Global projects and exploration
These new improved grades and recoveries in the
recent test work are likely to have a significantly
positive effect on economics of the project and will
be considered by feasibility study numbers that are
under way and scheduled for completion later in the
year,” says Biggins.
Mongolia
Cranes slash pre-sink time
The world’s fifth-largest mine, Oyu Tolgoi in
Mongolia, will use advanced techniques enabled
by pioneering crane design to fast-track the pre-
sink phase at Shaft 6.
The time needed will be dramatically reduced
by a Condra portal crane that combines a rapid
lift speed with optimised cross travel to waiting
dump trucks.
Pre-sinking is expected to be completed in less
than a quarter of the time considered the norm
— four months instead of the usual 18.
The Condra portal is radically different from
the level-luffing type of crane traditionally used
for pre‑sinking. Instead, a high-speed, high-lift
main hoist removes excavated spoil vertically,
by kibble, through an opening in the centre
of a drilling stage positioned by two separate
stage‑winders mounted on the same portal
frame.
Lift speed is an impressive one metre per
second — 15 times faster than the four metres
per minute found in standard mine workshop
applications.
South Af rica-based Condra researched
its advanced portal design during 2013 for
incorporation in a prototype machine used at a
new diamond mining shaft the following year.
In addition to an innovative frame design
and dramatically increased lift speed on the
main hoist, the portal crane also incorporated
improved drives, gearboxes, and safety devices,
better cabin access, and enhanced operation by
remote control.
Oyu Tolgoi Shaft 6 will have two of these
Condra portal machines.
During the pre-sink phase, they will stand
over the mouths of the main and auxiliary
rescue shafts and remain in place until the
shafts have been drilled, blasted, supported,
cleaned, and lined with concrete.
Oyu Tolgoi is a combined opencast
and underground mining project located
some 550km south of Mongolia’s capital,
Ulaanbataar, within the Gobi Desert. The
mine, still under development by Rio Tinto,
began producing copper and gold concentrate
in 2013. It is the largest mining project in
Mongolia’s history.
Condra began manufacture of the first of the
portals for Oyu Tolgoi in early July, when the
long-lead assemblies order was received. The
main order was received on 24 July.
Oyu Tolgoi’s pre-sink cranes will be bigger
and faster than the diamond mining machine
and will feature improved electronics.
Importantly, lifting speed of the 160kW
15-ton main hoist on the new portals will
double to 60 metres per minute.
The portal frame itself will comprise a 14m
high, 12m span extended by 3.2m cantilevers
on both sides to allow excavated spoil to be
moved to dump trucks using roads adjacent to
the shaft. Stairwells will replace the cat ladders
of the diamond mine portal.
Below-ground lift height will be 100m, and
the complete machine will weigh 88t.
Completion of both cranes, the design
of which makes provision for disassembly
and containerisation, is scheduled for early
November this year.
They will be shipped to Mongolia via China.
Ethiopia
Altus releases good copper results
Africa-focused exploration company
Altus Strategies has released positive
assay results for its Daro copper-gold
project in the Tigray province of
northern Ethiopia. The outcrop assay
results include 11.6% copper (Cu) and
4.4 grams per tonne of gold (g/t Au)
at the Teklil prospect.
According to Steven Poulton, CEO
at Altus, the exploration at Daro
continues yielding exciting results,
with high gold and copper assays
returning from a number of surface
sampling programmes, including
37g/t Au and 22.7% Cu.
The presence of gossans,
polymetallic mineralisation,
significant artisanal gold workings,
and favourable host geology
continues to indicate the potential
for a VMS discovery within Daro.
We are also excited to continue
developing the project further with
the discovery of the Keren prospect
containing a gold-bearing quartz
vein and stockwork system. Our
next phase of work will include
mapping and selective channel and
soil sampling programmes,” says
Poulton.
OCTOBER 2018 MINING MIRROR
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