Advanced Applied Geology

Advanced Applied Geology

Geochemistry and thermometry of chlorite in metamorphic and igneous rocks from north Azna, Sanandaj–Sirjan Zone

Authors
Mahsa Tahmasebi 1
Aliasghar Sepahi
Mirmohammad Miri 2
Javad Izadyar 3
1 Department of Geology, Faculty of sciences, Bu-Ali Sina University, Iran
2 Department of Geology, Faculty of Earth sciences, Shahid Chamran University of Ahvaz, Iran
3 Department of Geology, Faculty of sciences, Zanjan University, Iran
10.22055/aag.2025.50243.2526
Abstract
The present study focuses on the geochemical characteristics and chlorite thermometry in metamorphic and igneous rocks of the Azna region, located within the Sanandaj–Sirjan Zone. Chlorite occurs in regionally metamorphosed rocks) e.g., phyllites and schists(, contact metamorphic rocks )e.g., certain hornfelses(, and dynamically metamorphosed rocks )e.g., mylonitic granites(. In schists and phyllites, the chlorite exhibits progressive growth and is sometimes formed through retrograde metamorphism of minerals like staurolite. In mylonites, it typically results of the biotite instability. Microprobe and X-ray diffraction )XRD( analyses reveal that the type and chemical composition of chlorite vary across the studied rocks. The chlorites in schists and hornfelses contain higher amounts of Fe and Mg compared to those in metagranites and granites. The chemical composition of chlorite in various schists corresponds to Fe-rich clinochlore, cronstedtite, and amesite, while in granite mylonites, clinochlore, ripidolite, chamosite, and daphnite are identified. Thermometric studies indicate that chlorite formed at approximately 285°C in metapelites and around 260 °C in granite mylonites. These findings suggest that, as expected, chlorite in both progressive and retrograde conditions formed under greenschist facies metamorphic conditions.
Keywords
Thermometry
Progressive
Retrogressive
Green schist
Chlorite
Subjects
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Advanced Applied Geology
Volume 15, Issue 3
Autumn 2025
Pages 142-169