%0 Journal Article
%T PATRONES E ¨ªNDICES DE METEORIZACI¨®N QU¨ªMICA DE LOS DEP¨®SITOS DE VERTIENTE Y ROCAS FUENTES EN EL VALLE DE ABURR¨¢
%A ARISTIZ¨¢BAL
%A EDIER
%A ROSER
%A BARRY
%A YOKOTA
%A SHUICHIRO
%J Bolet¨ªn de Ciencias de la Tierra
%D 2009
%I Universidad Nacional de Colombia
%X tropical chemical weathering of the aburr¨¢ hillslope deposits and their respective bedrock were examined using x-ray fluorescence and x-ray diffraction analyses to document and quantify their chemical weathering profiles, compositions, and mineralogical properties. the chemical index of alteration (cia), loss on ignition (loi), and the mobiles index (imob) were used to quantify the degree of weathering of hillslope deposits and bedrock source. weathering patr¨®nds were analyzed using a-cn-k and a-cnk-fm diagrams. the materials mantling the slopes in the aburr¨¢ valley record an intense weathering history. chemical weathering is characterized by increased development of clay minerals (kaolinite, halloysite) and iron and aluminum sesquioxides. lateritization characterizes the final stage of the weathering profiles. concentrations of cao, na2o, k2o decrease markedly in the weathering products compared to the fresh bedrock source, whereas concentrations of al2o3, fe2o3, and mgo increase significantly. cia ratios of matrix slope deposits derived from all four sources near 100, whereas those of boulder slope deposits and saprolites are lower, and intermediate to fresh rock values. different a-cn-k weathering paths are evident for each lithotype validating the correlation established between the hillslope deposits and their various parents. chemical weathering indices in some samples are strongly influenced by the presence of sesquioxides, as reflected by high loi, anomalously low cia, and varying enrichment patr¨®nds on the a-cnk-fm diagrams. the overall results suggest that tropical conditions have dominated for a long time in the aburr¨¢ valley, leading to uniformly high weathering indices in matrix slope deposits irrespective of parent materials. prolonged warm and humid conditions could thus be responsible for the weathering and mobilization of extensive old hillslope deposits during the quaternary.
%K geochemistry
%K tropical weathering
%K weathering indices
%K hillslope deposits
%K aburra valley
%K colombia..
%U http://www.scielo.org.co/scielo.php?script=sci_abstract&pid=S0120-36302009000100003&lng=en&nrm=iso&tlng=en