no. 3624 METEORITES — MASON AND MAYNES 5 



olivine and pyroxene. The normative plagioclase has the composi- 

 tion Ann, a little more calcic than indicated by the refractive index, 

 but, because of the fine-grained nature of the feldspar, the latter 

 measurement is not very precise. 



Owing to its freshness and availability, the Allegan meteorite has 

 been used for many determinations of minor and trace elements. 

 These elements, in parts per million, are as follows (numbers in paren- 

 theses indicate references under "Literature Cited") : 



Schmitt et al (1965) have compared the abundances of Na, Sc, Cr, 

 Mn, Fe, Co, and Cu in chondrules and in the meteorite as a whole, 

 comparing the abundances by the ratio of the concentration in the 

 chondrules to the concentration in the meteorite as a whole. For the 

 elements Na, Sc, and Mn, this ratio is somewhat greater than unity, 

 indicating that these elements are relatively enriched in the chon- 

 drules. For Cr the ratio is 0.7, indicating lower chromium in the 

 chondrules than in the groundmass; for Fe and Cu this ratio is about 

 0.3, and for Co it is very low, 0.05. This correlates well with the geo- 

 chemical behavior of these elements and the distribution of minerals 

 within the meteorite. The chondrules are made up almost entirely 

 of silicates, whereas the metal and sulfide phases are practically con- 

 fined to the groundmass. Thus, the lithophile elements Na, Sc, and 

 Mn are relatively enriched in the chondrules; Cr is present partly in 

 the pyroxene, but also as chromite, and the chromite is mostly in the 

 groundmass; some of the Fe is in the silicates, but most is present 



