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Deposit Synonyms
Lamberts; Rl 128
Mineral District
Deposit Summary
stratabound Cu-Au-(REE) mineralisation in core of Paratoo Anticline in host siltstone of the Burra Group abutting a diapir and dolerite dyke. 1987 drilling identified an inferred resource of 100,000t @ <1% Cu.
Deposit Description
PARATOO, stratabound Cu-(Mn-REE-Au) mineralisation located in the core of the Paratoo Anticline, and in host siltstone of the Saddleworth Formation. Early mapping indicated mineralisation over a strike length of about 3.5 km, striking NS, dipping steeply east. Host is grey-green, laminated, carbonate-altered (in the form of large carbonate pits) siltstone, with sandstone lenses that abutted a large diapir, and a dolerite sill. Basic igneous rock classified as diorite and microdiorite intruded the dolomite. Granite intruded black, carbonaceous siltstone in the western part of the workings.
Later mapping by Gawler Craton Resources PL suggest the absence of any substantial diapir, with the host being diverse metasediments of the Saddleworth Formation. They interpret a narrow elongate dome of ridge-forming manganiferous dolomite as of the Skillogalee Dolomite, and forming the main fold hinge of the Whydown Dome that passes just north of the Paratoo Mine. They suggest breccias, and breccia dykes within both the Skillogalee Dolomite, and Saddleworth Formation are the result of synsedimentary, soft-sediment deformation processes. Tenement holders IR & MA Filsell (2012) suggest a structural origin as fluidised diatreme breccia. mapping indicated 2 parallel ore zones ~110m apart, roughly parallel to the anticlinal axis and centred on shear zones, with indicated strike length of mineralisation of ~3,000m.
Percussion drilling (61 holes totalling 2895m in 1987) was carried out to delineate additional ore reserves. The drilling defined an inferred resource of 735,000 tonne @ 0.66% Cu for 4,800 tonne contained metal, and confined to 3 mineralised zones over 300 m strike distance, and centred over the historic open pits. Thse included 3 largish open cuts and several shafts. Samples from drill holes also returned weak gold values, and anomalous REE, with maximum values 3.5%La, 1.9%Nd, 0.6%Y, and 0.155Yb. Mapping and soil sampling in the vicinity of the historic workings demonstrated both structural and lithological controls to mineralisation. Low Au values from vein and soil sampling confirmed the results from the previous exploration.
In 2003 Range River Gold NL drilling defined a zone of low grade gold mineralisation extending NE for 900m along the line of lode. Best value was 1m at 2.35g/tAu from 47m in hole PARC5. They confirmed broad intervals of anomalous copper values associated with the gold, with the copper anomalism extending for 3,000m to the NE. Further drilling has also confirmed elevated REE values at least to the base of oxidation, with best value 7m @ 0.3% total REE from 5-12m.
Mineralisaton in the oxidised zone includes veinlets of malachite, with rare pyrite and chalcopyrite, and as abundant malachite and some chysocolla as disseminations, and impregnations in host metasediment, and as films on bedding planes and joints. At depth sulfides include pyrite, chalcopyrite, possibly digenite, trace native copper in altered host rock.
Range River suggest the copper mineralisation may have resulted from volcanogenic, synsedimentary deposition from cupriferous brines emanating from distal sources, and/or leached from contemporaneous airfall tuff diluted in the dominantly terruginous material. Cu-Mn-REE mineralisation may be related to mobilisation of inherent ore minerals in the host sediment, or related to a later igneous phase of dolerite intrusions, with accompanying potassic-silica alteration. Comparison was made with the timing of mineralisation at Burra (related to intrusion of porphyry dated at ~797Ma. Note also volcanics identified at Oodlawirra at 800Ma. Fander in thin section 958(pp34 Env 1112), describes a pyritic, silty dolomite possible layers of feldspar of pyroclastic origin.
Discovery Year
? 1888
Commodities
Copper, Rare Earths
Ore Minerals
Chalcopyrite, Chrysocolla, Cuprite, Malachite, Tenorite
Gangue Minerals
Hematite, Pyrite, Quartz
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