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Deposit Synonyms
ML 6303
Mineral District
Deposit Summary
shear-hosted Fe-(Cu-Au) mineralisation in mylonitised gneiss within Karari Fault Zone segment. Resource (2008) of 10.6 Mt at 52.7%Fe, 0.4%Cu, & 0.1g/t Au. Production 2010-12 ~2.6Mt. Mine reopened by new owners in early 2015. .
Deposit Description
CAIRN HILL was first identified as a prominent 18km long, EW-trending linear, 18,000nT aeromagnetic anomaly located on the northern margin of the Mount Woods Domain, and presumably indicative of the presence of a major shear zone being an EW-trending continuation of the regionally significant, and anastomosing Karari Shear Zone as recognised to the west. Clark (2014) defined the mineralisation style as deep-level magnetite-rich end member of an IOCG system, wth age date on mineralisation in the range 1587-1525Ma.
The magnetic anomaly was drill tested in the early 1980s, with hole DD86EN 33 penetrating 2 narrow zones (1.4m & 6.8m wide), of massive to coarsely crystalline magnetite. Subsequently drilling of the western 600m of the magnetic anomaly confirmed 2 horizons of massive magnetite, and sheared, magnetite-rich gneiss carrying economically significant quartz-sulphide veining, with chalcopyrite, pyrite, pyrrhotite, and gold. Resource drilling of this western 600m cover of 5-30m of flat lying younger cover sediment. JORC compliant figures released by IMX resources (2010) were 11.4Mtonne at 49.5% Fe, 0.4% Cu, and 0.1g/tAu on a diluted basis. Continuing exploration has identified a continuation of the mineralisation along strike to the east and west, as well as at depth. Hole CHDCU02 returned values of 1,559ppmCe from 418-.15-419m.
Initial metallurgical test work demonstrated that simple magnetic separation using a coarse grind produced excellent recoveries of magnetite concentrate to >70% Fe, with economic levels of copper and gold in the non-magnetic grind fraction. The first ore was railed to Port Adelaide in October, 2010. Production ceased in June 2012 with ~2.6Mt ore mined. The mine was reopened in early 2015 by new owners Cu-River Mining Australia PL. Early exploration also identified a number of small radiometric anomalies coincident with outcropping gneiss. One anomaly was coincident with a calcareous sand unit of the Mount Anna Sandstone (Cadna-owie Formation). Assay results of 2 surface samples from here returned 1300 & 1450ppm U.
Discovery Year
? 1986
Commodities
Iron, Copper, Gold
Ore Minerals
Chalcopyrite, Gold, Magnetite, Malachite
Gangue Minerals
Feldspar, Pyrite, Quartz
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