DOI: 10.5285/0502846d-3ac3-46e9-aa2c-27adbe9367fd
title: Clay mineral composition of sediments from International Ocean Discovery Program (IODP) Expedition 379 Hole U1532B, Amundsen Sea, West Antarctica (2019)

description: This data set presents contents of the clay minerals smectite, illite, chlorite and kaolinite analysed on the clay fraction (less than 2 micrometers) of Pleistocene-Holocene drift sediments recovered at Hole U1532B on the Amundsen Sea continental rise during IODP Exp379 with RV JOIDES Resolution in Jan-Mar 2019. The clay mineral contents are given in percentages both versus expedition number, site number, hole ID, core number, drill core type (H: advanced piston corer system, X: extended core barrel system; R: rotary core barrel system), section number (sect), section half (W: work; A: archive) and depth of the top and bottom of the sample within a section or core catcher (CC) in centimetres (cm) and versus depth below seafloor (CSF-A) in metres (m). The d-values (in Angstrom) and integral breadths (IB, delta 2theta) of the clay minerals smectite and illite as well as the ratios between the areas of the 5 Angstrom and 10 Angstrom peaks of illite are also given. The clay mineral data were generated and analysed by Dr Claus-Dieter Hillenbrand (British Antarctic Survey, Cambridge, United Kingdom) and Prof Werner Ehrmann (Institute of Geophysics and Geology, University of Leipzig, Germany). Users of this dataset should cite the dataset DOI and acknowledge both the data generators (C.-D. Hillenbrand and W. Ehrmann) and the International Ocean Discovery Program (IODP). The work was funded by NERC UK-IODP Moratorium Award NE/T010975/1.
description: The clay fraction (less than 2 micrometers) was separated from the bulk sediment in settling tubes, and 40 mg clay suspension was mixed with 1 ml of an internal standard (0.04 % MoS2 suspension). The samples were then mounted as texturally oriented aggregates by rapidly filtering the suspension through a membrane filter (0.20 micrometer pore width), the filter cakes were dried at 50 °C, fixed on aluminium tiles and exposed to ethylene glycol vapour at a temperature of 60 °C for at least 18 h immediately before the X-ray analyses. The measurements were conducted on a diffractometer system Rigaku New Miniflex with CoK alpha radiation (30 kV, 15 mA). First, the samples were X-rayed in the range 3 - 40 °2 theta, with a step size of 0.02 °2 theta and a measuring time of two seconds per step. Then, the range 27.5 - 30.6 °2 theta was X-rayed with a step size of 0.01 °2 theta and a measuring time of four seconds per step in order to better resolve the (002) peak of kaolinite and the (004) peak of chlorite. The X-ray diffractograms were evaluated using the interactive MacDiff software (Petschick 2010, Petschick 1996). The main clay mineral groups were identified by their basal reflections at 16.5 Angstrom (smectite, after glycolisation), 10 and 5 Angstrom (illite), 14.2, 7, 4.72 and 3.54 Angstrom (chlorite), and 7 and 3.58 Angstrom (kaolinite) after the diffractograms had been adjusted to the MoS2 peak at 6.15 Angstrom. For semi-quantitative evaluations of the clay mineral assemblages, empirically estimated weighting factors on the integrated peak areas of the individual clay mineral reflections were used (Biscaye 1964, 1965). The crystallinity of illite was determined by calculating the integral breadth (IB, delta °2 theta) of the 10 Angstrom peak. High IB values indicate poor crystallinities, whereas low values indicate good crystallinities. Furthermore, we inferred the illite composition from the 5/10 Angstrom peak area ratio. Values more than 0.4 correspond to Al-rich illites (muscovite). The ratio decreases with Mg and Fe substituting the octahedral Al. Magnesium and iron-rich illites (biotite) have values less than 0.15 (Esquevin 1969).
description: A diffractometer system Rigaku New Miniflex with CoKα radiation (30 kV, 15 mA) was used for the X-raying. The diffractograms were analysed with the interactive MacDiff (v. 4.2.5) software (Petschick 2010).
description: By preparing, analysing and evaluating samples six times, a standard deviation of c. 1% was obtained for the concentrations of smectite, chlorite and kaolinite, and of c. 1.5% for illite. The standard deviation for the 5/10 Angstrom peak area ratios is c. 0.05 and that for illite IB c. 0.02 delta °2theta.