AustralasiaGold
Limited
ABN 93 104 757 904
 

EYRE PENINSULA, SOUTH AUSTRALIA - MURNINNIE PROJECT
Figure 1 Tenement Location

Summary
The key attractions of the Murninnie mine and environs are:

  • its situation in the southern part of the “Olympic Domain” – the geological province containing Prominent Hill, Olympic Dam (Roxby Downs), Carrapateena and Moonta-Wallaroo iron-oxide-copper-gold (“IOCG”) deposits;
  • the presence in intermittent outcrop of copper +/- gold mineralisation over more than 4 km length of strike;
  • the Murninnie mine, developed to 50m depth, historic producer of several thousand tonnes of ore containing high grades of oxide copper, with variable bismuth, gold and silver credits, not tested by a single drill hole;
  • alteration characteristics of the outcropping mineralisation similar to those associated with of IOCG styles of mineralisation;
  • the proximity of granitic intrusions “Hiltaba” Suite, widely associated with copper-gold and other mineralisation throughout the Gawler Craton;
  • soil geochemical data indicating potential for mineralisation more extensive than that historically discovered by prospectors.

Location and Title
Exploration Licence (“EL”) 3542 and Private Mine (“PM”) 156 (“the Tenements”) cover approximately 67 sq km, centred approximately 35 km SW of Whyalla and 55 km NE of Cowell in eastern Eyre Peninsula, South Australia (Figure 1). Subject to acquisition of interests under the current agreement, the Tenements are 100% owned by the Murninnie Mine Syndicate.

History and Access
Discovered in the early 1860’s, the Murninnie mine shipped a recorded (i.e. minimum) one thousand tonnes of high-grade oxidised ores of copper with variable bismuth content, before the beginning of the 20th Century, from lodes in a fracture zone in granitoid and metasedimentary metamorphic rocks of the Hutchison Group.

The area is used for sheep grazing, and is lightly vegetated. It is well serviced by the City of Whyalla and regional transport, communications and services systems.
Regional Geological Setting
The Tenements are situated in the southern part of the “Olympic Domain”, within the Gawler Craton. This is the belt of rocks of early to mid-Proterozoic age, intruded by granites of the Hiltaba Suite, which contains the Olympic Dam, Prominent Hill and Carrapateena IOCG deposits to the north, and the Moonta-Wallaroo copper orebodies to the south-east (Figure 2, extracted from selected publications Primary Industries and Resources South Australia (“PIRSA”). It lies within the G8 (NNE) lineament and just west of the G2 (NNW) lineaments defined by O’Driscoll.

Figure 2 Extract of PIRSA Solid Geology of SA showing Hiltaba granites in proximity to Murninnie

Regional magnetic data generally defines the dominant north-south trend of local stratigraphy and structure, reflecting the highly magnetic character of the Hutchison Group rocks and demagnetised character of the mylonite. Detailed gravity data is yet to be acquired.

The mineralisation of the Murninnie Tenements is hosted in sheared metasediments, granitic gneiss and amphibolite of the Hutchison Group, in the margins of a north-south oriented mylonite zone.

East of the mylonite zone the downfaulted easterly extension of the Hutchison Group basement and Hiltaba Granite intrusions is buried beneath Tertiary sediments about 100m in thickness.

The tenement area is gently undulating, on two levels separated by the escarpment. Regolith comprises sandplain, soil and eluvium, with partly developed calcrete, and less than 5% of rubbly outcrop.

Mineralisation Murninnie
Copper-Gold Deposit
The Murninnie deposit is exposed over a strike length of more than 400 metres by the incision of a steep-walled gully. Mineralisation is contained within a steeply dipping multiple lode system apparently influenced by its intersection with a number of cross-cutting structures. A series of adits, shafts and internal winzes exposes the mineralisation, extending to a maximum depth of 52 metres. As noted, ore totalling a few thousand tonnes has been extracted and selected higher grade material exported during the late 19th Century. Some of the underground development is exploratory in nature, and has been extended between 1900 and 1950, since the conclusion of mining.

One parcel of ore amongst several noted in the “Record of Mines - Summary Card” of 1901, from the records of PIRSA refers to “60 tons of ore containing 5% bismuth and 10% copper”; another, “15 tons of ore sent to smelters, averaged 10% Cu, but no bismuth”. Comments on the geology of the deposit assert that the lodes also contained “ …nickel, silver and cobalt.”; however no analyses are recorded.

Figure 3 Lodes at Murninnie with oxidised secondary copper mineralisation and hematite alteration

The material mined and exposed by mining is pervasively oxidised, with abundant secondary
copper and bismuth minerals. Weathering of the lode system is conspicuously deeper than is apparent elsewhere on the Tenements, where semifresh rock appears in places in outcrop, and fresh sulphide (with accessory gold) is occasionally observed in outlying mineralisation (see next section).
.
The mineralisation of the Murninnie area shows evidence of a number of the characteristics associated with the IOCG deposits including associated gold, multiple intrusions of Hiltaba-age granite in close proximity, and haematitic, potassic and calcic alteration. (Figure 4)

Hand specimens taken during the last three years from mine spoil and lodes exposed underground have yielded peak assay values of 7.7% copper, 3.8 grams/tonne gold, 2.4% bismuth and 10.0 grams/tonne silver.
Mineralisation elsewhere on the Tenements
Although outcrop is limited, prospecting has revealed isolated showings of copper mineralisation generally along strike and to the south of the Murninnie mine (Figures 1 and 4). Strike continuity of mineralised structures has been indicated by soil sampling over an area of approximately 4 x 2-km in the vicinity of the observed mineralisation.

The soil geochemistry results indicate that copper-gold mineralisation may extend over a greater width than the confines of the vein structures which have been mined historically.

Copper and gold mineralisation has been identified with quartz in epidote-altered amphibolite host rocks as well as in haematitic breccia (Figure 4) and gossanous iron oxide masses within meta-sediment and sheared granite or granite-gneiss.
Figure 4 Haematitic breccia-hosted copper mineralisation at The Scratchings
Program
Australasia Gold is proposing to evaluate this highly prospective tenement by systematic prospecting and rock sampling, extension of the soil geochemical survey, detailed gravity and magnetics surveys, shallow and deeper drilling of the subcropping western part of the sequence, as well as evaluation of the basement concealed at depth beneath Tertiary sediments in the eastern half of the EL.

Prospects
The Murninnie tenements are prospective for copper-gold mineralisation in a variety of structural settings. Chemically and mineralogically the alteration associated with the exposed mineralisation gives indications of associations with the IOCG(U) suite of deposits identified elsewhere in the region.