Inter- and intra-crystal REE variations in apatite from the Bob Ingersoll pegmatite, Black Hills, South Dakota

Journal Article · Wed Feb 01 00:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90394-3· OSTI ID:5021052

Jolliff, B L; Papike, J J; Shearer, C K ^[1]; Shimizu, N ^[2]

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1. South Dakota School of Mines and Technology, Rapid City (USA)
2. Massachusetts Institute of Technology, Cambridge (USA)

Concentrations of rare earth elements (REE) have been measured on a suite of apatite crystals from an internally zoned granitic pegmatite enriched in Li, B, Be, F, Nb, Ta, Sn and U with a Cameca IMS 3f ion microprobe using energy filtering. An apatite specimen from the Tin Mountain pegmatite, analyzed previously by isotope dilution, was used as a standard. The chondrite-normalized pattern determined with the ion microprobe closely matches the pattern determined by isotope dilution, with maxima at Sm and Dy, and minima at Nd and Er. Apatite samples from the Bob Ingersoll pegmatite show a large range of REE patterns and concentrations. In one case, apatite crystals within millimeters show differences in REE concentrations and pattern shapes, including a switch from positive to negative Eu anomalies. These effects may be coupled with non-ideal partitioning of REE in a heterogeneous mixture of melt, aqueous fluid and crystals. REE concentrations in apatite samples from the different pegmatite zones indicate a large variation in outer zones, high concentrations near the pegmatite core, and very low concentration in the core. Patterns are flat to slightly inclined (Ce/Yb: 1 to 5), and most samples have positive Eu anomalies. The magnitude of positive Eu anomalies decreases with inward position in the pegmatite, possibly indicating a progressive increase in {line integral}O{sub 2}, and a sharp increase may be indicated by systematic Ce depletion in apatite from the pegmatite core. REE-specific volatile complexes may contribute to variations, including unusual kinks, observed in REE patterns of apatite from mineral assemblages in upper parts of the pegmatite.

• DOE Contract Number: FG01-84ER13259
• OSTI ID: 5021052
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 53:2; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
APATITES
ELECTRON MICROPROBE ANALYSIS
RARE EARTHS
PEGMATITES
GEOCHEMISTRY
MINERALOGY
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
PETROGENESIS
SOUTH DAKOTA
VARIATIONS
CHEMICAL ANALYSIS
CHEMISTRY
ELEMENTS
FEDERAL REGION VIII
GRANITES
IGNEOUS ROCKS
METALS
MICROANALYSIS
MINERALS
NORTH AMERICA
PHOSPHATE MINERALS
PLUTONIC ROCKS
ROCKS
USA
580000* - Geosciences