The peak temperature and duration of ultrahigh-temperature (UHT) metamorphism are critical to identify and understand its tectonic environment. The UHT metamorphism of the Jining complex in the Khondalite Belt, North China Craton is controversial on the peak temperature, time and tectonic setting. A representative sapphirine-bearing granulite sample is selected from the classic Tianpishan outcrop for addressing the metamorphic evolution and timing. The rock is markedly heterogeneous on centimeter scale and can be divided into melanocratic domains rich in sillimanite (MD-s) or rich in orthopyroxene (MD-o), and leucocratic domains (LD). On the basis of detailed petrographic analyses and phase equilibria modelling using THERMOCALC, all the three types of domains record peak temperatures of 1120–1140 °C and a series of post-peak cooling stages at 0.8–0.9 GPa to the fluid-absent solidus (∼890 °C), followed by sub-solidus decompression. The peak temperature for MD-s is constrained by the coexistence of sillimanite-I + sapphirine + spinel + quartz, where sillimanite-I contains densely exsolved aciculae of hematite, yielding reintegrated Fe₂O₃ contents up to 2.1–2.3 wt %. The post-peak cooling evolution involves the sequential appearance of K-feldspar, sillimanite-II + garnet, orthopyroxene and biotite, where sillimanite-II is exsolution-free and contains variable Fe₂O₃ contents of 1.3–1.8 wt %. The peak temperature for MD-o is constrained by the sapphirine + orthopyroxene assemblage, where orthopyroxene has a maximum Al^IV of 0.22 (Al₂O₃ = 9.5 wt %) in the core. The cooling evolution involves the sequential appearance of K-feldspar, garnet and biotite, and the decreasing Al^IV (0.22→0.17) from core to rim in orthopyroxene. The peak temperature for LD is constrained by the inferred K-feldspar-absent assemblage and the maximum anorthite content of 0.11 in K-feldspar. The cooling evolution involves the crystallization of segregated melts, exsolution of supra-solvus ternary feldspars and growth of biotite. The Al in orthopyroxene, Fe₂O₃ in sillimanite and anorthite in K-feldspar are good indicators for constraining extreme UHT conditions although they depend differently on bulk-rock compositions. In-situ SHRIMP U–Pb dating of metamorphic zircon indicates that the UHT metamorphism may have occurred at > 1.94 Ga and the cooling under UHT conditions lasted over 40 Ma. The extreme UHT metamorphism in the Jining complex is interpreted to be triggered by the advective heating of intraplate hyperthermal mafic magmas together with a plume-related hot mantle upwelling, following an orogenic crustal thickening event.

中文翻译：

---

UHT变质作用在缓慢冷却下达到1100°C以上的峰值：来自华北克拉通济宁复杂地区的胶状花岗岩

峰值温度和超高温（UHT）变质的持续时间对于识别和了解其构造环境至关重要。华北克拉通（Khontonlite Belt）济宁石带济宁复合体的UHT变质作用在峰值温度，时间和构造环境方面存在争议。从经典的天pi山露头中选出代表性的含蓝宝石的花岗石样品，以解决变质作用的演化和时机问题。岩石在厘米尺度上具有明显的非均质性，可以分为富含硅线石（MD-s）或富含邻苯二茂铁（MD-o）的黑克拉通域和白垩纪域（LD）。在使用THERMOCALC进行详细的岩石学分析和相平衡建模的基础上，所有这三种类型的畴都记录了1120–1140°C的峰值温度以及在0时的一系列峰后冷却阶段。到无流体的固相线（约890°C）为8–0.9 GPa，然后进行亚固相线减压。MD-s的峰值温度受到硅线石-I +蓝宝石+尖晶石+石英的共存的限制，其中硅线石-I包含浓溶的赤铁矿针孔，产生重新整合的铁₂ O ₃含量最高为2.1–2.3 wt％。峰后冷却过程涉及到钾长石，硅线石-II +石榴石，邻位辉石和黑云母的相继出现，其中硅线石-II不存在脱溶现象，其Fe ₂ O ₃含量为1.3-1.8 wt％。MD-o的峰值温度受到蓝宝石+邻苯二酚组合的限制，其中邻苯二酚在芯中的最大Al ^IV为0.22（Al ₂ O ₃ = 9.5 wt％）。冷却过程涉及钾长石，石榴石和黑云母的相继出现，以及铝^IV的减少（0.22→0.17）从邻苯二酚的芯到边缘。LD的峰值温度受推测的无钾长石的组合和钾长石中最大的钙长石含量0.11的限制。冷却过程涉及偏析熔体的结晶，超溶剂三元长石的析出和黑云母的生长。邻二甲苯中的Al，Fe ₂ O ₃钾长石中硅线石和钙长石中的硅酸盐是约束极端超高温条件的良好指标，尽管它们对块状岩石成分的依赖不同。变质锆石的原位SHRIMP U–Pb测年表明，UHT变质可能发生在> 1.94 Ga处，并且在UHT条件下的冷却持续了40 Ma以上。济宁复杂的极端UHT变质被解释为是由于造山带地壳增厚事件之后，板内高温镁铁质岩浆的对流加热以及与羽流有关的热地幔上升。