Episodic hydrofracturing and large-scale flushing along deep subduction interfaces: Implications for fluid transfer and carbon recycling (Zagros Orogen, southeastern Iran)

We investigate the late Cretaceous blueschist-facies (480 °C-1.8 GPa) segment of Zagros suture zone, a well-preserved block-in-matrix paleo-subduction channel. aim to determine relative chronology, conditions deformation, and potential fluid sources processes associated with widespread occurrence lawsonite + clinopyroxene glaucophane veins aragonite-bearing hydraulic breccias. use multi-scale approach methodology provide new insights into deep flow mechanisms as well constrain possible sinks CO 2 -bearing fluids in subducting slab. Petrological analyses suggest that silicate-rich vein systems began precipitating during early burial evolved ongoing shearing-related deformation blueschist-facies, while most carbonate-rich hydrofractures formed at near-peak P-T conditions. In situ LA-ICP-MS trace element reveal that: (i) individual silicate host-vein pairs have similar REE signatures, reflecting local-scale fluid-mediated redistribution, (ii) carbonate-bearing metasediments also signatures (iii) blueschist-hosted exhibit enrichments along their rims, suggesting an increasing contribution metasedimentary-derived upon approaching peak . Carbonate O C isotope compositions metasedimentary rocks range from +13.6 +17.9‰ (δ 18 VSMOW ) − 1.0 +3.1‰ 13 VPDB ), demonstrating related large-scale H homogenization far-traveled mafic- ultramafic-derived fluids. Sr Nd isotopic ratios carbonate adjacent host resemble composition indicating rock-buffered occurred between infiltrating rock matrix, possibly episodic porous flow. Thermodynamic modeling predicts decarbonation via fluid-assisted reactions is inefficient carbon release likely occurs deeper subduction interface (i.e., eclogite-facies). propose deeply produced O-rich interacted lithologies facilitating further transport pulses (e.g., porosity waves) traveled kilometer-scale parallel interface, contributing herein observed triggering hydrofracturing lawsonite-blueschist-facies (≈50-60 km depth). Veinsets exhumed subducted hence unique opportunity understand fluid-rock interaction region which tremor slow slip events phenomena occur.