Mafic and Ultramafic Nodules - Introduction

Abstract

The great interest in the small nodules found in alkalic lavas and kimberlite diatremes lies in the hope that they will provide information about the composition and mineralogy of the earth's mantle. They have already been discussed by several contributors, including O'Hara, Chapter 5-IV; Dawson, 8-II and 8-V; Davidson, 8-III; Watson, 8-IV; Upton, 9-II; and von Eckermann, 9-IV. The nodules have been interpreted as representative of primary mantle material; as residual mantle material after extraction of basalt; as xenoliths picked up within the earth's crust; as cumulates from primary basaltic magma formed as bottom cumulates in temporary reservoirs, or formed marginally during upward flow.

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