Clouding of pyroxene and plagioclase in eucrites - Implications for post-crystallization processingThe clouding of pyroxene and plagioclase in the basaltic eucrites ALHA 77302, Juvinas, Pasamonte, and Stannern, is caused by finely disseminated inclusions. This clouding is interpreted to be the result of exsolution of minor components which became incompatible and crystallized on microfractures and other nucleation sites during postbrecciation metamorphism. The phases found in clouding require reduction of silicate FeO to metallic Fe in both pyroxene and plagioclase and possible redox of Cr(2+) to Cr(3+) in pyroxene. The assemblage of coexisting phases that make up clouding record conditions of T approximately equal to 900 C and f(O2) of 10 to the -16th to 10 to the -18th during slow cooling. Thus, clouding can be a useful indicator of postcrystallization conditions.
Document ID
19820038779
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Harlow, G. E. (American Museum of Natural History New York, NY, United States)
Klimentidis, R. (American Museum of Natural History New York, NY, United States)