Dynamical lifetimes of objects injected into asteroid belt resonances. Grimm, R. Heliocentric zoning of the asteroid belt by aluminum heating. Weidenschilling, S. The distribution of mass in the planetary system and solar nebula.
Space Sci. Greenberg, R. Planetesimals to planets—Numerical simulation of collisional evolution. Icarus 35 , 1—26 Stevenson, D. Rapid formation of Jupiter by diffuse redistribution of water vapor in the solar nebula.
Icarus 75 , — Scott, E. Bus, S. Phase II of the small main-belt asteroid spectroscopic survey: The observations. Lazzaro, D. Discovery of a basaltic asteroid in the outer main belt. Sunshine, J.
High-calcium pyroxene as an indicator of igneous differentiation in asteroids and meteorites. Cellino, A. The fossilized size distribution of the main asteroid belt. Linking the collisional evolution of the main belt to its dynamical excitation and depletion. Icarus , 63—94 Velocity distributions among colliding asteroids. Cambridge Univ. Press, Cambridge, Eugster, O. Cosmic-ray exposure ages of meteorites and lunar rocks and their significance. Chemie Erde 63 , 3—30 Download references. We thank S.
Bus, J. Chambers, D. Durda, M. Gounelle, H. Haack, H. Levison, T. McCoy, D. Mittlefehldt, E. Scott, J. Sunshine, D. Vokrouhlicky and M. Zolensky for discussions and comments. William F. You can also search for this author in PubMed Google Scholar. Correspondence to William F. Reprints and permissions information is available at npg. Bell J. Davis, W. Hartmann and M. Gaffey Asteroids: The big picture.
In Asteroids II eds. Binzel, T. Gehrels, and M. Matthews , pp. Makes case for radial T gradient in nebula corresponding to asteroid belt. Hewins R. In Ann. Earth Planet. Reviews evidence pertaining to chondrules and what they might tell us about the solar nebula. MacPherson G. Simon, A. Davis, L. Grossman and A. Krot Calcium-aluminum-rich inclusions: major unanswered questions.
In Chondrites and the Protoplanetary Disk eds. Krot, E. Scott, and B. Reipurth , pp. ASP Conference Series, vol. Astronomical Society of the Pacific: San Francisco. Jones R. Lee, H. Connolly Jr.
Love and H. In Protostars and Planets IV eds. Mannings, A. Boss, S. Russell , pp. Davis A. Summarizes the importance of volatility fractionation in the early solar system. Wood J. Primary and secondary minerals occur between matrix olivine grains. Their species and distributions are different in each matrix. In the host matrices of MET and MET chondrites, similar secondary minerals were observed; Ca-pyroxene, Fe, Ni-sulfide, ferrous olivine, fayalite, magnetite and altered silicates occur in these matrices Fig.
These mineral species are similar to those of CV3 OxB matrices e. These mineral species are consistent with those of CV3 OxA matrices e. In the A matrix 5, Ca-pyroxene, Ca-phosphate, relict Fe, Ni-metal, ferrous olivine and magnetite were observed Fig.
Fe-sulfide and Fe, Ni-sulfide are rare. These mineralogical features are similar to those of the CV3 Ox matrix e. In the RBT matrices 5 and 6, similar primary and secondary minerals were observed: kirschsteinite, Ca-pyroxene, Ca-phosphate, Fe, Ni-metal, kamacite, Fe-sulfide, Fe, Ni-sulfide, ferrous olivine and magnetite occur in these matrices Fig.
These mineralogical features are similar to those of the CV3 Red matrix e. We could not find any evidence of terrestrial weathering such as oxidation of opaques in the measured matrices e. The measured matrices have various Sr abundances and show some departures from CI chondrite abundance Fig. Small Ce anomalies are detected in each matrix Fig. The Ce anomalies are not correlated with the matrix compositions with respect to soluble elements such as Ca, Sr and Nd Additional file 1 : Fig.
Most of the matrices show Eu anomalies with large uncertainties; both positive and negative anomalies were detected in each matrix Fig. R 2 : correlation coefficient. In weathered Antarctic meteorites, the precipitation of Fe oxide weathering products is confined to fractures through the meteorite and voids in the fusion crust, rather than being pervasively distributed throughout the matrix Abreu and Brearley The low permeability of the matrix might limit the incorporation of terrestrial water into the matrices and prevent them from experiencing terrestrial weathering.
A similar process might have occurred in the matrices we measured and result in no precipitation of weathering products in them because CV3 matrices would have low permeability Bland et al.
Based on the weathering scale for ordinary chondrites e. The measured matrices with weathering grade W1 show similar or lower Ca, Sr and REE abundances compared to those with weathering grade W0 or matrices in the unweathered fall-type CV3 chondrites Fig. This may suggest that leaching of soluble elements might occur during terrestrial weathering in the matrices with weathering grade W1.
The depleted elements are Ce, Pr, Sm, Tb, Ho and Tm, which do not have high solubility in water, suggesting that soluble element abundances of the matrices with weathering grade W1 would not be disturbed during terrestrial weathering. The leaching of soluble elements from achondrites would cause low soluble element abundances with positive Ce anomalies. We expect that a similar process would occur in the CV3 matrices we measured. This indicates the same conclusion that Ca, Sr and LREEs would not be leached from the matrices with weathering grade W1 during terrestrial weathering.
Therefore, the Ca, Sr and LREE abundances of the matrices we measured would probably reflect preterrestrial processes, i. Although only the CV3 Red RBT matrix 6 shows a negative correlation between Sr abundances and Ce anomalies, it will not be discussed further because of its small number of data.
We will discuss whether any redistribution of Sr and LREEs occurred during aqueous alteration in type 1 and 2 matrices in the following sections.
The Sr and LREE partition coefficients in Ca-pyroxene from melt are highest among those in secondary minerals in a type 1 matrix e. This suggests that the Sr and LREEs in aqueous fluids would be preferentially incorporated into Ca-pyroxene during its formation. Since the amounts of Ca-pyroxene minerals control the Sr and LREE abundances of the matrix, the Sr and LREE abundances of a type 1 matrix would be disturbed during aqueous alteration in the parent body.
The Ca-rich phases in type 2 matrix are kirschsteinite, Ca-pyroxene, Ca-phosphate and plagioclase Fig. Because the Sr partition coefficients in these minerals are high Additional file 1 : Fig. S4 , the Sr in aqueous fluids would be preferentially incorporated into them during their formation. Since the amounts of these secondary minerals control the Sr abundance of the matrix, the Sr abundance of a type 2 matrix would be disturbed during aqueous alteration in the parent body.
There are no secondary minerals that have higher LREE partition coefficients than those of the Ca-rich secondary minerals in a type 2 matrix Additional file 1 : Table S1 and Fig. Thus, case 1 would not be possible. Because the dissolution of Sr and La in aqueous fluids would reflect the aqueous alteration conditions e.
This then implies that their LREE abundances would reflect the nebular process prior to the accretion of their parent body. This may imply that 1 all the matrix minerals experienced similar thermal processes in the solar nebula or 2 although each matrix mineral was formed by different nebular processes, they were well mixed prior to the accretion to their parent body.
This may imply that the matrix minerals retained their heterogeneity when the CV3 Red RBT matrix accreted to its parent body. The specific minerals or nebular processes that control the LREE abundances of matrices could not be constrained in this study.
0コメント