Retrograde eclogite from Mont Albert, Gaspé, Quebec: Discussion
Trzcienski describes a garnetand clinopyroxene-rich rock from the metamomhic sole of the Mont Albert ultrabasicbasic complex and interprets the rock as a retrogressed eclogite. Using the mineralogical data of Trzcienski's Table 1, this discussion presents evidence showing that the rock is not an eclogite, even though it is a gamet clinopyroxenite. Noneclogite gamet clinopyroxenites are common in metamorphic sequences developed at the base of transported alpine-type peridotites and within certain alpine-type peridotites, numerous examples of which have been documented in the literature (e.g., Spray 1982). The clinopyroxenes of these rocks may have relatively high Ca-Tschermak contents but are low in the additional jadeite and acmite components necessary to define the clinopyroxenes as omphacitic. The distinction of garnet clinopyre Green and Ringwood 1966; Clark and Papike 1968). These compositions are best represented by the system jadeiteacmite diopside hedenbergite Ca-Tsch (Clark and Papike 1968). This classifies the vast majority of the clinopyroxenes of eclogites as omphacites (Deer et al. 1978). Essene and Fyfe