In California and New Caledonia, metamorphism of eugeosynclinal rocks has produced blueschist facies in limited areas. The outcrop pattern and structure suggest that the shape of the zone of blueschist metamorphism is elongate parallel to major tectonic trends. Juxtaposition of large ultramafic bodies, subparallel to the blueschist belts, indicates a close tectonic relationship between metamorphism and the tectonic emplacement of the ultramafic masses. Initial emplacement of ultramafics along the depressed axis of the eugeosyncline may have produced deformation related to blueschist metamorphism. Mineral assemblages developed in blueschist facies are characterized by having formed under conditions where pressure is predominant over temperature. That pressure is relatively high requires extremely low thermal gradients combined with a rheology that would allow development of tectonic overpressures. ?? 1967.
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Glaucophane schists from california and new caledonia