Yellow Mountain Joint Venture
The Yellow Mountain copper-gold project (EL6325) is located 55 km north of Condobolin in central western NSW in the Lachlan Fold Belt, at the intersection of the Gilmore Suture and the Lachlan Transverse Zone (which hosts the Cadia Valley and Northparkes copper-gold deposits). Targets at Yellow Mountain include porphyry copper-gold deposits and disseminated epithermal gold deposits.
The project is subject to a joint venture between Golden Cross, CBH Resources (which took over original participant Triako Resources) and Paradigm Metals, with Paradigm farming-in, operating and sole-funding the joint venture. Paradigm currently holds a 30% interest and has the right to increase that to 51%, at which time Golden Cross will hold 30% and CBH will hold 19%.
A key feature in the exploration rationale at Yellow Mountain is a large buried NNW-trending magnetic anomaly (the Melrose Magnetic Anomaly) which has a strike length of approximately 14km. Almost all of the known mineralisation and geochemical anomalies at Yellow Mountain are associated with this magnetic feature. An outlying section of the tenement hosts the historic Yellow Mountain Mine (Figure 1).
Geology and Mineralisation
The Yellow Mountain area is located in the Canbelego-Mineral Hill Volcanic Belt. Ordovician siltstones and sandstones of the Girilambone Group are unconformably overlain to the north by the northwest-trending Siluro-Devonian Kopyje Group (part of the Cobar Supergroup).
Locally, the Kopyje Group lithologies comprise tuffs and minor lava flows of the Majuba Volcanics and a variety of tuffaceous sediments. Intrusive rocks in the area include the Devonian Yellow Mountain Granite, a Devonian intrusive quartz-feldspar (dacitic) porphyry and the Silurian Erimeran Granite.
Four main styles of mineralisation are known in the Yellow Mountain area:
- The Yellow Mountain Mine prospect has some similarities to Cobar-style structurally controlled Cu-Au and Pb-Zn mineralisation associated with veins in high strain zones;
- Disseminated gold (+/- arsenic) mineralisation in Ordovician sedimentary and volcanic rocks at Quarry Hill, possibly related to distal porphyry mineralisation, or alternatively to ‘Carlin-style’ sediment-hosted gold style deposits;
- Gold-copper (+/-molybdenum) mineralisation in andesite and intrusive rocks associated with quartz veining and possibly of a ‘gold porphyry’ style (e.g., Fountaindale prospect).
- Skarn (including Cu-Zn-Ag-As sulphide) mineralisation at the contact between the Melrose Volcanics and the Erimeran Granite.
The most significant past producer was the Yellow Mountain Mine in the north, which incomplete records indicate yielded 0.365t Cu, 2.74t Pb and 6.16kg Ag. Mineralisation here occurs in veins and stringers associated with altered volcaniclastic rocks of the Fountain Dale Tuff member of the Majuba Volcanics, and typically comprises pyrite-galena-sphalerite-chalcopyrite mineralisation with silver and gold credits.
The Melrose Magnetic Anomaly is interpreted to be caused by hydrothermal magnetite alteration around a possible copper-gold porphyry system (Figure 2). Triako drilled some 225 air-core holes over the anomaly to a maximum depth of 90m in 2003-2007, identifying the following geochemical anomalies:
- Gold anomalies associated with mineralisation within the Fountaindale Granodiorite and adjacent volcanics.
- A halo of gold-copper anomalies around the Fountaindale Granodiorite to the northwest, east and southeast.
- A group of arsenic-lead-zinc anomalies on the eastern margin of the main Fountaindale Granodiorite.
- A group of copper-zinc anomalies near the Erimeran Granite/Melrose Volcanics contact on the southwest margin of the Melrose Magnetic Anomaly.
- A group of zinc-arsenic anomalies at Rosedale in the far northwest margin of the Melrose Magnetic Anomaly.
Exploration at Quarry Hill at the northern end of the Melrose Magnetic Anomaly has defined a 4 sq. km gold-in-soil anomaly with associated arsenic. Past drilling by Triako intersected a 30m to +60m thick blanket of low grade oxide gold mineralisation grading 0.2 to 0.4g/t Au from surface. The best intersection was 16m @ 2.7g/t Au from 4m in PDH002.
Paradigm has completed an extensive air-core and reverse circulation drilling program, focusing on the Quarry Hill zone. In 2010, Paradigm drilled 74 air-core holes at the Quarry Hill prospect for 2,567m, targeting disseminated gold mineralisation. The extensive near-surface oxide gold horizon was confirmed with the mineralisation up to 50m thick. Highlights include:
- PQH001: 8m @ 1.0 g/t Au from 14m, including 4m @ 1.3g/t Au from 18m
- PQH028: 8m @ 1.0g/t Au from 10m
- PQH029: 36.5m @ 0.5 g/t Au from 0m, incl. 4m @ 2.4 g/t Au from 20m
- PQH030: 10m @ 0.64 g/t Au from 26m
- PQH044: 40m @ 0.5 g/t Au from 0m, incl 4m @ 2.0 g/t Au from 4m
The promising air-core results were followed up in 2011 with an RC drilling program testing for gold mineralisation at depth. A total of 16 vertical holes were drilled for 1,616m and intersected several wide shallow oxidised mineralised zones, with the best intersections being:
- PRC003 (oxide): 20m @ 0.5g/t Au
- PRC005 (oxide): 12m @ 1.45g/t Au from 28m, incl. 6m @ 2.0 g/t Au from 34m
- PRC008 (oxide): 30m @ 0.5 g/t Au
- PRC009 (sulphide): 37m @ 0.5 g/t Au from 71m, incl. 4m @ 1.4 g/t Au from 98m
Oxidation occurs to a depth of 50-70m in most holes, and gold mineralisation appears to be controlled by multiple low-angle faults within the meta-sandstones and schists.
The second phase of Paradigm’s 2011 drilling program was designed to test other prospects, including Quarry Hill South, for oxide gold mineralisation. A total of eight air-core holes at Quarry Hill South returned shallow oxide gold intersections within mafic volcanic rocks, over a strike length of approximately 150m. The best intersections were:
- PQS001: 2m @ 3.1g/t Au from 10m
- PQS005: 13m @ 1.0g/t Au from 9m – hold ended in mineralisation
- PQS007: 6m @ 3.1g/t Au from 5m
It is believed that the Quarry Hill South mineralisation lies within a low-angle structure dipping north. Mineralisation is shallow (less than 20m deep) and is open to the west beyond PQS005, with gold grades appearing to be significantly higher than at other Yellow Mountain prospects.
In early 2012, Paradigm collected 22 rock chip samples from the Yellow Mountain Mine area within the northern section of EL6325, to evaluate what had previously been considered to be a base metals target. Five samples returned gold assays of more than 1 g/t Au with maximum values of 5.5g/t Au, 267g/t Ag, 24% Pb and 11%Zn. Four of those had silver assays of over 100g/t Ag. Lead and gold values were shown to be closely related. Paradigm estimates a gold exploration target at the Yellow Mountain Mine of 10-15 million tonnes of shallow base metal and gold mineralisation which could be developed with further work, including further drilling and geophysical surveys.
Updated July 2012