Petrography and mineral chemistry of amphibolitic fragments in the south of Nain Ophiolite skarns, Central Iran

Shirdashtzadeh, N; Torabi, G; Samadi, R

doi:10.22071/gsj.2017.44135

Petrography and mineral chemistry of amphibolitic fragments in the south of Nain Ophiolite skarns, Central Iran

Document Type : Original Research Paper

Authors

N Shirdashtzadeh ¹

G Torabi ²

R Samadi ³

¹ Post-Doctoral Researcher Fellow, Department of Geology, Faculty of Science, University of Isfahan, Isfahan, Iran

² Professor, Department of Geology, Faculty of Science, University of Isfahan, Isfahan, Iran

³ Assistant Professor, Department of Geology, Mashhad Branch, Islamic Azad University, Mashhad, Iran

10.22071/gsj.2017.44135

Abstract

Some dark green fragments of amphibolites are found within skarns at the south of Nain Ophiolite at the northeast of Nain city. They are similar to ortho-amphibolites (metamorphosed basic rocks) of this ophiolite in hand specimen, but mineralogically they are composed of amphibole (magnesio-hornblende, Mg#>0.95), clinopyroxene (diopside, Mg#~0.61), garnet (grossular – andradite, with Grs_~63-87And_~12-35), quartz, and minor amount of calcite and wollastonite. Accessory minerals are including chlorite and prehnite, mostly filling the fractures. Field studies, petrography and mineral chemistry indicate that amphibolitic fragments mineralogically differ from the skarns and ortho-amphibolites of this ophiolite; so they can be considered as olistoliths with sedimentary origin (calcic marls of sea floor), turned into amphibolitic rocks (para-amphibolite) during the regional metamorphism at amphibolite - granulite facies and low oxygen fugacity.

Keywords

Mineralogy

Amphibolite

Skarn

Ophiolite

Nain