Optimization of Itrax Core Scanner Measurement Conditions for Sediments from Submarine Mud Volcanoes

Abstract

XRF scanners allow fast, high-resolution delivery of geochemical and physical property data from sediment cores. However, lack of standardized protocols for measuring parameter settings can lead to results of inferior quality to the instrument's real potential, particularly regarding light elements. In this study, a sediment core from a mud volcano in the Alboran Sea (off SE Spain) with very heterogeneous sedimentological character was analyzed using an Itrax™ Core Scanner (ITRAX). This study assesses some of the factors that influence measurements: type of anode used, X-ray exposure time, and effects resulting from the sample's exposure to room temperature during analysis as well as those caused by refrigerated storage. Quality and accuracy of the ITRAX data was evaluated by comparison with quantitative measurements obtained by conventional XRF and ICP-OES on discrete samples. The results obtained suggest 20 s is an optimal exposure time as this gives good quality results for the majority of elements analyzed, including light elements and trace elements (e.g. Al (1.9-6.6 %), Cr (84-161 µg g ). Additionally, this analysis time is not significantly detrimental to core condition. The ITRAX capacity to identify diagenetic and authigenic processes in this type of geochemical environment is also demonstrated.

Choosing optimal exposure times for XRF core‐scanning: Suggestions based on the analysis of geological reference materials

“…As demonstrated by previous studies [ Cuven et al ., ; Rodríguez‐Germade et al ., ], the scanning counts of all elements are linearly proportional to increased exposure time (Figure and supporting information Figures S1–S6). Consequently, when the exposure time was increased from 1 s to 100 s, the scanning counts of each measured element increased by two orders of magnitude for both X‐ray tubes.…”

“…[] used lacustrine sediments, while Rodríguez‐Germade et al . [] used marine sediments), the chemical differences between each reference material roughly cover most elements and concentration ranges that may be encountered in XRF‐scanning studies. Therefore, the testing results obtained from these samples can be applied to a wide range of future applications.…”

“…However, the exposure time, which represents the time period of each measured point exposed to X‐rays during scanning, is a vital parameter that directly affects the scanning counts. Theoretically, the longer the exposure time, the higher the scanning counts, which reduces relative uncertainties [ Jarvis et al ., ; Rodríguez‐Germade et al ., ]. Typically exposure times reported in the literature are set within the range of 10–30 s [e.g., Koutsodendris et al ., ; Löwemark et al ., ], although they can be set from 1 s [e.g., Guyard et al ., ] up to 100 s [e.g., Croudace et al ., ].…”

“…Unlike other technical issues that have been thoroughly discussed by previous studies, such as calibration [e.g., Böning et al ., ; Weltje and Tjallingii , ; Weltje et al ., ; Wilhelms‐Dick et al ., ] and the influences of physical and organic properties of the cores [e.g., Chawchai et al ., ; Hennekam and de Lange , ; Jarvis et al ., ; Löwemark et al ., ; MacLachlan et al ., ; Tjallingii et al ., ], only a few studies have reported the influence of exposure time [ Cuven et al ., ; Jarvis et al ., ; Rodríguez‐Germade et al ., ]. However, these exposure time‐related studies mainly focused on the reproducibility of XRF‐scanning data derived from marine or lacustrine sediments, and even fewer studies touched upon the accuracy of XRF‐scanning counts under different exposure times [ Rodríguez‐Germade et al ., ]. Furthermore, sediment heterogeneity, water content and grain size changes of the cores used for discussing the influences of exposure time [ Cuven et al ., ; Jarvis et al ., ; Rodríguez‐Germade et al ., ] may also affect or even overestimate the results of reproducibility and accuracy tests.…”

“…However, these exposure time‐related studies mainly focused on the reproducibility of XRF‐scanning data derived from marine or lacustrine sediments, and even fewer studies touched upon the accuracy of XRF‐scanning counts under different exposure times [ Rodríguez‐Germade et al ., ]. Furthermore, sediment heterogeneity, water content and grain size changes of the cores used for discussing the influences of exposure time [ Cuven et al ., ; Jarvis et al ., ; Rodríguez‐Germade et al ., ] may also affect or even overestimate the results of reproducibility and accuracy tests.…”