Multiple nitrogen isotopic components coexisting in ureilites

Abstract

Abstract-Nitrogen and noble gas isotopic compositions and C abundance of ureilites were analyzed using a stepwise combustion technique. Four Antarctic ureilites, ALHA77257, Asuka 88 193 I , Yamato 791538 and Yamato 790981 were analyzed. Multiple N isotopic components were observed in these ureilites. The 615N values of these N components ranged from +160 to -120%0. The minimum 615N values of typically -120%0 were observed at combustion temperatures at 70CL900 "C where large amounts of C were released. A heavy N component was observed in only two ureilites, ALHA77257 and Asuka 881931. Silicate-enriched fractions and C-concentrated fractions were prepared for these two ureilites. We concludc that both the light N and the heavy N are trapped in the carbonaceous vein minerals. The lack of correlation between the N/C ratio and the 36Ar/C ratio suggests that the primary carrier phase of the light N does not correspond to that of the planetary noble gases. We consider that the isotopically heavy N, which was observed in this study, is related to the heavy N observed among polymict ureilites. Small amounts (<0.5 ppm) of light N with the minimum 6I5N value of -120%0 were observed among the silicate fractions at the highest combustion temperature of 1200 OC, although the exact carrier phase of this light N is not known. We: consider that the currently observed ureilites were produced by injection of several volatile-rich objects into volatile-poor ureilitic silicates.

Spectral reflectance properties of ureilites

“…The pigeonite is homogeneous and shows coarse twin bands and spinodal decomposition due to incipient exsolution (Tribaudino 2006), while low‐Ca pyroxene exhibits fine lamellae‐like structures parallel to (100) consisting of orthopyroxene and clinopyroxene structures, with no apparent change in Ca content (Takeda 1989). Carbon content is 3.10 wt% (this study), which is identical to the value reported by Yamamoto et al. (1998).…”

“…1983), 3.50 wt% (Grady et al. 1985), 3.34 wt% (Jarosewich 1990), 1.27–3.56 wt% (Yamamoto et al. 1998), 3.0 wt% (Rooke et al.…”

Isotopic fractionation of nitrogen and carbon in Paleoarchean cherts from Pilbara craton, Western Australia: Origin of 15N-depleted nitrogen

“…Only sample preparation is described here. Yamamoto et al (1998) and Pinti et al ( , 2007 Kiyokawa et al, 2006). (b) Geological map of the North Pole Dome and Marble Bar area with location of sampled cherts redrawn and modified from the original map from the Western Australia Geological Survey.…”

Recycled noble gas and nitrogen in the subcontinental lithospheric mantle: Implications from N-He-Ar in fluid inclusions of SE Australian xenoliths.

“…Elemental and isotopic compositions of N and Ar are corrected for instrumental and procedural blanks as well as isotope discrimination factors determined from repeated analyses on the known amounts of air standard. Full descriptions of the analytical method and data processing are given in Yamamoto et al (1998).…”