Abstract
The Mamut porphyry copper deposit of Paleocene to upper Miocene age is located on the northern end of the island of Borneo. The ore deposit is one of many mineralized centers which occur within and along a northwest-southeast-trending tectonic zone in the state of Sabah, Malaysia. Copper mineralization is associated with a potash-rich adamellite porphyry intrusion and is localized in the intrusion as well as in the wall rocks. The wall rocks consist of serpentinite and a sequence of clastic sedimentary rocks. Volcanic rocks are sparse and are represented only by very thin beds of tuff within the preore clastic rock sequence.Mamut is a copper-gold deposit with a total ore reserve of 179 million tons of 0.476 percent copper and about 0.5 grams per ton of gold. The ore mineral assemblage is dominantly chalcopyrite with minor molybdenite and sparse galena and sphalerite. Mamut is unusual because both pyrrhotite and pyrite occur as gangue sulfides. Ore-related alteration is characterized by strong silicification and the development of biotite, both of which occur within the ore shell. Quartz-sericite alteration with veins is commonly observed.
