Petrology, geochemistry, and tectonic setting of Tertiary volcanic and intrusive rocks in the north of Shahr-e-Firouzeh (northeast of Iran)

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Research Center for Ore Deposit of Eastern Iran, Ferdowsi University of Mashhad, Mashhad, Iran

Abstract

The study area is located in 15 km of the north of Shahr-e-Firouzeh in Khorasan Razavi province. The area is situated in the southeast of Quchan-Sabzevar arc magmatic. Lithology of the district includes dacitic lavas, which are intruded by Oligocene porphyritic hornblende granodioritic stock and granodioritic dike as subvolcanic and plutonic rocks. Igneous rocks were overlapped by younger sedimentary rocks. The texture of dacitic unit is porphyric to glomeroporphic with flow groundmass. Quartz, plagioclase, K-feldspar, and hornblende are the main minerals. The texture of hornblende granodiorite porphyry is porphyric to glomeroporphic and plagioclase, K-feldspar, hornblende, and quartz are the common minerals, whereas granodiorite unit is granular and hornblende is not present. Based on geochemical studies, the acidic volcanic and intrusive rocks show metaluminous and medium-K nature. These rocks belong to the I-type granitoid. Enrichment of LREE versus HREE and enrichment of LILE and depletion in HFSE indicate magma formed in subduction zone. The melt originated from partial melting of amphibolite with 10 to 25% garnet. Based on the average amount of major oxides, enrichment of LREE, mostly positive Eu anomaly, high Sr (up to 499 ppm), and low Y (<13 ppm) and Yb (<1.4 ppm) contents, the magma show silica-rich adakitic nature. The intrusive and volcanic rocks of the northern Shahr-e-Firouzeh were generated by partial melting of Sabzevar Neotethyan young and hot subducted oceanic crust and mantle wedge in the continental margin of the Turan plate. 

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History

  • Receive Date: 26 November 2016
  • Revise Date:
  • Accept Date: 26 November 2016

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