Ultramafic nodules and their host rocks from Auckland, New Zealand
- 1 March 1975
- journal article
- research article
- Published by Cambridge University Press (CUP) in Geological Magazine
- Vol. 112 (2), 163-174
- https://doi.org/10.1017/s0016756800045842
Abstract
Ultramafic and mafic nodules are abundant inclusions in Cainozoic alkali basalts at 7 localities in the Auckland Province. Nodule types show a gradation from dunites and pyroxenites through periodotites to eucrites. Bulk chemical variations in the nodules show a wide range in MgO/ΣFeO with a tendency for Al2O3, ΣFeO, CaO and Na2O + K2O to increase as this ratio decreases. These chemical trends, together with published data on the nodules mineralogy and fabric, are consistent with their being interpreted as fragments of the upper mantle.Keywords
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