ORIGIN OF THE CHERT IN THE BOONE FORMATION, LOWER MISSISSIPPIAN, TRI-STATE AREA, ARKANSAS, MISSOURI AND OKLAHOMA
The source of the silica producing the chert in the lower and upper Boone Formation has been historically assigned a biogenic origin, but recent studies suggest a volcanogenic source. Chemical analyses of composite grains found within the insoluble fraction of the upper Boone carbonates indicate a felsic composition consistent with a quartz-rich granitoid igneous lithology. Elemental data determined by energy dispersive x-ray (EDX) of both lower and upper Boone chert include a significant weight percentage of both aluminum and potassium compositionally consistent with volcanic ash, and unlikely in biogenic silica. Further bulk geochemical and trace elemental evidence of a volcanogenic source of the silica for both penecontemporaneous and later diagenetic chert, which represent entirely different processes of formation, is provided by analyses utilizing a Quadrupole Inductively Coupled Plasma Mass Spectrometer (Q ICP-MS). The volcanogenic silica source is likely an island arc system associated with the Ouachita Mountain chain parallel to the Laurasian cratonic margin. This volcanogenic silica also produced the Arkansas Novaculite that has an equally high weight percentage of aluminum and potassium, and certainly does not represent a biogenic silica deposit.