Exsolution in clinoamphiboles

M. Ross; J. J. Papike; P.W. Weiblen

doi:10.1126/science.159.3819.1099

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Exsolution in clinoamphiboles

M. Ross·J. J. Papike·P.W. Weiblen

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Abstract

Ten amphibole specimens from a variety of metamorphic rocks such as talc schists, eclogites, and metamorphosed iron formations contain lamellae of a second amphibole oriented parallel to (1̅01) or (100), or both, of the host. Tremolites, actinolites, and hornblendes commonly have lamellae of a calcium-poor clinoamphibole with P 2 1 / m space-group symmetry, or lamellae of cummingtonite with C 2/ m space-group symmetry. Likewise cummingtonites and P 2 1 / m clinoamphiboles commonly contain lamellae of calcium-rich C 2/ m amphiboles such as tremolite. Results of x-ray diffraction, electron-probe, and microscope studies indicate that most lamellae result from unmixing of a homogeneous amphibole. The P 2 1 / m clinoamphibole is analogous to the clinopyroxene pigeonite in agreement with the results of M. G. Bown.

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M. Ross, J. J. Papike, P.W. Weiblen. 1968. Exsolution in clinoamphiboles. https://doi.org/10.1126/science.159.3819.1099

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