Mineralogical and fluid inclusion constraints on the genesis of gold-skarn deposits in the Nambija district (Ecuador)

摘要

The Nambija gold deposits are oxidized gold skarns developed on volcano-sedimentary rocks of the Triassic Piuntza Unit (southeastern Ecuador). A continuous process of skarn formation with a garnet-rich and pyroxene-poor prograde stage and gold deposition during a weak and sulfide poor retrograde stage has been recognized. Part of the late prograde and retrograde minerals (including native gold) are found in structurally-controlled irregular open spaces and veins (mainly along N10°E to N60°E directions). Gold precipitation is related to cooling of moderately saline fluids (2-11 wt% eq NaCl).