Abstract:

The geochemical features of the rare earth elements of coals from the Longtan Formation in Chongqing were studied using the methods of inductively coupled plasma mass spectrometry (ICPMS), Xray fluorescence (XRF), powder Xray diffraction (XRD). The results show that REE distribution patterns of coal samples are similar with each other. The left curve is at a high degree and the right is low and the curve is like the shape of ‘V’ as a whole. The curve of light REEs is steep and heavy REEs is rather flat in the mass. The coalforming swamps were impacted by terrigenous detrital deeply. There is high content of REEs in No.5 coal seam of Nantong Coal Mine，which is approximate twice of the average value of Chinese coal. It was controlled by Hannan Oldland, Dabashan Oldland and Longmenshan Island, only a little terrigenous detrital material was from Kangdian Oldland. There is low content of REEs in No.6 coal seam of Donglin Coal Mine，which is below the average value of Chinese coal. The effect of marine water was obvious. Although the REE contents of coal samples were not impacted by alkaline tonstein, the floor of No.6 coal seam of Donglin Coal Mine was impacted by it strongly. Based on the analysis of rare earth elements content and its ratios of coal seams, the depositional environments of Longtan Formation in the research region are sea bay (or lagoon) to tidal flat and shallow sea carbonate platform.

Key words: rare earth elements, geochemistry, coal, Longtan Formation