Volume 32, Issue 1 (4-2024)
www.ijcm.ir 2024, 32(1): 99-112 |
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1- School of Earth Sciences, Damghan University, Damghan, Iran
Abstract: (552 Views)
The studied area is located in the southeast of Shahrood, north Torud, and northeast of the Central Iran structural zone. The area is one of the Iranian basement terrains which include a wide variety of igneous and metamorphic rocks. The study gabbroic bodies form a small part of this complex and their essential minerals are Plagioclase (labradorite, bytownite), pyroxene (calcic group and augite and clinoenstatite composition), olivine, biotite, and amphibole (calcic group and pargasite and pargasite hornblende composition). Based on the chemical composition of minerals, the magma forming of these rocks has calc-alkaline nature and during their crystallization, the fugacity of oxygen has been high. Geothermometry of pyroxene and amphibole suggest crystallization equilibrium temperatures at gabbroic rocks, for pyro,xene are 900-1200°C and for amphiboles are 820-990°C‑ respectively. Geobarometry calculation of these rocks, using an amount of total amphibole aluminum (Alt is between 2-2.5), estimated between 6.52 to 8.9 kbar and for pyroxene between 5 to 7 Kbar. These conditions are equivalent to the formation and final equilibrium at depth of 23 to 27 km of the lower crust.
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