Crystallization of calcium‐aluminum‐rich inclusions: Experimental studies on the effects of repeated heating events

Abstract

Abstract-The observed textures and chemistry of calcium-aluminum-rich inclusions (CAIs) are presumed to be the culmination of a series of repeated heating and cooling events in the early history of the solar nebula. We have examined the effects of these heatingkooling cycles experimentally on a bulk composition representing an average Type B CAI composition by varying the nature of the starting material. Although the most recent and/or highest temperature event prior to incorporation into the parent body dominates the texture and chemistry of the CAI, prior events affect the phase compositions and texture. We have determined that a prior low-temperature event (simulated by heating the sample to 1275 "C and cooling slowly) increases the likelihood of anorthite crystallization in subsequent higher temperature events. A prior high-temperature event that produced dendritic melilite (simulated by heating the sample to 1550 "C and cooling rapidly) results in melilite that shows evidence of rapid crystallization in subsequent lower temperature events. The addition of Pt powder to the starting material appears to enhance the ability of anorthite to nucleate from this composition and increases the number of melilite crystals present in samples that crystallize euhedral melilite.

Zoning patterns of Fe and V in spinel from a type B Ca‐Al‐rich inclusion: Constraints on subsolidus thermal history

“…Type B1 inclusions are an important subclass consisting mostly of spinel, melilite, fassaitic clinopyroxene, and anorthite with a melilite-enriched outer mantle and variable amounts of finegrained alteration products. These inclusions are typically spheroidal in shape (but see Caillet et al 1993) and the coarse-grained phases are generally thought to have crystallized during one or more melting events, interspersed with or followed by alteration of varying intensity at lower temperatures (Beckett et al 2000;MacPherson and Davis 1993;MacPherson and Grossman 1981;Paque et al 2000;Stolper 1982). The melting events have received a great deal of attention because of their potential for constraining physical processes and high-temperature environments in the primitive solar nebula.…”

New minerals in type A inclusions from Allende and clues to processes in the early solar system: Paqueite, Ca3TiSi2(Al,Ti,Si)3O14, and burnettite, CaVAlSiO6

“…1958), who is also a cosmochemist at the California Institute of Technology. Her work has emphasized analytical and experimental approaches to understanding the nature of CAIs in meteorites (e.g., Paque et al., 1994, 2000, 2009, 2013; Stolper & Paque, 1986). Two of her publications are devoted to the phase that is being named paqueite (Barber et al., 1994; Paque et al., 1994).…”