ODP 1143 上的 K/Al 比值、Hf 同位素和粘土矿物含量

We collected splits from 1886 samples at 10 cm intervals for K and Al measurement. These samples were retrieved from ODP Site 1143, characterized by a core sediment composed of homogeneous hemipelagic fine-grained terrigenous materials and biogenic nannofossil carbonate ooze. Among these samples, 37 were earmarked for Hf isotope analysis, and 184 were allocated for clay mineral analysis. We determined the age of each sample through interpolation, utilizing an astronomically calibrated timescale from the same hole(Tian et al., 2002). All samples were dried at 60 ℃ in an oven and ~4 g samples were used and crushed into powder <200 mesh for K and Al measurements. The concentrations of K and Al were determined by X-ray fluorescence (XRF) using an Axios advanced PW4400. All analyses were conducted under the control of standards with relative standard deviation less than 5 %. To analyze Hf isotopes, the organic matter and carbonates from the sample were individually removed using excess hydrogen peroxide (30%) and 1 M acetic acid for 8 h. Then 100 mg of the sample was dissolved in a HF–HNO3 acid mixture at 120 °C for more than 72 h on a hot plate. Once dissolved, established ion exchange procedures were employed. The Hf isotopic compositions were determined using a Neptune plus (Thermo Finnigan) multicollector inductively-coupled plasma mass spectrometry (MC-ICP-MS). Clay minerals were identified by X-ray diffraction (XRD) on oriented mounts of decalcified clay-sized particles (<2 μm). The deflocculation of clays was performed by successive washing with distilled water after decarbonation with 1 M acetic acid. XRD spectra were obtained using a Rigaku D/max-rA diffractometer with Cu-Kα radiation, a voltage of 40 kV, and an intensity of 25 mA. Samples were scanned with the goniometer from 3° to 36° 2θ under air-dried conditions. Identification of clay minerals was made mainly according to the position of the (001) series of basal reflections on the XRD spectra.