Mobilization and redistribution of REEs and thorium in a syenitic lateritic profile: A mass balance study

摘要: Abstract REE-Th geochemistry and mineralogy have been studied in a lateritic profile derived from syenite at Akongo SW Cameroon. REE Th mass balance calculations for the host-rock minerals show that least 70% of LREE s 50% HREEs are contained allanite, apatite, titanite, epidote is controlled by same accessory which represent about 2 wt% unaltered syenite. These phases destroyed during first stages weathering causing most REEs to be rapidly released into soil. Comparison variation Zr, Ti, content as function apparent density different zones saprolite shows mobile element. The presence secondary thorianite (ThO2), etched surface on zircon grains, Ti cerianite support this geochemical interpretation. concentration thorium was, therefore, chosen invariant relative other elements, especially REEs, calculations. Most leached iron-rich upper horizons (loose nodular horizon, iron crust, top mottled clay horizon). Where groundwater table moves (saprolite bottom horizon), fractionated redistributed. There juxtaposition accumulation with precipitation aluminous hydrated phosphates. This study supports existence two cycles redistribution elements soil: 1. (1) dissolved ions 2. (2) individual particles part profile.