Thermal processing chondrules

Davis AM, MaePherson GJ (1996) Thermal processing in the solar nebula Constraints from refractory inclusions. In Chondrules and the Protoplanetary Disk. Hewins RH, Jones RH, Scott ERD (eds) Cambridge University Press, New York, p 71-76... 

To summarize, chondrules and CAIs formed by transient heating events that processed a large fraction of the matter in the accretion disk. These heating events appear to overprint the thermal processing that produced the volatile element depletions among chondrites. The exact nature of these events is unknown, although shock waves in the nebula and the X-wind model are currently receiving the most attention. 

Desch, S. J. and Connolly, H. C. (2002) A model of the thermal processing of particles in solar nebula shocks application to the cooling rates of chondrules. Meteoritics and Planetary Science, 37, 183-207. 

Most non-chondrule solids in the inner Solar System experienced thermal processing (see Chapter 8) that could have modified their initial oxygen isotopic composition (Yurimoto Kuramoto 2004). The complicated structure of meteoritic oxygen isotopes is difficult to reproduce simply by physical mixing of different reservoirs. Apart from thermal processing (e.g. melting, vaporization, condensation), a large mass-independent chemical process is required. The exact mechanism for this likely photochemical process is yet unknown, but the available constraints leave only a few pathways open. 

This indicates that the volatility fractionations affecting silicates and metal occurred under different conditions. Since chondrites are sedimentary rocks consisting largely of chondrules that were melted and rapidly cooled in zero gravity, the volatility depletions in bulk chondrites almost certainly arose in the nebula, likely during the thermal processing events that melted chondrules (see Chapters 7 and 8). 

Perhaps the most well-known, unsolved problem in cosmochemistry is the question of the mechanism whereby dust grain aggregates were thermally processed to form chondrules and some rounded refractory inclusions. Chondrule compositions and textures require rapid heating and somewhat slower cooling for their explanation a globally hot nebula is inconsistent with these requirements... 

The X-wind model has also been advanced as a means for thermal processing of chondrules (Shu et al., 1996). While it has not yet been possible to calculate the detailed thermal history of chondrule... 

Hood L. (1998) Thermal processing of chondrule precursors in planetesimal bow shocks. Meteorit. Planet. Sci. 33, 97-107. 

---