Geochemical Study of an Equine Enterolith, Medina County, Ohio

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An intestinal concretion (enterolith) was recovered during necropsy of a horse from Medina County, Ohio. The object is approximately spherical in shape and measures 9 X 8 X 7 cm in diameter. It is composed of struvite (NH4MgPO4 • 6H2O). The monohydrate dittmarite was not found. In addition to Mg and P, significant concentrations (^500 ppm) of Ca, K, and Fe and lesser amounts (^500 ppm) of Na, Mn, Rb and Sr were measured. The concretion is concentrically zoned with concentrations of Ca, Sr, Fe and Na decreasing from the inside out whereas those of K and Rb increase. The concentrations of Mg and Mn appear to be constant within analytical uncertainty. The cause for the chemical zonation of the enterolith is not known. The Rb/Sr ratio of the struvite is high compared to that of calcium phosphate and ranges from 4.9 to 20.7. The 87Sr/86Sr ratio is 0.7101 ± 0.0003 which leads to the interpretation that most of the Sr available to plants in the soil of Medina County was derived from particles of Devonian limestone (87Sr/86Sr = 0.7083) and lesser amounts from feldspar (87Sr/86Sr = 0.7141) and clay (87Sr/86Sr = 0.7345).


Author Institution: Department of Geology and Mineralogy, The Ohio State University



The Ohio Journal of Science. v83, n1 (March, 1983), 54-59