The Alpine structural and metamorphic evolution of the Ivozio complex is reported in Fig. 7. The evolution is characterized by a multistage structural and metamorphic re-equilibration during Alpine time:
a) the D1 deformation phase represents the relic of the prograde history and is characterized by the development of a penetrative foliation within most of the rocks. D1 developed at T 500°C at depths below 30 km, in the epidote-blueschists facies conditions. P/T and T/Depth ratios are respectively 2.5*10-3GPa°C-1 and 13°Ckm-1 showing that the during burial of Ivozio complex at depth, the thermal regime was compatible with cold oceanic lithosphere subduction.
b) Post-D1a stage is characterized by the static growth of Omp and Lws in eclogites. During this stage temperatures were 520 ± 30°C at depths from ≍ 50 to 70 km. The post-D1a evolution completely developed under eclogite facies conditions and P/T was 4*10-3GPa°C-1, while T/Depth 8°Ckm-1. During this P-prograde stage the thermal regime is lower, if compared with D1.
c) During the post-D1b stage the eclogite facies metamorphic association of Omp + Ky + Ep (in Lws-eclogites) was stable at P above 2.0 GPa and T = 610 ± 20°C. P/T ratio was 3*10-3GPa°C-1 while T/Depth 8°C km-1. Ex-Lws pseudomorphs consists of Omp + Ky. This re-equilibration stage testifies a slight increase in T/P ratio, attaining at this stage the higher P conditions.
d) During D2 a penetrative foliation underlined by eclogites facies association (e.g. Omp + Wm + Amp + Ep in eclogites and Amp-schists) developed. During this stage Ky-Ep pseudomorphic replacement of Lws is substituted by Pg + Ep. In ultramafics and serpentinites S2 is the widespread planar fabric and is underlined by Srp + Chl + Amp ± Ilm ± Cpx ± Carb ± Tlc. This stage is characterized by T = 550 ± 50°C at depths from 48 to 70 km. P/T ratios were between 2 up to 4*10-3GPa/°C and T/Depth ratios 12°C/km, testifying that during decompression the thermal regime is still low.
e) D3 took place under greenschists facies conditions and corresponds to the local development of a crenulation cleavage or to discrete shear bands; in low strain domains, newly grown corona aggregates are contemporaneous with syn-D3 mineral growth in foliated rocks. During D3 temperatures were 580°C at depths 22 km. P/T ratios were 1*10-3GPa/°C and T/Depth 26°C/km. With respect to the P-prograde path, the temperature values, at same pressure, are slightly higher, even if the T/Depth ratio keeps lower than a standard stable geotherm (e.g. Spear, 1993).