B2Gold holds its project interest through indirectly-owned subsidiaries. B2Gold has a 40% interest in Filminera and a 100% interest in Philippine Gold Processing & Refining Corporation (“PGPRC”). The remaining 60% interest in Filminera is held by a Philippines-registered company, Zoom Mineral Holdings Inc. (“Zoom”). Filminera owns the majority of the Masbate Gold Project tenements and is responsible for the mining, environmental, social and community relations on the Masbate Gold Project site. PGPRC developed and owns the process plant on the island of Masbate and is responsible for the sale of all gold.
Summary:
Masbate is considered to be an example of a low sulphidation epithermal gold deposit. The gold deposits that are currently being mined at Masbate are centred on a 5-7 km wide northwest- to south-east oriented mineralised volcanic block which is bounded by two interpreted northwest-trending fault zones. The mineralized system being mined in the open pit operations has a strike length of about 10 km, from Balete in the south to Pajo in the north. Mineralization has been tested to about 400 m depth.
The principal host rock to the gold mineralisation is a fractured andesitic–dacitic, tuffaceous agglomerate. Mineralisation occurs within quartz veins and associated altered and quartz-stockwork wall rocks and breccias. Gold is typically hosted in grey to white crystalline to chalcedonic quartz and is frequently associated with pyrite, marcasite, and minor amounts of chalcopyrite and sphalerite. HG veins are generally narrow (<1 m) but some may reach 20 m in width; sheeted stockwork zones can be up to 75 m in width.
The primary mineral associated with gold (+silver) mineralisation is quartz, both in the form of fracture-filling quartz veins and in the silicification of the host rocks. Calcite is a common vein mineral, but is generally present in smaller amounts, or is totally absent, in the oxidized ore.
The mineralizing system has a strike length of about 10 km, from Balete in the south to Pajo in the north. Mineralization has been tested to about 300 m depth with drilling; below this depth there is limited understanding of the mineralization extents.
The quartz and quartz–calcite vein systems can vary in thickness from 1–20 m, but can be considerably thicker in zones of structural complexity. For example, at the Main Vein, a broad zone of alteration or brecciation resulted in mineralised zones that were as much as 75 m wide. Quartz stockwork zones commonly associated with higher-grade veins display vein thicknesses that range from 1 cm to 10 cm in width.
Vein systems typically have distinct vein to wall-rock contacts, and limited development of alteration has occurred in the wall rocks. However, areas of stockwork can occur in the wall rock that result in a network of veinlets and pervasive alteration. Vein styles include fracture-filling quartz veins, well- developed stockwork zones, breccia pipes, and replacement of the host rocks.
Veins are generally grey–white in colour, display textures that range from massive to banded and include, in interpreted paragenetic sequence from oldest to youngest:
- Grey to blue-grey quartz veins;
- White cryptocrystalline and chalcedonic veins, commonly displaying calcite intergrowths;
- Calcite veins.
The primary sulphide is pyrite. Other sulphides include marcasite, chalcopyrite, galena and sphalerite. In oxidized units, goethite replaces the pyrite.
The main gold-bearing mineral is electrum. Electrum is typically observed as <10 µm inclusions within pyrite or goethite, or at the margins of pyrite and other sulphide phases. More rarely, gold can occur as free particles that may reach 500 µm in size. A small amount of the gold, based on tailings evaluations, may be hosted in silica. There may also be some minor gold hosted in tellurides, as elevated bismuth and tellurium contents have been reported from mineralized samples; no telluride minerals have been identified to date.
Silver content is variable, and is estimated at about 0.5–2 times the gold content. Silver assays are not currently done for exploration or grade control programs. Examination of the doré produced indicates about 40–45% silver content (Turner et al., 2012).