摘要
Unusual polyphase inclusions of K-feldspar+quartz+titanite+solid salt and K-feldspar+albite+quartz+epidote with textures similar to the other K-feldspar+quartz inclusions were found in omphacite grains from the Sulu ultrahigh pressure (UHP) eclogites. One of these inclusions contain square to round solid salt inclusions of KCl-NaCl composition. Such a mineral assemblage within K-feldspar-bearing inclusions hosted by UHP metamorphic phases suggests that (1) potassium granitic melts enriched in Cl components were presented during UHP metamorphism or at the early stage of rapid exhumation of deeply subducted continental slab; (2) they were resulted from reactions between the incoming granitic melts and quartz (or coesite); and (3) solid salt inclusions of NaCl-KCl were derived from dehydration and desiccation of Cl-bearing melts. Our new observations further demonstrate that during the tectonic evolution of UHP rocks, fertile components within deeply subducted continental materials could undergo partial melting, leading to the formation of Cl-bearing potassium granitic melts and substantial migration of fluid-conservative elements (e.g. Ti, Hf) within the UHP slab.
Unusual polyphase inclusions of K-feldspar ＋ quartz ＋ titanite ＋ solid salt and K-feldspar ＋ albite ＋ quartz ＋ epidote with textures similar to the other K-feldspar ＋ quartz inclusions were found in omphacite grains from the Sulu ultrahigh pressure （UHP） eclogites. One of these inclusions contain square to round solid salt inclusions of KCI-NaC1 composition. Such a mineral assemblage within K-feldspar-beating inclusions hosted by UHP metamorphic phases suggests that （1） potassium granitic melts enriched in C1 components were presented during UHP metamorphism or at the early stage of rapid exhumation of deeply subducted continental slab; （2） they were resulted from reactions between the incoming granitic melts and quartz （or coesite）; and （3） solid salt inclusions of NaCI-KCI were derived from dehydration and desiccation of Cl-bearing melts. Our new observations further demonstrate that during the tectonic evolution of UHP rocks, fertile components within deeply subducted continental materials could undergo partial melting, leading to the formation of Cl-bearing potassium granitic melts and substantial migration of fluid-conservative elements （e.g. Ti, Hf） within the UHP slab.
基金
supported by the SinoProbe Project (SinoProbe-2-6)
the National Natural Science Foundation of China (41073024 and 40872048)
关键词
超高压榴辉岩
超高压变质
钾长石
柯石英
固体盐
氯化钠
包裹体
多相
quartzo-feldspathic polyphase inclusions
solid salt inclusion
eclogite
ultrahigh-pressure metamorphism
Sulu UHP belt
