Some observations on the chemical composition of todorokite

Ostwald, J.

doi:10.1180/minmag.1986.050.356.25

Cited by 30 publications

(12 citation statements)

References 14 publications

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“…Ostwald (1986) summarized the results of an electron-microprobe examination of todorokite samples from both terrestrial and marine occurrences. He concluded that Ca is present in most todorokites, and where absent, Ba may take its place.…”

Section: E Compositional Variations Of the Manganese Oxidesmentioning

confidence: 99%

Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

Carlos¹,

Bish²

1990

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The Crater Flat Tuff is almost entirely below the water table in drill hole USW G-4 at Yucca Mountain, Nevada. Manganese-oxide minerals from the Crater Flat Tuff in USW G-4 were studied using optical, scanning electron microscopic, electron microprobe, and x-ray powder diffraction methods to determine their distribution, mineralogy, and chemistry. Manganese-oxide minerals coat fractures in all three members of the Crater Flat Tuff (Prow Pass, Bullfrog, and Tram), but they are most abundant in fractures in the densely welded devitrified intervals of these members. The coatings are mostly of the cryptomelane/hollandite mineral group, but the chemistry of these coatings varies considerably. Some of the chemical variations, particularly the presence of calcium, sodium, and strontium, can be explained by admixture with todorokite, seen in some X-ray powder diffraction patterns. Other chemical variations, particularly between Ba and Pb, demonstrate that considerable substitution of Pb for Ba occurs in hollandite. Manganese-oxide coatings are common in the 10-m interval that produced 75% of the water pumped from USW G-4 in a flow survey in 1983. Their presence in waterproducing zones suggests that manganese oxides may exert a significant chemical effect on groundwater beneath Yucca Mountain. In particular, the ability of the manganese oxides found at Yucca Mountain to be easily reduced suggests that they may affect the redox conditions of the groundwater and may oxidize dissolved or suspended species. Although the Mn oxides at Yucca Mountain have low cation exchange capacities, these minerals may retard the migration of some radionuclides, particularly the actinides, through scavenging and coprecipitation. I. I.\ PRODUCTIONYucca Mountain, located on the southwest margin of the Nevada Test Site (Fig. 1), is being studied as a potential repository for high-level nuclear waste. These studies are coordinated under the Yucca Mountain Project (YMP) managed by the Nevada Operations Office of the U.S. Department of Energy. Several holes have been drilled at Yucca Mountain for geologic and hydrologic studies. Drill hole USW G-4, the most recent (1982) cored hole within the proposed repository block, was continuously cored from 22 ft to 3001 ft total depth (TD). The drilling history, core lithology, and geophysical logs of the well are given in Spengler and Chornack (1984). A preliminary study of frequency and orientation of fractures in the core is included in Spengler and Chornack (1984); a more detailed analysis is being performed by the U.S. Geological Survey with the help of geologists from Fenix and Scisson.No attempt has been made in this study to quantify the relative abundances of different fracture types. Stratigraphic descriptions used in this report are from Spengler and Chornack (1984). A general stratigraphy of the Crater Flat Tuff in USW G-4 based on Spengler and Chornack (1984) is shown in Fig. 2. All the samples from the Crater Flat Tuff are indicated, and the distributions of manganese-oxide coatings an...

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Section: E Compositional Variations Of the Manganese Oxidesmentioning

confidence: 99%

Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

Carlos¹,

Bish²

1990

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“…Lower valence cations such as Mn(III), Ni(II), and Mg(II), which substitute for Mn(IV) to offset charges on the tunnel cations, appear to be concentrated into the sites at the edges of the triple chains, as in romanechite. Chemical analyses of todorokite show considerable variation in tunnel cation composition (80), and samples from ocean nodules have up to several weight percent Ni, Co, and͞or Cu (81). Because of todorokite's large zeolite-like tunnels, there has been considerable interest in recent years in producing synthetic analogues for possible use as catalysts or molecular sieves (82).…”

mentioning

confidence: 99%

Manganese oxide minerals: Crystal structures and economic and environmental significance

Post

1999

Proc. Natl. Acad. Sci. U.S.A.

1,521

1,182

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Manganese oxide minerals have been used for thousands of years-by the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean f loor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry.

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“…Naturally occurring todorokite and todorokite-like manganese oxides include some inorganic cations, such as calcium, magnesium, and sodium, although their cation content differs from one locality to another [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of manganese oxide octahedral molecular sieves containing cobalt, nickel, or magnesium, and the catalytic properties for hydration of acrylonitrile

Onda

Hara

Kajiyoshi

et al. 2007

Applied Catalysis A: General

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Some observations on the chemical composition of todorokite

Abstract: Variations in the cholesterol bile pigment and calcium salts contents of gallstones formed in gallbladder and in bile ducts with the degree of associated obstruction. Ann. Surff. 109, 161-86.

Cited by 30 publications

References 14 publications

Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

Manganese oxide minerals: Crystal structures and economic and environmental significance

Synthesis of manganese oxide octahedral molecular sieves containing cobalt, nickel, or magnesium, and the catalytic properties for hydration of acrylonitrile

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