Mineral chemistry and geochemistry of trace and rare earth elements in the ultramafic rocks of west of Maku
Subject Areas :
1 -
Keywords: Ophiolite, Rare earth elements pattern, Serpentinite, Crystal chemistry, Maku,
Abstract :
Late Cretaceous ultramafic rocks of the Neo-Tethyan ophiolite are located in the western Maku near the Iran-Turkey border as small, scattered bodies in vast areas. This part of Iran's territory belongs to the South Armenian Block (SAB), is Gondwanan, and is near the northern Neo-Tethyan suture. This study is focused on rock classification, residual phase composition, and mantle rock formation setting, using exact field relation observation, crystal chemistry studies, and whole rock chemistry accompanied by trace and rare earth elements investigations. The studied rocks were highly serpentinized, Ca-poor, and hydrated. These mantle rocks experienced a high degree of partial melting and were completely depleted from the incompatible elements. Therefore, the abundance of them was measured using a special method. The main phases are forsterite, enstatite, diopside, and chromian-spinel which are seen in the chrysotile-lizarditic serpentinized matrix. The U-shape rare earth elements pattern of the western Maku serpentinites is recorded as crustal contamination evidence. Additionally, the studied ultramafic rocks of western Maku based on the whole rock chemistry, diagrams and relations between major oxide and trace elements belong to the subducted serpentinites group. Also, they practiced high refertilization values by fluid/rock interactions on them. Hence, the enrichment of fluid mobile elements (FMEs) such as U, Pb, and Sr results from secondary events occurring during exhumation.