gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1994.58A.2.129 1.3 Ga Mafic Magmatism of the St. Francois Mountains of SE Missouri: Implications for Mantle Composition Beneath Mid-Continental USA Rämö O. T. Boyd W. W. The University of Helsinki, Dept. of Geology, P.O.Box II, FIN-00014, Helsinki, Finland Vaasjoki M. Geological Survey of Finland, Betonimiehenkuja 4, FIN-02150, Espoo, Finland Cameron R. L. 1344 N. Bluff Rd., Collinsville, IL 62234, USA Ryckman D. A. Dept. of Geology and Geophysics, University of Missouri - Rolla, Rolla, MO 65401, USA August–September 1994 58A 2 754 755 Copyright © 1994, The Mineralogical Society 1994