Precambrian volcanics associated with the taum Sauk Caldera, St. Francois Mountains, Missouri, U.S.A.
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Petrological studies of 12 volcanic rock units in the northeast segment of the Taum Sauk Caldera, the major structural feature in the western part of the St. Francois Mountains, indicate that they were probably derived from the same magma chamber. These calc-alkalic rocks become progressively silica and alkali rich and calcium poor from the base to the top of the stratigraphic column. In the part of the northeast segment of the caldera studied in detail, the extrusives are over 5 thick and have a volume of over 500 km3. Rock units consisting of ash-flow tuffs, bedded airfall tuffs and lava flows were apparently deposited within a single episode of volcanic activity, since no signs of extensive erosion were observed among them. Although the rocks are completely devitrified, the preservation of pyroclastic and flow features is excellent.
These volcanics are exposed representatives of a 1.3–1.4 b.y. old belt of volcanics and associated plutons which extends from southern Ohio to the Texas Panhandle any may represent a belt of continental accretion.
KeywordsMagma Chamber Water Vapor Pressure Alkali Feldspar Plagioclase Phenocryst Quartz Phenocryst
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- Anderson, R. E., 1962,Igneous petrology of the Taum Sauk area, Missouri. St. Louis, Mo., Washington Univ., Ph. D. thesis, available on film from University Microfilms, Inc., Ann. Arbor, Mich.Google Scholar
- -----, 1970,Ash-flow tuffs of Precambrian age in southeast Missouri. Missouri Div. Geol. Surv. and Water Res., Rept. Inv. 46, 50 p.Google Scholar
- Bickford, M. E. andA. L. Odom, 1968,Rb-Sr geochronology of igneous events in the Precambrian of the St. Francois Mountains, southeastern Missouri (abs). Program, Annual Meeting, Geol. Soc. Amer. Mexico City, Mex., p. 27.Google Scholar
- Haworth, E., 1894,The crystalline rocks of Missouri, including a section on general geology of the Missouri crystalline area, by C. R. Keys. Missouri Geol. Surv.,8, p. 81–222.Google Scholar
- Hayes, W. C., 1959,Chemical analyses, Precambrian rocks of Missouri. Missouri Div. of Geol. Surv. and Water Res. (multilithed).Google Scholar
- Lidiak, E. G., R. F. Marvin, H. H. Thomas, andM. N. Bass, 1966,Geochronology of the mid-continent region, United States, part 4, eastern area. Jour. Geophys. Research,71, p. 5409–5426.Google Scholar
- Lipman, P. W., R. L. Christiansen, J. T. O’Connor, 1966,A compositionally zoned ash-flow sheetin southern Nevada, in shorter contributions to general geology. U. S. Geol. Surv. Prof. Paper 524-F, 47 p.Google Scholar
- Mose, D. G., 1971,Chronology of Precambrian volcanic rock units in the center of the St. Francois Mountains; Missouri. Lawrence, Kansas, Kansas Univ., Ph. D. Thesis.Google Scholar
- Muehlberger, W. R., C. E. Hedge, R. E. Denison, andR. F. Marvin, 1966,Geochronology of the midcontinent region, United States; Part 2, southern area. J. Geophys. Res.,71, p. 5409–5428.Google Scholar
- Orville, P. M., 1967,Unit-cell parameters of the mirocline-low albite and sanidine-high albite solid solution series. Amer. Min.,52, p. 55–86.Google Scholar
- Ross, C. S., andSmith, R. L., 1961,Ash-flow tuffs — Their origin, geologic relations and identification. U. S. Geol. Survey Prof. Paper 366, 81 p.Google Scholar
- Schoolcraft, H. R., 1819,A view of lead mines of Missouri (including some observations on the mineralogy, geology, geography, antiquities, soil, climate, population, and production of Missouri and Arkansas and other sections of the western country). New York, 299 pp., 3 engravings.Google Scholar
- Slemmons, D. B., 1962,Determination of volcanic and plutonic plagioclases using a three-or four-Axis universal stage. Geol. Soc. Amer. Special Paper 69, 64 p.Google Scholar
- Smith, J. R., andH. S. Yoder, Jr., 1956,Variations in x-ray powder diffraction patterns of plagioclase feldspars. Amer. Mineral.,41, p. 632–647.Google Scholar
- Tolman, C. andF. Robertson, 1960,Precambrian geology map of Missouri (preliminary). Missouri Div. Geol. Surv. and Water Res.Google Scholar
- -----, 1969,Exposed Precambrian rocks in southeast Missouri. Missouri Div. Geol. Surv. and Water Res., Rept. Inv. 44, 68 p.Google Scholar
- Tuttle, O. F., andN. L. Bowen, 1958,Origin of granite in the light of experimental studies. Geol. Soc. Amer. Mem. 74, 153 p.Google Scholar