Mining Mirror October 2018 | Page 15

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 [13]