If you are doing geochemical soil or stream silt sampling, copper is the best pathfinder element but beware of glacial cover, which may mask the geochemical response. Deposits in the Cordillera are mainly of Triassic to Jurassic or Tertiary age. Some of the older ones occur entirely within the granitic host rocks, most are in both the qranitic body and the enclosing country rock. Porphyry-type mineral deposits result when large amounts of hot water that carry small amounts of metals pass through permeable rocks and deposit the metals. Often there is early development of a wide area of secondary biotite that gives the rock a distinctive brownish colour.
Gold is often in native found as tiny blobs along borders of sulphide crystals.
Molybdenite distribution is variable, Radial fracture zones outside the pyrite halo may contain lead-zinc veins with gold and silver values. Not all stages develop fully, nor are all the stages of equal importance. Various factors, such as magma type, volatile content, the number, size, timing and depth of emplacement of mineralizing porphyry plutons, variations in country rock composition and fracturing, all combine to ensure a wide variety of detail. As well, the rate of fluid mixing, density contrasts in the fluids, and pressure and temperature gradients influence the end result. Different depths of erosion alone can produce a wide range in appearances even in the same deposit.