PERTH (miningweekly.com) – An in-situ feasibility study at the Century zinc mine, in Queensland, has supported the development of in-situ operations alongside the current tailings operations.
ASX-listed New Century Resources on Wednesday reported that the study investigated the incorporation of Silver King and East Fault Block in-situ deposits into the existing mine plan, in addition to the current tailings reprocessing, to produce zinc concentrate and a new lead concentrate.
The study estimated that the in-situ development would require a capital investment of some A$66.7-million, allowing for average lead metal-in-concentrate production of some 33 000 t/y containing 972 000 oz/y of silver, and an average additional zinc metal-in-concentrate production of 22 000 t/y.
The lead concentrate product is expected to grade between 65% to 70% lead, and between 500 g/t and 600 g/t silver.
The current tailings operation at Century is targeting production of between 130 000 t and 145 000 t of zinc metal for the 2022 financial year, with C1 costs targeted at between $0.78/lb and $0.88/lb.
New Century noted that in-situ operations would reduce Century-wide C1 costs by some $0.21/lb payable zinc, through the benefit of additional lead, zinc and silver metal output spread throughout the project’s existing significant sunk capital base.
At current spot prices, the feasibility study estimated that the project would have a pre-tax net present value of A$234-million, an internal rate of return of 111%, and a pay-back period of only two years.
New Century told shareholders that a final investment decision on the in-situ operations would follow amendments to the existing environmental approvals and the completion of financing and joint venture assessments.
In the meantime, the company would complete board-approved front-end engineering design works, operational readiness and the procurement of long-lead items, while a final investment decision is targeted for the first quarter of 2022, and first in-situ production is expected in the first quarter of 2023.
Meanwhile, an upgraded mineral resource for the Silver King and East Fault block of 4.4-million tonnes, containing 209 000 t of lead, 234 000 t of zinc and 6.6-million ounces of silver, as well as a maiden ore reserve for Silver King and East Fault blocks of 2.5-million tonnes, containing 140 000 t of zinc, 5.4-million ounces of silver and 133 000 t of lead, have extended the mine life of the project to 2027.
There were also clear pathways to extend the mine life beyond 2030 and beyond with the conversion of mineral resources at Watson’s Lode, South Block and further Silver King extensions.