Carbonate Pellets Research Articles

EFFECTIVE DIFFUSIVITIES IN CALCIUM CARBONATE AND CALCIUM OXIDE SOLID PELLETS

Effective diffusivities in calcium carbonate and calcium oxide pellets have been determined by steady state diffusion method. It has been found that the diffusion in the solid pellets is controlled both by molecular and Knudsen mechanisms. The value of the tortuosity factor obtained is approximately 2 for these solid pellets.

XPS studies on strontium compounds

XPS measurements have been made on strontium carbonate, strontium oxide and strontium nitrate pellets and on strontium plate. For the latter substrate, the composition of the surface overlayer formed after prolonged exposure to dry air and the composition of the overlayer after scraping under doubly filtered argon has been examined. The effect of floodgun setting on the binding energies of the scraped strontium plate has been investigated. Finally, the effect of argon ion etching on the composition of the surface of scraped strontium plate has been examined.

Oxygen-minimum zone edge effects: Evidence from the central California coastal upwelling system

Geologic and biological data from box cores, gravity cores, and bottom photographs across the modern coastal upwelling system of central California reveal that biogeochemical activity increases along the edges of the oxygen-minimum zone (OMZ; <0.5 ml/1 O2). Macrofauna and benthic foraminifers, as well as relative concentrations of calcium carbonate, glauconite, and fecal pellets, all display edge effects. The major controls appear to be a combination of dissolved oxygen concentration of near-bottom waters, bottom currents, and possibly bacterially mediated nutrient recycling, as well as food supplies. OMZ edge effects should be recognizable in the rock record and may prove to be powerful paleoenvironmental/paleoecological indicators.

XPS studies on strontium compounds

XPS measurements have been made on strontium carbonate, strontium oxide and strontium nitrate pellets and on strontium plate. For the latter substrate, the composition of the surface overlayer formed after prolonged exposure to dry air and the composition of the overlayer after scraping under doubly filtered argon has been examined. The effect of floodgun setting on the binding energies of the scraped strontium plate has been investigated. Finally, the effect of argon ion etching on the composition of the surface of scraped strontium plate has been examined.

A Benchmark Experiment on Tritium Production and Radiation Heating in the LiF Assembly

An integral benchmark experiment on the Lithium Fluoride (LiF) material has been carried out in order to check the accuracy of neutronic design calculations. Experimental data of the tritium production rate and the radiation heating rate have been measured directly by each technique using Lithium Carbonate (Li/sub 2/CO/sub 3/) pellets and LiF thermo-luminescent dosimeters (LiF-TLDs), and indirectly by the multi-activation foil technique. The present accuracies of the neutronic calculations on the tritium breeding and the nuclear heating are discussed through comparing these benchmark data, where the two-dimensional transport code DOT 3.5 and the ENDF/B-IV cross-section library are applied as a typical example.

Plasma levels of tegafur following implantation of polycarbonate pellets containing tegafur or FD-1 into rats.

The possible use of poly (ethylene carbonate) and poly (propylene carbonate) pellets for sustained release of 5-fluorouracil derivatives (tegafur and FD-1) has been examined in vivo. Plasma levels of tegafur following implantation of the polycarbonate pellets into the rat peritoneal cavity were determined by high pressure liquid chromatography. Sustained release of the drug was obtained over 50d following implantation of poly (propylene carbonate) pellets containing 40% FD-1. Plasma level profiles in vivo were compared with release profiles in vitro. Plasma level profiles with multiple peaks were observed following implantation of FD-1 in poly (propylene carbonate) pellets and tegafur in poly (ethylene carbonate) pellets.

Examination of biodegradability of poly(ethylene carbonate) and poly(propylene carbonate) in the peritoneal cavity in rats.

The biodegradability of poly (ethylene carbonate) and poly (propylene carbonate), synthesized from carbon dioxide and alkylene epoxides, was investigated. The biodegradation of poly (ethylene carbonate) pellets in the peritoneal cavity in rats was observable 2 d after implantation and was nearly completed within 2 weeks. The degradation of poly-(propylene carbonate) pellets was not measurable after 2 months. The degradation rate of the pellets made of mixtures of the two types of polycarbonates decreased with increase in poly (propylene carbonate) content. No retardation in body weight gain was observed in polycarbonate-implanted rats. No visible undesirable reaction was observed at the implanted sites.

Hydrodynamics of Carbonate Fecal Pellets

ABSTRACT Sand-sized carbonate fecal pellets are a common to dominant constituent of many shallow marine tropical environments. Ovoid pellets 100-1000 µ in median diameter predominate. Pellets may be soft or hardened by intragranular micritization or cementation. Single grain settling of pellets collected from eight shallow marine environments in south Florida and the Bahamas permits calibration with the hydrodynamic behavior of quartz spheres. Well-hardened carbonate pellets settle at rates equivalent to quartz spheres having a median diameter 70 percent to 100 percent of the pellet size. Soft carbonate pellets containing abundant silt settled as quartz spheres 90 to 30 percent in diameter. Soft carbonate pellets composed mainly of aragonite needle mud settled as quartz spheres 60 to 25 ercent in diameter. From this data, preliminary estimates can be made of the shear velocities necessary for entertainment of pellet or peloidal sands and the propensity of suspended versus bedload transport of different grain types and sizes.

Palaeoaplysina (Hydrozoan?) Carbonate Buildups from Upper Paleozoic of Idaho

The plate-shaped calcareous hydrozoan? Palaeoaplysina Krotov is the main fossil in Late Pennsylvanian and Early Permian carbonate buildups in the Lemhi Range and Arco Hills of east-central Idaho. Palaeoaplysina has an internal subparallel canal system imbedded in cellular tissue, and mamelon-like surface protuberances. Other fossils in the buildups include the calcareous phylloid alga Eugonophyllum, other unidentified phylloid algae, crustose bryozoans, and less common gastropods, crinoids, and brachiopods. Buildup sediment accumulated primarily by the baffling and entrapment of loose carbonate pellets, lime mud, and skeletal fragments in protected pockets and hollows between Palaeoaplysina and algal plates. There is a continuum between tabular and lenticular buildup geometries. Broad tabular buildups are typically 2 to 10 m thick and as much as 15 km wide. The basal surfaces of the tabular buildups conform to previous sea-floor topography, whereas upper surfaces are relatively flat and planar, suggesting that the buildups were limited in upward growth because they formed in the uppermost subtidal zone. The abundance of porcelaneous tubular foraminifers (resembling apterrinellids and Hedraites), which encrusted some unpreserved organisms, suggests that some buildups were carpeted by unfossilized vegetation such as noncalcareous algae. Strongly lenticular buildups are typically 2 to 16 m thick and a few tens to hundreds of meters wide. Most were large enough to modify depositional conditions nearby, resulting in fore-mound and back-mound beds. All of the lenticular buildups, and some of the tabular ones, stood topographically above the adjacent sea floor while they formed. Some buildups are stacked one above another. Others are in offlapping sequences which also include lenticular beds of crinoidal-bryozoan lime wackestone and grainstone.

Lower Cretaceous Carbonate Beaches: ABSTRACT

Several carbonate beach sequences have been recognized and studied in Lower Cretaceous shallow-marine shelf limestones of the Edwards Formation, Central and West Texas. These sandstone bodies are local features associated with exposed insular areas developed in response to remnant structural features combined with biologic and normal sedimentologic processes (sand banks and rudist reefs). From top to bottom, 4 zones are recognized: backshore, beach foreshore, upper offshore, and lower offshore. The backshore consists of laminated, mud-cracked, fine-grained supratidal dolomite with gypsum molds and associated paleosoils. Thin washover deposits of coarse calcareous sands are common. The beach foreshore consists of a coarse rudist carbonate grainstone with a subaerial crust developed at the top. The dominant sedimentary structures are inclined laminations, accretion bedding, and vugs. Collapsed beachrock slabs are common. The upper offshore consists of poorly sorted rudist carbonate packstone with some finely interbedded coarse rudist carbonate grainstone and pellet carbonate packstone. This zone may contain festoon crossbedding trending normal to the direction of beach accretion. Beach rock cobbles derived from the beach foreshore zone above are common. The lower offshore zone consists of an echinoid-pellet carbonate packstone with common burrows and some festoon crossbedding. Useful criteria for the recognition of ancient carbonate beaches are: vertical sequence of sedimentary structures, from accretion beds at top to burrows at base; vertical sequence of texture and fabric from coarse, well-sorted grainstones at top to poorly sorted fine-grained packstones at base; presence of evaporative supratidal facies at the top of the sequence; and association of keystone vugs and beachrock slabs with the accretion-bedded part of the sequence. End_of_Article - Last_Page 641------------

Origin and Distribution of Glauconites and Related Clay Aggregates on Sea Floor off Southern California: ABSTRACT

Studies have been made of about 1,300 glauconitic samples from the sea floor off southern California, in Monterey Bay, California, and off Cedros Island, Baja California. The principal depositional environments are continental terraces, banks, ridges, and basin slopes. Clay aggregates that probably would be designated as glauconite, according to contemporary field usage of the term by geologists, grade from relatively soft, pale yellow-green, highly expandable montmorillonitic types to dark green, illitic types. As lattice thickness [d(001)] of these different types increases, the refractive index and potassium content decreases. The organic nitrogen content is greatest in highly expandable varieties. Glauconite may compose from less than 1 per cent to about 80 per cent of the upper few centimeters of sediment. Maximum concentrations occur in the sediments from the outer shelf and upper slope areas, but the distribution is patchy, both areally and vertically, within these sediments. Glauconite is rare in water depths of less than 100 feet. Off southern California, glauconites that probably have been deposited from turbidity currents occur in near-surface sediments from the continental rise and on the abyssal floor. Living benthonic Foraminifera of the same species as those that are filled with expandable glauconite occur in water depths that range from approximately 100 feet to 6,000 feet. Specimens of the genus Cassidulina are common in Foraminiferal faunas that contain abundant glauconite-filled tests. Glauconite replaces argillaceous sedimentary rock, mineral grains, organic carbonate, and probable fecal pellets. Some spheroidal-ellipsoidal and irregular-papillate forms appear to be of accretionary origin. The mineralogy and morphology of fillings in Foraminifera indicate that they are probably deposited by direct precipitation. Distinctive morphological varieties of glauconite are not everywhere randomly distributed, but are commonly concentrated in localized areas, which indicates that variations in morphology may be caused by local conditions of origin. Glauconites have been recognized that are reworked from Pliocene, and perhaps Miocene, submarine outcrops. Foraminiferal tests that are filled with glauconite range in age from Pliocene to Recent and from Pleistocene to Recent. No direct evidence of present-day formation of glauconite has been found. End_of_Article - Last_Page 275------------

Facies Relationships in Mississippian of Williston Basin and Their Effects upon Fluid Migration: ABSTRACT

A study of available sample longs of the Mississippian Madison carbonates and chemical sediments of the Williston basin reveals a sequence of limestone types which grade from deep, quiet-water limestones through shallow, open-marine shelf-type limestones into a shallow, agitated-water clastic limestone of a barrier shoal facies. These units grade updip into a depositional environment of restricted circulation characterized by evaporites. The three major stratigraphic units are Lodgepole, Mission Canyon, and Charles. Each of these units can be traced through all or part of this sequence. In the center of the basin the individual units generally display this pattern in the following manner: the Lodgepole formation is representative of a fairly quiet, deep-water environment ndicated by fine-grained, argillaceous carbonates with rare fossil remains, some chert, and here and there some pyrite. The dominant lithologic character of the Mission Canyon formation consists of finely crystalline to chalky matrix enclosing bioclastic remains and carbonate pellets with some true oolites, indicating deposition under moderately shallow conditions of open-marine environment. The Charles formation is composed of evaporites and fine-grained argillaceous limestones with zones of fossil remains, pellets, and oolites, and is representative of lagoonal, shallow and/or restricted water deposition. No formation is wholly barrier bank lithologically, but characteristic barrier lithologic type consisting of texturally mature bioclastics can be seen locally in all three units. Rese voir characteristics of porosity and permeability within the barrier zone are directly related to the degree of textural maturity, in that primary porosity and permeability are greater in sediments which have undergone better rounding, sorting, and winnowing by wave action. The fine-grained, argillaceous sediments of the basin deposits though locally porous, have only sub-capillary openings and present considerable resistance to fluid flow because of surface fraction between the carbonate particles and the fluid medium. The shelf-type carbonates, though containing abundant clastic material, show a very low degree of textural maturity, and here also, surface fraction of sub-capillary openings inhibits free movement of fluids. The texturally mature clastic limestone within the barrier-bank facies furnishes the best avenues for fluid movement and also the best reservoir rock. The presence of sparry calcite cement in the texturally mature calcarenites of the barrier indicates a high degree of original porosity and permeability. A potential reservoir cemented with sparry calcite or sparry anhydrite could retain its original porosity in an updip direction if a trap is present. The concepts of mineral cements and of textural maturity previously applied to sandstones should be extended to include clastic limestones. End_of_Article - Last_Page 1106------------