Characterisation of amphibolite-facies fluids of Variscan eclogites from the Orlica-Snieznik dome (Sudetes, SW Poland)

摘要: Abstract Eclogites from the Orlica-Snieznik dome (Sudetes, SW Poland) exhibit evidence for Variscan high-pressure metamorphism and a subsequent amphibolite-facies overprint. Three main types of fluid inclusions were observed in quartz partially retrogressed eclogites. Type 1: aqueous inclusions, mostly two-phase (L + V). 2: (a) CO2 ± N2 CH4 normally one-phase some contain graphite as daughter mineral; (b) inclusions. 3: mixed H2OCO2 (LH2O LCO2 VCO2) consisting 70–80 vol% CO2. The texturally earliest are (type 2a) which followed by H2OCO2N2 3) H2O 1) chronological order. Late N2CH4 2b) last to be trapped. Isochores not conformable with peak-metamorphic conditions estimated at temperatures between 640° 790°C minimum pressures >14 kbar. At least three possible explanations must considered: (1) no phase was present during eclogite-facies metamorphism; (2) all trapped event decrepitated retrogression; (3) only under medium-pressure We did succeed identify clearly related metamorphism. However, isochores derived microthermometric measurements can used constrain retrograde P-T path. highest-density isochore early indicates pressure 8 kbar 600°C. N2, re-equilibrated suggest an almost isothermal decompressional uplift 2 600°C, isobaric cooling 200°C. Therefore, rate low relative cooling, indicating relatively long period tectonic inactivity.