Regional Porphyry Systems
Porphyry copper-gold-molybdenum systems, and related skarn and epithermal gold systems, occur in Early to Late Jurassic intrusive and volcano-sedimentary rocks along the length of the Cordillera del Condor. Intrusive rocks of the Zamora Batholith host the porphyry deposits, skarn deposits occur in the older, intruded sedimentary rocks as well the overlying volcano-sedimentary rocks, and epithermal deposits are hosted by the volcano-sedimentary rocks. All these are overlain by Early Cretaceous sedimentary rocks.Several economic porphyry copper deposits (with significant gold or molybdenum) occur on the Ecuadorian side of the Cordillera del Condor in the Mirador District (Mirador, Mirador Norte, Panantza, and San Carlos deposits) to the north of Dorato's option properties. These deposits are classic calc-alkaline porphyries related to the emplacement of late-stage subvolcanic intrusive phases of the Zamora batholith.
The Mirador deposits contain a potassic core, variably overprinted by phyllic, which grades outward to a pyritic quartz-sericite and then propylitic alteration halo. Mineralization consists of pyrite-chalcopyrite stockwork and disseminated mineralization with local thin layers of supergene chalcocite enrichment. The deposits contain either significant molybdenum (60-250 ppm) or gold -- the total resource for the three main deposits contains 25 billion pounds of copper and 4.5 million ounces of gold. The deposits contain either significant molybdenum (60-250 ppm) or gold - the total resource for the four main deposits is estimated at 25 billion pounds of copper and 4.5 million ounces of gold.
To the south of Taricori and the Chinapintza District, El Hito and Santa Barbara represent two significant porphyry-epithermal systems. The deposits, currently poorly defined, have not been dated but are probably similar in age to the Corriente porphyries. The Cobrecon Sur mineralization appears to be the southeast extension of El Hito.
El Hito is a sub-economic porphyry system situated in Ecuador close to the Peruvian border, and contains copper mineralization in a quartz diorite to granodiorite stock that has intruded Piuntza volcanic rocks. There are several phases of stockwork veining associated with a central sericite-pyrite-clay alteration zone that grades outward to a propylitic halo. Mineralization in the inner core assays 0.1-0.3% copper with spot values of up to 0.9% copper. The porphyry system is approximately 2 km in diameter. In 2000, Valerie Gold drilled four diamond drillholes in the central part of the deposit in Ecuador, which returned intersections up to 300 meters long grading approximately 0.3% copper with minor gold.
Santa Barbara is a copper-gold porphyry-skarn deposit located in Ecuador, approximately 4 km west of El Hito. TVX Gold discovered the deposit in the mid- to late-1990's. The property was optioned to Valerie Gold (along with El Hito) in 1999 and later acquired by Goldmarca Resources (now Ecometals Ltd.). Mineralization consists of stockwork zones in altered porphyry and in skarn zones situated in a roof pendant of Misahualli volcanics. The deposit contains an inner phyllic-argillic-copper core with elevated levels of zinc and gold surrounded by a pyrite-propylitic alteration halo. Results of trenching and drilling by Valerie Gold indicate a potential resources of >700,000 oz Au (21 million tonnes @ approximately 1 g/t Au, 0.12% Cu).
