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Core drilling in Tanzania

Lake Victoria Mining completed a drilling programme in May 2012 at its Uyowa prospecting licence in northwestern Tanzania. The core-drilling programme focused from the central to the western part of the east-west trending mineralised zone, and covered a length of about 300m within the 1,700m-long artisanal gold zone. Vertical depth is about 100m below surface.

Drilling successfully intersected the mineralised lenses as identified from the RC drill programme in August 2011. Diamond drilling further defined the geometry of the mineralised zones as consiting of two gold lenses, approximately 25m apart and dipping to the north at 65°.

The dip of the two lenses steepens to 75° further along strike to the east. The southern lens is the more dominant of the two gold structures as it has both a higher gold grade and a continuous strike length. Gold mineralisation is hosted with pyrite within narrow ductile shear zones that have a maximum down hole intersected width of up to 7.8m.

Under examination

Analytical work is carried out at the independent SGS Laboratories in Mwanza, Tanzania. The drill samples have been subjected to full sample preparation followed by a 50g fire assay with an AA finish. Blanks (5%), commercial standards (5%) and duplicates (5%) have been used in each sample batch of 20 samples to monitor laboratory performance during the analysis. Samples submitted either represent 1m intervals or have been sampled according to lithology and/or structural zones that would include the presence of visible gold or gold bearing sulphides as logged in the boreholes.

To the east

The Kiabakari East project in northeastern Tanzania is about 4km southeast of the past producing Kiabakari gold mine. The four-hole drill programme, completed in June 2012, totalled 648.72m and was the first drilling by Lake Victoria at Kiabakari East. Final drill hole locations were determined by detailed geologic mapping, geophysical surveying and trench sampling.
The holes intersected wide zones of anomalous gold mineralisation including 37.5m of 1.03g/t gold, 43.35m of 0.58g/t gold, including higher-grade intersections of 1.75 g/t gold over 6.13m and 2.05 g/t gold over 3.00m.
Drilling was focused at BIF Hill, where previous trenching returned significant gold grades within banded iron formation rocks. The drill holes were located on the south side of BIF hill and were spaced 40m apart on N-S drill fences. The holes, drilled due north at angles of -50° and -55° below the horizontal, were designed to test the grade and to define the geometry of the gold mineralisation.

Geologic setting

Each borehole was drilled across an 80m-wide BIF package of rocks consisting of cyclic siltstone and banded chert sequences until the footwall pebble conglomerate was reached on the northern side of the hill. The BIF unit dips steeply to the south, and although occasional intraformational sedimentary slump breccias are present, the unit is complexly folded, which tends to increase the grade of the gold mineralisation. A north-northeast trending fault is present and appears to have displaced the eastern part of the mineralised zone some 40m to the north and to also have down-dropped the BIF unit to the east.

Massive sulphides, consisting of pyrrhotite and magnetite-rich bands occur throughout the BIF unit. Crackle brecciation and fracturing is more common in the brittle chert beds, which are often infilled with later pyrrhotite and/or pyrite mineralisation. Gold is associated with the sulphide-filled fractures as well as within zones of massive pyrite and, to a lesser extent, massive pyrrhotite mineralisation.

From the limited drilling undertaken across 80m of east-west strike length, the gold mineralisation, having been offset by the north-northeast fault, plunges steeply to the east. Anomalous gold values of more than 250ppb gold were encountered over substantial widths in each of the boreholes. Higher grades were intersected in the deeper eastern-most hole (KED004). It is important that mineralisation remains open down dip and along strike both to the west and down plunge to the east.

Future goals

A second target within the Kiabakari East licence is the Kyarano prospect, which is located 1.5km east of BIF Hill and has yet to be drill tested. Gold is associated with a north-northeast trending pyritic quartz felsite porphyry. This quartz porphyry has a known strike length of about 500m and is an active artisanal mine site. Shaft samples collected by Lake Victoria returned gold values up to 19.8g/t gold. Future work will attempt to locate drill targets to further test this prospect.

Gold shoots

The distribution of gold in Lens 2 suggests that there are three equally spaced gold “shoots” of approximately 80m wide plunging at 30 degrees to the west and which are open at depth. A left lateral fault on the western side of the main drilling target has offset the strike of the lenses by some 10m.

Some of the highest gold intercepts, which have been reported from drilling, occur in the westernmost shoot. The central and eastern ore shoots appear to have lower overall gold grades and narrower intercepts.

Additional drilling will be required to extend the down-dip resource potential of the western gold shoot. In the meantime, exploration will be aimed at discovering higher grade gold lenses along the 5.3 kilometre of strike to the west where landsat imagery and recent soil sampling indicates a possible extension of the gold bearing structural zone.

 
 
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