Prairie Creek (Murfreesboro)

The Prairie Creek diatreme is approximately 700 m in diameter and was formerly considered to be a kimberlite, but is now classified as a lamproite (Scott Smith and Skinner, 1984a). The intrusion comprises three phases: a breccia, a tuff and a massive mica peridotite. The peridotite consists of 36% olivine, 26% glass, 14-21% clinopyroxene, 5-11% phlogopite, 7-8% perovskite, opaque oxides and a little potassic richterite; these phases are described in some detail by Scott Smith and Skinner (1984a). Among the abundant country rock xenoliths within the diatreme are some small, up to 2 cm diameter, mafic ones which contain priderite and titanian potassian richterite (Mitchell and Lewis, 1983). The xenoliths occur in a matrix of mica peridotite, and contain a core dominantly of diopside and titanian potassian richterite with accessory priderite and an outer corona with some amphibole together with phlogopite and minor pyroxene. Mineral analyses are given by Mitchell and Lewis (1983); a geological map and general description will be found in Meyer (1976, p. 387 and Fig. 8). Three smaller intrusions occur to the northeast of Prairie Creek, namely Kimberlite Mine, American Mine and Black Lick. Kimberlite Mine includes a possibly reworked tuff and porphyritic rocks comprising olivine and phlogopite with a groundmass of glass containing variable perovskite, clinopyroxene and possible pseudomorphs after melilite. American Mine also apparently contains a reworked tuff, together with a rock of abundant olivine in a groundmass of phlogopite, clinopyroxene, titanian-potassian-richterite and K-feldspar (Scott Smith and Skinner, 1983).