In summary the microstructural investigations on the Ivozio mafic-ultramafic rock complex, based on a detailed foliation trajectory map, allow to re-define the deformation-metamorphism relationships as synthesised in Fig. 3. In particular the Lws-growth has been attributed at the D1a stage, which according to the thermobarometric estimates, occurred during final stages of P-prograde path at T 550°C. The Ky ± Omp syn D1b assemblage marks Tmax-PTmax conditions experienced by the Ivozio rocks, reached as a consequence of quasi-isobaric T-increase. P-T estimates indicate that these rocks belonging to the continental Austraolpine basement were buried at a high depth (≍70km) at T ≤ 630°C. Following this stage a decrease of P and T is recorded, during the exhumation under low-T conditions, by the development of Pg - Ep syn-D2 assemblage replacing Ky + Omp + Ep. Syn-D3 greenschists retrogradation marks the transition to a higher T/Depth ratio during the final stage of exhumation. To unravel the uplift-rate of this SLZ portion, at the end of its Alpine evolution, we need to relate the inferred successive P-T re-equilibration stages to the geochronological data, available in the literature (see Fig. 7 and Table 1b for references). All the available radiometric ages, obtained by minerals or mineral assemblages re-equilibrated under eclogite facies conditions, have been interpreted as age of P - T peak conditions. In this light we can attribute the age interval of 60 and 70 Ma to the post-D1b stage. On the other hand the greenschists syn-D3 retrogradation in the EMC predates the emplacement of Oligocene intrusives (e.g. Lanza, 1979; Scheuring et al., 1973; Zucali, 2002). Therefore the Ivozio complex accomplished its exhumation path during a time interval of 30-40 Ma, indicating minimal uplift rate of 1.8-2.4 mm year-1.
The P-T prograde evolution (D1 , post-D1a and post-D1b ) and the P-retrograde (D2 ) stage are characterised by a thermal state compatible with the subduction of cold (i.e. old) oceanic materials (Cloos, 1982; Cloos, 1993; Peacock, 1996), suggesting that the regime might have been already in a steady state during the prograde stages of subduction, or at least not characterized by a higher T/depth ratio. Effective mechanisms able to subduct the continental litosphere during active oceanic subduction are tectonic erosion and ablative subduction (Gerya et al., 2002; Lallemand, 1999; Tao, 1996), both already invoked to justify the very low thermal regime characterising eclogites developed in continental crust units of the Alps (e.g. Polino et al., 1990; Spalla et al., 1996). The syn-D3 transition to a higher T/depth ratio may represent the thermal signature of the Alpine collision.
Finally it may be noted that P-T paths inferred for Lws-bearing rocks of the SLZ are quite heterogeneous in shape and versus (Pognante, 1989a; Pognante, 1989b; Pognante, 1991; Spalla and Zucali, 2004): this heterogeneity may indicate that the EMC of SLZ is composed by different tectonic metamorphic units or is the result of strong later thermal heterogeneities in the subduction channel.