Centrex metals – PROJECTS

Centrex Metals Ltd has extensive tenement holdings over iron ore resources and exploration targets on Eyre Peninsula in the southern Gawler Craton adjacent to existing rail/port facilities.

Fig. 1 :: Centrex Metals Ltd Exploration Licenses, Eyre Peninsula (Click to see image)

The resources and targets are mainly within the early Proterozoic Middleback Subgroup sequence of banded iron formations (BIF) that host the historically important and currently operating iron ore mines of the Middleback Range (Onesteel Ltd). The extensive iron formations of Eyre Peninsula contain significant inferred resources of hematite and/or magnetite banded iron formation. Both historical and recent assays and metallurgical work have confirmed their potential and furthermore, the compositions of magnetic separations are favourable with high iron and low silica, alumina, phosphorous, alkalis and manganese.

Three categories of iron ore have been considered:

• massive hematite ore (as traditionally mined) with Fe > 56% and low impurities (eg. phosphorous and silica);
• hematite-rich BIF or jaspilite (interbanded hematite, quartz and/or iron silicates) with Fe >30%; and
• magnetite-rich BIF (interbanded magnetite, quartz, marble and/or iron silicates) with magnetite content as determined by magnetic Davis Tube Separation (DTS)
  >20% by weight.

The first category has traditionally been regarded as ‘direct shipping ore’ that could be exported without the need for beneficiation while the latter two categories would require beneficiation (concentration with or without pelletizing) to produce either iron concentrates or direct reduction (DR) grade iron ore pellets suitable for the export market.

Two small inferred hematite resources (total ca. 8 Mt @ 59-61% Fe) at Wilgerup on central Eyre Peninsula were identified by WMC Ltd during the 1990’s. The southern deposit is potentially suitable for direct shipping while the northern deposit could potentially be blended to form the basis of an initial small-scale iron ore mining operation 15-20km from rail and 115-130 km from port facilities. However, additional drilling and modelling are required to establish ore reserves and evaluate the economics of the project.

Inferred resources have been estimated for the major deposits based on limited drilling combined with geological mapping and interpretation of high-resolution aeromagnetic data (Table 1). Resources are judged to have reasonable prospects for eventual economic extraction. In the case of hematite BIF this may depend on other factors such as the eventual mining of underlying magnetite BIF. Exploration targets are those parts of the BIF for which potential quantity and grade are conceptual in nature and exploration has been insufficient to infer a mineral resource; continued exploration may not result in the determination of a resource.

Metallurgical tests for most of the above magnetite resources indicate that they are technically simple in regard to ease of upgrading the ores to high specification with low impurities such as phosphorous, silica, alumina, manganese and sulphides. They are relatively coarse grained, particularly on southern Eyre Peninsula, with good magnetite liberation at coarse grinds (100% passing 75 microns (μm)).

No beneficiation tests have been undertaken on hematite BIF except for Stony Hill where jaspilitic BIFs are suitable for beneficiation with recovery of most iron oxide after grinding to 150μm. Minus 100μm DTS concentrates averaged 47.9- 49.5% iron oxide @ 64.8-69.1% Fe.

Table 1: Summary of inferred BIF resources and exploration targets:

Prospect	Summary	Inferred Resources		Exploration Targets
		Hematite BIF	Magnetite BIF
Wilgerup (northern lens)	500-900 m long, 10-30m thick lens of massive martite hematite, micro-platy hematite & earthy hematite mineralisation with 0.1-0.55% P	6.1 Mt @ 59.4% Fe	nd	Up to 20 Mt hematite ore
Wilgerup (southern lens)	Potentially direct shipping massive hematite ore averaging <0.1% P	1.8 Mt @ 61% Fe	nd
Greenpatch	Extensive jaspilite BIF outcropping or under shallow cover 10 km from port. Strong aeromagnetic anomaly defines ~3.3km strike length.	12.9 Mt @ >33% Fe	75 Mt @ >25% DTS (69% Fe)	>100 Mt magnetite BIF >17.5 Mt hematite BIF
Bald Hill	Jaspilite BIF outcropping or under shallow cover extending over a strike length of 20km, 10 km from rail, 30-40 km from port. Several untested hematite targets in addition to magnetite. Resource estimate based on only 2 DHs.	nd	28.7 Mt @ >27% DTS (65-68% Fe)	Ca. 40 Mt magnetite BIF per strike km + local hematite BIF
Koppio	Jaspilite BIF outcropping or under shallow cover 12 km from rail, 35 km from port. Extends east to Brennand and Kapperna.	nd	39.6 Mt @ 29.7% DTS (65-69% Fe)	Up to 60 Mt magnetite BIF including Brennand
Carrow	Jaspilite BIF under shallow cover near Port Neill, 13 km from rail, 90 km from port – potential for new deepwater port facilities within 5-10 km	3.9 Mt @ >33% Fe	52.0 Mt @ 31.2% DTS (69.1% Fe)	>12 Mt hematite BIF
Iron Mount	Jaspilite BIF outcropping and in existing road-metal quarry and historic iron ore mine 50 km from port.	nd	6.7 Mt @ 37.2% DTS (63.5% Fe)	1-2 Mt hematite BIF
Bungalow	Intense aeromagnetic anomalies define ~18 km strike length of BIF under shallow to relatively thick cover, 40 km SSW of Iron Duke.	0.7 Mt @ 29.9% Fe	29.2 Mt @ 38% DTS (67.7% Fe)	>250 Mt magnetite BIF + significant hematite BIF
Stony Hill	BIF ore outcropping or under shallow cover; associated aeromagnetic anomaly extends over a strike length of 6km, 22km W of Iron Baron.	nd	nd	Significant magnetite and hematite BIF

BIF = banded iron formation
Inferred Resource estimates = quantities and grades of hematite BIF or magnetite BIF Exploration Target estimates = potential size of the target BIF based on known geology + aeromagnetic interpretation (includes Inferred Resources)
nd = not determined > = greater than < = less than Mt = million tonnes
DTS = magnetic concentrate from Davis Tube Separation (weight %)