ABSTRACT The Rocciavrè massif is a large eclogitized ophiolitic fragment exposed in the Western Alps (Piemonte, Italy) exhibiting an almost complete sequence of subducted Liguro‐Piemont lithosphere. Raman spectroscopy on carbonaceous material metasediments from and juxtaposed Orsiera indicates maximum temperatures range ~510°C–550°C, whereas thermodynamic modelling mafic lithologies reveals peak burial metamorphic conditions 550°C–590°C/2.2–3.0 GPa for both units, suggesting absence gap...

Understanding the evolution of convergent plate boundaries and mechanisms strain accommodation through time space is made possible by studying exhumed subduction complexes within orogenic belts. This study uses internal zones Western Alps, one largest best-preserved fossil in world, to track transition from collision. We herein combine in-situ Ar-Ar Rb-Sr data on white micas with pressure-temperature estimates derived pseudosection modeling Raman thermometry carbonaceous material, along...

Chlorite is a ubiquitous product of metamorphism, alteration magmatic rocks and hydrothermal processes owing to its large stability field wide compositional range. Its composition governed by several substitutions has been used as geothermometer, on the basis empirical, semi-empirical, thermodynamic models. As in some other phyllosilicates petrological interest, oxidation state iron chlorite may differ from usually assumed divalent state. However, crystal chemistry trivalent remains poorly...

Abstract Meter‐ to hectometer‐size horizons of carbonate‐bearing talcschists are found along or near the contacts between different Liguro‐Piemont subduction slices. Through mineral and bulk‐rock geochemistry, fluid inclusion analyses, titanite U‐Pb geochronology, this study shows that these formed by transformation serpentinites, at conditions close peak burial, due infiltration sourced from surrounding sediments. These rocks containing large amounts carbonates high concentrations...

Abstract In the Western Alps, oceanic lithosphere fragments recovered from subduction are exposed continuously across Liguro‐Piemont domain. this nappe‐stack, Schistes Lustrés metasediments volumetrically dominant and contain large amounts of high‐pressure lawsonite‐ Fe‐Mg carpholite‐bearing veins. These veins formed close to peak burial conditions at 30–60 km depth where deep slow slips tremors occur. 12 studied outcrops, vein thickness distribution fit power laws while spacings clustering...

Abstract Continental subduction and collision are not merely follow-ups of oceanic but mark the transition from lithospheric-scale deformation localized along interface to crustal-scale distributed across orogen. In order unravel processes typifying dynamic changes collision, we have characterized pressure-temperature (P-T) spatio-temporal evolution rocks on each side tectonic contact (Briançonnais–Liguro-Piemont [Br-LP] contact) separating subducted remnants continental fragments Western...

Fluid circulation and deformation mechanisms in the Schistes Lustrés

Despite the recognition that fluids play an important role in subduction zone processes, extent of fluid circulation and fluid-rock interactions within accretionary complexes is still not fully understood. Here, we examined Li elemental isotopic systematics inclusions trapped hydrothermal quartz veins metasedimentary rocks from three paleo-accretionary (Kodiak complex, Alaska; Shimanto Belt, Japan; Western Alps), which are contemporaneous with burial metamorphism at temperatures ranging 250...

In nature, very few organic compounds are recognized as abiotic. Abiotic methane (CH4) is the most abundant, and can be accompanied by short-chain hydrocarbons (ethane, propane) or acids (formate, acetate) in fluids occurring molecular hydrogen (H2)-enriched hydrothermal systems where olivine-bearing rocks altered via serpentinization reactions, such along slow ultra-slow spreading ridges. addition to those volatiles dissolved species, studies of oceanic serpentinites have highlighted low...

Abstract The neodymium hydroxynitrate, Nd(OH) 2 (NO3).H O, (PDF #37-1841) has been investigated by means of X-ray powder diffraction data. unit cell dimensions were determined from diffractometer methods, using strictly monochromatized CuKα 1 radiation, and evaluated indexing programs. monoclinic found was a = 19.381(4)Å, b 3.884(1)Å, c 6.291(1)Å, β 96.43(2)°.

Continental subduction and collision are not merely follow-ups of oceanic but mark the transition from lithospheric-scale deformation localized along interface to crustal-scale distributed across orogen. In order unravel processes typifying dynamic changes collision, we have characterized pressure-temperature (P-T) spatio-temporal evolution rocks on either side tectonic contact (Briançonnais/Liguro-Piemont – Br/LP contact) separating subducted remnants continental...

<p>Important amounts of fluids are released in subduction zones by successive dehydration reactions occurring both the previously hydrated oceanic crust (and mantle) and overlying sedimentary cover. The release circulation such rocks have major consequences on their mechanical chemical behavior. Indeed, presence a free fluid phase strongly modifies rock rheology, fracturing properties, could be implicated intermediate-depth earthquake slow slip events nucleation. Moreover,...

<p>Fragments of subducted slow-spreading oceanic lithosphere are exposed continuously in the Liguro-Piemont domain Western Alps. By combining new and literature petrological data, interpolated maps maximum temperatures, Si contents phengite as a proxy for peak pressure thermodynamic modelling, we provide detailed framework metamorphic conditions experienced by distinct subduction slices. High-resolution mapping confirms marked eastward increase grade throughout domain, well...

<p>The objective of this work is to study the fluid rock-interactions at low metamorphic grade in subduction zones. We focused particular on evolution metapelites from base seismogenic zone (⁓250℃) down-dip transition aseismic domain (⁓330℃). In three examples examined here (Kodiak Complex Alaska, Shimanto Belt Japan, French Alps), we followed variations mineralogy, trace element budget, as well inclusion elemental and...