TY - JOUR

T1 - Subduction zone-related metasomatism of Devonian oceanic lithosphere

T2 - Evidence from mineralogical, geochemical, and O-H-Sr isotope characteristics of amphibole-bearing peridotites of the Sowie Mountain Block (SW Poland)

AU - Ahmed, Ahmed H.

AU - Hamdy, Mohamed M.

AU - Meisel, Thomas C.

N1 - Publisher Copyright: © 2024 Elsevier B.V.

PY - 2024/4

Y1 - 2024/4

N2 - 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.

AB - 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.

KW - Amphibole-bearing peridotites

KW - Metasomatism

KW - Rb-Sr-Sm-Nd-O-H isotope

KW - Sowie Mountains Block (SMB)

KW - SW Poland

UR - http://www.scopus.com/inward/record.url?scp=85185346151&partnerID=8YFLogxK

U2 - 10.1016/j.lithos.2024.107547

DO - 10.1016/j.lithos.2024.107547

M3 - Article

AN - SCOPUS:85185346151

VL - 470-471.2024

JO - Lithos

JF - Lithos

SN - 0024-4937

IS - April

M1 - 107547

ER -