Authors: Garcia, O; Webster, S; Bruning, T; Brown, K; Schubert, C

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Garcia, O, Webster, S, Bruning, T, Brown, K & Schubert, C 2022, 'Northparkes E22 deposit: a strategic re-evaluation of mine design and material handling system', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 861-876,

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The Northparkes E22 deposit is a localised mineralisation area, separate to and approximately 2 km north of the E26 and E48 underground mines. The E22 orebody commenced using open pit mining methods in 2000 and over the two mining campaigns reached a depth of 230 m. Mining studies over the last 10 years have investigated extracting the remaining ore through numerous methods including further pit cutbacks, sublevel caving and block caving. The basis for the reserves has been a block cave where twin declines are mined from E48, the closest existing underground infrastructure, to form the ventilation and conveyor drives. This 3.7 km of development required to access the E22 orebody has positioned E22 as an investment with five years’ upfront capital expenditure before production commences. In 2021, a pre-feasibility study evaluated in detail underground sublevel caving and block caving methods along with sub options for production rate, net smelter return value, material handling, mine access and ventilation infrastructure. From the viable sub options 13, cases were pursued for financial analysis with four cases put forward for detail design: The evaluation of this work indicated that, for the sublevel cave options, although bringing forward highgrade material, the operating and capital costs were greater than the block caving cases, to recover 40% less tonnes. The two block cave options differ in their quantity and discharge point of underground ore they deliver to the surface. Options incorporated into the existing material handling hoist system are bottlenecked to the hoist capacity. This means that total Northparkes mill production will rely on surface stockpiles and open pits to supply the additional material not able to be hoisted. Cases that convey directly to surface provide an opportunity to convey up to 8 Mtpa of E22 underground ore, in addition to the hoist capacity. This scenario provides a future opportunity to connect the surface conveyor to the top of bins/base of hoist location via a 1.1 km conveyor. This connection rethinks the Northparkes material handling strategy and allows future mines associated with GRP, E26, and Michael J House (MJH) orebodies to also be conveyed or hoisted to surface.

Keywords: hoist, conveyor, material handling study

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