Condition for the formation of the compound chondrules in the solar nebula

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The conditions for compound chondrule formation described by J. L. GOODING and K. KEIL (Meteoritics, 16,17,1981) are reexamined using the criterion of gravitational instabilities (M. SEKIYA, Prog. Theor. Phys., 69,1116,1983). If a compound chondrule was formed by collisional sticking of a plastic particle with a solid or another plastic particle, the following conclusions are derived : (1) Chondrules were formed after the settling of dust particles had progressed and the number density of dust particles had increased by several orders of magnitude. (2) To reproduce the observed ratio of the compound chondrules to all the chondrules, collisional velocities of pre-chondrule particles must have been larger than about 1.6m s^<-1>, and the Weber number for the collision of molten pre-chondrule particles must have been larger than about 40,if we assume that the chondrule formation occurred in the asteroid region in the stage where dust particles were floating in the solar nebula. In this case, collisional sticking would be difficult. If sticking is impossible, then other formation mechanisms for the compound chondrules must be considered (e. g. J. T. WASSON et al., Geochim. Cosmochim. Acta, 59,1847,1995). (3) If chondrules were formed in the inner regions of the solar nebula, the lower limits for the relative velocities of the prechondrule particles would be reduced.
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