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SOLID SOLUTION, SUBSOLIDUS REDUCTION AND COMPOSITIONAL CHARACTERISTICS OF SPINELS IN SOME APOLLO 15 BASALTS
Author(s) -
Haggerty Stephen E.
Publication year - 1972
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1972.tb00448.x
Subject(s) - spinel , chromite , basalt , forsterite , solid solution , ionic radius , octahedron , geology , mineralogy , chemistry , geochemistry , crystallography , ion , crystal structure , paleontology , organic chemistry
Compositional data for spinels in the chromite‐hercynite‐ulvöspinel system from three large basalts and for spinels in 48 basalt particles in four soil samples show: (1) that the range of compositions are comparable to those of spinels in Apollo 12 basalts; (2) that the spinel series is complete between 0.75 FeCr 2 O 4 0.25 FeAl 2 O 4 and Fe 2 TiO 4 ; (3) that the Apollo 12 bimodal distribution is present insofar as chromite‐rich and ulvöspinel‐rich phases are more commonly present than compositions intermediate between these two end members; (4) well defined ionic relationships exist for those cations displaying high octahedral site preference energies in the spinel structure (viz. Cr vs Al and Ti vs Cr+ Al); (5) cations displaying low site preference energies (Fe 2+ , Mg) show poor correlation; and (6) the absence of a simple relationship between the divalent ions (Fe 2+ and Mg), and the paucity (10% of 356 analyses) of intermediate compositions suggests a strong dependence on the structural stability of intermediate members of a normal (hercynite, chromite) — inverse (ulvöspinel) solid solution series