Suprasubduction Zone Characteristics of the Guleman Ophiolite, SE Turkey: Evidence from Peridotite Geochemistry

Late Cretaceous ophiolites from SE Turkey has been recognized as remnants of the Neotethys oceanic lithosphere, however, whether these ophiolite suites formed in a Mid-Ocean Ridge (MOR) or a Suprasubduction zone (SSZ) setting is still under debate. This study presents new whole rock elemental and mineral chemistry data of ultramafic peridotites from Guleman ophiolite in SE Turkey. The studied peridotites are all harzburgites with model clinopyroxene contents from 2.6 to 4.8%. These harzburgites are fresh with LOI from 0.3 to 2.7 wt.% and show porphyroblastic textures with granulation and kinking structures commonly found. Negative correlation between whole rock MgO versus Al2O3, CaO, and modal clinopyroxene contents indicates partial melting as a major control over the chemical variation, whereas rims of olivine with elevated FeO could be resulted from metasomatism. Low Al2O3 (<1 wt.%), TiO2 (<0.04 wt.%) and Na2O (<0.1 wt.%) contents in clinopyroxenes and high Cr#(66 82) in spinels suggest there Guleman harzburgites could be residue of high degree of partial melting larger than 30%. Low whole rock HREE content ( < 0.1 chondritic value) also supports this statement. High Fo content (90.9 91.5) in olivines versus the high Cr# in spinels further demonstrate that this high degree of melting could be formed in a SSZ setting (Arai, 1994). Moreover, the presence of clinopyroxene under such high degree of melting also infers a hydrous melting condition (Gaetani & Grove 1998, Bizimis et al., 2000). All above evidence indicates that the Guleman ophiolite is most likely to originate in a SSZ setting. Reference cited: Arai, 1994 Gaetani & Grove 1998 Bizimis et al., 2000