Thermochronologic evidence for the exhumational history of the Alpi Apuane metamorphic core complex, northern Apennines, Italy

Abstract

[1] The Apennine Range is a young convergent orogen that formed over a retreating subduction zone. The Alpi Apuane massif in the northern Apennines exposes synorogenic metamorphic rocks, and provides information about exhumation processes associated with accretion and retreat. (U-Th)/He and fission-track ages on zircon and apatite are used to resolve exhumational histories for the Apuane metamorphic rocks and the structurally overlying, very low grade Macigno Formation. Stratigraphic, metamorphic, and thermochronologic data indicate that the Apuane rocks were structurally buried to 15-30 km and $400°C at about 20 Ma. Exhumation to 240°C and 9 km depth (below sea level) occurred at 10-13 Ma. By 5 Ma the Apuane rocks were exhumed to 70°C and $2 km. The Macigno and associated Tuscan nappe were also structurally buried and the Macigno reached its maximum depth of 7 km at $15 to 20 Ma. Stratigraphic evidence indicates that the Apennine wedge was submarine at this time. Thus we infer that initial exhumation of the Apuane was coeval with tectonic thickening higher in the wedge, as indicated by synchronous structural burial of the Tuscan nappe. From 6 to 4 Ma, thinning at shallow depth is indicated by continued differential exhumation between the Apuane and the Tuscan nappe at high rates. After 4 Ma, differential exhumation ceased and the Apuane and the Tuscan nappe were exhumed at similar rates ($0.8 km/Ma), which we attribute to erosion of the Apennines, following their emergence above sea level.

Speleogenesis in highly geodynamic contexts: The quaternary evolution of Monte Corchia multi-level karst system (Alpi Apuane, Italy)

“…Apatite fission track dating of metamorphic rocks gives us a first constraint about the time of exhumation. According to the published data, about 4.5−5.0 Ma ago the metamorphic rocks were still covered by at least 3-4 km of rock (Balestrieri et al, 2003;Fellin et al, 2007). We don't know the real exhumation rate of the metamorphic complex but we can suppose that it was exposed not earlier than 3.0−3.5 Ma ago.…”

Orogenic processes and the Corsica/Apennines geodynamic evolution: insights from Taiwan

“…Bézert and Caby 1988;Brunet et al 2000;Chopin et al 2008;Dal Piaz and Zirpoli, 1979;Danisik et al 2007;Fournier et al, 1991;Lahondère and Guerrot 1997;Lahondére 1996;Tribuzio and Giacomini 2002;Molli 2008;Vitale Brovarone et al 2009), Southern Tuscany and Alpi Apuane (based on Kligfield et al 1986;Fellin et al 2007;Giorgetti et al 1998;Jolivet et al 1998;Molli et al 2000;Rossetti et al 2002;Theye et al 1997) Corsican-derived continental units and continental slices from the former OCT show a variable high-pressure/lowtemperature metamorphic imprint. It ranges from lower grade (high-pressure greenschist to lower blueschist facies) in the external and presently geometrically lowermost units, to eclogite facies in the more internal and uppermost ones (Figs.…”

“…The early foliations are dated by 40 Ar/ 39 Ar geochronology in the range of 27-20 My (Kligfield et al 1986;Deino et al 1992, Brunet et al 2000 and exhumation at 240°C and 9 km of depth around 10-13 Ma as derived by Zircon FT data (Fellin et al 2007). …”

Edough-Cap de Fer Polymetallic District, Northeast Algeria: II. Metallogenic Evolution of a Late Miocene Metamorphic Core Complex in the Alpine Maghrebide Belt

“…15, the late thermal history of the massif is marked by exhumation along a high temperature-low pressure path and punctuated by thermal pulses of magmatic origin (heat advection in uppermost crust), plus hydrothermal convection and the formation of a series of metallic deposits at progressively decreasing temperatures and depths. The estimated exhumation rates for the Burdigalian/Langhian boundary and early Langhian times in the Edough massif (1.1 mm yr −1 ; Fellin et al 2007), and the Aspromonte in Calabria (0.9 mm yr −1 ; Heymes et al 2010). The first hydrothermal event took place in the latest Burdigalian (ca.…”