Rare earth element geochemistry and fractionation in Jurassic coal from Dongsheng-Shenmu area, Ordos Basin

Rare earth element (REE) in the Jurassic coal and several other related samples from Dongsheng-Shenmu area, Ordos Basin were determined to obtain information on their concentration and distribution, as well as to evaluate the modification and mobility of REE during deposition and weathering processes. The total rare earth element (Sigma REE) concentrations of coals samples vary from 3.13 to 287.95 mu g/g. The chondrite-normalized REE patterns of the coal samples are characterized by distinct enrichments of the LREE (light rare earth element, La-Eu), and flat distribution of HREE (heavy rare earth element, Gd-Lu), with negative Eu anomalies (Eu/Eu* = 0.56-0.80, and 0.71 on average). The coal and shale samples have similar REE distribution patterns, indicating the highly tight clustering of the two, and reflecting a similar source of shale and coal mineral matter. However, REE in coal and shale behave slightly differently owe to the difference in microenvironment between them, and some coals may have HREE enrichment relative to the shale due to preferentially addition or retention of HREE. In addition, HREE probably have relatively higher mobility than LREE during weathering process, resulting in the mobility and fractionation of REE. (C) 2014 Elsevier Ltd. All rights reserved.