K-cymrite in the Sulu UHP eclogites
苏鲁超高压榴辉岩中钾长石的超高压相

Recent studies have shown that both garnet and omphacite in the Sulu ultrahigh-pressure (UHP) eclogites contain various types of polycrystalline K-feldspar-bearing micro-inclusions. Whether K-feldspar within these inclusions had experienced UHP metamorphic reactions or not is a key question. Answers to this question could not only provide tight constraints on the formation mechanisms for the quartzo-feldspathic inclusions in mafic eclogites, but also help to promote understandings on the physical and chemical behaviors of continental crustal rocks during UHP metamorphism. Eclogite sample B174 was collected from the main borehole of the Chinese Continental Scientific Drilling Project (CCSD). Garnets from this sample contain a number of single-phase and polyphase polycrystalline inclusions including K-feldspar and calcite single-phase inclusions, K-feldspar+quartz and K-feldspar+calcite polycrystalline inclusions. Laser Raman Spectroscopy analyses show that part of the K-feldspar grains within these inclusions contains K-cymrite, a UHP phase of K-feldspar. This result indicates that (1) K-feldspar grains within these inclusions are polymorph after K-cymrite; and (2) K-feldspar-bearing inclusions in the Sulu eclogites formed at UHP conditions.