Major and rare earth element mineral chemistry of low-grade assemblages inform dynamics of hydrothermal ocean-floor metamorphism in the Dinaridic Neotethys

Abstract This contribution provides insights into ocean-floor hydrothermal metamorphism of the fast-evolving Dinaridic Neotethys. Mineralogical, geochemical and Sr isotope data collected from altered ophiolites non-ophiolite basalts/andesites tuffs active continental margin are consistent with alteration trajectories that reflect host-rock composition. suggests fluxes were restricted within a simple closed seawater-fed system. Based on initial isotopic ratios Sr, two fluid–rock interaction trends established: (a) low-to-medium degrees metasomatism in pre-Middle Jurassic anorogenic progressively abated, (b) increased intensities post-Middle orogenic ophiolites. agrees chlorite thermometry Ca-Al-(Fe)-silicate phase chemistry. The metamorphic assemblages belong to zeolite, prehnite-pumpellyite, prehnite-actinolite greenschist facies. facies is reliant temperature systems their fluid Rare earth element (REE) geochemistry shows variable pumpellyite dependent temperatures, prominent Eu Ce anomalies oxidation state, (c) light REE/heavy REE mobilization attributed prevalent ligand complexation, (d) multi-phase percolation across reaction zones heterogeneous permeability. study proposes initiation system(s) at or near spreading centre(s) infancy Such system became more complex during Middle Early Cretaceous time reactive fluids passing recharge area reaching hot zone. An abrupt obliteration established high-temperature regime ensued, following final closure