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Title: Geochemical Evidence for Rare-Earth Element Mobilization during Kaolin Diagenesis

Abstract

This study investigates how saprolization influences inherent rare-earth element (REE) source rock signatures and how depositional environment(s) and diagenetic reactions ultimately impact the REE signature within sedimentary kaolin bodies. Rare-earth element geochemistry signatures are particularly useful for tracking element sources and mobility and are, therefore, powerful tools in the investigation of clay mineral formation and diagenesis. Rare-earth element and bulk chemical compositions were determined using discrete chemical analyses and chemical imaging. Saprolitic materials show an enrichment in the light and heavy REEs, compared with the parent material, with enhanced Ce/Eu anomalies. Light REEs within sedimentary kaolins are associated with phosphate mineralogy and have experienced variable degrees of diagenetic fractionation and mobilization. Cretaceous kaolins display more light REE mobility compared with Tertiary kaolins, which show very little REE fractionation. Degrees of REE fractionation are driven primarily by differences in sedimentary kaolin physical properties and the presence of organic acids in groundwater. Unfortunately, the provenance of the Georgia kaolins could not be determined based solely on the trace-element and REE compositions because fractionations during saprolization and diagenesis mask much of the inherent provenance signatures. Lastly, implications for the REEs as an economic deposit and their beneficiation are discussed.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Indiana Univ., Bloomington, IN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1468249
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Earth and Space Chemistry
Additional Journal Information:
Journal Volume: 2; Journal Issue: 5; Journal ID: ISSN 2472-3452
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Florencite; Fractionation; Georgia; Kaolinite; Rare-Earth Element; Saprolite

Citation Formats

Cheshire, Michael C., Bish, David L., Cahill, John F., Kertesz, Vilmos, and Stack, Andrew G.. Geochemical Evidence for Rare-Earth Element Mobilization during Kaolin Diagenesis. United States: N. p., 2018. Web. doi:10.1021/acsearthspacechem.7b00124.
Cheshire, Michael C., Bish, David L., Cahill, John F., Kertesz, Vilmos, & Stack, Andrew G.. Geochemical Evidence for Rare-Earth Element Mobilization during Kaolin Diagenesis. United States. doi:10.1021/acsearthspacechem.7b00124.
Cheshire, Michael C., Bish, David L., Cahill, John F., Kertesz, Vilmos, and Stack, Andrew G.. Tue . "Geochemical Evidence for Rare-Earth Element Mobilization during Kaolin Diagenesis". United States. doi:10.1021/acsearthspacechem.7b00124.
@article{osti_1468249,
title = {Geochemical Evidence for Rare-Earth Element Mobilization during Kaolin Diagenesis},
author = {Cheshire, Michael C. and Bish, David L. and Cahill, John F. and Kertesz, Vilmos and Stack, Andrew G.},
abstractNote = {This study investigates how saprolization influences inherent rare-earth element (REE) source rock signatures and how depositional environment(s) and diagenetic reactions ultimately impact the REE signature within sedimentary kaolin bodies. Rare-earth element geochemistry signatures are particularly useful for tracking element sources and mobility and are, therefore, powerful tools in the investigation of clay mineral formation and diagenesis. Rare-earth element and bulk chemical compositions were determined using discrete chemical analyses and chemical imaging. Saprolitic materials show an enrichment in the light and heavy REEs, compared with the parent material, with enhanced Ce/Eu anomalies. Light REEs within sedimentary kaolins are associated with phosphate mineralogy and have experienced variable degrees of diagenetic fractionation and mobilization. Cretaceous kaolins display more light REE mobility compared with Tertiary kaolins, which show very little REE fractionation. Degrees of REE fractionation are driven primarily by differences in sedimentary kaolin physical properties and the presence of organic acids in groundwater. Unfortunately, the provenance of the Georgia kaolins could not be determined based solely on the trace-element and REE compositions because fractionations during saprolization and diagenesis mask much of the inherent provenance signatures. Lastly, implications for the REEs as an economic deposit and their beneficiation are discussed.},
doi = {10.1021/acsearthspacechem.7b00124},
journal = {ACS Earth and Space Chemistry},
number = 5,
volume = 2,
place = {United States},
year = {Tue Mar 06 00:00:00 EST 2018},
month = {Tue Mar 06 00:00:00 EST 2018}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on March 6, 2019
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