Chromian Jadeite, Phengite, Pumpellyite, and Lawsonite in a High-Pressure Metamorphosed Gabbro from the French Alps

C. Mevel and J. R. Kienast
Laboratoire de Pétrologie, Université de Paris VI, 4 pl Jussieu, 75230 Paris cedex 05, France

Summary: Small ophiolitic bodies are enclosed in the calcschists of the Piemont zone (western Alps). They have been metamorphosed in the blueschist facies during the alpine orogeny. One of them, the Roche Noire massif, includes gabbro breccias. The magmatic mineralogy of the gabbro was plagioclase + clinopyroxene + minor chromite. There was no chemical homogenization during metamorphism because of the lack of penetrative deformation and on the site of previous chromites, chromium-rich high-pressure and low-temperature minerals (jadeite, phengite, pumpellyite, and lawsonite) were formed. The Al ⇌ Cr substitution does not affect other P- and T-dependent substitutions.

Mineralogical Magazine; December 1980 v. 43; no. 332; p. 979-984; DOI: 10.1180/minmag.1980.043.332.04
© 1980, The Mineralogical Society
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