Dating of deformation phases using K-Ar and 40Ar/39Ar techniques: results from the northern apennines

Fluid Circulation in the Apuane Alps Core Complex: Evidence from Extension Veins in the Carrara Marble

“…3 may be interpreted as being the result of mixing of the three different end-member fluids: A, B and C. These fluids circulated during the greenschist-facies metamorphism of the AA area. This conclusion is supported by: (1) the vein structural setting, which is compatible with a syn-defonnational and syn- metamorphic fluid infiltration (Kligfield et al, 1986;Carmignani and Kligfield, 1990); (2)the agreement between trapping temperature and pressure estimated by the microthermometric data of primary inclusions (see below), with the P-T conditions of metamorphic peak in the AA (Kligfield et al, 1986;Carmignani and Kligfield, 1990;Costagliola et al, 1998); (3) the absence of post-entrapment reequilibration textures of these fluid inclusions. As far as the source of fluids is concerned, we must consider the hypothesis of a contribution from devolatilization reactions during prograde metamorphism of the host marble.…”

Triassic high-strain shear zones in Hainan Island (South China) and their implications on the amalgamation of the Indochina and South China Blocks: Kinematic and 40Ar/39Ar geochronological constraints

“…), crystalplastic deformation dominantly occurs at the temperatures of 300-450°C in quartz and 400-600°C in feldspar (e.g., Simpson and Schmid, 1983;Tullis and Yund, 1985;Kligfield et al, 1986). These microstructural characteristics hence suggest that the shearing deformation likely developed in the temperature range from 300°C to 600°C.…”

Structural and petrological constraints on the tectono‐metamorphic evolution of the Massa Unit (Alpi Apuane, NW Tuscany, Italy)

“…In the subsequent D2 history, previously formed structures were refolded and the present-day geometry of the tectonic units was achieved. In more detail, the D2 event can be subdivided into an early syn±metamorphic stage (15±8 Ma ago; Giglia and Radicati di Brozolo-1970;Klig®eld et al 1986;Carmignani et al 1994) and younger brittle phases (Molli and Meccheri 2000, and references therein). Within this deformation chronology, Franceschelli et al (1986) and Franceschelli and Memmi (1999) concluded that the peak of metamorphism occurred after D1 and before D2.…”

“…Peak-metamorphic conditions in the Apuane Unit of 300±450 C at 0.5 GPa (Franceschelli et al 1997) and 390±410 C at 0.8 GPa (Jolivet et al 1998) have been deduced. According to Carmignani and Klig®eld (1990) the Alpi Apuane Metamorphic Complex resulted from two main Tertiary deformation events: a D1 event (27±20 Ma ago; Klig®eld et al 1986), related to contraction and nappe stacking, and a younger extensional D2 event. During D1, SW-to NE-directed overthrusts and NE-facing tight to isoclinal recumbent folds with¯at-lying axial surfaces were produced.…”