1. Effects of Ca-Mg Substitution in C2/c pyroxene structure on natural clinopyroxenes from spinel peridotite nodules (Pico Cabugi, Brazil)
- Author
-
C. Fabro, Francesco Princivalle, G. Demarchi, Gabriella Salviulo, G., Salviulo, Princivalle, Francesco, Demarchi, Gabriella, and C., Fabro
- Subjects
Nodule (geology) ,Microprobe ,C2/c Pyroxene ,C2/c Pyroxenes ,Mineralogy ,Pyroxene ,Crystal structure ,engineering.material ,Geochemistry and Petrology ,CRYSTAL-STRUCTURE REFINEMENT ,General Materials Science ,Ca-Mg substitution ,Mg-Ca substitution ,spinel peridotites ,Brazil ,Peridotite ,clinopyroxenes ,Materials processing ,Chemistry ,Spinel ,spinel peridotite ,Crystallography ,engineering - Abstract
X-ray crystal structure refinements and microprobe analyses of clinopyroxenes from two suites of spinel-peridotite nodules are compared for an understanding of the structural response to a decrease in Ca content. The kinking of the tetrahedral chain (O3-O3-O3 angle) of the C2/c structure associated with decreased Ca content shows behavior similar to that observed for the A-tetrahedral chain of the P21/c structure. Contemporaneously the occupancy of the M2′ split site increases. In addition, as a consequence of the low Ca content, the M2 polyhedron dominates the structural rearrangement of the clinopyroxenes considered here.
- Published
- 1992