UNITED STATES DEPARTMENT OF INTERIOR GEOLOGICAL SURVEY Radioactive mineral spring precipitates, their analytical and statistical data, and the uranium connection by Robert A. Cadigan and J. Karen Felmlee Open-File Report 82-743 1982 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards. Contents Page Abstract.................................................................... 1 Introduction................................................................2 Purpose and scope of investigation.....................................2 Geographic and geologic setting........................................ 3 Previous work.......................................................... 3 Acknowledgments........................................................ 6 Mineral spring precipitate samples......................................... 17 Location.............................................................. 17 Morphology............................................................ 17 Sampling methods...................................................... 22 Analytical methods.................................................... 26 Radiogeochemistry..........................................................28 Statistical analysis.......................................................30 Data.................................................................. 30 Element abundances.................................................... 31 Correlation of element abundances..................................... 69 Factor analysis....................................................... 99 Carbon isotope data....................................................... 113 A seismic model...........................................................114 Summary...................................................................117 References cited.......................................................... 120 Illustrations Figure 1. Map showing physiographic province boundaries and general area sampled................................................... 4 2. Sample locality map............................................. 18 3. Photograph showing travertine deposits at Thermopolis, Wyoming....................................................... 19 4. Composite photograph of Doughty Springs site, Colorado..........20 5-8. Photographs showing:.............................................. 5. Precipitates at Doughty Springs................................. 21 6. Travertine deposits at Yellow Soda Spring and Taylor Soda Springs sites, Colorado....................... 23 7. Precipitates at Wilson Health Springs, Utah.....................24 8. Travertine deposits at Soda Dam Springs, New Mexico and Poncha Hot Springs, Colorado...................25 9-12. Histograms showing frequency distributions for: 9. eU, U, Th, S, Al, Fe, Ca, K, and Na.............................65 10. Mg, Si, Ti, As, B, Ba, Be, Ce, and Co...........................66 11. Cr, Cu, Ga, Ge, La, Mn, Mo, Nb, and Ni..........................67 12. Pb, Sc, Sr, V, W, Y, Yb, Zn, and Zr.............................68 13. Map showing mineral spring sites with high values of U, Ba, Fe, Mn, Ra, and S.........................................75 14-25. Scatter plots showing correlation for:............................ 14. U vs. Th........................................................81 15. Si vs. Al.......................................................82 16. Si vs. Ti.......................................................83 17. Al vs. V........................................................84 18. Ba vs. Ra(eU)...................................................85 19. Ba vs. Ca.......................................................86 ii Illustrations continued Page 20. B vs. Li........................................................87 21. Fe vs. U........................................................88 22. Be vs. As.......................................................89 23. Fe vs. Ra.......................................................90 24. V vs. U.........................................................91 25. S vs. Ca........................................................92 26. Diagrammatic sketch of the relationship of radioactive mineral springs to tectonic activity in an erogenic area............. 116 Tables Table 1. Index of sample localities by States.............................7 2. Chemical elements used in the geochemical study of radioactive mineral spring precipitates, methods of analysis, reporting and detection limits.............................................. 27 3. Elements and numbers of valid values, qualified values, total analyses and percent valid values.............................29 4. Geochemical data for 297 samples of mineral spring precipitates collected at 105 localities in 10 States......................32 5. Summary of geometric means, maximum and minimum values, estimated range of means, and number of analyses used in statistical computation for each element..................................64 6. Springs with precipitates containing the most Ra................70 7. Springs with precipitates containing the most U.................71 iii Tables continued Page 8. Springs with precipitates containing the most Ba.................72 9. Springs with precipitates containing the most Fe.................73 10. Springs with precipitates containing the most Mn.................74 11. Values of Pearson's correlation coefficient, _r_, for all possible pairs of variables.............................................77 12. Computed z_ correlation coefficients at the 5% and 1% levels of s ignif icance................................................... 94 13. Standard or z_ correlation matrix constructed from the _r_ correlation data and number of pairs listed in table 11.................... 95 14. Reordered varimax factor loadings for seven factors, with tentative interpretations of geochemical factors........................ 100 15. Sample factor scores............................................ 105 16. Radioactive mineral springs: C 1 3 /C 1 2 Ratios in - C0 - C0..............................................115 iv Radioactive mineral spring precipitates, their analytical and statistical data, and the uranium connection by Robert A. Cadigan and J. Karen Felmlee ABSTRACT Major radioactive mineral springs are probably related to deep zones of active metamorphism in areas of erogenic tectonism. The most common precipitate is travertine, a chemically precipitated rock composed chiefly of calcium carbonate, but also containing other minerals. The mineral springs are surface manifestations of hydrothermal conduit systems which extend downward many kilometers to hot source rocks. Conduits are kept open by fluid pressure exerted by carbon dioxide-charged waters rising to the surface propelled by heat and gas (CC^ and steam) pressure. On reaching the surface, the dissolved carbon dioxide is released from solution, and calcium carbonate is precipitated. Springs also contain sulfur species (for example, F^S and HS"), and radon, helium and methane as entrained or dissolved gases. The HS" ion can react to form hydrogen sulfide gas, sulfate salts, and native sulfur. Chemical salts and native sulfur precipitate at the surface. The sulfur may partly oxidize to produce detectable sulfur dioxide gas. Radioactivity is due to the presence of radium-226, radon-222, radium- 228, and radon-220, and other daughter products of uranium-238 and thorium- 232. Uranium and thorium are not present in economically significant amounts in most radioactive spring precipitates. Most radium is coprecipitated at the surface with barite. Barite (barium sulfate) forms in the barium-containing spring water as a product of the oxidation of sulfur species to sulfate ions. The relatively insoluble barium sulfate precipitates and removes much of the radium from solution. Radium coprecipitates to a lesser extent with manganese-barium- and iron-oxy hydroxides. R-mode factor analysis of abundances of elements suggests that 65 percent of the variance of the different elements is affected by seven factors interpreted as follows: (1) Silica and silicate contamination and precipitation; (2) Carbonate travertine precipitation; (3) Radium coprecipitation; (4) Evaporite precipitation; (5) Hydrous limonite precipitation and coprecipitated elements including uranium; (6) Rare earth elements deposited with detrital contamination (?); (7) Metal carbonate adsorption and precipitation. Economically recoverable minerals occurring at some localities in spring precipitates are ores of iron, manganese, sulfur, tungsten and barium and ornamental travertine. Continental radioactive mineral springs occur in areas of crustal thickening caused by overthrusting of crustal plates, and intrusion and metamorphism. Sedimentary rocks on the lower plate are trapped between the plates and form a zone of metamorphism. Connate waters, carbonate rocks and organic-carbon-bearing rocks react to extreme pressure and temperature to produce carbon dioxide, and steam. Fractures are forced open by gas and fluid pressures. Deep-circulating meteoric waters then come in contact with the reactive products, and a hydrothermal cell forms. When hot mineral-charged waters reach the surface they form the familiar hot mineral springs. Hot springs also occur in relation to igneous intrusive action or volcanism both of which may be products of the crustal plate overthrusting. Uranium and thorium in the sedimentary rocks undergoing