Until I moved to Woods Hole Oceanographic Institution in 1988, I had the impression that mid-ocean ridge basalts (MORB) were the best-understood basalts on Earth. Their Sr isotopic compositions were uniform around 87Sr/86Sr = 0.7025, indicating their derivation from a well-stirred mantle source. Their Nd isotopic compositions were radiogenic, indicating that their source(s) had been light REE depleted for a long period of time. Their crystallisation sequence of olivine-plagioclase-clinopyroxene was well recognised (e.g., Bender et al., 1978; Grove and Bryan, 1983) and their major element characteristics indicated fairly low pressure (10 –...

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