Mapping of carbon concentrations in the Allende meteorite with the ¹²C(d,p)¹³C method

Abstract

We have “mapped” carbon concentrations in a 4.2 × 4.2 mm area of the Ailende meteorite with the 12C(d,p)13 C nuclear method. The x,y resolution perpendicular to the deuteron beam was 65 μm; the depth resolution was 0.6 μm. The matrix of the meteorite contains about 1 wt % carbon, which is uniformly distributed at the 65‐μm level of resolution. The matrix contains most, perhaps close to all, C of this meteorite. The coarse‐grained constituents, such as chondrules, show a very strong enhancement of C in the depth range 2 to about 0 μm; the matrix does not show this enhancement. The enhancement may be due to contamination of the coarse‐grained areas or else to migration of C in solid solution from the interiors of comparatively large crystals to their freshly polished surfaces.

Organic compounds in the Murchison and Allende carbonaceous chondrites studied by photoionization mass spectrometry

“…It has been established previously (Van der Stap et al, 1986) that carbonaceous matter and hence organics are generally confined to the fine-grained matrix of chondrites. It would be desirable to determine the spatial relationships of different organic species, because such information might correlate with the mechanisms responsible for their production (e.g., synthesis on a metal or silicate particle versus fine-grained carbonaceous matter or phyllosilicates) or whether or not the particular organic compound in question was synthesized in the solar nebula or during a parent-body process (Cronin et al, 1988;Hayatsu and Anders, 1981).…”

Carbon, Oxygen, Silicon, Sulphur, Calcium, and Iron Determinations in Twenty‐four Dark Clasts and One Dark Inclusion of the Allende Meteorite by 12C(d,p)13C Nuclear Reaction and PIXE

“…Those from the oxygen reaction occur primarily in the range 0.8-1.70 MeV. Particles from reactions of the deuterons with other elements in the meteorite do not contribute measurably to the counting rates in these ranges (see also Van der Stap et al, 1986).…”

“…In our first series of measurements, we used graphite and kapton-foils (Cz2HIONzOs) as carbon standards (Van der Stap et al, 1986;. These were not fully satisfactory, hence we fabricated a standard from the Allende meteorite itself by grinding a 13 g piece in a ballmill to a fine powder, which was then homogenized and pressed into a 2.5 ern diameter pellet at 30 tons pressure.…”

“…1. In our earlier studies of carbon in Allende ( Van der Stap et al, 1986;, we have discussed how one can deduce carbon in different depth layers below the surface using definite energy windows in the measured Cvproton spectrum. The determination of the C con-…”

Carbon in Dark Inclusions of the Allende Meteorite

“…Here we report on the first two only. We focus on the element carbon because it occurs in Allende predominantly in one form: poorly crystalline graphite (Bauman et al, 1973;Chang et al, 1978;Housley and Clarke, 1980;Smith and Buseck, 1980;Lumpkin, 1983;Heymann et al, 1986). The distribution of carbon within the meteorite, and specifically for this work, in and about Drs may relate to condensation in the solar nebula, synthesis of carbonaceous matter on the parent body, and metamorphism, but above all to accretionary processes.…”