The geology and petrology of the Marble Delta
Date
1973-02
Authors
Otto, J. D. T.
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
The Marble Delta is an area of approximately 40 sq. km in Natal (30°22' Long., 30°40' Lat.), occupied by Precambrian marble and associated granites. The deeply dissected country was geologically mapped on a scale of I : 6 000. A new lithostratigraphic
classification of the metasediments is proposed.
The base of the lowermost Le Joncguet Formation (composed of
dolomitic marble and siliceous beds) is not exposed. This is
followed by the predominantly ca.lcitic Oribi Formation with
interbedded dolomite and graphitic layers. The marble is
unconformably overlain by the Cherrywillingham Formation which
comprises mainly amphibolite and granulite. The .three formations
together constitute the Marble Delta Group.
The main petrological units are calc-silicate marble,
metaquartzite, dolomite marble, cluster serpen~ine marble and
ce,lcite marble. Graphite layers are considered to have originated
in situ from organic remains; there is occasional evidence
of ionic transfer of carbon from this graphite by magmatic
fluids. The common mineral assemblages are diopside +
calcite + dolomite, tremolite + calcite + diopside + quartz,
calcite + quartz + dolomite, forsterite + calcite + dolomite,
plagioclase + cordierite + garnet + quartz, amphibole + clinopyroxene
+ plagioclase, hornblende + clinopyroxene + calcite,
wollastor~te + calcite + diopside. Other minerals are graphite,
antigorite, chrysotile, sphene, spinel, clinohumite, chondrodite,
zoisite, clinozoisite, hedenbergite, phlogopite, ilmenite,
hercynite, dravite, cummingtonite, talc, apatite, microcline,
saponite. The mineral assemblages resulted from regional
metamorphism and polyphase contact metamorphism.
Description
Thesis (MSc) -- Stellenbosch University, 1973.
Keywords
Geology -- South Africa -- Marble River Delta, Petrology -- South Africa -- Marble River Delta, Theses -- Earth sciences, Dissertations -- Earth sciences