THE PHYSICAL, CHEMICAL, AND MINERAL0G1CAL PROPERTIES OF LATERITE SAMPLES FORMED IN VARIOUS ENVIRONMENTS
THE PHYSICAL, CHEMICAL, AND MINERAL0G1CAL PROPERTIES OF LATERITE SAMPLES FORMED IN VARIOUS ENVIRONMENTS
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Date
1980
Authors
IBANGA, INIOBONG JIMMY
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Abstract
IBANGA, INIOBONG JIMMY. The Physical, Chemical, and Mineralogical
Properties of Laterite Samples Formed in Various Environments. (Under
the direction of STANLEY W. BUOL).
Samples of l a t e r i t e were obtained from Australia, Bolivia, B r a z i l,
Nigeria, Thailand, and the U. S. A. The l a t e r i t e materials were found to
have a yery wide range of chemical and morphological characteristics. A
prominent feature of all samples is a high content of iron and/or aluminum,
r e l a t i v e to other constituents. The amount of free iron varies
from 4.7 to 44.6% on an oxide basis. Iron is present in the form of goet
h i t e , hematite, lepidocrocite, as poorly c r y s t a l l i n e oxide compounds, and
as unidentified coatings on other minerals. The other minerals i d e n t i f i ed
in the l a t e r i t e samples were kaolin minerals, which are common in a l l samples,
quartz, feldspars, and micas. Quartz is an i n e r t component and is
believed to be derived from the underlying acidic rocks.
The structure of l a t e r i t e as observed in thin sections and with the
scanning electron microscope is complex and displays an even greater
variety than the chemical composition. One structural extreme is the type
composed largely of p i s o l i t i c bodies more or less closely packed in a
matrix. The other extreme of structure is the vesicular type in which the
cavities are either empty, f i l l e d or partly f i l l e d with clay minerals.
In addition, data obtained indicate a strong relationship between
color and iron mineralogy. The reddish colored samples have a high content
of hematite while the yellowish samples have a high goethite content.
Also, samples with a low active iron r a t i o tend to have a reddish color
while those with a high active iron r a t i o are yellowish in color. Another
relationship detected shows that samples that have a high content of kaol
i n i t e (- 60%) are dominated by hematite while those with < 30% k a o l i n i te
are dominated by goethite.
On an inter-regional scale, there is an apparent lack of relationship
between l a t e r i t e formation and lithology. But on a smaller scale the
l i t h o l o g i c a l control of the composition and form is more evident.
Description
A thesis submitted to the Graduate Faculty of
North Carolina State University at Raleigh
in partial fulfillment of the
requirements for the Degree of
Doctor of Philosophy
DEPARTMENT OF SOIL SCIENCE
Keywords
PHYSICAL,, CHEMICAL,, MINERAL0G1CAL PROPERTIES,, LATERITE SAMPLES,, VARIOUS ENVIRONMENTS,