PETROLOGICAL AND GEOCHRONOLOGICAL INVESTIGATION OF THE BLUE BALL LAMPROITE NEAR WALDRON, ARKANSAS, USA

This project involves the collection and analysis of lamproite rock samples from the Blue Ball Lamproite Dike near Waldron, AR to determine if these rocks are diamond-bearing and if the emplacement of this lamproite body is coincident with other lamproite bodies in Arkansas. Samples were prepared into thin sections using the UALR Rock Preparation Lab and petrographically examined to determine mineral assemblage. Examination of this rock revealed the presence of highly fractured, deformed, and altered olivine phenocrysts containing serpentine growth within olivine fractures, a primary matrix of phlogopite with accessory apatite, perovskite, and opaque minerals. A small amount of secondary calcite is present within thin veins found throughout the sample. Chunks of lamproite have also been crushed and processed using mineral separation techniques (i.e. jaw crusher, disc mill, water table, and magnetic separation) to collect zircons for geochronology analysis.

The occurrence of lamproite in Arkansas is very unusual, with lamproite being found in only a few locations in the state. Emplacement of lamproite requires ejection from the deep mantle into the shallow crust at supersonic speeds (!); a massive type of eruption that has never been directly observed. The most well-known lamproite body in Arkansas is the Prairie Creek Lamproite (also known as Crater of Diamonds State Park). Like Prairie Creek, the Blue Ball Lamproite may be diamond-bearing. With some compositional similarities between the Blue Ball and Prairie Creek Lamproites, the age of emplacement of the Blue Ball Lamproite has been previously assumed to be coincident with the Prairie Creek Lamproite during the mid-Cretaceous (~100 Ma). Continued analysis of these samples will determine if these assumptions are reasonable, or if new interpretation of the emplacement history of the Blue Ball Lamproite is required.