GEOCHEMICAL EXAMINATION OF GARNETS FROM THE PRARIE CREEK LAMPROITE, MURFREESBORO, ARKANSAS

The Prairie Creek Lamproite is a 95 million year old diamondiferous lamproite intrusion located in southwest Arkansas near the town of Murfreesboro. The area surrounding the pipe is maintained by the Arkansas Department of Parks and Tourism as a publicly accessible state park known as Crater of Diamonds State Park. This park was first opened in 1972, and is the only publicly available site to mine diamonds in the world. Since opening, over 30,000 diamonds have been recovered by visitors to the park.

The purpose of this research is to geochemically examine garnet-bearing samples from the Prairie Creek Lamproite to contribute to the understanding of lamproite formation. Preliminary geochemical analyses by scanning electron microscopy (SEM) were performed on individual garnet crystals provided by Crater of Diamonds State Park. Though analysis of individual garnet grains indicated that each was chemically homogeneous, there was significant compositional variation among the garnets analyzed. We are continuing the process of collecting, processing and analyzing additional garnet-bearing samples, both from surface exposures at the lamproite body itself, and from core samples provided by the Arkansas Geological Survey.