Rapid in-situ assaying of deep-sea sediments by portable X-ray fluorescence spectrometry and its applicability assessment

The pelagic clay, diatom ooze, ferromanganese nodules and crusts covering a large area of the abyssal plains are the common types of deep-sea sediments.It is very important to detect the composition of these sediments timely and accurately for improving the efficiency and cognitive ability of marine geological survey.Based on the assay of 60 samples collected from Philippine Sea by portable X-ray fluorescence spectrometry (pXRF), combined with laboratory test results, three key parameters of stability, accuracy and correlation of 24 elements detected, and its applicability of rapid detecting of deep-sea sediments to marine geological survey was discussed.Through comprehensive comparative study, it is found that nine elements, Ca, Cu, Fe, K, P, Pb, Sr, Zn and Zr, have good stability, accuracy and correlation, and can be directly used in qualitative and even quantitative research.The three index parameters of Al, Ba, Mn, Mo, Ni, Rb, Si, Ti, Th and V are slightly lower, which can be used for qualitative research and trend analysis.The elements of Bi, Cs, Mg, Sb and Sc are not recommended to use because of their poorly testing results.The measures beneficial to acquire high precision test data include adequate and uniform sampling volume, grinding and screening after drying to a constant of wet samples, adequate compaction and flattening during packaging, increasing test time, selecting appropriate reference materials for calibration and inspection, and increasing test times for key and abnormal samples.With the increase of the type and number of deep sea samples in the future, the pXRF method will be conducive to the establishment of more accurate test methods, so as to quickly reveal the composition characteristics of samples in the field and delineate mineralization anomalies etc.In this way, it can be used as a reference for the decision-making and deployment of key offshore projects.