Petrography, mineral chemistry and geothermobarometry of monzogabbro-monzodiorite intrusions of N-NE Bafq: An approach to understanding of the Ediacaran-Cambrian intracontinental rift in the central part of Iran

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Document Type : Research Paper

Authors

1 Petrology and Economic Geology Department, Shahrood University of Technology, Shahrood, Iran

2 Department of Mineralogy-Petrology-Economic Geology, School of Geology, Aristotle University, Greece

3 Institute of Geology and Geophysics, Chinese Academy of Sciences (CAS), China

Abstract

The study area is located in the N-NE Bafq and the central Iran structural zone. The Rizu-Desu volcano-sedimentary sequence is crosscut by bimodal (basic and felsic) intrusions and dikes, with compositions ranging from monzogabbro to leucogranite. In the monzogabbro-monzodiorite intrusions (540 to 520 Ma) of the investigated region, plagioclase (with a dominant albite-oligoclase composition), pyroxene (diopside and augite), Ca-Fe-Ti-rich amphiboles (magnesiohornblende, tschermakite, Kaersutite, and ferrokaersutite), and biotite (Fe-biotite and Mg-biotite, and also Ti-rich (0.38-1)) are the essential minerals. Apatite, monazite, magnetite, titanomagnetite, titanite (sphene), and zircon are also accessory minerals. Geothermobarometry investigations based on the mineral chemistry of pyroxene, amphibole, and biotite indicate the temperatures of cessation of exchange and final equilibrium of the minerals, mainly covering a temperature range of 1270 to 1140 °C (pyroxenes), 890-790 °C (amphiboles) and 780-745 °C (biotites) (in respectively) and the pressure mainly cover range of 12.33 to 0.5 kbar. Petrological features of the studied rocks are very similar to those of appinite rocks. The parental magmas of monzogabbro-monzodiorite intrusions have mostly an alkaline nature and originated from partial melting of the metasomatized mantle source in an intracontinental rift tectonic setting. The resulting magmas evolved by fractional crystallization, and possibly crustal contamination, then emplaced in the continental crust around the Ediacaran-Cambrian boundary.

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Article Title [Persian]

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Abstract [Persian]

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Geopersia

Articles in Press, Accepted Manuscript
Available Online from 14 July 2025

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History

  • Receive Date: 21 April 2025
  • Revise Date: 10 June 2025
  • Accept Date: 14 July 2025

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