Rare
earth element mineralization in South Africa occurs in heavy mineral
sand deposits, in pegmatites and granites of the Namaqualand
Metamorpic Complex, in carbonatites and alkaline complexes and in the
fluorite-bearing rocks associated with the Bushveld Igneous Complex.
South
Africa’s known and demonstrated recoverable reserves were estimated
in 1988 at 2.187 million metric tons of REO in two deposits; placer
monazite at Richards Bay and rare earth bearing apatite at the
Phalaborwa Complex (Van der Vyver, G P: Resources of Rare Earths in
South Africa, Minerals Bureau, 1988).
These
reserves, at the time, placed South Africa third in the world after
China and the USA, but South Africa never developed a rare earth
mining and refining industry. The other known occurrences in South
Africa have not been adequately explored to be classified as
demonstrated resources.
Although
South Africa produced rare earth-bearing monazite concentrates at
Richards Bay Minerals (RBM), production stopped before 2003 and RBM,
like Ticor and Namakwa Sands, currently recovers only ilmenite,
rutile and zircon.
The
rare earth-bearing apatite concentrates of Phalaborwa have been
investigated by MINTEK repeatedly with the view of producing rare
earth oxides.
The
Steenkampskraal monazite mine at Van Rynsdorp in Namaqualand,
operated from 1952 to 1963, producing a monazite concentrate that was
sold mostly for its thorium content rather than its rare earth
content. It was the largest thorium source in the world during the
years 1951 to 1963.
Richards
Bay Minerals
Placer-type
deposit with monazite plus thorium and consequently with a
radioactive hazard problem.
Richards Bay Minerals (RBM), jointly owned by Billiton and Rio Tinto, is the
largest single producer of titanium in the world from heavy mineral
deposits. RBM now accounts for about 25% of world output of
titanium feedstocks (titania slag and rutile), 33% of world zircon
output and 25% of high purity pig iron. The sand deposits contain
REE-bearing monazite and the
recoverable resource was estimated at 27,500 tonnes REO in 1988.
Phalaborwa
Complex
Carbonatite-type
deposit with a low-grade, high tonnage potential
The
Phalaborwa Complex is a zoned pyroxenite-syenite-carbonatite
intrusion located on four farms in Mpumalanga Province. It hosts
South Africa’s largest copper mine and produces, in addition,
magnetite, sulphuric acid, zirconia, uranium, precious metals,
vermiculite (Rio Tinto) and phosphate (FOSKOR).
The
REE occur mainly in the phosphate mineral apatite and the P2O5content
varies from 6% to 8% within the pyroxenites and the foskorite
(altered magnetite-olivine-apatite carbonatite). Rio Tnto’s
Palabora Mining Company has a standing contractual arrangement
whereby the apatite concentrates are delivered to FOSKOR for the
production of phosphate in exchange for copper concentrates from
FOSKOR. The
apatite concentrate contains on average 0.5% rare earth oxides. The
total recoverable resource has been estimated at 2,160, 000 tonnes
REO.
The europium content
is in excess of 1% in the rare earth concentrates and the
thorium oxide content of the rare earth concentrates is below 200
ppm. FOSKOR’s associated company, Sentrachem, conducted various
investigations and tests by MINTEK on the concentrates with the view
of recovering the individual rare earths.
Steenkampskraal
monazite mine
Pegmatite-type
deposit with limited tonnage potential
The
Steenkampskraal monazite deposit occurs in a sequence of highly
metamorphosed crystalline gneisses of the Roodewal Suite of the
Namaqualand Metamorphic Complex. The rocks are the host in which the
pegmatite ore body occurs. The monazite-bearing ore body is tabular
in shape with an undulating form and a thickness varying from 30 cm
to 90 cm.Minerals present in the ore body include monazite, quartz,
apatite and magnetite with small amounts of zircon, pyrite,
chalcopyrite, galena and ilmenite. The monazite is the source of the
rare earths. The
average in situ grade is 16.74% REO, 0.8% Cu, 0.5g/t Au and
6.0g/t Ag. The initial estimated reserve was 20 00 tonnes REO.
Subequently it was estimated
that
Steenkampskraal hosted a resource of 131 500 t of rare-earth minerals
in the indicated and inferred categories, with about 37 500 t of
resources located in the upper and lower tailings dams
Other
carbonatites and alkaline complexes with rare earth element
mineralization.
Mineralized
carbonatites usually contain a high concentration of the so-called
light rare earth elements lanthanum,
cerium, neodymium, praseodymium and samaruim. The
minerals containing the rare earths occur dispersed in the
calcite (Ca-rich), and, dolomite (Mg-rich) and ankerite (Fe-rich)
forming the bulk of the carbonatite.
If
a carbonatite or complex consists of multiple intrusions or phases,
the rare earth element content tends to increase in the youngest
phases. Apatite is considered to be an accessory phase of
carbonatites and contains substantial rare earth elements remobilised
by hydrothermal fluids.
The
rare earth minerals bastnaesite, parisite and synchisite are
considered to be supergene, i. e. formed at shallow depth by the
action of groundwater. (Mountain Pass in California and Mt Weld in
Australia, where the ore-grade mineralization occurs between 30
metres and 60 metres below the present-day surface, are examples
where the supergene enriched portions of the carbonatites are of
economic interest).
The
Glenover Carbonatite Complex
The
Glenover Carbonatite Complex, 80km north-northwest of Thabazimbi,
comprises an oval shaped, poorly exposed pyroxenite and carbonatite
body, 4.7 km long and 3.5 km wide. Monazite is bound in a
coarse-grained sövite (Ca-rich) and magnesio-carbonatite.
Associated
minerals include apatite, magnetite, phlogopite and pyrochlore.
Associated secondary minerals include quartz, synchisite,
fluorite, barite, monazite and columbite. The presence of synchisite
could indicate supergene enrichment in rare earth mineralization of
the brecciated complex, but there is no information available on the
distribution of the rare earth minerals.
Aim-listed
Galileo
Resources
was considering the options for its 34%-owned Glenover rare
earth/phosphate project, in Limpopo, South Africa in 2018
The
Kruidfontein Complex
The
Kruidfontein Complex is situated approximately 130km north-northwest
of Pretoria. It has a caldera structure, along a NW-striking regional
fault. The carbonatites represent the last stage of extrusive
activity of the Kruidfontein Complex.
Rare
earths associated with fluorite (CaF2)
mineralization occur associated with the intrusive (fluorite-rich
dykes and plugs) and extrusive (replacement and disseminated ore)
carbonatitic rocks.
A
large tabular stratiform ore body occurs in the southwestern part of
the Complex, and contains an average of 30% CaF2.
Fluorite occurs disseminated throughout the inner zone with
concentrations not exceeding 10% CaF2.
Analytical results from the inner zone show that the fluorite
contains La2O3 in
variable concentrations between 0.02 and 0.15 wt%.
The
Pilanesberg Complex
Rare
earths are found in alkaline rocks of Pilanesberg on Thabayadiotsa on
the farms Houwater 54, Rhenosterspruit 59 and Saulspoort 38.
Rare
earth mineralization on Houwater 54 occurs as veins in the contact
zone between a tinguaite ring dyke and younger foyaite, On the farm
Rhenosterspruit 59, rare earth mineralization occurs in tuff bands
intercalated with lava over a distance of 2 km. On the farm
Saulspoort 38, rare earth mineralization occurs as veins in a white
foyaite. Yttrium and REE are concentrated in britholite
((Ce,Ca,Th,La,Nd)5(SiO4,PO4)3(OH,F) ) veins and britholite-bearing
foyaite. High grade mineralization consists of britholite
containining 56.36% REO and 1.56% ThO2 and
magnetite with minor amounts of allanite, apatite, calcite,
strontianite, fluorite, aegirine and cheralite.
The
reserves have been estimated at 13.5 Mt at 0.7% REO +ThO2,
1.2 Mt at 6.54% REO +ThO2,
and 24 000t at 10% REO+ThO2.
The
Vergenoeg magnetite-fluorite deposit
The
Vergenoeg breccia pipe is located in Gauteng Province approximately
80 kilometers northeast of Pretoria. Vergenoeg is a fluorite-bearing
massive iron oxide deposit that is genetically related to granites of
the Bushveld Complex.
The
deposit is a funnel-shaped breccia pipe, with a diameter of 900 m
(north-northwest) to 700 m (east-northeast) on surface, which
contains fluorite, apatite, ilmenite and magnetite.
Vergenoeg
is a fluorite mine, despite the large volumes of magnetite and has
produced fluorite since 1956. The fluorite ore body, up to a depth of
360 m has a resource estimate of 174 Mt at 28.1% CaF2.
The iron resource is in the order of 195 Mt at 42% Fe.
Mining
has been focused on the upper part of the pipe-shaped body (porous
botryoidal hematite-goethite gossan). The gossan contains resistant
minerals such as cassiterite, apatite and rare earth carbonates.
Siderite
is often found with the REE minerals, normally occurring in veinlets
and coarse-grained masses. REE minerals in the upper part of the pipe
may have originated from remobilization of allanite from the lower
part of the pipe.
Similarly
remobilization might have resulted in the REE mineralization seen in
the siderite veins and interstitial grains between apatite laths,
including monazite.
The
primary assemblage of minerals in the lower part of the Vergenoeg
pipe comprises mainly of fluorite, ilmenite and fayalite (Fe2SiO4)
with minor pyrrhotite, apatite and allanite. Allanite is the most
common REE-bearing mineral in the primary mineral assemblage and are
intergrown with fayalite and ilmenite.
Similarities
with Phalaborwa and also with Bayan Obo, Mongolia, indicate that the
Vergenoeg pegmatoid pipe could be an extreme carbonatite-associated
member of the Fe-oxide Cu–Au (±REE±P) group of deposits. (Goff,
B. H., Weinberg, R, Groves, D. I.; Vielreicher, N.
M.; Fourie, P. J.: The giant Vergenoeg fluorite deposit in a
magnetite–fluorite–fayalite REE pipe: a hydrothermally-altered
carbonatite-related pegmatoid?; Mineralogy
and Petrology, Volume
80, Numbers 3-4, March 2004 , pp. 173-199).
The
Buffalo Fluorspar Deposit
The
deposit is situated about 75 km north of Vergenoeg near Mookgopong
(formerly Naboomspruit) in Limpopo Province and contains fluorite
veins which cut through altered rhyolite of the Rooiberg Group, which
is surrounded by the Bushveld Complex granite. Buffalo fluorite mine
was mothballed in October 2008 due to market circumstances. Ongoing
empirical test work to reduce the phosphorous content of its product
was in progress. In addition, test work on the fines from the
substantial aggregate dumps on the neighbouring property continued.
If either of these projects are revived and proves successful,
Buffalo could be re-opened.
One
of the opportunities at Buffalo that Sallies Ltd, the previous owner,
planned to investigate further, was the rare earth minerals contained
within tailings.
During
2009 Firebird Global Master Fund, Ltd (Incorporated in the Cayman
Islands) made a successful offer for the shares that they did not
already owned.
The
Zandkops Drift Complex
The
pipe-like vermiculite-calcite-limonite body is located approximately
26 km southwest of Garies, in the Northern Cape. Pyrochlore and
secondary REE mineralization is associated with manganoan calcite,
goyazite, gorceixite, carbonate-apatite, betafite, uraninite, and
niobium rutile.
A
bulk sample assayed 2.6% P2O5, 900
ppm Nb, 0.069 kg/t U3O8,0.197
kg/t ThO2, 1.2
%REO+ThO2 and
320 ppm Mo, but beneficiation tests yielded disappointing results.
