March, S.Hand, M.Morrissey, L.Kelsey, D.2025-05-022025-05-022025Scientific Reports, 2025; 15(1):3038-1-3038-142045-23222045-2322https://hdl.handle.net/2440/144376It is well recognised that endothermic processes such as dehydration and partial melting have the potential to exert measurable effects on the maximum temperatures reached in metamorphic rock systems. We show migmatitic metapelitic and mafic granulites record temperatures of ~820 °C, while spatially associated refractory Mg–Al-rich granulites record temperatures between 865 °C and >920 °C. These thermally contrasting samples are separated by ~1500 m, with no apparent intervening faults or shear zones to explain the apparent difference in peak metamorphic conditions. Temperature versus enthalpy modelling of these samples along simple prograde P–T paths imply migmatisation slows the rate of temperature increase relative to rocks that do not melt. We speculate refractory rocks in the present study are created through early hydrothermal alteration and metamorphism, resulting in melt-resistant bulk compositions. There are many potential geological contexts where neighbouring rocks may have contrasting melt fertility; the deposition of a cover sequence, pre-metamorphic alteration, and the intrusion of igneous protoliths are all possibilities. With this in mind, variations in maximum modelled temperatures in granulite facies domains should be relatively common.en© The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommo ns.org/licenses/by-nc-nd/4.0/.EnthalpyGranulite facies metamorphismMigmatitePhase diagramThermal bufferingJournal article10.1038/s41598-025-87496-5726999March, S. [0000-0002-5909-1280]Hand, M. [0000-0003-3743-9706]Morrissey, L. [0000-0001-7506-6117]