Production Rates Of Granitic Regolith Under Different Climatic Zones

Regolith is widely distributed on the earth surface,which is produced by the complex interactions among atmosphere,hydrosphere,biosphere and lithosphere.The substance released during the formation of regolith sustain the normal function of the ecosystem and it is the main source of the component for ocean.At the same time,these processes consume atmospheric CO₂,which regulates the climate of earth in long-term scale.In addition,the parent material of soil will be produced from it,which is great of importance for the survival and development of human beings.However,the quantification of regolith production rate is an unsolved problem in the scientific community because of the formation of regolith is a complex process under the influence of multiple factors.Until the proposal of U-series disequilibrium theory and the development of measuring technique subsequently make it possible to quantitatively determine the rate of regolith production process.Until now,U-series disequilibrium has been extensively applied to the study of regolith production rate.However,some debates still exist in the application of U-series disequilibrium theory on regolith study.Among these debates,whether the weathering profile should be simulated as a whole or not is one of them.It is impossible to directly compare the regolith production rates and discuss the influence of climate and other factors on the regolith production rate because the relative study is not enough and the difference among the formation of regolith.Furthermore,by combining with the cosmogenic nuclides method,U-series disequilibrium method can be used to assess the evolution state of regolith and the evolution of regolith during long term scale.To improve the application of U-series disequilibrium in the study of regolith and the difference of regolith production rates under various climatic conditions,in situ granitic regoliths under six different climatic zones are selected as research objects to perform U-series disequilibrium study systemically in this thesis.And six regolith profiles include NMG profile in cold temperate climatic zone,CBS profile in temperate climatic zone,QHD profile in warm temperate climatic zone,JLN profile in subtropical climatic zone,GTC profile in plateau subtropical climatic zone and HN profile in tropical climatic zone.Based on the findings in this thesis,the conclusions have been drawn as follows.（1）The U-series disequilibrium can be applied in the study of granitic regolith production rate,but some limitations are existed.The reasonable division of subzones based on the distribution characteristics of geochemistry data within profile is required.（2）The regolith production rates derived U-series disequilibrium of NMG,CBS,QHD,JLN,GTC and HN profiles range from 1.42±0.03 to 5.97±3.98 m/Ma,1.38±0.08 to 79.39±21.95 m/Ma,1.17±0.02 to 1.48±0.01 m/Ma,2.21±2.05 to2.68±0.69 m/Ma,1.47±0.01 to 2.91±0.01 m/Ma and 1.27±0.03 to 42.42±24.24 m/Ma,respectively.The regolith production rates of different subzones in the same profile are both similar to and significantly different from each other,which is attributed to the difference of evolutionary conditions during they are produced.（3）The regolith production rates of CBS and HN profile are increased first,then decreased with increase of depth,which is in agreement with humped function pattern.（4）There is no apparent correlation between regolith production rates obtained in different climatic condition and climate.The regolith production rate presented in profile is produced by complex interactions among climate,tectonics,and other factors,thus,the influence of climate on regolith production rate appears insignificant in long term scale.（5）The difference between production rates derived from U-series disequilibrium and denudation rates obtained by cosmogenic nuclide in weathering profile scale imply that the evolution state of all profiles are in non-steady state.