HRTEM/AEM and SEM study of fluid-rock interactions: Interaction of copper, silver, selenium, chromium, and cadmium-bearing solutions with geological materials at near surface conditions, with an emphasis on phyllosilicates

Technical Report · Sat May 01 04:00:00 EDT 1993

OSTI ID:6328654

Veblen, D R; Ilton, E S

TEM of naturally occurring Cu-rich biotites and feldspars from weathered portions of porphyry copper deposits has shown that copper is not in the structure of these minerals, is present in their weathering products such as copper-rich vermiculite layers, submicroscopic iron oxyhydroxides and native copper inclusions, and chrysocoua. Reaction of acidic solutions bearing-Cu[sup 2+], Ag[sup +], Cr[sup 6+], and Se[sup 4+], at 25C, with biotite indicates that ferrous iron in biotite can reduce Cu[sup 2+], Ag+, and Cr[sup 6+] to Cu[degrees], Ag[degrees], and Cr(III), respectively. However, Se[sup 4+] does not appear to be reduced. Copper is reduced in the interlayer region, silver is reduced in the interlayer and on the biotite surfaces, and chromium is reduced at the biotite surface. TEM shows that the reduction of copper and silver by biotite can produce native metal inclusions, whereas reduction of Cr(VI) to CR(III) did not produce any Cr-bearing precipitates. The copper and silver experiments show that iron in biotite can be a much stronger reducing agent than iron in solution. TEM and XPS of biotites reacted with CR(VI) clearly show that edges or (hkO) faces are much more reactive than the basal planes, where the edges are strongly enriched in CR(III) relative to the basal planes. In contrast, biotites reacted with Cr(IH)-bearing solutions show little fractionation between the edges and basal planes. Another important result of our XPS studies is that we demonstrated that the oxidation state of near surface iron in biotite can be quantified.

• Research Organization: Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Earth and Planetary Sciences
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-89ER14074
• OSTI ID: 6328654
• Report Number(s): DOE/ER/14074-17; ON: DE93018022
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AQUEOUS SOLUTIONS
BIOTITE
CHARGED PARTICLES
CHEMICAL REACTIONS
CHROMIUM IONS
COPPER IONS
COPPER ORES
DISPERSIONS
DOCUMENT TYPES
ELEMENTS
IONS
IRON
METALS
MICA
MINERALS
MIXTURES
ORES
PROGRESS REPORT
REDUCING AGENTS
REDUCTION
ROCK-FLUID INTERACTIONS
SELENIUM IONS
SILICATE MINERALS
SILVER IONS
SOLUTIONS
TRANSITION ELEMENTS