The distribution of Cr and the Mg-Cr relationship in terrestrial, meteoritic and lunar basalts

Abstract

The Cr distribution and the Cr-Mg relationship in terrestrial, meteoritic and lunar basalts have been examined. Meteoritic and lunar basalts contain on average, approximately the same amount of Cr which is an order of magnitude greater than that for terrestrial basalts. On the other hand, the statistical nature of the Cr distribution in each of the three sets of basalts differs distinctly. Cr and Mg correlate positively in meteoritic basalts and define a near-perfect straight line trend. Cr and Mg are also positively correlated in lunar basalts but with a much greater spread of values. The Cr-Mg meteorite line approximately bisects the spread of points of lunar basalts. Each Apollo mission site has a characteristic Cr-Mg relationship. An attempt by means of ionization potentials to predict the likelihood of Cr^II on the lunar surface has been inconclusive.