Ultra-high temperature (UHT) granulite-facies metamorphism is commonly identified in Mg–Al-rich rocks. Many such lithologies are thought to be metasedimentary rocks based on the presence of detrital zircon. However, whether a metasedimentary protolith is required to form diagnostic mineral assemblages and how much melt is lost during burial and heating to reach UHT conditions varies significantly according to the prograde pressure–temperature path. In this study, integrated thermodynamic modeling, accessory mineral modeling, and trace element modeling has been conducted on an average metapelite composition and average mid-ocean ridge basalt (MORB) composition under open-system conditions. The results show at least three and two melt loss events occur before reaching UHT conditions in initially water-saturated pelitic and basaltic rocks, respectively. Around 22–27 vol% S-type granite and 12–17 vol% I-type granite would be produced during these evolutions, respectively. Melt extraction leads to an increase of Al and Mg in metapelite residua. Mineral assemblage sapphirine + quartz is then allowed to form at higher grades; however, metabasalt does not form these UHT diagnostic assemblages, regardless of the amount of melt lost. During equilibrium melting, crustal differentiation induced by UHT metamorphism would significantly reduce the amount of heat-producing elements (HPEs) in the melt-depleted residuum, which progressively decreases a rock's heat production capacity. In reality, however, new monazite grains likely form during peak metamorphism and some monazite grains would be shielded by porphyroblasts, resulting in an increase of Th in the residua during heating. Even so, we suggest the efficiency of heat production would still decrease, given the heat production rate of Th is much lower than U. Considering some granitic rocks with relatively high heat production are emplaced into the granulite terrane, we suggest that radioactive heat production may be a contributing driving force for UHT metamorphism; however, it is not sufficient. Most heat required to generate UHT granulites must come from hybrid sources, such as advected heat from the mantle, conducted heat from nearby magmatic intrusions, radioactive heat production, and ductile shear deformation.

超高温 (UHT) 麻粒岩相变质作用通常在富镁铝岩石中发现。许多此类岩性被认为是基于碎屑锆石的变质沉积岩。然而，是否需要变质沉积原岩来形成诊断矿物组合以及在埋藏和加热过程中损失了多少熔体以达到 UHT 条件，根据压力-温度的前进路径而有很大差异。在这项研究中，对开放系统条件下的平均变泥质岩成分和平均洋中脊玄武岩 (MORB) 成分进行了综合热力学建模、副矿物建模和微量元素建模。结果表明，在最初含水饱和的泥质岩和玄武岩中，在达到 UHT 条件之前，至少发生了 3 次和两次熔融损失事件，分别。在这些演化过程中，将分别产生大约 22-27 vol% 的 S 型花岗岩和 12-17 vol% 的 I 型花岗岩。熔体萃取导致变泥质残渣中铝和镁的增加。然后允许形成更高等级的矿物组合蓝宝石 + 石英；然而，无论熔体损失多少，变玄武岩都不会形成这些 UHT 诊断组合。在平衡熔融过程中，超高温变质作用引起的地壳分异会显着减少熔融贫化残余物中的产热元素（HPE）的数量，从而逐渐降低岩石的产热能力。然而，实际上，在峰值变质作用期间可能会形成新的独居石颗粒，并且一些独居石颗粒会被卟啉母细胞屏蔽，导致加热过程中残留物中的 Th 增加。尽管如此，鉴于 Th 的产热率远低于 U，我们认为产热效率仍会下降。考虑到一些产热相对较高的花岗岩被置于麻粒岩地体中，我们认为放射性产热可能是一个贡献UHT变质的驱动力；然而，这还不够。产生 UHT 麻粒岩所需的大部分热量必须来自混合来源，例如来自地幔的平流热量、来自附近岩浆侵入体的传导热量、放射性热量产生和韧性剪切变形。我们认为放射性热的产生可能是 UHT 变质作用的推动力；然而，这还不够。产生 UHT 麻粒岩所需的大部分热量必须来自混合来源，例如来自地幔的平流热量、来自附近岩浆侵入体的传导热量、放射性热量产生和韧性剪切变形。我们认为放射性热的产生可能是 UHT 变质作用的推动力；然而，这还不够。产生 UHT 麻粒岩所需的大部分热量必须来自混合来源，例如来自地幔的平流热量、来自附近岩浆侵入体的传导热量、放射性热量产生和韧性剪切变形。