Abstract

The Kennack Gneisses are a series of migmatites and microgranites found at the base of the peridotite of the Lizard Ophiolite Complex. The gneisses were derived by metamorphism and anatexis of interbedded sediments and basalts of a lower ophiolite slice during displacement of the complex from the oceanic regime in Devonian times. Anatexis is thought to have taken place at temperatures of 700–800 °C and pressures of several kilobars, suggesting that heat was supplied locally by the thrusting of a hot peridotite sheet. Displacement and assembly of the ophiolite slices therefore probably took place not long after formation. Subsequent emplacement onto the Gramscatho beds was after considerable cooling.

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