Petrology and geochemistry of diabasic dikes and andesitic-basaltic lavas in Noorabad-Harsin ophiolite, SE of Kermanshah, Iran

The Noorabad-Harsin ophiolite is a part of the eastern Mediterranean-Zagros-Oman Tethyan ophiolites. This area is located in the south-southwest of the main Zagros thrust zone. This ophiolite consists of peridotites, serpentinites and pegmatite gabbros as mantle sequence whereas crustal sequence is composed of locally layered gabbros, isotropic gabbros, sheeted dike complex, basaltic to andesitic lavas and sedimentary rocks (radiolarites and Late Cretaceous pelagic limestones). The diabase dikes are enriched in LREE relative to HREE (La(n)/Yb(n)=1.7–3.3). Also, the andesites are enriched in LREE relative to HREE (La(n)/Yb(n)=3.1–5.37) and the pillow lavas are enriched in LILE (Th(n)/La(n)=2.1) while show a depletion in HFSE (Nb(n)/La(n)=0.07–0.2). The basaltic-andesitic lavas exhibiting mainly calc-alkaline, with minor island-arc tholeiitic affinities, are characterized by enrichment in LILE and LREE and depletion in HFSE. These geochemical characteristics compared with other Tethyan ophiolites along the Bitlis-Zagros suture zone reveal a suprasubduction zone environment for the genesis of the Noorabad-Harsin ophiolites.