Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5468997 | Applied Clay Science | 2017 | 10 Pages |
Abstract
Chemical analysis and element mapping of clay-size grains using scanning and transmission electron microscopy (STEM-EDX) greatly facilitates investigations of minor minerals and the location (speciation) of minor elements in the clay fraction. STEM-EDX was used to identify minor minerals and determine the composition of grains in the clay fraction of three soils developed from marble, phyllite, mica-schist and granite in southern Brazil. Before STEM-EDX analysis the clay was treated with citrate-bicarbonate-dithionite or NaOH to remove iron oxides and kaolin respectively. Chemical formulas of clay-size grains were calculated based on EDX analyses. Minerals that were not detected by XRD in the clay fraction were identified from STEM-EDX analyses, including fluorophlogopite, baileychlore, saponite-sauconite, gorceixite and crandallite. Partly weathered (altered) particles of fluorophlogopite had reduced F, K and Mg concentrations. High Zn concentrations in phyllite and mica-schist parent rocks were associated with the presence of baileychlore in the clay. Barium occurred in K-feldspar, smectite and illite. Small amounts of Ti were allocated in octahedral layer of smectite and illite. The chemical analyses of clay size particles supplied by high resolution STEM-EDX has great potential for investigating the location of elements within minerals in the clay fraction.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
A.H. Batista, V.F. Melo, R. Gilkes,