MUIRS REEF (100%)Exploration by Glass Earth Gold Limited (GEGL)at the Muir's Project in the Hauraki Goldfield in New Zealand's North Island has outlined an inferred resource of 5.24 Mt averaging 1.3 g/t gold using a 0.5 g/t gold cut off for a total of 219,000 ounces of gold. Gold as electrum occurs in mineralised low sulphidation style epithermal quartz veins. GEGL wholly owns the prospect and has focused on developing greater understanding of the economic potential of the mineralization at the site.
An NI 43-101 Technical Report has been compiled on the project and is available from Sedar, or the Technical Reports section.
The resource estimate is based on data from GEGL and historical data from BP Minerals and Mineral Resources New Zealand Ltd dating back to the 1980's. GEGL executed 24 trenches of 510m total length, 16 diamond drillholes of 3141.25m combined length, 2 RC drillholes of 463m combined length. The historical drilling comprises 12 diamond drillholes with a combined length of 1739m and 40 RC drillholes with a combined length of 3966m. Historical channel sampling includes 7 channel samples taken from surface and underground workings for a total of 253m combined length.
The reader is cautioned that the status of inferred resource reflects the relative confidence of the grade estimates and is based on several factors including sample spacing (both along strike and down dip), lack of quality assured data for historical drilling data, limited bulk density data, uncertainty over structural controls on mineralisation and sample quality. Furthermore, geological continuity has been assumed but not established. The resource has not yet been demonstrated as economically viable. There is also no certainty that it will be converted to a measured and indicated resource category through further drilling, or into a mineral reserve once economic considerations are applied.
Gold mineralised quartz veining in the andesite manifests as topographic highs at Muir's Reef and Massey Reef. As most of the project is covered by post-mineralisation ignimbrite there is potential to discover similar buried mineralised reefs. A seismic reflection survey or another geophysical technique should be considered to highlight lithological contrasts between ignimbrite cover and underlying older mineralised andesites rocks and faulting. If successful such a survey could greatly improve understanding of the sub surface geology and generate high quality drill targets.
Further drilling is recommended as the volume and grade of the inferred resource could be increased by exploratory drilling to test depth extensions to, and further infill drilling within, the presently known mineralisation. In addition to targeting further mineralisation loci, the drilling would seek to provide more reliable subsurface structural and density data. A proposed structural and petrographic programme is outlined before a decision to recommend a further 10,000m drill programme.
Channel Sample Program
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|Channel No||From||To||Interval m||Gold g/t||Silver g/t|
Glass Earth Gold is evaluating the Muirs gold prospect as it is an underexplored gold resource:
- the Muirs and Massey quartz reefs have hosted a producing gold mine which, through shallow open pitting and from three underground levels, achieved total production of 43,642 oz of gold until the 1930s;
- there have been several phases of more recent exploration over the Muirs system which provided encouraging results without providing a definitive understanding of the evident gold mineralization; and
- importantly, this advanced gold prospect lies just 65km southeast of Newmont Mining's Martha Mine at Waihi, located within the central Hauraki Goldfield area (see map)
Previous drilling and channel sampling work in the 1990s had returned interesting individual gold intercepts at the Muirs prospect (for instance channel sampling on surface returned 20 m @ 3.6 g/t Au). Encouraging rock chip samples and soil geochemistry indicated that two new potential vein systems enveloping the Muirs and Massey veins are gold mineralized.
The veins represent a highly typical epithermal gold system, with outcropping banded and colloform textured quartz veins, quartz breccia, and vein swarms mapped up to 20 m wide in the historical open pit. The host andesitic flows and pyroclastics are the southernmost extension of the Tertiary Volcanics of the Hauraki Goldfield which hosts the Martha Mine as well as the WKP West prospect.
Glass Earth Gold Exploration
Above: Laying cable for E-SCAN]
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Large scale E-SCAN(r) 3D resistivity surveys were conducted at Otawa and Gibraltar (respectively north and south of Muirs) in 2007, with follow up surface mapping and rock chip sampling. Rock chip sampling of outcrops returned individual results in the 0.5-3.0 g/t Au range. This work demonstrated that this epithermal gold prospect conjoins into one large continuous alteration and quartz veined system over 5000m in length, surrounding the historic Muirs Reef gold deposit.
In 2008 drilling of three deep diamond holes to test ground in and around the historic Muirs Reef deposit returned several gold intercepts, with the Massey Reef interpreted to be a sheeted vein system consisting of numerous banded quartz veins up to 5 m in width with interstitial stock work veining and brecciation, displaying extensive quartz veining and strong alteration and weathering throughout.
In 2009, gradient array resistivity profiling was undertaken over the Muirs prospect, with results suggesting a broader epithermal vein system west of the Muirs Reef veins. Data processing of the gradient array resistivity program was completed, with interpretation providing encouraging detail on subsurface geology and indicating the potential for several major new veins and extensions of existing veins. At this point our conclusions were that:
- a high-level epithermal gold system was indicated by the broad mineralized intersections in the three diamond drill holes, including 30 m @ 1.2 g/t Au and 6 g/t Ag, 16 m @ 1.1 g/t Au and 3.5 g/t Ag, within a broad zone of 37 m @ 0.8 g/t Au and 3.5 g/t Ag, confirming a mineralized system to 75m depth;
- additional gold mineralized quartz veins intersected either side of the broad intercepts indicate potential for a stockwork of veins between the Massey and Muirs vein systems;
- recent EM electrical ground surveying confirmed additional resistors indicative of new veins in the vicinity of Massey and Muirs quartz reef, and a potential new reef system east of Muirs quartz reef; and
- quartz vein petrology indicates a high-level epithermal system with unconstrained depth potential.
In late 2010 five drillholes completed a fence of drilling across the centre of the Muirs prospect, with the work program objective being to test geophysical/gold geochemical anomalies located parallel to, and along strike of, the Muirs and Massey Reefs. The objectives were only partially met, due to full sectional coverage not being achieved.
MSDDH05 (targeting the Muirs Reef in an untested central zone) intersected veining on the contact between andesite and volcaniclastic sediment, but with no economic mineralization detected, while MSDDH06 (targeting the western geophysical anomaly and coincident gold anomalous rock chips) encountered fresh unaltered andesite without significant alteration or veining, and accordingly the western target has been discounted as prospective.
Reverse circulation drilling testing the Eastern Vein target (MSRC01 and MSRC02), intersected hydrothermal clay-pyrite alteration with minor quartz veining. These drill holes terminated well short of their proposed depths, and while no gold mineralization was detected results indicate potential for parallel vein sets to the east of the Muirs/Massey vein system.
Above: Diamond drilling at the Muirs Reef project.
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MSDDH07 (drilled 440m south along strike of the Muirs Reef) was the most encouraging and insightful hole of the campaign. Drilled to test a strong resistor south along strike from Muirs Reef workings, MSDDH07 encountered strong hydrothermal alteration with all of the features associated with gold mineralization - including broad intervals of intense silicification, potassium-feldspar addition (adularia), frequent narrow quartz veining and high concentrations of iron sulfides (pyrite). Gold assays were sub-economic with the highest result being 0.41ppm gold over 1m from a hydrothermal breccia.
Accordingly this area to the south and west of Muirs Reef has significant potential. MSDDH07, while encountering anomalous mineralization, provided further encouragement due to the presence throughout of extensive veining and alteration. The hole terminated in mineralization and demonstrates a link to Massey Reef, where high gold grades have been detected at surface.
As encouragement was found in the detection of alteration and veining on the potential Eastern Vein target, and significant potential indicated to the South (where intense alteration and silicification was encountered over 300m south of the Muirs Reef, open both south and westwards), interest in the Muirs prospect has remained high and exploration work steadily continued.
Mr Simon Henderson, MSc Geology (CODES), an AusIMM Chartered Professional under the Discipline of Geology; is a Qualified Person as defined by National Instrument 43-101 and an employee of the Company, has reviewed and approved the technical information given above.