Using mineral chemistry in thermobarometry and thermo-oxybarometry of Fe-Ti±P host mafic-ultramafic rocks in the XV deposit (Bafq area, Central Iran): Implications for Tectonic Setting and Nature of the Magma

Articles in Press

Document Type : Research Paper

Authors

1 Department of geology of ore minerals and groundwater resources, Shahid Beheshti University, Tehran, Iran

2 Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran

3 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China

4 School of Earth Sciences and Resources, Chang’an University, Xi’an, China

5 Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, NV 89154, USA

6 Instituto de Geología Económica Aplicada (GEA), Universidad de Concepción, Casilla 160–C, Concepción, Chile

Abstract

The Fe–Ti ± P oxide mineralization hosted by the XV intrusion is located within the Bafq–Saqand metallogenic province in western Central Iran. This mineralization occurs in gabbroic and pyroxenitic rocks and appears in semi-massive, net-textured, and disseminated forms. According to the Ti + Cr + Na versus Al discrimination diagram, the analyzed pyroxenes are of igneous origin. Classification on the Q (Ca + Mg + Fe2+) versus J (2Na) diagram places them within the Ca–Fe–Mg pyroxene group (Quad). The average Mg# [Mg/(Mg + Fe2+) × 100] values are 87.23 wt.% for gabbroic and 84.20 wt.% for pyroxenitic pyroxenes. CaO contents range from 13.30 to 23.00 wt.% in gabbroic samples and from 18.52 to 23.12 wt.% in pyroxenitic rocks. In the Ca + Na(B) (a.p.f.u) versus Na(B) (a.p.f.u) diagram, the studied amphiboles are classified as calcic. Thermobarometric calculations indicate that the gabbros crystallized at temperatures between 904–1230 °C under pressures of 8.0–10.3 kbar, whereas the pyroxenites formed under slightly lower thermal conditions (901–1180 °C) and pressures from 7.0 to 8.9 kbar. Coexisting titanomagnetite–ilmenite mineral pairs record cooling temperatures ranging from 448 °C to 727 °C, mainly within 554–645 °C, with oxygen fugacity (ƒO2) values from –17.28 to –23.96. The relatively high ƒO2 values suggest that the parental magma evolved under oxidizing conditions, likely associated with an extensional tectonic setting during emplacement, cooling, and fractional crystallization.

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Geopersia

Articles in Press, Accepted Manuscript
Available Online from 21 December 2025

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History

  • Receive Date: 10 August 2025
  • Revise Date: 01 December 2025
  • Accept Date: 21 December 2025

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