Devolatilization of metabasic rocks during greenschist–amphibolite facies metamorphism

Abstract

AbstractThe production of large volumes of fluid from metabasic rocks, particularly in greenstone terranes heated across the greenschist–amphibolite facies transition, is widely accepted yet poorly characterized. The presence of carbonate minerals in such rocks, commonly as a consequence of sea‐floor alteration, has a strong influence, via fluid‐rock buffering, on the mineral equilibria evolution and fluid composition. Mineral equilibria modelling of metabasic rocks in the system Na2O‐CaO‐FeO‐MgO‐Al2O3‐SiO2‐CO2‐H2O (NCaFMASCH) is used to constrain the stability of common metabasic assemblages. Calculated buffering paths on T–XCO2 pseudosections, illustrate the evolution of greenstone terrane..