Deposit Types The original Hellyer massive sulfide deposit has been interpreted by most previous workers as a classic, seafloor, mound-style, VHMS deposit, developed in a similar manner to the classic Kuroko deposit (Gemmell and Large, 1992; Large, 1992; McArthur, 1996). Gemmell and Large (1992) described the hydrothermal alteration zonation pattern centred around the stringer zone and interpreted the metal zonation of the deposit to delineate the main feeder zones. McArthur (1996) examined the metal content, mineralogy, macroscopic and microscopic textures, and mineral trace element composition of the massive sulfide deposit in detail and supported the formation of the sulfide mound by deposition of sulfides at or near the seafloor with in-situ recrystallisation, intra-mound veining, upward deposition, and thermal retraction. This mound building and zone refining process, described by Eldridge et al. (1983), is responsible for the Cu-rich base of the deposit with an upward and outward increase in Zn and Pb content. Mineralisation is comprised predominantly of pyrite and sphalerite, with lesser galena and arsenopyrite. The deposit under review is a tailings dam, comprised of sediments pumped into a natural depression within a compacted earth-fill dam. The tailings sediments were sourced from the adjacent Hellyer Mine processing facility which processed polymetallic ore sourced mainly from the Hellyer underground mine plus some from the Fossey mine and the Que River mine. T ........

The Hellyer Gold Mines (HGM) mining method employs cutter suction dredges to excavate tailings material and transport it to shore via a floating pipeline. The dredged material is delivered to surge tanks via trommel screens to remove debris in the form of oversize rocks and timber and other vegetable matter. From these surge tanks the material is pumped via 300 mm diameter high-density polyethylene (HDPE) pipelines to the processing plant. The original “Seabird III” 300kW dredge with Warman10/8 main pump (10 inch / 250mm inlet, 8 inch / 200mm discharge) has nominal operating depth of up to 19 metres, with a nominal operating capacity of 180tph. The Seabird III has operated since October 2018 and is currently feeding 110 tonnes per hour to the processing plant. To maintain a feed rate of 100,000 tpm and more, given the potential of greater throughput in the processing plant following alterations to the flotation circuit, a second dredge has been commissioned in early 2022. This second unit should ensure steady feed rates with less interruptions for maintenance and unforeseen downtime events, the second dredge unit permits blending of feed material to the process plant. The dredge was designed for a excavation depth of 10.4m with a submerged 10/8 Warman pump fitted on the ladder and the revolving cutter head on the end of the ladder. This dredge is equipped with a removable ladder extension piece, allowing a maximum digging depth of 16m below water, though it is reported tha ........

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