Contents lists available at ScienceDirect Journal of Geochemical Exploration journal homepage: www.elsevier.com/locate/gexplo Geochemistry of Rare Earth Elements in Lower Gondwana Coals of the Talchir Coal Basin, India Vivek Mishra a,b, ⁎ , Sanchita Chakravarty b , Robert B. Finkelman c , Atul Kumar Varma a a Coal Geology and Organic Petrology Laboratory, Department of Applied Geology, Indian Institute of Technology (ISM), Dhanbad 826004, India b Coal Characterization Laboratory, CSIR – National Metallurgical Laboratory, Jamshedpur 831007, India c Geosciences Department, University of Texas at Dallas, Richardson, TX 75080, USA ARTICLE INFO Keywords: Indian coal Rare earth elements and yttrium Talchir coal basin Mode of occurrences ABSTRACT This study investigated the concentration, distribution, and modes of occurrences of rare earth elements in coal from the Talchir coal basin, Odisha State. This basin comprises two coal bearing Formations i.e. Barakar and Karharbari. Samples, collected from one borehole, were analyzed by X-ray difraction, X-ray fuorescence, electron microprobe and inductively coupled plasma mass spectrometry (ICP-MS). The coals are medium to high volatile, high ash and low sulphur. The Rare Earth Elements and Yttrium (REY) of the 34 coal samples varies from 29.6 ppm to 179.4 ppm with an average value of 91.0 ppm. The average value of total REY of the Barakar Formation (53.6 ppm) is considerably lower than the average value of Karharbari Formation (127.4 ppm). The average of the ratio of light to heavy rare earth elements (LREE/HREE) is also much higher in the Karharbari Formation (8.1) than in the Barakar Formation (4.4). Coals from both Formations show negative europium anomalies while only coals from the Karharbari Formation show a positive cerium anomaly. These diferences indicate diferences in depositional conditions between the coals of the two Formations within the coal basin. Through EPMA analysis, REY-bearing phosphates are found to be present in this coal in clay minerals. Monazites are found in Mg aluminosilicate matrix as dispersed minerals which may be detrital and monazite-bearing chlorite indicates that the monazites are formed by hydrothermal alteration during coalifcation. Ag, Ba and Zr are found as replacements or substitution in the REY phosphates. 1. Introduction The 17 lanthanides or rare earth elements (REEs) are valued for their unique magnetic, phosphorescent, and catalytic properties in numerous products and processes including high-strength magnets, car batteries, and catalysts as well as in defense and consumer electronics (Hower et al., 2016a; Dai et al., 2016). The major controls on the geological and cosmochemical behaviour of the REEs are their size (ionic radius), coordination number, redox potential, volatility and ionic behaviour. Geochemists divide REEs into the light rare earth (LREE i.e. from La to Sm, occasionally with Eu) and heavy rare earth (HREE i.e. from Gd to Lu). Although Y has a lower atomic weight, because of its chemical and physical similarities (ionic radius and charge is similar to Ho) it is commonly grouped with the HREE and, when included, they are referred to as REY (Bau, 1996; Seredin and Dai, 2012; Dai et al., 2016). In recent years almost 90% of the world's supply of REE comes from China (Department of Energy, 2017). This situation has resulted in countries seeking secure sources of these valuable and strategically important elements. One potential source that is attracting considerable attention is coal and the products of coal combustion (Seredin and Dai, 2012; Seredin et al., 2013; Hower et al., 2013, 2016a; Zou et al., 2014). There are many publications from the U.S., China, and Russia in- vestigating the concentration, distribution, mode of occurrence, and origin of REEs in coal (Birk and White, 1991; Seredin, 1996; Wenhui et al., 2000; Schatzel and Stewart, 2003; Wenfeng et al., 2003; Dai et al., 2006; Zheng et al., 2007; Wang et al., 2008; Sun et al., 2010; Liu et al., 2014; Wang et al., 2014; Dai et al., 2016; Hower et al., 2016b; Lin et al., 2017; Arbuzov et al., 2018). Information on the modes of oc- currence of REEs in coal can help to assess the potential extraction procedures from coal and coal combustion by-products (Finkelman, 1993; Seredin and Dai, 2012; Seredin et al., 2013; Sun et al., 2016; Dai and Finkelman, 2018; Finkelman et al., 2018). Based primarily on selective leaching behaviour Finkelman et al. https://doi.org/10.1016/j.gexplo.2019.04.006 Received 11 January 2019; Received in revised form 5 April 2019; Accepted 24 April 2019 ⁎ Corresponding author at: Coal Geology and Organic Petrology Laboratory, Department of Applied Geology, Indian Institute of Technology (ISM), Dhanbad 826004, India. E-mail address: vmishrageology@gmail.com (V. Mishra). Journal of Geochemical Exploration 204 (2019) 43–56 Available online 03 May 2019 0375-6742/ © 2019 Elsevier B.V. All rights reserved. T