The San Cristobal gold district is located 110 km east of the port of Antofagasta, Chile. It contains the San Cristobal gold
mine, where Niugini Mining Ltd. commenced a heap leach operation, with initial reserves of 10.1 million tonnes grading
1.34 g/t An, in December, 1990. The San Cristobal district occurs within an upper Cretaceous-lower Tertiary magmatic
arc. The main mineralisation occurs within a northwest trending subvertical zone, 1km long and 70-100 m wide, which
contains rhyolite porphyry and minor breccia, and is locally termed the "subvolcanic complex". At the San Cristobal
mine, most gold mineralisation occurs in subvertical quartz-pyrite veins which were emplaced in dilational sections of an
imbricate fault system. The bulk gold resource comprises four ore shoots which formed where the vein system intersects
the subvolcanic complex. Gold-bearing quartz-pyrite veins also occur at separate prospects, the Three Sisters and Sol
prospects, west and south of the San Cristobal mine. Hydrothermal alteration consists of potassic and propylitic
assemblages related to intrusion of the subvolcanic complex. This alteration is overprinted by a phyllic stage which is
associated with the emplacement of the quartz-pyrite veins. The oxide zone is 180 m thick, and contains native gold,
electrum, limonite, and manganocarbonates. The underlying hypogene zone contains pyrite with minor chalcopyrite,
sphalerite, galena, covellite, bornite, chalcocite, and arsenopyrite. Fluid inclusion studies indicate that the deposit formed
at approximately 270 C, and the mean salinity of the fluid was 4% NaCl equivalent. These observations enable the San
Cristobal deposit to be classed as a porphyry-related, mesothermal quartz-vein system of the low sulphidation type.