Deep-seated fluid involvement in ductile-brittle deformation and mineralization, South Mountains metamorphic core complex, Arizona

In the South Mountains metamorphic core complex of central Arizona, a middle Tertiary pluton exhibits the entire spectrum of ductile-to-brittle structures characteristic of metamorphic core complexes. Apart from minor Cu-enrichments in brecciated samples, original major- and minor-element abundances of the deformed igneous rocks are remarkably undisturbed, and there is little correspondence between chemical composition and deformational state. Fluids present during the entire history of ductile-to-brittle deformation were apparently close to chemical and oxygen-hydrogen-isotope equilibrium with the rocks. The temporal association of deformation with Tertiary plutonism and the evidence for high-temperature fluid/rock near-equilibrium support the interpretation that the fluids were expelled from differentiated, late crystallizing portions of the South Mountains plutonic complex. -from Authors