Chemical and mineralogical composition of Amazon River floodplain sediments,Brazil |
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| Affiliation: | 1. Centre for Glaciology, Wadia Institute of Himalayan Geology, 33, GMS Road, Dehra Dun 248001, Uttarakhand, India;2. Department of Geology, Hemvati Nandan Bahuguna Garhwal University (A Central University), Srinagar (Garhwal) 246174, Uttarakhand, India;1. Department of Geology, Palacký University, 17. Listopadu 12, Olomouc, Czech Republic;2. Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 250 68 Řež, Czech Republic;3. Department of Mathematical Analysis and Applications of Mathematics, Palacký University, 17. Listopadu 12, Olomouc, Czech Republic;1. Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968, USA;2. Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA;3. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;4. Key Laboratory of the Earth''s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;5. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China;6. Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA |
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| Abstract: | The total and exchangeable concentration of major elements and the mineralogical composition of sediments collected along the Amazon River floodplain (várzea) were determined. Average elemental composition (wt%) decreased in the order: Si>Al>Fe>Na>Ca>K>Mg>Ti. There was some spatial variability: the concentration of Al, Na and Mg decreased downstream; the concentration of Fe, K and Ti remained constant; the Si concentration increased toward the Amazon River mouth. Mineralogically, there was a downriver increase in the concentration of quartz and kaolinite, and a concurrent decrease in the concentration of Na- and Ca-plagioclases. On the other hand smectite-vermiculite clay minerals increased and the mica (illite) concentration remained constant. A mass balance indicated that, except for illite, downriver changes in the other minerals were not caused solely by mixing of Amazon River water with water from the major tributaries, which have a distinctly different composition. Therefore, the mass balance indicated that plagioclases and smectite-vermiculite had been lost in the várzea, while kaolinite was formed there. |
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