Supplemental Material: Cambrian eclogite-facies metamorphism in the central Transantarctic Mountains, East Antarctica: extending the record of early Palaeozoic high-pressure metamorphism along the eastern Gondwanan margin

Supplementary material for Brown (2024), PhD thesis - Chapter 2 - Cambrian eclogite-facies metamorphism in the central Transantarctic Mountains, East Antarctica: extending the record of early Palaeozoic high-pressure metamorphism along the eastern Gondwanan margin

Figure S1. Mineral Liberation Analysis (MLA) image of sample 90-130D. Image obtained using an FEI Quanta MLA–600 scanning electron microscope. Modal proportions of all minerals were determined from this MLA image.

Figure S2. P–Mo section for sample 90-130D at a temperature of 730°C. The horizontal axis shows the proportion of X_Fe3+ from 0.04 (Mo=0) to 0.27 (Mo=1). Compositions for Mo=0 and Mo=1 are given in mol%. The bold dashed black line indicates the X_Fe3+ value determined from mineral EPMA analyses. Modal proportion and compositional isopleths are shown as dashed white lines. The peak assemblage is g + o + hb + ru + q + (H₂O/L).

Figure S3. P–M_H2O section for sample 90-130D at a temperature of 690°C. This temperature was chosen because it encompasses the inferred modelled peak field in the P–T pseudosection (Fig. 2.9a). The horizontal axis shows the proportion of X_H2O from 0.04 wt% (M_H2O=0) to 0.31 wt% (M_H2O=1). Compositions for M_H2O =0 and M_H2O=1 are given in mol%. The M_H2O=0 H₂O proportion corresponds to a dry composition calculated from amphibole inclusions in garnet and inferred peak amphibole. The M_H2O=1 H₂O proportion corresponds to a hydrous composition calculated from the total amount of amphibole in the sample. The bold dashed grey line indicates the solidus. The bold dashed red line borders the inferred modelled peak fields as show in the P–T pseudosection (Fig. 2.9a). Modal proportion and compositional isopleths (which are also calculated for the P–T pseudosection) are shown as dashed white lines.

Figure S4. 2σ uncertainties on mineral modal proportion isopleths from the P–T pseudosection for 90-130D. Uncertainties are represented as grey polygons encompassing the white dashed lines (mineral modal proportion isopleths). Uncertainties were calculated in THERMOCALC. A complete description of the mineral equilibria forward model is provided in Figure 2.9.

Table S1. Representative EPMA mineral compositions for sample 90-130D. Compositions labelled '(average)' and highlighted in grey are calculated from all EPMA compositions for a given mineral or mineral generation. These average compositions are used to calculate the bulk-rock composition for sample 90-130D. Average mineral compositions are used given the equilibrated nature of the minerals in sample 90-130D. The notation (i) signifies the mineral is included in garnet or clinopyroxene. Note: EPMA compositions of ap and gth are not given since these were not used in the bulk-rock composition calculation. Mineral abbreviations after Whitney and Evans (2010).

Table S2. LA–ICP–MS major and trace-element results for zircon. U-Pb isotope data is provided for zircon standards GJ, Plesovice and 91500. Trace-element data is provided for synthetic glass standard NIST-610. (bd) signifies below detection. Pb is Pb(208).

Table S3. LA–ICP–MS major and trace-element results for rutile. U-Pb isotope data is provided for rutile standards R10 and R19. Major and trace-element data is provided for synthetic glass standard NIST-610. (bd) signifies below detection. Pb is Pb(208).

Table S4. Approximate mineral modal proportions and calculated bulk-rock composition for 90-130D.