38
2 WEATHERING AND THE SEDIMENTARY CYCLE
Fig. 2.14. Sketch illustrating the occurrence of carnotite roll-front ore bodies in fluvial channel sandstones.
The direction of front migration in this case was from right to left.
when a diagenetic front moving along a channel was stabilized by a change in the flow
or chemistry of migrating pore fluids (Raffensperger and Garvan, 1995a,b). The original source of the uranium has always been a source of debate but volcanic ashes and
tufts are often taken as the primary source, with subsequent migration and concentration by percolating acid groundwater. This close association of mineral migration and
hydrology has led to an understanding of the role of permeability barriers in determining the locus of carnotite precipitation. Thus mineralization is absent in the laterally
continuous sands of eolian and marine origin, which possess near uniform permeability. It typically occurs adjacent to permeability barriers, such as unconformities, or in
fluvial formations with sand:shale ratios of between 1 : 1 to 1 : 4 (see Section 6.3.2.2.4).
This brief review shows how weathering is a process of considerable direct economic
importance as well as being one of fundamental geological significance.
S E L E C T E D B I B L I O G R A P H Y
Hobday, D. K., and Galloway, W. E. (1998). Groundwater processes and sedimentary uranium
deposits. HydrogeoL J. 7, 127-138.
Leeder, M. R., Harris, T., and Kirkby, M. J. (1998). Sediment supply and climate change: Implications for basin stratigraphy. Basin Res. 10, 7-18.
Meyer, R. (1997). "Paleolaterites and Paleosols: Imprints of Terrestrial Processes in Sedimentary
Rocks." A. A. Balkema, Rotterdam. 151pp.
Wilson, M. J. (1999). The origin and formation of clay minerals in soils: Past, present and future
perspectives. Clay Miner. 34, 1-27.
R E F E R E N C E S
Bardossy, G. (1987). "Karst Bauxites." Elsevier, Amsterdam. 441pp.
Bohor, B. E, and Triplehorn, D. M., eds. (1993). "Tonsteins: Altered Volcanic Ash Layers in Coalbearing Sequences," Spec. Publ. No. 285. Geol. Soc. Am., Boulder, CO. 48p.
Bristow, C. M. (1968). Kaolin deposits of the United Kingdom. Int. Geol. Congr. Rep. Sess., 23rd,
Prague, vol. 15, pp. 275-288.
2 WEATHERING AND THE SEDIMENTARY CYCLE
Fig. 2.14. Sketch illustrating the occurrence of carnotite roll-front ore bodies in fluvial channel sandstones.
The direction of front migration in this case was from right to left.
when a diagenetic front moving along a channel was stabilized by a change in the flow
or chemistry of migrating pore fluids (Raffensperger and Garvan, 1995a,b). The original source of the uranium has always been a source of debate but volcanic ashes and
tufts are often taken as the primary source, with subsequent migration and concentration by percolating acid groundwater. This close association of mineral migration and
hydrology has led to an understanding of the role of permeability barriers in determining the locus of carnotite precipitation. Thus mineralization is absent in the laterally
continuous sands of eolian and marine origin, which possess near uniform permeability. It typically occurs adjacent to permeability barriers, such as unconformities, or in
fluvial formations with sand:shale ratios of between 1 : 1 to 1 : 4 (see Section 6.3.2.2.4).
This brief review shows how weathering is a process of considerable direct economic
importance as well as being one of fundamental geological significance.
S E L E C T E D B I B L I O G R A P H Y
Hobday, D. K., and Galloway, W. E. (1998). Groundwater processes and sedimentary uranium
deposits. HydrogeoL J. 7, 127-138.
Leeder, M. R., Harris, T., and Kirkby, M. J. (1998). Sediment supply and climate change: Implications for basin stratigraphy. Basin Res. 10, 7-18.
Meyer, R. (1997). "Paleolaterites and Paleosols: Imprints of Terrestrial Processes in Sedimentary
Rocks." A. A. Balkema, Rotterdam. 151pp.
Wilson, M. J. (1999). The origin and formation of clay minerals in soils: Past, present and future
perspectives. Clay Miner. 34, 1-27.
R E F E R E N C E S
Bardossy, G. (1987). "Karst Bauxites." Elsevier, Amsterdam. 441pp.
Bohor, B. E, and Triplehorn, D. M., eds. (1993). "Tonsteins: Altered Volcanic Ash Layers in Coalbearing Sequences," Spec. Publ. No. 285. Geol. Soc. Am., Boulder, CO. 48p.
Bristow, C. M. (1968). Kaolin deposits of the United Kingdom. Int. Geol. Congr. Rep. Sess., 23rd,
Prague, vol. 15, pp. 275-288.