Refractory Minerals — Archives from the Early Solar System

Refractory inclusions, though a minor component of chondritic meteorites, are the oldest solids formed in the Solar System. Composed of minerals that were among the first to condense from a solar-composition gas, their textures, mineralogy, and isotopic compositions reveal formation under diverse physicochemical conditions and subsequent processing—such as condensation, melting, and melt distillation. These early Solar System materials record both mass-dependent fractionation and large mass-independent isotopic anomalies in nuclides such as ⁴⁸Ca and ⁵⁰Ti, offering critical insights into stellar nucleosynthetic sources and nebular evolution.

In addition to nucleosynthetic signals, cosmogenic nuclides including ¹⁰Be, ³He, and ²¹Ne preserved in refractory minerals reflect interactions with energetic particles from the young, highly active Sun. Astronomical observations of young stellar objects suggest intense particle fluxes during the Sun’s early evolution, but meteoritic evidence remains the only direct record of this early irradiation environment. This thesis aims to bridge laboratory measurements with astrophysical models to constrain the irradiation and transport history of early Solar System solids.

I developed a new technique to combine SIMS and noble gas mass spectrometry on the same mineral grains by physically transferring samples between mounts. Applying this to hibonite and spinel inclusions, I measured isotopic systems including O, Al–Mg, Ca–Ti, and noble gases. The results show elevated ²¹Ne concentrations consistent with early solar cosmic ray (SCR) exposure. Coupled with disk transport modeling, these data constrain the young Sun’s particle flux to be up to 10⁷ times higher than today.

This thesis also examines isotopic diversity among CAIs and investigates the origin of isotopic anomalies in the Solar System and the evolution of isotopic reservoirs in the solar nebula. Together, these studies provide new constraints on early solar activity, mass transport, and the isotopic evolution of the protoplanetary disk.