title: Why large porphyry Cu deposits like high Sr/Y magmas?
abstract: Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is essential to develop genetic models that can be used for exploration purposes. Here we present results on a Pleistocene volcano of Ecuador that highlight the behaviour of copper in magmas with variable (but generally high) Sr/Y values. We provide indirect evidence for Cu partitioning into a fluid phase exsolved at depths of ~15 km from high Sr/Y (>70) andesitic magmas before sulphide saturation. This lends support to the hypothesis that large amounts of Cu- and S-bearing fluids can be accumulated into and released from a long-lived high Sr/Y deep andesitic reservoir to a shallower magmatic-hydrothermal system with the potential of generating large porphyry-type deposits.
authors.affiliation: Section of Earth and Environmental Sciences, University of Geneva , 1205 Geneva, Switzerland. Massimo.Chiaradia@unige.ch
authors.forename: Massimo
authors.initials: M
authors.lastname: Chiaradia
authors.forename: Alexey
authors.initials: A
authors.lastname: Ulianov
authors.forename: Kalin
authors.initials: K
authors.lastname: Kouzmanov
authors.forename: Bernardo
authors.initials: B
authors.lastname: Beate
mesh_terms: D003300:Copper / Q000737:chemistry*; D018534:Earth, Planet; D004484:Ecuador; D019418:Evolution, Chemical; D055593:Geological Phenomena; D008094:Lithium / Q000737:chemistry; D013440:Sulfides
chemical_list: D013440:Sulfides; D003300:Copper; D008094:Lithium