Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western Turkey
The garnet chemical zoning method (GZM) is a reliable thermodynamic approach for forward modeling pressure-temperature (P-T) paths using observed garnet and bulk rock compositions. However, intracrystalline diffusion is known to compromise the integrity of GZM modeled garnet-growth P-T paths. For th...
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MDPI AG
2021-12-01
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| Series: | Geosciences |
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| Online Access: | https://www.mdpi.com/2076-3263/11/12/505 |
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| author | Thomas M. Etzel Elizabeth J. Catlos |
| author_facet | Thomas M. Etzel Elizabeth J. Catlos |
| author_sort | Thomas M. Etzel |
| collection | DOAJ |
| description | The garnet chemical zoning method (GZM) is a reliable thermodynamic approach for forward modeling pressure-temperature (P-T) paths using observed garnet and bulk rock compositions. However, intracrystalline diffusion is known to compromise the integrity of GZM modeled garnet-growth P-T paths. For this reason, extracting reliable metamorphic estimates from garnet-bearing schists in the Central Menderes Massif (CMM), western Turkey, has been difficult. To evaluate the impact of diffusion on GZM, we simulate garnet growth and diffusion for an average metapelite using the program Theria_G. Modeled garnet compositions from four simulations are used to estimate P-T conditions and paths by GZM, which are compared against Theria_G specified P-T-t trajectories. Factors influencing results are heating/cooling rate, grain size, and peak T. At a maximum T of 610 °C, both undiffused and diffused garnet compositions returned estimates comparable to prescribed conditions regardless of heating/cooling rate. Diffused profiles from simulations reaching a maximum T of 670 °C also reproduced prescribed P-T paths if tectonism occurred at high heating/cooling rates (50 °C/my). From these insights and additional Theria_G simulation-derived observations for CMM garnets, we deduce that metamorphism in the region exceeded 650 °C and achieved a maximum burial P between 8–10 kbar prior to Cenozoic exhumation. |
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| issn | 2076-3263 |
| language | English |
| last_indexed | 2024-03-10T04:01:35Z |
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| spelling | doaj.art-8fc332ca3c7d4e9d9f7f8e231d6d0ba22023-11-23T08:32:28ZengMDPI AGGeosciences2076-32632021-12-01111250510.3390/geosciences11120505Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western TurkeyThomas M. Etzel0Elizabeth J. Catlos1Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 2275 Speedway Stop C9000, Austin, TX 78712, USADepartment of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 2275 Speedway Stop C9000, Austin, TX 78712, USAThe garnet chemical zoning method (GZM) is a reliable thermodynamic approach for forward modeling pressure-temperature (P-T) paths using observed garnet and bulk rock compositions. However, intracrystalline diffusion is known to compromise the integrity of GZM modeled garnet-growth P-T paths. For this reason, extracting reliable metamorphic estimates from garnet-bearing schists in the Central Menderes Massif (CMM), western Turkey, has been difficult. To evaluate the impact of diffusion on GZM, we simulate garnet growth and diffusion for an average metapelite using the program Theria_G. Modeled garnet compositions from four simulations are used to estimate P-T conditions and paths by GZM, which are compared against Theria_G specified P-T-t trajectories. Factors influencing results are heating/cooling rate, grain size, and peak T. At a maximum T of 610 °C, both undiffused and diffused garnet compositions returned estimates comparable to prescribed conditions regardless of heating/cooling rate. Diffused profiles from simulations reaching a maximum T of 670 °C also reproduced prescribed P-T paths if tectonism occurred at high heating/cooling rates (50 °C/my). From these insights and additional Theria_G simulation-derived observations for CMM garnets, we deduce that metamorphism in the region exceeded 650 °C and achieved a maximum burial P between 8–10 kbar prior to Cenozoic exhumation.https://www.mdpi.com/2076-3263/11/12/505garnetthermobarometryMenderes MassifGZMdiffusion modeling |
| spellingShingle | Thomas M. Etzel Elizabeth J. Catlos Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western Turkey Geosciences garnet thermobarometry Menderes Massif GZM diffusion modeling |
| title | Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western Turkey |
| title_full | Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western Turkey |
| title_fullStr | Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western Turkey |
| title_full_unstemmed | Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western Turkey |
| title_short | Garnet Chemical Zoning Based Thermobarometry: Method Evaluation and Applications in the Menderes Massif, Western Turkey |
| title_sort | garnet chemical zoning based thermobarometry method evaluation and applications in the menderes massif western turkey |
| topic | garnet thermobarometry Menderes Massif GZM diffusion modeling |
| url | https://www.mdpi.com/2076-3263/11/12/505 |
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