40Ar/39Ar ages and tectonic setting of ophiolite from the Neyriz area, southeast Zagros range, Iran

An ophiolite, considered to be an allochthonous fragment of Tethyan oceanic crust and mantle, crops out near Neyriz in the Zagros Range, Iran. 40Ar/39Ar ages ranging from 76.8+-23.8 Ma to 105+-23.3 Ma were measured on hornblende from five samples of plagiogranite and diabase from the ophiolite. The most precise ages are 85.9+-3.8 Ma for a diabase and 83.6+-8.4 Ma for a plagiogranite. The weighted mean age of hornblende from the five samples is 87.5+-7.2 Ma which indicates that the igneous part of the Neyriz ophiolite formed during the early part of the Late Cretaceous. Pargasite from amphibolite below peridotite of the Neyriz ophiolite has a 40Ar/39Ar age of 94.9+-7.6 Ma. The pargasite age agrees within analytical uncertainty with the ages measured on diabase and plagiogranite. Comparable ages have been measured on igneous rocks from the Samail ophiolite of Oman and on amphibolite below peridotite of the Samail ophiolite. (orig.)