Masara District Revisited

Fernando G. Sajona

Geology Manager
Bunawan Mining Corporation

Consulting Geologist
Sierra Mining Corporation
Philippine Mineral Development Corporation

Abstract

The Masara mineral district has one of the densest distributions of mineral occurrence in the Philippines. At least 29 gold and copper-gold deposits and prospects are distributed within an area of 250 aerial km². Historic legitimate mineral operations in the area include those of North Davao Mining Corporation (NDMC) in the Amacan and Panuraon Cu deposits and the Hijo, Lost Horizon and Royal Flush gold deposits; and those of the Masara gold veins by the Apex Mining Corporation (AMC). The majority of the district is covered by mineral tenements and tenement applications of these two companies. The Masara mine is now operated by Crew Gold Corporation (CGC). NDMC is under receivership of the Philippine Government, through the Assets Privatization Trust (APT) and managed by the Philippine Mining Development Corporation (PMDC).

The district occurs within the Masara ridge, bounded by the Hijo and Maragusan valleys to the west and east, respectively. The ridge is underlain by Cretaceous-Paleogene metavolcanics that are overlain by Cretaceous limestone, Eocene clastics and carbonates and Miocene limestone. The axis of the ridge is intruded and truncated by a series of diorites, andesites and dacites. The most recent evidence of magmatic activity includes a 2,000 Ka maar diatreme structure, manifested by the Lake Leonard crater lake. Solfataric emanations and hot springs attest to a young and still active hydrothermal system.

Several mineralization styles are recognized within the Masara district:

Porphyry copper mineralization is most evident in the eastern central portion, where the previous Amacan copper mine is located, along with other prospects of the same nature (e.g., Piaminyan, Tarago, Tagbaros, Panuraon).
Most abundant are polymetallic quartz-base metal-gold veins, best exemplified by the Masara gold veins within the AMC property. Similar veins are present north (Goldsborpugh, Kantari) and south (Royal Flush, Lost Horizon, Magwandos, Dasuran) of the AMC area, falling within the NDMC tenement.
Gold deposits as replacements in calcareous rocks characterize the Hijo and Barrio mines and other prospects within limestone fringing the western flank of the Masara Ridge (e.g., Kay Fraction, RCO).
Replacement deposits in volcaniclastic rocks occur at the western flank of the Lake Leonard crater (e.g., Lumanggang).
Finally, mixed fracture filling and replacement mineralization (Sagay-Sagay, Anitapan, Umbrella, Shanghai) can be traced along continuous north-northwest- to northwest-trending structures from the west-central to the southern segment of the district.

Numerous northwest-striking faults related to the Philippine Fault transect the NDMC property. These faults are interpreted as tensional jogs that developed in relation to a sigmoid structure in the NDMC area. The intersections of these structures with northeast-trending faults often coincide with copper and gold mineralization. In addition, ring structures interpreted to be related to volcano-plutonic activity within the sigmoid structure are spatially related to mineralization, suggesting their likely genetic connection.

In terms of exploration, the Masara district offers one of the biggest potential in any single district. No comprehensive exploration has so far been conducted, except for those in the historic mines. Preparations by PMDC are underway for the bidding of rights to explore and develop the NDMC property.

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