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ST. FRANCOIS MOUNTAINS INTRUSIVE SUITE (SUBVOLCANIC, ALKALI GRANITIC RING COMPLEXES)

ST. FRANCOIS MOUNTAINS INTRUSIVE SUITE (SUBVOLCANIC, ALKALI GRANITIC RING COMPLEXES)
State Missouri
Name ST. FRANCOIS MOUNTAINS INTRUSIVE SUITE (SUBVOLCANIC, ALKALI GRANITIC RING COMPLEXES)
Geologic age Precambrian [Y]
Comments Includes: Graniteville Granite- Alkali-granite central plutons; Knoblick, Slabtown, and Silvermine Granites- granite, granite porphyry, syenite, and trachyte ring intrusions; Butler Hill and Breadtray Granites- granophyre and alkali-granite subvolcanic massifs. The St. Francois Mountains constitutes an exposed portion of Late Precambrian continental crust. This Precambrian terrane of anorogenic, granitic ring complexes is characterized by the predominance of alkaline-silicic over mafic rocks, and trachytic intermediate rocks. The oldest rocks are the rhyolites intruded by comagmatic granite plutons of an epizonal batholith. Ore deposits within the terrane include: magmatic and hydrothermal deposits of iron-apatite; hypo-xenothermal vein deposits of tungsten, silver, and lead; and vein and replacement deposits of manganese.
Primary rock type granite
Secondary rock type
Other rock types
Lithologic constituents
Major
Igneous > Plutonic > Granitic > Alkali-feldspar-granite (Batholith)
Map references
Middendorf, M. A., and others, 2003, Geologic Map of Missouri: Missouri Geological Survey. Scale 1:500K
Unit references
Howe, W. B. and Koenig, 1961, The Stratigraphic Succession in Missouri: Missouri Geological Survey and Water Resources, Vol XL. 2nd Series.
Counties Bollinger - Camden - Carter - Iron - Madison - Reynolds - Sainte Genevieve - Saint Francois - Washington - Wayne