Modern Mining June 2016

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June 2016MODERN MINING29
WEST AFRICA
ture
Celebrating the first gold
pour are John Dorward
(left), Roxgold’s President
and CEO, and Paul Criddle,
Chief Operating Officer
(photo: Roxgold).
capacity can be increased by 50 % at a cost
of approximately US$5 million. The flowsheet
incorporates primary crushing, grinding with
a single stage SAG mill, gravity concentration,
classification, leaching and adsorption, tail-
ings thickening, electrowinning and smelting.
The SAG mill has been upgraded to a 1,5 MW
motor (from 900 kW in the Feasibility Study)
to allow for added flexibility.
The underground mine is accessed by a dual
ramp system via a single portal at the bottom
of a 23 m deep boxcut. Ramps are designed at
a -14,3 % gradient with dimensions ranging
from 5,3 m (width) by 5,8 m (height) to 5,0 m
by 5,5 m depending on the planned air flows.
Longhole open stoping (including up hole
retreat in certain areas) is the main mining
method with a limited application of cut and
fill for the crown pillar mining. All methods
except up hole retreat will employ waste rock
as backfill. The mine layout is based on 17 m
sub-levels. Standard longhole stopes two sub-
levels in height (34 m) and 25 m in strike
length will be utilised to mine the narrow vein
orebody.
Ventilation requirements for the mine are
estimated at 212 m3/s for a production rate of
750 t/d. All of the intake will be through the
main access ramp. Exhaust will be through the
east and west return air raises, each sized at 3 m
diameter.
The underground mining contract was
awarded to AUMS (African Underground
Mining Services) – which has consider-
able African experience – in September 2014
although the company only mobilised to site
in mid-2015. It is envisaged that by December
2018, AUMS will have delivered 17 100 m of
jumbo development, 120 000 m of specialised,
narrow-vein, 64 mm longhole drilling and
460 000 tonnes of ore.
Yaramoko’s probable mineral reserve totals
1,1 Mt at a grade of 11,83 g/t for 759 000 ounces
of gold. The indicated resource (including
reserves) amounts to 1,6 Mt at 15,8 g/t at a
5 g/t cut-off (810 000 ounces) while inferred
resources total 840 000 tonnes at 10,26 g/t
(278 000 ounces).
There is considerable scope to increase the
resource base. The current mine plan is to a
depth of 430 m but high-grade results have
been encountered to a depth of 900 m and there
is also potential for lateral expansion of the
orebody. In addition, RoxGold has a number of
promising regional targets. A high-grade satel-
lite resource – QV1 on the Bagassi South permit
– was discovered in April last year, 1,8 km
south of the 55 Zone (where the underground
mine is located). In April this year Roxgold
declared a maiden inferred resource for QV1 of
563 000 tonnes at 12,14 g/t for 220 000 ounces
of gold at a cut-off grade of 5,0 g/t.
Photos courtesy of Roxgold