The Mt Gibson Project (Mt Gibson) is located 290km northeast of Perth, in the Murchison Province of Western Australia, and 100 km south of the world-class Golden Grove volcanic-hosted massive sulphide (zinc-copper) mine. Both Mt Gibson and Golden Grove lie within the same volcano-sedimentary sequence: the Yalgoo-Singleton Greenstone Belt.

Click here to view a district geology map.

Legend originally acquired Mt Gibson from Oroya Mining Limited in November 2005, principally to pursue the untested volcanic-hosted massive sulphide potential (zinc-copper-gold) beneath the existing oxide gold pits.

 

The Mt Gibson Project comprises 215km² of exploration and mining tenements, and a gold mine with associated infrastructure that is currently on care and maintenance. The mine infrastructure is connected to the State Electricity Grid and includes a:-

• modern camp equipped to accommodate 160 employees and contractors,

• serviceable airstrip,

• established bore field.

Legend has leased the accommodation facilities and airstrip to Extension Hill Pty Ltd for a period of three years commencing 1 July 2008 for an annual rental of $500,000, (ASX Announcement: 11 June 2008).

Mt Gibson started life as a gold mining operation in 1986 following the discovery of gold in outcropping laterite (ironstone). Mining was conducted until 1998, with 95% of ore coming from 14 open pits. The operation produced 870,000 ounces of gold from 16.5Mt of ore at an average grade of 1.68 grams per tonne (g/t).

The current gold Mineral Resource (Indicated and Inferred) is 8,754,000 tonnes at an estimated grade of 1.98 g/t gold (559,000 ounces of gold). This resource is not economic at the current gold price.

An extensive rehabilitation programme involving the decommissioning of the plant/mill infrastructure is currently being undertaken with a view to reducing environmental bonds.

Click here to view the current Mt Gibson mineral resource summary.

A coherent zinc anomaly with a strike-length of over 5 km has been delineated by approximately 7,000 shallow holes (depth less than 100m) drilled to evaluate the near-surface gold resource. This zinc anomaly is broadly coincident with the main line of open pits.

Click here to view an aerial photograph of the Mt Gibson open pits and the footprint of the near-surface zinc anomaly.

Only 21 holes have ever been drilled deeper than 300 metres vertically beneath the near-surface zinc anomaly, and these were designed to test gold targets. Not all deep holes were assayed for zinc, although zinc sulphide was observed in many. Of the holes that were assayed for zinc, hole BGRCD-009 returned the best result of 4m at 13.4% Zn from 775m.

The limited historical drilling has defined a zinc-rich position within the mafic-felsic volcanic sequence. Exhalative, boron-rich seafloor sediments, mainly of volcanogenic chemical sedimentary origin, are inferred to have formed at the same time as the zinc mineralisation. The near-surface oxide gold mineralisation is interpreted, in part, to reflect oxidised volcanic-hosted massive sulphide, similar to the situation at Golden Grove.

Between June and August 2006, Legend completed an eight hole deep diamond drilling programme totalling 5,978.6m, targeting volcanic-hosted massive sulphide zinc-copper mineralisation over a 6km strike length. All drillholes intersected sub-economic zinc sulphide mineralisation, associated with laminated cherty metasediments intercalated with mafic and intermediate volcanics. The predictive geological model developed as a result of this drilling has identified important trends to new opportunities within this large base metal system.

The Project was joint ventured to Oz Minerals Limited (ASX:OZL), between May 2007 and November 2008, who brought significant expertise to the project via their operating knowledge of the Golden Grove Mine, (ASX Announcement: 8 May 2007). Oz Minerals completed five diamond drillholes for 2,956.6m, all of which intersected the prospective “zinc horizon” including a best interval of; 3.77m @ 6.75% Zn from 310m in MGB001 from within a broader mineralised zone of 30.29m @ 1.14% Zn from 285.37m, (ASX Announcement: 10 June 2008). This work also confirmed the geological model originally proposed by Legend.

Evaluation of the extensive geological and geochemical datasets related to the volcanic-hosted massive sulphide zinc mineralisation will be completed to assist further programmes.

Since the withdrawal of Oz Minerals, Legend has undertaken an extensive review of the gold potential of the Mt Gibson Project assessing the structural and lithological controls on gold mineralisation. The review involved the specialised consulting services of Predictive Discovery Pty Ltd using technology developed at CSIRO in the Predictive Mineral Discovery Co-operative Research Centre. The results have been extremely valuable in advancing the knowledge of the structural and lithological controls on the gold mineralisation. Unfortunately this work has not identified any new favourable structural positions of sufficient size to warrant drill testing.

IMAGES FROM MT GIBSON:

 

Diamond drill rig working at Mt Gibson		Geologists inspecting drill core		Wombat open pit
Laterite profile at Enterprise pit		Orion open pit		Mt Gibson accommodation village

Click on any of the photos above to view a larger image in a new window

LINKED DIAGRAMS:

Mt Gibson Location and District Geology Map

Mt Gibson Project Geology Map

Mt Gibson Aerial photograph of open pits and footprint of near-surface zinc anomaly

Mt Gibson Predictive Geological Model.