Isotopic evidence for the magmatic and tectonic histories of the Carolina terrane: implications for stratigraphy and terrane affiliation     

Stephanie Ingle  Paul A. Mueller  Ann L. Heatherington  Marianne Kozuch 《Tectonophysics》2003,371(1-4):187-211

Establishing the age and crustal nature of exotic terranes and their underlying basements helps to determine their paleogeographic origin and tectonic histories. We present U–Pb ages of zircons and Sm–Nd whole rock isotopic data for volcanic and plutonic rocks of the Carolina terrane, one of several peri-Gondwanan terranes that were accreted to the margins of the circum-Atlantic continents during the Paleozoic. Volcanism in this subduction-related arc culminated in the eruption of the Morrow Mountain rhyolite, at ca. 540 Ma; thus, magmatism in the Carolina terrane ceased at the beginning of the Cambrian. The presence of inherited zircons and non-juvenile depleted mantle model ages of Carolina slate belt rocks favor a basement that is, at least in part, composed of evolved continental crust. Ages of inherited xenocrystic zircons cluster at ca. 1000, 2100 and 2500 Ma. These ages, in addition to volcanism at ca. 618–540 Ma, correlate best with well-known tectonic events in present-day northern South America. Specifically, the Orinoquian-Sunsas, the Trans-Amazonian and the Central Amazonian orogenic zones are likely candidates for potential basement correlatives to the Carolina terrane. Sm–Nd isotopic signatures vary significantly, but permit assimilation of Orinoquian age (1000 Ma) crust by magmas derived from the depleted mantle in a subduction (arc-related) setting. Our findings are also consistent with proposed correlations between the Carolina terrane and Avalonia which is likewise believed to have formed along the northern margin of present-day South America.  相似文献   

Bacterial Production Stimulated Across the Zone of Influence of a Ground Water Circulation Well in a BTEX-Contaminated Aquifer     

Michael T. Montgomery  Barry J. Spargo  James G. Mueller  Richard B. Coffin  David C. Smith  Thomas J. Boyd 《Ground Water Monitoring & Remediation》2002,22(3):144-150

Benzene, toluene, ethylbenzene, and xylene (BTEX) hydrocarbons are typically the most abundant carbon source for bacteria in gasoline-contaminated ground water. In situ bioremediation strategies often involve stimulating bacterial heterotrophic production in an attempt to increase carbon demand of the assemblage. This may, in turn, stimulate biodegradation of contaminant hydrocarbons. In this study, ground water circulation wells (GCWs) were used as an in situ treatment for a fuel-contaminated aquifer to stimulate bacterial production, purportedly by increasing oxygen transfer to the subsurface, circulating limiting nutrients, enhancing bioavailability of hydrocarbons, or by removing metabolically inhibitory volatile organics. Bacterial production, as measured by rates of bacterial protein synthesis, was stimulated across the zone of influence (ZOI) of a series of GCWs. Productivity increased from ∼10² to >10⁵ ng C/L hour across the ZOI, suggesting that treatment stimulated overall biodegradation of carbon sources present in the ground water. However, even if BTEX carbon met all bacterial carbon demand, biodegradation would account for <4.3% of the total estimated BTEX removed from the ground water. Although bacterial productivity measurements alone cannot prove the effectiveness of in situ bioremediation, they can estimate the maximum amount of contaminant that may be biodegraded by a treatment system.  相似文献   

Stream response to repeated coseismic folding, Tiptonville dome, New Madrid seismic zone     

M. J. Guccione  K. Mueller  J. Champion  S. Shepherd  S. D. Carlson  B. Odhiambo  A. Tate 《Geomorphology》2002,43(3-4)

Fluvial response to tectonic deformation is dependent on the amount and style of surface deformation and the relative size of the stream. Active folding in the New Madrid seismic zone (NMSZ) forms the Tiptonville dome, a 15-km long and 5-km wide surface fold with up to 11 m of late Holocene structural relief. The fold is crossed by streams of varying size, from the Mississippi River to small flood-plain streams. Fluvial response of these streams to repeated coseismic folding has only been preserved for the past 2.3 ka, since the Tiptonville meander of the Mississippi River migrated across the area forming the present flood plain. This surface comprises a sandy point-bar deposit locally overlain by clayey overbank and silty sand crevasse-splay deposits, an abandoned chute channel infilled with laminated sandy silt and silty clay, and an abandoned neck cutoff filled with a sandy cutoff bar and silty clay oxbow lake deposits.Dating various stream responses to coseismic folding has more tightly constrained the timing of earthquake events in the central NMSZ and provides a means of partitioning the deformation amount into individual seismic events. Three earthquakes have been dated in the Reelfoot Lake area, ca. A.D. 900, 1470, and 1812. The latter two earthquakes had large local coseismic deformation. Both of these events were responsible for numerous stream responses such as shifting depocenters, modification of Mississippi River channel geometry, and derangement of small streams. Overbank sedimentation ceased on the dome as it was uplifted above the normal flood stage, and sedimentation of crevasse-splay deposits from the Mississippi River, colluvium from the scarp, and lacustrine sediment accumulated in the adjacent Reelfoot basin. The much larger Mississippi River channel responded to uplift by increasing its sinuosity across the uplift relative to both upstream and downstream, increasing its width/depth ratio across and downstream of the uplift, and decreasing the width/depth ratio upstream of the uplift. Despite the size of the Mississippi River, it has not yet attained equilibrium since the latest uplift 190 years ago. Small channels that could not downcut through the uplift were filled, locally reversed flow direction, or formed a lake where they were dammed.Uplift and stream response to folding along the Tiptonville dome is less dramatic between 2.3 and 0.53 ka. During this interval, abandoned channel fill and overbank deposition across the dome suggests that it was not a high-relief feature. One earthquake event occurred during this interval (ca. A.D. 900), but coseismic stream response was probably limited to a slight aggradation of a small flood-plain stream.  相似文献   

Spin-cast ZERODUR mirror substrates of the 8 m class and lightweight substrates for secondary mirrors     

Hartmut W. Hoeness  Rudolf Mueller  Erich W. Rodeck  Friedrich B. Siebers 《Astrophysics and Space Science》1989,160(1-2):193-197

For about 20 years SCHOTT has been supplying the glass ceramic ZERODUR, a material with very low thermal expansion. Besides many other applications, ZERODUR is excellently suited for the manufacture of mirror substrates for telescopes. About 80% of all telescopes in the western world with mirror diameters >1.8 m have been equipped with ZERODUR during the last 10 years. The development of modern astronomical telescopes is aimed at larger primary mirrors and lighter secondary mirrors.New techniques have been developed by SCHOTT for manufacture of thin monolithic mirror blanks of more than 8 m in diameter. The development of thin meniscus shaped shells using the spin-casting technique was successfully completed last year. During a test production several mirror substrates up to 4.1 m in diameter and down to 57 mm in thickness could be produced. The know-how has been acquired for the fabrication of mirror substrates of more than 8 m in diameter by the spin-casting technique.SCHOTT has also performed considerable developmental work in the field of lightweighted ZERODUR mirror substrates which can be generated using different techniques: forming of the lightweighted structure during casting, fusion of individual components to a total structure and lightweighting of a massive block by various mechanical machining methods.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.Registered trademark of SCHOTT Glaswerke, Mainz.  相似文献   

New near-aphelion light curves of Comet 2P/Encke     

Y.R. Fernández  S.C. Lowry  B.E.A. Mueller  M.J.S. Belton 《Icarus》2005,175(1):194-214

We present new, near-aphelion, time series of photometry of Comet 2P/Encke in Cousins-R band. With these light curves we find that the dominant, synodic rotational periodicity is either P₀=11.079±0.009 h or 2P₀=22.158±0.012 h. This is in contrast to data from the 1980s published by others that are consistent with 15.08- and 22.6-h periods. Those periods do not satisfy our phased light curves, and also the 1980s data are not easily reconciled with our periods. This could be due to P/Encke having non-principal axis rotation or due to a drift in the rotation period caused by outgassing torques. We observed the comet at five epochs: July, August, September, and October 2001, and September 2002, and the comet was at times intrinsically brighter than expected for a bare nucleus, due to an apparent contribution from an unresolved coma. Three-quarters of the data were obtained in the second and fifth epochs, and we analyzed these two time series using both the phase-dispersion minimization and “WindowCLEAN” techniques. At both epochs and with both techniques strong periodicities were found near frequencies and . By then using visual inspection of the phased light curves to corroborate these frequencies, and by using the data from the other three epochs to properly align light curve features, we were able to derive P₀ and 2P₀ as the only solutions that satisfy all our observations. The periodicity due to f₁ is clearly seen in our data, but we cannot tell from our data alone whether it is a manifestation of the nucleus's shape, non-principal axis rotation, or both.  相似文献   

Permeability and degassing of dome lavas undergoing rapid decompression: An experimental determination   总被引：1，自引：1，他引：0  

Sebastian Mueller  Oleg Melnik  Oliver Spieler  Bettina Scheu  Donald B. Dingwell 《Bulletin of Volcanology》2005,67(6):526-538

The gas permeability of volcanic rocks may influence various eruptive processes. The transition from a quiescent degassing dome to rock failure (fragmentation) may, for example, be controlled by the rocks permeability, in as much as it affects the speed by which a gas overpressure in vesicles is reduced in response to decompression. Using a modified shock-tube-based fragmentation bomb (Alidibirov and Dingwell 1996a,b; Spieler et al. 2003a), we have measured unsteady-state permeability at a high initial pressure differential. Following sudden decompression above the rock cylinder, pressurized gas flows through the sample. Two pressure transducers record the pressure signals above and below the sample. A transient 1D filtration code has been developed to calculate permeability using the experimental decay curve of the lower pressure transducer. Additionally an analytical steady-state method to achieve permeability is presented as an alternative to swiftly predict the sample permeability in a sufficiently precise manner. Over 100 permeability measurements have been performed on samples covering a wide range of porosity. The results show a general positive relationship between porosity and permeability with a high data scatter. Our preferred interpretation of the results is a combination of two different, but overlapping effects. We propose that at low porosities, gas escape occurs predominantly through microcracks or elongated micropores and therefore could be described by simplified forms of Kozeny–Carman relations (Carman 1956) and fracture flow models. At higher porosities, the influence of vesicles becomes progressively stronger as they form an increasingly connected network. Therefore, a model based on the percolation theory of fully penetrable spheres is used, as a first approximation, to describe the permeability-porosity trend. In the data acquired to date it is evident, that in addition to the porosity control, the samples bubble size, shape and distribution strongly influence the permeability. This leads to a range of permeability values up to 2.5 orders of magnitude at a given porosity.  相似文献   

Imaging of the Structure and Evolution of the Coma Morphology of Comet Hale–Bopp (C/1995 O1)     

Mueller  Béatrice E.A.  Samarasinha  Nalin H.  Belton  Michael J.S. 《Earth, Moon, and Planets》1997,77(3):181-188

Imaging of coma morphology of Comet Hale-Bopp from pre-perihelion through perihelion to post-perihelion is presented. Broad band images from 1996 and late 1997 show nearly radial jets streaking out from the nucleus. During both 1996 and late 1997, the brightest jets are approximately in a northern/northeastern direction. The slight curvature present in these radial jets is consistent with radiation pressure effects. Narrow band images around perihelion show two distinctive pictures of the CN and the continuum coma morphology. Spirals are clearly seen in the CN images but not in the continuum where structure is confined to the sunward side. The CN structure is consistent with continuous outgassing of the source of CN from the nucleus during both day and night. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

PROBLEMS IN THE DEFINITION AND MEASUREMENT OF STREAM LENGTH     

Jerry E. Mueller 《The Professional geographer》1979,31(3):306-311

Although stream length is a fundamental property of fluvially eroded landscapes, methods of obtaining this basic measure vary; therefore, data compiled from several sources are often not comparable. Not only are measurement methods inconsistent, but there is no standaid definition of stream length itself. Most measurements are taken directly from maps where accuracy may be questionable, and air photos have proven more reliable than topographic maps. Obtaining reliable stream-length data from published sources is perhaps the most perplexing problem of all. In investigations of stream length, therefore, it is imperative that data sources, measurement techniques, and methodology be clearly defined so that results may be studied in a meaningful context.  相似文献   

The cosmo-petrological significance of the coalescence of microchondrules with the decrease of volatiles in chondrites     

G. Mueller 《Astrophysics and Space Science》1969,4(1):3-43

The type I carbonaceous chondrites, with volatiles between 24 and 30% (at 1000 C, N₂ atm.), contain the maximum percentage of the low-temperature ground mass, in which the high-temperature minerals are dispersed as microchondrules. In the type II carbonaceous chondrites (vol. 12–24%), the loosely cohering aggregates of microchondrules, grape-bunch chondrules, reach a maximum. The type III carbonaceous chondrites and some enstatite chondrites (vol. 2–12%) contain the maximum of the partly coalesced chondrules, in which microchondrules of olivine and nickel-iron appear. The ureilites are interpreted as impact shocked aggregates of microchondrules in differing states of coalescence. The fully coalesced chondrules are characteristic for the ordinary chondrites with volatiles below 1%.It appears that the evolution of chondrules with the decrease of volatiles in meteorites subdivides into: (A) primary condensation of microchondrules with diameters of 0.01 mm; (B) secondary accretion of the former into the chondrules of diameter range ±1 mm.The observations may be explained through the hypothesis that at the highest-temperature stage of condensation of the asteroid-type parent body was an incandescent cloud (preserved through the solidification of chondrules at an early stage of degassing) covered with cosmic dust. The carbonaceous chondrites orginate from the marginal incandescent fog and the correspondingly deeper zones of the incandescent cloud mantle.The absence of typical chondritic rocks on earth may be explained by the slower cooling rate of this celestial body of relatively greater mass.  相似文献   

The European Large Area ISO Survey – VIII. 90-μm final analysis and source counts     

Ph. Héraudeau  S. Oliver  C. del Burgo  C. Kiss  M. Stickel  T. Mueller  M. Rowan-Robinson  A. Efstathiou  C. Surace  L. V. Tóth  S. Serjeant  D. M. Alexander  A. Franceschini  D. Lemke  T. Morel  I. Pérez-Fournon  J.-L. Puget  D. Rigopoulou  B. Rocca-Volmerange  A. Verma 《Monthly notices of the Royal Astronomical Society》2004,354(3):924-934

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