Depth-dependent transformation of kaolinite to dickite in sandstones of the Norwegian continental shelf

摘要: Replacement of kaolinite by dickite has been observed to occur with increasing depth burial in sandstones from three different basins on the Norwegian continental shelf. In Garn Formation (Middle Jurassic) Haltenbanken, samples 1.4-2-7 km below sea floor (110°C) contain kaolinite, whereas deeper than 3.2 (130°C) mainly is present. Statfjord (Late Triassic-Early Gullfaks and Sor Fields, transformation occurs at ~3.1 (120°C) From Sto Nordmela Formations (Lower Middle Troms Area, kaolin polytypes have identified only two shallow deep samples, but results are consistent determined other areas studied. These occurrences significant because they allow temperature kaolinite/dickite be established greater confidence had possible previously. Also observation this all so far examined indicates that it may a general predictable feature kaolinbearing worldwide therefore potentially reliable paleogeothermometer. most cases, as relatively large vermicular crystals, forms more euhedral, blockier crystals. This morphological difference, together nature structural difference octahedral occupancy between dickite, suggests dissolution reprecipitation, rather then solid state.