PROJECTS – koppio

Koppio aeromagnetic anomaly is 35km north of Port Lincoln and was investigated by SADM during the 1960’s (Shackleton, 1964a; Robinson, 1964). Outcrop comprises a series of jaspilite units or horizons that have been folded about relatively open N- to NW-plunging folds. Surface rock chip samples assay ca. 40% acid soluble Fe.

The main regional aeromagnetic anomaly is <500m wide and is folded into a series of 'Z'-vergence folds. The anomaly has a sharp southern margin but feathers out to the north suggesting there may be a body of magnetite BIF plunging N under shallow cover. The nature of the southern boundary with sharp truncation of N-trending anomalies immediately south is indicative of a thrust-faulted boundary that may also be shallowly N-dipping.

The most intense aeromagnetic anomaly is on the western limb of the interpreted Koppio synform. SADM carried out a broad spaced magnetic dip-meter survey over the prospect and sited 4 diamond holes (KD1-KD4) to test outcropping iron formation. Drillholes KD2-KD4 intersected variably oxidized magnetite iron formation. Drillhole KD1 did not intersect mineralisation. Drillhole KD-4 was sited to test the western part of the anomaly but was drilled sub-parallel to plunge as determined from foliation and banding. KD-4 intersected about 40m of banded quartz-amphibole-magnetite (+K-feldspar, apatite, biotite) BIF assaying 15-25% acid soluble Fe. The amphibole is a mixture of hornblende and grunerite.

In late 2001, bulk samples were collected and assayed from selected magnetite-rich intervals in KD-3 and KD-4. Results from KD-4 included 12.2m @ 38.4% Fe (100.58-112.78m) but since core was subparallel to banding, this represents only a very small interval or true thickness. Davis Tube separation yielded a 48.2% magnetite concentrate with 69.8% Fe and low phosphorous (0.09%), silica (1.8%) and alumina (0.3%). These results were considered very encouraging particularly combined with the observed shallow dips in the core of the synform.

SAIOG Geophysics and Drilling
In January 2002, a low-level aeromagnetic-radiometric survey was flown over Koppio at a nominal 20m agl for a total of 300 line km. Most of the area was flown at 40m line spacing but this was infilled to 20m above key areas.
The resolution of this survey was superior to existing aeromagnetic data and clearly showed that the most intense magnetic anomaly was NW of the SADM drillholes (Fig. 8).

Fig. 8 :: Koppio – Brennand :: Location of drillholes and BIF outcrops in relation to aeromagnetic imagery (Click to see image)

On this basis, drill hole KODD001 was sited to test what was considered to be a folded NE-dipping sequence of BIF. KODD001 intersected steeply to subvertically dipping BIF at ~140m and continued in an interbanded sequence of BIF, schist and amphibolite to ~362m. Based on the magnetic model there could be possibly more BIF below the EOH at 381m. The true thickness of the BIF sequence intersected in KODD001 is >140m but the aggregate true thickness of magnetite BIF is only ~70m.

KODD002 and KODD003 were sited on the eastern limb of the Koppio structure that dips relatively shallowly NW. These shallow dips were confirmed by drilling and KODD003 intersected interbanded magnetite BIF, schist, calcsilicate and amphibolite from 70-229m for an aggregate ~35m of magnetite BIF.

Unlike Greenpatch, Carrow, Bungalow and Iron Mount, which occur in a carbonate-rich sequence, the lithological sequence at Koppio comprises interbanded biotite-sillimanite schist and quartz-magnetite BIF with minor amphibolite sills or intrusives. This association suggests that the BIF occurs in a stratigraphically higher position close to the Yadnarie Schist at the top of the Middleback Subgroup. Banded quartz-magnetite BIF tends to occur as narrow bands 1-15 m thick.

The average grainsize of magnetite at Koppio is 0.1-0.3mm but ranges from 0.03-1.4mm. The majority is easily liberated by a coarse grind (-75µm; Table 14). Like Greenpatch, apatite occurs as discrete grains that can be magnetically separated.

Table 14: Aggregate assays for KODD001, KODD002 and PIRSA drillcore from Koppio

Drillhole	From (m)	To (m)	Intercept (m)	DTS magnetic con (%)	Fe (%)	SiO2 (%)
KD3	77.42	81.99	4.57	35.5	69.2	3.8
KD4	100.58	112.78	12.2	46.3	69.8	1.8
KODD001	143	153.9	10.9	26.75	65.39	8.02
KODD001	180.3	192.9	12.6	23.69	64.94	7.94
KODD001	228.74	244	15.26	37.79	70.11	2.87
KODD001	256.3	263.12	6.82	32.29	68.5	4.5
KODD001	266.85	272.5	5.65	33.51	68.33	4.86
KODD001	295.43	299.82	4.39	24.17	66.7	6.59
KODD001	312.7	328	15.3	26.04	58.37	16.53
KODD001	340.78	350.55	9.77	31.2	66.35	6.58
KODD001	355.16	360.08	4.92	29.55	66.48	6.6
KODD001	361.17	361.96	0.79	26.74	65	8.68
KODD001 Aggregate			86.4	29.5	65.6	7.8
KODD003	79.5	83.45	3.95	26.16	70.6	2.67
KODD003	85.22	86.9	1.68	28.81	70.2	2.57
KODD003	94.82	99.2	4.38	34	69.3	3.49
KODD003	112.58	121.31	8.73	32.8	69.16	4.09
KODD003	133	142.05	9.05	26.84	69.44	3.43
KODD003 Aggregate			27.8	29.9	69.5	3.5
Weighted Average, all Koppio samples				31.37	66.94	6.19

Fielding and Parker (2003) note that relatively poor Fe and SiO2 grades for some DTS fractions, particularly for KODD001 (cf KD4), may be due to poor grind procedures in early batches.

Magnetite and Hematite Resources
Although only a small iron-ore resource was previously identified at Koppio by SADM (2 Mt of siliceous ore, per 100 feet (30.5m) of depth, assaying 36-41% Fe), there is potential for a larger resource (Table 15) that could be viable as a satellite operation to the nearby Greenpatch resources. DTS magnetic concentrate assays for KODD001, as noted above, are not as good as those from KD4 so need to be checked.

Table 15: Inferred resources for Koppio based on very limited drilling combined with outcrop mapping and aeromagnetic interpretation

	Koppio West	Koppio East
Average true thickness based on intercepts with >20% DTS magnetite	24.4m (KODD001)	30m (KODD003)
Vertical extent of oxide zone below ground level	41.8m (KD4)	38.5m (KD3)
Assumed dip of BIF	80º NE	30º NW
Drillhole declination	60º SW	60º SE
Dip extent of magnetite BIF (excluding oxide zone) to 200m below ground level	161m	323m
Strike length (based on aeromagnetic interpretation and outcrop mapping)	600m	700m
Volume of magnetite BIF	5.3 million m3	6.3 million m3
Magnetite BIF density	3.4	3.4
Inferred magnetite BIF resource	18.2 Mt @ 29.5% DTS (65.6% Fe)	21.4 Mt @ 29.9% DTS (69.5% Fe)

No inferred hematite resources have been calculated due to insufficient data. However, two oxidised intercepts in KD3 (3.0-9.1m and 30.5-36.6m) contained an average 22.5% acid soluble Fe. The area of more subdued magnetics between Koppio and Brennand may be worth following up as a possible hematite target (Cowan, 2005a).

Based on magnetic modelling by Cowan, a series of holes were recently drilled by Centrex (early 2006). Results of the shallow RAB/slimhole RC drilling are still being compiled and evaluated by company geologists and were not available at the time of writing this report.

Regional Potential
The Brennand aeromagnetic anomaly 4km ENE of the Koppio anomaly is larger than Koppio but corresponds to an area of moderately extensive laterite and has not been properly investigated.

One SADM drill hole (BD1) was sited on the western edge of the anomaly and intersected several thin quartz-hornblende-magnetite-martite (apatite, pyrite, chalcopyrite) BIF bands (aggregate thickness 45m) interbanded with amphibolite and calcsilicate. No assays for Fe were recorded but visual estimates of iron oxides were 5-10%.

DTS magnetic concentrate results from a small section of SADM drillhole BD1 are similar to Koppio but with improved concentrate grades probably reflecting either coarser magnetite or better grinding (Table 16):

Drillhole	Drillhole From (m)	To (m)	Intercept (m)	DTS magnetic con (%)	Fe (%)	SiO2 (%)
BD1	105.46	106.68	1.22	26.9	69.3	2.22
BD1	143.16	151.64	8.48	25.18	69.4	2.51

The form of the Brennand aeromagnetic anomaly is similar to that of Koppio with similar magnetic amplitudes and it probably represents a N-plunging magnetite body in the core of an open synformal structure. The E-W strike length of the anomaly is just over 1000m and the anomaly is much more intense than Koppio inferring that Brennand could contain a significant magnetite BIF exploration target may be >20 Mt.

The Kapperna magnetic anomalies NE of Brennand have the highest magnetic amplitudes but the jaspilites appear to be thin, steeper dipping (Cowan, 2005a) and possibly only host small-medium sized magnetite BIF exploration targets.