Geological Studies of Ophiolite Collection Allahyarlu, Northwest of Iran

The principal rock units are a gabbro sequence, late intrusive rocks that consist largely of the plagiogranite and volcanic rocks, which are largely pillow basalts interbedded with pelagic sedimentary rocks, including radiolarian cherts. Chondrite- and primitive mantle-normalized incompatible trace element data indicate that the Lahroud ophiolite was derived from a within plate basalt-like mantle source. All rocks are cogenetic geochemically and were derived by fractionation from melts with a composition similar to average E-MORB with calc-alkaline signatures. Plate reconstructions suggest that the rocks appear to be approximately contemporaneous with the Mashhad ophiolites and Rasht ophiolite, which has a crystallization age of ~380 Ma. Rocks from the Lahroud ophiolite complex represent northern Paleo-Tethyan ocean crust that was formed distinctly earlier than crust preserved in the Ma Paleo-Tethys suture zone ophiolite from upper Paleozoic to Later Teriassic. The results from microfossil studies show the presence of Paleozoic biostratigraphy (e.g., Paleotextularia, Nodosinella cf. concinna, Pseudokahlerina, Cylindrica, Earlandia, Endothyra baileyi, pachyphloia, Fusulinella Stafella and Bivalve, Paratikhine). The data suggest that although the initial rifting and crystallization of the oceanic crust of the Lahroud ophiolite began in the Carboniferous, with volcanic activities continuing through to the late Triassic.