Recognition of Late Cretaceous Hasanbag ophiolite-arc rocks in the Kurdistan Region of the Iraqi Zagros suture zone: A missing link in the paleogeography of the closing Neotethys Ocean

RESEARCH ring in the Eocene-Oligocene (Aswad, 1999;Aswad et al., 2011).On the Arabian margin, this was superimposed onto the Cretaceous (Balambo) carbonate platform with the deep-water radiolarite Qulqula Group emplaced tectonically on top, followed by deposition of the Tanjero fl ysch in the Maastrichtian.This must have involved the collision of an older arc with the Arabian continental margin in Iraq (Ali, 2012), as already recognized in Oman, Turkey, and Cyprus ophiolites.This postulated arc along the Iraqi-Iranian Zagros section has previously not been recognized.In this paper, we demonstrate that an upper tectonic slice, previously thought to be the Tertiary Walash arc system, is in fact this missing Cretaceous arc along the Iraq-Iran boundary, named here the Hasanbag arc complex.This was achieved via integrated 40 Ar- 39 Ar dating of magmatic hornblende and whole-rock petrography and geochemistry. GEOLOGICAL BACKGROUNDThe study area is situated along the Iraq-Iran-Turkey border, in a rugged elevated topography (e.g., Hasarost Mountain is the highest mountain in Iraq at just over 3600 m) dissected by irregular steep valleys.