ORCID Identifier(s)

0000-0003-3032-8106

Graduation Semester and Year

2016

Language

English

Document Type

Thesis

Degree Name

Master of Science in Earth and Environmental Science

Department

Earth and Environmental Sciences

First Advisor

Andrew Hunt

Abstract

Analysis of the mineral constituents of friable surface deposits from the Burkina Faso and Niger regions, North Africa, was undertaken by computer controlled scanning electron microscopy (CCSEM) to try and identify variations in mineralogical composition which could be used for source attribution to distinguish windblown material from different contributing source areas. A total of 16 friable surface samples were collected for CCSEM analysis. These samples were from multiple geographic locations within the Burkina Faso region. CCSEM analysis generated data on individual dust particles that included: particle size, shape, and chemical composition. This combination of the Scanning Electron Microscope (SEM) working in the Backscattered Electron Imaging (BEI) mode was used for the aforementioned particle characterization. The BEI mode of imaging of microscopic dust particles provided information on the average atomic number composition and particle morphology. The use of a Silicon Drift X-ray detector with an ultra-thin window provided all element data on individual particles. The principal goal of this project was to (1) compare and contrast surface material from laterites versus proximal soils from the Burkina Faso and Niger regions of North Africa with the intention of differentiating the material from each other at the individual particle level and (2) to establish a linear classification scheme based upon the mineral composition of North African surface sediments to permit the attribution of laterite and soil particles to specific mineral classes. The mineralogy of the individual particles from all soil samples was determined by CCSEM. CCSEM analysis provided data on thousands of particles and, as a result, significant sized data sets can be evaluated statistically. With friable soil particles it is commonly of no use in CCSEM analysis to define specific mineral particle types. Obdurate minerals such as quartz may often be identified in CCSEM data (Particles composed wholly of Si). Unfortunately, transformation processes, such as the particles being coated by Fe, alter the composition of basic mineral forms in regards to the chemical composition identified in the SEM. In order to provide a realistic classification of the particles analyzed here, a reference data set from the analysis of a North African friable surface deposits sample was used to develop a classification scheme. Homogenous groups of particles within the data set were identified with the use of assisted cluster analysis. Homogenous groups of particles were distinguished based upon the associations of constituent particle elements. A 59-class element-based classification scheme was then developed based upon the homogenous groups identified. All classes were listed in a linear sorting order which was used to classify the CCSEM data from the soil samples collected within this study. The study sample CCSEM analysis typically contained element and other data on approximately 5,100 particles per sample.

Keywords

Burkina Faso, Niger, Laterite, Soil

Disciplines

Earth Sciences | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

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