Petrology
Sakine Moradi; Muhammad Reza Ghorbani; Shao- Yang Jing
Abstract
The Kahak mafic volcanic rocks in the central part of the Urumieh-Dokhtar Magmatic Arc are composed of basalts and basaltic andesite and show sub alkaline to transitional affinity. They are calc-alkaline based on the tholeiitic index (THL). U-Pb zircon dating yields ...
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The Kahak mafic volcanic rocks in the central part of the Urumieh-Dokhtar Magmatic Arc are composed of basalts and basaltic andesite and show sub alkaline to transitional affinity. They are calc-alkaline based on the tholeiitic index (THL). U-Pb zircon dating yields almost 60 (Middle Paleocene) and 24 to 19 Ma (Late Oligocene–Early Miocene) for andesitic basalt and basaltic rocks respectively. These rocks are identified by LREE and LILE enrichment and HFSE depletion with relatively negative or without Eu anomalies and E-MORB like pattern in multiple spider diagrams that.attributed to the subduction of the Neotethyan oceanic slab beneath the central Iranian microcontinent. Based on petrography, trace and rare earth elements, and isotopic features, fractional crystallization played a significant role during magma evolution in these rocks. Trace element modeling suggests that the studied mafic rocks were derived by partial melting within the spinel lherzolite mantle. Isotopic ratios also show that they resulted from lithospheric mantle metasomatized by released fluids from subducted slab sediments. The studied samples might have formed in the extensional regime followed by slab rollback and undergone a continental arc to back-arc basin transition during the Paleocene to Miocene. This basin might have been closed in the middle Miocene.
