The Broken Hill orebody is the largest silver-lead-zinc deposit of its kind in the world. It is located in the southeastern part of the Curnamona Province in Proterozoic rocks around 1,700 million years old.

GCR has 100% of EL6518 located to the south-east of thew township of Broken Hill (see figure below).  Through an extensive geological and geophysical database along with ground exploration three styles of minealisation are thought to be prospective in the tenement:

• Broken Hill-style mineralisation;
• High grade nickel-copper-platinum-palladium mineralisation; and
• Shear-hosted and iron oxide copper-gold mineralisation.

Vale (CVRD-Inco) - GCR Joint Venture

GCR's joint venture in the southern half of the Broken Hill tenement was designed to primarily test the PGE rich Ni Cu sulphides associated with the Neoproterozoic ultramafic and mafic dykes and differentiated bodies intruded into the high grade metamorphic rocks of the Paleo- and Mesoproterozoic Willyama Supergroup. Other potential exploration targets include iron oxide copper gold (IOCG) deposits.

Based on previous drilling results the most significant Ni Cu-PGE prospects appears to be associated with ultramafic rocks at the Mt Darling Ck prospect and also within the Mulga Springs prospect. Previous diamond drilling and rock chip sampling at Mulga Springs has returned strongly mineralised PGE, Ni, Cu and anomalous Au values. This mineralisation is situated along the basal contact of an olivine rich cumulate ultramafic (UM) which has a width of up to 100m and is elongate and discontinuous along strike. The UM unit associated with the known mineralisation is thought to extend in a south easterly direction into the joint venture area and a review of the magnetic data indicates that close spaced magnetic data may be of use tracking the UM units under cover.

As part of the broader exploration review process three areas were identified where moving loop EM surveying was deemed appropriate to test potential feeder zones around known ultramafic bodies. These areas include Mt Darling Ck, coincident magnetic and gravity anomalies associated with malachite staining at Crows Nest and areas to the south of the Little Broken Hill Gabbro complex where there were gaps in the historical EM data.

Data from the moving loop EM and reprocessing of the historical EM data failed to identify any conductive body that could be associated with massive sulphides. However initial field investigations have identified a number of mineralised locations, eg the Crows Nest prospect where malachite stained mafic rocks returned elevated values of copper and gold and a small magnetic feature with outcropping metagabbro which also returned elevated copper and gold values.

Further soil geochemistry in areas of residual soil and RAB/Aircore drilling in covered areas is required to test a number of magnetic targets adjacent or marginal to known ultramafic bodies. The detailed aeromagnetic data has helped to define the position of several geophysical anomalies which previous drilling identified as mafic lithologies below shallow transported material. Given their proximity to the Mulga Springs type location these anomalies are worthy of RAB drill testing.

Exploration by our Joint Venture partners over the past two years confirm the areas prospectivity for all three styles of mineralisation.

Drilling of ultramafic bodies by Vale at Little Broken Hill Gabbro returned anomalous copper and nickel values across several holes.  In addition the drilling confirmed the extension of the ultramafics under cover opening up the potential for hidden mineralisation elsewhere in the tenement.

History

Historically, work has focused on exploration for the Broken Hill-style Pb-Zn-Ag mineralisation, however a number of campaigns in the 1970’s and 1980’s recognised the association of small PGE-Ni-Cu gossans associated with intrusive mafic-ultramafic complexes which are probably about 600 to 700 million years old, much younger than the Broken Hill host rocks.

Sampling of these gossans returned spectacular grades of PGE’s and gold, commonly over 15 g/t combined. In the 1970’s CRA drilled a diamond hole into the Mulga Springs prospect and recorded a two to three metre intersection of banded pyrrhotite-pendlandite-chalcopyrite associated with cumulate textured olivine rich mafic rocks.

Whilst the tenor of this hole was assessed, no systematic analyses for PGE’s were undertaken. GCR undertook to drill a hole close by in 2001 and returned an intersection of 2m at 10.9 g/t platinum, 23.6 g/t palladium, 0.94 g/t gold, 6.12% copper and 4.45% nickel in massive sulphide.

Geological mapping by the NSW geological survey had outlined a discontinuous, locally highly sheared zone of mafic rocks extending from Mulga Springs, almost 9km to the northwest to the Moorkaie prospect. GCR undertook prospecting over this zone and discovered a number of previously unmapped mafic intrusions and gossans which returned highly anomalous PGE’s. The Back Ridge gossan returned 40g/t Pt+Pd for example.

At about this time GCR undertook to consolidate tenure in the district and secured at large licence to the south which hosted the Little Darling Creek PGE zone also assessed during the 1980’s. From 2003 to 2005 a joint venture with Sipa Resources led to accumulation of more ground, in particular, the Red Hill and Little Broken Hill Gabbro prospects, both hosting PGE-bearing mafic-ultramafic complexes. Sipa undertook ground EM surveys over Mulga Springs and the Moorkaie Prospects and drilled holes at Mulga Springs, Mulga West and Round Hill. Drilling proved unsuccessful however a distinct EM anomaly was detected on the down plunge extension of surface mineralisation at Moorkaie.

 Vale (CVRD-Inco) - GCR Joint Venture

In 2006 a joint venture with Inco/CVRD, now Vale,was formalised to work on the southern portion of the tenement.  The joint venture was designed to primarily test the PGE rich Ni Cu sulphides associated with the Neoproterozoic ultramafic and mafic dykes and differentiated bodies intruded into the high grade metamorphic rocks of the Paleo- and Mesoproterozoic Willyama Supergroup. Other potential exploration targets include iron oxide copper gold (IOCG) deposits.

Based on previous drilling results the most significant Ni Cu-PGE prospects appears to be associated with ultramafic rocks at the Mt Darling Ck prospect and also within the Mulga Springs prospect. Previous diamond drilling and rock chip sampling at Mulga Springs has returned strongly mineralised PGE, Ni, Cu and anomalous Au values. This mineralisation is situated along the basal contact of an olivine rich cumulate ultramafic (UM) which has a width of up to 100m and is elongate and discontinuous along strike. The UM unit associated with the known mineralisation is thought to extend in a south easterly direction into the joint venture area and a review of the magnetic data indicates that close spaced magnetic data may be of use tracking the UM units under cover.

As part of the broader exploration review process three areas were identified where moving loop EM surveying was deemed appropriate to test potential feeder zones around known ultramafic bodies. These areas include Mt Darling Ck, coincident magnetic and gravity anomalies associated with malachite staining at Crows Nest and areas to the south of the Little Broken Hill Gabbro complex where there were gaps in the historical EM data.

Data from the moving loop EM and reprocessing of the historical EM data failed to identify any conductive body that could be associated with massive sulphides. However initial field investigations have identified a number of mineralised locations, eg the Crows Nest prospect where malachite stained mafic rocks returned elevated values of copper and gold and a small magnetic feature with outcropping metagabbro which also returned elevated copper and gold values.

Further soil geochemistry in areas of residual soil and RAB/Aircore drilling in covered areas is required to test a number of magnetic targets adjacent or marginal to known ultramafic bodies. The detailed aeromagnetic data has helped to define the position of several geophysical anomalies which previous drilling identified as mafic lithologies below shallow transported material. Given their proximity to the Mulga Springs type location these anomalies are worthy of RAB drill testing.