Lead isotope ratios in Spanish coals of different characteristics and origin

Lead isotope ratios in coals of different rank from several Spanish basins were estimated and related with their characteristics. The isotope 206Pb/207Pb ratio values of the coals studied range between 1.13 and 1.21, with the exception of some coal samples from the Cretaceous which are more radiogenic. Coals were classified into groups according to their lead isotope ratios. These in turn were related to the isotope ratios of the minerals galena, pyrite, chalcopyrite, and carbonates. Some of the low-rank coals, in which lead might be expected to be associated with the organic matter, were not found to be related with the isotope ratios of minerals. The isotope ratios of the individual densimetric fractions separated from a bituminous coal are different to those of the raw coal. The differences between these isotope ratios may not only be due to the diverse origin of lead in different coals, but also with the possible presence of several lead species incorporated from various sources in a particular coal. The results of this work represent an important contribution to the lead isotope ratio database essential for the accurate interpretation of data regarding pollution sources.