The sedimentary sequence has been extensively folded, thrusted and dissected by major faults. The structure is dominated by an anticline some 3 kilometres (km) long and 2 km wide. Intruding the sedimentary rocks are numerous dacitic dykes, stocks and sills that are typically altered to a phyllic hydrothermal assemblage (quartz-sericite-pyrite). Minor granodiorite is present some deep drill holes.
Precious metal mineralization at Igor consists of a series of veins, breccias and mantos principally with a north to south orientation, although secondary north-east to south-west and north-west to south-east trends are also important. Gold and silver are the most important metals. Geochemically, arsenic and antimony commonly accompany precious metal mineralization. Weak localized base metal (lead and zinc) mineralization is also present. Copper grades are generally low, but frequently increase with depth, especially in the Portachuelos area. Oxidation, especially along structures, is pervasive and commonly extends to depths of several hundred metres. Gold and silver mineralization appears to bel ow to Intermediate sulphidation epithermal in character and there are indications of a deep porphyry copper gold system underlying the Igor District.
IGOR contains a district scale hydrothermal system with four principal gold and silver mineralized areas of deposits: