Mineral chemistry and geothermobarometry of adakitic rocks from Kashan, central Urumieh-Dokhtar magmatic arc, Iran: implications for magma evolution
Year: 2025
Type: article
Abstract: The Kashan region is located in the central part of the Urumieh-Dokhtar magmatic Arc (UDMA). In this area, Miocene adakitic rocks, including andesites and rhyodacites, occur as lava flows and domes. The primary mineral assemblages consist of amphibole, biotite and plagioclase, with minor alkali feldspar. Mineral chemistry analyses reveal that plagioclase compositions from andesine to oligoclase, amphiboles vary from Mg-hastingsite, tschermakite to Mg-hornblende, and biotites span from annite to phlogopite. Amphiboles show high Fe³+/(Fe³++Fe²+) ratios, whereas magmatic biotites in rhyodacites exhibit low total Al and narrow Fe/(Fe+Mg) ratios, indicative of relatively oxidizing conditions. Oxygen fugacity (ƒO2) values range from 10-10.4 bar (ΔNNO+0.75, representing nickel-nickel oxide) in andesites to 10-12.3 bar (ΔNNO+1.7) in rhyodacites. Application of the calcic amphibole geothermobarometer indicates that amphiboles crystallized at temperatures of 791-986 °C and pressures of 620-800 MPa in andesites, and at 636-850 °C and 250-450 MPa in rhyodacitic rocks, corresponding to maximum crustal depths of 28 km. Primary biotites in rhyodacites crystallized slightly later at temperatures of 690-784 °C (average 712 °C).
Authors: Khaksar, Tayebeh, Davoudian, Ali Reza, Moradi, Sakine, Shabanian, Nahid, Song, Shu -Guang
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6941094213
FWCI:
Cites:
Cited by:
Related to: