EDNA MAY GOLD PROJECTClick here to view an Animated AV Presentation of the Edna May Gold Project >> Overview With its robust economics, geologically and metallurgically well defined ore-body, high Ore Reserve confidence and excellent recovery rate of more than 92%, Catalpa’s Edna May Gold Operations offers an attractive, long-term platform to grow a mid tier gold producer. Catalpa’s mine and processing schedule demonstrate average gold production at Edna May in excess of 100,000 ounces of gold recovered per annum for a life of mine of more than nine years, with production planned to commence in June 2010.
Geology In the Westonia area, the remnant greenstone belt is about 5km wide and 10km long. In the immediate mine area the greenstone sequence strikes WNW and dips NNE at approximately 60 degrees. From north to south the sequence comprises magnesian mafic-ultramafic amphibolites, locally called the “Hangingwall Ultramafic”, underlain by a mafic volcanic sequence (“Footwall Amphibolite”). South of the mine area the Footwall Amphibolite is intercalated with units of quartz-feldspar-biotite schist interpreted to represent metamorphosed felsic igneous rocks. All significant gold mineralisation is hosted by a quartz-feldspar-biotite gneiss of approximately tonalitic composition, the EMG and amphibolites in its immediate hangingwall and footwall. The EMG is an irregular, broadly conformable body that has been traced over a strike length of 1400m, averaging about 70m thickness. In the resource area it averages 100m thickness. The intrusive locally occupies the mafic-ultramafic contact but at the broader scale it transgresses the ultramafic and mafic units to the east and west respectively. The EMG is thought to have been emplaced in a regional shear zone striking at a slight angle to stratigraphy. To the west of the mine area the EMG is offset by a NNE-striking fault and to the east it wedges out. Gold mineralisation is associated with quartz veins and selvages of diopside-amphibole-biotite-silica with accompanying pyrrhotite, pyrite and lesser chalcopyrite, galena, molybdenite and sphalerite. The majority of gold reportedly occurs within the veins, with lesser amounts in alteration selvages. Two types of veins are noted. The more important type, in terms of historic gold production, comprises a series of stacked, arcuate (antiformal) veins that form splays from the footwall shear zone. There are seven principal veins that, stacked west to east, are known as the Western, Edna May Hangingwall, Edna May, South, Central, Middle and Consolidated reefs. Each of the reefs has a similar antiformal shape, comprising a thin (<1 metre) limb along the footwall contact, thickening (up to 6m) in the west-facing hinge zone and thinning again to a metre or less as it conforms to wallrock foliation towards the hangingwall contact. In detail, the reef geometries are more complex with individual limbs splitting, converging and traversing other veins. The thickened hinge zones were the focus of historic mining and historic mine plans indicate the WNW plunge persisting to at least 250m below surface.
The second type of quartz veining comprises swarms of thin sheeted quartz veins, ubiquitous throughout the EMG, that dominantly conform to the wallrock foliation but do, in places, cross-cut it to form stockworks. Individual veins are generally less than 5 centimetres thick but isolated veins reach several metres width in places and veining tends to be better developed in the footwall half of the EMG, around the reefs. A large laminated vein, termed the Hangingwall Reef, traverses intercalations of EMG and ultramafic rocks along the hangingwall contact. The reef, which attains a maximum true thickness of 12m, is better developed in the eastern portion of the mine area; in the west it has largely been stoped out by unmineralised pegmatite dykes. All the veins are sulphidic to some extent, with pyrrhotite being dominant in the reefs and galena more common in the sheeted veins and Hangingwall Reef. Ore minerals, in decreasing order of abundance, include pyrrhotite, pyrite, chalcopyrite, galena, molybdenite, sphalerite, scheelite and wolframite. Fine-grained pyrite and subordinate pyrrhotite, molybdenite and scheelite occur in disseminated form throughout the EMG. Alteration is dominated by a calc-silicate assemblage of diopside, calcic amphibole, biotite, K-feldspar, titanite, calcite and muscovite. Silicification is generally restricted to narrow selvages around individual quartz veins although in areas of intense veining these selvages may coalesce to form broader zones of silicification. Depth of oxidation varies from about 30m in the west of the resource area to 60m in the east. Top of fresh rock occurs at about 50m depth in the west and 60m to 70m in the east. An alluvial channel of presumed Tertiary age traverses the eastern end of the resource area from south to north. The channel is approximately 500m wide and reaches a maximum depth of 23m in the vicinity of the existing pit, broadening to the north. Fill material comprises a basal conglomerate overlain by a variably indurated series of quartz grits, sands and clays. Particulate gold, presumably of detrital origin, is concentrated in channel fill conglomerates near the base of the cover sequence. The entire sequence, including the palaeochannel fill, has been extensively lateritised to form characteristic ferruginous, mottled and pallid zones in the weathering profile. Mining The pit will be mined in four stages which have been designed based on three optimised gold price economic boundaries at A$600/ounce, A$800/ounce and A$1,250/ounce. The low strip ratio nature of the Edna May deposit allows the mine to employ a single mining fleet for most of the mine life. Catalpa’s first blast was fired on schedule, on Monday 14 December 2009, successfully removing a remnant overhang from the north face of the open-pit. Mining has commenced, and 24 hour mining operations were underway in November. In addition, stockpiling of high and low grade ore has commenced on the ROM pad. Processing The process plant design and flow sheet provide for a conventional carbon in leach (CIL) process and SABC FF (SAG mill Ball mill pebble Crusher Feed Forward) circuit. The ore has been extensively tested and found to be metallurgically consistent with a typical metallurgical recovery of approximately 92%. The process plant was purchased and transported from the Big Bell mine site to the Edna May site in 2007 with key plant components stored under cover in Perth. The process plant consists of a 2.0kW SAG mill and a 3.7kW Ball Mill along with other components necessary to reconstruct the plant As part of the plant upgrade to 2.8Mtpa the following changes to the flow sheet were designed:
The mine and processing schedule will allow average annual gold production of more than 100,000 ounces recovered. The process plant has a twelve month construction period which commenced in July 2009, with first gold production scheduled in mid 2010. Future Developments |
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