The laser ablation technique, coupled with the use of quadrupole ICPMS equipment, proved a powerful tool for determination of trace elements in minerals. At the University of S?o Paulo, the technique was implemented f...The laser ablation technique, coupled with the use of quadrupole ICPMS equipment, proved a powerful tool for determination of trace elements in minerals. At the University of S?o Paulo, the technique was implemented for the study of minerals such as olivines, pyroxenes and biotites. The main problem to be tackled is the availability of proper multi-element reference materials usually prepared synthetically as glasses with various compositions by NIST and fused rock glasses by the Max Planck Institute (MPI) and USGS (basalts, andesite, quartz diorite, komatiites). The best tested ones are the NIST glasses, with good homogeneity and reliable compositional data for over 40 elements. Results are here presented that test additional RM’s. NIST 612 and 610 were used for calibration purposes. The best results were obtained for rock glasses USGS basalts BHVO-2G, BIR- 1G and BCR-2G (better homogeneity and recommended values). Our contribution tests especially the MPI komatiites glasses GOR-128 and GOR-132G, basalts KL-2G and ML-3BG, andesite StHs-6/ 80G and quartz diorite T-1G, discussing homogeneity issues and providing new data. There is a need for additional preparation of reliable reference materials.展开更多
The Patiho Formation sandstones, which crop out in Aregud neighborhood in Eastern Paraguay and show columnar joints near the contact zone with a nephelinite dyke, have as their main characteristics the high pro- porti...The Patiho Formation sandstones, which crop out in Aregud neighborhood in Eastern Paraguay and show columnar joints near the contact zone with a nephelinite dyke, have as their main characteristics the high pro- portion of syntaxial quartz overgrowth and a porosity originated from different processes, initially by dissolu- tion and later by partial filling and fracturing. Features like the presence of floating grains in the syntaxial cement, the transitional interpenetrative contact between the silica-rich cement and grains as well as the intense fracture porosity are strong indications that the cement has been formed by dissolution and reprecipita- tion of quartz from the framework under the effect of thermal expansion followed by rapid contraction. The increase of the silica-rich cement towards the dyke in association with the orthogonal disposition of the columns relative to dyke walls are indicative that the igneous body may represent the main heat source for the interstitial aqueous solutions previously existing in the sediments. At macroscopic scale, the increasing of inter- nal tensions in the sandstones is responsible for the nucleation of polygons, leading to the individualization of prisms, which are interconnected by a system of joints, formed firstly on isotherm surfaces of low tem- perature and later on successive adjacent planes towards the dyke heat source.展开更多
文摘The laser ablation technique, coupled with the use of quadrupole ICPMS equipment, proved a powerful tool for determination of trace elements in minerals. At the University of S?o Paulo, the technique was implemented for the study of minerals such as olivines, pyroxenes and biotites. The main problem to be tackled is the availability of proper multi-element reference materials usually prepared synthetically as glasses with various compositions by NIST and fused rock glasses by the Max Planck Institute (MPI) and USGS (basalts, andesite, quartz diorite, komatiites). The best tested ones are the NIST glasses, with good homogeneity and reliable compositional data for over 40 elements. Results are here presented that test additional RM’s. NIST 612 and 610 were used for calibration purposes. The best results were obtained for rock glasses USGS basalts BHVO-2G, BIR- 1G and BCR-2G (better homogeneity and recommended values). Our contribution tests especially the MPI komatiites glasses GOR-128 and GOR-132G, basalts KL-2G and ML-3BG, andesite StHs-6/ 80G and quartz diorite T-1G, discussing homogeneity issues and providing new data. There is a need for additional preparation of reliable reference materials.
文摘The Patiho Formation sandstones, which crop out in Aregud neighborhood in Eastern Paraguay and show columnar joints near the contact zone with a nephelinite dyke, have as their main characteristics the high pro- portion of syntaxial quartz overgrowth and a porosity originated from different processes, initially by dissolu- tion and later by partial filling and fracturing. Features like the presence of floating grains in the syntaxial cement, the transitional interpenetrative contact between the silica-rich cement and grains as well as the intense fracture porosity are strong indications that the cement has been formed by dissolution and reprecipita- tion of quartz from the framework under the effect of thermal expansion followed by rapid contraction. The increase of the silica-rich cement towards the dyke in association with the orthogonal disposition of the columns relative to dyke walls are indicative that the igneous body may represent the main heat source for the interstitial aqueous solutions previously existing in the sediments. At macroscopic scale, the increasing of inter- nal tensions in the sandstones is responsible for the nucleation of polygons, leading to the individualization of prisms, which are interconnected by a system of joints, formed firstly on isotherm surfaces of low tem- perature and later on successive adjacent planes towards the dyke heat source.
