Fisher reported in 1971 that Fanale and Nash have discussed in an earlier paper the K-U systematics of lunar, chondritic and terrestrial rocks and showed that chondrites are not members of these trend and terrestrial samples. They discerned distinct trend lines for Apollo 11 and Apollo 12 samples and for terrestrial rocks earth and showed that chondrites are not members of these trends. They pointed out that, if if the Earth and the Moon were formed from the same material, then the lunar rocks, which thus far have been analyzed must be "enriched" in both U and K, and then the Authors' must search for "depleted" lunar material which would enable the trend lines to be extrapolated so that they cross that of the Earth at some material balance point.
Fanale and Nash, in response to Fisher, included all the terrestrial data lying along the K/U = 104 line. This is an oversimplification based on incomplete data. This shows some recent K/U data for ultramafic rocks. These types of rock are not unimportant in a consideration of the total chemical makeup of the Earth; it is generally considered that either the peridotite inclusions in basalt or kimberlite or the lherzolite nodules discussed herein here are the best approximations to mantle rocks that is know at the present time. These authors concluded that the recent discovery of a glass rich in potassium, rare-earth elements, and phosphorus ("KREEP"), simultaneously reported by several groups of workers at the Apollo 12 conference in Houston in January 1971, together with subsequent studies of rock samples, suggests an additional interpretation of one aspect of the data. It now appears that the Apollo 1 1 and 12 samples may represent U- and K-enriched members of essentially the same differentiation sequence, and that magmatic processes that produced siliceous material such as rock 12013 may also contain an enrichment of such material in U relative to K.
This process may be analogous to the apparent enrichment in U over K in granitic, relative to basaltic, rocks on earth. Such an interpretation would also be consistent with the authors' conclusion that "the two suites appear to have been derived from materials of identical potassium and uranium content" (p. 282). In any case, this would not affect the authors' conclusions concerning the relationship between the bulk K/U ratios of terrestrial, lunar, and chondritic material.
Subsequent to the publication of the authors' report, it was brought to the authors' attention that Tera, et al. have discussed the K-U systematics of the Apollo 11 samples and have pointed out that both U and K are probably highly concentrated in interstitial glassy material.
Also see a review white paper by Campbell (1974): http://i2mconsultants.com/downloads/corp/CampbellK-USystem-1974C.pdf
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