Abstract
Oxygen isotopic compositions formed by non-mass dependent fractionation processes have been widely observed in calcium-aluminium rich inclusions (CAIs) and chondrules produced in the early solar nebula. So far, only photodissociation has been known to produce non-mass dependent oxygen isotopic fractionation. Therefore, the reason for the oxygen isotopic compositions of CAIs and chondrules has been discussed based on an ultraviolet photodissociation process of carbon monoxide in solar nebula. Recently, we found that electrical discharge can produce non-mass dependent oxygen isotopic fractionation in refractory oxide grains. Presolar silicate materials, which are an important reservoir of oxygen in the early solar nebula, are believed to have been produced in high-temperature regions prior to the formation of the solar nebula. Our results may provide another possible path, caused by the processing of presolar silicate materials and leading to the non-mass dependent oxygen isotopic fractionation of CAIs and chondrules.
