Anders: Origin of Carbonaceous Chondrites 



521 



drites as well (Fredriksson, 1%2). Alteration of the olivine by water would 

 release these spherules, possibly in altered form, from their chondrule matrix. 

 But it is also possible that the spherules formed at a later stage. The particles 

 in Orgueil are quite similar to the troilite globules in meteorite veins (Anders 

 and Goles, 1961) and may well be of similar origin. The association of many 



#- 



• Carbonaceous Chondrite (Murray) 

 o Ordinary Chondrite (Holbroolt) 



»20 



.21 



.22 



.36 



.38 



He He Ne'^"' Ne"' Ne'^'" Ar'^ Ar"" 



FiGURE 5. Noble gases in a cariionaceous and an ordinary chondrite. In Holhrook, these 

 gases (except for radiogenic He-") are produced by cosmic-ray induced spallation reactions on 

 iron and other stable nuclides. The 3 neon isotopes are made in nearly ef|ual aliundance. 

 In Murray, the isotopic abundances resemble those in Earth's atmosphere, suggesting that 

 these gases, too, are of primordial origin. A small amount of cosmogenic gas is present in 

 Murray as indicated l)y the increased abundances of He^ and Ne-^ relative to their atmospheric 

 abundances. 



of the Orgueil spherules with firmly attached silicate fragments is consistent 

 with either hypothesis. 



The trace element abundances, the variations in the olivine composition, and 

 the primordial gas content are most easily e.xplained by assuming that both 

 the carbonaceous chondrites and the ordinary chondrites were derived from 

 still more primitive ancestral matter. Perhaps the most embarrassing require- 

 ment for this material is that some of it at least must have passed through an 

 earlier, high-temperature stage without losing its primordial gases completely. 



It is possible to accomplish this in the meteorite parent body, but some 

 special assumptions are required (DuFresne and Anders, 19626). A more 



