High pressure melting of eclogites and metasomatism of garnet peridotites from Monte Duria Area (Central Alps, N Italy): A proxy for melt-rock reaction during subduction

Abstract

 Syn-deformation development of garnet websterites during melt-peridotite interaction in subduction environments.

Subducted organic matter buffered by marine carbonate rules the carbon isotopic signature of arc emissions

“…5 ). The interaction of subducted ocean carbonates and organic matter with fluids coming from the dehydration of the down-going slab 25 , 42 is a continuous process starting early in the forearc region 9 , 43 (Fig. 5 ; Supplementary Fig.…”

Reaction‐Induced Mantle Weakening at High‐Pressure Conditions: An Example From Garnet Pyroxenites of Ulten Zone (Eastern Alps, N Italy)

“…The origin of pyroxenites has been related to a variety of magmatic and metamorphic processes, including: i) recycling of crustal material during subduction (Allègre & Turcotte, 1986; Kornprobst et al., 1990; Morishita & Arai, 2001; Morishita et al., 2003; Yu et al., 2010); ii) moderate‐ to high‐pressure crystal segregation from magmas rising from asthenospheric mantle sources (Bodinier et al., 1987a, 1987b; Dantas et al., 2007; Gysi et al., 2011; Kempton & Stephens, 1997; Keshav et al., 2007; Mukasa & Shervais, 1999; Rivalenti et al., 1995; Takazawa et al., 1999; Vannucci et al., 1993; Warren et al., 2009); iii) refertilization of "depleted" upper mantle through melt‐peridotite reactions during asthenospheric upwelling (Bodinier et al., 2008; Dantas et al., 2009; Garrido & Bodinier, 1999; Van Acken et al., 2010); and iv) reaction between peridotites and fluids/melts derived by high‐pressure dehydration/melting of the subducted crust (e.g. Malaspina et al., 2006, 2017; Pellegrino et al., 2020; Wang et al., 2008).…”

Geochemical evolution of melt/peridotite interaction at high pressure in subduction zones

“…Melt-peridotite interaction via reactive porous flow has been largely studied in mantle samples from oceanic and subcontinental settings (e.g., Godard et al, 1995;Ionov et al, 2005;Borghini et al, 2020). In comparison, we know little about the role of these interactions at high pressure (HP) and relatively low temperature (LT) such as those reached at the slab interface, even in warm subduction zones (e.g., Malaspina et al, 2006;Scambelluri et al, 2006;Pellegrino et al, 2020).…”

“…The Borgo outcrop of the Monte Duria area (Adula-Cima Lunga unit, Central Alps, Italy) is an ideal example of meltperidotite interaction which occurred under a deformation regime at HP, that enabled the combination of porous and focused flow of eclogite-derived melts into Grt-peridotites (Pellegrino et al, 2020;mineral abbreviations from Warr, 2021). In the Monte Duria area Grt-peridotites occur in direct contact with migmatised orthogneiss (Mt.…”

“…Both eclogites and peridotites record a common HP peak at 2.8 GPa and 750 °C and post-peak high temperature (HT) equilibration at 0.8-1.0 GPa and 850 °C (Tumiati et al, 2018). Grtperidotites show metasomatic pargasitic to edenitic amphibole, dolomite, phlogopite and orthopyroxene after olivine, crystallised after the interaction with crust-derived agents enriched in SiO 2 , K 2 O, CO 2 and H 2 O at peak conditions (Tumiati et al, 2018;Pellegrino et al, 2020). They also show a "spoon-shape" fractionation in LREE (La N /Nd N = 2.4) related to the LREE enrichment in clinopyroxene and amphibole crystallised in the garnet stability field, interpreted by Pellegrino et al (2020) as acquired by the interaction with a hydrous melt.…”