ژئوشيمي و پترولوژي سري هاي مافيك و اپي كلاستيت هاي همراه در افيوليت هاي سيه چشمه، جنوب غربي ماكو

Geochemistry and Petrology of Mafic Rocks and Associated Epiclastites in the Siyah-Cheshmeh Ophiolite (SW of Maku)

Pillow lavas, massive lava flows, basaltic and diabasic dikes, meta basalts, andesites, meta-andesites, gabbros, pegmatite gabbros, dacitic dikes along with epiclastites, hyaloclastites and cold breccias are the main constituents of the crustal unit of the Siyah-Cheshmeh ophiolite. The various rock units of the Siyah-cheshmeh ophiolite are petrographically and geochemically different and based on the trace elements and tectonomagmatic diagrams; they are considered to form in different environments. Some of pillow lavas, basaltic flows, meta-basalts, basaltic fragments in epiclastites and basaltic dikes display alkaline characteristics. They are marked by enrichment in LREE, Nb and Ta. These geochemical behaviors resemble exclusively both to oceanic island basalts (OIB) and to E-MORB-OIB basalts. On the other hand, some rock units including lava flows, pillow lavas, diabasic dikes, andesitic-dacitic dikes, lapilli tuffs, pegmatite gabbros and gabbroic dikes are characterised by high LREE/HREE ratio and depletion in Ti,Nb,Ta and therefore show either IAT or calk-alkaline affinity. It is clear that the formation of OIB-E-MORB basalts are related to the interaction between mantle plumes and an oceanic spreading center. Otherwise, petrogenesis of calk-alkaline and IAT rocks is thought to be related to supra-subduction zone.