Zinc-lead-silver

• Lead Zinc Silver Factsheet and Map [PDF 1.1mb]
• Lead Zinc Silver Factsheet and Map [DOCX 603kb]

The Northern Territory contains numerous zinc-lead-silver mineral deposits that have produced over 2.0 Mt of zinc, 0.6 Mt of lead and 25 Moz of silver in the last 20 years. These deposits are found across the NT in a number of geological basins and orogenic regions. The Zn-Pb-Ag-rich provinces include; McArthur Basin, Pine Creek Orogen and Arunta Region. Deposits in the first two provinces account for 97% of past Zn-Pb-Ag production and 98% of identified Zn-Pb-Ag resources. Current resources for the NT are estimated at 16.4 Mt of zinc, 9.5 Mt of lead and 267 Moz of silver.

There is currently one mine in operation at the giant McArthur River deposit The McArthur River mine is situated about 70 km southwest of Borroloola, in the McArthur Basin. It is operated by McArthur River Mining Pty Ltd (MRM), a subsidiary of Xstrata PLC. It opened as an underground mine in 1995 and has since converted to open cut. The McArthur River mine has a total resource of 162.2 Mt at 10.7% Zn, 4.7% Pb and 48 g/t Ag. In 2011/12, MRM produced 449,000t of bulk concentrate. The deposit is regarded as a sedimentary exhalative (SEDEX) deposit, comprising fine-grained thinly bedded sulfide ore hosted in the HYC Pyritic Shale Member of the Barney Creek Formation. In August 2012, the Xstrata board gave final approval for the $360M Phase 3 Development Project at McArthur River, which will lead a doubling of production capacity to approximately 5.5 Mtpa and an increase in bulk zinc/lead concentrate volume to 800 000 tpa.

The Myrtle prospect, 20 km south of McArthur River, has a similar style of mineralisation, although with a coarser grain size than at McArthur River. The Inferred Resource at Myrtle is 43.6 Mt at 4.09% Zn, and 0.95% Pb, at a 3% Zn+Pb cutoff, with a higher-grade core of 15 Mt at 5.45% Zn and 1.0% Pb. The deposit and surrounding tenements are currently the subject of a Rox Resources Ltd-Teck Australia Ltd joint venture. The Birrindudu Basin also has potential for McArthur River-style shale-hosted deposits.

A number of base metal deposits occur in the Rum Jungle Mineral Field of the Pine Creek Orogen, including the polymetallic Browns deposit and the Woodcutters Pb-Zn-Ag deposit. Woodcutters is a vein-style deposit hosted by carbonaceous shales and was mined from 1984-99, producing 4.65 Mt ore averaging 12.28% Zn, 5.65% Pb and 87 g/t Ag. The largest single resource in the area is at the Browns sulfide deposit which contains 47.82 Mt at 0.35% Cu, 3.74% Pb, 0.09% Co and 0.07% Ni. An inferred resource at Browns East is given as 14.6 Mt at 1.06% Cu, 1.09% Pb, 0.14% Co, and 0.15% Ni.

The Arunta Region hosts a number of lead-zinc deposits including volcanic-hosted massive sulphide mineralisation (Utnalanama-style deposits) and skarns. Palazoic basins have high potential for Mississippi Valley style mineralisaion, with the largest known MVT deposit in the NT being the Sandy Creek Zn-Pb deposit in the Bonaparte Basin, which has a resource of 24.38 Mt @ 1.8% Zn, 0.45% Pb and 4.5 g/t Ag.