffsberg Kwartsiet lid van die Pretoria
Groep sedimente. Dit is strukturee/ gekontroleer binne die sogenaamde Tin
Sone.
Vorige navorsers het na die waardgesteente as 'n arkose verwys op grand
van die hoe veldspaat-inhoud. lntensiewe en uitgebreide verandering van die
oorspronklike waardgesteentes het plaasgevind tydens mineralisasie.
Deurdringende kalium-hermobilisering en -herverspreiding het plaasgevind.
Die aard van die oorspronklike waardgesteente is egter tot so 'n mate
verander, dat dit chemies nie korrek gek/assifiseer kan word nie.
Wandrotsverandering van die verskil/ende ertsskeute in beide die voet- en
dakgesteentes is baie soortge/yk. Die heelrotsgeochemie van die
wandgesteentes verskil baie min weg van die ertsskeute af.
Die mineraalchemie van die ertsskeut-minerale is aanduidend van die
v/oeistofsamestelling en mineralisasietoestande van die NAD-tinafsetting. Die
FeO/(FeO + MgO) verhouding van toermalyne dui daarop dat afsetting op 'n
afstand vanaf die bron van die mineralisasie-vloeistowwe plaasgevind het.
Die spoor-elementchemie van die NAD-piriete verskil van die piriete van die
Leeuwpoort tinafsetting, wat verandering in vloeistofsamestelling aandui. In
teenstelling met vorige aannames dat die karbonate in die Rooiberg
tinafsettings as ankeriet bekend staan, is daar volop sideriet gevind. Piriet
kristalliseer dikwels saam met sideriet onder spesifieke fisiese en chemiese
toestande. Kassiteriet is meestal arm aan spoor-elemente, maar is relatief
verryk in Fe.
Hidroliese breksiering van die skeute en die toermalyn-chemie dui sterk op 'n
hidrotermale oorsprong vir die NAD afsetting. Die bron van die vloeistowwe is
nog nie definitief vasgestel nie. / Digitized at 300 dpi Colour PDF format (OCR), using ,KODAK i 1220 PLUS scanner. Digitised, Ricardo Davids on request from IBL 10 September 2013
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/58243 |
| Date | 12 1900 |
| Creators | Naude, Karin |
| Contributors | Hallbauer, D. K., Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 228 p. : ill. |
| Rights | Stellenbosch University |
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