[LPT] Granulite thermobarometry with Al in orthopyroxene


EN | In the world of high-grade metamorphic rocks, things can get a little tricky: from element compatibility, closure temperatures from chemical systems and migmatite field structures. One process that may occur is the late Fe-Mg exchange between minerals such as orthopyroxene, garnet and biotite. Our post shares how Pattison et al. (2003) found a solution for this problem considering the orthopyroxene Al-solubility in granulite PT estimates; and even created an online software – RCLC.


PT | No mundo das rochas de alto grau, as coisas podem ficar “divertidas”: de compatibilidade de elementos e temperaturas de fechamento de sistemas químicos, até estruturas migmatíticas lindas e complexas em campo. Como essa complexidade afeta estimativas P-T em granulitos? Uma das maneiras é na troca tardia de Fe e Mg em minerais como ortopiroxênio, granada e biotita. Confira no post como Pattison et al. (2003) pensaram em uma solução para esse problema e até criaram um programa online para estimativas PT em granulitos com base na solubilidade de alumínio (Al) no ortopiroxênio – o RCLC.


Author: Lucas Schiavetti

References

  • Pattison, D.R.M., Chacko, T., Farquhar, J. & McFarlane, C.R.M. (2003) Temperatures of granulite facies metamorphism: constraints from experimental phase equilibria and thermobarometry corrected for late Fe-Mg exchange. Journal of Petrology, 44, 867-900. https://doi.org/10.1093/petrology/44.5.867
  • Pattison, D.R.M., Chacko, T., Farquhar, J., McFarlane, C.R.M., Widney, J. (2019). Program “RCLC”: Garnet-Orthopyroxene Thermobarometry Corrected for Late Fe-Mg Exchage. Journal of Petrology, 60(5), 1107-1108 https://doi.org/10.1093/petrology/egz018
  • Rocha, B. Moraes, R., Möller, A., Cioffi, C.R. (2018). Magmatic inheritance vs. UHT metamorphism: Zircon petrochronology of granulites and petrogenesis of charnockitic leucosomes of the Socorro-Guaxupé nappe, SE Brazil. Lithos, 314-315, 16-39. https://doi.org/10.1016/j.lithos.2018.05.014
  • Tesser, L.R., Ganade, C.E., Weinber, R.F., Basei, M.A.S., Moraes, R., Batista, L.A. (2021). Ultrahigh-temperature Paleoproterozoic rocks in the Neoproterozoic Borborema Province, implications for São Francisco Craton dispersion in NE Brazil. Journal of Metamorphic Geology, 40,359-387. https://doi.org/10.1111/jmg.12632

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