Isotopic analysis of presolar graphite grains from Orgueil

Jadhav, M.; Amari, S.; Zinner, E.; Maruoka, Teruyuki

doi:10.1016/j.newar.2006.06.004

Cited by 26 publications

(37 citation statements)

References 11 publications

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“…Although any causal relationships are difficult to discern, the presence of oxygen can stabilize these grains against further graphitization and probably reflects a higher O/C ratios in their formation environments. Further interesting insights into trends in the morphology and other properties of graphites from different density fractions will likely come from planned studies of Orgueil graphites which, unlike those from Murchison, are reported to contain much larger graphites in the high density fractions and also appear to lack cauliflower grains (Jadhav et al 2006).…”

Section: Discussionmentioning

confidence: 99%

Correlated isotopic and microstructural studies of turbostratic presolar graphites from the Murchison meteorite

Croat¹,

Stadermann²,

Bernatowicz³

2008

Meteorit & Planetary Scien

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Abstract-We present data from TEM and NanoSIMS investigations of Murchison (CM2) KFC1 presolar graphites. TEM examinations of graphite ultramicrotome sections reveal varying degrees of graphite disorder, leading to distinctions between well-graphitized onions, more turbostratic platy graphites, and the most disordered cauliflower graphites. Aside from their larger size, platy graphites are roughly similar in isotopic composition and in internal grain properties to the well-graphitized onions. Most carbide-containing platy graphites exhibit large s-process element enrichments (~200× solar Mo/Ti ratios), suggesting origins predominantly in AGB carbon stars. The C isotopic distribution of platy graphites is similar to onions, with representatives in both 12 C-depleted (5 < 12 C/ 13 C < 40) and 12 C-enriched groups (100 < 12 C/ 13 C < 350) and a pronounced gap in the 40 < 12 C/ 13 C < 75 region that contains 75% of mainstream SiCs. The large 12 C enrichments combined with the extreme s-process element enrichments suggest formation in an environment inhomogeneously enriched in the nucleosynthetic products of thermal pulses in AGB stars. In contrast, numerous scaly cauliflower graphites show 18 O enrichments and lack s-process-enriched carbides, suggesting a SN origin, as was the case for many Murchison KE3 SN graphites. The more turbostratic graphites (platy and scaly) are on average larger than onions, likely resulting from formation in a gas with higher C number density. Oxygen content increases progressively with increasing degree of graphite disorder, which can stabilize these grains against further graphitization and may be a reflection of higher O/C ratios in their formation environments.

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Section: Discussionmentioning

confidence: 99%

Correlated isotopic and microstructural studies of turbostratic presolar graphites from the Murchison meteorite

Croat¹,

Stadermann²,

Bernatowicz³

2008

Meteorit & Planetary Scien

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“…Isochrons reported in this paper were derived from more than 450 depth profiles of samples whose data were published in previous studies, including presolar graphite grains from the Orgueil (CI1; Jadhav et al 2006;Groopman et al 2012;Jadhav et al 2013; (Nittler et al 2008) grains, whose major elements include Al, were also analyzed in this study (see Section 3.3).…”

Section: Samples and Experimental Methodsmentioning

confidence: 99%

“…Figure 3 shows the breakdown of these 90 presolar grains by type, including 39 low-density (LD; 1.6 2.05 r < < g cm 3 -) graphite grains; Jadhav et al 2006Jadhav et al , 2013Zinner et al 2014). AB grains, with C C 12 13 ratios <10 are thought to form in J-stars or in born-again AGB stars (Amari et al 2001a;Fujiya et al 2013).…”

Section: Mg-al Isochronsmentioning

confidence: 99%

INFERRED INITIAL²⁶Al/²⁷Al RATIOS IN PRESOLAR STARDUST GRAINS FROM SUPERNOVAE ARE HIGHER THAN PREVIOUSLY ESTIMATED

Groopman

Zinner

Amari

et al. 2015

ApJ

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We performed an in-depth exploration of the Al-Mg system for presolar graphite, SiC, and Si 3 N 4 grains found to contain large excesses of 26 ratios that, on average, are ∼1.5-2 times larger than the ratios previously reported for the grains. The majority of presolar graphite and SiC grains are heavily affected by Al contamination, resulting in large negative Mg Mg 26 24 d intercepts of the isochron lines. Al contamination is potentially due to etching of the grains' surfaces and subsequent capture of dissolved Al during the acid dissolution of their meteorite host rocks. From the isochron fits, the magnitude of Al contamination was quantified for each grain. The amount of Al contamination on each grain was found to be random and independent of grain size, following a uniform distribution with an upper bound at 59% contamination. The Al contamination causes conventional whole-grain estimates to underpredict the initial Al Al ratios greatly exceed those predicted in the He/C and He/N zones of SN models.

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“…The Murchison and Orgueil (CI) meteorites are the only two from which graphite grains were extracted [17,18] and systematically studied [19,20]. The abundance of graphite grains in Murchison is 0.88 ppm [19].…”

Section: Introductionmentioning

confidence: 99%

“…Low-density graphite grains show 18 O enrichment in many of the grains that are taken as proof that they formed in core-collapse supernovae: 18 O is produced via 14 N(α,γ) 18 F(e + ν) 18 O in the partial He burning zone, resulting 18 O/ 16 O ratio of 1.68 in a 15M sun model by Rauscher et al [40]. Many low-density graphite grains show 28 Si excesses, similar to SiC X grains from supernovae, while a few show 29 Si and 30 Si excesses.…”

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confidence: 99%

Nucleosynthetic Signatures in Presolar SiC and Graphite Grains

Amari¹

2017

Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

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Presolar SiC and graphite grains are the grain types whose isotopic signatures have been extensively studied. Isotopic compositions of light and intermediate elements in single grains have been analyzed mostly using secondary ion mass spectrometry. Detailed information about nucleosynthetic conditions can be obtained from isotopic compositions of heavy elements. Isotopic compositions of heavy elements in SiC and graphite grains have been analyzed using resonant ionization mass spectrometry. Analyses of heavy elements and noble gases are likely to produce new insights into presolar grains using newly-developed instruments.

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Isotopic analysis of presolar graphite grains from Orgueil

Cited by 26 publications

References 11 publications

Correlated isotopic and microstructural studies of turbostratic presolar graphites from the Murchison meteorite

Correlated isotopic and microstructural studies of turbostratic presolar graphites from the Murchison meteorite

INFERRED INITIAL²⁶Al/²⁷Al RATIOS IN PRESOLAR STARDUST GRAINS FROM SUPERNOVAE ARE HIGHER THAN PREVIOUSLY ESTIMATED

Nucleosynthetic Signatures in Presolar SiC and Graphite Grains

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Isotopic analysis of presolar graphite grains from Orgueil

Cited by 26 publications

References 11 publications

Correlated isotopic and microstructural studies of turbostratic presolar graphites from the Murchison meteorite

Correlated isotopic and microstructural studies of turbostratic presolar graphites from the Murchison meteorite

INFERRED INITIAL26Al/27Al RATIOS IN PRESOLAR STARDUST GRAINS FROM SUPERNOVAE ARE HIGHER THAN PREVIOUSLY ESTIMATED

Nucleosynthetic Signatures in Presolar SiC and Graphite Grains

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INFERRED INITIAL²⁶Al/²⁷Al RATIOS IN PRESOLAR STARDUST GRAINS FROM SUPERNOVAE ARE HIGHER THAN PREVIOUSLY ESTIMATED