We present textural evidence of spinel (low-Zn) and quartz from two samples of quartzofeldspathic rocks from the Larsemann Hills, East Antarctica. The present occurrence is unusual for the fact that the direct grain contact is preserved unlike most other occurrences where these two phases are separated by reaction products during retrograde and/or prograde metamorphic stages. Textural features further indicate that Ti-biotite was part of the prograde assemblage that underwent partial melting to produce spinel. The maximum temperature estimated from the rock is 870 °C. Monazite grains are abundant in the rock and these are mostly homogeneous in terms of U, Th and Pb distribution. In situ U–Th-total Pb EPMA data of these monazite yield a group age of 527 ± 8 Ma. Textural and geochronological data match with the second (M₂) stage of metamorphism of the Larsemann Hills region as evident from the existing geological record. Although spinel and quartz was considered to be a part of peak M₂ assemblage in earlier studies, preservation of their grain contact is enigmatic. We consider the grain contact metastable and its preservation possibly resulted from significant overstepping of cooling reaction due to fast reaction kinetics.

我们提供了来自南极东部拉尔瑟曼山的两个石英长石岩石样品的尖晶石（低锌）和石英的结构证据。当前的情况是不寻常的，因为与大多数其他情况不同，保留了直接的谷物接触，在逆行和/或顺行变质阶段，这两个相被反应产物隔开。织构特征进一步表明，钛黑云母是部分经历熔融生成尖晶石的前级组合的一部分。岩石估计的最高温度为870°C。独居石颗粒在岩石中含量丰富，就U，Th和Pb的分布而言，它们大多是均匀的。这些独居石的原位U-Th-总Pb EPMA数据表明该群年龄为527±8 Ma。质地和年代学数据与第二（M ₂从现有的地质记录中可以明显看出，Larsemann Hills地区的变质阶段。尽管在较早的研究中尖晶石和石英被认为是M ₂峰集合的一部分，但保持其晶粒接触仍然是个谜。我们认为晶粒接触是亚稳态的，其保存可能是由于快速反应动力学导致的冷却反应明显超速进行的结果。