The Kermanshah ophiolitic complex consists of a mélange formation including dismembered ophiolitic sequences. These ophiolites are located along the Main Zagros Reverse Fault, which marks the ophiolitic suture zone between the Zagros belt and the Sanandaj-Sirjan zone. They represent the Neo-Tethyan oceanic lithosphere originally existing between the Arabian (to the south) and Eurasian (to the north) continental margins. The Kermanshah ophiolites were emplaced onto platform carbonate rocks representing the Northeastern Arabian margin. The Kermanshah ophiolitic complex is composed of various partial sequences including: mantle tectonites; gabrro and cumulate gabbro; (with isotropic, pegmatoid and foliated texture) and very scarce pillow basalts. Petrographic observations, mineral chemistry, wholerock chemistry, and rare earth element (REE) modelling carried out on mantle tectonites and intrusive rock associations point out for the following conclusions. (1) The foliated gabbroic sequence has NMORB chemical signature. (2) The pegmatoid gabbroic sequence shows an E-MORB signature. Comparison with the well-studied Oman ophiolites suggests that this sequence may have formed during the early stage of oceanic spreading. (3) The depleted lherzolites show mild depletions in HREE and variable depletion in LREE. REE modelling shows that they may represent a residual mantle after 15-20% removal of N-MORB melts. Some lherzolites show a moderate enrichment in La and Ce with respect to Sm, suggesting that this residual MORB mantle was subsequently trapped in a suprasubduction zone (SSZ) mantle wedge and enriched in LREE by subduction-derived fluids. (4) The depleted harzburgites have a significant depletion in incompatible and REE, coupled with a marked LREE enrichment with respect to medium REE. REE modelling shows that they may represent residual a mantle after 25-30% removal of boninitic-type melts in an intra-oceanic arc setting.
Geochemistry and petrology of the Kermanshah ophiolites (Zagros belt, Iran) an evidence for the Neo-Tethyan magmatism in the northern Arabian realm.
SACCANI, Emilio;BECCALUVA, Luigi
2012
Abstract
The Kermanshah ophiolitic complex consists of a mélange formation including dismembered ophiolitic sequences. These ophiolites are located along the Main Zagros Reverse Fault, which marks the ophiolitic suture zone between the Zagros belt and the Sanandaj-Sirjan zone. They represent the Neo-Tethyan oceanic lithosphere originally existing between the Arabian (to the south) and Eurasian (to the north) continental margins. The Kermanshah ophiolites were emplaced onto platform carbonate rocks representing the Northeastern Arabian margin. The Kermanshah ophiolitic complex is composed of various partial sequences including: mantle tectonites; gabrro and cumulate gabbro; (with isotropic, pegmatoid and foliated texture) and very scarce pillow basalts. Petrographic observations, mineral chemistry, wholerock chemistry, and rare earth element (REE) modelling carried out on mantle tectonites and intrusive rock associations point out for the following conclusions. (1) The foliated gabbroic sequence has NMORB chemical signature. (2) The pegmatoid gabbroic sequence shows an E-MORB signature. Comparison with the well-studied Oman ophiolites suggests that this sequence may have formed during the early stage of oceanic spreading. (3) The depleted lherzolites show mild depletions in HREE and variable depletion in LREE. REE modelling shows that they may represent a residual mantle after 15-20% removal of N-MORB melts. Some lherzolites show a moderate enrichment in La and Ce with respect to Sm, suggesting that this residual MORB mantle was subsequently trapped in a suprasubduction zone (SSZ) mantle wedge and enriched in LREE by subduction-derived fluids. (4) The depleted harzburgites have a significant depletion in incompatible and REE, coupled with a marked LREE enrichment with respect to medium REE. REE modelling shows that they may represent residual a mantle after 25-30% removal of boninitic-type melts in an intra-oceanic arc setting.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.