PROJECTS – mount hill

The Mount Hill prospects are located on south central Eyre Peninsula, EL 2905, 18-25km W and WNW of Port Neill. They are located on the northern edge of the Lincoln Uplands under unconsolidated Cainozoic sediments and, immediately N of Mount Hill railway siding, Mesoproterozoic sediments of the Blue Range Beds. The Port Lincoln-Kimba railway line extends through the centre of the prospect area.

There are several prospects that collectively form a series of long N- to NE-trending aeromagnetic anomalies. The eastern anomaly is the structurally most complex with evidence of tight folding and faulting. It forms the eastern limb of a major antiformal structure (Fig. 11) that plunges N under the Mesoproterozoic sediments. The western anomalies form the western limb of this structure and represent two parallel BIF units in the south. As well as faulting sub-parallel to strike, there are a number of NW-trending breaks and offsets in the BIF anomaly trends interpreted as cross faults.

Cowan (2005d) undertook detailed reprocessing and enhancement of the aeromagnetic data using the latest enhancement and analysis techniques, estimation of magnetic source depths and mapping of major magnetic elements and lineaments.

Hematite Targets
Identification and screening of possible hematite targets by including interpreted faults and fold hinges Cowan (2005d) was hampered by the variable thickness of cover. Magnetic modelling and inversion were undertaken on a selection of potential targets.

Models 1-4 on the main eastern BIF suggest tabular bodies at depths of 17-113m below surface, dipping to the east at ca. 70º. Indicated thicknesses are ca. 80-120m. Model
5 in the N of the eastern BIF suggests a tabular body at 144m depth with a width of 262m, dipping steeply E. The increase in depth between Model 4 and Model 5 may suggest extensive oxidation of BIF, thicker cover or an increase in plunge of the fold structure.

Models 6-7 on the central BIF anomalies suggest tabular bodies at depths of, respectively, 17m and 206m, the latter below the Blue Range Beds.

Models 8-16 on the western BIF anomaly trend suggest near vertical tabular bodies at depths of 30-193m with widths of 75-175m. Again the variation in depths suggests either extensive oxidation of the BIF, deeper cover or an increase in plunge of the fold structure. Some western BIF units mapped as outcropping give magnetic source depths in the range 80-100m suggesting oxidation of magnetite to hematite. Other potential targets include favourable structures such as interpreted faults and fold hinges.

Based on the modelling and interpretation, eight preliminary hematite targets have been identified (Fig. 11).

Fig. 11 :: Mount Hill :: Location of BIF outcrops/prospects in relation to
aeromagnetic imagery (Click to see image)