Ordinary chondrite-related giant (>800μm) cosmic spherules from the Transantarctic Mountains, Antarctica

Oxygen isotopes in cosmic spherules and the composition of the near Earth interplanetary dust complex

“…This is not consistent with the bulk major element composition of the spherules, as the glass spherules of this group all belong to the normal group characterized by moderate evaporation (e.g., Yada et al, 2005). The high d 18 O and D 17 O are thus a pristine characteristic and the spherules have been described in the literature as 16 O-poor spherules (Yada et al, 2005;Suavet et al, 2010Suavet et al, , 2011. Their precursor might be fragments of unequilibrated ordinary chondrites (Suavet et al, 2010), dominated by chondrules with glass or feldspathic mesostasis (D 17 O = +3&; Franchi et al, 2001) or by secondary magnetite grains (D 17 O = +5& to +7&; Franchi et al, 2001).…”

“…When analyzed, Na 2 O contents are low (<0.31 wt.% Na 2 O), which suggests that studied particles do not derive from ablation of larger objects during atmospheric entry . Cosmic spherules come from mid-Pacific deep-sea sediments (Clayton et al, 1986;Engrand et al, 2005), Antarctic ice Taylor et al, 2005;Yada et al, 2005), and loose Antarctic sediments (Suavet et al, 2010(Suavet et al, , 2011Cordier et al, 2011aCordier et al, , 2012. Their apparent diameter ranges from 50 to 2280 lm, with a gradual decrease in the spherule number with increasing size and a gap between 1600 and 2200 lm (Fig.…”

“…1. whereas that of primitive asteroids/comets decreases, suggesting a continuum between micrometeorites and meteorites. Accordingly, study of "giant" micrometeorites (Suavet et al, 2011) has shown that the contribution of ordinary chondrite asteroids largely dominates the flux (45%) when the spherule diameter exceeds 1 mm. Our work shows that the transition in terms of relative abundance of the two cosmic spherule populations is sharp and around 500 lm in size.…”

“…2) (Clayton et al, 1986;Engrand et al, 2005;Taylor et al, 2005;Yada et al, 2005;Suavet et al, 2010Suavet et al, , 2011Cordier et al, 2011aCordier et al, , 2012. No compositional data exist for spherules analyzed for oxygen isotopes by Suavet et al (2010).…”

HED-like cosmic spherules from the Transantarctic Mountains, Antarctica: Major and trace element abundances and oxygen isotopic compositions

“…However, different offset amplitudes are observed when analyzing the olivine San Carlo and the quartz "Boulangé" standards (Suavet et al, 2010). The value we used for correcting the offset might be not strictly suitable for the measurement of basaltic glasses, although, in practice, it is a satisfactory approximation for the building of an internally consistent database for differentiated and chondritic spherules from the Transantarctic Mountain micrometeorite collection (this study; Suavet et al, 2010Suavet et al, , 2011bCordier et al, 2011b). This might successfully explain why all the spherules plot below the trend expected for spherules deriving from 4-Vesta or vestoids but in a coherent way.…”