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Deposit Synonyms
Blinman Extension; Mc 10428; Mc 1265; Mc 1571; Mc 237; Mc 427; Mc 601; Old Blinman; Sml 162; Sml 86
Mineral District
Deposit Summary
Cu mineralisation in a NS-trending structural zone marginal to the eastern boundary of the Blinman Diapir. Historically significant mine, with production from 1862-1918 estimated at 203,400 tonne mined for 10,000 tonne copper metal product.
Deposit Description
BLINMAN, mine was once the largest and most productive copper mine in the Flinders Ranges, yielding from 1862 to 1918 ~10,000 tonne of copper metal from ~203,400 tonne of ore mined. The early phase of mining produced hand sorted ore for export overseas, then a copper matte (~95%Cu) product from on-site smelting operations. From 1903-08 large scale operations commenced for production mainly of a copper matte to 55-70%Cu. After 1908 to closure small parties of tributary workers gouged out parcels of high grade ore. Dickinson (Bull 21, 1944) describes copper mineralisation as associated with a host “mine dolomite,” being a unit within a ~76m sequence of silty metasediment interpreted as an elongate NS-orientated exotic block in host diapiric rock of the regional Blinman Diapir. Historically 3 distinct ore-shoots were identified, the "Southern lode," the "Northern Lode," and a smaller apophysis named the "Counter Lode arising from the "Northern Lode."
Dickinson describes 3 forms of mineralisation, small veins occupying tension fractures that trend EW transversely across the deposit, as open cavity fillings and linings on the walls of vughs, and as disseminations in the massive dolomite, as irregular grains and patches. Approximately 95% of the deposit is estimated to occur as the latter, averaging 3-4% Cu. High-grade mineralisation is mainly associated with the transverse tension gashes identified as of late stage in the overall deformation sequence. Copper mineralisation in the upper, oxidised zone (90-110m), is dominantly cuprite and malachite, and in the underlying sulphide zone chalcopyrite, bornite, chalcocite and minor pyrite. Gangue minerals include dolomite, barite and calcite, with some quartz.
In 2009-11 exploration by Helix Resources Ltd confirmed an overall stratiform orebody, with a near vertical dip. Alteration style is that of a complex, zoned alteration overprint of the “mine sequence,” not confined to a single stratigraphic unit. There are zones of dolomitisation, silicification, albitisation, argillic alteration, and associated with multiphase breccias/veining. Alteration zoning appears to be a bleached clay/sericite cores around high grade zones grading outward to pink dolomite alteration. High grade zones are represented by EW-trending sets of sulphide veins, with bleached selvages (potassic alteration), with a later more northerly set of quartz-carbonate-sulphide veins also recognised.
Results from drilling, and geophysics were interpreted to indicate a lateral continuity of the mineralised sequence greater than was previously recognised. Also a flattening of the dip of the mine sequence at depth. They interpret the timing of mineralisation as probable Delamerian, and suggest a possible relationship to the intrusion of mafic rocks into the diapiric structure. They present an overview of mineral prospectivity of the Blinman Diapir. Assuming a scenario of a stratigraphy relatively in situ, they discuss the potential of the margins of the diapir where they suggest the overall form of a domal structure of the diapir might indicate increased fluid flow along its margins. Also greater prospectivity of near vertical stratigraphy as suggested by the decrease in grade at Blinman of the flat-dipping “mine sequence” due to the preferred development of late stage tensional structures in sediments with the steep dips. Area is registered as a Geological Monument (# 1036).
Discovery Year
? 1859
Commodities
Copper
Ore Minerals
Bornite, Chalcocite, Chalcopyrite, Copper, Cuprite, Malachite
Gangue Minerals
Barite, Calcite, Dolomite, Limonite, Pyrite, Quartz
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