Historical mining at Bulgera totals 441,000 tonnes grading 1.65g/t Au producing 23,400 ounces of gold. Extraction, haulage and processing occurred when gold was selling at or below A$570 per ounce. With the gold price now exceeding A$2,000 per ounce of gold Norwest believes further resource definition and exploration work at Bulgera will add significant value to this asset.
The Bulgera Gold Project location is endowed with infrastructure including the large Plutonic Gold Mine operating nearby, 2 x gas-fired power stations, overhead transmission power lines, bore fields, airstrip and camp facilities.
The Bulgera Project comprises two granted exploration licences, E52/3316 and E52/3276, covering 36.8km² over the northeast end of the Plutonic Well Greenstone Belt, 200 kilometres northeast of Meekatharra.
The project is located 20 kilometres northeast of the Marymia mining centre and 48 kilometres via road from the operating Plutonic gold mine which has produced over 5 million ounces of gold since 1990. The Plutonic mine was recently purchased by Toronto listed Superior Gold Inc. (TSX-V:SGI).
Figure 2 - Shallow open cut mining up until 2004 from Bulgera Gold project (Venus pit backfilled).
The project contains four shallow open pits that have undergone two phases of mining between 1996 and 1998 and again between 2003 and 2004. Mining of the four pits Bulgera, Mercuri, Venus and Price produced a reported 440,799 tonnes of ore @ 1.65 g/t Au for 23,398 ounces of gold. The ore was treated at the Marymia mining centre during the first phase and the Plutonic processing facility during the second phase. Vango Mining Ltd (ASX: VAN) is in the process of re-developing key prospects at the nearby Marymia mining centre.
Bulgera is located at the north eastern end of the Plutonic Well Greenstone Belt, which is approximately 50 kilometres long and 10 kilometres wide and hosts the numerous Plutonic and Marymia gold deposits. The greenstone belt comprises mafic and ultramafic volcanic rocks, fine to coarse clastic sediments, and felsic to intermediate volcanic rocks, which generally dip to the north west at shallow to locally steep dips. Multiple suites of felsic to intermediate porphyries intrude the greenstone sequence and swarms of dolerite dykes locally crosscut the strata.
The Bulgera deposit consists of a shallow dipping sequence of amphibolites with narrow intercalated layers of ultramafic schist and metasediment. Gold mineralisation has been developed mainly in the amphibolites. Whereas at Mercuri a similarly dipping sequence of interlayered felsic volcanics, mafic volcanics, mafic sediments and minor felsic sediments is underlain by an ultramafic unit.
The gold mineralisation at both Mercuri and Bulgera deposits occurs within a broad shear zone which is about 45 metres thick. The shear zone contains multiple lodes which can be up to 140 metres long down dip. The gold mineralisation is associated with silica-biotite alteration of the host rock, and occurs in quartz veins.
Exploration Potential and Planned Work
The fieldwork to be undertaken by Norwest will comprise RC drilling of the strike and depth extensions of the Mercuri and Bulgera pits, and regional targets along the western Bulgera trend. In short, Norwest will be targeting extensions to existing well-defined mined structures, and subsequently applying the understanding from known structures to regional targets. The figures below show the Bulgera targets and the interpreted potential extensions that will underpin the development of Norwest’s gold exploration/expansion going forward.
The Bulgera gold project is located within 10 kms of Norwest’s Marymia project tenements which include the Jenkins and Dixon prospects. This provides the option to combine exploration programmes and benefit from the associated time/cost savings on rig and personnel use, mobilisation, accommodation and materials transport.