Geochemistry and origin of elements in some UK coals

Twenty-four UK coals ranging in rank with 4.6%-37.6% volatile matter were a nalysed for 46 major and trace elements. The samples were obtained from the UK Coal Bank and are representative of the major UK coal fields. The major element distributions are interpreted in terms of the mineralogical variat ions-quartz and kaolinite are largely responsible for the Si and Al, carbon ates for Ca and Mg and pyrite for Fe. Also exerting an influence in some sa mples are siderite, At-phosphate minerals and illite. Based on statistical relationships with the major elements, Rb, Cr, Th, Ce, Zr, Y, Ga, La, Ta, N b and V are thought to be mainly present in the clay minerals, and As, Mo, Sb, Tl, Se and Bi and Pb are probably present in pyrite. Strontium and Ba a re concentrated in a restricted number of samples related to the phosphate minerals. Germanium is the only element for which a major organic associati on can be demonstrated. Elements with an indirect association with the orga nic matter are Na, Cl, and Br in porefluids and possibly Te. The ash conten t is controlled mainly by the detrital input and the trace elements related to the ash content are therefore those elements associated with the clay m inerals. Variations with rank would appear to be mainly related to the mois ture content (porefluids). The trace elements associated with the quartz an d clay minerals are thought to be dominantly detrital in origin. The non-de trital elements, essentially those contained in pyrite, an thought to have been incorporated in the depositional environment from waters with enhanced salinities through seawater ingress, hence there are positive relationship s between S and trace element concentrations, (C) 1999 Elsevier Science B.V . All rights reserved.