Basalt sample preparation

Year One Refinement of sample preparation and analytical techniques for trace element analysis in ocean island basalts using existing samples from the Galapagos. Compilation of existing geochemical data for Pinta and Marchena Islands. Training of students in analytical techniques, preparation for fieldwork. 

Another analytical procedure for sample preparation including analyte separation and enrichment is the coprecipitation of the trace elements to be determined. The co-precipitation behaviour of Ti, Mo, Sn and Sb under two different fluoride forming conditions (at < 70 °C in an ultrasonic bath and at 245 °C using a Teflon bomb) has been studied to improve the accuracy of the trace analysis of these elements in Ca-Al-Mg fluorides, by ICP-MS.14 The applicability of this analytical method (including isotope dilution technique) was demonstrated for four carbonaceous chondrites and silicate reference materials of basalt or andesite.14... 

Sample Preparation. The basalt was crushed and sieved, and the -120 + 230 mesh fraction was used. The grains were ultrasoni-cally washed in deionized water to remove very fine adhering particles. If these particles are not removed, they will preferentially dissolve under hydrothermal conditions, resulting in abnormally high rates of mineral-fluid reactions (10). Examination of samples of the basalt on a scanning electron microscope assured that all fines had been removed. Nitrogen B.E.T. specific surface area of the washed basalt was 2.7 m2/g. 

Standards used for comparators are either well documented materials (U.S.G.S. BCR-1 Basalt, NBS Orchard Leaves, NBS Bovine Liver, etc.) or are prepared in the laboratory by pipetting known quantities of elements onto high purity cellulose material. Standards are weighed into polycarbonate and packaged for irradiation in the same manner as the samples. 

Chemical analyses by INAA were conducted at the Archaeometry Laboratory at the Missouri University Research Reactor Center (MURR). Aliquots of sample were oven-dried at 100 °C for 24 h. Amounts of approximately 150 mg were weighed into small polyvials used for short irradiations. At the same time, 200 mg of each sample was weighed into high-purity quartz vials used for long irradiations. Along with the majolica samples, reference standards of SRM-I633a (coal fly ash) and SRM-688 (basalt rock) were similarly prepared, as well as quality control samples of SRM-278 (obsidian rock) and Ohio Red Clay (standards treated as unknowns). 

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