Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: This study was initialized to introduce capillary electrophoresis (CE) as a useful technique in
the analysis of fluid inclusions in quartz. lts advantages are low detection limits for the
dissolved ionic content of the fluid, the small amount of sample (1 g or less) for a detailed
qualitative and quantitative analysis, and the short time required to obtain results (one run for
either cations or anions take approximately 10 minutes).
The study area from which quartz veins were selected is situated within the Neoproterozoic
Saldania belt. Syn- and post-tectonic S-, 1- and A-type granitoids from the Cape Granite Suite
intruded the metamorphosed Malmesbury greywacke and pelites between 550 and 510 Ma.
Additional periods of tectonism and metamorphism occurred during Cape Supergroup
sedimentation (480 - 400 Ma) as well as Karoo sedimentation and the simultaneous Cape
Orogeny (280 -215 Ma).
The quartz-biotite±chlorite vems are hosted by Cape Granite as well as Malmesbury
sediments. These barren quartz veins are part of two vein sets, one dipping at an angle
between 15 and 500 to the S to SE and striking W, similar to Sn-mineralized quartz veins in
the SW-cape, while the other is near-vertical and striking W to NW. Except for their
orientation, no differences regarding associated minerals, inclusion characteristics or fluid
chemistry indicated a difference in origin.
Four fluid phases within a temperature range of 160 - 390 °C were identified as being largely
late-magmatic and released from the underlying Cape Granite plutons, namely an early 370-
390 °C population, followed by the 310 - 360, 230 - 300 and lastly the 160 - 200 °C
populations. Initiation of this fluid system occurred from at least SlOMa, after final granite
intrusion, but the age of the final stage is unknown. Renewed fluid circulation occurred during a later period of metamorphism, possibly during the Cape Orogeny. These fluids had
temperatures between 240 and 360°C and are of sedimentary origin, most likely released
from the Malmesbury metamorphites.
The technique of capillary electrophoresis has been evaluated for its application to bulk fluid
inclusion analysis, and the crush-leach fluid extraction procedure of Bottrell, et al., (1988)
optimized for CE analysis. Contamination factors were identified and minimized or
eliminated, where possible. Bulk fluid inclusion chemistry obtained by CE was therefore
proved to provide valuable information regarding the various fluid generations as long as
inclusion populations are investigated individually to explain and correlate bulk data. / AFRIKAANSE OPSOMMING: Die doel van die studie was om te toon dat die tegniek van kapillêre elektroforese bruikbaar is
in die analiese van vloeistofmsluitsels in kwarts. Die voordele van hierdie tegniek is lae
deteksie limiete vir die opgeloste ioon inhoud van die vloeistof, die klein monstergrootte
(< 1g) wat nodig is vir 'n omvattende kwalitatiewe en kwantitatiewe analise, en die kort
tydsduur waarin resultate verkry word ('n katioon of anioon analise vir een monster duur lO
minute).
Die studie gebied waar kwarts are gemonster is, is binne die Neoproterosoïese Saldania
Gordel geleë. Sin- en laat-tektoniese S-, I- en A-tipe graniete van die Kaapse Graniet Suite het
die gemetamorfiseerde Malmesbury grouwakke en peliete tussen 550 en 510 Ma
binnegedring. Latere periodes van tektonisme en metamorfose het tydens deponering van die
Kaap Supergroep (480 - 400 Ma), en die gelyktydige episodes van Karoo sedimentasie en
Kaapse Orogenese (280 - 215 Ma) plaasgevind.
Die gasheer gesteentes vir die kwarts-biotiet±chloriet are is Kaapse Graniet sowel as
Malmesbury sedimente. Hierdie ongemineraliseerde are is deel van twee aarstelsels, nl. een
met 'n duik hoek tussen 15 en 50° S tot SO en 'n westelike strekking, soortgelyk aan die Sn-
,.gemineraliseerde are in die SW-Kaap, terwyl die ander stel are feitlik vertikaal is en W tot
NW strek. Behalwe vir die verskil in oriëntasie was daar geen aanduiding, wat betref 'n
verskil in geassosieerde minerale, vloeistofinsluitsel kenmerke of vloeistof chemie, dat hierdie
twee aarstelsels van verskillende oorsprong is nie.
Vier vloeistof fases binne 'n temperatuur gebied van 160 - 390 °C en 'n vloeistof saliniteit
van 0 - 5.7 gewig % NaC1 ekw. is geïdentifiseer, met 'n laat-magmatiese assosiasie en
vrygestel deur die onderliggende Kaapse Graniete. Dit behels 'n vroeë 370 - 390 °C populasie, gevolg deur die 310 - 360, 230 - 300 en laastens die 160 - 200 °C populasies.
Inisiasie van hierdie sisteem kon moontlik rondom 510 Ma gelede plaasgevind het, maar die
ouderdom van die finale fase is onbekend. Hernude vloeistof sirkulasie het tydens 'n later
stadium van metamorfose onstaan, moontlik tydens die Kaapse Orogenese. Hierdie
vloeistowwe het temperature tussen 240 en 360 °C en is van sedimentêre oorsprong waar dit
moontlik deur metamorfose van die reeds gemetamorfiseerde Malmesbury gesteentes
vrygestel is.
Die tegniek van kapillêre elektroforese is vir die toepassing daarvan in die analise van
vloeistof insluitsels in kwarts geëvalueer, terwyl die vloeistof vrystellingsmetode van Bottrell
en Yardley (1988) vir hierdie tegniek geoptimaliseer is. Kontaminasie faktore is geïdentifiseer
en verminder of uitgeskakel waar moontlik. Daar is getoon dat die vloeistof chemie, wat
verteenwoordigend is van al die insluitsel populasies in 'n monster, wel bruikbaar is t.o.v.
afsonderlike vloeistof generasies, solank elke populasie individueel bestudeer is om die
omvattende chemiese data te verduidelik en met 'n enkele populasie te korrelleer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51751 |
| Date | 12 1900 |
| Creators | Martin, Riana Theresa |
| Contributors | Hallbauer, D. K., Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 104 p. |
| Rights | Stellenbosch University |
Page generated in 0.0022 seconds