The data collected during my NASA Earth and Space Science Fellowship has provided new insights into the formation and evolution of the early Solar System. In this study, I developed methods to precisely analyze the titanium isotopic composition of calcium-aluminum-rich inclusions (CAIs) using laser ablation multi-collector inductively coupled plasma mass spectrometry. My work here led to the discovery of a new and rare type of CAI characterized by a large mass-independent 46Ti and 50Ti anomalies and is identified as having Fractionation and Unidentified Nuclear (FUN) effects. Detailed analysis of this inclusion along with laboratory evaporation experiments demonstrate that melting of its precursor material under nebular conditions was accompanied by surface evaporative loss of moderately volatile elements (greater than 80% of silicon and 90% of magnesium) resulting in a present-day composition very distinct from that of the original precursor condensate. These results suggest that large degrees of chemical fractionation occurred in the nebula via condensation and evaporation processes within the first few million years of Solar System history. Additionally, the chemical and isotopic differences between normal and FUN CAIs places further constraints on the physio-chemical structure of the protoplanetary disk as well as processes associated with the heating and transport of materials that coalesce into planetesimals and eventually larger planetary bodies.
Williams C. D., Ushikubo T., Janney P. E., Kita N. T., Bullock E. S., Hines R. R., MacPherson G. J., Hervig R. L., Wadhwa M. (2016) Thermal and chemical evolution of the early Solar System as recorded by FUN CAIs: Part I – Petrology, mineral chemistry, and isotopic composition of Allende FUN CAI CMS-1. Geochimica et Cosmochimica Acta 201, 25-48. doi.org/10.1016/j.gca.2016.10.053. [PDF]
Mendybaev R. A., Williams C. D., Spicuzza M. J., Richter F. M. Valley J. W., Wadhwa M. (2016) Thermal and chemical evolution in the early Solar System as recorded by FUN CAIs: Part II – Laboratory evaporation of potential CMS-1 precursor material. Geochimica et Cosmochimica Acta 201, 49-64. doi:10.1016/j.gca.2016.08.034. [PDF]
Williams C. D., Janney P. E., Hines R. R.,Wadhwa M. (2016) Precise titanium isotope compositions of refractory inclusions in the Allende CV3 chondrite by LA-MC-ICPMS. Chemical Geology 436, 1-10. doi:10.1016/j.chemgeo.2016.04.021. [PDF]