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Table 2 Intervals of compositional variations in minerals marking different metamorphic stages of garnet-bearing gneiss

From: Blueschist mylonitic zones accommodating syn-subduction exhumation of deeply buried continental crust: the example of the Rocca Canavese Thrust Sheets Unit (Sesia–Lanzo Zone, Italian Western Alps)

Mineral pre-1a pre-1b M1 M2
Grt Mg = 0.28–0.56 Mg = 0.09–0.28 Mg = 0.03–0.08 Mg = 0.02–0.04
  Fe2+ = 2.02–2.31 Fe2+ = 2.24–2.51 Fe2+ =1.37–1.67 Fe2+ = 1.18–1.53
  Fe3+ = 0.00–0.07 Fe3+ = 0.01–0.07 Fe3+ =0.00–0.08 Fe3+ = 0.00–0.10
  Ca = 0.08–0.22 Ca = 0.09–0.31 Ca = 1.08–1.40 Ca = 1.24–1.48
  Mn = 0.15–0.34 Mn = 0.22–0.36 Mn = 0.09–0.28 Mn = 0.12–0.31
Jd/Cpx    XJd = 0.84–0.97  
    Na = 0.89–0.98  
    Fe = 0.00–0.05  
    Ca = 0.01–0.04  
    Mg = 0.00–0.03  
Wm Si = 3.07–3.07   Si = 3.37–3.58 Si = 3.35–3.52
  Altot = 2.85–2.85   Altot = 1.88–2.23 Altot = 2.02–2.25
  Ti = 0.02–0.02   Ti = 0.00–0.01 Ti = 0.00–0.01
  Mg = 0.04–0.05   Mg = 0.24–0.30 Mg = 0.23–0.30
Ep    Fe3+ =0.38–0.65 Fe3+ =0.33–0.52
    Altot = 2.36–2.64 Altot = 2.47–2.7
    Mn = 0.00–0.01 Mn = 0.00–0.01
Gln     Na = 1.88–1.96
     Altot = 1.77–1.93
     Fe2+=1.58–2.04
Pl     XAb = 0.93–0.96
     XAn = 0.02–0.06
     XOr = 0.01–0.03