ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract Electron microprobe analyses of Ca-poor pyroxenes in gabbroic rocks of the Main Zone of the Bushveld Complex reveal that inverted pigeonites have lower Mg/Fe ratios than coexisting hypersthenes. Textural relationships, however, indicate that the two Ca-poor pyroxenes did not crystallize simultaneously from the magma. Early pigeonite reacted with the magma to form hypersthene and the difference in the Mg/Fe ratio of these two pyroxenes reflects the difference of this ratio between early pigeonite and the magma at the time of reaction. Some of the grains of early pigeonite, now inverted to hypersthene, evidently escaped this reaction with the magma. Bulk compositions of pyroxenes intermediate between that of pigeonite and hypersthene are postulated on the grounds of varying amounts of exsolved augite in the hypersthene which has originated from pigeonite by reaction with magma.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00373565
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