Hydration of eclogite, Pam Peninsula, New Caledonia

Garnet glaucophanite and greenschist facies assemblages were formed by the recrystallization of barroisite-bearing eclogite facies metabasites in nort hern New Caledonia. The mineralogical evolution can be modelled by calculat ed P-T and P-X-H2O diagrams for appropriate bulk rock compositions in the m odel system CaO-Na2O-FeO-MgO-Al2O3-SiO2-H2O. The eclogites, having develope d in a clockwise P-T path that reached P approximate to 19 kbar and T appro ximate to 590 degrees C, underwent decompression with the consumption of fr ee H2O as the volume of hydrous minerals increased. Eclogite is preserved i n domains that experienced no fluid influx following the loss of this fluid . Garnet glaucophanite formed at P approximate to 16 kbar during semi-perva sive fluid influx. Fluid influx, after further isothermal decompression, wa s focused in shear zones, and resulted in chlorite-albite-bearing greenschi st facies mineral assemblages that reflect P approximate to 9 kbar.