Mineralogy and origin of rhizoliths on the margins of saline,alkaline Lake Bogoria,Kenya Rift Valley |
| |
Authors: | Richard Alastair Owen Richard Bernhart Owen Robin W Renaut Jennifer J Scott Brian Jones Gail M Ashley |
| |
Institution: | 1. Department of Geography, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China;2. Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada SK S7N 5E2;3. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada AB T6G 2E3;4. Department of Geological Sciences, Rutgers University, Piscataway, NJ 08854, United States |
| |
Abstract: | A wide range of rhizoliths occurs around the margins of Lake Bogoria, Kenya. These include root casts, moulds, tubules, rhizocretions, and permineralised root systems. These rhizoliths are variably composed of opaline silica, calcite, zeolites (mainly analcime), fluorite, and possibly fluorapatite, either alone or in combinations. Some rhizoliths are infilled moulds with detrital silicate grains. Most rhizoliths are in situ, showing both vertical and horizontal orientations. Reworked rhizoliths have been concentrated locally to form dense rhizolites.Hot-spring fluids, concentrated by evapotranspiration and capillary evaporation, have provided most of the silica for the permineralisation of the plant tissues. Precipitation involved the growth of silica nanospheres and microspheres that coalesced into homogeneous masses. Calcite rhizoliths formed following evaporative concentration, evapotranspiration, and (or) CO2 degassing of Ca-bearing runoff water that infiltrated the sediment, or by mixing of runoff with saline, alkaline groundwater. Fluorite precipitated in areas where mixing of hot-spring and meteoric waters occurred, or possibly where hot-spring fluids came into contact with pre-existing calcite. Zeolitic rhizoliths formed during a prolonged period of aridity, when capillary rise and evaporative pumping brought saline, alkaline waters into contact with detrital silicate minerals around roots. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|