Six sites formed from serpentinite parent material on Greenhill, Strathdon and Unst, Shetland were excavated and the soil profiles sampled and described. After removal of organic material and separation of minerals into particle size fractions, the fractions obtained were studied by X - ray Diffraction, Differential Thermal Analysis and elemental analysis employing Atomic Absorption Spectrometry, using a dissolution procedure especially developed for conditions occuring here. Further investigations were performed using IR spectrometry and chemical dissolution techniques. Weathering tended towards three distinct types, these being (i) podzolization, characterized by bleached upper horizons due to leaching of Fe (III) down the profile, (2) laterization, not of tropical intensity but characterized by accumulation of hydrated iron oxides at the surface and iron rich clay minerals at depth and (3) gleying, characterized by reducing conditions virtually throughout the profile but with mottles containing Fe (III). The factors involved in the development of these profiles are discussed and possible mechanisms for weathering of serpentine are suggested. The dominant clay, minerals were smectite and vermiculite in all sites and the ratio of smectite to vermiculite increased with a decrease in particle size and with poorer drainage of the site. Two types of smectite were present, nontronite and saponite. The former occurs in freely drained sites and the latter under conditions of poor drainage. Chlorite, kaolinite and illite were also present. High levels of Chromium, Manganese, Nickel and Cobalt were found in the parent serpentinite and the clay minerals. The effect of particle size and drainage on the distribution of these elements was studied and their concentrations were lower in the clay fractions than in the parent serpentinite indicating that they are released into solution during weathering. Chromium is associated with chromite and nickel with serpentine. A method for the estimation of Chromium (III) and Chromium (VI) was developed and applied to the whole soils. Only Chromium (III) was found to occur naturally in the sites investigated.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:458281 |
| Date | January 1976 |
| Creators | Hargitt, Robert |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU432173 |
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