Statistical analysis of the concentrations of trace elements in a wide diversity of coals and its implications for understanding elemental modes of occurrence

Seventeen trace elements in 24 coals from worldwide deposits of differing ranks and sulfur contents were determined with the use of inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and flow injection (FI) ICP-MS. By examining multiple correlations between each trace element and three major elements, calcium, aluminum, and iron, we have found that thirteen trace elements (Li, Be, V, Cr, Mn, Ni, Cu, Zn, Ga, As, Se, Sr, and Ba) in the coals show significant correspondence. Elements correlating with aluminum are lithium, beryllium, vanadium, chromium, copper, gallium, and selenium; of these elements, vanadium, chromium, and copper also have a relationship with iron. Manganese, strontium and barium are correlated with calcium, while nickel, zinc, and arsenic are correlated with iron. In the geochemical and mineralogical senses, the significant correlation of a trace element with calcium reflects its common association with carbonate minerals for medium- to high-rank coals, while that with aluminum is implicative of the common association with aluminosilicate minerals and that with iron is characteristic of the association with sulfide minerals for high-sulfur coals, and with iron-bearing carbonate and clay minerals for low-sulfur coals. It is observed that most trace elements have more than one common association(s) in the 24 coals.