Petrology, mineral chemistry, and thermobarometry of the metamorphic rock assemblages in north Azna

Authors

1 Department geology Bu Ali Sina Uni, Hamedan, Iran

2 Professor, department of geology , faculty of sci, Bu-Ali Sina university, hamedan,

3 Assistant professor, department of gelogy , shahid chamran ahvaz, Iran

4 Assistant professor, department of geology of zanjan university, Iran

Abstract

North Azna (the Sanandaj-Sirjan zone) hosts metamorphic complex including slate, phylite, andalsuite staurolite schist, hornfelse, marble and meta-sandstone formed by various metamorphism and deformation phases during subduction of Neo-Tethys beneath in the Jurassic. Electron microprobe analyses show that the garnets are almandine-rich, the biotites are high-Mg, the plagioclases are of albite and the chlorites are Fe-Mg rich. Petrographic observations reveal that the mineral assemblage garnet + staurolite + biotite + andalusite formed in the schists at peak of the regional metamorphism in the middle amphibolite facies. After that and due to intrusion of the granitoid bodies, the second metamorphism phase formed the garnet + biotite + andalusite hornfelse. The rocks subsequently endured retrograde metamorphism caused substitution of the staurolite and andalusite with the biotite + muscovite + chlorite assemblage. The calculated thermodynamic phase diagram show that the regional metamorphism reached 550 °C and 4 kbar at its peak condition. In the contact metamorphism, increasing temperature caused formation of more andaluite in the hornfelses. Although, Al2O3 content of the protolith was not sufficient to form high amounts of andalusite.

Keywords

New Findings in Applied Geology

Articles in Press, Accepted Manuscript
Available Online from 10 July 2024

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History

  • Receive Date: 13 April 2024
  • Revise Date: 25 May 2024
  • Accept Date: 08 July 2024

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