"The gold dredger has mined around the perimeter creating an illusion that most reserves have been mined. This is not yet so, as the interior of the Blocks remain intact, concealed by the perimeter overburden mound, hidden inside the half-ring of active and abandoned dredge ponds." | ABSTRACT The South Dredge is a second-hand dredger, formerly active in the Bugant Goldfield in northern Mongolia for many years until the dredgeable reserves became almost exhausted.
The dredger was sold to Shijiir Alt Ltd, dismantled, trucked to Zaamar and reassembled. The dredger is the most southern (upstream) dredger in the Zaamar Goldfield, and is mining the huge Tuul Placer, and some of the underlying red Ulaan Placer. The South Dredge has been studied in action at its new location.
The South Dredge is assisted by 2 large Ukrainian Soviet Esh Draglines that strip the overburden to create a chain of dredge ponds. In doing so, the draglines have created a huge wall of steep overburden mounds on the perimeter, especially on the west where the overburden thickens as the Tuul Placer is partly concealed by terraces. The larger of the draglines is a Soviet Esh 10/70 Dragline with a 6m3 bucket and 70-metre reach. The smaller dragline is a Soviet Esh 6/45 Dragline with a 6m3 bucket and a 45-metre reach.
The eastern perimeter is the Tuul River, and the Draglines were compelled to dump an inner perimeter mound on intact virgin reserves. To mine them will require expensive flattening of the mound or to accept these reserves as being sterilised and lost. Such dilemmas are inevitable with draglines but would be avoidable if a Cutter-Suction Dredge were to be used.
The South Dredge operates on the west bank of the Tuul River, a short distance downstream from the main Road Bridge. The dredger is mining in Blocks C1-19 and C1-20, but inspection shows considerable reserves of gold remain in these blocks. The dredger has mined around the eastern, northern and western perimeter creating an illusion that most reserves have been mined. This is not so, as fieldwork showed that the interior of the blocks remain intact, concealed by the perimeter overburden mound, hidden inside the half-ring of active and abandoned dredge ponds.
The half-moon of overburden mounds now towers as a steep western wall above the dredge pond that are visible from space (click to see Landsat image). The dredge pond itself is dominated by the curved ridged mound of oversize discharged by conveyor at the rear of the dredge, concealing the tailings below.
The photos record the dredge ponds making a 90-degree bend at the north-west corner of the mined area, and a 180-degree doubling-back has recently been undertaken, the dredge-path cleared first by the 2 Draglines. The dredger is therefore now mining the interior of the un-mined central area. DOWNLOAD ABSTRACT
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