Basaltic rocks characterized by nodulelike inclusions of olivine and related minerals are of world-wide occurrence and have long been known, especially in Germany. Everywhere the nodules show a remarkable uniformity of chemical and mineral composition and in this respect are similar to dunites—intrusive rocks of equally wide distribution. This similarily in the chemical and mineral composition of the two modes of occurrence and the wide distribution of both of these, suggest the value of a detailed study. This paper gives the results of a large number of chemical and spectrographic analyses of the minerals in the nodules and in dunites and discusses the mineralogie and geologic relationships. The authors conclude that dunites have been brought up from profound depth by orogenic processes, and olivine-rich nodules have been carried up from the same source by basaltic magmas.

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