Document Type : Original Research Paper
Authors
1 Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran
2 Faculty of Earth Sciences, Geological Survey of Iran, Tehran, Iran
Abstract
The Marphioon pluton in the central part of Urmia-Dokhtar magmatic arc is among the Neotethyan oceanic lithosphere subduction-related intrusions. The composition of this pluton changes from granodiorite to tonalite. Marphioon granitoid gives rise to contact aureole zone with different peripheral thicknesses. U-Pb geochronology of a sample from southern outcrop suggests that these rocks have crystallized at 18.89±0.20 Ma in Early Miocene.These rocks belong to medium-K calc-alkaline series with I-type affinities. In terms of geodynamic setting, this intrusion is classified as volcanic arc granites and active continental margin granites. Qualitative interpretation of aeromagnetic data suggested a diorite to gabbroic composition due to high magnetic susceptibility.The Marphioon intrusion is strongly tectonized due to faulting. Basement dextral strike-slip faults and their sinistral conjugates are potential mechanisms for its exposure. It seems that the Marphioon magma in an active continental margin, originated from the partial melting of the lower continental crust with the involvement of mantle-derived melts, where mafic magma in mantle wedge has provided optimal temperature and fluids for this melting in the lower crust. Collectively, Marphioon intrusion seems to be emplaced during the transition time from subduction to collision in the Urmia-Dokhtar magmatic arc contemporaneous with the closure of the Neotethyan ocean.
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