(SFM) Igneous Suite -- St. Francois Mountains, Southeastern Missouri


(SFM) Igneous Suite -- St. Francois Mountains, Southeastern Missouri


This collection is composed of igneous volcanic and intrusive rocks from the St. Francois Mountains of Missouri. The variation within the collection can be used to explain the geologic history of the area. The St. Francois Mountains batholith was formed by granitic intrusions into Precambrian rhyolites, tuffs, and breccias. Then basalt, diabase, and porphyritic intrusions cut the granitoids.


January 20, 1969


Western Minerals, Inc.

Spatial Coverage

St. Francois Mountains, Ozark region of Southeastern Missouri

Temporal Coverage

Precambrian (1.476 Ga)

Accrual Method

Purchased from Western Minerals Inc.


Start here: 

Bickford, M.E. and Mose, D.G., 1974, Geochronology of Precambrian rocks, St. Francois Mountains, South eastern Missouri: GSA Special Papers 1975, v. 165, p. 1-48 doi: http://dx.doi.org/10.1130/SPE165-p1

  • Early study of the geochronology of the Precambrian rocks within the St. Francois mountains. Provides further insight upon the sequence discussed in the dscription.

Meert, J.G. and Stuckey, W., 2002, Revisiting the paleomagnetism of the 1.476 Ga St. Francois Mountains igneous province, Missouri: Tectonics v. 21, Issue 2, p. 1-19 doi: http://dx.doi.org/10.1029/2000TC001265

  • Information acquired from paleomagnestism studies of the St. Francois igneous provence has proven fruitful for determining an acient paleomagnetic pole for Laurentia. 

Menuge, J.F, Brewer, T.S., and Seeger, C.M., 2002, Petrogenesis of metaluminous A-type rhyolites from the St. Francois Mountains, Missouri and the Mesoproterozoic evolution of the southern Laurentian Margin: Precambrian Research, volume 113, issues 3-4, p. 269-291 doi: http//dx.doi.org/10.1016/S0301-9268(01)00211-X

  • Trace elemental analysis of Precambrian rocks from the SFM provide insight into the condition of crystallization and the elemental constituents which played a role into the interesting history of this rhyolitic provence. 

Rohs, R. C, and Van Schmus, W.R., 2006, Isotopic connection between basement rocks exposed in the St. Francois Mountains and the arbucks Mountains southern mid-continent, North America: International Journal of Earth Sciences, volume 96, Issue 4, p. 599-611
doi: http://dx.doi.org/10.1007/s00531-006-0123-5
  • Radiometric study of the SFM provence and the Arbuckle mountains of southern Oklahoma suggests a common source. 

Wenner, D. and Taylor Jr., H.P., 1976, Oxygen and hydrogen isotope studies of a Precambian granite-rhyolite terrane, ST. Francois Mountains, southeastern Missouri: Geological Society of America bulletin v. 87, no. 11, p.1587-1598
doi: http://dx.doi.org/10.1130/0016-7606
  • Isotopic analysis of oxygen isotope content within mineral grains within the Precambrian rhyolitic rocks of the SFM yields data that suggests Precambrian oceans were similar to modern day meteoric oceans.

Collection Items

St. Francois Mountains Western Minerals Supplementary Information
OCR PDF of supplemental information for the St. Francois Mountains collection.

Red Granophyre (fine grained)
Hand Sample: Holocrystalline phaneritic, porphyritic and granophyrite rich in alkali feldspar. Larger crystals or pockets of biotite and quartz also present. Rock is weathered to orange brown. Contact on one side with dark black-brown quartz-rich…

Hand Sample: Holocystalline, phaneritic, medim-grained granitoid with subhedral grains of smoky quartz, plagioclase feldspar, potassium feldspar, and biotite. Weathering to red-yellow on some surfaces.

Diorite Porphyry Dike
Hand Sample: Holocrystalline, phaneritic, porphyritic, diorite with quratz crystals up to 3mm in diameter set in a field of smaller light gray, and dark gray crystals. Some small oxidized pyrite crystals. Very weathered on two sides to orange yellow…

Graniteville Granite
Hand Sample: Holocrystalline, medium-grained phaneritic granite with smoky quartz, potassium feldspar, and biotite

Hand Sample: Porphyritic rhyolite with medium-grained potassium feldspar and plagioclase feldspar phenocrysts in a dark red-brown matrix. Weathers with an orangish tinge.

Granite (pink medium-grained)
Hand Sample: Holocrystalline, phaneritic, medium-grained granitoid with an abundance of alkali feldspar. Other minerals include quartz and biotite. Some chemical weathering has produced a white coating.

Granite (medium-grained)
Hand Sample: Holocrystalline, phaneritic, medium-grained granite composed predominantly of smaller alkali feldspar crystals with larger crystals of smoky quartz, biotite, and plagioclase feldspar

Red Granite (coarse grained)
Hand Sample: Holocrystalline, coarse-grained, phaneritic granite with dominant alkali feldspar crystals, as well as quartz and plagioclase feldspar. Veins or pockets of dark brown-black material dispersed intermittently.

Diabase Porphyry Dike
Hand Sample: Hypocrystalline, porphyritic, diabase with subhedral plagioclase and alkali feldspar (weathered to green) crystals approximately 1cm in length. Matrix is brown-black color. Weathered to white. Intensive weathering on one side to light…

Basalt Dike
Hand Sample: Aphanitic brown-black basalt with microcrystalline inclusions of quartz and alkali feldspar. Weathers to yellow orange. Part of a dike cross cutting granite at the Cornwall Quarry.

Medium Coarse Grained Adamellite
Hand Sample: Holocrystalline, phaneritic, fine-to-medium-grained quartz monzonite. Mineralogy includes large plagioclase laths up to 8mm in length, quartz, alkali feldspar, biotite. Very large crystals of a dark material up to 3cm in length.…

Hand Sample: Holocrystalline fine-to-medium-grained phaneritic rhyolite with quartz, biotite, and plagioclase crystals generally no larger than 2mm. Weathers to brownish-orange.

Stouts Creek Rhyolite (VanEast group)
Hand Sample: Hypocrystalline, porphyritic rhyolite. 20% subhedral to anhedral biotite, quartz, and microcline (sanidine) phenocrysts. 80% grey-brown groundmass. Massive.

Skrainka Diabase
Hand Sample: Porphyritic diabase with light crystals in a dark-grey-to-black groundmass. Plagioclase 45%, Pyroxene 45%, Hornblende 5%, Olivine and Biotite 5%

Brown Mountain intrusive Rhyolite
Hand Sample: Porphyritic orange-pink rhyolite. Dominantly potassium feldspar with some black crystals. Weathers to brown-black and yellow-brown.

Diorite (coarse-grained)
Hand Sample: Porphyritic (or coarse-grained phaneritic) diorite with coarse-grained white plagioclase laths up to 1cm and some black mineral. Weathering to rust-orange color.

Ketcherside Tuff
Hand Sample: Aphanitic, pyroclastic grey-black tuff. Conchoidal fracture pattern from a strike-point on one edge. Weathers to yellow-brown.

Devonite (diabase-porphyry)
Hand Sample: Porphyritic diabase with coarse to very coarse grained subhedral pink-green plagioclase laths approximately 3cm in length set in a gray-black matrix. Inclusions of matrix present within plagioclase laths. Weathers to orange-brown.

Hand Sample: Aphanitic, grayish-white with some patches of fine-grained grey crystals. Weathers to medium yellow-brown.
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