Cu and Mo re-enrichment during ductile deformation: A case study of the Yuleken porphyry Cu deposit, Eastern Junggar, NW China

Abstract

Porphyry Cu deposits can be strongly deformed during subsequent tectonic evolution. To date, research pertaining to the deformation and the enrichment of mineralization in porphyry deposits has suffered from a paucity of proof. Here, we describe the diagnostic petrologic and geochemical signatures of the Yuleken porphyry Cu deposit from stages of metallogenic overprinting. The rocks studied in this work are from deformation-metallogenic structures that have (1) a distinguished metallogenic and tectonic evolution, (2) a three-layer, spatial, deformation-metallogenic structure, (3) distinguishably different fluid components within protomylonite, mylonite, and ultramylonite zones, and (4) variational geochemical characteristics of coexisting chalcopyrite and magnetite.Integrated sulfide and oxide mineral investigations pertaining to the mineral deformation and the trace element variation of the minerals chalcopyrite and magnetite in the Yuleken porphyry Cu deposit indicated that Cu and Mo can be enriched during ductile deformation through physical (analogous geochemical characteristics of chalcopyrite from different stages) and chemical migrations. The elemental variation of magnetite (magnetites from deformed stages have higher contents of Ti, V, Co, Mn, and Ga than those from other stages) and the variation of the fluid components within the protomylonite, mylonite, and ultramylonite zones reveal that the migration and precipitation of Cu, Mo, and Fe were influenced by oxygen fugacity, fluid components, and temperature variation. In conclusion, the arc-related porphyry deposits were able to become involved in the ductile deformation zone, inducing areas of Cu and Mo enrichment in theory. Units subjected to ductile deformation may have great potential for porphyry Cu (-Mo) deposit formation under the influence of magmatism.