Trace elements of Paleocene Tachira coals, southwestern Venezuela: a geochemical study

The concentration and distribution of 35 elements in 78 coal samples from t he Tachira State coal fields belonging to Los Cuervos Formation (Paleocene) of western Venezuela were obtained using atomic absorption spectrometry (A AS) and inductively coupled plasma atomic emission (ICP-AES). The aim of th is work was to determine, through a multivariate statistical approach (fact or analysis), if there is a correlation between the trace element content i n coal beds and the provenance rocks at the time of peat deposition. Compar ison with world averages and geometric means for trace element concentratio ns in coal-bed samples shows that B, Ba, La, V, Mn, Zn, and Ph are depleted . However, Tachira coal samples show a perceptible enrichment in Bi, Sb, As , Cd, and Mo, and they are highly enriched in Ag and Co. Nicholl's plot sug gests that only B and Co show a distinctive organic affinity. Enriched elem ents (Ni, Ag, Cd, Mo, Co) are both statistically and genetically related, a nd we attribute their origin to a volcaniclastic Jurassic unit. Other stati stical factors (Th-V-P and Ca-Mg-Mn) reveal a different provenance, indicat ing a felsic plutonic source and a sedimentary limestone, respectively. A f ourth factor (K-Mo-Th-S) is composed mainly of clay minerals and authigenic sulfides. (C) 2001 Elsevier Science Ltd. All rights reserved.