Natural Gamma Radiation-derived K, U and Th contents of marine sediments obtained during IODP Expeditions 359, 360, 361, 362 and 363 with DV JOIDES Resolution

During International Ocean Discovery Program (IODP) expeditions, shipboard-generated data provide the first insights into the cored sequences. The natural gamma radiation (NGR) of the recovered material, for example, is routinely measured on the ocean drilling research vessel DV JOIDES Resolution. At present, only total NGR counts are readily available as shipboard data, although full NGR spectra (counts as a function of gamma-ray energy level) are produced and archived. These spectra contain unexploited information, as one can estimate the sedimentary contents of potassium (K), thorium (Th), and uranium (U) from the characteristic gamma-ray energies of isotopes in the 40K, 232Th, and 238U radioactive decay series. Dunlea et al. [2013] quantified K, Th and U contents in sediment from the South Pacific Gyre by integrating counts over specific energy levels of the NGR spectrum. However, the algorithm used in their study is unavailable to the wider scientific community due to commercial proprietary reasons. Here, we present a new MATLAB algorithm for the quantification of NGR spectra that is transparent and accessible to future NGR users. We demonstrate the algorithm’s performance by comparing its results to shore-based inductively coupled plasma-mass spectrometry (ICP-MS), inductively coupled plasma-emission spectrometry (ICP-ES), and quantitative wavelength-dispersive X-ray fluorescence (XRF) analyses. Samples for these comparisons come from eleven sites (U1341, U1343, U1366, U1367, U1368, U1369, U1414, U1428, U1429, U1430, U1463) cored in two oceans during five expeditions. In short, our algorithm rapidly produces detailed high-quality information on sediment properties during IODP expeditions at no extra cost. Data for IODP Expeditions 317, 318, 320-324, 327, 329, 330, 334, 336, 339-342, 344-346, 349-356 can be found at http://dx.doi.org/10.1594/IEDA/100668. The Vocatio Foundation provided funding through a scholarship to David De Vleeschouwer, laureate in the 2016 promotion. This work also benefited from funding through European Research Council (ERC) Consolidator grant “EARTHSEQUENCING” (grant agreement 617462), awarded to Heiko Pälike.

在国际海洋发现计划（IODP）的远征中，船舶产生的数据为对岩芯序列的首次洞察提供了基础。例如，所回收材料的自然伽马辐射（NGR）通常在海洋钻探研究船DV JOIDES Resolution上被常规测量。目前，作为船载数据，仅能方便地获取总NGR计数，尽管完整的NGR光谱（计数作为伽马射线能级的函数）被生成并归档。这些光谱蕴含着未被充分利用的信息，因为我们可以从40K、232Th和238U放射性衰变系列同位素的典型伽马射线能量中估算出钾（K）、钍（Th）和铀（U）的沉积含量。Dunlea等人[2013]通过整合NGR光谱的特定能级计数来量化南太平洋副热带环流中的沉积物中的K、Th和U含量。然而，由于商业专有原因，他们的研究中使用的算法无法为更广泛的科学界所获取。在此，我们提出了一种新的MATLAB算法，用于NGR光谱的量化，该算法具有透明性和易于访问性，可供未来的NGR用户使用。我们通过将其结果与岸基感应耦合等离子体质谱（ICP-MS）、感应耦合等离子体发射光谱（ICP-ES）和定量波长色散X射线荧光（XRF）分析进行比较，来展示该算法的性能。这些比较的样品来自五次远征期间在两大洋中钻取的十一个地点（U1341、U1343、U1366、U1367、U1368、U1369、U1414、U1428、U1429、U1430、U1463）。简言之，我们的算法能够以不额外增加成本的方式，迅速生成关于IODP远征期间沉积物特性的详细高质量信息。关于IODP远征317、318、320-324、327、329、330、334、336、339-342、344-346、349-356的数据，可以在http://dx.doi.org/10.1594/IEDA/100668上找到。Vocatio基金会通过为2016年晋升奖获得者David De Vleeschouwer提供的奖学金提供了资金支持。这项工作还受益于欧洲研究委员会（ERC）的 Consolidator grant “EARTHSEQUENCING”（协议号617462）的资助，该资助由Heiko Pälike获得。