Outside of the Imbo, Makapela and Barrick joint venture projects, Loncor also has two other projects: Yindi in the southwest of the Ngayu belt and North Kivu to the south.
Loncor holds 100% of the Yindi project, which is a 2.5-kilometre radius, circular parcel of land within the southern part of the Archean Ngayu Greenstone Belt surrounding and including the Yindi project It does not form part of the joint venture with Barrick although Barrick has certain pre-emptive rights over the Yindi area.
Figure 1: Location of Yindi Project Area in the Ngayu Belt
Yindi is the site of an old Belgian mining operation which ceased production before independence, and which produced approximately 45,000 ounces and 21,000 ounces of gold from primary and secondary sources respectively. The Belgians primarily exploited discrete high grade, quartz veins by means of adits and narrow open-pits, and limited open-pitting was also carried out on mineralized banded ironstones (BIF). Operations ceased in the mid-1950s.
Exploration by Loncor at Yindi commenced in March 2010 with the establishment of a 2 x 6 kilometre soil sampling grid, coincident with a well-defined magnetic anomaly, and covering the area of old mining activity. Soil sampling lines were originally at a spacing of 160 metres, with infill to 80 metres in anomalous areas. All soil sampling lines were geologically mapped. Channel sampling of accessible old adits and open-pits was undertaken, and several old trenches were re-excavated and channel sampled. Mechanical auger drilling was carried out to test for saprolite mineralization below soil anomalies.
Diamond drilling commenced in September 2010 and 18 holes (3,274 metres) were completed. The drilling focussed on an area of BIF-hosted gold mineralization which was identified from soil and channel sampling, and which had been mined to a limited extent during colonial times. Holes ranged from 134 metres to 290 metres in depth (i.e. a maximum of 262 metres vertically below surface). The drilled lithologies consisted mainly of fine-grained schists, which petrographic studies show were originally pelitic sediments and tuffs, now metamorphosed to lower greenschist facies. Several units of BIF up to about 15 metres in thickness are interlayered with the schists. The sequence has a consistent NW-SE strike and southwesterly dip of about 75°.
Gold mineralization occurs both within the BIF and within the schist near the BIF contacts, and is associated with:
- pyritisation of magnetite bands in the BIF;
- massive pyritisation of the BIF;
- disseminated pyrite in the schist; and
- quartz veining within both the schists and BIF
Significant borehole intersections included 21.30 metres grading 3.31 g/t Au, 22.27 metres @2.26 g/t Au, 24.04 metres @ 1.45 g/t Au and 8.10 metres grading 2.53 g/t Au. The main mineralized zone at Yindi averaged a true width of 11.0 metres at an average grade of 2.20 g/t Au over a strike length of 350 metres.
Induced polarisation (I.P.) geophysical surveys were carried out in March 2013 and comprised a 1 x 1 kilometre gradient array survey, followed by two lines of pole-dipole. The objectives of this work were: (a) to assess the I.P. response of mineralized BIF as an orientation for surveys elsewhere in the concession, (b) to assist in determining the geometry and plunge of the BIF-hosted mineralization at Yindi, and (c) to detect possible additional mineralized zones. This geophysical survey indicated a shallow plunge to the mineralization and identified a number of drill targets. Follow up drilling is warranted to test these I.P. targets and if successful, to determine a mineral resource at Yindi.