Gold-rich VHMS deposits of the Western Cordillera of Ecuador: mineralogy, lead isotope and metal geochemistry

Resumen

The Western Cordillera of Ecuador hosts three Au-rich Cu-Zn YHMS deposits within an EarlyTertiary island arc sequence, now accreted to the continent. The deposits are characterized by pyrite-chalcopyrite mineral parageneses including bornite, covellite, digenite, tennantite, and are affected bya quartz-sericite alteration. Lead isotope compositions are homogeneous within each deposit but differsignificantly among the three orebodies, even if two of them are only l.5 km apart. Lead isotopecompositions of the orebodies overlap those of the volcanic host rocks and are consistent with leadderived from mixing of pelagic sediments, mantle and oceanic crust. Geological setting mineralogy,and gold grades of the VHMS depos its of the Western Cordillera of Ecuador bear some similarities to those of recent and present-day massive sulphides of the western Pacific.those of recent and present-day massive sulphides of the western Pacific.