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THE DISTRIBUTION OF RARE EARTH AND TRACE ELEMENTS IN FRACTIONS OF MARINE SHALE

THE DISTRIBUTION OF RARE EARTH AND TRACE ELEMENTS IN FRACTIONS OF MARINE SHALE. Janet Frey D. E. Grandstaff Department of Geology Temple University Philadelphia, PA. Why Shale ? Shales comprise 60% or more of sedimentary rocks

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THE DISTRIBUTION OF RARE EARTH AND TRACE ELEMENTS IN FRACTIONS OF MARINE SHALE

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  1. THE DISTRIBUTION OF RARE EARTH AND TRACE ELEMENTS IN FRACTIONS OF MARINE SHALE Janet Frey D. E. Grandstaff Department of Geology Temple University Philadelphia, PA

  2. Why Shale? • Shales comprise 60% or more of sedimentary rocks • Shale reactions are important as sources and sinks for trace elements.

  3. Why Rare Earth Elements? • Not much is know about mobility of REE elements in earth surface systems. • REE have commonly been considered conservative in natural waters • – water mass tracers. • However, REE may interact with sediments. • REE as analogs in nuclear waste disposal • (Neptunium, Americium) • Radioactive REE in short-term waste release

  4. However trace elements may be contained in a variety of phases: Ion exchange sites on clays Adsorbed on hydrous ferric oxides Adsorbed to organic matter Co-precipitated in carbonates Bound in crystalline minerals The phase in which they are contained determines their environmental mobility. (pH, redox, ionic strength) REE concentrations in bulk shales are fairly well known.

  5. Method of sequential extraction (Tessier et al., 1979) 1 gram of powdered rock EXCHANGEABLE 1 m MgCl2 CARBONATE 1 m NaOAc HFO 0.04m NH2OH·HCl - HOAc ORGANIC 0.02m HNO3 – H2O2 CRYSTALLINE HF – HClO4

  6. Shale samples: Pierre Shale (K) South Dakota Navesink (K) New Jersey Hornerstown (K-T) New Jersey

  7. Replicate Analyses ExCarHFO ORG XTL VA25-a VA25-b VA25-c U 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 ppm VA25-a VA25-b VA25c Pb 0 2 4 6 8 10 ppm VA25-a VA25-b VA25-c La 0 2 4 6 8 10 12 14 ppm

  8. Verendrye 1 0.1 0.01 Total XTL Org Car Hfo (REE/NASC) La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

  9. Sharon Springs 10 Sum Exch Org XTL Hfo Car 1 REE / NASC 0.1 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 0.01

  10. Navesink 10 Total XTL Org Hfo Car Ex 1 REE / NASC 0.1 0.01 0.001 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

  11. Verendrye

  12. Shale Fractionation Variable Lanthanum (LREE) ExchCarbHFOOrganicXtl Smectite Illite ppm SD-25 SD-24 VA-25 VA-24 10 30

  13. Gadolinium (MREE) EX Car Hfo Org Xtl SD-25 SD-24 VA-25 VA-24 ppm

  14. Ex Glauconite CarbHFOOrgXtl ppm

  15. ppm

  16. Sharon Springs Yb Gd La Ex XTL Carb car Hfo Org Smectite

  17. Verendrye La Yb Gd car hfo XTL org Illite

  18. Hornerstown Yb La Gd hfo XTL org Glauconite

  19. Yttrium SD-25 SD-24 VA-25 VA-24 EX Car Hfo Org XTL 0 10 20 30 40 50 ppm JHB-2 JHA-1 JN-1 0 5 10 15 20 ppm

  20. SD-25 SD-24 VA-25 VA-24 0 50 100 150 200 250 300 ppm EX Car Hfo Org XTL U 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 ppm SD-25 SD-24 VA25 VA24 Th 0 5 10 15 20 25 ppm

  21. JN-1 JHA-1 JHB-2 U 0 1 2 3 4 5 6 7 8 9 10 ppm JN-1 JHA-1 JHB-2 Th 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 ppm

  22. Conclusions • Fractionation of REE/TE in shales is highly variable • Depends on mineralogy, organic content • In some cases <50% of REE in refractory phases • Carbonate, HFO, Organic and Exchangeable fractions may provide a source of REE and TE that become mobile due to environmental changes in redox, pH and ionic strength. • LREE may be less conservative than HREE; • not reliable tracers. • These reactions should be considered in waste disposal scenarios.

  23. Thanks for listening!

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