The Kermanshah ophiolites (KO) crop out along the Main Zagros Thrust and consist of an ophiolitic mélange including several rock-associations that record the geodynamic evolution of the Tethys between Arabia and Eurasia continental margins. Mineral and whole-rock chemical and isotopic data allowed the recognition of the tectono-magmatic significance of the different rock-types forming the KO, which are: 1) Exhumed subcontinental mantle lherzolites and associated gabbros and basaltic dykes that testify for a Triassic, asymmetrical continental break-up. 2) Pillow lavas ranging from alkaline basalt to P-MORB and E-MORB, which record the Late Triassic volcanism associated with plume effects occurring at the continent-ocean transition zone. 3) Foliated gabbro sequences (with N-MORB signature) and depleted lherzolites representing the conjugate magmatic rocks-mantle residua formed in a mid-ocean ridge setting during the steady-state spreading phase (Late Triassic- Late Jurassic). The residual MOR mantle was subsequently trapped in a SSZ and enriched in LREE by subduction-derived fluids. 4) Depleted harzburgites representing the residual mantle formed by multi-stage melt extraction (10-20% MORB melt + 25-30% boninite melt), which testify for the existence of an intra-oceanic arc associated with the consumption of the Tethys by a NE-dipping subduction (Late Jurassic). These data suggest that the eastern Tethys was characterized by rifted margins “intermediate” between the two ideal end-members: volcanic rifted margins (E Greenland-type) and non-volcanic rifted margins (Iberia-type). In fact, it was characterized by pulsed, asymmetrical rifting (like Iberia-type) and volcanism associated with plume effects (like E Greenland-type).
The Kermanshah ophiolitic complex (Zagros belt, Iran): A key area for understanding the geodynamic evolution of the eastern Tethys.
SACCANI, Emilio;BECCALUVA, Luigi
2012
Abstract
The Kermanshah ophiolites (KO) crop out along the Main Zagros Thrust and consist of an ophiolitic mélange including several rock-associations that record the geodynamic evolution of the Tethys between Arabia and Eurasia continental margins. Mineral and whole-rock chemical and isotopic data allowed the recognition of the tectono-magmatic significance of the different rock-types forming the KO, which are: 1) Exhumed subcontinental mantle lherzolites and associated gabbros and basaltic dykes that testify for a Triassic, asymmetrical continental break-up. 2) Pillow lavas ranging from alkaline basalt to P-MORB and E-MORB, which record the Late Triassic volcanism associated with plume effects occurring at the continent-ocean transition zone. 3) Foliated gabbro sequences (with N-MORB signature) and depleted lherzolites representing the conjugate magmatic rocks-mantle residua formed in a mid-ocean ridge setting during the steady-state spreading phase (Late Triassic- Late Jurassic). The residual MOR mantle was subsequently trapped in a SSZ and enriched in LREE by subduction-derived fluids. 4) Depleted harzburgites representing the residual mantle formed by multi-stage melt extraction (10-20% MORB melt + 25-30% boninite melt), which testify for the existence of an intra-oceanic arc associated with the consumption of the Tethys by a NE-dipping subduction (Late Jurassic). These data suggest that the eastern Tethys was characterized by rifted margins “intermediate” between the two ideal end-members: volcanic rifted margins (E Greenland-type) and non-volcanic rifted margins (Iberia-type). In fact, it was characterized by pulsed, asymmetrical rifting (like Iberia-type) and volcanism associated with plume effects (like E Greenland-type).I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
