Abstract

Electron probe analyses show that the pyroxenes of the peridotite-mylonites are significantly enriched in alumina when compared with the pyroxenes in the dunites described by Ross et al (1954), but are comparable to the Lizard pyroxenes and to those in olivine nodules of basalts. The closest comparison of the latter is with nodules of a mugearite from Ichinomegata, Akita, Japan. In the groundmass of the amphibole peridotite-mylonites, clinopyroxene is extremely rare, and the variation of the amphibole content is estimated to range from <10 percent to a maximum of 50 percent. The idea that olivine nodules are residua in the fractional melting process and now appear in a basaltic liquid which was alkalic at its original depth and pressure is supported.

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