Geochemistry of sediment core GeoB7920-2

The X-ray fluorescence (XRF) core scanner provides bulk-sediment chemistry data measured nondestructively at the split core sediment surface. Although this method is widely accepted, there is little known about the effects of physical properties such as density and water content on XRF core scanner data. Comparison of XRF scanner measurements from the sediment surface and dry powder samples of sediment core GeoB7920 indicates strongly reduced element intensities for the lighter elements Al and Si. We relate the lower element intensities of the measurements taken at the sediment surface to the amount of water in the sample volume analyzed by the XRF core scanner. The heavier elements K, Ca, Ti, and Fe remain relatively unaffected by the variation of any physical property within sediment core GeoB7920. Additionally, we successfully use the elemental intensity of Cl as a proxy for the seawater content in the sample volume analyzed by the XRF core scanner. This enables the establishment of a correction function for the elements Al and Si that corrects for the radiation absorption of the water content in sediment core GeoB7920 off Cape Blanc, NW Africa.

X射线荧光（X-ray fluorescence, XRF）岩芯扫描仪可在劈开的岩芯沉积物表面无损获取沉积物整体化学组成数据。尽管该方法已被广泛认可，但目前学界对密度、含水量等物理性质对XRF岩芯扫描仪测量结果的影响仍知之甚少。通过对比GeoB7920岩芯沉积物表面的XRF扫描测量结果与沉积物干粉样品的测量数据，我们发现轻元素铝（Al）、硅（Si）的强度在沉积物表面测量时显著降低。我们将沉积物表面测量的元素强度偏低现象，归因于XRF岩芯扫描仪分析的样品体积内的含水量。较重元素钾（K）、钙（Ca）、钛（Ti）和铁（Fe）则基本不受GeoB7920岩芯内任意物理性质变化的影响。此外，我们成功将氯（Cl）的元素强度用作XRF岩芯扫描仪分析的样品体积内海水含量的代用指标。这一发现为建立铝（Al）和硅（Si）的校正函数提供了可能，该函数可校正非洲西北部布兰克角外海GeoB7920岩芯中水分对辐射吸收带来的影响。