Exploration programmes are currently underway in five countries: Senegal, Mali, Côte d’Ivoire, Burkina Faso and the Democratic Republic of Congo where we have a combined groundholding of 13 583km2, hosting 276 targets. Of these, 130 are satellite targets to existing operations while 146 targets are potential stand-alone operations. The exploration work is supported by a team of 70 geoscientists.
ACHIEVED IN 2010
- Completed Gounkoto prefeasibility and feasibility studies and confirmed upside
- Loulo 3 developed into a significant satellite deposit
- Additional resources delineated at Loulo 1 and PQ10; upside from additional targets
- Exploration drilling extended purple patch in Yalea underground
- Updated Massawa geological model; started evaluation of satellite targets
- Commenced evaluation of Tongon satellite targets
- Completed geological model of Kibali KCD deposit; confirmed mineralisation between Sessenge and KCD
- Completed airborne electromagnetic survey over Kibali and prioritised targets
TARGET FOR 2011
- Complete Massawa feasibility study and evaluate satellite targets
- Complete underground conceptual study at Gounkoto; delineate satellite deposits adjacent to Gounkoto and Loulo
- Evaluate satellite deposits at Tongon and advance stand-alone targets within permit portfolio
- Test extensions to KCD orebody at Kibali and evaluate satellite deposits
- Develop at least one new exploration footprint
In 2010 exploration delivered on two key objectives:
- Completion of a positive feasibility study at Gounkoto
- Delivery of additional open pittable mineral resources to the Loulo plant.
At Gounkoto, a positive feasibility was completed on the back of mineral resources totalling 5.53 million ounces at 5g/t. Work included drilling for resource definition, metallurgical testwork, piezometry, sterilisation of infrastructure and advanced grade control. All forms of drilling totalled 99 120 metres during 2010.
The host rocks to the Gounkoto mineralisation are a sequence of fine grained arkoses which have suffered an early silica carbonate alteration event. More than 95% of the sulphide is pyrite (with minor arsenopyrite and chalcopyrite) and additionally gold tellurides are present. Mineralisation is bounded by a hangingwall shear and footwall mylonite. In the hangingwall there is a prominent limestone unit which is used as a marker horizon.
The mineralisation at Gounkoto has now been intersected over a 1.9 kilometre strike length and down to a depth of 642 vertical metres. The geometry of the Gounkoto system varies along its length as well as down dip and variations in strike, dip and thickness are closely related to grade distribution. Structural intersections also played an essential role in focusing fluid flow and multiple plunging zones projected from surface have been confirmed by deeper drilling, highlighting the good potential for underground mineable resources. Additional upside has been identified in the deposit as detailed below:
Southern pit area: Near-surface drilling has identified an area of wide, high grade mineralisation in the southern part of the deposit: GKAGCRC119 - 61.00 metres at 8.09g/t from 35.00 metres and GKAGCRC120 - 78.00 metres at 4.74g/t from 28.00 metres. Drilling is ongoing and results suggest this is a dilation zone within the main structure which plunges to the north and has a strike potential of 125 metres to a vertical depth of nearly 90 metres.
Fe structure: A north-south orientated iron rich structure which locates to the west of the main zone is providing further upside following RC drilling. Drill hole GKAGCRC293 - 19.00 metres at 10.72g/t from 3.00 metres and GKAGCRC294 - 26.00 metres at 14.56g/t from 32.00 metres. The weighted average gold grade from drilling is 4.4g/t over a strike length of 275 metres, to vertical depths of 120 metres and a true thickness of 12 metres.
Jog zone: A broad zone of high grade mineralisation has been intersected at the base of the US$700 pit shell, over a strike length of 100 metres. GKDH281 - 100.00 metres at 8.37g/t from 197.20 metres, GKDH285 - 93.45 metres at 5.51g/t from 182.00 metres, GKDH286 - 47.05 metres at 6.20g/t from 122.95 metres and GKDH283 - 55.30 metres at 11.60g/t from 187.50 metres.
Hangingwall: Drilling on the hangingwall has confirmed continuity of gold mineralisation associated with Si-Alb-CO3 alteration within a brittle fault, striking approximately north-south; average gold grade from drilling is 2.2g/t over a 500 metre strike length. Mineralisation is open in all directions with both shallow and steep high grade plunges evident. The follow-up of these will be prioritised as part of a programme to advance the underground conceptual study in 2011.
The southern half of the Loulo mining permit is developing into a new, significantly mineralised district. At the P64 target, 300 metres northwest of Gounkoto, previous work including trenching, diamond core and RC drilling, identified a 145 metre long strongly mineralised zone with the following intercepts: P64C13 - 26 metres at 6.29g/t, P64C4 - 34.45 metres at 8.85g/t, P64C5 - 21 metres at 4.87g/t, P64C6 - 24 metres at 2.81g/t, P64C7 - 25 metres at 2.40g/t, P64RC05 - 71 metres at 1.67g/t, and P64RC06 - 81 metres at 1.75g/t. Mineralisation is hosted in a tourmalinised greywacke with weak chlorite alteration.
Two kilometres southeast of Gounkoto is Faraba where an inferred resource of 567 000 ounces at 2.60g/t has been previously delineated. Mineralisation at Faraba locates where the north-south striking shear system intersects favourable coarse grained lithological layers. The resulting mineralisation occurs as sub-horizontal to gently plunging shoots with blade-like morphology.
In 2011, drill programmes will further test P64 and Faraba as well as Toronto and additional targets highlighted by an update generative study.
The Loulo 3 target has developed into a significant satellite deposit and a 1.7 kilometre long open pit. During 2010 a total of 1.93 million tonnes of ore were mined at a grade of 3.05g/t for 189 491 ounces. Geologically the deposit trends northeast and is bound both in the hangingwall and footwall by fine grained semi-pelitic units termed SQR (after the French term schistose quartz rosé meaning argillaceous pink quartzite). Mineralisation is hosted within a coarse grained greywacke which has been variably altered by silica and tourmaline. Intersecting north-south to north-northwest orientated structures, which are shallow dipping to the east, control high grade plunging shoots.
A programme of nine diamond holes for 2 380 metres is ongoing to test Loulo 3 at 160 to 180 metres vertical depth, testing beneath the base of the US$1 000 pit shell, the extent of which is limited by data constraints. To date, four diamond holes totalling 1 102 metres have been drilled along the entire strike length of the deposit at approximately 400 metres spacing. The holes confirmed the geological model and returned very encouraging mineralisation: l3DH33 - 4.7 metres at 2.50g/t from 235.1 metres, l3DH35 - 6.0 metres at 4.59g/t from 224 metres, l3DH36 - 10.4 metres at 10.22g/t from 221.15 metres and l3DH39 - 9.5 metres at 7.59g/t from 183 metres.
The Yalea structure is highly mineralised, hosting the deposits of Yalea and Loulo 3, as well as a number of surface targets.
At Loulo 1, 22 RC holes totalling 1 623 metres were drilled over a 630 metre strike length to a vertical depth of 50 metres. Mineralisation (5 to 15 metre thickness) follows the strike and dip of the lithological layering, trending northnortheast- northeast and dipping east at between 50 and 60 degrees. Sulphides are present predominantly as disseminated pyrite within the tourmalinised greywacke and quartz tourmaline. Results from the RC drilling include: L1RC18 - 5 metres at 4.43g/t from 7 metres, L1RC21 - 8 metres at 5.21g/t from 12 metres, L1RC22 - 8 metres at 4.71g/t from 62 metres and L1RC30 - 11 metres at 4.54g/t from 22 metres. Global mineral resource estimates amount to 23 858 ounces at 2.65g/t.
The priority in 2011 for exploration is the five kilometre segment from Loulo 3 to Loulo 1, which is a zone of continual gold anomalism and mineralisation including the surface targets of Loulo 2 and the Loulo 2-3 Gap. An initial programme of deeper diamond drilling will be completed on 500 metre drill centres to vertical depths of 200 metres. Surface RC drilling will also continue to define satellite open pits.
YALEA UNDERGROUND EXPLORATION
Exploration drilling defined additional high grade mineralisation on the margins of the 'purple patch': YUDH109 - 25.60 metres at 10.65g/t and YUDH112 - 21.35 metres at 10.88g/t.
This resulted in a reserve increase of 0.78 million tonnes at 8.68g/t for 216 419 ounces. In 2011, as underground development advances, exploration drilling will continue to target extensions to high grade mineralisation as geological models are updated and refined.
PQ10: On the Gara structure, attention focused on the PQ10 target. Forty-six holes for 3 504 metres were drilled over a strike length of 600 metres testing the western mineralised structure. The geology consists of finely laminated sediments units which bound mineralised pink quartzite (QR) units. The SQR units are weakly foliated, striking 185 to 195 degrees and dipping 50 to 70 degrees west. Brittle-ductile shears are present in the QR units. Subsequently a small resource was mined: 60 806 tonnes at 4.11g/t (8 035 ounces). The eastern structure is narrow with a true width of 7 metres and average grade of 1.8g/t. Additional upside has been identified at PQ10 south 7 RC holes defined mineralisation along a steep east-dipping shear which cross-cuts the western limb of an open antiform. The weighted average gold grade is 2.2g/t over a true width of 6 metres.
OTHER LOULO TARGETS
During the year the potential of all the Loulo satellites was evaluated. This involved a data review and updated geological estimates, fieldwork and in the case of Bolibanta, drilling. Additionally, pit shells and resources have been calculated for the most promising of the satellites around Loulo and these will be further evaluated by exploration in 2011. The combined potential from all the Loulo satellites is approximately 270 000 ounces at 2.8 g/t.
On the Bambadji permit in Senegal, adjacent to both Loulo and Gounkoto, work progressed from reconnaissance exploration, through RAB and RC drilling and culminated in diamond drilling on specific targets which have analogies to Gara, Yalea and Gounkoto styles of mineralisation. By the year end, six holes had been drilled on two targets: Kolya and Waraba. The programme has intersected strongly deformed and altered rocks containing pyrite mineralisation at both targets. However, intersections from the Kolya target have so far confirmed a narrow mineralised quartz tourmaline (QT) system beneath strong gold mineralisation at surface. At Waraba, the holes intersected a large alteration system on the margin of an albitite intrusive. The remaining priority targets for this initial phase of drilling are Kach, Gefa, Baqata and Mananord.
The Massawa gold project is located within the Kounemba permit in Eastern Senegal which geologically lies within the 150 kilometre long Mako greenstone belt. The Mako greenstone belt, comprises mafic–ultramafic and felsic volcanic rocks intruded by granitoids. A regional crustal scale shear zone, the Main Transcurrent Shear Zone (MTZ) with northeast-southwest trend exploits the lithological contact between the Mako and the Dialé–Daléma Supergroups and is the host structure to mineralisation at Massawa.
A total strike length of 8.5 kilometres has been drilled, but only a 4 kilometre portion of this has been evaluated for the present mineral resource modelling and has been drill tested to a 50 metre by 50 metre spacing to a maximum vertical depth of 640 metres. In 2010, 50 resource diamond holes for 19 835 metres, 47 dedicated metallurgical diamond holes for 8 620 metres and 15 geotechnical diamond holes for 3 697 metres were drilled. Additionally 105 shallow RC holes for 7 204 metres were drilled.
The 4 kilometre strike at Massawa currently being evaluated contains two zones of mineralisation: northern and central. However, they are part of the same northeast trending mineralised structure, which has been offset by north-south belt discordant structures. Geological logging of core and interpretation confirms that the mineralised system occurs at a volcanic/sedimentary contact, where a prominent and continuous lapilli tuff sequence acts as a marker horizon. The average bedding strikes 020 and dips 60 to 76 degrees to the west. Graded-bedding is common and suggests the sequence is overturned. The host sequences have been intruded by felsic dykes, gabbros and granitic bodies, particularly in the central area. Mineralisation is hosted in a variety of rocks including: greywackes, volcaniclastics and both mafic (gabbros) and felsic intrusives. The mineralised system is however structurally controlled and deformation is essentially brittle-ductile. The alteration assemblage is composed of sericite, silica, carbonate, pyrite and arsenopyrite. Gold mineralisation formed in two phases: an early phase composed of fine disseminated pyrite and arsenopyrite and a later stage which is a shallow level gold system where quartz-stibnite and a large range of antimony- bearing minerals host coarse native gold.
During 2010, as well as the resource drilling, deep drilling has confirmed continuity of the lithological sequence, structure, alteration and gold mineralisation to a maximum depth of 640 metres below the surface, results include: 17.15 metres at 3.49g/t, including 4 metres at 6g/t in the central zone and 29.20 metres at 3.75g/t, including 12.60 metres at 5.98g/t in the northern zone. Step out drilling, testing the mineralisation along strike confirmed continuity of high grades, 200 metres, north of lion extension with 1.60 metres at 15.49g/t. In Massawa South, drilling returned broad low grade intersections (MWDDH464 - 22.85 metres at 0.59g/t) but revealed a similar geological and alteration package as the central zone.
Exploration on Massawa has been slowed down as we have advanced Gounkoto and Kibali providing the time to fully evaluate the metallurgy and development strategies. The aim is to progress the project to final feasibility in 2011.
As well as Massawa, there are a number of targets which have had varying degrees of follow-up work completed on them from trenching through to RAB and diamond drilling, and all highlight the possibility of providing additional ounces within a 15 kilometre radius of Massawa. Our key objective is the discovery of at least 2 million ounces of non-refractory ore to supplement the ore from Massawa. These targets are summarised below:
Sofia: 56 RC holes for 5 571 metres were drilled at 100 metre spacing along a strike length of 4 kilometres. The mineralisation is continuous along strike, the weighted average gold grade is 1.45g/t over a true thickness of 18 metres and includes intersections of: SFRC001 - 31 metres at 2.5g/t, SFRC007 - 29 metres at 3.16g/t, SFRC010 - 16 metres at 4.6g/t and SFRC021 - 15 metres at 4.08g/t. Geologically the target is underlain by a sequence of andesite and volcaniclastic rocks intruded by quartz feldspar porphyries and gabbros. Mineralisation is associated with disseminated pyrite accompanied with silica-K feldspar-carbonate alteration.
Delya: Is defined by a 6 kilometre by 100 metre plus 20ppb gold in soil anomaly. A programme of 2 761 metres of RC drilling, on 100 metre spaced centres, was completed over a strike length of 1 kilometre. Intersections from this programme include DlRC005 - 5 metres at 5.59g/t, DlRC010 - 4 metres at 7.22g/t, DlRC013 - 11 metres at 9.50g/t and DlRC014 - 9 metres at 14.95g/t from a structure which averages 5 metres width and a weighted average gold grade of 4.5g/t. Mineralisation is hosted within a package of schists, strongly sheared and altered by silica- sericite-iron and disseminated pyrite and arsenopyrite.
Bakan Corridor: The Bakan Corridor groups together a number of anomalous gold in soil targets (Bakan, Tizia, Khosa, Tiwana and Tina) along a 10 kilometre segment of the northeast trending Kossanto structural corridor which is sub-parallel to the MTZ. The geology comprises a sequence of ultramafic units, felsic and intermediate volcanics (andesites, dacites and rhyodacites), cherts and igneous rocks ranging from diorite to monzonite. By year end a total of 5 RC holes for 531 metres, out of a programme of 11 RC holes, had been drilled at the Bakan target. The first hole returned 29 metres at 1.9g/t, including 10 metres at 4.5g/t. A further 13 RC holes (1 175 metres) are designed to test mineralised felsic intrusives at Tina along a 1.25 kilometre strike. Additional holes are being planned at Khosa where intensively northeast sheared felsic intrusives and silicified bodies (cherts) were mapped.
Bambaraya: At Bambaraya, 5 RC holes for 588 metres were completed as infill drilling to previous work over a 1 kilometre strike. Results returned narrow, low grade intersections: BBRC03 - 3 metres at 2.12g/t, BBRC04 - 3 metres at 1.57g/t and BBRC08 - 18 metres at 1.8g/t and 9 metres at 1.26g/t. Mineralisation is hosted within northeast trending pillow basalts and is associated with silica-sericite-tourmaline-iron carbonate-pyrite alteration. no further work is planned on this target for the time being.
As well as RC drilling on known satellite targets the team commenced the evaluation of the next level of targets for drilling in 2011: Kawsara, Manja, Galama, Sira, Kaldou, Makana, KB and KA. Additionally, work also started on generating new targets at Nouma, Makana East and Sofia South.
With the commissioning of the new mine at Tongon and the first commercial gold production, exploration has now shifted focus to the evaluation of satellite targets.
An 11 647 line kilometre airborne electromagnetic geophysical survey was flown over the Senoufo Greenstone Belt in northern Côte d'Ivoire, covering the Nielle permit and portions of the Diaouala and Fapoha permits. The survey provided the foundation to an improved geological and structural interpretation of the belt; the resultant prospectivity analysis identified 79 new targets, of which 18 ranked high to medium and locate within a 15 kilometre radius of the Tongon plant.
The prioritisation of targets resulted in exploration programmes being performed at: Seydou, Jubula, Tongon West, Sekala, Belokolo and Nafoun. encouraging results were returned from:
- SEYDOU: trenching and drilling - 12.3 metres at 2.3g/t, 19 metres at 5.32g/t and 21 metres at 3.76g/t.
- SEKALA: RAB drilling returned multiple mineralised zones including 23 metres at 2.18g/t and 15 metres at 1.11g/t.
- JUBULA: trenching - 61 metres at 1.31g/t, 16.5 metres at 3.52g/t and 12 metres at 1.7g/t.
- TONGON WEST: RC drilling - 10 metres at 4.47g/t and 14 metres at 3.08g/t.
In 2011 RAB, RC and diamond drilling are all planned to progress these targets as well as to advance stand-alone opportunities within our permit portfolio.
DEMOCRATIC REBUBLIC OF CONGO
Exploration completed a detailed analysis of the KCD deposit resulting in a new geological model which supported a substantial increase in mineral reserves to 10 million ounces at 4.21g/t within global mineral resources of 18.4 million ounces at 3.1g/t. Drilling connected the Sessenge deposit to KCD and confirmed over 2 kilometres of continuous mineralisation: DDD472 - 14.80 metres at 4.18g/t, DDD475 - 25.95 metres at 4.28g/t, DDD484 - 29.70 metres at 3.92g/t and DDD485 - 39.60 metres 6.65g/t.
There is additional upside within the current Sessenge- KCD deposit both near surface and at depth. The deposit comprises a series of stacked lodes, which have been labelled by their elevation: 3 000 series, 5 000 series and 9 000 series plunging moderately to the northeast. The outlines of these lodes, rather than being limited by the extent of mineralisation, are in fact limited by drilling.
There are three key upside opportunities:
- Expand the open pit to the northeast by testing extensions to the 3 000 lode within the drained Lake Durba
- Sessenge-KCD gap requires infill drilling for resource conversion
- Test the continuity and extensions to the underground lodes down plunge (9 000 and 5 000 series).
A 12 277 line kilometre SPECTREM airborne electromagnetic (EM) survey was flown over the Kibali concession during the second quarter of 2010.
The key highlights of this survey were:
- Igneous intrusions are more widespread than previously mapped.
- A corridor of strong northeast trending structural grain is coincident with the main areas of mineralisation.
- Strong EM conductor coincident with the KCD area, interpreted to be the response from carbonaceous shales +/- the Durba hill ironstone.
- Strong east-west conductors along the West Nile Gneiss contact possibly related to carbonaceous shale unit that was exploited by early thrusting and subsequently crosscut by a later northeast structural grain.
- Conductive and magnetic trend running along or parallel to the main mineralised trend.
Three-dimensional modelling of the data has identified a number of northeast plunging shoots of highly conductive material that are interpreted to represent mainly graphitic carbonaceous shale.
Several of these shoots are associated with areas of known mineralisation, for example at KCD and Pakaka. The shoots are thought to represent intersections of important mineralising northeast trending S2 tructures and northwest trending S1 thrusts that have exploited carbonaceous shale horizons.
Although the EM anomalies do not map actual gold mineralisation it is thought the conductive shoots highlight structurally important traps especially as they daylight coincident with gold in soil anomalies.
In 2011, exploration programmes will target the upside opportunities within the Sessenge-KCD deposit. In evaluating satellite targets, priority will be given to Gorumbwa and Agbarabo, which were high grade underground mines during the Belgium era, as well as testing conceptual ideas generated from the geophysical survey.
Generative and new business
As well as advancing the key strategic areas, generative work and research continues to identify new exploration opportunities within Archaean and Proterozoic age rocks across the African continent.