Fig. 3: Representative photomicrographs, hyperspectral confocal Raman maps and two type fluid inclusions in carbonated eclogite sample HB142-1 showing immiscible H2O–CH4 fluids in the Western Tianshan subduction zone.
From: Immiscible metamorphic water and methane fluids preserved in carbonated eclogite
a A large number of fluid inclusions observed in actinolite. The fluid inclusions grow along their long-axis directions. b Enlarged image showing numerous fluid inclusions with oriented distribution in retrograde amphibole (Amp). The fluid inclusions can be divided into Type-1 and Type-2 fluids. c Ankerite (Ank) and actinolite (Act) porphyroblasts are in equilibrium, and Ank is cut by paragonite (Pg). d Enlarged images showing the presence of fluid inclusions in actinolite (Act). e, f Hyperspectral confocal Raman maps showing the presence of CH4 in fluid inclusions in the Ank core and Act, whose locations marked in squares in (c) and (d). g–j Representative images and the corresponding sketches showing the presence of two types CH4-rich fluid inclusions in Ank and Act, respectively. k The coexistence of Type-1 of H2O-rich fluid inclusions and Type-2 of CH4-rich fluid inclusions in garnet (Grt) mantle. l Symbiotic fluid inclusions had significantly different ratios of CH4/H2O in the rim of omphacite (Omp). The insert enlarged images show the Type-1 and Type-2 fluid inclusions. The coexistence of Type-1 and Type-2 fluid inclusions demonstrates that immiscible fluid phases must have occurred during HP metamorphism.
