LATERITE FORMATION PROCESS IN SOUTHERN CHINA AND ITS RARE EARTH ELEMENT (REE) GEOCHEEMISTRY
Chemical index of alteration (CIA) for different laterites released that lateritesderived from basalt, Quaternary red clay and gneiss hold the highest CIA values,followed by granite laterites, then limestone and sandstone; other parameters ratio exposed the results which agreed well with that ofCIA; Normalized transitions for major element components were carried out to removethe false phenomena of enrichment or loss of inert components from which threestages for laterization process can be inferred, that is, leaching stage of CaO followedby leaching of and primary desilicification with Al-enrichment, thenthe stage of desilicification and Fe and Al-enrichment. Total REE contents in laterites were much higher than that in their basal rocks, andgneiss, limestone and granite laterites possessed the highest contents of total REE butlowest in sediments rich in quartz, t tests show no obviously REE content vahanceindifferent laterite horizons; Soluble REE richened apparently in the lower horizons inlaterite profiles, varied a lot with their derived basal rocks and extremely obviouslyexponential relation can be observed between total REE and soluble REE also extremelyobviously positive relations can exist for soluble REE with CIA values and claycontents while extremely obviously negative relations with organic matter, pH values and milos, which means soluble REE contents can be an effective indicator forlaterization strength. Total REE contents showed extremely apparent negative relationswith ratios and positive with ratio which reflectedthe reliance on parent rocks. After being normalized transition, laterite REE can be seenleached in the early laterization stage while enriched in the later stage. The mainchemical forms of REE in laterites were mainly crystal phases which inherited fromparent rocks, while other forms mainly related closely with laterization process.
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NSTL
万方数据
维普
