New Findings in 
Applied Geology

New Findings in Applied Geology

Thermobarometry Chelvan igneous rocks using amphibole, biotite, plagioclase, pyroxene minerals, north of Shahrekord, Sanandaj-Sirjan zone

Author
Assist. Prof., Dept., of Geology, Payame Noor University, Tehran, Iran
Abstract
The area is in 45 kilometers north of Shahrekord and near the city of Chelvan in the middle part of the Sanandaj-Sirjan structural zone. The stratigraphic column of the area consists of: Cretaceous carbonates, Jurassic shales and sandstones, and volcanic rocks. The petrographic observation of volcanic rocks indicate the presence of igneous rocks of the andesite, andesite-basalt and basalt types with the main minerals olivine, pyroxene, plagioclase and amphibole, along with biotite and minor and opaque minerals that have a dominant microlitic porphyry and porphyry texture. The results of the chemical analysis of pyroxene phenocrysts indicate the presence of augite-type pyroxenes with a chemical composition spectrum of Fs 12.52-17.38 En 42.71-Wo 36.92-39.67, which were formed in the temperature range of 1200 to 1300 degrees Celsius and a pressure range of 6 to 10 kilobars. The amphiboles are magnesian-hornblende type that crystallized at a pressure of 2.7 to 5 kilobars and a temperature of 720 to 800 degrees Celsius. The micas of this area are primary magmatic magnesian biotites that were formed at a temperature of 580 to 680 degrees Celsius, and the composition of plagioclases fluctuates from oligoclase to labradorite, indicating the crystallization temperature 700-800 degrees Celsius. The combination of mineral chemical analysis data of the Chelwan igneous rocks indicates the tectonic setting of calc-alkaline magmas that formed in a subduction zone.
Keywords

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Volume 19, Issue 38 - Serial Number 38
December 2025
Pages 278-292

  • Receive Date 14 May 2025
  • Revise Date 28 July 2025
  • Accept Date 02 August 2025