Geochemical, ⁴⁰Ar/³⁹Ar age, and isotopic data for crustal rocks of the Neyriz ophiolite, Iran

Abstract

Trace-element data (including the rare-earth elements) in the crustal sequence of the Neotethyan Neyriz ophiolite in southwest Iran indicate normal mid-ocean ridge basalt (N-MORB) or island-arc tholeiite chemistry for the Tang-e Hana basalt. The data suggest that the Tang-e Hana rhyodacite, basalt, plagiogranite, and gabbro derived from a low-K tholeiitic parent magma. Trace-element distributions in amphibolite clasts, in the sole detachment of the ophiolite south of Lake Neyriz, correlate well with distributions in basalt clasts in the mélange and in the Tang-e Hana basalt. These trace elements suggest that the amphibolite originated from metamorphism and deformation of a tholeiitic basalt protolith. New 40Ar/39Ar incremental heating plateau ages from two hornblende plagiogranite specimens, in the crustal sequence in Tang-e Hana, are 92.07 ± 1.69 and 93.19 ± 2.48 Ma. Isotopic data for five Tang-e Hana basalts yield εNd values of +7.8 and +7.9, and 87Sr/86Sr values of 0.70368 to 0.70476. The isotopic compositions, ophiolite tectonostratigraphy, and correlation of the 40Ar/39Ar cooling (plagiogranite) and deformation (amphibolite) ages suggest emplacement of the Neyriz ophiolite either into an accretionary prism, through offscraping and subduction erosion, and (or) formation in a supra-subduction zone environment, around 82–96 Ma. Progressive accretion probably led to the development of a fore-arc basin and deposition of Upper Cretaceous – Eocene fore-arc and arc-derived sediments on the ophiolite.

Geodynamic evolution of Upper Cretaceous Zagros ophiolites: formation of oceanic lithosphere above a nascent subduction zone

“…Despite several studies on the Neyriz ophiolite (e.g. Babaie et al 2006; M. R. Jannessary, unpub. Ph.D. thesis, l'Univ.…”

“…The Neyriz ophiolite was thrust over the Pichakun and mélange sheets in Turonian to Maastrichtian time (e.g. Ricou, Braud & Brunn, 1977;Alavi, 1994;Babaie et al 2006), exposing and allowing erosion of the ophiolite and accumulation of such clasts in Upper Cretaceous-Paleocene conglomerates (Haynes & Reynolds, 1980;Lanphere & Pamić, 1983). This episode of erosion may correspond to when SSZ rocks were exhumed, as evidenced by the presence of SSZ clasts in Upper Cretaceous-Paleocene conglomerates (Sabzehei, 1996).…”

“…Ph.D. thesis, Univ. London, 1982) and tholeiitic (Babaie et al 2006) characteristics, serpentinites and metamorphic rocks. The upper mélange is tectonically overlain by ophiolite slices, and both ophiolite and mélange thrust sheets are transported over Cenomanian-Turonian shallow water shelf/platform carbonates (Sarvak Formation; Alavi, 1994).…”

“…de Louis Pasteur, France, 2003) and as seafloor that was scraped off the down-going plate and incorporated into the Zagros accretionary prism (e.g. Babaie et al 2006). The Kermanshah ophiolite is described as a piece of Tethyan oceanic lithosphere scraped off during NE-directed subduction underneath the Iranian block (e.g.…”

Petrology and Geochemistry of Ophiolitic Host Rocks of Copper Mineralization in Dowlat Abad-Tang e Hana Area (Neyriz-Iran)

“…This subject indicates that ophiolite complex is formed in a pre-arc subduction zone [59]. In such an environment in the presence of volatile substances by high-grade partial melting, boninitic magnesium-rich magma has formed.…”