Digging deep for success

AVOCA Resources is the Australia Mining Prospect Awards Explorer of the Year

Avoca Resources has seen the development of a number of deposits over the past 18 months, and has moved from greenfield exploration to production in the space of a year.

The Trident Gold Deposit was discovered by Avoca in October 2004, and lies midway between the gold mining camps of St Ives and Norseman, in the Eastern Goldfields of Western Australia.

The discovery of the Athena resource at Higginsville in February 2006 is the company’s second major discovery.

The discovery also brought the JORC compliant resource base at Higginsville to over 1 million ounces.

Predevelopment work commenced immediately in parallel with the feasibility study, yielding an initial mining reserve of 582,000 ounces.

Underground development commenced in January 2007, with ore production commencing in June 2007.

Production is planned to reach 200,000 ounces per annum by 2008, with average life of mine cash costs approaching or bettering the global gold sector.

Avoca purchased the Higginsville Project on 30 June 2004, and drilled five infill diamond drill holes in August 2004.

Detailed examination of these holes, and the subsequent re-logging of previous diamond holes, led to dramatic changes in the geological interpretation of the site.

Shear fabric was observed sub-parallel to the core axis, and the most favourable lithology lay further west of the existing drilling.

The majority of veins were flat tensional veins bound by the zones of steep shear fabric and not flat lodes as previously interpreted.

The previous interpretation of primary texture was reinterpreted as an alteration texture overprinting the shear fabric.

The decision was made to change the orientation of the drilling and drill from east to west.

Potential steep east-dipping structures were targeted in the more favourable lithology to the west.

Four holes were planned and drilled in October 2004.

Three of the four holes intersected a thick new zone of mineralisation.

These holes were the discovery holes of the newly named Trident Deposit.

Trident discovery

Trident is a blind discovery only 250 m from an existing mine that closed six years prior to its discovery.

Higginsville was made company’s highest priority project, and this commitment played a clear part in the discovery of Trident.

A number of factors were critical to the success of the discovery.

The crucial factor underpinning the company’s success was the recognition of the high potential for underground ore at the Higginsville site from empirical observations.

The field is situated between the major mining centres of St Ives and Norseman, where underground production is considered to be low for the belt.

The company also highlighted a lack of deep bedrock drilling in the area.

A complete understanding of the key geological elements of the area was achieved through a comprehensive geological evaluation and reinterpretation of historical diamond drilling data.

The commitment of dedicated and experienced geological personnel, including former chief and senior mine geologists from St Ives and Norseman, was also a factor in Avoca’s success.

In March 2007, the company announced the further discovery of a major new ore zone, named Apollo, lying north of the planned Trident decline.

The discovery supports the company’s confidence that Higginsville will become a ten-year plus gold mine, more than double the estimated life of mine, upon which the current feasibility study was based.

Highly commended

Castlemaine Goldfields is located at the old Wattle Gully mine site in Chewton, central Victoria.

The Castlemaine Project, 30 km south of Bendigo, contains a high-density of gold workings and outlying smaller goldfields.

The company has 100% of the Castlemaine and Tarnagulla Goldfields, and controls Sebastian Goldfield through a joint venture.

The Castlemaine Goldfield has produced some 5.6 million ounces of gold, less than 1 million ounces of this came from underground, and from this Wattle Gully (415,000 ounces) made up half.

During the first nine months of 2006 a substantial volume of mining and geological information was gained from historical articles.

The articles related to mine production found in the Mount Alexander Mail and other newspapers from 1851 onwards.

The company digitised all available mine plans and historical sketches to build a comprehensive 3D exploration model for the Castlemaine project.

To date over 1300 plans and sections have been scanned and added to the interpreted geology contained in the model.

This significant amount of work has provided the necessary knowledge base to develop overall structural models, and define new high-quality drill targets in the goldfield.

The next phase of drilling will continue the rigorous exploration of the overall field, and will comprise both structural and targeted drilling in the northern and southern areas.

This company holds licences that cover the complete Castlemaine goldfield, and is well positioned to evaluate the whole field, a situation that has not previously occurred on this under-explored, high-potential field.

Castlemaine Goldfields is now in a position to launch drill programs across the larger goldfield and discover similar prospects with which to substantiate the multimillion ounce potential of the field.

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