Osmium isotope evidence for uniform distribution of s- and r-process components in the early solar system

Yokoyama, T.; Vinai, K.; Alexander, Conel M. O'd.; Lewis, R. S.; Carlson, Richard W.; Shirey, Steven B.; Thiemens, M. H.; Walker, Richard J.

doi:10.1016/j.epsl.2007.05.017

Cited by 71 publications

(89 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For some elements, in particular barium, neodymium, and samarium, the extent of the effects is still the subject of some debate. For molybdenum, ruthenium, and osmium the effects have not been confirmed by subsequent studies (e.g., Becker & Walker 2003;Lee & Halliday 2002;Yokoyama et al 2007). For these reasons, except for the effects in oxygen and possibly titanium and chromium, evidence that the initial heterogeneity was not entirely erased by mixing within the nebula before planets started to form remains controversial.…”

Section: Introductionmentioning

confidence: 78%

Calcium Isotope Composition of Meteorites, Earth, and Mars

Simon

DePaolo

Moynier

2009

ApJ

148

163

View full text Add to dashboard Cite

The relative abundances of calcium isotopes in the mass range 40-44 were measured in primitive and differentiated meteorites and igneous rocks from Earth and Mars in search of non-mass-dependent variations that could provide clues about early solar system processes. 40 Ca abundance found in some chondrites and all differentiated meteorites studied. It appears that isotopic heterogeneity in calcium was still present at the completion of disk formation but was homogenized during planetary accretion.

show abstract

Section: Introductionmentioning

confidence: 78%

Calcium Isotope Composition of Meteorites, Earth, and Mars

Simon

DePaolo

Moynier

2009

ApJ

148

163

View full text Add to dashboard Cite

show abstract

“…Prior studies have shown that acid digestion of primitive meteorites does not always lead to complete dissolution of all presolar grains, ultimately affecting measured isotopic compositions (23,24). For instance, because presolar SiC grains are strongly enriched in s-process nuclides (25) and are extremely acid-resistant, a measured s-process deficit could reflect the incomplete acid dissolution of s-process-enriched SiC grains (23 (20).…”

Section: Discussionmentioning

confidence: 99%

Tungsten isotopic constraints on the age and origin of chondrules

Budde

Kleine

Kruijer

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

112

View full text Add to dashboard Cite

Chondrules may have played a critical role in the earliest stages of planet formation by mediating the accumulation of dust into planetesimals. However, the origin of chondrules and their significance for planetesimal accretion remain enigmatic. Here, we show that chondrules and matrix in the carbonaceous chondrite Allende have complementary 183 W anomalies resulting from the uneven distribution of presolar, stellar-derived dust. These data refute an origin of chondrules in protoplanetary collisions and, instead, indicate that chondrules and matrix formed together from a common reservoir of solar nebula dust. Because bulk Allende exhibits no 183 W anomaly, chondrules and matrix must have accreted rapidly to their parent body, implying that the majority of chondrules from a given chondrite group formed in a narrow time interval. Based on Hf-W chronometry on Allende chondrules and matrix, this event occurred ∼2 million years after formation of the first solids, about coeval to chondrule formation in ordinary chondrites.Hf-W chronometry | nucleosynthetic anomalies | chondrule formation | complementarity | planetesimal accretion P lanet formation is thought to have occurred in stages and involved the collisional growth of kilometer-sized planetesimals to bodies of ever increasing size. However, the first step of planet formation-the initial accumulation of dust into planetesimals-is poorly understood (1, 2). This process can be investigated by studying chondrites, primitive meteorites derived from small bodies that never melted and differentiated. As such, chondrites preserve a record of the physical and chemical processes that affected solid material in the early solar nebula, ultimately leading to the accretion of dust to planetesimals (3). The two major constituents of chondrites are chondrules-microto millimeter-sized once-molten silicate spherules-and volatilerich, fine-grained matrix. Understanding the formation of these two components is key for constraining the origin of chondrites, which in turn may help to identify the processes that led to the accumulation of solar nebula dust into planetesimals. However, the origin of chondrules remains poorly understood, and a wide range of possible formation mechanisms has been proposed: (i) chondrules may have formed through collisions between protoplanetary bodies (4-6); (ii) chondrules may have formed near the Sun and were then transported outward by protostellar jets (7); and (iii) chondrules may have formed through more localized melting events of nebular dust caused by shock waves (8, 9) or current sheets (10). Although many recent models argue for an impact origin of chondrules (4-6), the observation that chondrules and matrix from carbonaceous chondrites are chemically complementary lends strong support to an origin of both components from a single reservoir of nebular dust (11-13). However, the significance of this chemical chondrule-matrix complementarity and whether it can distinguish between a nebular or impact origin of chondrules is debated (6). Thus, not...

show abstract

“…(a ) Nucleogenic heterogeneity in the solar nebula Isotopic variation at the whole-rock scale has now been identified in a number of elements in primitive meteorites (Black & Pepin 1969;Clayton et al 1973;Rotaru et al 1992;Podosek et al 1997;Dauphas et al 2002;Yin et al 2002b;Becker & Walker 2003;Brandon et al 2005;Andreasen & Sharma 2006Shukolyukov & Lugmair 2006;Carlson et al 2007;Trinquier et al 2007;Yokoyama et al 2007). For the larger of the anomalies, particularly those found in preserved Nd for a variety of meteorites expressed in parts per million difference relative to the average value of a terrestrial Nd standard (in most cases, the La Jolla Nd standard).…”

mentioning

confidence: 99%

Composition of the Earth's interior: the importance of early events

Carlson

Boyet

2008

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

The detection of excess 142 Nd caused by the decay of 103 Ma half-life 146 Sm in all terrestrial rocks compared with chondrites shows that the chondrite analogue compositional model cannot be strictly correct, at least for the accessible portion of the Earth. Both the continental crust (CC) and the mantle source of mid-ocean ridge basalts (MORB) originate from the material characterized by superchondritic 142 Nd/ 144 Nd. Thus, the mass balance of CC plus mantle depleted by crust extraction (the MORB-source mantle) does not sum back to chondritic compositions, but instead to a composition with Sm/Nd ratio sufficiently high to explain the superchondritic 142 Nd/ 144 Nd. This requires that the mass of mantle depleted by CC extraction expand to 75–100 per cent of the mantle depending on the composition assumed for average CC. If the bulk silicate Earth has chondritic relative abundances of the refractory lithophile elements, then there must exist within the Earth's interior an incompatible-element-enriched reservoir that contains roughly 40 per cent of the Earth's 40 Ar and heat-producing radioactive elements. The existence of this enriched reservoir is demonstrated by time-varying 142 Nd/ 144 Nd in Archaean crustal rocks. Calculations of the mass of the enriched reservoir along with seismically determined properties of the D″ layer at the base of the mantle allow the speculation that this enriched reservoir formed by the sinking of dense melts deep in a terrestrial magma ocean. The enriched reservoir may now be confined to the base of the mantle owing to a combination of compositionally induced high density and low viscosity, both of which allow only minimal entrainment into the overlying convecting mantle.

show abstract

Osmium isotope evidence for uniform distribution of s- and r-process components in the early solar system

Cited by 71 publications

References 40 publications

Calcium Isotope Composition of Meteorites, Earth, and Mars

Calcium Isotope Composition of Meteorites, Earth, and Mars

Tungsten isotopic constraints on the age and origin of chondrules

Composition of the Earth's interior: the importance of early events

Contact Info

Product

Resources

About