Premium
Evolution of lithospheric mantle in the north of Nain‐Baft oceanic crust (Neo‐Tethyan ophiolite of Ashin, Central Iran)
Author(s) -
Shirdashtzadeh Nargess,
Torabi Ghodrat,
Morishita Tomoaki
Publication year - 2020
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1111/iar.12342
Subject(s) - peridotite , geology , ophiolite , geochemistry , olivine , plagioclase , mantle (geology) , oceanic crust , partial melting , spinel , petrology , subduction , tectonics , quartz , seismology , paleontology
This study is focused on a plagioclase‐bearing spinel lherzolite from Chah Loqeh area in the Neo‐Tethyan Ashin ophiolite. It is exposed along the west of left‐lateral strike‐slip Dorouneh Fault in the northwest of Central‐East Iranian Microcontinent. Mineral chemistry (Mg# olivine < ~ 90, Cr# clinopyroxene < ~ 0.2, Cr# spinel < ~ 0.5, Al 2 O 3 orthopyroxene > ~ 2.5 wt%, Al 2 O 3 clinopyroxene > ~ 4.5 wt%, Al 2 O 3 spinel > ~ 41.5 wt%, Na 2 O clinopyroxene > ~ 0.11 wt%, and TiO 2 clinopyroxene > ~ 0.04 wt%) confirms Ashin lherzolite was originally a mid‐oceanic ridge peridotite with low degrees of partial melting at spinel‐peridotite facies in a lithospheric mantle level. However, some Ashin lherzolites record mantle upwelling and tectonic exhumation at plagioclase‐peridotite facies during oceanic extension and diapiric motion of mantle along Nain‐Baft suture zone. This mantle upwelling is evidenced by some modifications in the modal composition (i.e. subsolidus recrystallization of plagioclase and olivine between pyroxene and spinel) and mineral chemistry (e.g. increase in TiO 2 and Na 2 O of clinopyroxene, and TiO 2 and Cr# of spinel and decrease in Mg# of olivine), as a consequence of decompression during a progressive upwelling of mantle. Previous geochronological and geochemical data and increasing the depth of subsolidus plagioclase formation at plagioclase‐peridotite facies from Nain ophiolite (~ 16 km) to Ashin ophiolite (~ 35 km) suggest a south to north closure for the Nain‐Baft oceanic crust in the northwest of Central‐East Iranian Microcontinent.