Research article Calculating pressure with elastic geobarometry: A comparison of different elastic solutions with application to a calc-silicate gneiss from the Rhodope Metamorphic Province Evangelos Moulas a, ⁎, Dimitrios Kostopoulos b , Yury Podladchikov c,f , Elias Chatzitheodoridis d , Filippo L. Schenker e , Konstantin M. Zingerman f,g , Panagiotis Pomonis b , Lucie Tajčmanová h a Institute of Geosciences, Johannes-Gutenberg University of Mainz, Mainz, Germany b Faculty of Geology and Geoenvironment, Department of Mineralogy and Petrology, National and Kapodistrian University of Athens, Athens, Greece c Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland d Department of Geological Sciences, School of Mining and Metallurgical Engineering, National Technical University of Athens, Athens, Greece e Institute of Earth Science, University of Applied Sciences and Arts of Southern Switzerland (SUPSI), Campus Trevano, Manno, Switzerland f Faculty of Mechanics and Mathematics, Moscow State University, Moscow, Russian Federation g Faculty of Applied Mathematics and Cybernetics, Tver State University, Tver, Russian Federation h Institute of Earth Sciences, Heidelberg University, Heidelberg, Germany abstract article info Article history: Received 6 May 2020 Received in revised form 14 September 2020 Accepted 25 September 2020 Available online 01 October 2020 Keywords: Raman Elastic barometry Quartz-in-Garnet barometry (QuiG) Rhodope Metamorphic Province Eclogite Raman elastic geobarometry has increasingly been used complementary to metamorphic phase equilibria to es- timate the conditions of recrystallization in metamorphic rocks. The procedure of applying Raman elastic barom- etry to host-inclusion mineral systems requires several steps that involve various assumptions. One of the most essential assumptions is that the mineral host-inclusion system behaves in an elastic and reversible manner. We discuss the discrepant results obtained by different authors employing different analytical solutions for elasticity and explore the assumptions lying behind each method. Furthermore, we evaluate numerically linear and non- linear elastic solutions and show their discrepancies. Both formulations are tested against recently published ex- periments on quartz inclusions in garnet (QuiG) at pressures up to 3 GPa, and we find a very good agreement be- tween calculated and experimental pressure values (within 10% relative error). We subsequently apply our new elastic geobarometer to a calc-silicate gneiss from the Rhodope Metamorphic Province (N. Greece). The results of Raman elastic barometry combined with garnet-clinopyroxene geothermometry yield eclogite-facies conditions (~720 ± 40 °C, ~1.5 ± 0.2 GPa). These results are comparable to a high-temperature metamorphic overprint de- duced from phase equilibria modeling in surrounding lithologies (730 ± 40 °C, ~1.2 ± 0.1 GPa). Our findings in- dicate that the estimated pressure from Raman elastic barometry is consistent with a significant viscous relaxation at high temperatures. We conclude that although Raman elastic barometry is a powerful tool for pres- sure estimation in metamorphic rocks, its pressure estimates do not necessarily correspond to entrapment con- ditions. Our results are consequential for the estimates of reaction overstepping in high-grade metamorphic rocks. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Rock microstructures develop as a result of action of physical and chemical processes that take place in response to changing pressure and temperature (P–T) conditions. In addition to geothermobarometry and phase equilibria, which mostly rely on chemical changes, mechani- cal equilibria between different minerals/fluids can also be used to ex- tract information about the P–T conditions prevailing during metamorphic recrystallization. Some of the early applications of me- chanical effects to estimate P–T conditions come from the study of fluid inclusions (e.g. Roedder and Bodnar, 1980). The rationale behind such studies is that, once trapped in a host mineral, a fluid cannot adjust its volume freely, and therefore it will adjust its pressure, thus following a different P–T path compared to its host phase. This principle has not only been applied to fluids and/or melts but also to solid mineral inclu- sions and is commonly referred to as elastic geobarometry or elastic geothermobarometry (e.g. Angel et al., 2015; Enami et al., 2007; Rosenfeld and Chase, 1961; Zhong et al., 2019). The major assumption behind elastic geobarometry is that the host and the inclusion have Lithos 378–379 (2020) 105803 ⁎ Corresponding author. E-mail address: evmoulas@uni-mainz.de (E. Moulas). https://doi.org/10.1016/j.lithos.2020.105803 0024-4937/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos