Geology, mineralogy, and petrology of the contact zone, southern Magnet Cove igneous complex, Hot Spring County, Arkansas

The contact zone of the southern Magnet Cove Igneous Complex was mapped in detail in the Martin Marietta Materials' Jones Mill quarry. Rocks in the endocontact zone include garnet pseudoleucite syenite, garnet nepheline syenite, nepheline syenite, nephelinolite, phonolite, intrusion breccias, and a xenolithic aphanite. These subvulcanic rocks developed at low pressure/variable volatile pressure conditions. They are cut by dikes of phonolite, pseudoleucite phonolite, nephelinite, and lamprophyres. In the exocontact zone, the folded Mississippian strata of Arkansas Novaculite and Stanley Group are low-grade hornfels facies, contact metamorphic metacherts, metasandstones and hornfels. Twenty-five lamprophyre dikes occur in the country rocks.; Polarization-optical microscopic examinations results are presented and documented. Quantitative XRD/Rietveld determinations and whole rock chemical analyses are given for selected samples. For the first time this XRD-technique was applied to rocks from the MCIC. In combination, these analytical techniques allow recognition, refinement, and valuation of the magmatites and their history.