PROJECTS – greenpatch
Greenpatch EL 2816 is a high priority target located only 10km NW of Port Lincoln. Previous work identified two prospects at Greenpatch: the main outcropping jaspilite area and a small hematite prospect in Section 147.
Section 147 prospect appears to be a small (a few thousand tonnes) hematite occurrence with little vertical extent and no aeromagnetic anomaly. It is likely a Tertiary laterite product.
The main Greenpatch jaspilite occurrence comprises several scattered outcrops of jaspilite and ferruginous quartzite over an area of ca. 20 sq. km (Fig. 5) within the core of an overturned N-plunging antiform. Rock chip samples average ca. 45% acid soluble Fe in well-banded martite-quartz (diopside, amphibole, minor magnetite) jaspilite. Martite is hematite pseudomorphing or replacing magnetite.
Magnetite BIF at Greenpatch is a strongly banded rock with typically monomineralic magnetite bands alternating with quartz, dolomitic marble and iron-rich silicate bands. Typically this rock is strongly recrystallised by high-grade metamorphism with upgrading and thickening of magnetite in the axial regions of folds. The jaspilite can be classified as carbonate to silicate-facies BIF with bands of quartz magnetite.
Fig. 5 :: Greenpatch location of drillholes, BIF outcrops, rock samples and interpreted geology in relation to aeromagnetic imagery
Host rocks comprise a sequence of diopside-quartz dolomitic marble, calcsilicate gneiss, graphitic mica schist, amphibolite and gneiss all of which have undergone deep lateritic weathering. While BIF is typically not as deeply weathered as adjacent units, the depth to fresh magnetite on the prospect is 20-40m.
The Greenpatch aeromagnetic anomaly is the largest and strongest magnetic anomaly on southern Eyre Peninsula and is about 3km wide E-W by 2km long N-S. Outcropping jaspilite occurs around the southern and eastern edges of the anomaly and combined with drilling information and interpreted magnetic models, defines a strongly magnetic unit about 120-200m thick folded around the nose of the antiform (Fig. 6). The extension of the aeromagnetic anomaly to the north albeit somewhat more diffuse is clearly due to the northerly plunge of the nose of the antiform beneath overlying metasediments of the Hutchison Group. The aggregate strike length of the BIF from magnetics and outcrop is ca. 6km although the cumulative total strike length of high intensity magnetic anomalies is 3.3km.
