Physics
Scientific paper
May 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005gecoa..69.2193b&link_type=abstract
Geochimica et Cosmochimica Acta, Volume 69, Issue 9, p. 2193-2204.
Physics
6
Scientific paper
The content of radiation-induced defects (RIDs) in kaolinite samples originating from lateritic soils and continental detritic sediments of the middle Amazon Basin (Brazil) is investigated using electron paramagnetic resonance. The paleodose registered by kaolinites ranges from 80 to 900 kGy. Present-day dose rates of radiation, determined from the whole-rock U and Th content, range between 4000 and 40,000 mGy/ka. In most samples, U and Th concentrations are correlated, suggesting that U has not been remobilized by lateritization. This observation is consistent with the fact that ˜80% of the total U content is incorporated in resistant minerals, such as zircon and Ti oxides. The heterogeneous distribution of U, observed by induced fission tracks mapping, makes it possible to neglect the α-radiation contribution of the U decay chains in the dose-rate calculation. The interpretation of the measured content of RIDs in kaolinite is then performed using the calculated present-day dose rate and assuming equilibrium in the radioactive decay chains. For the sedimentary samples, the amount of RIDs is broadly correlated to the dose rate and provides apparent absolute ages older than 20 Ma. The RID contents in kaolinites from the lateritic soils provide apparent ages ranging from 10 to 6 Ma. The high RID content of these lateritic kaolinites shows that their chemical, isotopic, and crystallographic properties are not representative of present-day weathering conditions. Models assuming the “dynamical equilibrium” of kaolinites with local physical-chemical conditions prevailing in lateritic soils are thus questionable. Alternatively, our findings bring strong support for the use of the isotopic composition of kaolinites to decipher continental paleo-climates.
Allard Thierry
Balan Etienne
Calas Georges
Chabaux François
Falguères Christophe
No associations
LandOfFree
Formation and evolution of lateritic profiles in the middle Amazon basin: Insights from radiation-induced defects in kaolinite does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Formation and evolution of lateritic profiles in the middle Amazon basin: Insights from radiation-induced defects in kaolinite, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Formation and evolution of lateritic profiles in the middle Amazon basin: Insights from radiation-induced defects in kaolinite will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1434679