The Cobar Superbasin Overview

The Cobar Superbasin is one of several intracratonic basins developed in the Lachlan Orogen during the Silurian/Devonian; it is the richest polymetallic basin in the Lachlan Orogen as evidenced by the impressive pre-mining metal inventory; >2.2 million tonnes copper, >7.0 million ounces of gold, >4.7 million tonnes of zinc, >2.8 million tonnes of lead, and 145 million ounces of silver.

Location of mineral deposits in relation to basement architecture (courtesy Vlad David)

Location of mineral deposits in relation to basement architecture (courtesy Vlad David)

 

The Superbasin developed as four deep-water troughs surrounded by shallow-water flanking shelfs.

The northern portion, containing the Cobar Trough, is characterised by siliciclastic sediments locally intruded with felsic volcanics. The southern portion, which contains the Mt Hope and Rast Troughs, is dominated with volcanics of bimodal character and volcaniclastic rocks intercalated with sediments. These two troughs are separated from the Cobar Trough in the north by a major NE trending basement fault zone called the Nymagee-Wagga Zone.

The predominantly sediment-hosted mineralisation (Cobar-style mineralisation) in the southern volcanic/volcaniclastics portion has been characterised with discontinuous, remobilised, en-echelon lenses hosted within high strain zones close to early Devonian porphyritic intrusives, which are in proximity to active syn-sedimentary rift faults. All known deposits are structurally controlled and typically occur as narrow, short strike length pipes, lenses and veins, with a considerable vertical extent.

Peel believes that the prospectivity of the southern portion of the Cobar Superbasin (the area covered by Peel Mining’s tenements) is extremely high, factoring in the presence of metal-bearing fluids and high strain domains which favour mineral deposits and occurrences; this is supported by the presence of major deposits in the area such as Nymagee-Hera, Mt Hope Mine, May Day mine, and of course the Mallee Bull polymetallic deposit; this deposit is characterised by the aforementioned Cobar-style of mineralisation, with a strike of less than 200m, 5-20m width and current down dip extent of more than 550m. The major mines and deposits within the Cobar Superbasin are summarised in the table below:

Deposit/Mine Main Metals Resources Comment
Elura(now re-named Endeavor) Zn-Ag-Pb-(Cu) Original Pre-mining resource – 45 Mt at 8.5% Zn,
5.3% Pb, 9g/t Ag
As at May 2006
Reserves – 11Mt at 7.9% Zn, 4.5% Pb, 66g/t Ag
Resources – 17.6Mt at 8.7% Zn, 4.9% Pb, 69g/t
Ag
Owned and
operated by
Toho Zinc’s CBH Resources Ltd
CSA Cu-Ag As at Dec 2012
Reserves – 6Mt at 4.6% Cu, 18g/t Ag
M&I Resources – 5.4Mt at 6% Cu, 24g/t Ag
Inferred Resources – 6Mt at 5.8% Cu, 21 g/t Ag Production 1964-2012 > 1,000,000t Cu
Owned and
operated by
Glencore-Xstrata
Peak Au-Cu-Pb-Zn-Ag Pre-mining Resource – 4.5Mt at 7g/t Au, 21g/t Ag,
1.7% Zn, 1.5% Pb, 0.7% Cu
As at May 2006
Resources and Reserves – 6.35Mt at 6.9g/t Au,
0.74% Cu
(Perseverance, New Occidental, New Cobar)
NewGold Inc
McKinnons Au-As-Sb (Ag-Zn-
Pb-Cu-Hg)
As at May 2006
Reserves- 1.8Mt at 2.0g/t Au
Resources – 4.5Mt at 1.2g/t Au
Mined – 1.2Mt at 2.6g/t Au
Cobar
Consolidated
Wonawinta Ag As at March 2012
Reserves – 10.1Mt at 80g/t Ag, 1.1% Pb,(25.9Moz
Ag)
Resources – 26Mt at 63g/t Ag, 0.8% Pb (52.8Moz
Ag)
Cobar
Consolidated
Hera Au-Zn-Pb-Ag (Cu) As at June 2011
Resources – 2.44Mt at 4.1g/t Au, 16.7g/t Ag, 0.2% Cu, 2.8% Pb, 3.8% Zn
YTC
Resources
Nymagee Cu-Zn-Pb-Ag As at December 2011
Resources – 8.1Mt @ 1.2% Cu, 0.3% Pb, 0.7% Zn
and 9g/t Ag.
YTC
Resources
Tritton Cu As at June 2011
Resources – 29.9Mt at 1.6% Cu
Straits
Resources
Mineral Hill Cu, Au, Ag, Pb, Zn,
Ag
5.2Mt at 1.2% Cu, 1.6% Pb, 0.9% Zn, 37g/t Ag,
1.33g/t Au
KBL Mining Ltd
May Day Au, Pb, Cu, Ag Reserves: 193,000t @ 2.92g/t Au, 11g/t Ag Peel Mining Ltd

Cobar Basin Mines and Deposits: Historic and Current Reserves and Resources