LAMPROITES AND ANIMAL HEALTH

Lamproites are mantle-derived volcanic rocks enriched in K, Na, and Ca and are characterized by high K₂O/Na₂O ratios. They occur as volcanic pipes—similar to the diamond-yielding kimberlites—and may be forced up 100 km or more above the mantle zone where they originate, to form outcrops. One such occurrence, in southeastern Kansas in Woodson County, forms a dome caused by the intrusion of lamproite, about 100 Ma years ago, into a sequence of upper Pennsylvanian (~300 Ma) sedimentary rocks comprising sandstone, siltstone, and shale with minor limestone, belonging to the Douglas Group (Berendsen and Blair, 1991). Mineralogically the Kansas lamproite, known as the Hills Pond lamproite (Wagner, 1954), is dominated by olivine (~75%), and phlogopite (up to 20%) with less than 5% pyroxenes and spinel group minerals (Benedictus, et al; 2008). Owing to the preponderance of ferromagnesian minerals lamproites are highly susceptible to weathering and turn into lose aggregates after several weeks of exposure to the atmosphere. This results in: (a) elements like K, Ca, Mg, Fe and other nutrients becoming readily bioavailable in the environment, and (b) easy extraction of the lamproite ore without drilling and blasting. An interesting aspect of Kansas lamproite is its use in cattle feed. Local farmers have been aware of its beneficial effects to animal health for a long time, but it was not until 1982 that Mico-Lite, LLC, initiated commercial exploitation of lamproite. The company extracts about 70,000 metric tons of lamproite that occurs as sills up to 35 m thick; processes it to separate phlogopite, and sells it as a supplement to cattle feed to provide essential nutrients, such as K, Mg, and Fe. The paper discusses the geology, geochemistry, mining, and processing of lamproite at Micro-Lite manufacturing plant, along with nutrient value of the lamproite-derived product to animal health.