The concentrations of helium and carbon in fluorite associated with Cretaceous to Neogene (90-13 Ma) granitic magmatism in the Japanese arc have been measured. Concentrations of Li, U, Th and Gd were measured to correct for secondary generated 3He. The CO2/3 He of fluorites are almost uniform (1.5 x 1010 -4 x 1010) and in fair agreement with the range of present island arc volcanic gases. The calculated mantle C contribution in the Mesozoic subduction zone appear to have been identical to the present one (7-19%) indicating that the C flux from the mantle in supra-subduction zone environments has remained fairly constant during the past 70 million years.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology