Petrogenesis of the late Miocene Chenar volcanism in the southeast Urumieh-Dokhtar magmatic belt, Kerman, Iran: evidence from geochemical, U-Pb geochronologic, and Hf isotopic constraints

Abstract

The Chenar volcanic cone intruded the southeastern part of the Dehaj-Sarduiyeh volcano-sedimentary belt, in the southeast Urumieh-Dokhtar magmatic arc in Iran. The adakitic rocks, with porphyritic texture, mainly consist of rhyodacites and dacites,commonly comprised of phenocrysts of plagioclase, hornblende and biotite, with rare K-feldspar in a groundmass composed of plagioclase, K-feldspar and quartz. They yielded U-Pb zircon ages of 5.52±0.099Ma, 5.46±0.12Ma, and 6.44±0.12Ma, and radiogenic ɛHf(t) values ranging from +3.1 to +12.7. The whole-rock geochemical analysis of these rocks reveals transitional calc-alkaline to shoshonitic characteristics. The geochemical characteristics of the study rocks, particularly their high Sr/Y (⁓51.6-136.8) at low Y (⁓4.43–16.2ppm) and high La/Yb (⁓28.4–118.4ppm) at low Yb (⁓0.2–1.3ppm), are coherent with a high silica adakitic signature. The whole-rock positive Eu/Eu* anomaly and zircon Ce/Ce* anomaly reflect the effects of an oxidized magmatic signature where the rocks of the study area originated from a mantle source. The high silica adakite geochemical characteristics of the Chenar volcanic cone support formation by partial melting of the modified mantle under the influence of metasomatized subducted oceanic slab in a post-collisional environment.