Abstract
Marschall et al. (2006) estimated Li/B ratio in greenschists, blueschists, eclogites based on the chemical and modal compositions of main constituent minerals in relevant rocks. These data suggest that Li/B ratio in the hydrated fluid increases from 0.25 to 0.55 with the depths of metamorphic reactions taken place. These data suggest that Li/B ratio becomes a potential tool as an indicator of the generated depth of deep fluids. To verify this idea, we carried out microthermometry and Raman spectroscopy for fluid inclusions in quartz veins/lenses crystallized from 20 to 60 km depths in the Sanbagawa belt, Japan. We further performed Li and B analyses using ICP-MS for extracted fluids from quartz veins/lenses by the crush leaching technique. As a result, although the extracted fluids certainly are the mixture of multi-stages deep fluids, Li/B ratios of them increase with the metamorphic grade of the host rocks from 0.020 to 0.271.
