<i>In situ</i> visualization of crystallization inside high temperature silicate melts

Srivastava, Atul; Inatomi, Yuko; Tsukamoto, Katsuo; Maki, Takao; Miura, Hitoshi

doi:10.1063/1.3406149

Cited by 12 publications

(9 citation statements)

References 20 publications

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“…This assumption originates from the results of classical furnace-based crystallization experiments (e.g., ; however, several estimations based on some chondrule features, such as overgrowth thicknesses on relict grains (e.g., Wasson & Rubin 2003) and rim formation for barred olivine chondrules (Miura et al 2010b), give much higher cooling rates (∼ 200-2000 K s −1 ; Miura & Yamamoto 2014). Moreover, porphyritic textures may be reproduced by multiple melting processes (e.g., Rubin 2010) and they can also be formed via supercooled precursors (e.g., Srivastava et al 2010;Seto et al 2017). Therefore, dust enrichment is not necessarily needed for volatile retainment when the heating/cooling rates around their liquidus temperature are high enough.…”

Section: Volatile Retentionmentioning

confidence: 99%

Compound Chondrule Formation in Optically Thin Shock Waves

Arakawa

Nakamoto

2019

ApJ

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Shock-wave heating within the solar nebula is one of the leading candidates for the source of chondruleforming events. Here, we examine the possibility of compound chondrule formation via optically thin shock waves. Several features of compound chondrules indicate that compound chondrules are formed via the collisions of supercooled precursors. We evaluate whether compound chondrules can be formed via the collision of supercooled chondrule precursors in the framework of the shock-wave heating model by using semi-analytical methods and discuss whether most of the crystallized chondrules can avoid destruction upon collision in the post-shock region. We find that chondrule precursors immediately turn into supercooled droplets when the shock waves are optically thin and they can maintain supercooling until the condensation of evaporated fine dust grains. Owing to the large viscosity of supercooled melts, supercooled chondrule precursors can survive high-speed collisions on the order of 1 km s −1 when the temperature is below ∼ 1400 K. From the perspective of the survivability of crystallized chondrules, shock waves with a spatial scale of ∼ 10 4 km may be potent candidates for the chondrule formation mechanism. Based on our results from one-dimensional calculations, a fraction of compound chondrules can be reproduced when the chondrule-to-gas mass ratio in the pre-shock region is ∼ 2 × 10 −3 , which is approximately half of the solar metallicity.

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Section: Volatile Retentionmentioning

confidence: 99%

Compound Chondrule Formation in Optically Thin Shock Waves

Arakawa

Nakamoto

2019

ApJ

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“…We carry out numerical simulations for a wide range of supercooling and cooling rate by using the phase-field method, which is one of the most effective numerical methods to simulate crystal growth in a supercooled liquid. As a first step, we consider the situation of container-less crystallization experiments using levitation methods (Tsukamoto et al, 1999(Tsukamoto et al, , 2001Nagashima et al, 2006Nagashima et al, , 2008Srivastava et al, 2010) because in these experiments the thermal profile of the droplet and the crystal growth pattern were observed in-situ, so we can verify the results of our numerical simulations. For comparison, we consider a droplet of pure forsteritic (Mg 2 SiO 4 ) composition, which was adopted in these experiments.…”

Section: Introductionmentioning

confidence: 87%

A new constraint for chondrule formation: condition for the rim formation of barred-olivine textures

et al. 2011

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A barred-olivine (BO) chondrule usually has an olivine rim that covers the chondrule surface. Numerous experiments have been carried out to reproduce the BO texture. However, the rim structure could be reproduced only in a few studies reported in the literature. The difficulty in reproducing the rim structure lies in the fact that its formation condition has not been constrained experimentally or theoretically. In the present paper, we have carried out numerical simulations of crystal growth of a highly-supercooled melt droplet of pure forsteritic composition (Mg 2 SiO 4), and succeeded in reproducing the double structure, i.e. the rim and the dendrite. The droplet cools from the surface, the temperature of which should be cooler than the center of the droplet. Since a crystal grows faster along the cooler surface than across the hotter center, the rim was found to be formed when the temperature difference between the center of the droplet and its surface is large enough. From our results, both from numerical simulations and analytical consideration, we found that the double structure of rim and the dendrite could be formed only when the cooling rate is within a narrow range, which depends upon the degree of supercooling. Our results, for the first time, could explain why the formation of rim of BO texture was hardly reproduced in the previous experiments reported in the literature to date.

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“…If T n / T hyp is smaller than 1, a remelting occurs. Accoring to the free-floating-crystallization experiment of a forsterite liquid by Srivastava et al (2010), a porphyritic texture was obtained with the value ∼0.7. Thus, a porphyritic chondrule could remelt momentarily by recalescence.…”

Section: Relict Grains In Porphyritic Chondrulesmentioning

confidence: 93%

“…Free-floating, laser-heating experiments using drop towers, high-speed gas flows or ultrasonic sound waves that levitate molten silicate charges remove the problem of preexisting solid nuclei (Nelson et al 1972;Blander et al 1976;Nagashima et al 2008;Srivastava et al 2010). These experiments have clearly shown that the supercooling degree of a melt charge is a crucial factor that determines petrographic textures upon its solidification.…”

Section: Petrographic Textures Of Chondrulesmentioning

confidence: 99%

Bubbles to Chondrites-I. Evaporation and condensation experiments, and formation of chondrules

Nakano

Hashimoto²

2020

Prog Earth Planet Sci

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We propose a simple model of chondrule formation that is supported by our new experiments. With a laser-heating and inert-gas-cooling technique, we obtained evaporation and condensation pathways starting with chondritic compositions till ends, and extracted ‘relative volatilities’ of elements from them. Above boiling points, we observed numerous silicate droplets being ejected from collapsed cavities of vapor bubbles on the surface of molten sample, known as jet-droplets. We postulate jet-droplets as origin of chondrules. The formation mechanism of jet-droplets requires a dense and large solid body (>3 cm across), named ‘duston’, for chondrule precursors. Our chondrule formation model presumes dustons having CI-like composition. Upon boiling, a duston ejects jet-droplets from its molten surface and simultaneously forms an adiabatically expanding vapor cloud around it. The jet-droplets supercool and incorporate the supersaturated vapor and fine condensates while they travel through the cloud, thus completing their makeup as chondrules. The compositions and the mixing ratio of the three components (jet-droplet, vapor and condensate) can be exactly predicted by using relative volatilities of elements, given the chondrule composition to be fitted and the conditions: vaporization degree (VD) and redox state (fs) of the duston. We attempt to reproduce bulk compositions of chondrules in total of 600. About 75% chondrules are successfully matched with specific combinations of VD and fs for each chondrule. The model altogether explains 3.5 features of chondrules: maximum size and size-frequency distribution; chemical variety; and textural variety.

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In situ visualization of crystallization inside high temperature silicate melts

Cited by 12 publications

References 20 publications

Compound Chondrule Formation in Optically Thin Shock Waves

Compound Chondrule Formation in Optically Thin Shock Waves

A new constraint for chondrule formation: condition for the rim formation of barred-olivine textures

Bubbles to Chondrites-I. Evaporation and condensation experiments, and formation of chondrules

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