Por: Pedro Reyes Vivar, Raimondi Exploraciones.

Abstract

The iron oxide copper gold (IOCG) deposits are recognized in the western margin of the Andes between the 14th parallel in Peru and the coastal zone of Chile. In contrast, in the northern sector of the Peruvian coast, these deposits are not well identified, so the occurrence of these deposits is proposed, based on the identification of Cu, Au and Fe mineralization in the field, evidenced in (even) small but numerous mining operations. Also, although the definition of an IOCG system implies a wide range of (sub)types of deposits, a related tectonic framework has been recognized on the northern coast of Peru, associated with a Jurassic-Cretaceous alkaline to calc-alkaline magmatism, developed in a trans-Arc Cordilleran basin in an extensional regime (Polliand,2005). This environment has been identified in association with the Albian (113-110 Ma) Huarmey basin (Myers 1983). 

In this zone, copper mineralization comes from chalcopyrite, complementing bornite and secondary minerals, Au is in free state and as electrum inside chalcopyrite, pyrrhotite and magnetite mainly. Complementary pyrite (marcasite), hematite, molybdenite and actinolite, sericite, chlorite and clays occur as main gangue. Mineralization occurs in geometries of elongated bodies, veins and breccias, within (meta) volcanites of the Casma group and in intrusive rocks of the coastal batholith. The structures present a preferential orientation of 100º-120º, with variable dip from 30º to sub-vertical. 

As a result of recent investigations, where an association (at least spatially), between the occurrence of masses (>106 m3) of quartz, with the denomination of quartz "POD", with IOCG deposits (Lobo 2004) is proposed. These have been identified in at least 5 localities in the working area. This suggests the importance of this concept and its validity as a useful tool in the exploration of this type of deposit.

The mineralization tenors, in small mining operations, oscillate in the ranges of 10g/t Au-15 g/t Au @ 2% Cu, with variable contents of Ag and Mo. The mineralization potential is still unknown due to the size and limitations of these small mining operations. But by the number of occurrences and geometric projections of these in the field, it is considered important for the interest of medium (if not) large mining operations.