A highly residual granulite facies rock (sample RG07‐21) from Lunnyj Island in the Rauer Group, East Antarctica, presents an opportunity to compare different approaches to constraining peak temperature in high‐grade metamorphic rocks. Sample RG07‐21 is a coarse‐grained pelitic migmatite composed of abundant garnet and orthopyroxene along with quartz, biotite, cordierite, and plagioclase with accessory rutile, ilmenite, zircon, and monazite. The inferred sequence of mineral growth is consistent with a clockwise pressure–temperature (P–T) evolution when compared with a forward model (P–T pseudosection) for the whole‐rock chemical composition. Peak metamorphic conditions are estimated at 9 ± 0.5 kbar and 910 ± 50°C based on conventional Al‐in‐orthopyroxene thermobarometry, Zr‐in‐rutile thermometry, and calculated compositional isopleths. U–Pb ages from zircon rims and neocrystallized monazite grains yield ages of c. 514 Ma, suggesting that crystallization of both minerals occurred towards the end of the youngest pervasive metamorphic episode in the region known as the Prydz Tectonic Event. The rare earth element compositions of zircon and garnet are consistent with equilibrium growth of these minerals in the presence of melt. When comparing the thermometry methods used in this study, it is apparent that the Al‐in‐orthopyroxene thermobarometer provides the most reliable estimate of peak conditions. There is a strong textural correlation between the temperatures obtained using the Zr‐in‐rutile thermometer––maximum temperatures are recorded by a single rutile grain included within orthopyroxene, whereas other grains included in garnet, orthopyroxene, quartz, and biotite yield a range of temperatures down to 820°C. Ti‐in‐zircon thermometry returns significantly lower temperature estimates of 678–841°C. Estimates at the upper end of this range are consistent with growth of zircon from crystallizing melt at temperatures close to the elevated (H₂O undersaturated) solidus. Those estimates, significantly lower than the calculated temperature of this residual solidus, may reflect isolation of rutile from the effective equilibration volume leading to an activity of TiO₂ that is lower than the assumed value of unity.

中文翻译：

---

在超高温下测试温度计的保真度

来自南极东部Rauer组的Lunnyj岛的高度残留的花岗石相岩（样品RG07-21）提供了一个机会，可以比较不同的方法来限制高品位变质岩的峰值温度。样品RG07-21是一种粗粒状的云母辉石岩，由丰富的石榴石和邻辉石以及石英，黑云母，堇青石和斜长石与金红石，钛铁矿，锆石和独居石组成。矿物生长的推断序列与顺时针压力-温度（一致P - Ť当与正向模型（比较进化）P - Ť假剖面）。根据常规的Al-邻-邻二甲苯热比重法，Zr-金红石热度法和计算出的组成等值线，估计最高变质条件为9±0.5 kbar和910±50°C。锆石边缘和新结晶的独居石晶粒的U–Pb年龄为c。514 Ma，表明这两种矿物的结晶都发生在被称为普里兹构造事件的区域中最年轻的普遍变质事件的结尾。锆石和石榴石的稀土元素组成与在熔体存在下这些矿物的平衡生长相一致。当比较本研究中使用的测温方法时，很显然，邻邻邻二甲苯基铝气压计提供了最可靠的峰值条件估计值。使用锆金-金红石温度计获得的温度之间存在很强的结构相关性-最高温度由邻辉石中包含的单个金红石晶粒记录，而石榴石，邻辉石，石英和黑云母中包含的其他晶粒产生的温度范围为温度低至820°C。Ti-in-Zircon测温仪得出的温度估计值低得多，为678-841°C。该范围上限的估计值与在接近高温（H₂ O饱和）固相线。这些估计值明显低于该残余固相线的计算温度，可能反映出金红石与有效平衡体积的隔离，导致TiO ₂的活性低于假定的统一值。