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Characterization of Mineral Forms in Andepts from Chile
Author(s) -
Espinoza W.,
Rust R. H.,
Adams R. S.
Publication year - 1975
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1975.03615995003900030047x
Subject(s) - allophane , amorphous solid , electron microprobe , mineralogy , organic matter , clay minerals , differential thermal analysis , scanning electron microscope , soil water , analytical chemistry (journal) , infrared spectroscopy , materials science , chemistry , geology , diffraction , crystallography , environmental chemistry , organic chemistry , composite material , physics , optics , soil science
The mineralogy of two undisturbed volcanic soils from Chile (Typic Dystrandepts) and of the sand and clay‐size particles of the soil residues was studied by using ultrasonic, scanning electron microscope, X‐ray diffraction, transmission electron microscope, infrared spectroscopy, differential thermal analysis, and electron microprobe techniques. The effects of removal of organic matter, free iron and aluminum oxides, and amorphous alumino‐silicates was evaluated in the X‐ray, DTA, and IR analyses. The soils are characterized by an amorphous inorganic matrix in a flocculated state with a sponge type structure. This matrix presents a high specific surface (225 m 2 /g), CEC of about 45 meq/100g at pH 7.0, low base saturation (< 20%) and bulk density of 0.9 to 1.1 (g/cm 3 ) and SiO 2 /Al 2 O 3 molar ratio of 2.0 to 4.0. Organic matter appeared in some well preserved structures, partially due to silica accumulation. The principal primary minerals are fresh volcanic glass and K‐feldspars and the principal secondary mineral is allophane or an amorphous analog. The removal of organic matter, free iron and aluminum oxides and amorphous alumino‐silicates did not alter the DTA, X‐ray and IR patterns.