Australia-based exploration company Uranex started a drilling programme at its Nachu graphite tenement in south-east Tanzania late last month after successfully completing an electromagnetic (EM) survey.

The EM survey results of the 147 km2 of land surveyed indicates a 5.5 km2 of highly conductive zones on the tenement. These promising results indicate that there is a strong possibility of a significant graphite resource on the tenement, Uranex CEO Rod Chittenden tells Mining Weekly.

The EM survey areas were calculated based on an 888 Hz frequency, which is indicative of the conductivity at a depth greater than 35 m. The area covered by the EM survey accounts for 63% of the strike length of mineralisation indicated by the outcrop sampling.

The results from the interpretation of the other frequencies used in the EM survey show that these conductor zones are reasonably continuous from just below the surface to depths of more than 45 m.

The EM drilling programme will continue to cover the area between the northern and southern zones, as about 45 km of survey still has to be completed in the extended exploration programme.

As a result of the promising EM survey results, Uranex’s geology team started the drilling programme using a reverse-circulation drilling rig to primarily confirm whether the conductive zones are mineralised and the depth of mineralisation.

Guideline The drill chips from the drill programme will provide the geologists with a visual indication of the grade of the graphite, which the team will use as a guideline for further drilling.

Subsequent to the drilling programme, diamond drilling of the most prospective areas will be undertaken to provide samples for analysis and further metallurgical testwork, says Chittenden.

Basic exploration on the Nachu tenement, which is situated west of the coastal city of Lindi and about 200 km from the port city of Mtwara, in south-east Tanzania, started in February when Uranex geologists visited the site and uncovered further graphite outcrops, in addition to the outcrop uncovered in December 2012.

This initial exploration programme entailed surface sampling, surface mapping and sample analysis and was followed by a programme of trenching in areas of graphitic mineralisation in outcrops.

During the trenching, which started in June, five trenches were completed for a total length of 3.674 m and 2.049 m of this trenching exposed graphitic mineralisation, notes Chittenden.

Geology
Regionally, Nachu is situated within the Usagaran (Mozambique belt) Proterozoic system, which principally comprises high-grade, amphibolite-grade metamorphic rocks of sedimentary and igneous origin, ranging from schists to gneisses, including marbles, amphibolites, graphitic schist, mica and kyanite schist, acid gneisses, hornblende, biotite and garnet gneisses, quartzite and granulites.

These metamorphic rocks are overlain by Cretaceous sediments in the east and Karoo sediments in the south-west.

The structural trends of the Usagaran system are mainly north–south and the rocks in this system are well known for hosting gold, nickel, copper and gemstones such tourmaline, red garnet, tanzanite and high-grade coarse graphite flakes.

High-grade graphitic gneisses in the Chiliogali Hills, 10 km south-east of Australian miner Syrah Resources’ graphite and vanadium Nachingwea exploration project and about 40 km south of the Nachu tenement, have been reported as containing zones or bands with more 20% graphite.

Several other graphite-bearing gneisses are reported within or near the Nachingwea granulite terrain.

The area’s local geology is characterised by banded gneisses, generally quartz feldspar with darker biotite bands and Uranex has noted intrusive rocks and quartz vein intrusions.

The area is underlain by mica schists, quartz-ites, quartz feldspar gneisses, granitic gneisses, amphibolites, garnetiferous amphibolitic gneisses and micaceous graphitic schists.

In addition, some pegmatites and undiffer-entiated metamorphic sediments and gneisses were noted. Large parts of the area are covered by fairly deep red soils, with very little outcrop seen.

Uranex has gained much insight about working in Africa through its other African projects, which includes its Manyoni uranium project, in central Tanzania; its Mkuju uranium project, in southern Tanzania; and the Songea coal project, in the southern part of the Ruhuhu basin, in south-west Tanzania.

The company’s portfolio also includes a coal discovery at its Rutumba North tenement, near the Tanzanian port of Mtwara, and the Mkalama project area, in the north of Tanzania, which has the potential for a nickel/iron deposit in ultramafic rocks.

Through these projects, Uranex has learnt the importance of openly and freely communi-cating with the local communities living in close proximity to the exploration areas. “The communication has resulted in the com- munities’ understanding of what the explora-tion company hopes to achieve and has helped Uranex understand the needs and expectations of the community surrounding the project, says Chittenden.

Uranex’s short-term goal is to obtain promising target areas to eventually obtain an inferred or indicated resource estimate.

The company hopes to obtain the resource estimate next year and plans to also undertake a scoping study and start an environmental- impact assessment, while continuing to foster social communication.

Within the next three years, Uranex aims to establish a graphite-processing plant to generate cash flow. The company is looking at graphite produc-tion levels of 30 000 t/y to 40 000 t/y.