Development of micro-PIXE method for geochemical analysis. Quantitative trace element analyses of minerals and single fluid inclusions by micro-PIXE

This work was performed by University of Tsukuba under contract with Japan Nuclear Cycle Development Institute. In this study, quantitative trace element analytical techniques for minerals and single fluid inclusions by micro-PIXE have been developed investigate a behavior of radioactive nuclide in rocks and chemical compositions of deep underground water that is retained in minerals as fluid inclusions. By using the developed methods, trace elements in glasses and minerals were determined with average estimated relative error of ±10%. For single fluid inclusions, elements with concentrations of 10 to 1000 ppm were measured with average estimated relative error of ±7%. For natural fluid inclusions with 30 μm radius and 20 μm depth in quartz, the total analytical errors were estimated to be ±40% relative for Ca, ±16% for Fe, ±13% for Zn, ±12% for Sr, and ±11% for Br and Rb, by considering uncertainties in microscopic measurements of inclusion depths. Detection limits of 4 to 46 ppm for elements of mass numbers 25-50 were achieved for analyses of a spherical fluid inclusion with 30-μm radius and 20-μm depth in quartz at an integrated charge of 1.0 μC. The trace element compositions of single fluid inclusions in hydrothermal quartz veins from Nagano and Nagasaki Prefecture were also determined by using the developed method. High concentration (wt.%) of Ca and Fe, and tens to thousands ppm Mn, Zn, Cu, Br, Rb, Sr, Pb, and Ge, were observed in the fluid inclusions indicating higher metal contents in hydrothermal fluid released from granite. (author)