Stratigraphy and Palaeontology
Zahra Khajehjavaran; Gholam Reza Ghadami; Mohammad Poosti; Abbas Moradian; Behrouz Karimi Shahraki
Abstract
Andesites are located in the north of shahr-e-babak , central Iran, Urumieh- Dokhtar belt. The main texture in these rocks is porphyry and their phenocrysts are plagioclase (Andesine to Labradorite), pyroxene (Augite), amphibol (Tschermakite and Magnesiohornblende). These properties are signatures of ...
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Andesites are located in the north of shahr-e-babak , central Iran, Urumieh- Dokhtar belt. The main texture in these rocks is porphyry and their phenocrysts are plagioclase (Andesine to Labradorite), pyroxene (Augite), amphibol (Tschermakite and Magnesiohornblende). These properties are signatures of calc- alkaline series formed in a volcanic arc setting. Based on geochemical studies, the rocks show enrichment in LREE rather than HREE. The lack of significant Eu anomalies in REE pattern indicates oxidation state of magma during crystallization. Based on geochemical studies, the clinopyroxenes are Augite and have been crystallized from magma with almost 10% H2O. Fe3+ values of the clinopyroxenes reveal high oxygen fugacity in the magma. Based on the mineral chemistry data, pressure estimates from the clinopyroxenes in the range of 6-10 Kbr and composition yield the crystalization temperatures that range from 900-1100 OC. Typically, clinopyroxenes occure at calc-alkaline orogenic igneous rocks. The plagioclase composition yield the crystalization temperatures that range from 650-750 OC. According to the present study, the rocks are probably the result of the subduction of the Neo-Tethys oceanic lithosphere below the Sanandaj-Sirjan zone, during the Eocene and in a volcanic arc environment.
Ramin Samadi; M. V. Valizadeh; H. Mirnejad; H. Kawabata
Abstract
Metamorphic rocks of Dehnow area mainly consist of gray to black fine-grained schists. Garnet schists are closer to the tonalitic body than the garnet chloritoid schists. There is a thin layer of staurolite and andalusite bearing hornfels between these schists and the Dehnow tonalitic body. Garnet schists ...
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Metamorphic rocks of Dehnow area mainly consist of gray to black fine-grained schists. Garnet schists are closer to the tonalitic body than the garnet chloritoid schists. There is a thin layer of staurolite and andalusite bearing hornfels between these schists and the Dehnow tonalitic body. Garnet schists and garnet chloritoid schists of Dehnow area are mineralogically comprised of quartz, biotite, muscovite, garnet, chlorite, chloritoid, tourmaline and ilmenite. Geothermobarometry results indicate that hornfels (550oC, 4.3 kbar) and garnet chloritoid schist (486-497oC) have formed in lower equilibrium condition in comparison with garnet schist (569oC, 5.3 kbar).
