Japan Oil, Gas and Metals National Corporation (JOGMEC) and Tenke Mining Corp., which is now NGEx Resources Inc. (NGEx), jointly began the Vicuña exploration project, Vicuña JV, in November, 2004. The Vicuña JV project area is located in the Andean Cordillera straddling the border between Chile and Argentina with 240 km
2 area coverage. The Area has been considered to be highly prospective for porphyry copper-gold discoveries but sufficient exploration activities were not conducted.
In the Los Helados area situated in the Chilean side of the Vicuña JV project area, due to the lack of drilling work in the past, the distribution of alteration was only recognized at the time when JOGMEC entered the Vicuña JV in 2004. However, in February 2007, we began the drilling campaign after conducting geological mapping, geochemical, and geophysical exploration programs, totaling 18,000m in length 32 holes completed by June, 2011. As a result, we intercepted the mineralization that led to the discovery of what is believed to be a major porphyry copper-gold system. The copper-gold mineralized zone in Los Helados was formed by mineralization related to a dacite porphyry stock. It is also characterized by significant copper-gold mineralization generated in a hydrothermal breccia system. What porphyry copper-gold deposits have in common is the telescopic development of advanced argillic alteration, sericite alteration, intermediate argillic alteration, and potassic alteration, which spread from the surface to the underground area. Re-Os age dating of separated molybdenite from B type vein give date of 13.13+/-0.32Ma, similar to the age of the porphyry copper-gold systems in the eastern Maricunga subbelt.
Grassroots exploration in Los Helados began with geological mapping targeting the alteration identified by satellite image analysis, and after 7 years of exploration, it resulted in the discovery of a potentially significant porphyry copper-gold deposit. It can be pointed out that the following four major factors played important roles in our success in the early-stage exploration: identification of alteration through ASTER satellite image analysis, review of geological models at the drilling stage, prediction of rich mineralization using updated information, and flexible revision of the drilling plan as new results became available.
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