XANES of Ti3+ and Ti4+ in Zircon

The temperature and redox state of magmas are key to understand planetary evolution. The Moon formed via a giant impact onto the proto Earth that has allowed elevated temperature of magma production, of which a critical constraint is the high Ti contents of lunar zircons. Ti has two valance states, Ti3+ and Ti4+, and the retention of Ti in igneous zircons may be affected also by redox state. We have synthesized zircons, and found enhanced Ti solubility at reduced and low temperature conditions. One mechanism for the observation is that, under cool and reduced conditions, Ti3+ is present in appreciable amounts in the system and partitions more into zircon. We plan to test this idea by examining Ti3+ and Ti4+ in zircons from representative runs. The crystal sizes and Ti contents of the zircons require the analyses by synchrotron XANES. The results will be used along with our other trace-elements data in zircons to place new constraints on the thermal state of planetary magmas.