苏鲁超高压榴辉岩中钾长石的超高压相

在苏鲁超高压榴辉岩中,石榴石和绿辉石包含多种含钾长石的显微多晶包襄体.确定其中的钾长石是否经历过超高压变质不仅有助于限定这些长英质包裹体的成因机制,而且有助于深化理解在超高压变质过程中陆壳岩石的物理和化学行为.榴辉岩B174样品采自于中国大陆科学钻探主孔岩心.该样品的石榴石含多种单相和多相多晶包裹体,其中包括钾长石和方解石单相包裹体、钾长石+石英和钾长石+方解石多晶包裹体.激光拉曼光谱分析揭示了部分钾长石残留有超高压钾长石相--钾质钡铝沸石,表明(1)钾长石至少经历了从钾质钡铝沸石向钾长石的退变质相变;和(2)榴辉岩中含钾长石多晶包裹体形成于超高压变质条件下.

K-cymrite in the Sulu UHP eclogites

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.