| State | Missouri |
|---|---|
| Name | St. Francois Mountains intrusive suite (subvolcanic, alkali granitic ring complexes) |
| Geologic age | Precambrian Y |
| Lithologic constituents | Major
Igneous > Plutonic > Granitic > Alkali-feldspar-granite (Batholith)
|
| 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. |
| References | Howe, W.B. and Koenig, 1961, The Stratigraphic Succession in Missouri: Missouri Geological Survey and Water Resources, Vol XL. 2nd Series. |
| NGMDB product | |
| Counties | Bollinger - Camden - Carter - Iron - Madison - Reynolds - Sainte Genevieve - Saint Francois - Washington - Wayne |