Original paper

Geochemical features of amphibolites from the Qarehaghaj area, East Azerbaijan, NW Iran; implications for paleotectonic setting

Advay, Mehran; Moazzen, Mohssen; Hajialioghli, Robab


Amphibolites, meta-peridotites and marbles exposed in the Qarehaghaj area of the East Azerbaijan province, NW Iran, represent a dismembered and metamorphosed ophiolite complex. Stratigraphic relations and comparison with similar rock units in Central Iran indicate a possible Neoproterozoic - Early Cambrian age for the ophiolite. Amphibolite whole rock chemistry using ele- ments that were relatively immobile during metamorphism indicate two types of parent magmas from which their protoliths crystallized: mid-ocean ridge basalt (MORB) and volcanic arc basalt magma. The association of basalts that originated in both an abyssal and supra-subduction zone setting in a single oceanic basin is attributed to their accumulation in a fore-arc tectonic setting, similar to most of the much younger Neotethys ophiolites. The fore-arc basin was situated at a Proto-Tethyan margin and Proto-Tethyan oceanic crust was obducted during collision, probably during the Pan-African orogeny. The age of the orogeny and related amphibolite-facies metamorphism is not known. It is conceivable that it records a post-obduction, crustal thickening phase of the Pan-African orogeny, but on the other hand there is circumstantial evidence in support of a Tertiary age for metamorphism and partial melting of the mafic rocks. Exhumation of the metamorphic rocks along NW–SE trending thrust faults can be related to extensional phases associated with the Alpine orogeny.


nw iranabyssal and supra-subduction zoneamphiboliteneoproterozoic ophiolites