Igneous rocks

Includes undifferentiated altered sedimentary rocks of Paleozoic age at Granite Mountain, Pulaski County, and Mufreesboro, Pike County. Acid to intermediate - Nepheline syenite complexes at Magnet Cove and Potash Sulfur Springs, stocks at Granite Mtn., explosion breccias, and dikes and sills (principally trachyte,tinguaite, phonolite, some ranging from syenite to diabase). Basic to ultrabasic - Lamproite pipes (Murfreesboro, Pike County) and dikes and sills (principally lamprophyres of fourchite, ouachitite, and monchiquite).
State Arkansas
Name Igneous rocks
Geologic age Cretaceous
Lithologic constituents
Major
Igneous > Plutonic > Foidal-syenitic > Nepheline-syenite (Stock or pipe)
Igneous > Volcanic > Alkalic-volcanic (Dike or sill)
Igneous > Plutonic > Intrusive-carbonatite (Stock or pipe)The carbonatite complexes have yielded a vareity of commodities including:magnetite (iron), titanium, rare earths, molybdenum, uranium, barite and phosphate. Magnet Cove is known to mineral collectors for an unusual variety of mineral species.
Minor
Igneous > Hypabyssal > Lamprophyre (Stock or pipe)
Igneous > Plutonic > Syenitic > Syenite (Stock or pipe)
Igneous > Volcanic > Felsic-volcanic > Trachyte (Dike or sill)
Comments Alkalic ring dike igneous complexes: Magnet Cove (Hot Spring County)-core of carbonatite-ijolite, inner ring of alkalic extrusives and outer ring of nepheline syenite; Potash Sulfur Springs (Garland County)-mafic alkalic rocks, carbonatite, nepheline syenite and syenite. Both intruded during Mesozoic time into Paleozoic shale, sandstone and novaculite.
References

Haley, B.R., Glick, E.E., Bush, W.V.; Clardy, B.F.; Stone, C.G.; Woodward, M.B., and Zachry, D.L., 1993, Geologic Map of Arkansas: U.S.Geological Survey Special Geologic Map, scale 1:500,000.

NGMDB product
Counties Garland - Hot Spring - Pike - Pulaski - Saline