Summary:
The Manono Lithium tailings are technogenic deposits, created from the processing of material from the Manono-Kitolo deposit, which was mined from 1919 to the mid-1980’s for tin and columbite-tantalite (coltan). Nine out of the eleven tailings were drilled, of which five form this Mineral Resource Estimate. The tailings deposits stretch over a length of 12 km, in a northeast-southwest direction, immediately adjacent to the mined pits. Several of the deposits consist of a mixture of material types, typically pegmatite and laterite, with some clay material being present in minor quantities in specific deposits.
The deposits are named alphabetically, with a suffix used to differentiate between coarse (c) and fine (f) material. The nine tailings that make up the project are from north to south named Cc, Cf, Ec, Hc, Hf, Gc, Gf, Ic and K.
The lithium mineralisation is primarily hosted in spodumene with minor lepidolite. Tin mineralisation is hosted in cassiterite and tantalum in tantalite.
Project Geology
The Manono Lithium Tailings Project is composed of nine coarse tailings dumps and fine tailings terraces produced from mining and processing of material from the various Manono-Kitotolo open pits. The tailings material is typically coarse, ranging from 1 mm to 5 mm sized gravel.
The material composition of each tailings deposit varies, with many being composed of a combination of pegmatite, laterite and/or clay material. The contrast of the two material types is noticeable with the reddish-brown laterites juxtaposed against white pegmatite material. The J deposit is visible in background which consists exclusively of laterite material.
Few deposits appear to consist of a single material type, the exception to this being the K-dump which is primarily composed of pegmatite. The K-dump consists of tailings lying over a flat area 675 m by 500 m in extent, with depths up to 15 m in the centre, gradually thinning out to 3 m along the edges. Stacked tailings, up to 20 m high are located in the northwest corner of the K-dump, while stacked tailings in a cone-like shaped feature are found in the east of the deposit, attaining a maximum thickness of 45 m.
Fine vegetation, consisting of shrubs and tall grass, covers the majority of the tailings deposits. This tends to be thicker in the lower lying tailings of the K, Gf and Hf deposits. Some deposits show evidence of historical and recent artisanal mining activity for cassiterite and coltan as observed by the disturbed ground in the foreground.
Deposit type
The Manono Lithium Tailings Project is composed of the reject LCT (Lithium-Caesium-Tantalum) pegmatite material processed at the Manono-Kitotolo mine from 1919 to the mid-1980s. Technogenic deposits are a category of superficial formations created by anthropogenic direct or induced depositional processes.
Tailings from the Manono-Kitotolo open pits were deposited on the ground adjacent to the various open pits. The coarse tailings were deposited over many years into raised heaps that reach heights up to 70 m above surface. The fine tailings material was deposited into flat terraces adjacent to the coarse tailings dumps.
Many of the tailings deposits are composite in nature, consisting of layers of pegmatite, laterite and/or clay layers. These were deposited by mechanical means, including most of the deposits denoted as “fines”, with the exception of the Hf and Gf deposits, which are assumed to have formed due to the settling of fine material in standing ponds of water as evidenced by the presence of clay layers in these deposits.
Technogenic deposits such as those at Manono are typical of many mining operations across the globe and often contain concentrations of various metals of economic value due to incomplete recovery during the processing of the raw, in-situ source material. Their extents and depths tend to be well defined and due to their recent formation, the only processes affecting their evolution is erosion due to fluvial or aeolian processes.
Mineralisation
The Manono-Kitotolo mine exploited a large pegmatite deposit that produced between 140,000 tonnes and 185,000 tonnes of tin and 4,500 tonnes of coltan concentrate (Scholtz, 2019). The reject processed material was deposited on the coarse tailings dumps and fine tailings terraces that make up the Manono Lithium Tailings Project.
Lithium is present in the minerals spodumene and lepidolite, and tin is present in cassiterite. The tailings still contain cassiterite currently being mined by artisanal miners. The majority of the pegmatites mined also contain spodumene (and/or lepidolite) and the minerals can be visually identified in the material on the coarse tailings dumps (Scholtz, 2019). The relatively high grade of lithium in spodumene was analysed in two grab samples by BRGM (1.7% to 2% Li2O) and indicates that lithium was likely not recovered during historical processing (Scholtz, 2019).