Wall Zone Research Articles

壁式構造の解法の基礎的研究 (その 1) : 壁柱の幅が梁成に比べて非常に大きい場合の剛域の研究

Currently available methods for elastic analysis of wall frame structures are equivalent frame analogy with effective lengths of beams increasing by an amount equal to fourth their depth at each end considering the effect of local deformation at the beam-to-wall junctions. In this paper, the wall zone is taken as an a semi-infinite elastic plane and the beam as cantilever. Normal and sher stresses at the wall boundary can be found by photoelastic experiments, from which deformations are calculated as two dimentional elastic problems. The beam should be extended by half the beam depth at each end. The effects of local shear deformations are calculated as reduction factors for the beam shearing stiffnesses proportional to span to depth ratios.

Floor-fractured lunar craters

Numerous lunar craters (206 examples, mean diameter = 40km) contain pronounced floor rilles (fractures) and evidence for volcanic processes. Seven morphologic classes have been defined according to floor depth and the appearance of the floor, wall, and rim zones. Such craters containing central peaks exhibit peak heights (approximately 1km) comparable to those within well-preserved impact craters but exhibit smaller rim-peak elevation differences (generally 0–1.5km) than those (2.4km) within impact craters. In addition, the morphology, spatial distribution, and floor elevation data reveal a probable genetic association with the maria and suggest that a large number of floor-fractured craters represent pre-mare impact craters whose floors have been lifted tectonically and modified volcanically during the epochs of mare flooding. Floor uplift is envisioned as floating on an intruded sill, and estimates of the buoyed floor thickness are consistent with the inferred depth of brecciation beneath impact craters, a zone interpreted as a trap for the intruding magma. The derived model of crater modification accounts for (1) the large differences in affected crater size and age; (2) the small peak-rim elevation differences; (3) remnant central peaks within mare-flooded craters and ringed plains; (4) ridged and flat-topped rim profiles of heavily modified craters and ringed plains; and (5) the absence of positive gravity anomalies in most floor-fractured craters and some large mare-filled craters. One of the seven morphologic classes, however, displays a significantly smaller mean size, larger distances from the maria, and distinctive morphology relative to the other six classes. The distinctive morphology is attributed, in part, to the relatively small size of the affected crater, but certain members of this class represent a style of volcanism unrelated to the maria - perhaps triggered by the last major basin-forming impacts.

Graphic intergrowths of feldspars and quartz in some Czechoslovak pegmatites

Graphic intergrowths of alkali feldspar+quartz, and plagioclase+quartz, occur together in pegmatites in the eastern part of the Czechoslovak Moldanubicum. They form zones between the finer-grained wall zone and the central blocky feldspar+quartz core. The normative Or-Pig-Q compositions of the graphic intergrowths and the Or-Ab-An contents of their feldspars show broad variations generally, but have a restricted range within individual pegmatites. At two localities studied in more detail, coexisting feldspars show gradual changes in composition, from the margins up to the innermost graphic pegmatite, compatible with fractional crystallization along the feldspar solidus-solvus intersection in the Or-Ab-An-Q-H2O system, at different vapour pressures in different pegmatites. Two models are demonstrated for low and high pressure cases. The feldspar compositions from central blocky zones deviate from the magmatic fractional crystallizations paths; this corresponds with the general assumption that they crystallized from supercritical gaseous fluids.

Flow over high roughness elements

The mean velocity and longitudinal turbulence-intensity distributions inside the zone of and above high roughness elements were investigated experimentally. This was accomplished by using a model forest canopy. The results indicate that the flow may be divided into transition and fully-developed flow regions, followed by a short adjustment distance near the downstream terminus of the rough boundary. The transition region has a strong effect on the flow characteristics within and above the layer of roughness elements. Generally, a similar qualitative variation for both velocity and turbulence was found inside and above the roughness zone, whose influence extends to more than three times the roughness height. Investigation of the modified universal logarithmic law for describing the velocity variation above the roughness zone revealed that both of the so-called similarity parameters, i.e., friction velocity and roughness length, are not local constants. On the contrary, for a given flow and local conditions they vary drastically with height. It is suspected that this is due to the fact that the classical assumption of constant shear stress throughout the boundary layer or significant portions of it is not satisfied in the case of roughness elements many times greater in height than the thickness of the viscous wall zone.

Uredospore development in Puccinia graminis

The present paper reports a number of electron microscope observations on the protoplasm and walls of developing spores which provide additional information on uredospore wall and spine development and on the fine structure of organelles, particularly of mitochondria and endoplasmic reticulum and of lipid bodies in developing spores. Micrographs of partially extracted uredospore walls and of chromium-shadowed extracted sections demonstrate the architecture of the wall as seen in cross and tangential section. Three distinct wall zones are clearly visible with the external wall layer forming the boundary of the germinal pore.

Genesis of the White Cloud and Related Pegmatites, South Platte Area, Jefferson County, Colorado

The writer mapped in detail the geology of an area of approximately 12 square miles, including South Platte, Colorado, to ascertain the geologic setting of large, concentrically zoned, rare-earth-bearing pegmatite bodies. These occur within granite of the northeastern portion of the Pikes Peak batholith. The outer batholithic zone of granite contains platy flow structure concentric with the concordant contact between the batholith and metasomatized metamorphic wall rocks, indicating emplacement of a mobile magma in the mesozone. Pegmatite and aplite dike emplacement, as well as development of tensional quartz veins with deuteric wall rock alteration and fluorite veins, mark the late stages of batholith formation. The rare-earth-bearing pegmatite bodies are lens-or pod-shaped, with quartz cores surrounded by four concentric but commonly incomplete zones. These zones are generally: (1) wall zones of graphic granite; (2) outer-intermediate zones of biotite, cyrtolite, and perthite; (3) middle-intermediate zones of giant perthite crystals; and (4) inner-intermediate zones of euhedral fluorite crystals. Compromise surfaces between some minerals are interpreted as evidence of simultaneous growth; crystallization is believed to have proceeded from the pegmatite walls inward following Bowen9s reaction series. Replacement at the White Cloud pegmatite consists of perthite by albite, fluorite by yttrofluorite, yttrofluorite by doverite, quartz and allanite by fluorite, biotite by hematite, quartz by sericite, and gadolinite by an unidentified fluocarbonate of yttrium with an X-ray structure similar to bastnae-site. Several rare-earth minerals have not been identified. Pegmatite emplacement is believed to have taken place by: (1) liquid segregation in a giant miarole, or (2) autointrusion, or (3) a combination thereof in the early stages of batholith crystallization. Paragenesis is interpreted in the light of recent laboratory findings of other workers supporting resurgent boiling and the action of a vapor phase as a transfer medium in replacement.

The Peg Claims spodumene pegmatites, Maine

The Peg Claims pegmatites are located SW. of Rockland in the towns of Warren and Cushing, Knox County, Maine. These pegmatites are representative of a group of zoned, granitic, Li-bearing pegmatites in which spodumene is present nearly from wall to wall. The pegmatites are discordant, steeply dipping, tabular bodies in the Penobscot quartz-mica schist near the Waldoboro granite. A narrow quartz- tourmaline-muscovite-apatite aureole is commonly developed around each of the pegmatites and around inclusions of country rock in the pegmatites. The pegmatites are zoned, and each may be subdivided into: 1) a narrow quartz-muscovite border zone; 2) a narrow albite-quartz-muscovite wall zone; and 3) an albite-quartz-spodumene-perthite core that constitutes most of the pegmatite. Cross-cutting, fine-grained, quartz-albite-spodumene-muscovite lenses are found within pegmatite cores. The bulk mineralogy and variations in the mineralogy from zone to zone of the largest body (Dike 1) were determined by megascopic mineral point-counts. There is a decrease of albite, quartz, and muscovite and an increase of spodumene and perthite from the border and wall zones into the core. The alkali contents of Dike 1 and of each of its zones were determined by flame photometer and X-ray fluorescence analyses. The amount of Na 2 O decreases and the amounts of K 2 O, Li 2 O, Rb 2 O, and Cs 2 O increase from the border and wall zones into the core. Estimated bulk compositions of Dike 1 and of each of its zones were computed. It is concluded that the distribution, structural features, bulk chemistry, and the mineralogical, chemical, and textural zoning of the pegmatites are consistent with development by fractional crystallization of a pegmatitic fluid in a restricted system.

Geology and Origin of the Pollucite-Bearing Montgary Pegmatite, Manitoba

The Montgary Pegmatite in southeastern Manitoba is a large, complexly zoned, spodumene-bearing body containing the world9s largest known reserves of pollucite. The pegmatite is near the margin of a granitic intrusive rock and forms an elongate, disc-shaped body lying more or less perpendicular to the near-vertical schistosity of the enclosing Precambrian plagioclase amphibolite. The amphibolite has no compositional or textural trends beyond a narrow alteration zone that can be correlated with distance from the pegmatite. The alteration zone, 4–6 feet in average width, contains small amounts of glaucophane, biotite, apatite, and tourmaline in addition to the normal mineral assemblage of the amphibolite. The pegmatite is subdivided into six zones, two replacement bodies, and a unit that may be a replacement body. The six zones are: (1) a quartz–albite border zone; (2) a perthite–quartz–plagioclase–muscovite wall zone; (3) a spodumene–perthite–plagioclase–quartz intermediate zone; (4) a spodumene–quartz intermediate zone with minor perthite; (5) a microcline-quartz intermediate zone, and (6) a quartz core. Neglecting the quartz core and considering the two spodumene–bearing zones as one, the internal structure is one of concentric shells. Aplitic albite replaces lower portions of the spodumene-bearing zones and upper portions of the footwall portion of the wall zone. Fine-grained lepidolite replaces parts of the microcline-quartz intermediate zone. Pollucite forms very fine-grained, monomineralic bodies cut by veins of quartz; these bodies are tentatively regarded as replacement bodies. Lithia has been concentrated toward the hanging wall and up the dip of the pegmatite. The attitude of the pegmatite and the shape of the hanging wall amphibolite–pegmatite contact exerted an important control over lithia distribution during crystallization. An igneous hypothesis of origin is the most acceptable. Pegmatitic fluids, probably related to the nearby granitic intrusive rock, were permissively introduced into a dilatant zone along a sinuous shear. The internal structure is consistent with fractional crystallization accompanied by resurgent boiling of the residual liquid in a restricted system. Deposition of crystals took place from the walls inward. The zonal structure has been influenced, but not caused, by the attitude of the pegmatite. Upward lithia concentration is consistent with the development of a second fluid phase by resurgent boiling following the deposition of wall-zone material. Alkali-replacement bodies were formed late in the history of the pegmatite. The fluids responsible for their formation were probably either vapors formed by resurgent boiling or residual fluids left over after the main pegmatite crystallization.

Radiant Heat Transfer in Gas-filled Cylindrical Enclosure with Temperature Gradient

Calculations of heat transfer rates in cylindrical furnaces, making rigorous allowance for axial radiant heat flux, were carried out, and the results were used to evaluate existing approximate methods of calculation. A Fortran program for the IBM 709 was written to calculate the radiantconvective heat fluxes for gas-filled cylindrical furnaces using the Hottel-Cohen method of zoned analysis and making use of the direct interchange areas for cylindrical furnaces calculated by H. Errku.The major assumptions made in the formulation of the program are that there are no radial temperature gradients or gas recirculation, i.e., plug flow of the combustion gases is assumed in the furnace.The heat transfer rates were calculated for eighteen sets of conditions. The design parameters investigated were length-to-diameter ratios of two and four and diameters of two and four feet. The operational variables studies were sink temperatures of 1460°K and 2460°K, and enthalpy feed rates of 100×104, 50×104 or 25×104, and 6.25×104 Btu/hr·cu.ft. The furnace walls were treated as heat sinks with an emissivity of 0.8 and the end walls as refractories with an emissivity of 0.5. The fuel was assumed to have a composition corresponding to (CH2) n and to be instantaneously burned with a stoichiometric amount of air. No flame luminosity was assumed.From the results it was found that 90% of the net heat flux to any wall zone originated in the gas zone contiguous with it and the adjacent gas or end zoned.The results of the computer runs were compared with two approximate methods of calculating furnace performance. One method, which formulates the heat flux neglecting the net radiation along the axis of the furnace but allowing for the axial gas temperature gradient, was found to give heat fluxes from 9.1% lower at high firing rates to as much as 12% higher at lowest firing rates. The error in heat flux distribution along the furnace was larger still, ranging from +24% to -12%.A completely stirred furnace approximation with the heat-transfer temperature equal to the exit temperature gave total fluxes which ranged from 1.2% to 18.7% lower than the computer calculations at high and low firing rate, respectively.The overall efficiencies of the eighteen runs were correlated as a function of dimensionless parameters defining the design and operational variables within 3%. Also, corrections to be added to the exit gas temperature to give the “effective” heat transfer temperature of a well-stirred chamber of equivalent performance were calculated and correlated as a function of a dimensionless parameter. The magnitude of the correction ranged from 570°F to 60°F. Either correlation gives a mean of predicting furnace performance for furnace where radial temperature gradients and gas recirculation are unimportant.The efficiencies of the plug-flow furnaces studied here and of the well-stirred furnaces bracket that of real furnaces. Consequently, the present calculations indicate the range of possible error in estimating the thermal efficiency of furnaces by various simple but inaccurate models.

Mineralogy of a uraninite-bearing pegmatite, Lac La Ronge, Saskatchewan

The Nunn Lake uraninite pegmatite is a large, well zoned sill-like body. Uraninite occurs within the outer three feet of the wall zone, as sheet-like masses within an aplitic phase of the pegmatite, and as late fracture fillings.Deposition of the uraninite took place in two stages. The first stage was crystallization within and contemporaneous with the potassium-rich wall zone. The second stage was the crystallization of the uraninite within aplitic phases of the pegmatite and as late fracture fillings. This second stage of uraninite crystallization is in direct association with a mineral assemblage that is evidence of a late residua of alkali potassium silicate and the acid radicals of the halides.

Pegmatitic lithium deposits in Canada

Granitic pegmatites containing lithium minerals occur in the Yellow-knife-Beaulieu district, Northwest Territories; the Cat Lake-Winnipeg River, the Herb Lake, and East Braintree-West Hawk Lake districts, Manitoba; and the Preissac-Lacorne district, Quebec.Several general characteristics are exhibited: 1. The pegmatites occur in medium- to high-grade metamorphic rocks or in plutonic rocks. 2. They are associated spatially and perhaps genetically with bodies of granite that contain 20 to 40 percent microcline and 20 to 40 percent albite or oligoclase. 3. They are marginal and exterior pegmatites. 4. In districts where regional zonation of granitic pegmatites is present, the pegmatites richest in lithium minerals are farthest from the center of the associated body of granite. 5. In pegmatite bodies that contain spodumene from wall to wall except for discontinuous, narrow border and, or, wall zones, many or almost all of the spodumene crystals are oriented with their long axes perpendicular to the walls, and are too fine-grained to be hand-sorted on a commercial scale. 6. Cleavelandite is generally a principal component of the wall zones. 7. In a given internal structure unit, spodumene is one of the early minerals to form. 8. Replacement bodies containing spodumene have not been found. 9. Amblygonite and montebrasite have been found only in intermediate zones.Spodumene is the most abundant lithium mineral and it occurs in intermediate zone deposits, in thinly lenticular pods, and in pegmatite bodies that are essentially spodumene-bearing from wall to wall.The bulk of the present lithium reserves in Canada is contained in pegmatite bodies that are essentially spodumene-bearing from wall to wall. These bodies are typically dike-like or thinly lenticular in shape. The grade and grain size of the spodumene in deposits of this type are remarkably uniform. At present, two companies are considering the development of such deposits in the Preissac-Lacorne district, Quebec.

The Paragenesis of the Varuträsk Pegmatite

AbstractA preliminary report is presented on the paragenesis of the Varuträsk pegmatite, situated about 10 km. from Skellefteå, in Sweden. Three main stages can be distinguished (a) An epimagmatic-pegmatitoid stage during which the primary zonal development of the pegmatite body into border zone, wall zone, intermediate zones, and core was accomplished; (b) a hydrothermal replacement stage, divisible into a high temperature phase with a Li-replacement unit and a Cs-replacement unit, and a lower temperature phase with a cleavelandite replacement unit and a feebly developed fluorite unit (c) a final stage of supergene alteration. The age of the pegmatite lies between 1650 and 1800 million years.

Pegmatites of the Van Horn Mountains, Texas

Zoned and unzoned perthite-quartz-plagioclase-muscovite pegmatites in the form of tabular bodies, irregular bodies with tabular branches, irregular masses, elongate lenses, lit-par-lit zones, and small augen and stringers are distributed throughout the Precambrian metasedimentary rocks of the Mica Mine area, Van Horn Mountains, Texas. Zoned bodies have a core of perthite and quartz and a plagioclase-quartz-perthite-muscovite wall zone. The pegmatites contain numerous schist inclusions, and some show evidence of contamination by biotite schist and amphibolite.Intimate penetration of the host rock by pegmatite fluids was accomplished by a combination of dilation and digestion. Dilation was effected by injection pressure and (to an unknown degree) orogenic stresses. Crystallization of a solution containing a large excess of potash took place in a closed or restricted system where a delicate balance of solubility factors was maintained for long periods or in a solution of low viscosity, thus facilitating growth of large crystals about a limited number of centers. Zoning and textural relationships are accounted for under these conditions. The importance of horizon and mode of emplacement in the formation of pegmatite textures and shapes is emphasized. A review of the granitization, palingenesis or anatexis, open-system (or aqueous), and magmatic theories of pegmatite origin shows that the features of Mica Mine pegmatites are best explained by the magmatic theory.The Mica Mine area has possibilities of exploitation for feldspar and scrap mica.