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 Shale reactions are important as sources and sinks for trace elements.

Element Groups (Families) Alkali EarthAlkaline EarthTransition Metals Rare EarthOther MetalsMetalloids Non-MetalsHalogensNoble Gases

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

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

Method of sequential extraction (Tessier et al., 1979) 1 gram of powdered rock EXCHANGEABLE1 m MgCl 2 CARBONATE1 m NaOAc HFO0.04m NH 2 OH·HCl - HOAc ORGANIC0.02m HNO 3 – H 2 O 2 CRYSTALLINEHF – HClO 4

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

La VA25-a VA25-b VA25-c Pb VA25-a VA25-b VA25c U VA25-a VA25-b VA25-c Replicate Analyses Ex Car HFO ORGXTL ppm ppm ppm

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

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

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

Verendrye

Shale Fractionation Variable Exch Carb HFO OrganicXtl Smectite Illite Lanthanum (LREE) ppm SD-25 SD-24 VA-25 VA-24

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

ppm Glauconite Ex Carb HFO OrgXtl

ppm

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

La Verendrye Gd Yb org XTL car hfo Illite

Hornerstown La Gd Yb org XTL hfo Glauconite

SD-25 SD-24 VA-25 VA-24 Yttrium ppm JHB-2 JHA-1 JN ppm EX Car Hfo Org XTL

Th SD-25 SD-24 VA-25 VA ppm U SD-25 SD-24 VA25 VA ppm ppm EX Car Hfo Org XTL

U Th JN-1 JHA-1 JHB-2 JN-1 JHA-1 JHB ppm ppm

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.

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