Statistical analysis of clinopyroxenes from deep-sea basalts Available to Purchase

Pyroxene analyses of superior quality, from Dsdp Legs 11, 15, 17, 34, and 37, have been used to identify the various basalt groups from pyroxene chemistry. Cluster analysis, factor analysis, and variation plots give insight into the crystal chemistry of the pyroxenes. The tholeiitic and alkalic pyroxene groups differ primarily in Cr₂O₃, TiO₂, and Na₂O contents. Tholeiitic pyroxenes are high in Cr₂O₃ and low in Na₂O and TiO₂, relative to an average pyroxene. For the same oxides, pyroxenes from alkalic basalts are high in TiO₂ and Na₂O, and low in Cr₂O₃. Two pairs of cations, Ti–^IVAl and Fe³⁺–^IVAl, have high correlation coefficients in all of the groups. It appears that common substitutions which occur in deep-sea pyroxenes are: Al for Si in a tetrahedral site combined with Ti or Fe³⁺ substituting for Mg or Fe²⁺ (respectively) in the octahedral M1 site.