ZIMBABWE
Geography
Zimbabwe is a landlocked country in south-east Africa. To the south, Zimbabwe is separated from
South Africa by the Limpopo River; the north-western border is defined by the Zambezi River.
Zimbabwe’s highest peak is Mount Nyangani (2592 m), which is located within the Nyanga National
Park in the east of the country. Zimbabwe’s lowest elevation, 162 m, lies to the south-east, at the
junction of the Runde and Save Rivers, on the border with Mozambique.
Zimbabwe’s climate is tropical, although this is moderated by elevation. The rainy season extends
from November to March. The terrain is mostly high plateau, with a higher central plateau and a
mountainous range in the east.
Mineral exports and agriculture are the main foreign currency contributors to Zimbabwe. The country
has reserves of metallurgical grade chromite and other commercial mineral deposits include coal,
asbestos, copper, diamonds, nickel, gold, platinum and iron [1].
Geology
Zimbabwe is underlain by a core of Archean basement known as the Zimbabwe Craton, which is
intruded by the famous Great Dyke, a SSW–NNE trending ultramafic/mafic dyke complex. The
craton is principally composed of granitoids, schists and gneisses and greenstone belts. It is overlain
in the north, northwest and east by Proterozoic and Phanerozoic sedimentary basins (Figure 1) [2].
FIG. 1. Regional geological setting of Zimbabwe showing the distribution of selected uranium deposits and
occurrences. For the general uranium deposit and occurrence legend see World Uranium Geology,
Exploration, Resources and Production, IAEA, 2020. A general global geological legend is shown although not
all geological units necessarily occur on this particular map.
The eastern half of Zimbabwe comprises the Archaean Rhodesian cratonic nucleus, a 3600–2600 Ma
block of granites, gneiss and charnockite domes containing greenstone belts. The low metamorphic
grade greenstone belts are intruded by late potassic granites, porphyries and sodic tonalites.
The cratonic trends are transected by the N–S trending Great Dyke (2530 Ma). The craton is
surrounded by Proterozoic mobile belts where, formerly, broadly similar basement rocks have been
metamorphosed, deformed and granitized.
In the west of the craton, Lower Proterozoic–Middle Proterozoic sediments rest on the basement.
These have been compared to the Katanga–Copperbelt Series of the Democratic Republic of the
Congo and Zambia, and with the Nama–Transvaal Series of South Africa. The sediments are
somewhat different from the Copperbelt, as no carbonates are reported, although volcanics are
present. The degree of metamorphism is also higher, locally reaching amphibolite facies. The rocks
consist of basal sequences of conglomerates, overlain by lavas, conglomerates, arkoses, sandstones
and schists. Copper is disseminated in the upper arkoses and conglomerates, below the schists and
above the lavas.
The various Precambrian rocks are overlain unconformably by Karoo sediments of Carboniferous–
Triassic age. Small outliers occur well into the craton, but the Karoo is largely confined to
downfaulted or downwarped grabens and basins. The rocks are mainly arenites, conglomerates, shales
and coals, with both oxidized and reduced facies. In the north and west, in the Zambezi graben, they
crop out over an area of around 78 000 km². However, in the west and, more particularly, the south,
the Karoo consists predominantly of basalts with thin interbedded sedimentary sequences. In the
south-east, there is a small area of Jurassic continental and marine sediments, while in the west, Karoo
strata are overlain by Eocene aeolian Kalahari sands, which blanket the bedrock geology. Large
Tertiary syenite–granite complexes occur in the south-east along the margins of the Limpopo graben.
Small, shallow Quaternary sedimentary basins occur in the centre, west and south-east of the country
[2, 3].
Uranium exploration
Uranium exploration was started in Zimbabwe in an ad hoc manner in the early 1950s by numerous
private prospectors. Many radioactive anomalies were found at that time, mainly associated with
pegmatite in the basement complex and in Proterozoic terrain, as well as within Karoo sediments. In
the mid-1950s, the United Kingdom Atomic Energy Authority (UKAEA) commenced a
comprehensive search for radioactive minerals but with very limited success. A guarantee purchase
programme for uranium ores undertaken to stimulate prospecting and mining generated only one
shipment of 300 t of ore grading 0.255% U, yielding 0.77 tU. This came from a mineralized fault zone
in granite. The UKAEA programme also included an airborne radiometric survey covering 17 000
km². During this time, private companies also engaged in systematic exploration ventures consisting
of airborne and ground surveys and selective core drilling. A variety of geological environments were
investigated, although with very little success.
In 1969, Karoo Group sediments were explored under three Exclusive Prospecting Orders. Attention
focused on the heavy mineral content of various conglomerates, but the only radioactive mineral
found was monazite. In 1972, the Messina Development Co. Ltd discovered a large radioactive
anomaly during an airborne survey in the Sabi Valley, but ground follow-up, including drilling, failed
to identify the cause of the anomaly. In 1976, Gold Field Prospecting Co. (Pty) Ltd examined the
granitic terrain of the Chinamora batholith, located 30 km north-east of Salisbury. Both airborne and
ground surveys were conducted. However, the only anomalies detected were from weakly radioactive
alaskite dykes.
Modern uranium exploration in Zimbabwe started in 1981, when a gamma spectrometric airborne
survey was flown over the entire Zambezi valley using fixed wing aircraft. The purpose of the survey
was the evaluation of the Karoo System strata. To verify and screen anomalies identified by the
airborne survey, a follow-up helicopter-borne and ground-based survey was conducted in 1982. The
German company Interuran, formerly named Saarberg Interplan Uran, was one of the companies
involved and it focused work on the Kanyemba area. In 1983–1987, additional work was completed
on all verified anomalies. Following discovery of the Kanyemba-1 deposit, a detailed evaluation was
initiated. Between 1985 and 1990, exploration and delineation drilling, as well as technical studies on
hydrogeology, rock mechanics, ore processing, mining, etc., were completed. A prefeasibility study
was also completed using this information.
Exploration activities for the Kanyemba-1 deposit were achieved by the end of 1991. During 1991–
1992, a technical feasibility study was completed. An environmental impact study was started,
including the collection of baseline data on the hydrogeology, radon flux, dosimetry and micro-
meteorology of the area.
Owing to the depressed international uranium market, which adversely impacted the feasibility of the
Kanyemba project, all activities were terminated at the end of 1992 [3].
Figure 2 summarises historical exploration data, for a total of USD $6.9 million, including 28 562
metres of drilling and 24 400 km2 of airborne radiometric surveys.
FIG. 2. Domestic uranium exploration data for Zimbabwe. Comparison of exploration expenditures, drilling
and uranium market price (US$ current) [4–11].
Uranium resources
Identified resources
Zimbabwe’s identified resources (reasonably assured resources) are 1800 tU (in situ) with a
recoverable cost of up to US $80/kgU and an average grade of 0.6% U. The resources are associated
with the Kanyemba-1 deposit located in the northern part of the country, near the border with
Mozambique. The deposit consists of several lens shaped bodies, 0.20–3 m thick, 20–100 m wide and
up to 600 m long. It is a tabular deposit occurring in sandstones of the Upper Pebbly Arkose
Formation (Upper Triassic) of the Upper Karoo System. The sandstone host rock was deposited by a
meandering fluvial system.
The 2018 Red Book indicates 1400 tU as reasonably assured resources recoverable in the $130-
260/kg cost category.
Undiscovered resources
Zimbabwe does not report any estimated additional resources (EAR-II). However, it has reported
speculative resources of 25 000 tU recoverable at <US$130/kgU. These resources are associated with
sedimentary rocks of the Permian–Lower Jurassic Karoo System. In 1983, IUREP reported
speculative resources of 10 000–50 000 tU, hosted in sandstone and magmatic environments [52.12].
The 2018 Red Book indicates 25 000 tU as speculative resources.
Potential for new discoveries
The 7800 km² of overlying Lomagundian platform sediments are regarded as the best Precambrian
target. In these, around Sinoia, disseminated copper mineralization occurs in association with
metamorphosed lavas and schists at the base of a thick clastic sequence. In the Molly mine, uraninite
and secondaries are patchily dispersed, antipathetically to copper in the sediments in the vicinity of
intrusive pegmatites. It has been suggested that the rocks of low metamorphic grade in this series
possess uranium potential. However, to the north, where the series is metamorphosed up to
amphibolite facies, it is likely to be barren. The Karoo Group sandstones crop out over an area of
90 500 km² and must be considered to have some potential based on the general premise for
exploration applied in other parts of southern Africa.
Minor occurrences of pitchblende and secondary uranium minerals have been located in the Wankie
coalfield and near Sebungwe, in the NE–SW post-Karoo faults. The major problem in prospecting
these sediments is poor exposure due to laterization and subdued topography. The Karoo consists of
sandstone/shale/conglomerate intercalations of continental origin, in reduced and oxidized facies, with
coals and organic debris. This is a highly favourable situation for the concentration of uranium in
reduced zones in the porous sections of the sequences. In the west and south of the country, the Karoo
rocks are dominantly basalts, but the basal sediments may well be worthy of examination. Small
outliers in the craton could also be worthy of examination. In the same general area, two syenite–
phonolite complexes could have minor potential for uranium as a co-product with monazite and rare
earth minerals.
In the west, the Karoo is overlain by Eocene Kalahari sands. On the basis of the broad observations of
increasing aridity towards the Botswana border, and on the intermittent nature of drainage both now
and in the past, duricretes could well be developed in this area. If a source of uranium is available for
their formation, calcrete deposits of the Yeeleerie–Swakopmund type could occur. However, younger
sands could mask orebodies in the Karoo. The coarser zones of Quaternary sediments might be
worthy of examination where the underlying rocks can be shown to be uraniferous.
The main uranium potential of Zimbabwe is undoubtedly in the north-western one third of the
country, to some extent in low grade metamorphosed Lomagundi (Precambrian) Copperbelt type
platform sediments, but more particularly in the extensive areas of poorly exposed Karoo sediments
[3].
Uranium production
Three hundred tonnes of ore, containing 0.77 tU, were produced in the 1950s. The Kanyemba-1
deposit, with known resources of 1800 tU in the <US $80/kgU cost category, could, under favourable
market conditions, support a production centre. Feasibility studies completed in the early 1990s
provided plans for the construction of such a centre, with a production capability of 350 tU/year.
On 24 April 2010, a press report stated that the Government of the Islamic Republic of Iran had
entered into an agreement with the Government of Zimbabwe to develop and mine the Kanyemba-1
deposit [13].
References
[1] CENTRAL INTELLIGENCE AGENCY, The World Factbook: Zimbabwe, Washington, DC (2008),
https://www.cia.gov/library/publications/the-world-factbook/index.html
[2] SCHLÜTER, T., Geological Atlas of Africa, 2nd edn, Springer, Berlin and Heidelberg (2008) 274–278.
[3] JOINT STEERING GROUP ON URANIUM RESOURCES, World Uranium: Geology and Resource Potential,
Miller Freeman Publications, Inc., San Francisco (1980) 524 pp.
[4] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium
Resources, Production and Demand, OECD, Paris (1977).
[5] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium
Resources, Production and Demand, OECD, Paris (1979).
[6] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium
Resources, Production and Demand, OECD, Paris (1982).
[7] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium
Resources, Production and Demand, OECD, Paris (1983).
[8] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium
Resources, Production and Demand, OECD, Paris (1986).
[9] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium
Resources, Production and Demand, OECD, Paris (1988).
[10] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium
Resources, Production and Demand, OECD, Paris (1990).
[11] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY
AGENCY, Uranium 1991: Resources, Production and Demand, OECD, Paris (1992).
[12] INTERNATIONAL ATOMIC ENERGY AGENCY, Speculative Resources of Uranium, A Review of IUREP
Estimates 1982–83, IAEA, Vienna (1983).
[13] MUSHEKWE, I., ALEXANDER, H., Iran strikes secret nuclear mining deal with Zimbabwe’s Mugabe regime,
The Daily Telegraph (24 Apr. 2010).
Updated from INTERNATIONAL ATOMIC ENERGY AGENCY, World Uranium Geology, Exploration, Resources and Production, IAEA, Vienna (2020) by M. Fairclough (December 2020)
