Geochemistry of major, trace and rare earth elements in coals from the Tazareh mine, eastern Alborz coalfield, NE Iran

The Tazareh mine in the eastern Alborz coalfield is one of the most important coal-producing areas in Iran and contains medium volatile (19.1–31.5%), low sulfur (0.015–0.491%) and variable ash yield (3–31.5%) bituminous coal. In this research, a total of 21 samples were collected from the Tazareh coal layers, footwall and hanging wall. The concentrations of rare earth elements (REEs) and other elements were determined by inductively coupled-plasma mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). Additionally, traditional features of coal and host rocks were studied by X-ray diffraction (XRD) and petrographic methods. The concentration coefficient (CC) of Tazareh coal samples show that Sc (CC = 2.71), Be (CC = 2.68) and Ni (CC = 2.30) are slightly enriched, Li, Cr, Pb, Sb, V, Cs, As, Co, Cu, Nb, Y, Rb, Tl, REE, Zr, Zn, Ta and Th (0.5 < CC < 2) are normal, and concentrations of remaining trace elements are lower than the average world hard coals. The NASC-normalized REEs pattern and (La/Yb)n, (La/Sm)n, (Gd/Yb)n, and (La/Lu)n ratios in the Tazareh coal confirm that the LREEs are enriched relative to HREEs, and comparatively, the degree of LREE enrichment of coal is lower than that of coal-bearing shale and argillaceous shale. Coal-bearing strata were deposited under oxic conditions in a warm-humid climate. The average content of REE + Y in Tazareh coal (58 ppm) is lower than world coals (83 ppm), while Sc is enriched.