Response to the Comment by S.B. Simon, L. Grossman, and S.R. Sutton on "Valence state of titanium in the Wark-Lovering rim of a Leoville CAI as a record of progressive oxidation in the early Solar Nebula"

Abstract

S. Simon et al. incorrectly suggest that in earlier work we claimed there was no Ti3+ in Wark-Lovering rim pyroxenes. In neither the paper by Simon et al. (2005) nor the subsequent paper by Dyl et al. (2011) did we assert that there was no Ti3+ in rim pyroxenes. Rather, we found that many pyroxenes have Ti3+ below detection while others have lower Ti3+/Ti4+ than is typical of CAI interiors, indicating rim formation in a relatively oxidizing environment. Dyl et al. (2011) showed through exhaustive testing that the suggestion by Simon et al. (2007) that EMPA data in the paper by Simon et al. (2005) were flawed is incorrect. Here we consider each point raised in the comment by S. Simon et al. and reiterate that our electron microprobe data and the XANES data of Simon et al. (2007) agree and demonstrate a statistically significant (~2σ) or greater difference between rim and interior pyroxene Ti3+/Ti4+. We show that the oxidation states of Ti in Wark-Lovering rim pyroxenes, the chemistry of rim pyroxenes, and the modal abundances of rim minerals are best explained by reaction between the CAI and gas that was orders of magnitude more oxidizing than the solar-like gas from which the CAIs originally formed.