- Narrow Vein Mining
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The Tambis Project, containing the Bananghilig Gold Deposit as shown on Figure 1, is operated under a Mining Agreement with Philex Gold Philippines Inc. over Mineral Production Sharing Agreement (“MPSA”) 344-2010-XIII which covers 6,262 hectares.
The area has been known as an alluvial gold producing area since Spanish times. The first modern exploration pre-Medusa group was conducted in the 1970s followed by further work in the 1990s. The Company commenced a concerted effort in July 2010 and drilling prior to this is summarised in Table 1.
Table 1: Summary of the historical drilling statistics for Tambis-Bananghilig Project area
On 28 August 2012, Cube Consulting Pty Ltd estimated a new Inferred Resources for the deposit based on all available drilling as at 31 July 2012 including 74,522 metres of new drilling in 235 holes.
Additional recent regional geological and mineralisation information is contained in the 2012 announcements dated 10 May 2011, 12 September 2011, 17 January 2012 and 28 August 2012.
In July 2010, new regional and detailed mapping and drilling programmes were commenced with the aim of validating the current resource and extending it to provide a reserve of approximately 1,000,000 ounces. This reserve would form the basis for a feasibility study which would target production centre.
On 28 August, 2012, Cube consulting Pty Ltd estimated a new estimate resource for the deposit based on all available drilling as at 31 July 2012 including 74,522 metres of new drilling in 235 holes.
A Scoping study was published on 9 April 2013.
Regional Geology Setting
The Tambis regional geology, termed the Tambis intrusive-breccia complex, typifies a structurally complex intermediate-sulphidation, epithermal gold, breccia-type system, including disseminated gold overprinting the host Tertiary-age igneous package which had been emplaced into an andesitic volcanic basement. The fertile igneous suite comprises a multi-phase calc-alkaline, high level, sub-volcanic intrusive package cut by extensive bodies of phreatomagmaticdiatremes and hydrothermal breccias.
Laboratory studies including fluid inclusions have indicated that the Tambis area is only shallowly eroded with an estimated 500 to 950 metres of material stripped from the original surface.
The Tambis intrusive-breccia complex is overlain by younger marine limestones and basal mudstones to the south and the east. The extent of the complex below this younger cover is yet to be determined.
BANANGHILIG DEPOSIT DESCRIPTION AND MINERALISATION
Figure 2 shows the Bananghilig Deposit and the B2 Discovery area.
Figure 1: Tenement location map showing the mines and prospects.
Deposit Geology and Mineralisation
The Bananghilig Deposit (Figure 2) is located partly within diatreme breccias which measure at least 1,000 metres west to east and still open to the south beneath the younger sediments, and also around the diatreme margins and in the country rocks along structural corridors.
The diatreme breccias contain unsorted fragments of the andesitic basement as well as fragments of the later intrusive rocks predating the diatreme events in a matrix of comminuted rock flour and magmatic crystals. Fragment sizes range from granule-sized to building-sized mega-blocks which have been torn off the walls of the diatreme during the multi-episodal explosive activity. The explosive activity also fractured the mega-blocks and wall rocks, preparing them for subsequent mineralisation deposition. The cross-section in Figure 3 shows several of the mega-blocks which are the same composition as the wall rocks in this area.
After the diatreme formation, several events of hydraulic fracturing, hydrothermal and fault brecciation, rock alteration, quartz veining and precious- and base-metal mineralisation occurred. Based on mineral associations and fluid inclusion results, the main gold deposition event appears to have occurred following multiple hydrothermal fracturing along the margins of, and within the diatreme complex. High gold concentrations appear to be associated with elevated Ag and base metals.
The gold mineralisation style (+Ag ±Zn ±Cu ±Pb) is classified as an intermediate sulphidation epithermal system. In and immediately adjacent to the diatreme, the gold mineralisation generally occurs in vein-like zones, in fractures and/or breccia in-fill in milled/fluidised muddy matrix breccia bodies and coarsely brecciated/fractured andesitic-dacitic wallrock.
Breccia veins in the deposit exhibit epithermal mineral growth textures and in particular are related to retrograde boiling of the mineralizing fluids. Major hydrothermal breccia veins are sub-vertical to steeply dipping, averaging one metre thick, and form anastomosing pinch-and-swell patterns up to several hundred meters along strike. They are commonly offset in many places by post-mineralisation faults. Down dip continuity of breccia vein mineralisation has been demonstrated to persist down to 500 meters from surface. The breccia veins generally form a northeast-trending sub-parallel array with minor north-south and east-west trends.
Widespread silica-illite-pyrite hydrothermal alteration affects the volcanic wallrocks, the various breccia bodies and the hypabyssal intrusives associated with them. The pervasive near-surface argillic alteration haloes grade laterally and vertically at depth into chloritic and propylitic alteration assemblages.
Detailed drilling results are contained in announcements dated 12 September 2011, 17 January, 28 August 2012, 21 November 2012, 07 January 2013, 02 April 2013, 08 July 2013, 08 August 2013 and December 2013 , March 2014, June 0214, September 2014 Quarterly Reports.
Drilling was completed in July 2014.
On 2 April 2013, the results of the sterilisation drilling were announced showing widespread gold mineralisation at the site first chosen for the mill (figs 4 & 5). An alternative mill site is now being investigated.