2021 年 116 巻 3 号 p. 140-158
Quantitative and semi–quantitative procedures using a portable energy dispersive X–ray fluorescence spectrometer (portable XRF) were applied to geochemical studies in fault rocks, lake sediments, and soils, including paleotsunami deposits. The results obtained are as follows:
1) Correlation coefficients (r2; measured values by portable XRF versus reported values) for working curves of major elements obtained using powdered reference standard materials were 0.70–0.99 with p < 0.01, except for Mg, and r2 values for the trace elements were 0.72–0.99 with p < 0.05, except for Cl, Ba, and U.
2) In the fault rocks from Central Japan (e.g., Shiraki–Nyu fault, Atera faults; powdered and nonpowdered rock fragment samples), measured values of K, Ca, Ti, Mn, Fe, Rb, Sr, Zr, and Th contents obtained using portable XRF are consistent with the reported values (r2 = 0.47–0.90, with p < 0.01). Clear Fe and Mn enrichments and K and Rb depletions were observed within the gouges of the Shiraki–Nyu fault from Central Japan.
3) The depth profiles of chemical components in lake sediments (powdered) from the Noto Peninsula in Central Japan measured using portable XRF methods were similar to those measured using the stationary–type XRF (r2 = 0.61 in Ti and r2 = 0.40 in Zr contents, with p < 0.05).
4) For paleotsunami deposits on the Pacific coast of northeast Japan, the chemical components and titanium–normalized values (Si/Ti, Ca/Ti, Sr/Ti, and As/Ti) in powdered samples measured using portable XRF correlated well with those in a previous study measured using stationary–type XRF (r2 = 0.84–0.98, with p < 0.01). Cluster analyses of geochemical data conducted using portable XRF were useful to characterize event deposits on the north Sendai Plain.
In each kind of sample, the element concentration values (SiO2, TiO2, Fe2O3, MnO, CaO, K2O, S, V, Cr, Cu, Zn, As, Rb, Sr, Zr, Pb, and Th) obtained via quantitative analyses using portable XRF were consistent with the reported values obtained via other methods, such as stationary–type XRF and inductively coupled plasma–mass spectrometry.