Book contents
- Chondrules
- Cambridge Planetary Science
- Chondrules
- Copyright page
- Contents
- Contributors
- 1 Introduction
- Part I Observations of Chondrules
- 2 Multiple Mechanisms of Transient Heating Events in the Protoplanetary Disk
- 3 Thermal Histories of Chondrules
- 4 Composition of Chondrules and Matrix and Their Complementary Relationship in Chondrites
- 5 The Chondritic Assemblage
- 6 Vapor–Melt Exchange
- 7 Chondrules in Enstatite Chondrites
- 8 Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry
- 9 26Al–26Mg Systematics of Chondrules
- 10 Tungsten Isotopes and the Origin of Chondrules and Chondrites
- 11 The Absolute Pb–Pb Isotope Ages of Chondrules
- 12 Records of Magnetic Fields in the Chondrule Formation Environment
- Part II Possible Chondrule-Forming Mechanisms
- Index
- Plate Section (PDF Only)
- References
6 - Vapor–Melt Exchange
Constraints on Chondrite Formation Conditions and Processes
from Part I - Observations of Chondrules
Published online by Cambridge University Press: 30 June 2018
- Chondrules
- Cambridge Planetary Science
- Chondrules
- Copyright page
- Contents
- Contributors
- 1 Introduction
- Part I Observations of Chondrules
- 2 Multiple Mechanisms of Transient Heating Events in the Protoplanetary Disk
- 3 Thermal Histories of Chondrules
- 4 Composition of Chondrules and Matrix and Their Complementary Relationship in Chondrites
- 5 The Chondritic Assemblage
- 6 Vapor–Melt Exchange
- 7 Chondrules in Enstatite Chondrites
- 8 Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry
- 9 26Al–26Mg Systematics of Chondrules
- 10 Tungsten Isotopes and the Origin of Chondrules and Chondrites
- 11 The Absolute Pb–Pb Isotope Ages of Chondrules
- 12 Records of Magnetic Fields in the Chondrule Formation Environment
- Part II Possible Chondrule-Forming Mechanisms
- Index
- Plate Section (PDF Only)
- References
Summary
The bulk volatile contents of chondritic meteorites provide clues to their origins. Matrix and chondrules carry differing abundances of moderately volatile elements, with chondrules carrying a refractory signature. At the high temperatures of chondrule formation and the low pressures of the solar nebula, many elements, including Na and Fe, should have been volatile. Yet the evidence is that even at peak temperatures, at or near the liquidus, Na and Fe (as FeO and Fe-metal) were present in about their current abundances in molten chondrules. This seems to require very high solid densities during chondrule formation to prevent significant evaporation. Evaporation should also be accompanied by isotopic mass fractionation. Evidence from a wide range of isotopic systems indicates only slight isotopic mass fractionations of moderately volatile elements, further supporting high solid densities. However, olivine-rich, FeO-poor chondrules commonly have pyroxene-dominated outer zones that have been interpreted as the products of late condensation of SiO2 into chondrule melts. Late condensation of more refractory SiO2 is inconsistent with the apparent abundances of more volatile Na, FeO and Fe-metal in many chondrules. Despite significant recent experimental work bearing on this problem, the conditions under which chondrules behaved as open systems remain enigmatic.
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- Information
- ChondrulesRecords of Protoplanetary Disk Processes, pp. 151 - 174Publisher: Cambridge University PressPrint publication year: 2018
References
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