The deposit is principally hosted by a 900 m long by 400 m wide north-south striking intrusive stock complex composed largely of quartz diorite porphyry. The igneous rocks have intruded a thick sequence of andesitic volcanics and a basement of biotitequartz schists and mafic flows. The size, grade and mineralogy of the Guinaoang deposit are typical of porphyry copper deposits.

From 2011 the project was held under option by Gold Fields for a total exercise price of US$70m ($9.5m received by the company in payments). The option was not taken up as Gold Fields began new operations in Australia and all exploration data, including the high-grade, BR 60 drill hole undertaken during the option period, is now the property of Bezant.

Economic studies

In 2011 TWP Australia was commissioned by Bezant Resources PLC to undertake a Conceptual Study for the Mankayan Project in the Philippines. The Project was an undeveloped underground mine, for which a conceptual mining, extraction and processing method was to be determined. This study was conducted within the limits of accuracy of +35% to -30%. In 2014 GHD was commissioned to conduct a desktop review of the TWP report to update the capital and operating expenditure selected in the TWP report.

Snowden: JORC Compliant resource upgrade (as at July 2009)

  • Project return estimated (US$3.00/lb, Cu US$1,250/oz Au):
    • post-tax NPV of approximately US$739 million at an 8% discount rate
    • post-tax IRR of 21%
    • post-tax net cashflow of approximately US$3.7 billion
  • 20 million tonnes (“Mt”) per annum, block caving operation over an estimated 28 year mine life
  • Total capital investment cost of approximately US$1 billion over the duration of the project at 20 Mta and over 28 year mine life
  • US$17.31 costs per ore tonne, including all royalties, taxes, capital costs, equipment ownership, operating and processing costs and administrative and technical services costs


In June 2009 Snowden was requested by Bezant Resources Plc (Bezant) to generate an updated resource estimate for the Guinaoang copper-gold deposit (The Mankayan Project).

At the time of the Snowden resource report the Mankayan project has a 38 year history which includes being managed by a number of separate companies. The deposit had been tested by 55 drillholes mostly drilled to depths in excess of 900 m. However, the passage of time and many changes in ownership means that much of the past work, particularly prior to 1996, has often been poorly documented or is not documented at all.

From late 2007 to 2009 Bezant drilled a 9778 m programme (nine holes) along the full strike length of the deposit to test the validity of the historical drilling results and to provide samples for density and metallurgical analysis.

Snowden built a new resource block model for the Guinaoang deposit (June 2009) using geological and alteration interpretations provided by Bezant. Snowden interpreted the copper mineralisation envelope using a nominal 0.2% copper threshold. Mineralised volumes were estimated using block modeling while in situ density values were assigned to the model blocks based on assigning fixed (mean) values based on rock type derived core measurements. Copper and gold grades were estimated within the copper mineralisation envelope using ordinary block kriging. No Snowden resource geologists have been to site. The resource has been classified and reported in accordance with the 2004 Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (the JORC Code) using a 0.4% Cu cut-off. The Mineral Resource summary is listed below:

Gold Fields Drilling

Goldfields during their option period drilled an additional diamond drill hole, BC-60, representing longest hole drilled to date on the Mankayan Project with a total length of 1,491m. Hole BC-60 confirms ore body remains open at depth and increases previously known depth extent of the mineralisation on eastern part of the deposit by over 200m.