TUFFS

Tubular membranes Tubular modules Tubular reactors Tubulates b-Tubulin Tubulin Tuffs Tufperm Tufprene... 

Tuff, a compressed volcanic material, is the primary constituent of Yucca Mountain, near Las Vegas, Nevada, the site selected by Congress in 1987 for assessment for spent fuel disposal. An underground laboratory, to consist of many kilometers of tunnels and test rooms, is to be cut into the mountain with special boring equipment to determine if the site is suitable for a repository. 

Extraction of Bertrandite. Bertrandite-containing tuff from the Spor Mountain deposits is wet milled to provide a thixotropic, pumpable slurry of below 840 p.m (—20 mesh) particles. This slurry is leached with sulfuric acid at temperatures near the boiling point. The resulting beryUium sulfate [13510-49-1] solution is separated from unreacted soflds by countercurrent decantation thickener operations. The solution contains 0.4—0.7 g/L Be, 4.7 g/L Al, 3—5 g/L Mg, and 1.5 g/L Fe, plus minor impurities including uranium [7440-61-1/, rare earths, zirconium [7440-67-7] titanium [7440-32-6] and zinc [7440-66-6]. Water conservation practices are essential in semiarid Utah, so the wash water introduced in the countercurrent decantation separation of beryUium solutions from soflds is utilized in the wet milling operation. 

Po22olans iaclude natural materials such as diatomaceous earths (see Diatomite), opaline cherts, and shales, tuffs, and volcanic ashes or pumicites, and calciaed materials such as some clays and shales. By-products such as fly ashes and siUca fume are also employed. In the United States the proportion of po22olan iaterground with clinker has varied from 15 to over 30%, whereas ia Italy, cements with a 30—40% po22olan content are produced. 

Tuff, m. tuff, tufa dust, tuffartig, a. tufaceous. 

Tuff-erde, /. tufaceous earth, -kalk, m. tufaceous limestone, -stein, m. tufa, tuff, tuffsteinartig, a. tufaceous. 

Yucca Mountain, if it becomes the site for the isolation of SNF, will be laced with tunnels, waste in storage casks and monitoring equipment. A waiting period is planned while better isolation alteniadvcs are sought. IfYucca Mountain is not used, it is to be refilled with the tuff material removed earlier. In the United States the SNF that would be isolated in Yucca Mountain would be waste that has not been reprocessed it would be material that has come out of nuclear reactors and has been cooled at the plant site. 

Wolfsberg, K. Aguilar, R.D. Bayhurst, B.P. Daniels, W.R. DeVilliers, S.J. Erdal, B.R. Lawrence, F.O. Maestas, S. Mitchell, A.J. Oliver, P.Q. Raybold, N.A. Rundberg, R.S. Thompson, J.L. Vine, E.N. "Sorption-Desorption Studies on Tuff. III. A Continuation of Studies with Samples from Jackass Flats and Yucca Mountain, Nevada", Report LA-8747-MS, Los Alamos National Laboratory, 1981. 

Clevelend, J.M. Rees, T.F. Nash, K.L. "Plutonium Speciation in Selected Basalt, Granite, Shale, and Tuff Ground Waters", in press. 

V-Surficial, weakly coherent, alluvial deposits readily eroded by water. (Vj-<3 percent slope V2-<12 percent slope). I-Incompetent, or weakly coherent, bedrock such as shales and tuffs readily eroded by water and (or) prone to mass movement on steep slopes (li-<12 percent slope l2->12 percent slope). C-Competent, or strongly coherent, bedrock such as layered lava flow rocks and igneous intrusives not readily eroded by water, nor generally prone to mass movement except for rockslides and rockfalls from very steep slopes and cliffs (Ci-<12 percent slope). 

These different sites of hydrothermal and ore-forming activity may have resulted from the mode of subduction of the Pacific Plate. Mariana-type subduction (characterized by a steep angle of subduction and back-arc basin formation Uyeda and Kanamori, 1979) during middle Miocene caused WNW-ESE extension, submarine hydrothermal activity, thick accumulation of bimodal (basaltic and dacitic) volcanic activity (Green tuff) and Kuroko-type formation (Shikazono and Shimizu, 1993). Plio-Pleistocene Chilean-type subduction (shallow-dipping subduction zone, E-W compression Uyeda and Kanamori, 1979) and oblique subduction of the Pacific Plate beneath the North American Plate led to uplift and expansion of land area, subaerial hydrothermal activity accompanied by meteoric water circulation, subaerial andesitic volcanic activity and formation of vein-type deposits. 

Kuroko deposits occur in the Green tuff region which is characterized by thick altered volcanic and sedimentary piles of Miocene age. 

It is clear in Fig. 1.10 that the distribution of Kuroko deposits is restricted in a narrow zone in the Green tuff region which was called a Kuroko belt by Inoue (1969). This belt was formed by rapid subsidence under the extensional stress regime and is thought to have been a back-arc depression zone at middle Miocene age. The relationship between tectonic setting and formation of Kuroko deposits is discussed in section 1.5. 

Kuroko-type Gypsum or Barite Green Tuff Beit of Japan Clusters of Kuroko Deposits... 

Figure 1.10. The distribution of the Green Tuff belt of Japan and the Kuroko-type massive sulfide deposits within it. Major mining districts are labeled and ore deposit clusters outlined (Cathles, 1983a).

Menaichizawa, Sasahata), is composed mostly of brecciated andesite lavas and andesitic hyaloclastics. This formation is conformably overlain by the formation (Hotakizawa, Sunakobuchi) composed of thick sequence of basaltic lavas and tuff breccias with minor intercalations of mudstone and felsic tuff. 

The formation which is mostly composed of dacite lavas, tuff breccia and mudstone (Hanaoka, Yukisawa, Uwamuki formations) conformably overlies the Hotakizawa and Sasahata formations. The thickness of these formations is 300-400 m. Kuroko ore deposits occur at the upper part of this formation. White rhyolite lava domes characterized by intense sericite alteration have a close spatial relationship with Kuroko deposits. 

The younger formations (Ittori, and Tobe formations) of late Miocene to Pliocene overlie the Shishigamori, Shigenai and Harukizawa formations and are comprised mostly of mudstones, interbedded felsic tuffs, and tuffaceous sandstones. The total thickness of these formations is ca. 500 m. The formations of Pleistocene unconformably overlie the... 

Negative Eu anomaly is observed for hydrothermally altered dacite underlying the Kuroko ores and anhydrite in the dacitic tuff breccia. 

Epithermal base-metal vein-type deposits are distributed in the Green tuff region (Southwest Hokkaido, Northeast Honshu) (Fig. 1.62). The distribution area of this type of deposits is nearly same as that of Kuroko deposits. For example, large deposits (Osarizawa Cu-(Au) Ani Cu-Au Hosokura Pb-Zn deposits) occur in Northeast Honshu, but are more widely distributed in the Green tuff region than Kuroko deposits. 

Figure 1.62. Location of epithermal-type deposits in Japan (Shikazono and Shimizu, 1988a). 1 Green tuff and subaerial volcanic region of Tertiary/Quaternary ages, 2 Main Paleozoic/Mesozoic sedimentary terranes, 3 Main metamorphic terranes. TTL Tanakura tectonic line, ISTL Itoigawa-Shizuoka tectonic line, MTL Median tectonic line. Open circle epithermal Au-Ag vein-type deposits, solid circle epithermal base metal vein-type deposits, open triangle epithermal Au disseminated-type deposits.

Nekko Dacite Ys isawa Fonnation dacite lava tuff breccia +500tn... 

Nekko Volcano (dacite lava, tuff breccia)... 

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