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 ...
Read More
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.
Petrology
Hamid Ahmadipour; Hamideh Salehinejad; Seyed Hesam-Aldin Moeinzadeh; Abbas Moradian
Abstract
Shan Abad–Raviz basic intrusions from the West of Rafsanjan (Kerman province), represent a part of Dehaj-Sarduyieh belt and intruded into the Eocene volcano-sedimentary rocks as dykes and apophyses. Thicknesses of the dikes and the diameters of the patches reach up to 4 and 10 meters respectively. ...
Read More
Shan Abad–Raviz basic intrusions from the West of Rafsanjan (Kerman province), represent a part of Dehaj-Sarduyieh belt and intruded into the Eocene volcano-sedimentary rocks as dykes and apophyses. Thicknesses of the dikes and the diameters of the patches reach up to 4 and 10 meters respectively. In the field, they appear as dark intrusions contain sporadic euhedral pyroxene crystals with up to 5 mm in size. They are gabbro and diorite and their main minerals are plagioclase and pyroxenes set in a fine-grained matrix and show intergranular and porphyroid textures. These rocks have low-K calc-alkaline affinities and their geochemical characteristics tend to the subduction zone settings. In these rocks, 87Sr/86Sr and 143Nd/144Nd ratios vary between 0.70403 to 0.70409 and 0.5128 to 0.5129 respectively and εNd(i) values change between 3.52 to 6.6. These evidences along with the special textures show that their parent magmas affected by fractionation, assimilation and magma mixing processes. Considering that these rocks have intruded into the Eocene volcanics, we suggest that they represent the last stages of Eocene magmatism in the Cenozoic Kerman magmatic belt and intruded into the crust after the intiation of Neo-Tethys subduction beneath to Central Iranian block, probably in a continental margin tectonic setting.
