Summary of micrographic analysis of fracture coating phases on drill cores from Pahute Mesa, Nevada Test Site. Revision 1 Page: 92 of 144
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Sample UE-20F/8668'
This sample shows red coaling layer. X-ray powder diffraction shows that the
coating layers contain hematite, quartz, illite, and small amount of K- and Na-feldspars
(Appendix 2). TEM results show the coating layer contains hematite, quartz, illite,
highly disordered Mn-rich hydroxide, and small amount of K- and Na-feldspars. A TEM
image of powder specimen shows euhedral hematite crystals (Figure 2-1). The size of
the crystals range from 20 nm to 200 nm. EDS spectra from the crystals show Fe and O
peaks, i.e., Fe-oxide (Figure 2-2). SAED pattern also indicates the Fe-oxides is hematite
(Figure 2-3). Some hematite crystals form inclusions in quartz (Figure 2-4, Figure 2-5).
A Mn-rich phase was identified. It displays fiber-like shape (Figure 2-6, Figure
2-7). SAED patterns with strong streaking along (hOl)* direction show highly disorder in
structure (Figure 2-8, Figure 2-9). The SAED patterns are indexed based on birnessite
unit cell. It is proposed that the Mn-rich phase consists of domains of birnessite, buserite,
and todorokite. The structures of these phase are similar. EDS spectrum shows that the
phase contains small amount of Ca (Figure 2-7). Results from EDS analyses show that
the average atomic ratio between Ca and Mn is 1.12:10. It is proposed that Mn is
dominated by Mn4+, and Ca is in the interlayer positions of birnessite/buserite domains
and tunnel positions of todorokite domains. Figure 2-10 is a HRTEM image showing the
two Mn-rich crystals and the boundary between them. Variation of (202) lattice fringes'
periodicity indicates stacking disorder of the structural units along (202) * direction.
Figure 2-11 and Figure 2-12 show hematite, albite, and illitic clays. SAED
patterns from the illite show streaking diffraction along c* direction (Figure 2-13, Figure14
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Summary of micrographic analysis of fracture coating phases on drill cores from Pahute Mesa, Nevada Test Site. Revision 1, report, December 1, 1998; United States. (https://digital.library.unt.edu/ark:/67531/metadc682049/m1/92/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.