J/ApJS/253/41 Nitrogen isotopic compositions in Isheyevo (Sanghani+, 2021)
Presolar silicate and oxide grains found in lithic clasts from Isheyevo and
the fine-grained matrix of Northwest Africa 801.
Sanghani M.N., Marhas K.K., Hsiao S.S.-Y., Peeters Z., Shang H., Lee D.-C.,
Bizzarro M.
<Astrophys. J. Suppl. Ser., 253, 41-41 (2021)>
=2021ApJS..253...41S 2021ApJS..253...41S (SIMBAD/NED BibCode)
ADC_Keywords: Meteorites
Keywords: Meteorites; Carbonaceous chondrites; Circumstellar dust
Asymptotic giant branch stars; Type II supernovae; Silicate grains
Novae
Abstract:
We report on the discovery of 33 oxygen-anomalous grains from the
CH3/CBb3 chondrite Isheyevo and the CR2 chondrite Northwest Africa
(NWA) 801. Oxygen isotopic compositions indicate the origin of the
majority grains in stellar outflows of low-mass (∼1.2 to ∼2.2M☉),
solar-metallicity red giant or asymptotic giant branch stars, while
highly 17O-enriched grains probably have nova origins. Isotopic
compositions of the eight 18O-rich grains, including an extremely
18O-rich grain (∼16 times solar 18O/16O ratio), are reproduced
by zone mixing of SNe II ejecta. Close-to-normal silicon, magnesium,
and calcium isotopic compositions of grains are consistent with the
isotope exchange in the interstellar medium or the meteorite parent
body, while two grains with Si isotopic anomalies and one grain with
Mg isotopic anomalies reflect the Galactic chemical evolution. An
Isheyevo clast showed several hot spots with moderate to high 15N
enrichments, including a hot spot with an extreme 15N excess of
(7225±316)%0. However, no correlation between 15N enrichment and
presolar oxygen-rich grain abundance is found. Grains with elliptical
shapes probably indicate primary condensation feature. Two complex
grains possibly display decoupling of the isotopic and elemental
compositions in the grain formation environments. The low
silicate-to-oxide abundance ratio for the fine-grained chondrule rims
in NWA 801 likely reflects the preferential destruction of silicates
due to terrestrial weathering. In NWA 801, the presolar O-rich grain
abundance in fine-grained chondrule rims is higher than in the
interchondrule matrix, similar to the trend observed for some
aqueously altered chondrites of petrologic type 2.
Description:
Polished thin sections of the Isheyevo carbonaceous chondrite were
used for presolar oxygen-anomalous grain search. Several lithic clasts
were identified using the secondary and backscattered electron images
from the scanning electron microscope (SEM) at the Institute of
Geological Survey of Denmark and Greenland (GEUS), Copenhagen. Six
A-clasts with anhydrous silicates were further chosen by looking
carefully at the elemental maps and backscattered electron (BSE)
images and secondary electron (SE) images made using SEM at GEUS,
Copenhagen, and at an electron probe micro analyzer (EPMA), at the
University of Hawaii (UH).
Two thin sections of NWA 801 from our collection were additionally
prepared and backscattered electron images from a field-emission SEM
(FE-SEM) at the Institute of Earth Sciences, Academia Sinica, Taipei,
and an FEI Quanta ESEM-FEG at DTU Copenhagen were used.
See Section 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 32 456 Nitrogen isotopic compositions of the clast B1d_005
from Isheyevo
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See also:
J/A+A/357/572 : Dust formation in WC stars (Cherchneff+, 2000)
J/ApJ/743/L23 : 48Ca heterogeneity in differentiated meteorites (Chen+, 2011)
J/ApJ/758/45 : Isotopic Sr abundances in meteorites (Moynier+, 2012)
J/ApJ/758/59 : Nickel isotopes in meteorites (Steele+, 2012)
J/ApJ/763/L33 : Be-B concentrations in rare CB/CH chondrite (Gounelle+, 2013)
J/A+A/617/A7 : Nitrogen isotopic ratio in prestellar cores (Redaelli+, 2018)
J/A+A/644/A29 : 14N/15N ratio in YSOs (Redaelli+, 2020)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name Nitrogen Hot-spot name
20- 23 F4.2 um Size [0.36/3.25] Hot-spot size
estimate from NanoSIMS ROI
25- 28 I4 10-3 Ratio [-648/9722] Nitrogen isotopic ratio,
δ15N/14N (per mil)
30- 32 I3 10-3 e_Ratio [9/707] Uncertainty (1σ) in Ratio (per mil)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 25-Jun-2021