Geochemistry and Eruptive Environment of the Mafic Rock Series in the Balvard-Baft Ophiolites

Basalts, gabbros, tuffs, diabasic dikes, agglomerates and breccias and the rock fragments of breccias are the main mafic constituents of the Balvard-Baft ophiolites. Geochemical signatures of these rocks reveal depletion in HFSE and enrichment in LILE and simultaneous occurrence of island-arc tholeiitic and calc-alkalic volcanisms. These geochemical behaviors are the evidences suggesting that these mafic rocks are of supra-subduction zone affinity. These special signatures associated with the position of the Nain-Baft ophiolitic belt behind the Mesozoic magmatic arc of the Sanandaj-Sirjan zone, suggest back-arc spreading (in the active margin of the Central Iranian block), during middle Cretaceous due to the oblique subduction of Neo-Tethys beneath the Central Iranian block.