Petrological constraints on the origin of pyroxenite dykes in the lithospheric mantle of the cheshmeh-bid ophiolitic Massif, Southern Iran
Articolo
Data di Pubblicazione:
2021
Citazione:
Petrological constraints on the origin of pyroxenite dykes in the lithospheric mantle of the cheshmeh-bid ophiolitic Massif, Southern Iran / A. Eslami, G. Borghini, A. Montanini, G. Grieco, C. Marchesi. - In: OFIOLITI. - ISSN 0391-2612. - 46:1(2021 Jan), pp. 63-81.
Abstract:
The Cheshmeh-Bid ophiolitic massif in the Khajeh-Jamali district (Southern Iran) is dominated by harzburgite-dunite tectonites locally intruded by orthopy-roxenite dikes. These latter are composed of dominant coarse orthopyroxene with minor olivine, Cr-spinel, clinopyroxene and amphibole. Estimated equilibrium temperatures for Mg-hornblende and edenitic amphibole reveal a late stage magmatic origin. The Cheshmeh-Bid orthopyroxenites are characterized by very low Al2O3, CaO, Na2O and TiO2 abundances coupled to relatively high MgO and SiO2 contents. They display U-shaped REE patterns, selective LILE enrichment and positive Pb and Sr anomalies. The host harzburgites are highly refractory mantle residues resulting from fluid-assisted melting. Field observations and mineral assemblages suggest that the pyroxenites formed by melt injection along fractures within rather cold ambient harzburgites and chromitites at moderate pressure (P > 1 GPa). Based on bulk-rock compositions and mineral chemistry, we infer that the Cheshmeh-Bid orthopyroxenites originated from the intrusion and crystallization of hydrous Si-rich, low-Ca melts with a boninite signature in a supra-subduction environment. Fine-grained neoblastic domains developed in the pyroxenites in response to subsolidus ductile deformation and recrystallization, which were most likely related to the exhumation of the Cheshmeh-Bid ophiolite massif.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Cheshmeh-Bid ophiolite massif; Hydrous boninite melt; Iran; Orthopyroxenite; Supra-subduction setting
Elenco autori:
A. Eslami, G. Borghini, A. Montanini, G. Grieco, C. Marchesi
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