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Bolobolo Copper Prospect
Porphyry deposits in the Surigao District are controlled by the intersection of northeast to southwest-trending faults with north-northwest trending splays of the major Philippine Fault system. Due diligence work by Mindoro defined, amongst many other structural targets, one such structural intersection set in the Bolobolo area. A small ground reconnaissance program was carried out in 2005 to determine its potential significance.
Altered and mineralized float boulders and outcrop were located over a wide area at Bolobolo. Widespread propylitic alteration, characteristically the outer halo of a porphyry system, was defined in volcanics. Within this propylitic halo, outcrops and boulders of intense argillic, phyllic and calc-silicate alteration were located. Phyllic alteration (quartz-sericite-pyrite), which is characteristically proximal to the main mineralized core of porphyry systems, is intense, structurally controlled, and can be traced over three kilometers and observed up to 200 meters wide. A mineralized float boulder of calc-silicate located in a stream, contains abundant disseminations of chalcopyrite and bornite, as well as high-density quartz-bornite-magnetite veinlets.
A representative grab sample assayed 1.34 percent copper, 17.1 g/t silver. A float boulder of similar alteration and mineralization found in a stream, approximately 1.6 kilometers to the south, assayed 0.96 percent copper and 4.9 g/t silver.
In a third stream, approximately three kilometers to the northeast, a boulder of silicified limestone assaying 1.92 percent copper was also found. Calc-silicate mineralization characteristically occurs in limestone near Philippine porphyry copper-gold deposits.
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