--> ABSTRACT: A Preliminary Study of REE Distributions in Mudrocks of Permian Beacon Supergroup, Central Transantarctic Mountains: Evidence for Early Development and Preservation of LREE Enrichment, by Lawrence A. Krissek and Timothy C. Horner; #91030 (2010)

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A Preliminary Study of REE Distributions in Mudrocks of Permian Beacon Supergroup, Central Transantarctic Mountains: Evidence for Early Development and Preservation of LREE Enrichment

Lawrence A. Krissek, Timothy C. Horner

Partial REE patterns have been determined for ten Permian mudrock samples from the central Transantarctic Mountains. Depositional environments of the samples range from fluvial overbank to openwater deltaic and basinal. REE patterns have been characterized by a LREE enrichment factor (EF), defined as the NASC-normalized La/Lu ratio. The response of LREE to weathering intensity, thermal diagenesis, and compositional variability has been assessed.

Average LREE EF for the ten samples is 2.00 (±0.6), similar to published LREE EF for recent riverine and marine siliciclastics. This agreement suggests that the LREE EF of a sediment is established early in its weathering/transport history. LREE EF do not covary with either an index of chemical weathering or vitrinite reflectance, indicating that LREE are not fractionated by either bulk weathering processes or diagenesis.

As noted previously, LREE EF increases as grain size decreases and clay mineral abundance increases. Geographic variations in LREE EF, however, may also reflect a provenance control. These stratigraphic and geographic distributions of LREE EF emphasize the importance of grain size and mineralogy as controls on REE compositions, but also suggest that the early development of LREE enrichment can include a stable provenance signal.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.