Metal-associated carbon in primitive chondrites: structure, isotopic composition, and origin

Graves Nunataks 95209: A snapshot of metal segregation and core formation

“…Data for EH, EL, and CH are from stepped combustion measurements of bulk samples (Grady et al, 1986;Grady and Pillinger, 1990). Other previous data are ranges of ion probe measurements in individual graphite grains (El Goresy et al, 1995;Mostefaoui et al, 1997Mostefaoui et al, , 2000Zipfel et al, 1997). The graphite extracted from the metal-rich vein (Fig.…”

Micro‐Raman spectroscopic investigations of graphite in the carbonaceous meteorites Allende, Axtell and Murchison

“…This may be due to different types of carbon inclusions in the meteorites. Mostefaoui et al 3 compared the crystallite …”

“…The efficiency of both processes depends on various parameters including temperature, pressure, time and the nature of the precursors. 3 Graphitization is a slow process that usually requires very high temperatures, and one should not expect to find perfectly crystallized graphite after heating to the temperatures characteristic of chondrule formation. 3 It is evident that the L a values from the CV3 meteorites Allende and Axtell are very similar, ¾45Å, while the L a value from the CM2 meteorite Murchison is somewhat larger, ¾70Å.…”

“…3 Graphitization is a slow process that usually requires very high temperatures, and one should not expect to find perfectly crystallized graphite after heating to the temperatures characteristic of chondrule formation. 3 It is evident that the L a values from the CV3 meteorites Allende and Axtell are very similar, ¾45Å, while the L a value from the CM2 meteorite Murchison is somewhat larger, ¾70Å. This is in good agreement with the results published by Li et al,7 who stated that the order parameter of carbonaceous material in carbonaceous chondrites generally tends to decrease with increasing petrologic type and metamorphism grade.…”

“…everything that is not an optically definable chondrule or a calcium-aluminum inclusion) or concentrated in carbon-rich aggregates; in both cases, carbon is likely to be poorly graphitized. 3 The first microanalysis by Raman spectroscopy that showed the presence of carbon as graphite in meteorites was performed by Michel-Levy and Lautie 4 in 1981. This investigation of the Tieschitz meteorite revealed the characteristics of a graphite structure.…”