On the magmatic record of the Makran arc, southeastern Iran: Insights from zircon U-Pb geochronology and bulk-rock geochemistry
Journal
Geochemistry, Geophysics, Geosystems
Journal Volume
15
Journal Issue
6
Pages
2151-2169
Date Issued
2014
Author(s)
Abstract
Abstract Twenty‐one magmatic rocks were analyzed for major and trace elements, and a subset of them for Sr‐Nd isotopes and zircon U‐Pb isotopes, to constrain magma genesis and tectonic evolution of the Makran arc, southeastern Iran. Representative samples from the Bazman and Taftan volcanoes yield zircon U‐Pb ages from ∼0.84 to ∼7.5 Ma, consistent with published ages ranging from the Late Miocene to Late Pleistocene. The Mirabad granitic pluton adjacent to and geochemically similar to the Taftan volcano was dated at ∼19 Ma, indicating that arc magmatism might have started earlier than commonly thought in the Early Miocene. The studied rocks show basaltic to rhyolitic compositions, calc‐alkaline affinity, and an orogenic signature involving enrichments in large ion lithophile elements, light rare earth elements, Th and Pb, and depletions in high field strength elements and P, relative to elements of similar incompatibilities. The trace element ratios in a subset of relatively primitive samples are consistent with derivation from a mantle source that underwent subduction‐related enrichment. The covariations of Sr and Nd isotopic ratios, and of these ratios and MgO and SiO 2 , are consistent with combined assimilation and fractional crystallization. The process is modeled using covariations of 87 Sr/ 86 Sr and Sr concentration in the studied rocks given that Sr behaves as neutral or slightly incompatible. We propose, in light of published and our new data, that the Makran represents a window of continental collision between the India‐Eurasia collision zone to the east and the Arabia‐Eurasia collision zone to the west.
SDGs
Type
journal article