Subduction zone-related metasomatism of Devonian oceanic lithosphere: Evidence from mineralogical, geochemical, and O-H-Sr isotope characteristics of amphibole-bearing peridotites of the Sowie Mountain Block (SW Poland)

Ahmed H. Ahmed, Mohamed M. Hamdy, Thomas C. Meisel

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The serpentinized peridotite bodies found in gneisses of the Sowie Mountains Block (SMB) in the Central Sudetes of SW Poland (NE segment of the Bohemian massif) are significanly metasomatized. Mineral chemical and whole-rock geochemical data combined with Rb-Sr-Sm-Nd-O-H isotope data suggest that these peridotites are refractory oceanic mantle relics from supra-subduction zone to mid-ocean ridge. They and the nearby Devonian (∼400 Ma) ophiolitic ultramafic rocks most probably came from the same mantle source. The studied peridotites are all rich in Ti, LREE and FME, except for a few that are slightly depleted in LREE. Mineralogical changes include formation of metasomatic poikilitic amphiboles and olivine, as well as metamorphic Cpx and Opx. Mixing with metasomatic sulfide-rich liquids and PPGEs (Rh, Pt, and Pd) enrichment are also supposed. The εNd and 87Sr/86Sr ratios are similar to the compositions of HIMU, EM2, and continental basalt, indicating that the depleted mantle protolith was commonly mixed with components of subducted oceanic crust and rare continental crust input. Also, the δ18O values of separated amphiboles are comparable to metasomatic fluids derived from subducted oceanic slab. The contrasting δ18O and δD values of amphibole and serpentine minerals show that serpentinization fluids are not the amphibole-forming agent. The metasomatism of the investigated peridotites most likely occurred as a result of their emplacement in the SMB, concurrently with the SMB's HT-HP metamorphism.
Original languageEnglish
Article number107547
Number of pages25
Issue numberApril
Publication statusPublished - Apr 2024

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  • Amphibole-bearing peridotites
  • Metasomatism
  • Rb-Sr-Sm-Nd-O-H isotope
  • Sowie Mountains Block (SMB)
  • SW Poland

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