%0 Journal Article
%T An¨¢lisis geoqu¨ªmico (elementos mayores, menores, traza, ¦Ä13C, ¦Ä18O y tierras raras) de microbialitas selectas provenientes de la Formaci¨®n San Casiano (Tri¨¢sico Medio - Superior, NE de Italia)
%A S¨¢nchez-Beristain
%A Francisco
%A L¨®pez-Esquivel Kranksith
%A Laura
%J Bolet¨ªn de la Sociedad Geol¨®gica Mexicana
%D 2011
%I Sociedad Geol¨®gica Mexicana
%X the results of the geochemical analysis of 28 major, trace and rare earth elements, as well as carbon and oxygen isotopes, are presented for 17 microbialite samples from the st. cassian formation (ne italy). these results have allowed the characterisation of the mineralogical composition of the microbialites as high-mg calcite (>4.00 % mol mg), the determination of their good state of preservation, and the detection of the influence of fine siliciclastic sedimentation during their growth. furthermore, redox conditions of the palaeoenvironment were determined with the aid of these analyses. finally, it was possible to compare the geochemical signals of the microbialites with that of skeletal components, allomicrites and cements in order to find possible metabolical relicts and/or evidence of biological activity using trace elements. two methods were used to perform these analyses: laser ablation inductively coupled plasma-mass spectrometry (la-icp-ms), and mass spectrometry to obtain carbon and oxygen isotope values. microbialitic samples show medium to high contents of silicon and aluminium. these elements reflect the sedimentation of clays during the growth of microbialites. there is no correlation between the values of mn/sr and ¦Ä18o or between ¦Ä13c and ¦Ä18o, indicating the absence of meteoric diagenesis. iron and manganese concentrations show a medium correlation with sulfur, which links the origin of these elements to early diagenetic processes. these processes can be confirmed by the high strontium content and the ¦Ä18o values. the microbialites are enriched with a vast array of minor and trace elements. some elements of unknown biological importance (rb, ti, zr, nb and th) are associated with certain major elements (r2 with si > 0. 5), confirming their terrigenous origin. other elements (zn, sb, cr, v, sn, ni and co) show no association with silicon or aluminium, yet they cannot be considered as metabolic residues due to their enrichment in non-biological phase
%K microbialites
%K carnian
%K triassic
%K st. cassian formation
%K element analysis
%K la-icp-ms.
%U http://www.scielo.org.mx/scielo.php?script=sci_abstract&pid=S1405-33222011000300003&lng=en&nrm=iso&tlng=en