Two igneous bodies were encountered during the drilling of the Michigan Basin deep drill hole. The upper body (unit 1) extended from 4970 to 4998 m, while the lower body (unit 2) was observed from 5252 m to the bottom of the hole at 5324 m. Samples used in this investigation were taken at 1.5-m intervals in the core section from 5306 to 5322 m. In addition, one sample from the lower contact of unit 1 was examined. The assemblage observed in unit 2 consists of clinopyroxene-chlorite-albite-epidote-actinolitesphene, while the one sample from unit 1 contains albite-chlorite-carbonate-epidote. Both of these assemblages can be characterized as spilitic and are representative of conditions which prevail during greenschist facies metamorphism. Comparison of the compositions of the various phases coexisting in the two assemblages with published experimental studies suggests conditions of equilibration of approximately 450¿C and a fluid pressure of 1--2 kbar.