Leaching Simulation Of Carbonate Weathering Mechanisms And Enrichment Instruction Of Uranium And Thorium

In the study of carbonate rock weathering crust, find that change from rock tosoi（lRock-soil interface）sudden and clear，have not continuous evolution sequence，it’s hard direct use geological section development characteristics to explorecarbonates pedogenesis and some elements enrichment mechanism.Based on this,inthis study,with experimental simulation method,direct tracer rock-soil interfaceprocess role，then reveals carbonates pedogenesis and geochemistry of U, Th.WithCO2saturated water as a leaching solution conducted a dry hot,wet hot,dry cold threeclimatic conditions simulated leaching experiments which located carbonateweathering crust Rock-soil interface rock powder layer sample,made a key researchon the leachates EC、pH and main elements analysis the enrichment mechanism of U、Th in lime soil during the formation process.Conclusions are as follows:(1)Insolubles weathered in carbonate rocks mainly begins transition from rock tosoil of Rock-soil interface,synchronized with carbonate dissolution。(2)There is a difference of carbonate dissolution intensity leaching conditions inthree performance in which dry cold condition have the strongest dissolution intensityunder wet hot condition have the weakest dissolution intensity,dry hot Betweenthem.Shows that low temperature conditions favor the dissolution ofcarbonate;Released by the dissolution of carbonate Ca, Mg etc.conducive more alongthe fluid weathering in an environment drainage is discharged.(3)Under dry hot condition,acid insoluble component where the K、Na、Si、Mg、P located has the strongest mineral weathering intensity.Most of the dissolutionability of base cations between wet hot and dry cold,showing wet hot strongerdissolution characteristics than dry cold;The Si and P in the three samples did notshow a consistent trend.In the dry hot Si and P also showed the strongest abilitydissolution,the wet hot and dry cold environment do not conducive Si, P releasecarrier of mineral decomposition and ions,this difference in the micro-environment of the leaching system may be the cause of Si and P in the wet hot and dry cold twoconditions did not show the same trend reason;Fe and Mn are weak migrationelement,in the dry cold environments where Fe leaching of weakest,under dry hotand wet hot Fe have no variation of the same trend as three specimens,Mn showing aactivity characteristic in whole,Mn leaching conditions in three specimens also haveno similar trend;In this process,Ti and Al both showed significant inertiacharacteristics。(4)In U, Th mutation enrichment process,carbonate rock-soil interface is animportant location.In the rock-soil interface reactions:to U,with the rapid dissolutionof carbonate weathering solution out and significant loss meantime due to the hugechanges while narrowing weathered residue resulted in residual volume relativeenrichment of U strongly，make U changes in the performance of high loss intensityin low background,thus a high degree of geochemical characteristics ofenrichment.Under different conditions, Th exhibit different characteristics,when Thand U were active characteristics has similar performance feature;when showing theinert characteristics，Th enrichment profiles mainly from the soluble portion of theremaining after dissolution.(5)U, Th in carbonate content and the bedrock weathering profile (or bedrockacid insoluble) content of the corresponding elements have not related changescharacteristics.The U, Th, but inversely proportional to the acid insoluble contentbedrock weathering profiles in the level of enrichment factor，in other words:thelower the content of acid insoluble carbonates,the larger the amount of carbonatedissolution of the body, with the activity of the solution to bring out the more U orTh,while the greater the degree of weathering changes in the volume is reducedresidue,therefore, the relative degree of enrichment of the residual U or Th is alsohigher.