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Iron ore

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Iron ore

The Northern Territory contains small to large iron ore deposits that produced about 9 Mt of iron ore between 1967 and 1974. Current resources for the NT are estimated at 300 Mt of iron ore. Most of this occurs as low-grade oolitic sedimentary deposits (Hodgson Downs, Deposits B and C) in the Roper River district of the McArthur Basin. These haematite-rich oolitic beds are 0.5 to 4 m thick and Mesoproterozoic in age.

Small, higher grade hydrothermal-type deposits (eg Frances Creek) and skarn deposits (eg Mt Bundey) within the Pine Creek Orogen have been mined in the past. Mining of Au (±1Cu-Bi)-bearing ironstone at Tennant Creek over the past 60 years has produced tailings containing up to 70% magnetite at Warrego (11 Mt), Peko (4 Mt) and Nobles Nob (2.4 Mt). These tailings represent potential sources of low-cost iron ore, as they are located near the Alice Springs-Darwin railway line and existing infrastructure.

France Creek mine has been recently re-opened and the first shipment of high-grade (over 63% F3) iron ore to China took place in Spetember 2007.

Iron ore deposits of the Northern Territory

The following updated notes are derived from the abstract of Ferenczi PA, 2001. Iron ore, manganese and bauxite deposits of the Northern Territory. Northern Territory Geological Survey, Report 13. Contact the InfoCentre (telephone +61 8 8999 6443 or email) for copies of this report, available free-of-charge.

Iron ore occurrences in the Northern Territory have been classified into four types: oolitic sedimentary, hydrothermal, Fe-skarn and surficial. Mesoproterozoic iron ore deposits of the Roper River iron field (McArthur Basin) are examples of the first style. These oolitic ironstones form 0.5-4.0 m thick beds in the Sherwin Formation that are laterally continuous over tens of kilometres. Several hundred million tonnes of ironstone material is present in this region. Ore quality is generally low and typically about 40% Fe, 30% SiO2 and 0.1% P, although better quality material (>50% Fe, <30% SiO2 and 0.1% P) exists in the Hodgson Downs area. Shallow drilling is required over this area to determine subsurface phosphorus levels. Thin Ordovician oolitic ironstones are present in the Amadeus and Georgina Basins.

Distal hydrothermal iron deposits are massive, tabular to podiform, stratabound haematite/magnetite bodies formed by the enrichment of an iron-rich protolith. Hydrothermal fluids derived from magmatic or connate brines during orogenic activity have remobilised sedimentary iron in the host sequence into adjacent stratigraphic and structural trap sites. Iron-rich pods in the Frances Creek iron field (Pine Creek Orogen), Tennant Creek mineral field (Tennant Region) and Harverson Pass area (Arunta Region) are examples of this style of mineralisation.

Some 8 Mt of ore grading 59% Fe has been produced from southern deposits in the Frances Creek iron field, which contains series of discontinuous, stratabound, massive haematite lenses over a 40 km strike length. Thick ore intersections (up to 110 m @ 63% Fe) are present in synclinal structures. Small resources exist in the southern (1.4 Mt @ 64% Fe and 0.08% P) and northern (2.4 Mt @ 54% Fe and 0.12% P) areas. Detailed gravity surveys over selected areas in the southern part of the field could be used to detect 1-5 Mt lenses in gently plunging synclinal structures under shallow cover.

Mining of gold and copper over the past 60 years at Tennant Creek has produced tailings containing up to 70% magnetite at Warrego (10 Mt), Peko (4 Mt) and Nobles Nob (2 Mt). These tailings represent potential sources of low-cost iron ore, as they are located near the Alice Springs-Darwin railway line and existing infrastructure. Small tonnages of iron ore are present in the Rum Jungle area and may meet the requirements for other local mineral processing operations.

Small Fe-skarn deposits are present in the Pine Creek Orogen (Mount Bundey area) and Arunta Region. Some 840 000 t @ 63% Fe was mined from Mount Bundey between 1968-71 and a remaining resource of 190 000 t @ 62% Fe and 0.8% S exists below the pit floor. Surficial iron occurrences in the NT are not considered an attractive exploration target due to their typical low tonnage and grade.

 

Last Updated: 9 July 2010