# O/C Isotopic and EPR Signature of Marble from the Apuan Alps (Italy): A Critical Review
## 2 Material and Methods
### Geological Setting
#### 2.1.2 Tectono-Metamorphic Deformation  
During the Tertiary period, the whole Apuan Alps sedimentary sequence underwent tectono-metamorphic deformation, which resulted into superimposed deformation events (see updated reviews in [26; 32; 33]). The tectono-metamorphic deformation lasted about 15 My (27 to 12 Ma) and gave rise to a complex tectonic assemblage resulting in a series of first-order ductile (NE-E verging) nappe-folds. Namely, they are the Carrara Syncline, VincaAnticline, Orto di Donna-Mt. Corchia Syncline, Tambura Anticline, and Arnetola Syncline, with the crest of the late uplifting dome along the alignment of Boana-Mt. Corchia [17; 18; 31] (Figure 1). The tectono-metamorphic deformation occurred at low-grade metamorphic conditions (general condition with T at 300 to 450 \({}^{\circ}\)C and P up to 0.6-0.8 GPa), which resulted in green-schist facies (pirofillite + phengite-muscovite + quartz + albite + biotite + chloride \(\pm\) epidote \(\pm\) chlorotid) for pelites. These conditions correspond to a depth of about 12 km [18; 31; 34]. Figure 1: Tectonic sketch map of the Apuan Alps metamorphic core complex. ND = Neogene deposits; TN = Tuscan Nappe; MU = Massa unit; PB = Palaeozoic basement; CP = Carbonate Platform: Late Triassic dolomite (Grezzoni) and Early Jurassic marble; PU = Middle Jurassic to Oligocene pelagic units. CS = Carrara Syncline; VS = Vallini Syncline; VA = Vinca Anticline; OS = Orto di Donna Syncline; TA = Tambura Anticline; AS = Arnetola Syncline; BD = Boana dome; blue line = top of the uplifting dome (elaboration, [PERSON]). Deformation rates ranged from 0.8 to 2.5 mm/y (2.5 to 7.9 \(\times\) 10\({}^{-15}\) cm/s) [34; 35; 36], with finite strain ratios varying from 4.0/1 to 12.5/1 with average values of 7.0/1. The authors of [33; 37] argue for a deformation path reaching 30 \({}^{\circ}\)C/km of geothermal gradient, but below 35 \({}^{\circ}\)C/km according to [38]. The authors of [39; 40] envisaged that in the early tectono-metamorphic deformation stage, the uppermost (west side) AAMs were located in the deepest positions at higher equilibrium temperature (430 \({}^{\circ}\)C) with respect to the lowermost (east side) AAMs that were in a higher position at a lower temperature (380 \({}^{\circ}\)C). This situation reversed during the late tectono-metamorphic deformation stage when the folds-stack was formed with a difference in T from the top (west) at 340 \({}^{\circ}\)C to the bottom (east) at 380 \({}^{\circ}\)C.  
During these tectono-metamorphic deformation phases, strong transposition events occurred in the axial-plane high-strain zones. The events resulted into the formation of sheets of \"fault-rock\", the layering of which especially marks the symform-syncline axial plane. Deformation occurred with no evidence of hydrothermal and exotic fluids flowing through the AAM body [41]. Post 8 Ma, during uplifting and exhumation, as core complex, the AAMs were cut in the ductile-brittle transition stage by crack veins filled by spathic calcite in the core of the marble body, and by mixed fluids near the contacts with the other embedding lithologies at 370-380 \({}^{\circ}\)C and 0.30-0.325 GPa [37; 38]. Later, brittle sub-vertical fractures occurred; no faults are presents in the body of the Apuan Alps metamorphic core complex. The rock composition, consisting almost totally of calcite (>97%) in most of the AAMs, prevents assessment of whether the dynamic microfabrics overprint an early annealed fabric or if they are related to the earlier stages of deformation surviving the late static recrystallisation and grain growth [18; 40]. Calcite flow laws suggest that, under P/T conditions, the AAMs deformed by grain-size-sensitive super-plastic deformation mechanisms [42; 43; 44]. This means that the AAM grain sizes resemble those of the original carbonate-platform facies. The main elements of the mesoscopic tectonic fabric recognisable in the field [19; 20; 45] in the AAM body is the main tectono-metamorphic schistosity (S1) called verso by quarriers.