Medusa Mining Limited (TSX:MLL)(ASX:MML), through its Philippines operating company Philsaga Mining Corporation, announces an update of the Co-O Mine surface drilling results for previous hole MD 259 and new holes MD 261 to MD 279, results from underground drilling and an update on regional drilling around the Co-O Mine.
The Royal Vein set is now being delineated by drilling and development along the northern side of the Co-O Mine resource model and has been extended westwards to the Tinago Shaft.
A new vein set named the North Tinago Veins and located to the north of the Royal Vein set is currently being delineated on surface following initial drill intersections of up to 2.90 metres at 8.08 g/t gold, and on a different vein, 1.00 metre at 29.53 g/t gold.
Geoff Davis, Managing Director of Medusa, commented:
"The Co-O Vein system continues to grow, as evidenced by the recognition and delineation of the North Tinago Vein set. Drilling of the Royal Vein set indicates they start at shallow depths and extend the full distance along the north side of the mine resource model from east of the Saga Shaft westward to the Tinago Shaft area, although infill drilling and development is on-going to confirm this interpretation.
In addition, surface work is delineating new veins at West Tinago and the vein system at Gamuton is shaping up to be more extensive than previously thought. These will be systematically drilled to determine their potential.
These new discoveries have the potential to significantly increase the mining area."
Co-O MINE DRILLING
Discussion
Following the announcement of the discovery of additional Royal Veins on 30 June 2010, a further set of veins, the North Tinago vein set, has been recognised to the north of the Royal Vein set and is being delineated by surface mapping and trenching work and by on-going drilling.
Drill results
Previous reports were published for holes numbered MD 241 to 260 on 30 June 2010, for MD 217 to 240 on 29 March 2010, for holes below MD 217 on 18 January 2010, 1 July 2009, 1 December 2008 and 12 August 2008. In 2007 the announcements are dated 9 July, 15 May and 28 February.
Results down to 0.2 metres wide are reported since underground development shows that in many cases as the veins approach cross-cutting faults, they narrow down on both sides of the fault over 5 to 10 metres before widening out, and hence the narrower intersections are important in defining vein continuity. There is also some pinching and swelling of veins along strike. Most drilling is sub-parallel to the fault direction and rarely intersects the faults, which are subsequently identified by underground on-vein development.
Drill hole collar positions are surveyed by a qualified surveyor and surface drill holes are surveyed downhole at regular intervals using a digital multi-shot downhole camera.
It is important to note that the drilling of narrow epithermal veins generally provides an indication of the presence of the gold mineralised vein but may not always provide good quantitative data with respect to accurate grade and volume estimations for some or all of the following reasons:
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Veins commonly pinch and swell and may be brecciated or displaced by faults;
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Gold distribution may be erratic, and
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Drill core recovery may be reduced because of the brecciation and soft unconsolidated material and hence the recovered material may not be representative of the material drilled.
Consequently, the Company regards the initial drilling as indicative only and operates the policy of using drilling to locate the position and extent of the mineralised veins. This is then followed by on-vein development to support the drilling results, and to provide a more accurate estimate of vein grades and which results in the upgrading of the resource category from Inferred to Indicated. The development supports the estimation of resources and facilitates the conversion of resources to reserves.
Co-O REGIONAL DRILLING
Using the Co-O Mine as a model, drill testing commenced in the September quarter of 2009 on veins in the vicinity of the Co-O Mine.
The Co-O vein system Central Vein outcrops at surface on the western side of the Oriental Fault, where it was first discovered. The veins at surface rarely exceed 0.5 metres width and generally assay around 1 to 5 g/t gold (with possibly some supergene enrichment which is an increased concentration of minerals due to weathering of the near surface mineralisation). Gold values on the Central Vein start to increase significantly approximately 80 metres below surface.
It should also be noted that the drilling in the late 1980s and early 1990s to locate the veins east of the Oriental Fault intersected clay - minor silica alteration zones up dip from the high grade veins, and returned assays up to 1 g/t gold which were considered inconsequential at the time. Hence the Company carefully evaluates the importance of low assays in geologically favourable settings.
Results for EXP 001 to 012 were announced on 17 December 2009, an update up to EXP 022 was provided on 19 March 2010, and results for holes EXP 022 to 028 were provided on 30 June 2010. A total of 6935.9 metres have been completed in the nine holes EXP 029 to 037. Assays are awaited for EXP 036 and below 381 metres in EXP 037.
DISCUSSION
The results from EXP034 and 035 indicate the presence of multiple veins in this vicinity at depth, and to date two of these appear to have been located on surface, being NT 1 and NT 2. Surface mapping and trenching is now being used to track the veins on surface and to target delineation drilling.
Veins NT 3A, 3B and NT 4 to the southeast are also being delineated by surface trenching and mapping in preparation for further drilling.
Hole EXP 037 appears to have intersected a well mineralised, possibly northwest-trending vein.
The Royal Vein set is now interpreted to extend along the entire length of the northern side of the current vein resource model. Importantly they appear to start at shallow depths (and may indeed outcrop or subcrop below the soil horizon) as indicated by numerous shallow drill hole intersections in holes MD 264, 267, 272 and 275, development on Level 3 at the eastern end of the mine and recently commenced development from the Tinago Shaft end on Level 1, heading eastwards.
The recognition of the continuity of the Royal Vein set and the new North Tinago Vein set adds considerable potential for the mine to expand the underground workings further to the north of the current operations, initially at shallow depths.
ON-GOING DRILL PROGRAMME
Two to three surface rigs will continue drilling on the Co-O Mine and two to three rigs will continue regional drilling. Four drill rigs are operating underground.
DRILL HOLE SAMPLING AND ASSAYING PROCEDURES
Samples were taken from mainly HQ sized (hole outside diameter 96mm, hole inside diameter 63.5mm) and some NQ sized (hole outside diameter 75.8mm, hold inside diameter 47.6mm) drill core. The selected sample intervals were halved by diamond saw and half the core was bagged, numbered and sent to the Company laboratory. In a small number of cases to confirm the geological logging, the selected interval was re-split and ¼ core re-submitted for assay.
Initial sample preparation and assaying was undertaken at the Company's on–site laboratory. Samples were dried at 105ºC for 6 to 8 hours, crushed to less than 1.25 cm by jaw crusher, re-crushed to less than 3 mm using a secondary crusher followed by ring grinding of 700 to 800 grams of sample to nominal particle size of less than 200 mesh. Barren rock wash is used between samples in the preparation equipment. The samples were assayed by fire assay with Atomic Absorption Spectrometer (AAS) finish on a 30 gram sample. All assays over 5 g/t gold were re-assayed using gravimetric fire assay techniques on a 30 gram sample.
Check assaying of the majority of samples used in the resource estimate update and which contain more than 0.5 metres at more than 2 g/t gold have been undertaken by McPhar Geoservices Phils Inc ("McPhar"), a NATA and ISO 9001/2000 accredited laboratory in Manila. The pulps were airfreighted to McPhar who fire assayed 30 grams of sample using AAS finish and a selected number of samples were checked using gravimetric fire assay techniques. Duplicate samples and standards are included in each batch of check samples.
When reporting results, where available, the assays of McPhar as an independent laboratory have been given priority over the Company laboratory's results.
Information in this report relating to Exploration Results has been reviewed and is based on information compiled by Mr Geoff Davis, who is a member of The Australian Institute of Geoscientists. Mr Davis is the Managing Director of Medusa Mining Limited and has sufficient experience which is relevant to the style of mineralisation and type of deposits under consideration and to the activity which he is undertaking to qualify as a "Competent Person" as defined in the 2004 Edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves" and is a "Qualified Person" as defined in "National Instrument 43-101" of the Canadian Securities Administrators. Mr Davis consents to the inclusion in the report of the matters based on his information in the form and context in which it appears.
Source: Medusa Mining Limited