Impact Minerals Limited (Impact Minerals) has commenced a significant exploration programme for uranium on its extensive areas of prospecting licenses of more than 27,000 square kilometers in Botswana. Impact Minerals’ prospecting licences cover 350 km of the strike extensions of rocks that host many significant uranium deposits throughout southern Africa, including the adjacent uranium deposits owned by A-Cap Resources Limited (A-Cap) at the Letlhakane Project near Serule.
Here A-Cap has reported an Inferred Resource of 98 Mlb of uranium oxide at an average grade of 158 ppm at a cut-off grade of 100 ppm, in deposits hosted by near-surface calcrete and by Karoo Group sedimentary rocks. A bankable feasibility study on the Letlhakane Project is in progress.
Polo Resources Limited, Impact Minerals’ shareholder, also has about a 19% shareholding in A-Cap.
Impact’s licences are prospective for three types of uranium deposits:
Deposits hosted by Karoo sedimentary rocks, which host a number of large uranium deposits throughout southern Africa, including at Letlhakane;
Uranium hosted by calcrete in Cainozoic palaeochannels, a style of mineralisation well known in Australia and Namibia; and
Deposits within playa (salt) lakes which, in Australia and elsewhere in Africa, are known to host significant uranium deposits.
Impact Minerals has identified 18 such target areas with a combined strike length of more than 400 km within its licences. These generally comprise elongate regions within which there are variably exposed calcrete outcrops and/or outcrops of prospective Karoo sedimentary rocks. Many have elevated surface uranium responses in the regional airborne radiometric data and in ground spectrometer readings.
Five of these target areas have been prioritised for follow-up work on the basis of the widespread surface uranium anomalism in calcretes and sandstones, backed by regional mapping, ground reconnaissance work and sampling. These are called Sua, Lekolobo, Kodibeleng, Ikongwe and Shoshong.
Large soil geochemistry programmes on these targets are in progress to identify specific drill targets, with the aim of drilling at least two of these prior to year end, subject to weather constraints and access during the summer wet season.
Priority Target Areas
Lekolobo: calcrete and Karoo sandstone targets adjacent to the Letlhakane Project The Lekolobo target area is south of and adjacent to A-Cap’s Letlhakane Project. These licences cover the interpreted south western extension of the uranium mineralisation at Letlhakane, including the recently discovered prospects at Serule West and Serule East. Impact Minerals’s target is defined at surface by a 12 km long area of up to 20 ppm eU in the airborne radiometric data.
At Letlhakane the Karoo-hosted primary uranium mineralisation occurs in a fault-bounded sedimentary basin as well as in Karoo-aged palaeochannels that feed into this basin and which are recognisable in the radiometric data.
The western and south western extensions of the uranium mineralisation at Letlhakane disappear under younger cover rocks, calcrete and alluvium towards Impact Minerals’ tenements.
At Impact Minerals’s Lekolobo target area the geological setting is similar to that at Letlhakane. Outcrops of Karoo sandstone contain up to 66 ppm eU* (measured with a portable spectrometer) and are interpreted to be part of a west-draining Karoo palaeochannel that enters a sedimentary basin hidden beneath the Kalahari sand and calcrete.
Kodibeleng – Ikongwe – Shoshong: 80 km of calcrete palaeo channels These three target areas are each at least 20 km long and interpreted as Kalahari palaeochannels containing calcrete. They are buried by up to five metres of sand and soil and are prospective for calcrete-hosted uranium deposits such as Yeelirrie in Western Australia and Langer Heinrich in Namibia.
The headwaters of all three channels drain from Archaean, Proterozoic and Karoo-aged rocks that all contain elevated uranium values of up to 80 ppm eU (measured with a portable spectrometer). Such uranium-enriched rocks comprise a fertile source for uranium that may deposit in the younger channels.
At one locality in the Kodibeleng palaeochannel the calcrete has been eroded to reveal up to 3 m of calcreted Kalahari sandstones and conglomerates which at the base contain up to 35 ppm eU (measured with a portable spectrometer), that is, a ten times greater response than at surface.
Sua: airborne radiometric uranium anomalies covering more than 200 sq km The Sua target area comprises two very large anomalies 200 sq km in extent, of elevated uranium values up to 10 ppm eU identified in the regional airborne radiometric data.
The eastern anomaly is 12 km long and up to five km wide, and the western anomaly is 20 km long by 15 km wide and probably continues to the west. Soil profiles exposed in shallow trenches within the western area have uranium values up to 15 ppm eU (as measured with a portable spectrometer) for up to 2 metres below surface. This indicates that the uranium is not a surficial feature and may represent a soil anomaly over a larger source at depth.
The Sua target has similarities to the Manyoni Project in Tanzania (owned by Uranex NL) where uranium mineralisation has been discovered 2 m below the surface of playa lakes. Here Uranex have reported an Inferred Resource of 46 Mt at 151 ppm uranium oxide (100 ppm cut-off grade) for a contained 15 Mlb of uranium oxide within an area of about fivesquare kilometres.
Impact Minerals’ targets in Botswana have the potential to host very large deposits of uranium mineralisation in a country ranked in first place by the Fraser Institute in its 2009 survey of Mining jurisdictions in Africa.