CGA Mining Masbate Gold Mine, Philippines
The project is on the island of Masbate, about 350km south of the Philippines capital, Manila. It is a brownfield site with established infrastructure including an airstrip, dedicated jetty, roads, accommodation, offices, clubhouse, workshops, assay laboratory and bunker fuel tanks, all of which require various degrees of rehabilitation.
CGA acquired the mine in March 2007 and owns it indirectly through its 100% ownership of Philippine Gold Ltd, 40% of Filminera and 100% of Philippine Gold Processing & Refining Corp (PGPRC). The remaining 60% of Filminera is owned by a Philippines-registered company, Zoom Mineral Holdings Inc, in which CGA has a 40% interest.
CGA had taken a loan of $80.3m towards the development of the mine in 2008. The loan was granted by BNP Paribas at a repayment period of 4.5 years.
PGPRC is the developer and owner the process plant, and is be responsible for the sale of all gold.
The new 4Mtpa processing plant was constructed by Leighton Contractors at an estimated $178m. It was commissioned in February 2009.
Life of the mine is quoted at 9.5 years, with a payback period of 6.8 years.
On 14 April 2010, exploration drilling at the Masbate Gold Project began. On 12 April a new exploration license was granted to the project. The new permit extends 52.3km² and is contiguous to the tenements currently mined.
The Masbate gold deposits are centred on a northwest-to-southeast mineralised volcanic belt, 5–7km wide, which is bounded by two northwest-trending fault zones, the Pinanaan Fault to the east and the Malubi-Lanang-Balete Fault to the west. The volcanic belt occurs along the western flank of an earlier diorite intrusive. Gold is associated with the volcanic belt while copper is reported to occur within the diorite intrusive.
The principal host rock to the gold mineralisation is a fractured andesitic-dacitic, tuffaceous agglomerate. Mineralisation occurs in quartz veins within the agglomerate, and also within associated altered and quartz stockworked wall rocks and breccias. The gold is generally finely distributed, with a suggested grain size of 5–20 microns.
As of May 2008, the mine has 135.33Mt (0.96g/t) of indicated resources, including 127.15Mt (0.79g/t) of inferred resources. These figures reflect an increase of 62% from the time of acquisition. In the first year of operations (2009 - 10), the probable mining reserves were 3.03Moz of gold. This included total indicated resource base of 4.55Moz and inferred resources of 3.22Moz.
Production started in 2009 and the first gold was poured in May 2009. On 17 November 2009, a record daily production of 17,123t milled was achieved. Average annual gold production over the first eight years of the mine's life is forecast at 200,000oz/yr.
In the final quarter of 2010, the production was 50,330oz.
The total material movement requirement averages 16.5Mt over the life of the mine, with a maximum of just over 21Mt in year three and a minimum requirement of just under 12Mt in year five. To achieve this target the company says a peak mining fleet of three hydraulic excavators and 20 dump trucks will be needed.
Exploration drilling will be carried out until April 2011. It will include 55,000m of drilling and 15,000m trenching. Work in the initial stages will focus on proving up the inferred resources which currently stand at five million ounces. To do so, infill drilling will be carried out along the strike as well as the down dip of the existing reserves.
The process plant is a conventional carbon-in-leach (CIL) type facility consisting of primary crushing, two-stage grinding, leaching, adsorption and thickening process stages; elution, electrowinning and smelting gold recovery stages; and a cyanide detoxification stage treating process plant tails before disposal in a new tailings storage facility, being built 3km from the plant.
The mine is being developed by Leighton Contractors (Philippines) Inc, a wholly-owned subsidiary of Leighton Holdings Ltd of Australia. CGA originally had a six-year agreement with Leighton that covered the supply of all mining and earth-moving equipment, maintenance and personnel to mine the ore and associated waste material. This contract was renewed and extended to support the 2011 expansion programme.
Power is being supplied by three Sulzer units to provide a 32MW capacity on site. The units were chosen for reasons of lower operating costs (due to the efficiencies of the equipment) and to retain ownership of power supply from the start of operations. Poyry Energy was chosen to construct the power unit, which was commissioned in April 2009. The ongoing operations and maintenance are being undertaken by Wartsila Philippines.
Reclaim water recycled from the tailings storage facility provides the bulk of the process plant water supply. When this is not available, raw water is pumped from the existing Guinobatan River dam for general process use. Potable water is drawn from existing and new deep-well bores next to the river.
CGA plans to increase the mine output from the existing 6Mtpa to 6.5Mtpa in the first quarter of 2011. The company has already invested $15m on the expansion programme and also acquired an undisclosed stake in the Pajo property.
Pajo covers an area of 786ha and is located to the north of the Colorado pit on the Mastabe Gold Project. The company now has more than 18km of exploration tenements.