Chemistry and microstructures of clay particles in smectite-rich shelf sediments, South Shetland Islands, Antarctica

The clay mineralogy of a Holocene sediment core from the shelf of Livingston Island, South Shetland Islands, Antarctica has been investigated by X-ray diffraction (XRD), lattice imaging, bulk chemical analysis of fine clay fractions and analytical transmission electron microscopy (ATEM). The clay minerals identified by XRD of <2 μm fraction are smectite 63%, chlorite 25% and illite 12%, with little downcore variation. Lattice imaging of clay particles has confirmed the presence of interstratified illite-smectite and interstratified chlorite-smectite. ATEM of Ca-saturated samples showed that the smectitic clay particles are rich in K, Fe and Mg. K in the smectitic particles is mostly present as a fixed cation in the interlayer, confirming the presence of interstratified illite. A comparison of the mineralogy of the bedrock/soils in the probable source area and the core sediment strongly supports the view that the clay minerals must have originated by glacial erosion, physical weathering and reworking of hydrothermally altered volcanic bedrock and tephra of the South Shetland Islands.