Melt Inclusions in Eclogites from High-Pressure and Ultra-High Pressure Metamorphic Belt in the Dabie Mountains, China

摘要

The eclogites mostly occur as lenses or layers intercalated in the metamorphic supracrustal rocks in the Dabie Mountains, China. Melt inclusions have been discovered for the first time in the eclogites. Petrographical, microthermometric and Raman spectroscopic studies have been made of the inclusions. The melt inclusions are isolated within omphacite, kyanite and cocsite. The homogenization temperatures for the melt inclusions generally vary between 820 and 950 °C. Some inclusions contain two phases, a silicate glass phase and a gas phase in which the dominant gas is CO2, and some three phases with an aqueous solution (15.9 ~ 22.0 Wt%NaCleq), The composition of glass phase from a kyanite eclogite(Sample 1) is close to its host mineral kyanite. HjS and OH" detected by Ramma analyses are respectively molecules and ions in monomer [SiC>4] networks. The glass phase from coesite-bearing eclogite (Sample 4) corresponds to a type of frame [SiOj] network structure, with a composition close to the host mineral coesite. Thus the host minerals possibly crystallized from the melts of corresponding compositions, and the melts are likely of anatexis origin.