Hydrous iron oxide minerals with short range order deposited in a spring/stream system, Tongariro National Park, New Zealand

摘要: An iron-rich deposit occurs on the bed of Waiuku Stream and one its tributaries, Mt Ruapehu, New Zealand. The upper limit is a spring which vents in tributary. Isotope ratios, 18O/16O, D/H, 13C/12C, indicate that water largely meteoric origin, from catchment at higher altitude, dissolved carbon dioxide has volcanic source. Dissolved solids appear to be derived acid attack andesite. Ferrous iron (30 g m-3) oxidized reaching surface, rate can accounted for abiotically, forming ochrous deposit. major components are Fe (40-50%), Si (5-10%), H2O(+) (11-13%), H2O(-) (14-23%), surface areas samples lie range 120-240 m2 g-I. Electron micrographs show globular aggregates indistinct, approximately spherical, particles with diameters about 5-10 nm. This information, together X-ray diffractograms, i.r. differential thermal analysis patterns hydrous oxide (more correctly, oxyhydroxide) short order. Most have characteristics close those material presently known as protoferrihydrite, though closer ferrihydrite. readily adsorbs silica phosphate stream water.