Comparison of Sm-Nd and U-Pb dating methods in rare-earth and associated minerals from pegmatites
The study was undertaken to explore the applicability of the newly developed Sm-Nd dating method to rare-earth minerals which exhibit relatively large rare-earth-element fractionations and their geological environments, and to compare the results of this dating system with those of the well-developed U-Pb system. A procedure was developed for the chemical separations for radiometric chronology. The Sm-Nd data of the samarskite-xenotime assemblage, Mitchell County, North Carolina, yield a linear array on an evolution diagram; if interpreted as an isochron, the slope of the isochron corresponds to 808 +- 12 My. The U-Pb data of the samarskite-xenotime assemblage indicate that the apparent crystallization and metamorphic ages are strongly dependent upon the isotopic composition of the common lead assumed. The apparent crystallization and metamorphic ages of the assemblage range from 850 to 900 My and from 0 to 250 My, respectively. The single-stage-model age, 808 +- 12 My, of the Sm-Nd data is not consistent with the apparent crystallization age, 850-900 My, of the U-Pb data. The Sm-Nd and U-Pb data of the fergusonite assemblage, Ytterby, Sweden, indicate that the assemblage was crystallized 1.80 Gy ago. These data as well as the physical appearance of the mineral crystals also indicate that both the Sm-Nd and U-Pb dating systems in the assemblage have been disturbed by relatively recent weathering.
- Research Organization:
- Carnegie-Mellon Univ., Pittsburgh, PA (USA)
- OSTI ID:
- 5828784
- Country of Publication:
- United States
- Language:
- English
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RARE EARTH EPIDOTE FROM PEGMATITES OF THE MIDDLE URALS
Related Subjects
580100* -- Geology & Hydrology-- (-1989)
ACTINIDES
AGE ESTIMATION
COMPARATIVE EVALUATIONS
DATA
DATA FORMS
ELEMENTS
EUROPE
EXPERIMENTAL DATA
IGNEOUS ROCKS
INFORMATION
ISOLATED VALUES
ISOTOPE DATING
ISOTOPE SEPARATION
ISOTOPES
LEAD
METALS
MINERALS
NEODYMIUM ISOTOPES
NORTH AMERICA
NORTH CAROLINA
NUMERICAL DATA
OXYGEN COMPOUNDS
PEGMATITES
PHOSPHATES
PHOSPHORUS COMPOUNDS
RARE EARTH ISOTOPES
RARE EARTHS
ROCKS
SAMARIUM ISOTOPES
SCANDINAVIA
SEPARATION PROCESSES
SOUTHEAST REGION
SWEDEN
TRANSITION ELEMENT COMPOUNDS
URANIUM
USA
XENOTIME
YTTRIUM COMPOUNDS
YTTRIUM PHOSPHATES