Quantitative Analysis Of Mineral Components In Weathering Regolith By Using XRD Full Spectrum Fitting Technique

Quantitative analysis of minerals in weathering crust and soil is a hard difficult to mineralogists.In view of the traditional X-ray diffraction quantitative method existing flaw in analyzing supergene minerals(especially clay minerals),this article explores a new technology-X-ray diffraction full spectrum fitting(Rietveld)application in the field of geology.The article try to apply X ray diffraction full spectrum fitting Rietveld method quantitative analysis of mineral components in weathering crust and establish this analysis technical process,put forward the effectiveness evaluation criteria.The paper takes Longjiang granite weathering crust and Liutang volcanic rock weathering crust as typical cases to study,depicts minerals vertical variation in weathering crust.The chief results of the study as follows:(1)Full spectrum fitting Rietveld method in quantitative analysis of the complex multiphase mixture has powerful function.Compared to the traditional X-ray diffraction such as internal standard method,quantitative analysis of clay minerals in weatehring crust by Rietveld method needn't pure substance to make standard diffraction diagram,it can improve only depend on the characteristic peak for calibration,effectively solve the problem of multiphase mixture diffraction peaks overlap and solve such as crystallinity and preferred orientation factors on the influence of diffraction intensity.Therefore,Rietveld method can give accurate quantitative analysis results.(2)Established quantitative analyze minerals process in weathering crust of XRD full spectrum fitting Rietveld method.That mainly includes the weathering crust of sample preparation and XRD data acquisition,qualitative analysis,crystal structure data of mineral phases acquisition and XRD data of test samples for full spectrum fitting refinement.(3)Base on the presupposition of refinement strategy,crystal cell parameters,background function,temperature factor and single peak were refined and quantitative analyze 16 samples minerals in Longjiang granite weathering crust and Liutang volcanic rock weathering crust.Longjiang coarse grained biotite granite weathering crust,Longjiang fine grained granite weathering crust and Liutang volcanic rock weathering crust final correction factor Rwp in 5.44%-10.77%?3.02%-8.83%?3.96%-10.65%,respectively.All samples final correction factor Rwp less than 11%.The results of full spectrum fitting refinement experiment consistent with geological situation,illustrate that Rietveld method can be effectively applied in the quantitative phase analysis of geological samples.(4)The result of two profiles Longjiang granite weathering crust comparative study cases show that mineral components of coarse grain granite and fine grained granite weathering crust in vertical change trend are significantly different with same supergene environment.Kaolinite is the advantage clay mineral in the coarse grain granite weathering crust.From bottom to top in the profile,the content of kaolinite variation is 25.28%?39.92%?42.37%?46.96%?58.12%.While the advantage clay mineral in fine grain granite weathering crust is illite,from bottom to top in the profile,the content of illlite variation is 4.08%?13.79%?30.3%?30.55%.Mineral quantitative analysis results indicate that coarse grain granite easier weathering than fine grain granite in the same weathering condition.(5)The result of Liutang volcanic rock weathering crust sduty case show that the advantage clay minerals of acid volcanic rock weathering crust are mainly kaolinite and illite in subtropical environment,this two kind minerals content can reach more than 70% in completely weathering layer and laterite.