Lherzolite xenolith bearing flows from the east otago province: Crystal fractionation of upper mantle magmas

Abstract

The Waipiata Volcanic Formation comprises a large number of minor eruptive vents peripheral to the Dunedin volcano. Many of the flows and associated pyro‐clastic deposits contain spinel‐lherzolite xenoliths. The lherzolite‐bearing flows have relatively low Mg numbers and are the result of low degrees of partial melting followed by fractional crystallisation in the upper mantle. Early fractionation is controlled by tschermakitic clinopyroxene with minor olivine and titanomagnetite, whereas the more evolved flows also include kaersutite as a significant fractionating phase. © 1991 Taylor & Francis Group, LLC.