A statistical-chemical and thermodynamic approach to the study of lunar mineralogy |
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| Authors: | SK Saxena LS Walter |
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| Institution: | Department of Geological Sciences, Virginia Polytechnic Institute, Blacksburg, Virginia, U.S.A.;Planetology Branch, Goddard Space Flight Center, Greenbelt, Maryland 20771, U.S.A. |
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| Abstract: | Principal components analysis is used to study the chemical compositions of pyroxenes of five Apollo 12 specimens. Important correlations recognized in the variation of oxide weight per cent are: MGO, Al2O3, SiO2| CaO, TiO2, FeO MgO, Al2O3, SiO2| FeO MgO, SiO2, FeO | Al2O3, CaO, TiO2 where the oxides on one side of the bar are correlated positively with each other and negatively with the oxides on the other side. Several other similarly distinct relationships with significantly less variance could be noted. These correlations indicating substitutional relationships can be interpreted as representative of stable and metastable trends of crystallization by using crystal-chemical and thermodynamic information. The per cent variance of pyroxene groups with characteristic trends in each specimen can be evaluated and interpreted in terms of history of crystallization. Distribution of Fe and Mg in certain pairs of olivine and pyroxene, which are found in contact in the rock and which may have crystallized simultaneously, is useful in recognizing the tendency towards chemical equilibrium in FeMg distribution during a limited interval in the liquidus or subsolidus stages. |
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