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the exploration right is held by Glenover and is part of a joint
venture with Galileo Resources. The Xiluvo REE Project is located
in Mozambique and lies within a mining license held by Promac lda.
Geological setting
Naturally REE-enriched sources are alkaline volcanic and
intrusive rocks. Carbonatites are the most REE-enriched group
of igneous rocks, yet only one REE deposit is considered entirely
magmatic: the Mountain Pass Deposit in the US. The most
common occurrence of REE is associated with carbonatites. The
highest REE concentrations are typically encountered in iron-
rich dolomitic carbonatite varieties; that is, those with ferroan
dolomite to ankerite as the main carbonate phase, sometimes
accompanied by siderite.
REEs are effectively concentrated in residual deposits such as
laterites produced by prolonged tropical weathering. In carbonatites,
chemical weathering causes the breakdown of the main minerals.
Dissolution of the carbonate phases and apatite releases the REEs,
which are subsequently incorporated into new REE supergene
phosphate and carbonate minerals such as monazite and/or
bastnaesite. REE enrichments achieved in these residual deposits are
typically 5–10 times those in the original source rock.
China’s near-monopolistic domination of the world rare earth
market was due to the discovery of REE ion-adsorption clays.
Deep weathering of granitic and acid volcanic rocks without
associated denudation, has generated weathering profiles rich
in clays. REE released during the breakdown of REE-bearing
accessory phases in the protolith are adsorbed onto kaolinitic and
halloysitic clay minerals and retained.
The interest in rare earth elements (REEs)
continues to spread due to increasing
dependency on it from the technology sector.
Due to the complex nature of these deposits,
investors need to take care when considering
projects, writes Nicolaas C Steenkamp.
complex in Zambia has been noted as a significant deposit
while Wigu Hill in Tanzania is held by Montero Mining and
Exploration. The Ngualla Hill REE deposit, also in Tanzania, is
being developed by Peak Resources.
Mrima Hill, one of a cluster of carbonatite and alkaline intrusions
in Kenya, was covered by a special mining lease held by Cortec
Mining Kenya, but the licence was recently revoked. Developer
Namibia Rare Earths holds the exclusive prospecting license for
the Lofdal REE project in Namibia.
The Zandkopsdrift Project in South Africa is managed by Frontier
Rare Earths. The Glenover Complex is also in South Africa, and
www.africanmining.co.za
Historically mined REE deposits are generally associated with
mineral sands deposits produced mainly from monazite. The REE
mineral content of these heavy mineral sands is around 1%. REE-
bearing accessory phases such as zircon, monazite, and xenotime, are
common in crustal granitoids and are refractory during weathering; as
such, they are a common constituent of heavy mineral sand placers.
The REEs are subdivided into ‘light’ (LREE) and ‘heavy’
(HREE). The LREEs are dominantly hosted in bastnaesite
and monazite and lesser fluoro-carbonates. Lateritic deposits
tend to be more HREE enriched. These HREEs are derived
from secondary processes and are loosely bound via adsorption
processes within clay minerals.
Applications of REEs
There are 17 REEs that vary in scarcity and in their
applications. Rare earths are used to make strong permanent
magnets which, in turn, are used in the electric motors that
provide power for appliances, robots, and electric vehicles
(EVs). REEs are also playing a role in the renewable energy
development sector. The magnets used in wind turbines are
also made of REEs. High-strength neodymium magnets
are used in industries such as electrical motor manufacture,
medical science, and renewable energy. It is used in commercial
products, such as headphones, cellular phone speakers, and
microphones.
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