Ba isotopic compositions in stardust SiC grains from the Murchison meteorite: Insights into the stellar origins of large SiC grains

BARIUM ISOTOPIC COMPOSITION OF MAINSTREAM SILICON CARBIDES FROM MURCHISON: CONSTRAINTS FORs-PROCESS NUCLEOSYNTHESIS IN ASYMPTOTIC GIANT BRANCH STARS

“…With the exception of very large mainstream grains (7-58 μm, Ávila et al 2013), s-process barium isotopic patterns were found, although there exist systematic differences between single grain data and model predictions (Lugaro et al 2003a). In addition, it was found that mainstream SiC grains with smaller sizes tend to contain higher barium concentrations and a barium isotopic signature more strongly enriched in s-process isotopes (Zinner et al 1991;Marhas et al 2007;Ávila et al 2013), supporting the view that barium was implanted in the grains. However, the implantation model proposed by Verchovsky et al (2004) predicts that the 'G-component' (pure s-process barium isotopes made in the helium intershell), defined by Lewis et al (1990), should be implanted more efficiently into larger SiC grains at high energy compared to the 'N-component' (initial barium isotopes present in the convective envelope, low energy), which is the opposite of the observed trend.…”

“…The measurement of abundance anomalies in their isotopic compositions allows the study of s-process nucleosynthesis in individual stars at a level of precision unavailable to spectroscopic observations. Barium isotopic compositions in presolar grains have been measured in SiC aggregates (Ott & Begemann 1990;Zinner et al 1991;Prombo et al 1993;Jennings et al 2002) and in single mainstream grains (Jennings et al 2002;Savina et al 2003a;Barzyk et al 2007a;Marhas et al 2007;Ávila et al 2013). With the exception of very large mainstream grains (7-58 μm, Ávila et al 2013), s-process barium isotopic patterns were found, although there exist systematic differences between single grain data and model predictions (Lugaro et al 2003a).…”

Presolar Grains

“…There is a hint of the initial presence of short-lived 107 Pd (T 1/2 ¼ 6.5 Â 10 6 years) from 107 Ag excesses . Single grain measurements of chromium (Levine et al, 2009;Savina et al, 2010), strontium (Nicolussi et al, 1998b), zirconium (Barzyk et al, 2007;Nicolussi et al, 1997), molybdenum (Barzyk et al, 2007;Nicolussi et al, 1998a), ruthenium , and barium (Barzyk et al, 2007;Savina et al, 2003a) have been made with RIMS and of barium (Avila et al, in press;Marhas et al, 2007), tungsten and hafnium (Avila et al, 2012b), and lead (Avila et al, 2012a) with SIMS. By selecting grains free of contamination by multielement RIMS analysis, Barzyk et al (2007) could, from measured molybdenum (and barium) isotopic ratios, restrict the range of the socalled 13 C pocket to close to the standard case that best explains the main component of s-element in the solar system.…”

Barium Isotopic Compositions in Thirty‐Four Geological Reference Materials Analysed by MC‐ICP‐MS

“…Previous studies have shown that Ba isotopes have the potential to track both high-and low-temperature geochemical processes. Barium isotopic anomalies in meteorites (e.g., carbonaceous chondrites) have been used to constrain the heterogeneity of the early solar system (Savina et al 2003, Ranen and Jacobsen 2006, Andreasen and Sharma 2007, Carlson et al 2007, Avila et al 2013, Bermingham et al 2016; Ba isotopic characteristics of terrestrial (Miyazaki et al 2014, Nan et al 2015 and extraterrestrial igneous rocks (Moynier et al 2015) have been applied to identify the precursor materials of the Earth. Both 'inorganic' weathering process and biological activity can fractionate Ba isotopes in fluids and secondary minerals in soils (Bullen and Chadwick 2016).…”