These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Incipient basin inversion of the Middle Archean Moodies Basin, Barberton Supergroup, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

The Moodies Group of the Barberton Greenstone Belt is one of the oldest and best-preserved quartz-rich sedimentary sequences on Earth. Its strata, approx. 3 km thick, record an initial extensional setting, followed by a strong shortening pulse which resulted in the dominant large-scale final deformation of the greenstone belt. We investigated the apparently rapid transition from Moodies extensional to compressive setting through detailed mapping, correlation of measured sections and the analysis of a prominent basaltic lava which extends for approx. 60 km along strike, in order to constrain the tectonic and depositional setting of some of the earliest stable life-providing habitats on Earth. In the middle Moodies Group, large-scale cross-bedded coarse-grained sandstones, interpreted as an offshore dune field, are abruptly overlain by a discontinuous cobble and boulder conglomerate of up to 4 m thickness, possibly representing local small alluvial fans above a cryptic disconformity. A basaltic lava, reaching approx. 50 m thick, regionally exists above this unit and forms the most prominent marker unit in the Moodies Group. In most places, the lava is metasomatically altered to a fine-grained mesh of illite, sericite, chlorite and very fine-grained quartz. In its upper third, it contains abundant amygdules approx. 0.5 - 1 cm in diameter. We did not record significant thickness changes hinting at eruption centers, feeder channels, flow markers nor pillows. Two thin but regionally continuous dacitic tuffs overlying the lava yielded concordant single-zircon ages of 3229+-6 Ma (Heubeck et al., in prep.) which are statistically indistinguishable from underlying Fig Tree Group volcanics and suggest high depositional and subsidence rates (mm/yr or higher) of intervening Moodies Group strata. Overlying clastic sediments up to 1 km thick show a very high lateral and vertical variability in grain size and petrography. Their facies ranges from alluvial conglomeratic wedges, fluvial gravelly sandstones, nearshore cross-bedded sandstones, tuffaceous shales to thin BIFs; sandstones show isolated occurrences of laminated curly biomats. The rapid facies changes attest to the termination of a uniform sedimentation regime and suggest the incipient breakup of the basin in numerous subbasins. The boulder conglomerate below the base of the basaltic lava likely represents the tectonic turning point in the evolution of the Moodies Basin by marking a pronounced increase in local depositional slope, the subsequent initiation of horizontal shortening, basin margin uplift and erosion, and final tight greenstone belt shortening. The eruption of the basaltic lava may be related to brittle segmentation of the basement, causing small-scale faulting, alluvial fan development on a former shelf, and allowing magma ascent.

Kirstein, Jens; Heubeck, Christoph; Lippold, Wigbert

2010-05-01

2

Sm-Nd dating of Fig Tree clay minerals of the Barberton greenstone belt, South Africa  

NASA Technical Reports Server (NTRS)

Sm-Nd isotopic data from carbonate-derived clay minerals of the 3.22-3.25 Ga Fig Tree Group, Barberton greenstone belt, South Africa, form a linear array corresponding to an age of 3102 +/- 64 Ma, making these minerals the oldest dated clays on Earth. The obtained age is 120-160 m.y. younger than the depositional age determined by zircon geochronology. Nd model ages for the clays range from approximately 3.39 to 3.44 Ga and almost cover the age variation of the Barberton greenstone belt rocks, consistent with independent evidence that the clay minerals are derived from material of the belt. The combined isotopic and mineralogical data provide evidence for a cryptic thermal overprint in the sediments of the belt. However, the highest temperature reached by the samples since the time of clay-mineral formation was <300 degrees C, lower than virtually any known early Archean supracrustal sequence.

Toulkeridis, T.; Goldstein, S. L.; Clauer, N.; Kroner, A.; Lowe, D. R.

1994-01-01

3

Accretionary history of the Archean Barberton Greenstone Belt (3.55-3.22 Ga), southern Africa  

NASA Technical Reports Server (NTRS)

The 3.55-3.22 Ga Barberton Greenstone Belt, South Africa and Swaziland, and surrounding coeval plutons can be divided into four tectono-stratigraphic blocks that become younger toward the northwest. Each block formed through early mafic to ultramafic volcanism (Onverwacht Group), probably in oceanic extensional, island, or plateau settings. Volcanism was followed by magmatic quiescence and deposition of fine-grained sediments, possibly in an intraplate setting. Late evolution involved underplating of the mafic crust by tonalitic intrusions along a subduction-related magmatic arc, yielding a thickened, buoyant protocontinental block. The growth of larger continental domains occurred both through magmatic accretion, as new protocontinental blocks developed along the margins of older blocks, and when previously separate blocks were amalgamated through tectonic accretion. Evolution of the Barberton Belt may reflect an Early Archean plate tectonic cycle that characterized a world with few or no large, stabilized blocks of sialic crust.

Lowe, D. R.

1994-01-01

4

Palaeomagnetism of Archaean rocks of the Onverwacht Group, Barberton Greenstone Belt (southern Africa): Evidence for a stable and potentially reversing geomagnetic  

E-print Network

Greenstone Belt (Kaapvaal Craton, southern Africa). Our palaeomagnetic measurements strengthen a recently) in the Kaapvaal Craton of southern Africa and the Pilbara Granite-Greenstone terrain in western Australia, bothPalaeomagnetism of Archaean rocks of the Onverwacht Group, Barberton Greenstone Belt (southern

Utrecht, Universiteit

5

Growth of early archaean crust in the ancient Gneiss complex of Swaziland and adjacent Barberton Greenstone Belt, Southern Africa  

NASA Technical Reports Server (NTRS)

The relationship between early Archean greenstones and high grade gneisses in the Ancient Gneiss Complex of Swaziland and the neighboring Barberton greenstone belt in Southern Africa is discussed. New high precision zircon analyses reveal a complex history in individual zircons from tonalitic orthogneisses, with ages as old as 3644 + 4 Ma. This suggests the presence of continental crust prior to the formation of the supracrustal rocks of the Barberton greenstone belt, which have been previously considered the earliest rocks in the area. The author suggested that these data are incompatible with the intraoceanic settings that have been widely accepted for this terrane, and favors either a marginal basin or rift environment. By using the detailed age information obtained from zircons in combination with Ar-40 and Ar-39 and paleomagnetic measurements, the author estimated that plate velocities for this part of Africa craton were about 10 to 70 mm/yr, during the period 3.4 to 2.5 Ga. This is not incompatible with the idea that Archean plate velocities may have been similiar to those of today.

Kroener, A.; Compston, W.; Tegtmeyer, A.; Milisenda, C.; Liew, T. C.

1988-01-01

6

Depositional and tectonic setting of the Archean Moodies Group, Barberton Greenstone Belt, South Africa  

NASA Technical Reports Server (NTRS)

The 3.22-3.10 Ga old Moodies Group, uppermost unit of the Swaziland Supergroup in the Barberton Greenstone Belt (BGB), is the oldest exposed, well-preserved quartz-rich sedimentary sequence on earth. It is preserved in structurally separate blocks in a heavily deformed fold-and-thrust belt. North of the Inyoka Fault, Moodies strata reach up to 3700 m in thickness. Detailed mapping, correlation of measured sections, and systematic analysis of paleocurrents show that the lower Moodies Group north of the Inyoka Fault forms a deepening- and fining-upward sequence from a basal alluvial conglomerate through braided fluvial, tidal, and deltaic sandstones to offshore sandy shelf deposits. The basal conglomerate and overlying fluvial facies were derived from the north and include abundant detritus eroded from underlying Fig Tree Group dacitic volcanic rocks. Shoreline-parallel transport and extensive reworking dominate overlying deltaic, tidal, and marine facies. The lithologies and arrangement of Moodies Group facies, sandstone petrology, the unconformable relationship between Moodies strata and older deformed rocks, presence of at least one syndepositional normal fault, and presence of basaltic flow rocks and airfall fall tuffs interbedded with the terrestrial strata collectively suggest that the lower Moodies Group was deposited in one or more intramontane basins in an extensional setting. Thinner Moodies sections south of the Inyoka Fault, generally less than 1000 m thick, may be correlative with the basal Moodies Group north of the Inyoka Fault and were probably deposited in separate basins. A northerly derived, southward-thinning fan-delta conglomerate in the upper part of the Moodies Group in the central BGB overlies lower strata with an angular unconformity. This and associated upper Moodies conglomerates mark the beginning of basin shortening by south- to southeast-directed thrust faulting along the northern margin of the BGB and suggest that the upper Moodies Group was deposited in a foreland basin. Timing, orientation, and style of shortening suggest that this deformation eventually incorporated most of the BGB into a major fold-and-thrust belt.

Heubeck, C.; Lowe, D. R.

1994-01-01

7

Depositional and tectonic setting of the Archean Moodies Group, Barberton Greenstone Belt, South Africa.  

PubMed

The 3.22-3.10 Ga old Moodies Group, uppermost unit of the Swaziland Supergroup in the Barberton Greenstone Belt (BGB), is the oldest exposed, well-preserved quartz-rich sedimentary sequence on earth. It is preserved in structurally separate blocks in a heavily deformed fold-and-thrust belt. North of the Inyoka Fault, Moodies strata reach up to 3700 m in thickness. Detailed mapping, correlation of measured sections, and systematic analysis of paleocurrents show that the lower Moodies Group north of the Inyoka Fault forms a deepening- and fining-upward sequence from a basal alluvial conglomerate through braided fluvial, tidal, and deltaic sandstones to offshore sandy shelf deposits. The basal conglomerate and overlying fluvial facies were derived from the north and include abundant detritus eroded from underlying Fig Tree Group dacitic volcanic rocks. Shoreline-parallel transport and extensive reworking dominate overlying deltaic, tidal, and marine facies. The lithologies and arrangement of Moodies Group facies, sandstone petrology, the unconformable relationship between Moodies strata and older deformed rocks, presence of at least one syndepositional normal fault, and presence of basaltic flow rocks and airfall fall tuffs interbedded with the terrestrial strata collectively suggest that the lower Moodies Group was deposited in one or more intramontane basins in an extensional setting. Thinner Moodies sections south of the Inyoka Fault, generally less than 1000 m thick, may be correlative with the basal Moodies Group north of the Inyoka Fault and were probably deposited in separate basins. A northerly derived, southward-thinning fan-delta conglomerate in the upper part of the Moodies Group in the central BGB overlies lower strata with an angular unconformity. This and associated upper Moodies conglomerates mark the beginning of basin shortening by south- to southeast-directed thrust faulting along the northern margin of the BGB and suggest that the upper Moodies Group was deposited in a foreland basin. Timing, orientation, and style of shortening suggest that this deformation eventually incorporated most of the BGB into a major fold-and-thrust belt. PMID:11539505

Heubeck, C; Lowe, D R

1994-01-01

8

Study of Carbonaceous Material in cherts from Barberton Greenstone Belt and the Astrobiological Implications.  

NASA Astrophysics Data System (ADS)

Carbonaceous matter is present in chert deposits of Barberton Greenstone Belt (BGB), South Africa. This is a famous place in the world for its Archean geology, wich represents around 3.5 billion years of earth's history. Therefore this area provides us the opportunity to study and understand an important part history of our planet, and also allow to compare with the geological history of other planets in our solar system [1]. Raman micro-spectroscopy has proved to be a very important and non-destructive powerful tool for distinguish micro-sized particles of C-polymorphs, as it is very sensitive to the nature of carbon bonding [2]. The connection between the Raman characterization of these carbonaceous phases with ancient biogenic activity it's of special interest. Cherts of BGB have been interpreted as precipitates or diagenetic replacements of preexisting sedimentary and pyroclastic deposits in a silica saturated Archean ocean [3]. Several layered Samples of cherts from BGB utility for the present study were collected during the expedition carried out in August 2010 sponsored by CNES and ESA. A detailed Raman spectral analysis of carbon C-C vibrations has been performed in the first (1200-1800 cm-1) and second (2500-3200 cm-1) order regions [4]. The results show important changes in the G-D bands in the layered structure of chert. Additionally a UPLC-ESI-QTOF-MS was carried out trying to introduce new insight in the Raman interpretation of the bands and in the possible assignments to particular molecular groups which could be related with biotic or abiotic origin of the carbonaceous material. Among the tentative compounds obtained from UPLC-ESI-QTOF-MS study it is worth to mention hydroxy-lycopene and the hydroxyl derivative of ?-carotene (i.e. ?-cryptoxanthin), which are carotenoids produced by cyanobacteria. These results are consistent with the presence of 22-Hopanol and Tetrahymanol, which are characteristic hopanoids of photosynthetic cyanobacteria and have been found in 2.7 billion year old rocks in Pilbara (Australia) [5]. The chromatographic behavior and exact mass coincidence of the m/z values found in this study give support, at least partially, the identification proposed.

Rull, F.; Venegas, G.; Montero, O.; Medina, J.

2012-04-01

9

Peering into the Cradle of Life: Scientific Drilling in the Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

The Barberton Greenstone Belt in South Africa is one of the best-preserved successions of mid-Archean (3.5-3.2 Ga) supracrustal rocks in the world, and a site where conditions and processes at the surface of the Archean Earth can be studied in detail. Despite generally good outcrop, complete field sections are not preserved, and crucial features such as the contacts of lava flows and continuous successions of critical sedimentary rock sequences are not exposed. Through diamond drilling we have obtained continuous sections and relatively unaltered samples from the volcano-sedimentary successions. The sedimentary sequences provide information about erosion and sedimentation on the early Earth, the composition and temperature of Archean seawater, and one possible site where life may have emerged and evolved. Investigation of spherule layers (including impact debris) provide information about the nature and magnitude of meteorite impact on the early Earth. The ultramafic to mafic volcanic rocks provide new insights into volcanic processes, dynamics of the crust and mantle, interaction between oceanic volcanic crust and the hydrosphere and biosphere. The project supported by the International Continental Drilling Program and by scientists from 13 countries in five continents. Drilling started in July 2011 and is expected to finish in February 2012. Regular updates are posted on the ICDP web site < www.icdp-online.org>. By December 2011, two 300m holes in komatiite had been completed. This drilling provided excellent sections through over 60 flows of komatiite or komatiitic basalt, including a thick inflated flow composed of highly magnesian, possibly hydrous komatiite. Drilling was continuing at two sites in sedimentary sequences. The first, at Buck Reef, has yielded over 600 m of banded chert retaining complex sedimentary and diagenetic structures; the second, in the Middle Fig Tree formation, has intersected 350 m of interbanded chert and ferruginous shale. Two additional hole will be completed by March 2012. The distribution of samples and post-drilling research will be coordinated by a steering committee from all member countries and a workshop to decide who does what on the core will be held in South Africa in mid 2012.

Arndt, N. T.; Barberton Drilling Team

2012-04-01

10

Single zircon dating constraining the maximum age of the barberton greenstone belt, Southern Africa  

Microsoft Academic Search

One of the central issues in early Precambrian crustal evolution is the age and genetic relationship between greenstone belt supracrustal assemblages and nearby high-grade gneiss terranes. The crucial question, in most cases, is which of the two is older. We report zircon ages, using the new single grain evaporation technique, from a metaquartzite and a felsic volcanic flow of the

Alfred Kröner; Wolfgang Todt

1988-01-01

11

Fluid inclusion analysis of chert veins from the Mendon Formation, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

Strongly silicified volcanic rocks and overlying sediments are a common feature in the Mesoarchean Barberton Greenstone Belt, South Africa. The silification predominantly occurs at the top of mafic to ultramafic lava flows at the contact to sedimentary chert horizons, and has been interpreted as a result of fluid circulation in shallow subseafloor convection cells (Hofmann & Harris, 2008). Six samples of silicified rocks of the Mendon Formation were used for a fluid inclusion study to better constrain the conditions of formation and the source and physico-chemical evolution of the fluid that might have been responsible for the alteration. The studied samples consist of silicified ultramafic rock and chemical precipitates with abundant chert and/or quartz veins. The silicified ultramafic rocks are mainly made up of quartz, Cr-muscovite and Cr-Spinell. Tourmaline and chlorite are locally present. Sedimentary cherts are nearly pure quartz with minor accessory minerals such as rutile and Fe-(hydr)oxides. Fluid inclusions are present in coarse-grained quartz in mainly bedding parallel syntaxial veins. Primary fluid inclusions occur as clusters in the crystal's core with an average size of 5-10 µm. They occur as two phase aqueous (liquid-vapour) inclusions at room temperature with a relatively constant vapour fraction (c.15-20 vol.%). Most fluid inclusions from veins crosscutting the silicified ultramafic rocks have a salinity between 0.5 and 11.0. wt.% NaCl equiv., one sample additionally contains inclusions with distinctly higher salinities (18 - 30 wt.% NaCl equiv.). Homogenization into the liquid phase occurs from 110°C to 210°C; with most values ranging between 150 and 180°C. The sample showing two distinct groups in salinity shows the lowest Th ranging from 110°C to 150°C. The sedimentary cherts show substantial differences i.e. the presence of a phase that prohibits freezing with a N-cooled freezing stage; probably CH4 or N2. Independent temperature estimates were derived from chlorite thermometry and illite cristallinity. Chlorite thermometry yielded temperatures of 250-350°C, whereas a Kübler index of < 0.25 ?°2? means the samples belong to the Epi-zone. Excluding the high salinity and sedimentary samples, the pressure during fluid inclusion entrapment is calculated at 1.6 - 2.4 kbar, corresponding to a depth of 5 - 8 km. These values argue against a shallow water deposition, yet could mean that the crystalline parts of the veins formed after burial during a later deformation or a late stage fluid infiltration event. However, if the veins formed at ca. 150 - 180°C during early seafloor alteration, the primary fluid inclusions may have also survived any subsequent thermal event.

Farber, Katja; Dziggel, Annika; Meyer, Franz M.

2013-04-01

12

Magnetotelluric measurements across the southern Barberton greenstone belt, South Africa: data improving strategies and 2-D inversion results  

NASA Astrophysics Data System (ADS)

Magnetotelluric (MT) measurements in areas with electromagnetic (EM) noise sources such as electric fences, power and railway lines pose severe challenges to the standard processing procedures. In order to significantly improve the data quality advanced filtering and processing techniques need to be applied. The presented 5-component MT data set from two field campaigns in 2009 and 2010 in the Barberton/Badplaas area, South Africa, was acquired within the framework of the German-South African geo-scientific research initiative Inkaba yeAfrica. Approximately 200 MT sites aligned along six profiles provide a good areal coverage of the southern part of the Barberton Greenstone Belt (BGB). Since it is one of the few remaining well-preserved geological formations from the Archean, it presents an ideal area to study the tectonic evolution and the role of plate tectonics on Early Earth. Comparing the electric properties, the surrounding high and low grade metamorphic rocks are characteristically resistive whereas mineralized shear zones are possible areas of higher electrical conductivity. Mapping their depth extension is a crucial step towards understanding the formation and the evolution of the BGB. Unfortunately, in the measurement area numerous noise sources were active, producing severe spikes and steps in the EM fields. These disturbances mainly affect long periods which are needed for resolving the deepest structures. The Remote Reference technique as well as two filtering techniques are applied to improve the data in different period ranges. Adjusting their parameters for each site is necessary to obtain the best possible results. The improved data set is used for two-dimensional inversion studies for the six profiles applying the RLM2DI algorithm by Rodi and Mackie (2001, implemented in WinGlink). In the models, areas with higher conductivity can be traced beneath known faults throughout the entire array along different profiles. Resistive zones seem to correlate well with plutonic intrusions.

Kutter, S.; Chen, X.; Weckmann, U.

2011-12-01

13

Characterization, provenance, and tectonic setting of Fig Tree greywackes from the Archaean Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

In this study, mineralogical and geochemical data, as well as Sr and Nd isotopic compositions of early Archaean greywackes from the Fig Tree Group are presented to provide further information about the evolution of the Barberton Greenstone Belt (BGB) of the Kaapvaal Craton, South Africa. The chemical data on the collected greywackes from the BGB suggest limited chemical modification of the source rocks. The Eu/Eu * anomaly is negative with an average value of 0.76 which is slightly higher than that of Eu-depleted crustal rocks (0.65). High Cr and Ni concentrations and a Cr/Ni ratio of about 1.6 indicate derivation from ultramafic sources without fractionation. Although rounded zircons occur, the combination of CIW/CIA (Chemical Index of Weathering/Chemical Index of Alteration) values and Eu/Eu * ratios suggests little transportation until final deposition, whereas the juvenile crustal material comes from local sources. The siliciclastic material seems to be of mixed felsic and mafic-to-ultramafic origin. The tectonic setting of the source areas appears to reflect a continental island arc of Andean type, supporting the existence of an active plate-tectonic geodynamic system in early Archaean time. Sr isotopic data indicate an alteration during a post-depositional event, most probably at 2.6-2.7 Ga, which disturbed the Sr isotopic system. The Sm-Nd isotopic system must also have been altered since deposition of the rocks, as suggested by ?Nd values both lower and higher than expected. The calculated depleted-mantle model ages of 3.0 to 3.8 Ga are in the range of BGB sedimentary rocks. The higher model ages appear to reflect the underlying belt, which is represented by the Onverwacht Group and the surrounding intrusives, as being the major source of the greywackes.

Toulkeridis, Theofilos; Clauer, Norbert; Kröner, Alfred; Reimer, Thomas; Todt, Wolfgang

1999-03-01

14

The rheological behavior of fracture-filling cherts: example of Barite Valley dikes, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

A 100 m-thick complex of near-vertical carbonaceous chert dikes marks the transition from the Mendon to Mapepe Formations (3260 Ma) in the Barberton Greenstone Belt, South Africa. Fracturing was intense in this area, as shown by the profusion and width of the dikes (ca. 1 m on average) and by the abundance of completely shattered rocks. The dike-and-sill organization of the fracture network and the upward narrowing of some of the large veins indicate that at least part of the fluid originated at depth and migrated upward in this hydrothermal plumbing system. Abundant angular fragments of silicified country rock are suspended and uniformly distributed within the larger dikes. Jigsaw-fit structures and confined bursting textures indicate that hydraulic fracturing was at the origin of the veins. The confinement of the dike system beneath an impact spherule bed suggests that the hydrothermal circulations were triggered by the impact and located at the external margin of a large crater. From the geometry of the dikes and the petrography of the cherts, we infer that the fluid that invaded the fractures was thixotropic. On one hand, the injection of black chert into extremely fine fractures is evidence for low viscosity at the time of injection; on the other hand, the lack of closure of larger veins and the suspension of large fragments in a chert matrix provide evidence of high viscosity soon thereafter. The inference is that the viscosity of the injected fluid increased from low to high as the fluid velocity decreased. Such rheological behavior is characteristic of media composed of solid and colloidal particles suspended in a liquid. The presence of abundant clay-sized, rounded particles of silica, carbonaceous matter and clay minerals, the high proportion of siliceous matrix and the capacity of colloidal silica to form cohesive 3-D networks through gelation, account for the viscosity increase and thixotropic behavior of the fluid that filled the veins. Stirring and shearing of the siliceous mush as it was injected imparted a low viscosity by decreasing internal particle interactions; then, as the flow rate declined, the fluid became highly viscous as the inter-particulate bonds (siloxane bonds, Si-O-Si) were reconstituted. The gelation of the chert was rapid and the structure persisted at low temperature (T < 200 °C) before fractures were sealed and chert indurated.

Ledevin, M.; Arndt, N.; Simionovici, A.

2014-05-01

15

Exceptional preservation of aragonite in a circa 3.3 billion year old microbial mat from the Barberton greenstone belt, South Africa  

NASA Astrophysics Data System (ADS)

Exceptional preservation of aragonite in a circa 3.3 billion year old microbial mat from the Barberton greenstone belt, South Africa Frances Westall, Barbara Cavalazzi, Laurence Lemelle, Yves Marrocchi, Jean-Noël Rouzaud, Alexandre Simionovici, Murielle Salomé, Smail Mostefaoui, Caroline Andreazza, Frédéric Foucher, Jan Toporski, Andrea Jauss, Volker Thiel, Axel Hofmann, Anders Meibom, François Robert Aragonite occurs as a biologically-formed mineral precipitate within modern calcifying microbial mats. It is, however, rarely preserved in the geological record because, as one of the least stable polymorphs of calcium carbonate, it readily converts to calcite in present environmental conditions at the Earth's surface. In an in situ investigation at the micro- to nanometer-scale, we show that 5-10 nm sized nanocrystals of aragonite are preserved within the organic framework of a partially calcified microbial mat from the ~ 3.3 billion year-old Josefsdal Chert in the Barberton greenstone belt, South Africa. Transformation of the aragonite to calcite was blocked by a combination of chemical inhibitors within the crystal lattice, organic molecules coating the nanocrystals and, in particular, to the precocious permeation of the mat by hydrothermal silica. Apart from its exceptional preservation for 3.3 billion years, the identification of aragonite in the Josefsdal microbial mat is the earliest evidence for in situ calcification of a microbial mat. Furthermore, the indications of associated sulphur-reducing bacteria (SRB) activity with calcification strongly support a photosynthetic origin for the mat. This is the most direct evidence for photosynthesis in early Archaean rocks.

Westall, Frances; Cavalazzi, Barbara; Lemelle, Laurence; Marrochhi, Yves; Rouzaud, Jean-Noel; Simionovici, Alexandre; Andreazza, Caroline; Foucher, Frédéric; Thiel, Volker; Hofmann, Axel

2010-05-01

16

REE geochemistry of 3.2 Ga BIF from the Mapepe Formation, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

Banded iron formations (BIFs) are chemical sediments interbedded with Fe- and Si-rich layers, characteristically present in the early history of the Earth. A popular hypothesis for the formation of BIFs postulates that dissolved oxygen produced by photosynthesizers such as cyanobacteria oxidized dissolved ferrous Fe supplied by submarine hydrothermal activities. During precipitation of Fe-oxide minerals, phosphorus and rare earth elements (REEs) were most likely adsorbed on their surface. Therefore, chemical compositions of REEs that adsorbed onto Fe-oxide have useful information on the seawater chemistry at the time of deposition. Especially, information on the redox state of seawater and the extent of the contribution of hydrothermal activity during BIF deposition are expected to have been recorded. Occurrence of BIF has been traditionally tied to the chemical evolution of the atmosphere. Rise of atmospheric oxygen, or as known as GOE (Great Oxidation Event: e.g., Holland, 1994), has been widely believed to have occurred at around 2.4 Ga ago. Contrary, however, some studies have suggested that such oxygenation could have occurred much earlier (e.g., Hoashi et al., 2009). In this study, we used 3.2 Ga old BIF from the Mapepe Formation at the bottom of the Fig Tree Group of the Swaziland Supergroup in the northeastern part of the Barberton Greenstone Belt, South Africa. We aimed to constrain the marine environment, and by inference atmospheric environment, at the time of BIF deposition from REE geochemistry. Major elements and REE compositions of 37 samples were measured using XRF and ICP-MS, respectively. Samples with less than 1.0 wt% Al2O3 are considered to be "pure" BIFs with minimal amount of continental contamination, and are expected to have inherited marine REE signatures. Abundance of REE normalized by C1 chondrite for the analyzed samples commonly exhibits positive Eu anomaly and LREE

Yahagi, T. R.; Yamaguchi, K. E.; Haraguchi, S.; Sano, R.; Teraji, S.; Kiyokawa, S.; Ikehara, M.; Ito, T.

2012-12-01

17

Origin and mechanisms of K–Si-metasomatism of ca. 3.4–3.3 Ga volcaniclastic deposits and implications for Archean seawater evolution: Examples from cherts of Kittys Gap (Pilbara craton, Australia) and Msauli (Barberton Greenstone Belt, South Africa)  

Microsoft Academic Search

The effects of K–Si-metasomatism during the formation of Early Archean replacement cherts have been quantified in this study by the investigation of two well-known stratigraphic sections: the Msauli chert (MC, Barberton greenstone belt, South Africa) and the Kittys Gap chert (KGC, Pilbara craton, Western Australia). The KGCs have a dacitic precursor similar to Duffer Formation dacites (Pilbara craton), while the

Virgile Rouchon; Beate Orberger

2008-01-01

18

Inferred Primary Compositions of Archean Spherules Formed by the Condensation of an Impact-produced Rock Vapor Cloud, Barberton Greenstone Belt, South Africa  

NASA Technical Reports Server (NTRS)

Based on the lunar cratering record, impacts were larger and more frequent on the early Earth than they are today. There is no persevered record of these early terrestrial impacts because rocks of this age have been obliterated by tectonism and erosion. The oldest known evidence of impacts on Earth lies in four beds (S1, S2, S3 and S4) in the Barberton Greenstone Belt (BGB), South Africa, ranging in age from about 3.24 to 3.47 Ga. These beds are composed in large part of sand-sized spherical particles, termed spherules, that are thought to have formed by the condensation of rock vapor clouds ejected above the atmosphere as a result of large impacts. Spherule beds S2 and S3 are both about 20 cm thick where composed entirely of fall-deposited spherules and up to a meter thick where spherules are mixed with locally derived debris. The diameters the bolides have been estimated to be between 20 and 50 km, based on bed thickness, size of the largest spherules, Ir fluence and extraterrestrial Cr.

Krull, A. E.; Lowe, D. R.; Byerly, G. R.

2003-01-01

19

Physics of crustal fracturing and chert dike formation triggered by asteroid impact, ˜3.26 Ga, Barberton greenstone belt, South Africa  

NASA Astrophysics Data System (ADS)

asteroid impacts, reflected in the presence of spherule beds in the 3.2-3.5 Ga Barberton greenstone belt (BGB), South Africa, generated extreme seismic waves. Spherule bed S2 provides a field example. It locally lies at the contact between the Onverwacht and Fig Tree Groups in the BGB, which formed as a result of the impact of asteroid (possibly 50 km diameter). Scaling calculations indicate that very strong seismic waves traveled several crater diameters from the impact site, where they widely damaged Onverwacht rocks over much of the BGB. Lithified sediments near the top of the Onverwacht Group failed with opening-mode fractures. The underlying volcanic sequence then failed with normal faults and opening-mode fractures. Surficial unlithified sediments liquefied and behaved as a fluid. These liquefied sediments and some impact-produced spherules-filled near-surface fractures, today represented by swarms of chert dikes. Strong impact-related tsunamis then swept the seafloor. P waves and Rayleigh waves from the impact greatly exceeded the amplitudes of typical earthquake waves. The duration of extreme shaking was also far longer, probably hundreds of seconds, than that from strong earthquakes. Dynamic strains of ˜10-3 occurred from the surface and downward throughout the lithosphere. Shaking weakened the Onverwacht volcanic edifice and the surface layers locally moved downhill from gravity accommodated by faults and open-mode fractures. Coast-parallel opening-mode fractures on the fore-arc coast of Chile, formed as a result of megathrust events, are the closest modern analogs. It is even conceivable that dynamic stresses throughout the lithosphere initiated subduction beneath the Onverwacht rocks.

Sleep, Norman H.; Lowe, Donald R.

2014-04-01

20

Implications of in situ calcification for photosynthesis in a ~ 3.3 Ga-old microbial biofilm from the Barberton greenstone belt, South Africa  

NASA Astrophysics Data System (ADS)

Timing the appearance of photosynthetic microorganisms is crucial to understanding the evolution of life on Earth. The ability of the biosphere to use sunlight as a source of energy (photoautotrophy) would have been essential for increasing biomass and for increasing the biogeochemical capacity of all prokaryotes across the range of redox reactions that support life. Typical proxies for photosynthesis in the rock record include features, such as a mat-like, laminated morphology (stratiform, domical, conical) often associated with bulk geochemical signatures, such as calcification, and a fractionated carbon isotope signature. However, to date, in situ, calcification related to photosynthesis has not been demonstrated in the oldest known microbial mats. We here use in situ nanometre-scale techniques to investigate the structural and compositional architecture in a 3.3 billion-year (Ga) old microbial biofilm from the Barberton greenstone belt, thus documenting in situ calcification that was most likely related to anoxygenic photosynthesis. The Josefsdal Chert Microbial Biofilm (JCMB) formed in a littoral (photic) environment. It is characterised by a distinct vertical structural and compositional organisation. The lower part is calcified in situ by aragonite, progressing upwards into uncalcified kerogen characterised by up to 1% sulphur, followed by an upper layer that contains intact filaments at the surface. Crystallites of pseudomorphed pyrite are also associated with the biofilm suggesting calcification related to the activity of heterotrophic sulphur reducing bacteria. In this anoxygenic, nutrient-limited environment, the carbon required by the sulphur reducing bacteria could only have been produced by photoautotrophy. We conclude that the Josfsdal Chert Microbial Biofilm was formed by a consortium of anoxygenic microorganisms, including photosynthesisers and sulphur reducing bacteria.

Westall, Frances; Cavalazzi, Barbara; Lemelle, Laurence; Marrocchi, Yves; Rouzaud, Jean-Noël; Simionovici, Alexandre; Salomé, Murielle; Mostefaoui, Smail; Andreazza, Caroline; Foucher, Frédéric; Toporski, Jan; Jauss, Andrea; Thiel, Volker; Southam, Gordon; MacLean, Lachlan; Wirick, Susan; Hofmann, Axel; Meibom, Anders; Robert, François; Défarge, Christian

2011-10-01

21

High Resolution Tephra and U/Pb Chronology of the 3.33-3.26 Ga Mendon Formation, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

Stratigraphic and geologic interpretations of komatiitic flows and tuffs in the Barberton greenstone belt (BGB) are complicated by structural complexity, facies changes, and temporal repetition of lithofacies. Here we describe new data on the compositions of flows and tuffs and U/Pb ages that correlate existing and proposed new members of the Mendon Formation across the BGB. The Mendon Formation includes from 300 to >1000 m of komatiite, komatiitic tuff, and carbonaceous-to-ferruginous chert that represent the uppermost Onverwacht Group south of the Inyoka Fault. Our new data confirm that the Weltevreden Formation, the uppermost Onverwacht Group north of the Inyoka Fault, is correlative with the upper members of the Mendon Formation. The conformably overlying Fig Tree Group is composed largely of lithic sandstones and dacitic volcaniclastic rocks likely representing uplift and volcanism within a magmatic arc. Thus the Onverwacht to Fig Tree Group transition may represent a profound change from plume to plate tectonics. Recent studies have also demonstrated the importance of large asteroidal impacts near the Onverwacht-Fig Tree contact, two in the Mendon Formation and two in the lower Fig Tree Group spanning a 50 myr interval, suggesting a possible link between impacts and this tectonic transition. The compositional change from komatiitic to dacitic ash is moderately abrupt and near the S2 impact layer. However, at least five felsic ash layers are recognized in the Mendon Formation, and several komatiitic ash layers occur above S2 in the lowest Fig Tree Group. A preliminary compilation of the new data with that of previous studies suggests: 1) the Mendon Formation has an extreme diversity of primary komatiitic compositions, but also includes thin felsic ash layers, 2) no komatiitic flows have been identified in the Fig Tree Group but several komatiitic ash layers occur associated with spherule bed S2, 3) major faults in the south-central BGB isolate sections of the Mendon Formation with correlative komatiitic compositions, but remarkably different thicknesses, and 4) there are at least four impact layers in this short interval.

Decker, N. B.; Stefurak, E. J.; Thompson, M. E.; Lowe, D. R.; Byerly, G. R.

2012-12-01

22

Palaeomagnetism of Archaean rocks of the Onverwacht Group, Barberton Greenstone Belt (southern Africa): Evidence for a stable and potentially reversing geomagnetic field at ca. 3.5 Ga  

NASA Astrophysics Data System (ADS)

Palaeomagnetic data from the Palaeoarchaean Era (3.2-3.6 Ga) have the potential to provide us with a great deal of information about early conditions within, and processes affecting, the Earth's core, mantle, and surface environment. Here we present new data obtained from some of the oldest palaeomagnetic recorders in the world: igneous and sedimentary rocks from the Onverwacht Group of the Barberton Greenstone Belt (Kaapvaal Craton, southern Africa). Our palaeomagnetic measurements strengthen a recently published positive conglomerate test (Y. Usui, J.A. Tarduno, M. Watkeys, A. Hofmann and R.D. Cottrell, 2009) and our new U-Pb date constrains the conglomerate to older than 3455 ± 8 Ma. The new palaeomagnetic data from other units are nontrivial to interpret and are of uncertain reliability when taken individually; similar, we argue, to all other published palaeomagnetic data of this age. Nonetheless, four poles (two new, two derived from published data) produced from high temperature components of magnetisation recorded in the Komati, Noisy, and Hooggenoeg formations exhibit considerably improved clustering when their directions are corrected for differences in attitude resulting from a large fold structure dated at 3.23 Ga. On the basis of this enhanced consistency in stratigraphic coordinates, the positive conglomerate test, and the absence of any clear indications of their remagnetisation from comparison with younger poles, we argue that these are the most trustworthy palaeomagnetic results yet produced from any rocks of Palaeoarchaean age. When taken in conjunction with published data, the new results present the most compelling evidence to date that the Earth had a stable geomagnetic field at ca. 3.5 Ga in addition to presenting tentative evidence that it was undergoing polarity reversals. The data do not appear to support a claim, made previously from Palaeoarchean palaeomagnetic data from the Pilbara Craton (Y. Suganuma, Y. Hamano, S. Niitsuma, M. Hoashi, T. Hisamitsu, N. Niitsuma, K. Kodama and M. Nedachi, 2006), of extremely rapid latitudinal plate motion during this period. Finally, when compared with similarly aged data from the Pilbara Craton (Western Australia), the new data do not rule out the hypothesis that the two cratons were conjoined at this point in their history in the supercraton Vaalbara.

Biggin, Andrew J.; de Wit, Maarten J.; Langereis, Cor G.; Zegers, Tanja E.; Voûte, Sara; Dekkers, Mark J.; Drost, Kerstin

2011-02-01

23

Sulfur isotope mass-independent fractionation in impact deposits of the 3.2 billion-year-old Mapepe Formation, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

Theoretical and experimental studies have shown that atmospheric SO2 isotopologue self-shielding effects in the 190-220 nm region of the solar spectrum are the likely cause for mass independent fractionation of sulfur isotopes (S-MIF). The main products of this photochemical reaction - SO3 and S0 - typically define a compositional array of ca. ?33S/?34S = 0.06-0.14. This is at odds with the generally observed trend in Archean sulfides, which broadly defines an array of ca. ?33S/?34S = 0.9. Various explanations have been proposed, including a diminution of ?34S caused by chemical and biogenic mass-dependent fractionation of sulfur isotopes (S-MDF), mixing with photolytic products produced during felsic volcanic events, or partial blocking of the low-wavelength part of the spectrum due to the presence of reduced atmospheric gases or an organic haze. Early in Earth history large meteorite impacts would have ejected dust and gas clouds into the atmosphere that shielded solar radiation and affected global climate. It is thus likely that at certain time intervals of high meteorite flux the atmosphere was significantly perturbed, having an effect on atmospheric photochemistry and possibly leaving anomalous sulfur isotopic signatures in the rock record. Here we describe the sulfur isotopic signatures in sulfides of spherule beds S2, S3 and S4 of the Barberton Greenstone Belt, South Africa. In particular, in spherule bed S3 - and to a lesser extent S4 - a trend of ca. ?33S/?34S = 0.23 is observed that closely follows the expected trend for SO2-photolysis in the 190-220 nm spectral range. This suggests that an impact dust cloud (deposited as spherule beds), which sampled the higher region of the atmosphere, specifically incorporated products of SO2 photolysis in the 190-220 nm range, and blocked photochemical reactions at higher wavelengths (250-330 nm band). By implication, the generally observed Archean trend appears to be the result of mixing of different MIF-S sources arising from a variety of photochemical reactions that took place in the lower part of the atmosphere.

van Zuilen, M. A.; Philippot, P.; Whitehouse, M. J.; Lepland, A.

2014-10-01

24

Carbonaceous matter and putative microfossils of the mid-Archean Kromberg type-section re-visited, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

Silicified seafloor sediments of the Kromberg Formation from the Onverwacht Group of the Barberton greenstone belt (BGB), South Africa, have been argued to contain some of the world's oldest preserved carbonaceous microfossils. Previous studies of these cherts have reported filamentous, spheroidal and ellipsoidal microfossils in thin-section (Walsh 1992); and bacteriomorph like structures in HF-etched samples (Westall et al. 2001). These microtextural studies however, lack supporting in-situ geochemical data, and are hampered to some degree by re-mobilisation of the carbonaceous matter (Van Zuilen et al. 2007). In light of these concerns, and ongoing debates surrounding carbonaceous remains in other Archean cherts (e.g., W Australia), further in-situ data from the Kromberg is required to positively identify carbonaceous matter of biogenic origin. New data will also help to address outstanding questions regarding the relative contribution of benthic versus planktonic microorganisms, and the putative microbial metabolisms involved. This study focuses on surface samples and drill core from the Barberton Scientific Drilling Programme, (BSDP, Grosch et al. 2009) from the southeastern limb of the Onverwacht anticline of the BGB. We sampled the Footbridge chert and a second chert horizon in drill core KD1 of the BSDP in the upper Kromberg Fm; and surface outcrops of two black cherts from the lower Kromberg Fm. Sedimentological logging reveals horizons rich in volcaniclastics with interbedded finely laminated grey-black chert, also intrusive black cherts, and sulphide rich horizons. The TOC of the sampled cherts is 1.24 to 5.40 wt%. Preliminary bulk carbon isotope values range from ?13C -21.1 to -35.3o values that are consistent with organic matter produced by anoxygenic photosynthesis. Microfabrics preserved in the Kromberg cherts include, primary wispy-laminated carbonaceous films suggesting compaction of early carbonaceous laminae. Also large composite carbonaceous grains >30 ?m across recording wave-motion on the seafloor. Secondary fabrics include hydrothermal veins containing remobilized carbon and sometimes sulphides, also void-filling silica spherulites coated in carbonaceous matter. A novel fabric discovered in the lower Kromberg chert is silicified carbonaceous fragments with plastic deformation that are morphologically comparable to microtextures reported from the 3.416 Ga Buck Reef Chert (Tice and Lowe 2004) interpreted to be deformed microbial mat fragments. These fabrics are currently being studied by raman spectroscopy to assess the effects of taphonomic processes and metamorphic alteration on this potential biosignature. In-situ sulphur isotope measurements by SIMS on sulphides associated with primary carbonaceous fabrics of the Footbridge chert found a narrow range in ?34SCDTvalues of -6.00 to + 1.50 o and positive ?33S values up to +2.50 o suggesting the involvement of atmospheric sulphur aerosols, but do not strongly support either microbial sulphate reduction or disproportionation (Grosch and McLoughlin 2013). The geochemical evidence for microbial processes must therefore be further tested in the Kromberg cherts to build upon the bulk carbon isotope data that is consistent with, but alone not diagnostic of, microbial processes. In summary, this new survey of carbonaceous cherts from the Kromberg type section has identified well-preserved candidate microbial microfabrics that will be the target of ongoing high resolution in-situ geochemical and ultrastructure analysis.

McLoughlin, Nicola; Grosch, Eugene

2014-05-01

25

Spherule Beds 3.47-3.24 Billion Years Old in the Barberton Greenstone Belt, South Africa: A Record of Large Meteorite Impacts and Their Influence on Early Crustal and Biological Evolution  

NASA Technical Reports Server (NTRS)

Four layers, S1-S4, containing sand-sized spherical particles formed as a result of large meteorite impacts, occur in 3.47-3.24 Ga rocks of the Barberton Greenstone Belt, South Africa. Ir levels in S3 and S4 locally equal or exceed chondritic values but in other sections are at or only slightly above background. Most spherules are inferred to have formed by condensation of impact-produced rock vapor clouds, although some may represent ballistically ejected liquid droplets. Extreme Ir abundances and heterogeneity may reflect element fractionation during spherule formation, hydraulic fractionation during deposition, and/or diagenetic and metasomatic processes. Deposition of S1, S2, and S3 was widely influenced by waves and/or currents interpreted to represent impact-generated tsunamis, and S1 and S2 show multiple graded layers indicating the passage of two or more wave trains. These tsunamis may have promoted mixing within a globally stratified ocean, enriching surface waters in nutrients for biological communities. S2 and S3 mark the transition from the 300-million-year-long Onverwacht stage of predominantly basaltic and komatiitic volcanism to the late orogenic stage of greenstone belt evolution, suggesting that regional and possibly global tectonic reorganization resulted from these large impacts. These beds provide the oldest known direct record of terrestrial impacts and an opportunity to explore their influence on early life, crust, ocean, and atmosphere. The apparent presence of impact clusters at 3.26-3.24 Ga and approx. 2.65-2.5 Ga suggests either spikes in impact rates during the Archean or that the entire Archean was characterized by terrestrial impact rates above those currently estimated from the lunar cratering record.

Lowe, Donald R.; Byerly, Gary R.; Kyte, Frank T.; Shukolyukov, Alexander; Asaro, Frank; Krull, Alexander

2003-01-01

26

Spherule beds 3.47-3.24 billion years old in the Barberton Greenstone Belt, South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution.  

PubMed

Four layers, S1-S4, containing sand-sized spherical particles formed as a result of large meteorite impacts, occur in 3.47-3.24 Ga rocks of the Barberton Greenstone Belt, South Africa. Ir levels in S3 and S4 locally equal or exceed chondritic values but in other sections are at or only slightly above background. Most spherules are inferred to have formed by condensation of impact-produced rock vapor clouds, although some may represent ballistically ejected liquid droplets. Extreme Ir abundances and heterogeneity may reflect element fractionation during spherule formation, hydraulic fractionation during deposition, and/or diagenetic and metasomatic processes. Deposition of S1, S2, and S3 was widely influenced by waves and/or currents interpreted to represent impact-generated tsunamis, and S1 and S2 show multiple graded layers indicating the passage of two or more wave trains. These tsunamis may have promoted mixing within a globally stratified ocean, enriching surface waters in nutrients for biological communities. S2 and S3 mark the transition from the 300-million-year-long Onverwacht stage of predominantly basaltic and komatiitic volcanism to the late orogenic stage of greenstone belt evolution, suggesting that regional and possibly global tectonic reorganization resulted from these large impacts. These beds provide the oldest known direct record of terrestrial impacts and an opportunity to explore their influence on early life, crust, ocean, and atmosphere. The apparent presence of impact clusters at 3.26-3.24 Ga and approximately 2.65-2.5 Ga suggests either spikes in impact rates during the Archean or that the entire Archean was characterized by terrestrial impact rates above those currently estimated from the lunar cratering record. PMID:12804363

Lowe, Donald R; Byerly, Gary R; Kyte, Frank T; Shukolyukov, Alexander; Asaro, Frank; Krull, Alexandra

2003-01-01

27

Implications of a 3.472-3.333 Gyr-old subaerial microbial mat from the Barberton greenstone belt, South Africa for the UV environmental conditions on the early Earth  

PubMed Central

Modelling suggests that the UV radiation environment of the early Earth, with DNA weighted irradiances of about three orders of magnitude greater than those at present, was hostile to life forms at the surface, unless they lived in specific protected habitats. However, we present empirical evidence that challenges this commonly held view. We describe a well-developed microbial mat that formed on the surface of volcanic littoral sediments in an evaporitic environment in a 3.5–3.3?Ga-old formation from the Barberton greenstone belt. Using a multiscale, multidisciplinary approach designed to strongly test the biogenicity of potential microbial structures, we show that the mat was constructed under flowing water by 0.25??m filaments that produced copious quantities of extracellular polymeric substances, representing probably anoxygenic photosynthesizers. Associated with the mat is a small colony of rods–vibroids that probably represent sulphur-reducing bacteria. An embedded suite of evaporite minerals and desiccation cracks in the surface of the mat demonstrates that it was periodically exposed to the air in an evaporitic environment. We conclude that DNA-damaging UV radiation fluxes at the surface of the Earth at this period must either have been low (absorbed by CO2, H2O, a thin organic haze from photo-dissociated CH4, or SO2 from volcanic outgassing; scattered by volcanic, and periodically, meteorite dust, as well as by the upper layers of the microbial mat) and/or that the micro-organisms exhibited efficient gene repair/survival strategies. PMID:17008224

Westall, Frances; de Ronde, Cornel E.J; Southam, Gordon; Grassineau, Nathalie; Colas, Maggy; Cockell, Charles; Lammer, Helmut

2006-01-01

28

Chronology of early Archaean granite-greenstone evolution in the Barberton Mountain Land, South Africa, based on precise dating by single zircon evaporation  

NASA Technical Reports Server (NTRS)

Precise Pb-207/Pb-206 single zircon evaporating ages are reported for low-grade felsic metavolcanic rocks within the Onverwacht and Fig Tree Groups of the Barberton Greenstone Belt (BGB), South Africa, as well as for granitoid plutons bordering the belt. Dacitic tuffs of the Hooggenoeg Formation in the upper part of the Onverwacht Group are shown to yield ages between 3445 + or - 3 and 3416 + or - 5 Ma and to contain older crustal components represented by a 3504 + or - 4 Ma old zircon xenocryst. Fig Tree dacitic tuffs and agglomerates have euhedral zircons between 3259 + or - 3 Ma in age which are interpreted to reflect the time of crystallization. The comagmatic relationships between greenstone felsic volcanic units and the surrounding plutonic suites are keynoted. The data adduced show that the Onverwacht and Fig Tree felsic units have distinctly different ages and thus do not constitute a single, tectonically repeated unit as proposed by others. It is argued that conventional multigrain zircon dating may not accurately identify the time of felsic volcanic activity in ancient greenstones, and that the BGB in the Kaapval craton of southern Africa and greenstones in the Pilbara Block of Western Australia may have been part of a larger crustal unit in early Archaean times.

Kruener, Alfred; Byerly, Gary R.; Lowe, Donald R.

1991-01-01

29

Chronology of early Archaean granite-greenstone evolution in the Barberton Mountain Land, South Africa, based on precise dating by single zircon evaporation.  

PubMed

We report precise 207Pb/206Pb single zircon evaporation ages for low-grade felsic metavolcanic rocks within the Onverwacht and Fig Tree Groups of the Barberton Greenstone Belt (BGB), South Africa, and from granitoid plutons bordering the belt. Dacitic tuffs of the Hooggenoeg Formation in the upper part of the Onverwacht Group yield ages between 3445 +/- 3 and 3416 +/- 5 Ma and contain older crustal components represented by a 3504 +/- 4 Ma old zircon xenocryst. Fig Tree dacitic tuffs and agglomerates have euhedral zircons between 3259 +/- 5 and 3225 +/- 3 Ma in age which we interpret to reflect the time of crystallization. A surprisingly complex xenocryst population in one sample documents ages from 3323 +/- 4 to 3522 +/- 4 Ma. We suspect that these xenocrysts were inherited, during the passage of the felsic melts to the surface, from various sources such as greenstones and granitoid rocks now exposed in the form of tonalite-trondhjemite plutons along the southern and western margins of the BGB, and units predating any of the exposed greenstone or intrusive rocks. Several of the granitoids along the southern margin of the belt have zircon populations with ages between 3490 and 3440 Ma. coeval with or slightly older than Onverwacht felsic volcanism, while the Kaap Valley pluton along the northwestern margin of the belt is coeval with Fig Tree dacitic volcanism. These results emphasize the comagmatic relationships between greenstone felsic volcanic units and the surrounding plutonic suites. Some of the volcanic plutonic units contain zircon xenocrysts older than any exposed rocks. These indicate the existence of still older units, possibly stratigraphically lower and older portions of the greenstone sequence itself, older granitoid intrusive rocks, or bodies of older, unrelated crustal material. Our data show that the Onverwacht and Fig Tree felsic units have distinctly different ages and therefore do not represent a single, tectonically repeated unit as proposed by others. Unlike the late Archaean Abitibi greenstone belt in Canada, which formed over about 30 Ma. exposed rocks in the BGB formed over a period of at least 220 Ma. The complex zircon populations encountered in this study imply that conventional multigrain zircon dating may not accurately identify the time of felsic volcanic activity in ancient greenstones. A surprising similarity in rock types, tectonic evolution, and ages of the BGB in the Kaapvaal craton of southern Africa and greenstones in the Pilbara Block of Western Australia suggests that these two terrains may have been part of a larger crustal unit in early Archaean times. PMID:11538384

Krüner, A; Byerly, G R; Lowe, D R

1991-04-01

30

Petrography, PGE Contents and Os Isotope Systematics of Barberton CT3 Spherule Layers  

NASA Astrophysics Data System (ADS)

We focus on some spherule layers from the northeastern part of the Barberton Greenstone Belt, South Africa and aim to determine their diagenetic-metamorphic history and to assess their possible impact origin by petrographic and geochemical analyses.

Ozdemir, S.; Schulz, T.; Koeberl, C.; Reimold, W. U.; Mohr-Westheide, T.

2014-09-01

31

Archaean greenstone belts and associated granitic rocks - A review  

NASA Astrophysics Data System (ADS)

Archaean greenstone belts and associated granitic rocks comprise some of the most diverse rock types on the Earth's surface and were formed during the early stages of the development of the planet from Eoarchaean to Neoarchaean times - a period extending back from about 4000 to 2500 million years ago. Because of their great age, these rocks have received unprecedented attention from a wide spectrum of Earth scientists striving to learn more about the evolution of the Earth, including its crust, hydrosphere, atmosphere, the commencement of life, and the nature and distribution of mineral deposits. The knowledge gained thus far has accumulated incrementally, beginning with solid field-based studies, the latter being supplemented with increasingly advanced technological developments that have enabled scientists to probe fundamental questions of Earth history. Archaean granite-greenstone terranes display considerable variability of lithologies and geotectonic events, yet there are unifying characteristics that distinguish them from other geological environments. Most greenstone belts consist of a wide variety of volcanic and sedimentary rocks that reflect different evolutionary conditions of formation and all have invariably been influenced by subsequent geotectonic factors, including the intrusion of ultramafic, mafic and granitic complexes, resulting in widespread deformation, metamorphism, metasomatism, as well as mineralization. Geochemical and isotopic age determinations have shown how complex these ancient rocks are and efforts at understanding the nature and evolution of the hydrosphere, atmosphere and primitive life have made Archaean terranes exciting environments in which to study. Conflicting views as to the nature, history and origin of many of the rock types and events in Archaean terranes has been ongoing and stimulating. This review attempts to describe the main lithotypes and other characteristics of granite-greenstone belt geology and points to some areas where contrasting views have been expressed.

Anhaeusser, Carl R.

2014-12-01

32

Workshop on the Tectonic Evolution of Greenstone Belts (supplement containing abstracts of invited talks and late abstracts)  

NASA Technical Reports Server (NTRS)

Topics addressed include: greenstone belt tectonics, thermal constaints, geological structure, rock components, crustal accretion model, geological evolution, synsedimentary deformation, Archean structures and geological faults.

1986-01-01

33

Subaqueous calderas in the Archean Abitibi greenstone belt: An overview and W.U. Mueller a,  

E-print Network

Subaqueous calderas in the Archean Abitibi greenstone belt: An overview and new ideas W.U. Mueller Available online 6 January 2009 Keywords: Archean calderas VMS deposits Abitibi belt Volcanology Carbonate Archean volcanogenic massive sulfide (VMS) deposits, yet documentation of Archean subaqueous calderas

Long, Bernard

34

Thermobarometry in the Hadean: The Nuvvuagittuq Greenstone Belt  

NASA Astrophysics Data System (ADS)

The 4.28 Ga 142Nd model age of the faux-amphibolite formation makes it the oldest assemblage of the Nuvvuagittuq Greenstone Belt (Northeastern Superior Province, Quebec, Canada) and the oldest rocks yet found on Earth. The protolith of the faux-amphibolite, however, is uncertain. The bulk chemistry suggests that it is most likely mafic and basaltic to basaltic-andesite in composition (samples have 36-63 wt% SiO2 and 3.5- 14 wt% MgO), although it has very low Ca-content compared to typical basalt. This low-Ca content is reflected in the crystallization of the amphibole cummingtonite, as opposed to hornblende, that is characteristic of the faux-amphibolite's adjacent gabbro sill. This suggests that Ca and other elements were mobile, perhaps during metamorphism. On the other hand, we do not see low-Ca in the adjacent gabbro sill suggesting either a more complex history for the faux-amphibolite, i.e. a metamorphic event before the emplacement of the gabbro sill, or Ca-depletion as the result of weathering processes. The faux-amphibolite is a heterogeneous gneiss with the mineral assemblage: cummingtonite + quartz + biotite + plagioclase ± anthophyllite ± garnet ± alkali-feldspar with the majority of the biotite replaced by retrograde chlorite. The garnets are heavily fractured, poikioblastic and, apart from the rims, are not zoned with respect to Fe and Mg. The garnets, as well as the groundmass, contain inclusions of zircon, rutile, ilmenite, monazite and other REE phosphates, and iron sulfides. Preliminary garnet-biotite geothermometry has been done that supports upper amphibolite to granulite facies metamorphism. Unzoned garnets from different parts of the faux-amphibolite record distinct Fe-Mg exchange temperatures that range from 730 to 940 °C (assuming a constant pressure of 5 kbar) suggesting the preservation of a metamorphic field gradient. Further geothermobarometry with trace element and accessory phases will be used to further describe the PT path as the resulting trace element zoning profiles may record reactions and loss of phases during the prograde PT path; phases that otherwise are not preserved. Thus, future work using the LA-ICPMS will aim to better constrain the metamorphic compositional changes to the faux-amphibolite's protolith.

Scher, S.; Minarik, W.

2009-05-01

35

Sulfide Mineralization In The Marble Bar Greenstone Belt Around Mount Edger Batholith, Pilbara Craton, Western Australia  

Microsoft Academic Search

Pilbara Craton is one of the most important regions in the world to understand the evolution of early Earth, because the geological history is well preserved through the metamorphism of low grade. Pilbara Craton, Western Australia, consists of two different tectonic components formed 3.6 and 2.8 Ga; an older Archean granite occupying the east Pilbara and greenstone belt. In the

S. Kitazono; M. Nedachi; S. Taguchi

2004-01-01

36

The geology and mineralisation at the Golden Pride gold deposit, Nzega Greenstone Belt, Tanzania  

Microsoft Academic Search

The Golden Pride gold deposit (˜3 Moz) is located in the central part of the Nzega Greenstone Belt at the southern margin of the Lake Victoria Goldfields in Tanzania. It represents an inferred Late Archaean, orogenic gold deposit and is hosted in intensely deformed meta-sedimentary rocks in the hanging wall of the approximately E-W striking Golden Pride Shear Zone. The

I. M. A. Vos; F. P. Bierlein; J. S. Standing; G. Davidson

2009-01-01

37

EVIDENCE FOR 2.45 GA TECTONISM RECORDED in THE NORTH CARIBOU GREENSTONE BELT, NORTHWESTERN ONTARIO  

E-print Network

EVIDENCE FOR 2.45 GA TECTONISM RECORDED in THE NORTH CARIBOU GREENSTONE BELT, NORTHWESTERN ONTARIO.0 Ga to 2.7 Ga, and magmatism is broadly coeval with pervasive deformation and metamorphism. The North Mine are 2.45 Ga. These ages correspond to crustal cooling or a 400-500°C thermal pulse, nearly 300 m

38

The geology and mineralisation at the Golden Pride gold deposit, Nzega Greenstone Belt, Tanzania  

Microsoft Academic Search

The Golden Pride gold deposit (?3 Moz) is located in the central part of the Nzega Greenstone Belt at the southern margin\\u000a of the Lake Victoria Goldfields in Tanzania. It represents an inferred Late Archaean, orogenic gold deposit and is hosted\\u000a in intensely deformed meta-sedimentary rocks in the hanging wall of the approximately E–W striking Golden Pride Shear Zone.\\u000a The hanging-wall

I. M. A. Vos; F. P. Bierlein; J. S. Standing; G. Davidson

2009-01-01

39

3.4-Billion-Year-Old Biogenic Pyrites from Barberton, South Africa: Sulfur Isotope Evidence  

Microsoft Academic Search

Laser ablation mass spectroscopy analyses of sulfur isotopic compositions of microscopic-sized grains of pyrite that formed about 3.4 billion years ago in the Barberton Greenstone Belt, South Africa, show that the pyrite formed by bacterial reduction of seawater sulfate. These data imply that by about 3.4 billion years ago sulfate-reducing bacteria had become active, the oceans were rich in sulfate,

Hiroshi Ohmoto; Takeshi Kakegawa; Donald R. Lowe

1993-01-01

40

Abstract, 2011 Advances in Earth Science Research Conference 2011 Petrogenesis of the Metavolcanic Rocks of the North Caribou Greenstone Belt: Implications for  

E-print Network

Rocks of the North Caribou Greenstone Belt: Implications for tectonic evolution of the Archean are commonly associated with orogenic gold deposits in Archean greenstone belts. The occurrence of biotite of the belt and are in contact with the surrounding granitoids. The metavolcanic rocks "envelope" the Archean

41

Geochemistry of Precambrian carbonates: II. Archean greenstone belts and Archean sea water.  

PubMed

Carbonate rocks with geological attributes of marine sediments are a minor component of the Archean greenstone belts. Despite their relative scarcity, these rocks are important because they record chemical and isotopic properties of coeval oceans. The greenstones containing such carbonates appear to cluster at approximately 2.8 +/- 0.2 and approximately 3.5 +/- 0.1 Ga ago. The samples for the younger group are from the Abitibi, Yellowknife, Wabigoon (Steep Rock Lake), Michipicoten and Uchi greenstone belts of Canada and the "Upper Greenstones" of Zimbabwe. The older group includes the Swaziland Supergroup of South Africa, Warrawoona Group of Australia and the Sargur marbles of India. Mineralogically, the carbonates of the younger greenstones are mostly limestones and of the older ones, ferroan dolomites (ankerites); the latter with some affinities to hydrothermal carbonates. In mineralized areas with iron ores, the carbonate minerals are siderite +/- ankerite, irrespective of the age of the greenstones. Iron-poor dolomites represent a later phase of carbonate generation, related to post-depositional tectonic faulting. The original mineralogy of limestone sequences appears to have been an Sr-rich aragonite. The Archean carbonates yield near-mantle Sr isotopic values, with (87Sr/86Sr)o of 0.7025 +/- 0.0015 and 0.7031 +/- 0.0008 for younger and older greenstones, respectively. The best preserved samples give delta 13C of +1.5 +/- 1.5% PDB, comparable to their Phanerozoic counterparts. In contrast, the best estimate for delta 18O is -7% PDB. Archean limestones, compared to Phanerozoic examples, are enriched in 16O as well as in Mn2+ and Fe2+, and these differences are not a consequence of post-depositional alteration phenomena. The mineralogical and chemical attributes of Archean carbonates (hence sea water) are consistent with the proposition that the composition of the coeval oceans may have been buffered by a pervasive interaction with the "mantle", that is, with the oceanic crust and the coeval ubiquitous volcanosedimentary piles derived from mantle sources. PMID:11539784

Veizer, J; Hoefs, J; Lowe, D R; Thurston, P C

1989-01-01

42

Exploring lithological assemblages and structural styles of granite-greenstone belts  

NSDL National Science Digital Library

1. Day 1: End of class Mini lecture (15 minutes) on: a. what greenstone belts are (where in the world, rock assemblages, structures) b. vertical vs. horizontal tectonic models (old arguments and current details). c. Superior Province (one example) introduction 2. Homework and Jigsaw Activity: Looking at "typical" structures within greenstone belts. This assignment asks students to compare papers with folding models vs. thrusting models. One set of papers that provides a good contrast focuses on the Beardmore-Geraldton greenstone belt in the Superior Province, Canada. Students will also use a paper with Lithoprobe seismic data across the Superior Province. a. Folding model: Kehlenbeck, M. M. 1986. Folds and folding in the Beardmore-Geraldton fold belt. Canadian Journal of Earth Sciences (CJES) 23, 158-171. b. Thrusting model: Devaney, J. R. & Williams, H. R. 1989. Evolution of an Archean subprovince boundary: a sedimentological and structural study of part of the Wabigoon-Quetico boundary in northern Ontario. CJES 26 1013-1026. c. Percival, J. A. et al. 2006. Tectonic evolution of the western Superior Province from NATMAP and Lithoprobe studies. CJES 43(7): 1085-1117. Divide the class into 3 "expert" groups and assign one paper to each group. Students need to create an outline of the major structures (faults, folds, both) described and the evidence provided for the structural interpretation. Students should bring two copies of their outline to class. 3. Day 2 Turn in one copy of outline (to be assessed for grade) and meet with the group to create a composite, master outline (30 minutes). Students break up into small groups (one from each "expert" group), discover very different structural style interpretations, and try to determine WHY there are the discrepancies (lack of data, preconceived notions influencing interpretations, etc). The goal of the new group is to prepare each student to write a short paper. Each student is assigned to write a 1-page paper exploring reasons why there are discrepancies between the models. Students are also encouraged to speculate on what other evidence or future research might help resolve the apparent conflict. Students begin paper in class and finish outside of class. 4. Day 3 Students hand in paper (to be graded). Mini lecture/ discussion on key related questions. a. Does either model (folding or faulting) support or negate either vertical or horizontal tectonic models? b. Are there any modern analogues to greenstone belts? If so, what are the differences or limitations to the comparisons (lithological and structural)?

Czeck, Dyanna

43

Structure of Southwestern Michipicoten Greenstone Belt, Ontario: Evidence for Archean accretion  

NASA Technical Reports Server (NTRS)

The results of detailed mapping of a well exposed (by a large fume kill) Archean Michipicoten greenstone belt of Ontario is discussed. Numerous structural features are described including soft sediment deformation, thrust faults, isoclinal folds, and sill intrusion, which apparently formed prior to the earliest flattening cleavage. It was inferred that all of these events may have taken place before the rocks were completely lithified, and the question was raised as to whether early soft sediment and tectonic deformation were coeval. If so, the overall picture would permit (but not compel) recognition of a convergent oceanic environment such as an accretionary wedge or forearc basin.

Mcgill, George E.; Shrady, Catherine H.

1988-01-01

44

The geology of the Morro Velho gold deposit in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero, Brazil  

Microsoft Academic Search

The Morro Velho gold deposit, Quadrilátero Ferrífero region, Minas Gerais, Brazil, is hosted by rocks at the base of the Archean Rio das Velhas greenstone belt. The deposit occurs within a thick carbonaceous phyllite package, containing intercalations of felsic and intermediate volcaniclastic rocks and dolomites. Considering the temporal and spatial association of the deposit with the Rio das Velhas orogeny,

Diogenes Scipioni Vial; Ed DeWitt; Lydia Maria Lobato; Charles H. Thorman

2007-01-01

45

Unravelling the Maggie Hays and Emily Ann nickel sulphide deposits via a multidisciplinary study of the Archaean Lake Johnston Greenstone Belt, Yilgarn Craton, Western Australia  

Microsoft Academic Search

In order to better understand the architecture and structural evolution of the Archaean Lake Johnston Greenstone Belt and predict, the distribution of remobilized magmatic ultramafic nickel-sulphide mineralization in the belt, a multidisciplinary study has been carried out on the central area of the greenstone belt around the Maggie Hays and Emily Ann nickel-sulphide deposits. The nickel-sulphide deposits are hosted in

A. Joly; J. Miller; C. Stott; T. McCuaig; M. Duguet

2008-01-01

46

Micro-PIXE elemental imaging of pyrites from the Bulawayan-Bubi Greenstone Belt, Zimbabwe  

NASA Astrophysics Data System (ADS)

Micro-PIXE at the NAC nuclear microprobe was used for studies of a sequence of unusual pyrite-bearing carbonate sediments from the east of Turk Mine, Bubi Greenstone Belt, Zimbabwe. This pyrite mineralization shows a variety of textures, and its petrographic interpretation needed more solid geochemical evidence. Elemental maps were obtained using Dynamic Analysis (DA) (a rapid matrix transform method) which forms part of the GeoPIXE software package, and were complemented by point analyses in selected areas. The implemented on-demand beam deflection system allowed for count rates of the order of 3000 counts/s with negligible dead time. The distribution of As and other elements confirmed the petrographic interpretation of three different pyrite generations. In addition, point analyses showed that Sb and Pb were significantly elevated in the zones of As enrichment.

Xenophontos, L.; Stevens, G.; Przybylowicz, W. J.

1999-04-01

47

Remnants of an Early Archaean (>3.75 Ga) sea-floor, hydrothermal system in the Isua Greenstone Belt  

Microsoft Academic Search

Localised low-strain domains in the ?3.75 Ga Isua Greenstone Belt, West Greenland, contain a wealth of well-preserved primary structures. These include pillow lavas with dark, fine-grained cooling rims, pillow breccias, debris flows and conglomerates. Here we describe quartz globules from a relatively undeformed pillow breccia, which contains unstrained quartz. Most quartz globules contain only few quartz grains, but some of

Peter W. U Appel; Hugh R Rollinson; Jacques L. R Touret

2001-01-01

48

Overview of the Barberton Drilling Project  

NASA Astrophysics Data System (ADS)

The Barberton Greenstone Belt in South Africa is one of the best-preserved successions of mid- Archean (3.5-3.2 Ga) supracrustal rocks in the world, and, as such, a remarkable natural laboratory where conditions and processes at the surface of the Archean Earth can be studied in detail. Volcanic and sedimentary sequences in the belt provide information on the environment in which life emerged and evolved. A drilling project, sponsored by the International Continental Drilling Program (ICDP), and many national funding agencies, was completed in May 2012. More than 3000 m of core from 5 holes at four sites were recovered. At the Tjakastad site, two ca. 300 m holes were drilling through sequences of komatiites and komatiitic basalts. The other three holes targeted sedimentary rocks: the Buck Reef hole sampled over 700m of mainly banded black and white cherts; the Mid Fig Tree hole sampled a sequence of ferruginous charts and mudstones; and the Barite Valley hole samples a more varied sequence including sandstone, shale, cherts and volcaniclastic rocks. The core is stored and has been logged in facilities of the University of the Wirwatersrand. Core logs can be found at tp://www.peeringintobarberton.com/Sites.html . An open call for proposals to work on the core, sent out in November 2012, was answered by over 50 scientists from 12 countries who plan to study the core using techniques ranging from petrography, through major and trace-element analysis, to sophisticated isotopic analysis. A workshop to discuss the drilling project and to view the core is planned at the University of the Witwatersrand in Johannesburg from Mon 18th to Wed the 21st February 2013, followed by a short trip to the Barberton belt to visit the drilling sites.

Arndt, Nicholas T.; Wilson, Allan; Mason, Paul; Hofmann, Axel; Lowe, Don

2013-04-01

49

3-D imaging of the Central Lapland Greenstone Belt using magnetotelluric and seismic data  

NASA Astrophysics Data System (ADS)

New broadband magnetotelluric (MT) data were acquired in the Central Lapland Greenstone Belt (CLGB) area, northern Finland, during the field campaigns in 2009 and 2010. The measurements belong to an ongoing project at the Geological Survey of Finland. The project intends to create the target- and regional scale 3-D models of the CLGB area using potential field, seismic and electromagnetic data. The survey area is located in the western and northern parts of the CLGB that is one of the largest Proterozoic greenstone belts in the world. In the north and west, the survey area is bordered by Proterozoic granitic rocks and intrusions. The CLGB consists of a Palaeoproterozoic (2.5 - 1.97 Ga) volcanic and sedimentary cover that was deposited on the Archaean (> 2.5 Ga) basement. The Kittilä Group greenstones, which form the core of the CLGB, are suggested representing an allochtonous unit, is bound by tectonic contacts with older units surrounding it (Hanski, 1997). The collected MT dataset consists of the data from 80 sites with the frequency range of 300 - 0.002 Hz and the site spacing of 500 m - 4 km. At the first stage, the MT data were analyzed along a number of crossing 2-D lines. MT parameters were also examined as maps, because the central part of the survey area forms a magnetotelluric array. A regional electrical dimensionality and strike were studied with invariants and various decomposition techniques. Regional electrical dimensionality proved to be mainly 2-D and 3-D except for some northern MT sites in resistive granite-hosted regions, which fulfilled criteria for 1-D interpretation. Smooth 2-D conductivity models were obtained by inverting the determinant of the impedance tensor (Siripunvaraporn & Egbert, 2000; Pedersen & Engels, 2005) and TE- and TM- data jointly using the nonlinear conjugate gradient algorithm of Rodi & Mackie (2001). Model resistivities range from 0.1 Ohm-m to greater than 20 000 Ohm-m in the survey area. The highest conductivities are related to N-S elongated graphite- and sulfide-bearing schists of the CLGB, which are visible also in the airborne electromagnetic data of the study area. Results show that these conductors have the deep roots of about 5 - 10 km. The highest resistivities emerge from granite intrusions that are located in the northern part of the study area. In the west, the resistivity of the CLGB is much higher with no indications of high-conductivity anomalies in the uppermost 40 km. However, in the westernmost part of the study area, a conductivity contrast is observed at the depth of about 10 km possibly indicating the contact zone of the two cratons of the Fennoscandian Shield, i.e. the Karelian and the Norbotten cratons (Lahtinen et al., 2005). 2-D inversion models are presented together with seismic data from the Finnish Reflection Experiment (FIRE) along the CMP-lines 4A and B. In the eastern and central parts of the study area, conductivity anomalies are usually associated with dipping reflectors, whereas such a relationship is not evident in the western part of the study area.

Lahti, I.; Korja, T.; Smirnov, M.; Vaittinen, K.; Sandgren, E.; Niiranen, T.; Nykänen, V.

2012-04-01

50

3.4-Billion-year-old biogenic pyrites from Barberton, South Africa: sulfur isotope evidence  

NASA Technical Reports Server (NTRS)

Laser ablation mass spectroscopy analyses of sulfur isotopic compositions of microscopic-sized grains of pyrite that formed about 3.4 billion years ago in the Barberton Greenstone Belt, South Africa, show that the pyrite formed by bacterial reduction of seawater sulfate. These data imply that by about 3.4 billion years ago sulfate-reducing bacteria had become active, the oceans were rich in sulfate, and the atmosphere contained appreciable amounts (>>10(-13) of the present atmospheric level) of free oxygen.

Ohmoto, H.; Kakegawa, T.; Lowe, D. R.

1993-01-01

51

The geology and mineralisation at the Golden Pride gold deposit, Nzega Greenstone Belt, Tanzania  

NASA Astrophysics Data System (ADS)

The Golden Pride gold deposit (˜3 Moz) is located in the central part of the Nzega Greenstone Belt at the southern margin of the Lake Victoria Goldfields in Tanzania. It represents an inferred Late Archaean, orogenic gold deposit and is hosted in intensely deformed meta-sedimentary rocks in the hanging wall of the approximately E-W striking Golden Pride Shear Zone. The hanging-wall sequence also includes felsic (quartz porphyritic) to mafic (lamprophyric) intrusions, as well as banded iron formations. Hydrothermal alteration phases associated with mineralisation are dominated by sericite and chlorite. Two main ore types can be distinguished, chlorite and silica ore, both occupying dilational sites and structural intersections in the hanging wall of the main shear zone. Sulphide minerals in both ore types include pyrrhotite, arsenopyrite, pyrite and accessory sphalerite, galena, sulphosalts and Ni-Co-Bi sulphides. Gold and tellurides are late in the paragenetic sequence and associated with a secondary phase of pyrrhotite deposition. Sulphur isotope compositions range from -6 to 7 per mil and are interpreted to reflect contributions from two distinct sources to the mineralising fluids in the Golden Pride gold deposit. A redox change, potentially induced by the intrusion of mafic melts, together with structural elements in the hanging wall of the Golden Pride Shear Zone, are interpreted to be the main controls on gold mineralisation in this deposit.

Vos, I. M. A.; Bierlein, F. P.; Standing, J. S.; Davidson, G.

2009-10-01

52

Discovering the Carrier Phase of the Extraterrestrial Component in Archean Spherule Layers, Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

Comprehensive study of sedimentary, petrographic, mineralogical, and geochemical characteristics from a set of new samples of Archean spherule layers in the ICDP Drill Core BARB5 from the Barite Valley.

Mohr-Westheide, T.; Fritz, J.; Reimold, W. U.; Schmitt, R. T.; Hofmann, A.; Koeberl, C.; Luais, B.; Tagle, R.; Salge, T.; Hoehnel, D.

2014-09-01

53

Spherule Size Distribution in the BARB5 ICDP Drill Core from the Barberton Greenstone Belt, South Africa  

NASA Astrophysics Data System (ADS)

On the four 4 cm thick spherule layers of the ICDP BARB5 drill core grain size analysis has been performed. The grain size statistics do not indicate regular decrease of spherule sizes, so do not represent a single impact bed.

Hoehnel, D.; Mohr-Westheide, T.; Fritz, J.; Reimold, W. U.

2014-09-01

54

Early Archean fossil bacteria and biofilms in hydrothermally-influenced sediments from the Barberton greenstone belt, South Africa  

Microsoft Academic Search

SEM imaging of HF-etched, 3.3–3.5 Ga cherts from the Onverwacht Group, South Africa reveals small spherical (1 ?m diameter) and rod-shaped structures (2–3.8 ?m in length) which are interpreted as probable fossil coccoid and bacillar bacteria (prokaryotes), respectively, preserved by mineral replacement. Other, possibly biogenic structures include smaller rod-shaped bacteriomorphs (<2 ?m in length) and bacteriomorph moulds. The identification of

Frances Westall; Maarten J de Wit; Jesse Dann; Sjerry van der Gaast; Cornel E. J de Ronde; Dane Gerneke

2001-01-01

55

The Cosmos greenstone succession, Agnew-Wiluna greenstone belt, Yilgarn Craton, Western Australia: Geochemistry of an enriched Neoarchaean volcanic arc succession  

NASA Astrophysics Data System (ADS)

The geodynamic setting of the Neoarchaean Eastern Goldfields Superterrane (EGS) of the Yilgarn Craton is the subject of debate. Some authors propose plume models, while others advocate variants on a subduction accretion model for the origin of mineralised greenstone belt sequences. Felsic volcanism in the Kalgoorlie Terrane, the westernmost terrane of the EGS, is considered to have a tonalite-trondhjemite-granodiorite/dacite (TTG/D) geochemical affinity. The Cosmos greenstone succession, which lies in the Agnew-Wiluna greenstone belt (AWB) of the Kalgoorlie Terrane, contains several komatiite-hosted nickel sulphide deposits, the volcanic footwall to which consists of an intercalated succession of fragmental and coherent rocks ranging in composition from basaltic andesite to rhyolite. Light rare earth elements (LREEs) and large ion-lithophile elements (LILEs) are strongly enriched relative to high field strength elements (HFSEs) across all volcanic units, and the rocks display strong positive Pb and negative Nb anomalies. These geochemical characteristics resemble closely those of modern high-K calc-alkaline to shoshonite continental arc successions. Contrasting REE, LILE and HFSE concentrations, coupled with assimilation-fractional crystallisation (AFC) modelling, shows that the intercalated dacitic and andesitic volcanic rocks within the footwall succession are not co-genetic. Xenocrystic zircons within the felsic volcanic lithologies indicate that some assimilation of older continental crust contributed to the generation of the footwall volcanic sequence. The geochemical characteristics of the Cosmos volcanic succession indicate that parental melts were derived via partial melting of enriched peridotite that had been contaminated by subducted crustal material within the mantle wedge of a subduction zone. In contrast, two younger felsic porphyry intrusions, which cross-cut the volcanic succession, have a distinct TTG/D affinity. Therefore, these intrusions are considered to be generated via partial melting of a subducting slab and are related to local high-Ca granitoid intrusions. The Cosmos volcanic succession represents the first extrusive high-K calc-alkaline to shoshonitic volcanic arc sequence described in the Kalgoorlie Terrane and, coupled with age dating of the stratigraphy, is indicative of formation in a long-lived volcanic arc setting active from 2736 Ma to later than 2724 Ma. The composition and geochemical affinity of the volcanic footwall succession to the Cosmos komatiite-hosted nickel-sulphide deposits contrasts with the majority of felsic volcanic rocks within the AWB and also the wider Kalgoorlie Terrane, suggesting that the overall architecture of this region is more complex than is currently thought. Our conclusions not only have consequences for recent models of the tectonic evolution of the EGS but also contribute to the debate on the operation of plate tectonics during the late Archaean in general. The arc affinity of the Cosmos volcanic succession, containing abundant high-K calc-alkaline andesite lavas, provides further support for the operation of plate tectonics in the Neoarchaean.

de Joux, A.; Thordarson, T.; Fitton, J. G.; Hastie, A. R.

2014-09-01

56

Sedimentary Depositional Environment in the Nuvvuagittuq Greenstone Belt, Northeastern Superior Province, Canada  

NASA Astrophysics Data System (ADS)

Our knowledge of Earth's primitive surface environment is limited by the very few outcrops of demonstrably sedimentary rocks we have available. The Nuvvuagittuq Greenstone Belt (NGB) is an Eoarchean/Hadean volcano-sedimentary assemblage emplaced prior to 3.75 Ga (Cates and Mojzsis 2007) and likely as early as 4.28 Ga (O'Neil et al. 2008). Its recent discovery extends the inventory of available outcrops and pushes back the limit of time that we previously had access to. The rocks included within the NGB may represent Earth's oldest sedimentary rocks in the world and, in this respect, may provide crucial information about Earth's primitive surface environment. Our recent sampling of the NGB reveals three distinct sedimentary assemblages comprised of a sulfide-rich quartzite and two different types of banded iron formations (BIF). Here our aim is to constrain protoliths of these sedimentary rocks, with the aim of deducing the original depositional environments. Accordingly, we have mapped the relationships between the different lithologies in detail. The two BIF horizons are a few meters thick and run sub parallel to each other, separated by a horizon of cummingtonite-bearing amphibolite (previously referred to as Faux-amphibolite). Both contain cm-scale quartz-, magnetite-, and amphibole-rich laminations, but differ distinctly from each other. BIF 1 is very magnetite rich with quartz and is relatively poor in sulfides, while BIF 2 has large amounts of sulfides and green amphibolite, but is very poor in magnetite. The quartzite horizon is considerably larger (reaching thicknesses of ˜ 50 m) and is mainly formed of coarse quartz grains with minor disseminated sulfide grains. In order to supplement this field observation, we started a detailed petrological description and performed chemical analyses on our sample set. At the conference we will propose possible environmental deposition conditions for these rocks and reconstruct possible sedimentary protoliths. In addition we will present preliminary sulfur and iron isotope analyses that will allow further comparisons between the three sedimentary units.

Binnion, L.; Thomassot, E.; O'Neil, J.; Francis, D.; Busigny, V.; Wing, B.

2009-05-01

57

Volcanic-hosted massive sulfide deposits in the Murchison greenstone belt, South Africa  

NASA Astrophysics Data System (ADS)

The Archean Murchison greenstone belt, Limpopo Province, South Africa, represents a rifted epicontinental arc sequence containing the largest volcanic-hosted massive sulfide (VMS) district in Southern Africa. The so-called Cu-Zn line is host to 12 deposits of massive sulfide mineralization including: Maranda J, LCZ, Romotshidi, Mon Desir, Solomons, and Mashawa with a total tonnage of three million metric tons of very high grade Zn, subordinate Cu, and variable Pb and Au ore. The deposits developed during initial phases of highly evolved felsic volcanism between 2,974.8 ± 3.6 and 2,963.2 ± 6.4 Ma and are closely associated with quartz porphyritic rhyolite domes. Elevated heat supply ensured regional hydrothermal convection along the entire rift. Recurrent volcanism resulted in frequent disruption of hydrothermal discharge and relative short-lived episodes of hydrothermal activity, probably responsible for the small size of the deposits. Stable thermal conditions led to the development of mature hydrothermal vent fields from focused fluid discharge and sulfide precipitation within thin layers of felsic volcaniclastic rocks. Two main ore suites occur in the massive sulfide deposits of the “Cu-Zn line”: (1) a low-temperature venting, polymetallic assemblage of Zn, Pb, Sb, As, Cd, Te, Bi, Sn, ±In, ±Au, ±Mo occurring in the pyrite- and sphalerite-dominated ore types and (2) a higher temperature suite of Cu, Ag, Au, Se, In, Co, Ni is associated with chalcopyrite-bearing ores. Sphalerite ore, mineralogy, and geochemical composition attest to hydrothermal activity at relatively low temperatures of ?250 °C for the entire rift, with short-lived pulses of higher temperature upflow, reflected by proportions of Zn-rich versus Cu-rich deposits. Major- and trace-metal composition of the deposits and Pb isotope signatures reflect the highly evolved felsic source rock composition. Geological setting, host rock composition, and metallogenesis share many similarities not only with Archean VMS districts in Canada and Australia but also with recent arc-back-arc systems on the modern seafloor where fragments of continental crust and areas of elevated heat flow are involved in petrogenetic and associated metallogenic processes.

Schwarz-Schampera, Ulrich; Terblanche, Hennie; Oberthür, Thomas

2010-02-01

58

Origin of Peculiar Horizons from the Nuvvuagittuq Greenstone Belt: Testing the Conglomerate Hypothesis  

NASA Astrophysics Data System (ADS)

Earth's earliest rock record is fragmentary, and often distorted by metamorphic changes suffered under great temperatures and pressures. Recent work may, however, have opened the door to more direct examination of the earliest Earth. Measurements of Nd-142 from rocks of the Nuvvuagittuq Greenstone Belt (NGB), N. Quebec yield an apparent 4.28 Ga isochron (O'Neil et al., 2008). These are potentially the oldest rocks on Earth and understanding the protoliths of the rocks of the NGB may help constrain Earth's earliest surface environment. Peculiar horizons of quartz-rich rocks within the NGB have been hypothesized to represent metamorphosed conglomerates. In order to evaluate this hypothesis, we apply a series of consistency tests aimed at observations ranging from the field to microscale. First, we made high-resolution (10m grid) maps of the purported conglomerate horizons, and interpreted the map pattern of these horizons for their conformity with sedimentary contacts. The horizons are continuous throughout the mapped area, and do not cross cut any other lithologies, which is necessary, but not sufficient, evidence for a sedimentary origin. Second, we examined the mineralogy and three-dimensional geometry of the potential clasts in large polished blocks. The potential clasts fall into just two different types: the dominant type is made up primarily of coarse grains of quartz; the second type is distinctly subordinate and is largely made up of fine-grained equigranular quartz and relict plagioclase with minor amounts of biotite. The dominant type can occur as lozenge-shaped pods up to 5 cm thick, while the subordinate type more commonly occurs as thin (<2 cm thick) undulose layers. Neither the mineralogies nor the geometries of the potential clasts offer certain indication of a sedimentary origin, though they are potentially consistent with one. Third, we are comparing the identity and chemistry of trace minerals within the potential clasts to that of the surrounding matrix. Preliminary results suggest that the matrix hosts many zircon, monazite and xenotime neoblasts as well as a variety of sulfide minerals, while most of the trace minerals in the dominant type of potential clasts are euhedral sulfides, with rare chromite-rich regions. Trace zircon and monazite are more common in the subordinate type of potential clasts, with zircon occasionally exhibiting that show a concentric but truncated zonation. And finally, we are also measuring sulfur isotope compositions of sulfides from the potential clasts and from the matrix. The key principle linking these two consistency tests is the presence or absence of mineralogical, mineral chemical, and isotopic heterogeneity.

Kitayama, C.; Thomassot, E.; Wing, B. A.

2009-05-01

59

Sediment provenance in the Palaeoproterozoic Rio Itapicuru greenstone belt, Brazil, indicates deposition on arc settings with a hidden 2.17-2.25 Ga substrate  

NASA Astrophysics Data System (ADS)

A study of sediment provenance and tectonic setting was carried out for the first time on metasedimentary rocks of the Rio Itapicuru greenstone belt, Serrinha Block, São Francisco craton, Brazil, using a combination of LA-ICP-MS zircon U-Pb geochronology, whole-rock geochemistry and Sm-Nd isotope data. The protoliths of the studied phyllites, micaschists and biotite gneisses were classified mostly as mudstones and impure sandstones, i.e. shales and greywackes. The chemical index of alteration (CIA) ranges from 39 to 70 indicating moderate chemical weathering in source areas. Intermediate and felsic rocks (granite, granodiorite, rhyolite and andesite) are the likely main source rocks, and less often mafic rocks (basalt and gabbro). The depleted-mantle Nd model ages (TDM), most in the range 2.0-2.2 Ga, and the positive ?Nd values for the proposed deposition time (ca. 2115 Ma) suggest source rocks mainly in the greenstone belt. The U-Pb data on detrital zircon grains of four samples yielded 207Pb/206Pb age mostly in the timespan 2125-2237 Ma, with age populations clustering at 2164 ± 4 Ma and 2209 ± 4 Ma, and minor outliers at ca. 2112 Ma, 2270 Ma, and 2415 Ma. The results indicated that the metasedimentary rocks of the Rio Itapicuru greenstone belt have source areas mainly in Palaeoproteroic terranes such as the Rio Itapicuru and Rio Capim greenstone belts. The zircon populations between 2.17 Ga and 2.24 Ga are not found in the Serrinha block, thus requiring sources that are not known in the region. Diagrams of tectonic setting suggest that the sediments may have been deposited on continental island arc. Our data support a model in which basalts and arc granites of the Rio Itapicuru greenstone belt were accreted onto an unknown continental or arc margin and the entire pile collided with, and were thrust onto a microcontinent represented by the adjacent Archaean basement complex.

Grisolia, Maria Fernanda P.; Oliveira, Elson P.

2012-10-01

60

Pluton emplacement within an extensional transfer zone during dextral strike-slip faulting: an example from the late Archaean Abitibi Greenstone Belt  

Microsoft Academic Search

The Lake Abitibi area within the late Archaean Abitibi Greenstone Belt exhibits an interlinked plutonic, structural and metamorphic evolution that may characterize segmented strike-slip faults at upper-to-mid-crustal levels. Along the major, southeastward propagating Macamic D2 dextral strike-slip fault, Theological and preexisting D1 structural heterogeneities induced the development of NNW-trending dextral-oblique splays which evolved into an extensional trailing fan and created

S. Lacroix; E. W. Sawyer; E. H. Chown

1998-01-01

61

Geochemistry of shales from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe: Implications for provenance and source-area weathering  

Microsoft Academic Search

Phyllites from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe, were deposited on a stable cratonic platform. Analyses of the phyllites generally define a single geochemical group based on major-and trace-element abundances. The phyllites are strongly depleted in CaO, Na2O, and Sr with respect to average Archean upper crust. By contrast, K2O, Ba, and Rb are enriched several times relative

Christopher M. Fedo; Kenneth A. Eriksson; Eirik J. Krogstad

1996-01-01

62

HFSE\\/REE fractionations recorded in three komatiite-basalt sequences, Archean Abitibi greenstone belt - Implications for multiple plume sources and depths  

Microsoft Academic Search

Komatiite-tholeiite sequences in the Archean Abitibi greenstone belt show systematic differences of REE patterns and high field strength element (HFSE)\\/REE fractionations between volcanic centers. Type 1 komatiites are Al undepleted, and have flat REE patterns, with mantle-normalized Nb, Zr, Hf\\/REE of about 1. Type 2 komatiites are relatively MgO-rich, Al-undepleted, with LREE depletion and positive normalized Nb, Zr, Hf\\/REE fractionations.

Q. Xie; R. Kerrich; J. Fan

1993-01-01

63

Brazil's premier gold province. Part II: geology and genesis of gold deposits in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero  

Microsoft Academic Search

Orogenic, gold deposits are hosted by rocks of the Archean Rio das Velhas greenstone belt in the Quadrilátero Ferrífero region, Minas Gerais state, Brazil, one of the major gold provinces in the world. The gold deposits occur at the base of the mafic-ultramafic succession, with the most important orebodies controlled by E-W-striking, strike-slip faults. The main mineralization styles are (1)

Lydia Lobato; Luiz Ribeiro-Rodrigues; Frederico Vieira

2001-01-01

64

The volcanology of komatiites as deduced from field relationships in the Norseman-Wiluna greenstone belt, Western Australia  

NASA Astrophysics Data System (ADS)

Komatiites in the western part of the Norseman-Wiluna greenstone belt in the Yilgarn Block of Western Australia display a wide variety of volcanic facies, ranging from very thin differentiated Munro Township-type flow units through to very thick olivine-rich cumulate flow units containing high proportions of adcumulate dunite. Cumulate flow units have been mapped in detail in the Agnew-Wiluna segment of the Norseman-Wiluna Greenstone Belt. In the Yakabindie and Mt. Keith areas, thick lenticular bodies of olivine adcumulate are flanked and overlain by thinner sheet-like sequences of finer grained olivine orthocumulates. They show fine-scale internal layering, broad-scale cryptic layering and upper fractionated sequences containing harrisites, pyroxene bearing cumulates and in some cases gabbroic derivatives. Low grade disseminated sulphide mineralisation occurs within the dunite lenses. In the stratigraphically equivalent Kathleen East area adcumulate dunite grades laterally into olivine orthocumulates and spinifex textured flows. A similar relationship is also seen further south, where the Perseverance ultramafic complex consists of a thick central dunite lens flanked on one side by thin fine grained orthocumulate sequences and on the other by intercalated orthocumulates and spinifex textured flows. These field relationships indicate an extrusive origin for the adcumulate dunite bodies. The Walter Williams Formation, in the west-central part of the Norseman-Wiluna Belt, is a very large cumulate flow unit 150 km long and 30 km wide in presently exposed extent. It consists of a central sheet-like body of adcumulate dunite, underlain and overlain by olivine orthocumulates. The adcumulate sheet is everywhere capped by a distinctive thin layer of olivine harrisite. At its northernmost extent, the flow unit consists of cyclically layered olivine and pyroxene bearing cumulates capped by gabbros, dolerites and pyroxene spinifex-textured material, interpreted as a periodically replenished lava lake sequence. Both the lenticular dunite bodies of the Agnew-Wiluna Belt and the sheet-like dunite body of the Walter Williams Formation are interpreted as crystallisation products of very large submarine komatiite lava flows which erupted and flowed at very high rates. The adcumulate dunites are interpreted as the products of in situ crystallisation at low degrees of supercooling at the top of upward and inward accreting crystal piles at the bases of the flows. Flanking and overlying olivine orthocumulates reflect higher rates of heat loss at the site of crystallisation due to lower lava flow rates. Field evidence from Perseverance, and the general geometry of the dunite lenses, suggest that the lenses formed within large thermal erosion channels developed by turbulent lava rivers flowing over low-melting felsic volcanic substrates. The textural range exhibited by komatiites can be integrated into a comprehensive model for the geometry of large komatiite flow fields formed by rapid extrusion. Dunite sheets form close to the eruption sites, and dunite lenses as a result of channellisation further away from the vent, or close to the vent in the situation where the substrate is non-refractory and thermal erosion can take place readily. Kambalda-type volcanic facies develop in more distal environments where lava emplacement is channellised and episodic, and Munro-type flow units represent small scale lava tubes formed at low flow rates on the distal flanks of major eruptions, or close to the vent of very small ones. Waning eruption rates leads to proximal facies being overridden by distal ones, a common observation in komatiite sequences. The size of thermal erosion channels requires very rapid eruption rates comparable to those in Phanerozoic flood basalt terrains.

Hill, R. E. T.; Barnes, S. J.; Gole, M. J.; Dowling, S. E.

1995-01-01

65

A glimpse of Earth's primordial crust: The Nuvvuagittuq greenstone belt as a vestige of mafic Hadean oceanic crust  

NASA Astrophysics Data System (ADS)

Investigation of Earth’s primitive crust is biased towards felsic rocks because they contain zircons that provide robust geochronological constraints. Felsic rocks, however, cannot be derived directly from the mantle thus the first crust had to be mafic in composition. Obtaining precise ages on old mafic rocks is however difficult due to their lack of zircon and the metamorphic overprinting they have suffered. 143Nd and 142Nd analyses on the Nuvvuagittuq greenstone belt suggests that its mafic components formed more than 4 billion years ago and that the dominant lithology of the belt, known as the “faux-amphibolite”, represents the only relict of Hadean crust formed at ~4.3 Ga. Its protolith is interpreted to be mafic volcanic rocks and volcanic pyroclastic deposits. The faux-amphibolite can be divided into three distinct geochemical group stratigraphically superimposed. The faux-amphibolite at the base of the sequence is tholeiitic with a composition indicating derivation of primary melts from an undepleted mantle and fractionation under dry conditions. Towards the top of the volcanic sequence, the faux-amphibolites are characterized by higher Al/Ti ratios. They appear to have fractionated under elevated water pressure and are geochemically similar to modern boninite and calc-alkaline volcanic rocks. A new series of faux-amphibolite was analysed for 142Nd isotopic composition. 21 samples have deficits in 142Nd ranging from -7 to -18 ppm compared to the terrestrial standard. These deficits have now been confirmed by measurements of the same samples at ETH (Roth et al., GCA, A886, 2010). A 146Sm-142Nd isochron constructed for all faux-amphibolite yields an age of 4368 +72-142 Ma (n=30). A line fit only to the faux-amphibolite compositional group that shows the widest range in LREE enrichment, including corresponding co-genetic ultramafic sills gives a 146Sm-142Nd age of 4381 +67-123 Ma (n=21). The Hadean age for the faux-amphibolite is supported by a 4079 ± 110 Ma (n=15) 147Sm-143Nd age for intruding gabbro sills. The supracrustal sequence has been highly metamorphosed with isotopic data suggesting metamorphic events at circa 3.8 Ga and 3.1 Ga with the last significant heating event recorded at ~2.65 Ga in Sm-Nd data for garnets from the faux-amphibolite. This supports a mafic composition for Earth’s primitive crust with a compositional transition from tholeitic to boninitic and calc-alkaline volcanic rocks. The presence of pillow basalts supports a subaqueous eruption for at least a portion of the province. The Nuvvuagittuq faux-amphibolite shares some chemical characteristics with the 3.8 Ga Garbenschiefer unit of the Isua greenstone belt in SW Greenland. Both the Garbenschiefer and the faux-amphibolite are chemically similar to modern-day suprasubduction volcanic arc lavas suggesting that modern plate tectonic regime already may have been established on Earth by the Hadean/Eoarchean. Regardless of the tectonic regime, the similarities between the 3.8 Ga Garbenschiefer and the Nuvvuagittuq 4.3 Ga faux-amphibolite suggest that their chemical features are perhaps characteristic of Earth’s early mafic crust.

O'Neil, J.; Carlson, R. W.

2010-12-01

66

THE MURCHISON GREENSTONE BELT, SOUTH AFRICA: ACCRETED1 SLIVERS WITH CONTRASTING METAMORPHIC CONDITIONS2  

E-print Network

temperature-deformation (P-T-D) histories, and are separated from each other by relatively narrow, high-34 deformation patterns observed throughout the belt. These patterns are explained by a N-S compressional36.precamres.2012.03.005 #12;2 ± 0.6 kbar at 570°C, along a relatively hot, minimum apparent geotherm of ~30°C

Boyer, Edmond

67

A Detailed Record of Archean Biogochemical Cycles and Seawater Chemistry Preserved in Black Shales of the Abitibi Greenstone Belt  

NASA Astrophysics Data System (ADS)

Geological and biological evolution are intimately linked within the Earth System through the medium of seawater. Thus, in order to track the co-evolution of Life and Earth during the Archean Eon we must determine how biogeochemical cycles responded to and initiated changes in the composition of Archean seawater. Among our best records of biogeochemical cycles and seawater chemistry are organic carbon-rich black shales. Here we present a detailed multi-proxy study of 2.7 Ga black shales from the Abitibi Greenstone Belt, Canada. Abitibi shales demonstrate extreme enrichments in total organic carbon (up to 15 wt. %) and total sulfur (up to 6 wt. %) reflecting vigorous biogeochemical cycling in the basin, likely driven by cyanobacteria. The speciation of reactive Fe minerals indicates that pyrite formed in a sulfidic water column (euxinia) and that dissolved Fe was the limiting reactant. The deposition of more than 50 m of euxinic black shales suggests that the Fe-rich conditions reflected by Archean BIF deposition were not necessarily ubiquitous. Biologically significant trace metals fall into two categories. Metals that can be delivered to seawater in large quantities from hydrothermal sources (e.g., Cu and Zn) are enriched in the shales, reflecting their relative abundance in seawater. Conversely, metals that are primarily delivered to the ocean during oxidative weathering of the continents (e. g., Mo and V) are largely absent from the shales, reflecting depleted seawater inventories. Thus, trace metal supply at 2.7 Ga was still dominated by geological processes. Biological forcing of trace metal inventories, through oxidative weathering of the continents, was not initiated until 2.5 Ga, when Mo enrichments are first observed in the Mt. McRae Shale, Hamersley Basin. Multiple sulfur isotope analysis (32S, 33S, 34S) of disseminated pyrite displays large mass independent fractionations (?33S up to 6 %) reflecting a sulfur cycle dominated by atmospheric processes under low oxygen conditions. Pyrite sulfur isotopes generally display a positive correlation between the magnitude of MIF (?33S) and enrichments in ?34S, producing a slope of ~1.1, a common feature for Archean pyrites. The preservation of large quantities of pyrite sulfur with a characteristically Archean isotopic signature suggests that a volcanic source of sulfur is sufficient to drive localized and long-lived euxinic conditions provided that organic matter is abundant and dissolved Fe is scarce. The most remarkable characteristic of black shales from the Abitibi Greenstone Belt is the preservation of large concentrations of organic carbon. This suggests that fixed N was at least locally abundant for extended periods of time in the Archean. Future work on Archean biogeochemical cycles, and their influence on Earth's delayed oxygenation, should attempt to determine if N fixation was localized or global in nature.

Scott, C.; Planavsky, N. J.; Bates, S. M.; Wing, B. A.; Lyons, T. W.

2011-12-01

68

Age constraints on felsic intrusions, metamorphism and gold mineralisation in the Palaeoproterozoic Rio Itapicuru greenstone belt, NE Bahia State, Brazil  

USGS Publications Warehouse

U-Pb sensitive high resolution ion microprobe mass spectrometer (SHRIMP) ages of zircon, monazite and xenotime crystals from felsic intrusive rocks from the Rio Itapicuru greenstone belt show two development stages between 2,152 and 2,130 Ma, and between 2,130 and 2,080 Ma. The older intrusions yielded ages of 2,152??6 Ma in monazite crystals and 2,155??9 Ma in zircon crystals derived from the Trilhado granodiorite, and ages of 2,130??7 Ma and 2,128??8 Ma in zircon crystals derived from the Teofila??ndia tonalite. The emplacement age of the syntectonic Ambro??sio dome as indicated by a 2,080??2-Ma xenotime age for a granite dyke probably marks the end of the felsic magmatism. This age shows good agreement with the Ar-Ar plateau age of 2,080??5 Ma obtained in hornblendes from an amphibolite and with a U-Pb SHRIMP age of 2,076??10 Ma in detrital zircon crystals from a quartzite, interpreted as the age of the peak of the metamorphism. The predominance of inherited zircons in the syntectonic Ambro??sio dome suggests that the basement of the supracrustal rocks was composed of Archaean continental crust with components of 2,937??16, 3,111??13 and 3,162??13 Ma. Ar-Ar plateau ages of 2,050??4 Ma and 2,054??2 Ma on hydrothermal muscovite samples from the Fazenda Brasileiro gold deposit are interpreted as minimum ages for gold mineralisation and close to the true age of gold deposition. The Ar-Ar data indicate that the mineralisation must have occurred less than 30 million years after the peak of the metamorphism, or episodically between 2,080 Ma and 2,050 Ma, during uplift and exhumation of the orogen. ?? Springer-Verlag 2006.

Mello, E. F.; Xavier, R. P.; McNaughton, N. J.; Hagemann, S. G.; Fletcher, I.; Snee, L.

2006-01-01

69

Early Proterozoic (2.0 GA) Phosphorites from Pechenga Greenstone Belt and Their Origin  

NASA Technical Reports Server (NTRS)

The period of 2500-2000 Ma is heralded by several other hallmark events, including onset and decline of the greatest positive excursion of Beta13Ccarb (Lomagundi-Jatuli Paradox), development of a significant seawater sulphate reservoir, abundant deposition of anomalously organic matter (OM)-rich sediments, the oldest known significant petroleum deposits (Shunga Event), and the appearance of first known marine phosphorites at 2000 Ma as reported here. They occur as numerous rounded, soft-deformed, clasts in fine-pebble intra-formational conglomerates, forming two separate c. 200 m-thick turbidite fans within the 1000 m-thick OM- and sulphide-rich turbiditic greywackes of the Pilgujaervi Formation in the Pechenga Greenstrone Belt, NW Russia. Carbonate-fluorapatite is the main mineral in the phosphorite clasts. OM, framboidal and micronodular pyrite as well as inclusions of quartz and chlorite are additional components. Many clasts show microlayering with a variable degree of soft-deformation, implying that they were derived from non-lithified, bedded phosphorites. Numerous samples revealed diverse microbial microstructures interpreted as cyanobacterial mats consisting of filamentous (1-3 micrometer in diameter, 20 micrometers in length), coccoidal (0.8-1.0 micrometers) and ellipsoidal or rod-shaped microfossils (0.8 micrometers in diameter, around 2 micrometers in length) which morphologically resemble modern Microcoleus and Syphonophycus, Thiocapsa, and Rhabdoderma, respectively, reported from alkaline or saline environments. No principle differences have been found between microfossils described from Cambrian and Phanerozoic and the 2000 Ma phosphorites. The sequence of the early Palaeoproterozoic events which point to a significant oxidation of the hydrosphere, now including formation of phosphorites and change in the phosphorous cycle, mimics the sequence which was repeated once again at the Neoproterozoic-Cambrian transition, implying that oxidation of the terrestrial atmosphere-hydrosphere system experienced an irregular cyclic development.

Rozanov, A. Yu.; Astafieva, M. M.; Melezhik, V. A.; Hoover, R. B.; Lepland, I.

2007-01-01

70

Metallogeny of precious and base metal mineralization in the Murchison Greenstone Belt, South Africa: indications from U-Pb and Pb-Pb geochronology  

NASA Astrophysics Data System (ADS)

The 3.09 to 2.97 Ga Murchison Greenstone Belt is an important metallotect in the northern Kaapvaal Craton (South Africa), hosting several precious and base metal deposits. Central to the metallotect is the Antimony Line, striking ENE for over 35 km, which hosts a series of structurally controlled Sb-Au deposits. To the north of the Antimony Line, hosted within felsic volcanic rocks, is the Copper-Zinc Line where a series of small, ca. 2.97 Ga Cu-Zn volcanogenic massive sulfide (VMS)-type deposits occur. New data are provided for the Malati Pump gold mine, located at the eastern end of the Antimony Line. Crystallizations of a granodiorite in the Malati Pump Mine and of the Baderoukwe granodiorite are dated at 2,964 ± 7 and 2,970 ± 7 Ma, respectively (zircon U-Pb), while pyrite associated with gold mineralization yielded a Pb-Pb age of 2,967 ± 48 Ma. Therefore, granodiorite emplacement, sulfide mineral deposition and gold mineralization all happened at ca. 2.97 Ga. It is, thus, suggested that the major styles of orogenic Au-Sb and the Cu-Zn VMS mineralization in the Murchison Greenstone Belt are contemporaneous and that the formation of meso- to epithermal Au-Sb mineralization at fairly shallow levels was accompanied by submarine extrusion of felsic volcanic rocks to form associated Cu-Zn VMS mineralization.

Jaguin, J.; Poujol, M.; Boulvais, P.; Robb, L. J.; Paquette, J. L.

2012-10-01

71

Tectonic evolution of the Oudalan-Gorouol greenstone belt in NE Burkina Faso and Niger, West African craton.  

NASA Astrophysics Data System (ADS)

The Oudalan-Gorouol Greenstone Belt (OGGB) forms part of the Palaeoproterozoic as the Baoulé-Mossi domain of the West African Craton (WAC) and hosts gold deposits at Essakane, Gossey, Korizena, and Falagountou in NE Burkina Faso, and Kossa goldfield in Niger. The Birimian supracrustal sequences in the OGGB are dominated by meta-volcanoclastic greywacke intercalated meta-conglomerate, siltstone and shale, carbonate (dolomite) and volcanic units pillow basalts). The belt is surrounded by plutonic rocks including granite, TTG suite granitoids and granite gneiss. The sequences where subjected to two phases of deformation, and several phases of contact metamorphosed to hornblende-hornfels facies during emplacement of pyroxenite-gabbro-norite, granodiorite-tonalite and gabbro dykes and porphyritic sills. The OGGB is bounded and/or crosscut by several major NNE to NE-trending shear zones including the steeply east-dipping Markoye Shear Zone (western margin of the OGGB), Tin Takanet-Bellekcire Shear Zone, Dori Shear Zone, Kargouna Shear Zone, Takabougou Shear Zone, and Bom Kodjelé Shear Zone (transects the centre of the OGGB). The structures were readily identified using LANDSAT, Aster, aeromagnetic and RTP magnetic data, with follow-up strategic mapping, highlighting the value of interpreting geophysical and remotely sensed data in regional mapping in Burkina Faso and Niger. Structural studies completed in 2007 adjacent to the Essakane gold mine indicated that the NE-trending, first-order crustal-scale Markoye Shear Zone (MSZ) has undergone at least two phases of reactivation concomitant to two phases of regional deformation (Tshibubudze et al., 2009). The first phase of deformation, D1, resulted in the formation of NNW-NW trending folds and thrusts during dextral-reverse displacement on the MSZ. The deformation predates the Eburnean Orogeny is termed the Tangaean Event (meaning low hills in the Moré language of Burkina Faso) and is tentatively dated at ca. 2170-2130 Ma (Hein, 2009). D2 involved a period of SE-NW crustal shortening and sinistral-reverse displacement on the MSZ, and is correlated to the Eburnean Orogeny ~2.1 Ga of Feybesse et al. (2006). Deformation in D2 is characterised by NE-trending regional folds (F2) and a pervasive NE-trending foliation (S2-C to S2). Since 2007 an identical tectonic history has been established for a number of shear zones in the OGGB including the north-trending Kargouna Shear Zone, which is subtended by NW- and NE-trending shears. However the metamorphic grade and mineral assemblages vary from one shear zone to the next. Structural studies completed adjacent to the Dori batholith have indicated that the MSZ forms a shear complex that was active during pluton emplacement. However, the MSZ has two main branches that join at the location of a mylonite zone located north west of Essakane. Southwest of Essakane, a NW-trending mylonite zone crosscuts the Dori batholith and near the village of Kargouna, which is situated southeast of Essakane, the Kargouna shear crosscuts and deforms the Dori batholith. It is thus likely that the Dori batholith was emplacement prior to D1 in the OGGB. Gold mineralization in the OGGB is generally hosted in the hanging-wall of NE-trending faults and or NW-trending folds in metasiltstone-sandstone-shale sequences. Nkuna (2009) concluded that the deposits can be classified as orogenic gold deposits under the sub-class of "intrusion related" due to their proximity to plutonic masses, which concurs with geophysical studies for the OGGB. References: Feybesse, J.L., Billa, M., Guerrot, C., Duguey, E., Lescuyer, J.L., Milési, J.P., Bouchot, V., 2006. The Palaeoproterozoic Ghanaian province: Geodynamic model and ore controls, including regional stress modelling. Precambrian Research 149, 149-196. Hein, K.A.A., 2009 (In press). Structural chronologies in the Goren Greenstone belt (Burkina Faso); Implications for West African tectonics. Journal of African Earth Sciences. Tshibubudze, A., Hein, K.A.A., Marquis, P. 2009. The Markoye Shear Zone in NE Burkina Fas

Tshibubudze, Asinne; Hein, Kim A. A.

2010-05-01

72

Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa.  

PubMed

Although plate tectonics is the central geological process of the modern Earth, its form and existence during the Archaean era (4.0-2.5 Gyr ago) are disputed. The existence of subduction during this time is particularly controversial because characteristic subduction-related mineral assemblages, typically documenting apparent geothermal gradients of 15 degrees C km(-1) or less, have not yet been recorded from in situ Archaean rocks (the lowest recorded apparent geothermal gradients are greater than 25 degrees C km(-1)). Despite this absence from the rock record, low Archaean geothermal gradients are suggested by eclogitic nodules in kimberlites and circumstantial evidence for subduction processes, including possible accretion-related structures, has been reported in Archaean terrains. The lack of spatially and temporally well-constrained high-pressure, low-temperature metamorphism continues, however, to cast doubt on the relevance of subduction-driven tectonics during the first 1.5 Gyr of the Earth's history. Here we report garnet-albite-bearing mineral assemblages that record pressures of 1.2-1.5 GPa at temperatures of 600-650 degrees C from supracrustal amphibolites from the mid-Archaean Barberton granitoid-greenstone terrain. These conditions point to apparent geothermal gradients of 12-15 degrees C-similar to those found in recent subduction zones-that coincided with the main phase of terrane accretion in the structurally overlying Barberton greenstone belt. These high-pressure, low-temperature conditions represent metamorphic evidence for cold and strong lithosphere, as well as subduction-driven tectonic processes, during the evolution of the early Earth. PMID:16885983

Moyen, Jean-François; Stevens, Gary; Kisters, Alexander

2006-08-01

73

The Asama igneous complex, central Japan: An ultramafic-mafic layered intrusion in the Mikabu greenstone belt, Sambagawa metamorphic terrain  

NASA Astrophysics Data System (ADS)

The Asama igneous complex comprises layered mafic and ultramafic plutonic rocks exposed over about 500×6000 m in the Mikabu greenstone belt, Sambagawa metamorphic terrain of Mie Prefecture; its margins terminate by faults, and there is no trace of chilled rocks. The exposed layered sequence is about 460 m thick, and includes dunite, plagioclase wehrlite, olivine gabbro and two-pyroxene gabbro. The crystallization sequence of essential cumulus minerals is olivine, followed by plagioclase and clinopyroxene together, and finally the appearance of orthopyroxene. Olivine systematically varies in composition from Fo 89 to Fo 78 with stratigraphic height in the lower to middle portion of the layered sequence. The composition of clinopyroxene changes from Ca 49Mg 46Fe 5 to Ca 40Mg 47Fe 13 upward in the layered sequence; cumulus orthopyroxene, which occurs at the top of the exposed layered sequence, has a composition of Ca 2Mg 74Fe 24. Cumulus chromite occurs as disseminated grains in peridotitic rocks, and tends to increase its {Fe3+}/{(Cr+Al+Fe 3+) } ratio with stratigraphic height. The most aluminous chromite [ {Cr}/{(Cr+Al)} = 0.48 ] occurs in dunite that crystallized shortly before plagioclase began to separate as an essential phase. The {Cr}/{(Cr+Al)} ratio of the most aluminous chromite, coupled with the crystallization order of essential minerals, suggests that the Asama parental magma was moderately enriched in plagioclase and clinopyroxene components in the normative mineral diagram plagioclase-clinopyroxene-orthopyroxene. It was similar to a Hawaiian tholeiite and different from the Bushveld and Great "Dyke" parental magmas that were more enriched in orthopyroxene component; it also differed from mid-oceanic ridge basalts that are more depleted in the orthopyroxene component. The Asama clinopyroxene and chromite show characteristically high TiO 2 contents and are also similar to those in Hawaiian tholeiites. The Asama igneous complex probably resulted from the crystallization of a magma of a Hawaiian (oceanic-island) tholeiite composition and formed in an oceanic island regime.

Agata, T.

1994-11-01

74

Geochemistry and petrogenesis of the granitoids of the Barberton Mountain Land, South Africa  

NASA Astrophysics Data System (ADS)

The Barberton Mountain Land, situated in the Kaapvaal craton of southern Africa, is a well preserved pre-3.0 Ga granite-greenstone terrane. The greenstone belt consists of a sequence of mafic to ultramafic lavas and metasedimentary rocks emplaced/deposited between 3.5 and 3.2 Ga. The granitoid rocks were emplaced over a 500 Myr time-span and can be divided into two suites. The TTG suite (emplaced ca 3.5 - 3.2 Ga) contains tonalites, trondhjemites and granodiorites; and the GMS suite (emplaced ca 3.2 - 3.1 Ga) includes granites, monzogranites and a small syenite-granite complex. Geochemically, the TTGs are typically low- to medium-K, metaluminous I-type granites, Their chondrite-normalised rare-earth-element (REE) patterns show two trends. The majority of plutons are LREE-enriched, HREE-depleted and with small or no Eu anomalies, whilst the Steynsdorp and Doornhoek plutons are relatively HREE-undepleted with significant Eu anomalies. Nd isotope analyses show that the 3.4 Ga TTGs have positive ?Nd values (0 to +3.7), indicative of depleted-mantle sources, similar to the oldest greenstone belt formations (the Onverwacht). In contrast, the 3.2 Ga TTGs have negative ?Nd, suggesting crustal or enriched-mantle input into the magmas. The GMS rocks, on the other hand, are medium- and high-K metaluminous I-type rocks. They display two dominant REE patterns. Medium-K GMS rocks (the Dalmein and portions of Heerenveen) are LREE-enriched, HREE-depleted and have no Eu-anomalies, whereas, the high-K GMSs (Heerenveen, Mpuluzi and Boesmanskop) are relatively HREE-enriched with negative Eu anomalies. Positive and negative ?Nd values (-4.4 to +4.8) for the Boesmanskop Syenite suggests depleted-mantle and crustal signatures. The ?Nd and REE patterns, in particular, provide insights into the compositions of potential source rocks and restites for the TTG and GMS suites. Since HREEs and Eu are readily accommodated in garnet and plagioclase, respectively, their depletion suggests the presence of these minerals in the restite. For the TTG suite, we therefore suggest a garnet-rich amphibolitic or eclogitic depleted-mantle source at a depth > 40 km. This has been confirmed by experimental work constraining the stability of garnet in the trondhjemite compositions, and at magmatic temperatures, to a pressure of 15.24 ± 0.5 kbar corresponding to a depth of 54.9 ± 1.8 km. In contrast, the GMS suite most probably had a plagioclase-rich, garnet-poor source that may be a mixture of depleted-mantle and crustal materials. Tectonically, the Barberton area is dominated by two episodes of terrane accretion at ˜3.5 and 3.2 Ga, the ages of TTG magmatism. This compressional tectonic regime, coupled with the results of experimental work on the partial melting of greenstone type material leads us to suggest basaltic amphibolites of the greenstone sequences as likely source materials for the TTGs. The likely source rocks for the GMS suite, however, are not so easily constrained. The chemistry and ?Nd values of the Boesmanskop syenite suggest a hybrid mantle-crustal source. This type of hybrid source might also explain the features of the monzogranitic batholiths. Close associations between syenite and monzogranites are common, particularly in post-orogenic extensional/transtensional settings. Although extensional activity has not been documented in Barberton, ˜3.1 Ga strike-slip activity has. A post orogenic thinning of the crust might explain the production of large voluminous monzogranite batholiths and the passive nature of their intrusion dynamics.

Yearron, L.; Clemens, J.; Stevens, G.; Anhaeusser, C.

2003-04-01

75

Early Archean spherule beds of possible impact origin from Barberton, South Africa: A detailed mineralogical and geochemical study  

NASA Technical Reports Server (NTRS)

The Barberton Greenstone belt is a 3.5- to 3.2-Ga-old formation situated in the Swaziland Supergroup near Barberton, northeast Transvaal, South Africa. The belt includes a lower, predominantly volcanic sequence, and an upper sedimentary sequence (e.g., the Fig Tree Group). Within this upper sedimentary sequence, Lowe and Byerly identified a series of different beds of spherules with diameters of around 0.5-2 mm. Lowe and Byerly and Lowe et al. have interpreted these spherules to be condensates of rock vapor produced by large meteorite impacts in the early Archean. We have collected a series of samples from drill cores from the Mt. Morgan and Princeton sections near Barberton, as well as samples taken from underground exposures in the Sheba and Agnes mines. These samples seem much better preserved than the surface samples described by Lowe and Byerly and Lowe et al. Over a scale of just under 30 cm, several well-defined spherule beds are visible, interspaced with shales and/or layers of banded iron formation. Some spherules have clearly been deposited on top of a sedimentary unit because the shale layer shows indentions from the overlying spherules. Although fresher than the surface samples (e.g., spherule bed S-2), there is abundant evidence for extensive alteration, presumably by hydrothermal processes. In some sections of the cores sulfide mineralization is common. For our mineralogical and petrographical studies we have prepared detailed thin sections of all core and underground samples (as well as some surface samples from the S-2 layer for comparison). For geochemical work, layers with thicknesses in the order of 1-5 mm were separated from selected core and underground samples. The chemical analyses are being performed using neutron activation analysis in order to obtain data for about 35 trace elements in each sample. Major elements are being determined by XRF and plasma spectrometry. To clarify the history of the sulfide mineralization, sulfur isotopic compositions are being determined.

Koeberl, Christian; Reimold, Wolf Uwe; Boer, Rudolf H.

1992-01-01

76

Ion microprobe zircon U Pb dating of the late Archaean metavolcanics and associated granites of the Musoma-Mara Greenstone Belt, Northeast Tanzania: Implications for the geological evolution of the Tanzania Craton  

NASA Astrophysics Data System (ADS)

Ion microprobe zircon U-Pb ages from metavolcanic and associated granitic rocks of the late Archaean Musoma-Mara Greenstone Belt (MMGB) of northeast Tanzania reveal that the oldest mafic volcanism in the belt occurred at 2676-2669 Ma followed by felsic volcanism at ˜2668 Ma. The felsic volcanism was coeval with the emplacement of the oldest pulse of massive granitoids that is dated at 2668 Ma. The youngest volcanic episode, represented by a volcanic horizon in the largely sedimentary Kavirondian Supergroup that overlies the greenstone sequence with a marked unconformity, occurred at ˜2667 Ma. A younger phase of post-orogenic granites concluded the magmatic evolution of the MMGB at ˜2649 Ma. Our age data suggests that the entire volcano-sedimentary sequence in MMGB was emplaced in a relatively short time interval between ˜2676 and ˜2667 Ma. It also shows that contrary to arguments based on the degree of deformation, the foliated granites and some amphibolite rafts enclosed in them do not constitute the basement to the greenstone sequence. The data further shows that volcanism in the MMGB was younger than the ˜2820 Ma age of volcanism in the Sukumaland Greenstone Belt (SGB) to the far southwest and the ˜2720 Ma age of volcanism in the nearby Kilimafedha Greenstone Belt (KGB) to the south. The age of granitic magmatism (ca. 2.69-2.55 Ga) in the three belts was, however, largely coeval. Granitic magmatism of this age has also been reported in different parts of the Tanzania Craton suggesting that it was responsible for the late Archaean crustal growth and marks the beginning of a period of stability (or of cratonization).

Manya, Shukrani; Kobayashi, Katsura; Maboko, Makenya A. H.; Nakamura, Eizo

2006-07-01

77

Synchrotron Radiation X-Ray Fluorescence nanoanalyses of the metallome of a ~3.3 Ga-old microbial biofilm from the Barberton greenstone belt, South Africa.  

NASA Astrophysics Data System (ADS)

Combining in situ nanometer-scale techniques on the fossilized Josefsdal Chert Microbial Biofilm (JCMB) reveals a distinct vertical structural and compositional organisation: the lower part is calcified as aragonite, while the upper non-calcified kerogenous layer is characterised by up to 1% sulphur [1]. The in situ analysis of all the metals as a group represents a useful microbial fingerprint [2] and we will continue to explore it. Synchrotron Radiation X-Ray Fluorescence maps of high spatial resolution (< 0.3 µm) were recorded on a unique FIB section (15 x 10 x 3 µm3) of the JCMB. A 300 nm resolution was reached at 2500 eV on the ID21 scanning X-ray microscope (SXM) and a 120x165 (horizontal x vertical) nm at 17450 eV on ID22NI at the European Synchrotron Radiation Facility (ESRF). All maps reveal chemical heterogeneities not previously discernible by scanning the same FIB cut using micron resolution. The feasibility of high-resolution analyses with high flux on rock samples was first shown for samples that had in this respect an ideal hotspot geometry in a uniform silica matrix [3, 4]. Our FIB sample preparation ensures negligible thickness variations so quantitation of all the metals in the JCMB is presently only limited by the important intrinsic heterogeneity of the sample. Methods to deal with micrometer bulk heterogeneity have just been developed by performing redundant volumetric scans in fluorescence tomography to counterbalance the complex sample geometry [5]. An alternative methodology more adapted to the thin slice geometry is tested here. A relationship between the ratio of the Compton to Rayleigh (C-R) scatterings and the average atomic number (Zave), only established with unpolarized X-rays [6], was measured using fully polarized synchrotron beams [7]. C-R peaks measured on thick Astimex standards (1 mm) and those calculated from Monte-Carlo simulations of thick and thin (100 µm and 1 µm) samples having the same compositions were analyzed using a version of the PyMCA software [8] specially optimised for this purpose. The empirical relations of the type Zave = a•(C/R)b obtained for the three analyses sets provide a comprehensive set of calibrations suitable for any sample of any thickness. On the basis of these calibrations, we inferred positions and concentrations of undetected low-Z phases in the JCMB and further corrected the concentrations of the detected metals in the organic phases. 1. Westall F., et al., 2011. Earth & Planet. Sci. Lett., 310, 468-479. 2. Zerkle A L., et al., 2005. Am. J. Science, 305, 467-502. 3. Westphal A. J., et al., 2010. AIP Conference Proceedings, 1221, 131-138. 4. Bleuet P., et al., 2008. App. Phys. Lett., 92, 213111-1-3. 5. Golosio B., et al., 2003. Appl. Phys., 94, 145-157. 6. M. Haschke, 2003. PhD dissertation, T.U. Berlin. 7. Simionovici A. S., et al., 2010. Proceedings of the Meteoritical Society Conference, N.Y., USA. 8. Solé V.A., et al., 2006, Elsevier, 62, 63-68.

Hubert, A.; Lemelle, L.; Salome, M.; Cloetens, P.; Westall, F.; Simionovici, A.

2012-04-01

78

Implications of in situ calcification for photosynthesis in a ~3.3 Ga-old microbial biofilm from the Barberton greenstone belt, South Africa  

E-print Network

1 Implications of in situ calcification for photosynthesis in a ~3.3 Ga-old microbial biofilm from microbial biofilm Calcification probably due to the activities of a photosynthetic consortium of microorganisms within the biofilm including heterotrophic sulphur reducing bacteria Preservation

Paris-Sud XI, Université de

79

Unravelling the Maggie Hays and Emily Ann nickel sulphide deposits via a multidisciplinary study of the Archaean Lake Johnston Greenstone Belt, Yilgarn Craton, Western Australia.  

NASA Astrophysics Data System (ADS)

In order to better understand the architecture and structural evolution of the Archaean Lake Johnston Greenstone Belt and predict, the distribution of remobilized magmatic ultramafic nickel-sulphide mineralization in the belt, a multidisciplinary study has been carried out on the central area of the greenstone belt around the Maggie Hays and Emily Ann nickel-sulphide deposits. The nickel-sulphide deposits are hosted in a sequence of amphibolite facies rocks, severely affected by metamorphic and magmatic events. Geochronology, structural and metamorphic petrology and 3D geological modelling have been undertaken. Through a common georeferencing using Geomodeller 3D modelling software, all available data (geological map, interpretative cross-sections, drill hole and structural information) have been integrated into a 3D model to constrain the thickness of the lithologies and their geometry. Applying the THERMOCALC software coupled to the analysis of textural relationships between the main metamorphic phases, the peak P-T conditions were estimated from garnet rims and matrix minerals. The P-T evolution was deduced from garnet core compositions. The U-Pb SHRIMP method on monazite was utilized to constrain the time parameter of the P-T-t path. Two major thermal events have been inferred from the field relationships. The D1 event was part of regional metamorphism associated with a strong NNE-SSW shortening. The D1 event is associated with the development of kilometre-scale recumbent folds currently preserved at the Emily Ann Ni-deposit during top-to-the-NNE transport. A 2634 +/- 4.6 Ma SHRIMP age of folded dykes in the deposit provides an upper age limit on the D1 event. During this first event, massive nickel sulphides were mechanically remobilized into major fold hinges. The D2 event was associated with peak metamorphic temperatures, and was linked to the emplacement of the granite intrusions into the belt. The D2 event is characterized in the field by an intense top-to-the-SSE shearing. This deformation has substantially remobilized the massive nickel sulphide ore. Garnet-bearing pegmatitic intrusions that cross cut the ductile fabrics associated with peak metamorphism are common at the Maggie Hays deposit, and provide a lower U-Pb SHRIMP age constraint on the D2 event of 2631 +/- 2.9 Ma. The intense shearing observed occurred at upper amphibolite facies, and is inferred to be a key component of massive sulphide remobilization. The studied samples reached metamorphic peak conditions of 596-678 +/- 65 °C and 5-7 +/-2.1 kbars during D2. The combination of different applied approaches is helping to build a better understanding of stratigraphic and structural relationships in the greenstone belt and is helping to develop new exploration targets. Key words: Yilgarn craton, SHRIMP U-Pb dating, metamorphic petrology, 3D modelling.

Joly, A.; Miller, J.; Stott, C.; McCuaig, T.; Duguet, M.

2008-12-01

80

Environmental arsenic contamination and its health effects in a historic gold mining area of the Mangalur greenstone belt of Northeastern Karnataka, India.  

PubMed

This report summarizes recent findings of environmental arsenic (As) contamination and the consequent health effects in a community located near historic gold mining activities in the Mangalur greenstone belt of Karnataka, India. Arsenic contents in water, hair, nail, soil and food were measured by FI-HG-AAS. Elemental analyses of soils were determined by ICP-MS (inductively coupled plasma-mass spectrometry). Of 59 tube-well water samples, 79% had As above 10 ?g L(-1) (maximum 303 ?g L(-1)). Of 12 topsoil samples, six were found to contain As greater than 2000 mg kg(-1) possibly indicating the impact of mine tailings on the area. All hair and nail samples collected from 171 residents contained elevated As. Arsenical skin lesions were observed among 58.6% of a total 181 screened individuals. Histopathological analysis of puncture biopsies of suspected arsenical dermatological symptoms confirmed the diagnosis in three out of four patients. Based on the time-course of As-like symptoms reported by the community as well as the presence of overt arsenicosis, it is hypothesized that the primary route of exposure in the study area was via contaminated groundwater; however, the identified high As content in residential soil could also be a significant source of As exposure via ingestion. Additional studies are required to determine the extent as well as the relative contribution of geologic and anthropogenic factors in environmental As contamination in the region. This study report is to our knowledge one of the first to describe overt arsenicosis in this region of Karnataka, India as well as more broadly an area with underlying greenstone geology and historic mining activity. PMID:23228450

Chakraborti, Dipankar; Rahman, Mohammad Mahmudur; Murrill, Matthew; Das, Reshmi; Siddayya; Patil, S G; Sarkar, Atanu; Dadapeer, H J; Yendigeri, Saeed; Ahmed, Rishad; Das, Kusal K

2013-11-15

81

Brazil's premier gold province. Part II: geology and genesis of gold deposits in the Archean Rio das Velhas greenstone belt, Quadrilátero Ferrífero  

NASA Astrophysics Data System (ADS)

Orogenic, gold deposits are hosted by rocks of the Archean Rio das Velhas greenstone belt in the Quadrilátero Ferrífero region, Minas Gerais state, Brazil, one of the major gold provinces in the world. The gold deposits occur at the base of the mafic-ultramafic succession, with the most important orebodies controlled by E-W-striking, strike-slip faults. The main mineralization styles are (1) structurally controlled, sulfide replacement zones in banded iron formation (BIF); (2) disseminated sulfide minerals and gold in hydrothermally altered rocks along shear zones; and (3) auriferous quartz-carbonate-sulfide veins and veinlets in mafic, ultramafic, and felsic volcanic rocks, and also in clastic sedimentary rocks. The most common host rocks for ore are metamorphosed oxide- and carbonate-facies banded iron (± iron-rich metachert) formations (e.g., the Cuiabá, São Bento and Raposos deposits) and the lapa seca unit, which is a local term for intensely carbonatized rock (e.g., the giant Morro Velho mine with >450 t of contained gold). Metabasalts host most of the remaining gold deposits. Mineralogical characteristics and fluid inclusion studies suggest variations in the H2O/CO2 ratio of a low-salinity, near-neutral, reducing, sulfur-bearing, ore fluid. The presence of abundant CH4-rich inclusions is related to reduction of the original H2O-CO2 fluid via interaction with carbonaceous matter in the wallrocks. Oxygen fugacity was close to that of graphite saturation, with variations likely to have been influenced by reaction with the carbonaceous matter. Carbon-rich phyllites and schists, which commonly bound ore-bearing horizons, seem to have played both a physical and chemical role in localizing hydrothermal mineral deposition. Microtextural studies indicate that gold deposition was mainly related to desulfidation reactions, and was paragenetically coeval with precipitation of arsenic-rich iron sulfide minerals. Carbon isotope data are compatible with dissolution of CO2 from pre-existing mantle-derived carbonation zones, and indicate fluids of metamorphic origin. A major episode of hydrothermal fluid introduction into different rock types caused epigenetic gold formation and wallrock alteration at about 300 to 400 °C during the late stages of regional deformation and metamorphism of the greenstone belt. The age of gold mineralization is constrained to be younger than 2,698 and perhaps closer to 2,670 Ma.

Lobato, Lydia; Ribeiro-Rodrigues, Luiz; Vieira, Frederico

2001-07-01

82

SHRIMP U-Pb, 207Pb/ 206Pb zircon dating, and Nd isotopic signature of the Umburanas greenstone belt, northern São Francisco craton, Brazil  

NASA Astrophysics Data System (ADS)

The Gavião block in the northern portion of the São Francisco craton, northeast Brazil, is one of the oldest Archean fragments of the South American platform. It underwent polycyclic evolution from very old juvenile components dated between 3400 and 3000 Ma. The studied parts of the Umburanas greenstone belt (UGB) formed over 'stable' continental crust. SHRIMP U/Pb isotopic analyses of detrital zircons from conglomeratic quartzites of the UGB's lower unit yield dates between 3335 and 3040 Ma. These dates indicate provenance from crustal materials of different ages and a maximum age of deposition as young as 3040±24 Ma (single zircon analysis) but certainly after 3147±16 Ma (three analyses). 207Pb/ 206Pb zircon evaporation analyses from a meta-andesite of the intermediate unit of the UGB yield 2744±15 Ma, which is interpreted as the time of magmatic crystallization. The Sm/Nd whole-rock systematics of three metakomatiites from the base of the lower unit indicate that they are isotopically disturbed. Additional Sm/Nd analyses of one metabasalt (lower unit) and two meta-andesites (intermediate unit) were compared with those of the country rocks. Their similarity suggests that crustal contamination processes play an important role in the formation of volcanic rocks. As a whole, the isotopic picture is in agreement with an ensialic tectonic setting of the studied parts of the UGB.

Bastos Leal, Luiz R.; Cunha, José C.; Cordani, Umberto G.; Teixeira, Wilson; Nutman, Allen P.; Menezes Leal, Angela B.; Macambira, Moacir J. B.

2003-01-01

83

Source characteristics of the ?2.5 Ga Wangjiazhuang Banded Iron Formation from the Wutai greenstone belt in the North China Craton: Evidence from neodymium isotopes  

NASA Astrophysics Data System (ADS)

Here we first present samarium (Sm)-neodymium (Nd) isotopic data for the ?2.5 Ga Wangjiazhuang BIF and associated lithologies from the Wutai greenstone belt (WGB) in the North China Craton. Previous geochemical data of the BIF indicate that there are three decoupled end members controlling REE compositions: high-T hydrothermal fluids, ambient seawater and terrigenous contaminants. Clastic meta-sediment samples were collected for major and trace elements studies in an attempt to well constrain the nature of detrital components of the BIF. Fractionated light rare earth elements patterns and mild negative Eu anomalies in the majority of these meta-sedimentary samples point toward felsic source rocks. Moreover, the relatively low Th/Sc ratios and positive ?Nd(t) values are similar to those of the ?2.5 Ga granitoids, TTG gneisses and felsic volcanics in the WGB, further indicating that they are derived from less differentiated terranes. Low Chemical Index of Weathering (CIW) values and features in the A-CN-K diagrams for these meta-sediments imply a low degree of source weathering. Sm-Nd isotopes of the chemically pure BIF samples are characterized by negative ?Nd(t) values, whereas Al-rich BIF samples possess consistently positive ?Nd(t) features. Significantly, the associated supracrustal rocks in the study area have positive ?Nd(t) values. Taken together, these isotopic data also point to three REE sources controlling the back-arc basin depositional environment of the BIF, the first being seafloor-vented hydrothermal fluids (?Nd(t) < -2.5) derived from interaction with the underlying old continental crust, the second being ambient seawater which reached its composition by erosion of parts of the depleted landmass (likely the arc) (?Nd(t) > 0), the third being syndepositional detritus that received their features by weathering of a nearby depleted source (likely the arc) (?Nd(t) > 0).

Wang, Changle; Zhang, Lianchang; Dai, Yanpei; Li, Wenjun

2014-10-01

84

Early Cambrian Post-collisional volcanosedimentary Rey Bouba greenstone belt in northern Cameroun: LA-MC-ICP-MS U-Pb geochronology and implications for the geodynamic evolution of the Central African Fold Belt (CAFB).  

NASA Astrophysics Data System (ADS)

The Rey Bouba Greenstone Belt (RBGB) is a greenschist volcanosedimentary basin representing the youngest accretion event that characterized the geodynamic evolution of the CAFB of Northern Cameroon. LA-MC-ICP-MS U-Pb detrital zircon data indicate that both older PP to MP and younger NP to Early Cambrian sources from ca 2000 to ca 540 Ma, with main provenance being zircon grains from Cryogenian igneous rocks (between ca 850 and ca 650 Ma) were involved in the formation of the RBGB basin. Considering the age of metamorphism inferred from high pressure granulites at ca 600 Ma within the CAFB of northern Cameroon as the most direct evidence for the timing of continental collision, we conclude that the deformation associated with migmatites and post-collisional granites which fed the Rey Bouba basin mostly with NP zircon lasts until post 540 Ma, in correlation with the final amalgamation of the Gondwana Supercontinent during Latest Neoproterozoic-Earliest Cambrian. Therefore, the RBGB may represent the youngest post-collisional metavolcanosedimentary basin within the CAFB.

Bouyo, Merlain

2014-05-01

85

An Early Shelter for Life on Earth? S and O Isotope Evidence From the Nuvvuagittuq Greenstone Belt, Northeastern Superior Province, Canada  

NASA Astrophysics Data System (ADS)

The Nuvvuagittuq Greenstone Belt (NGB,) is one of Earth's oldest Eoarchean volcano-sedimentary suites, and was emplaced prior to 3.75 Ga (Cates and Mojzsis, S.J. 2007), and likely as early as 4.28 Ga (O'Neil et al. 2008). As revealed by recent detailed mapping, the NGB geology is dominated by cummingtonite-bearing amphibolites (formerly called Faux-amphibolite, (O'Neil et al. 2008)) and a series of conformable gabbroic and ultra mafic sills. Minor horizons in the belt include banded iron formations (BIF) with cm-scale quartz-rich and magnetite-rich laminations, and a pyrite-bearing quartzite in gradational contact with the BIF. These rocks and may represent the oldest remains of the sedimentary record on Earth. We performed multiple O-isotope measurements of individual minerals (quartz, garnet, amphibole and magnetite) from three NGB lithologies (BIF, faux amphibolites and quartzite). In BIF samples, ?18O values cover a narrow range (from 1.36 per mil magnetite to 4.98 per mil with one outlier at 9.99 per mil), whereas silicate minerals in the faux reveal a more scattered range that is more depleted in light isotopes (7.77 per mil ? ?18O ? 13.38 per mil). One quartzite sample has also been analyzed and reveals the most 16O-depleted composition yet measured from the belt (?18O = 15.44 per mil). The ?17O and ?18O values from these samples define a fractionation line for multiple oxygen isotopes with a slope of 0.528 ± 0.004 (MSWD = 0.47), statistically indistinguishable from the slope (0.524 +± 0.002) of the Archean Terrestrial Fractional Line (TFL) determined from other Archean rocks and minerals. These results show no evidence for the drastic O-isotope heterogeneity that would likely accompany the late heavy bombardment of the Earth-Moon system. We also performed multiple S-isotope ratio measurements (?34S, ?33S, ?36S) in samples covering the entire lithological suite of the NGB. Samples from the quartzite and BIF display a narrow range of ?34S values (0.8 per mil ? ?34S ? 3.3 per mil), in good agreement with ranges reported so far from early Archean sediments. The same samples exhibit non-zero ?33S and ?36S values (respectively ranging from 0.18 to 2.27 per mil and from -2.9 per mil to -0.6 per mil) that are negatively correlated (?36S ~ -0.9 ?33S) and conform to the linear array that characterizes most of the Archean Eon. Finally, the NGB BIF and silica formation reveal a tight correlation between ?33S and ?34S values (?33S ~ 0.9 ?34S) that matches previous observations from Neoarchean and Paleoarchean samples. In previous studies, the ?34S - ?33S - ?36S correlations observed here have been taken to reflect both a restricted chemistry of the atmosphere and a dynamic microbiologically-dominated sulfur cycle. Taken together, and considering the age of the NGB, the S- and O-isotope results suggest that conditions conducive to life on Earth were established very early in Earth's history. Either there was apparently no significant perturbation of the early Earth system by the late heavy bombardment, or the rocks of the NGC record a time interval that was not affected by this dramatic event. This talk will explore the implications of these two possibilities for the early establishment of a stable environment suitable for the emergence of life.

Thomassot, E.; O'Neil, J.; Francis, D.; Cartigny, P.; Rumble, D.; Wing, B.

2009-05-01

86

Geochemical characteristics of aluminum depleted and undepleted komatiites and HREE-enriched low-Ti tholeiites, western Abitibi greenstone belt: A heterogeneous mantle plume-convergent margin environment  

NASA Astrophysics Data System (ADS)

A compositionally diverse suite of komatiites, komatiitic basalts, and basalts coexist in the Tisdale volcanic assemblage of the late-Archean (˜2.7 Ga) Abitibi greenstone belt. The komatiites are characterized by a spectrum of REE patterns, from low total REE contents (9 ppm) and pronounced convex-up patterns to greater total REE (18 ppm) and approximately flat-distributions. Thorium and niobium are codepleted with LREE. Komatiites with the most convex-up patterns have low Al 2O 3 (4.7 wt%) contents and Al 2O 3/TiO 2(12) ratios; they are interpreted to be the Al-depleted variety of komatiite derived from a depleted mantle source. Those komatiites and komatiitic basalts with flatter REE patterns are characterized by greater Al 2O 3 (7.0 wt%) and near chondritic Al 2O 3/TiO 2 (20) ratios; they are interpreted to be Al-undepleted komatiites generated from trace element undepleted mantle. For the komatiites and komatiitic basalts collectively, Gd/Ybn ratios are negatively correlated with La/Smn, but positively with MgO and Ni. The spectrum of patterns is interpreted as mixing between Al, HREE, Y-depleted, and Sc-depleted komatiites and Al-undepleted komatiites in a heterogeneous mantle plume. Auminum-depleted komatiites are characterized by negative Zr and Hf anomalies, consistent with majorite garnet-liquid D's for HFSE and REEs, signifying melt segregation at depths of >400 km. Tisdale Al-undepleted komatiites and komatiitic basalts have small negative to zero Zr(Hf)/MREE fractionation, signifying melt segregation in or above the garnet stability field. Collectively, the komatiites have correlations of Zr/Zr? and Hf/Hf ? with Gd/Ybn, and hence the Zr(Hf)/MREE fractionations are unlikely to have stemmed from alteration or crustal contamination. Two types of basalts are present. Type I basalts are Mg-tholeiites with near flat REE and primitive mantle normalized patterns, compositionally similar to abundant Mg-tholeiites associated with both Al-undepleted and Al-depleted komatiites in the Abitibi belt. They have absolute concentrations and ratios of most moderately and highly compatible elements comparable to N- MORB (Zr ˜79 vs. 74, Y ˜30 vs. 28, and Zr/Y = 2.4-2.9 vs. 2.6 ), but are relatively less depleted in highly incompatible elements and lack positive Nb or P anomalies. Type II basalts are relatively aluminous (Al 2O 3 ˜ 16 wt%), with high Al 2O 3/TiO 2 (24-28) ratios. They are characterized by low Th, Nb, and LREE contents at eight to ten times chondrite, with slightly convex-up LREE patterns ( La/Smn = 0.86-0.99 ), but strongly fractionated and enriched HREEs, Y, and Sc, where Gd/Ybn = 0.50-0.55 and consistently positive Zr(Hf)/MREEs anomalies. These basalts are tentatively interpreted as low-Ti tholeiites formed in a convergent margin setting with second stage melting, induced by fluids and melts enriched in incompatible elements and Zr(Hf) relative to MREEs, of a mantle source depleted during first stage melting. They are analogous to the Phanerozoic low-Ti tholeiite - boninite association. Accordingly the Tisdale volcanic sequence records a plume-convergent margin interaction. New analyses of Al-undepleted komatiites from the classical locality at Pyke Hill in Munro Township confirm the presence of small positive anomalies of P, Zr, and Hf, with Zr/Hf ratios generally < 36. These signatures are similar in spinifex and cumulate zones signifying that they are unlikely to have resulted from alteration. The data were generated by INAA and ICP-MS using both HF?HNO 3 dissolution and Na 2O 2 sinter. The lack of LREE enrichment with negative Nb, Ta, P, and Ti anomalies in any of the Tisdale or Munro komatiites confirms an intraoceanic setting for the volcanic stage of the Western Abitibi greenstone belt.

Fan, J.; Kerrich, R.

1997-11-01

87

The geology of the Morro Velho gold deposit in the Archean Rio das Velhas greenstone belt, Quadrila??tero Ferri??fero, Brazil  

USGS Publications Warehouse

The Morro Velho gold deposit, Quadrila??tero Ferri??fero region, Minas Gerais, Brazil, is hosted by rocks at the base of the Archean Rio das Velhas greenstone belt. The deposit occurs within a thick carbonaceous phyllite package, containing intercalations of felsic and intermediate volcaniclastic rocks and dolomites. Considering the temporal and spatial association of the deposit with the Rio das Velhas orogeny, and location in close proximity to a major NNW-trending fault zone, it can be classified as an orogenic gold deposit. Hydrothermal activity was characterized by intense enrichment in alteration zones of carbonates, sulfides, chlorite, white mica??biotite, albite and quartz, as described in other Archean lode-type gold ores. Two types of ore occur in the deposit: dark gray quartz veins and sulfide-rich gold orebodies. The sulfide-rich orebodies range from disseminated concentrations of sulfide minerals to massive sulfide bodies. The sulfide assemblage comprises (by volume), on average, 74% pyrrhotite, 17% arsenopyrite, 8% pyrite and 1% chalcopyrite. The orebodies have a long axis parallel to the local stretching lineation, with continuity down the plunge of fold axis for at least 4.8??km. The group of rocks hosting the Morro Velho gold mineralization is locally referred to as lapa seca. These were isoclinally folded and metamorphosed prior to gold mineralization. The lapa seca and the orebodies it hosts are distributed in five main tight folds related to F1 (the best examples are the X, Main and South orebodies, in level 25), which are disrupted by NE- to E-striking shear zones. Textural features indicate that the sulfide mineralization postdated regional peak metamorphism, and that the massive sulfide ore has subsequently been neither metamorphosed nor deformed. Lead isotope ratios indicate a model age of 2.82 ?? 0.05??Ga for both sulfide and gold mineralization. The lapa seca are interpreted as the results of a pre-gold alteration process and may be divided into carbonatic, micaceous and quartzose types. The carbonatic lapa seca is subdivided into gray and brown subtypes. Non-mineralized, gray carbonatic lapa seca forms the hanging wall to the orebodies, and is interpreted as the product of extreme CO2 metasomatism during hydrothermal alteration. This dolomitic lapa seca ranges in composition from relatively pure limestone and dolomite to silty limestone and dolomite. The brown carbonatic and micaceous lapa secas are the host rocks to gold. These units are interpreted to correspond to the sheared and hydrothermal products of metamorphosed volcaniclastic and/or volcanic rocks of varying composition from dacitic to andesitic, forming various types of schists and phyllites. The high-grade, massive sulfide orebodies occur at the base of the gray carbonatic lapa seca. Both disseminated mineralization and quartz veins are hosted by micaceous lapa seca. The data are consistent with a model of epigenetic mineralization for the lapa seca, from a hydrothermal fluid derived in part from the Archean basement or older crust material. ?? 2007 Elsevier B.V. All rights reserved.

Vial, D. S.; DeWitt, E.; Lobato, L. M.; Thorman, C. H.

2007-01-01

88

A billion years of crustal evolution recorded in the Nuvvuagittuq greenstone belt: Pb-Hf evidence for Eoarchean TTGs produced from melting of Hadean mafic crust  

NASA Astrophysics Data System (ADS)

Investigation of Earth's primitive crust is limited by the scarcity of Eoarchean/Hadean terrains. Most of these terrains are dominated by felsic Tonalite-Trondhjemite-Granodiorite (TTG) rocks. These felsic rocks however, cannot be directly produced from melting of the mantle but must instead have been derived from the melting of an older mafic precursor. Obtaining accurate ages on old terrestrial mafic rocks is challenging. The geochronology constraints on Archean mafic rocks commonly come from long-lived radiogenic isotopic systems that can be affected by younger metamorphic/metasomatic events. The short-lived 146Sm-142Nd isotopic system is less susceptible to partial resetting because 146Sm became extinct prior to ~4 Ga. The mafic rocks from the Nuvvuagittuq greenstone belt (NGB), called the Ujaraaluk unit, have 146Sm-142Nd systematics consistent with them being formed in the Hadean, between 4.3 and 4.4 Ga. This age has been challenged because the oldest U-Pb ages on zircons obtained in the NGB are ~3.8 Ga. The ~3.8 Ga zircons, however, are from trondhjemetic bands intruding the NGB and thus provide only a minimum age for the mafic rocks. The NGB is surrounded by 3.65 Ga tonalites having deficits in 142Nd suggesting derivation from an Hadean precursor such as the Ujaraaluk unit. We have now identified two additional tonalite generations dated at 3.75 Ga and 3.4-3.5 Ga suggesting a more complex thermal history for the NGB. In order to better constrain the geologic relationship between the mafic and the felsic rocks and the evolution of the NGB through time, we present whole-rock Lu-Hf data for the Nuvvuagittuq rocks as well as combined Pb-Hf analyses in zircons from a series of surrounding TTGs dated at 3.35 Ga, 3.4-3.5 Ga, 3.65 Ga and 3.75 Ga. The Lu-Hf isotopic compositions of the NGB mafic rocks have been partially reset by a Neoarchean metamorphic/metasomatic event, consistent with what is observed for the long-lived 147Sm-143Nd system. Zircons from the 3.35 to 3.65 TTGs have strongly subchondritic initial ?Hf values and display an ?Hf vs. age array consistent with their derivation from a 4.3-4.4 Ga mafic precursor. The 3.75 Ga TTGs have initial ?Hf values consistent either with derivation from the ~4.2 Ga NGB gabbros or with incorporation of more juvenile mantle-derived material. The Hf-zircon and 142Nd data for the Eoarchean NGB TTGs is consistent with their formation from the melting of the Hadean Ujaraaluk unit. The time integrated ?Hf-zircon data also is consistent with the Hf isotopic compositions of the Jack Hills zircons suggesting a similar primitive mafic precursor for the Eoarchean/Hadean TTGs forming Earth's early crust.

O'Neil, J.; Boyet, M. M.; Carlson, R. W.; Paquette, J.

2012-12-01

89

Greenstone Digital Library Software  

NSDL National Science Digital Library

Greenstone is a suite of software designed to build and distribute digital library collections. Produced by the New Zealand Digital Library Project at the University of Waikato, this innovative tool was created to "empower users, particularly in universities, libraries, and other public service institutions, to build their own digital libraries." The software consists of the Collector, which helps create new collections, modify or add to existing ones, or delete collections; and the Administration, which allows the addition of new users, summarizes the collections in the system, and gives technical information on the installation. Also included is a section comprising the Greenstone manuals, and a section that tells about the Greenstone software and where the New Zealand Digital Library Project originated. The software runs on Windows and Unix, and both source codes and binaries are available for downloading on the site.

1969-12-31

90

Platinum-group element alloy inclusions in chromites from Archaean mafic-ultramafic units: evidence from the Abitibi and the Agnew-Wiluna Greenstone Belts  

NASA Astrophysics Data System (ADS)

The paper investigates the role of primary magmatic phases in the fractionation and concentration of PGE in Archaean mafic and ultramafic systems. The composition of chromites and olivines in sulphur-poor (S < 0.6 wt%) komatiites from the Agnew-Wiluna Belt (Western Australia), and of chromite concentrated from komatiitic basalt, ferropicritic basalt and tholeiitic basalt from the Abitibi Belt (Canada) were analysed. The results of laser ablation ICP-MS analyses show that PGE-bearing alloys are not stable in crystallising komatiite and that ruthenium is soluble in chromite during crystallisation. Conversely, analyses of chromites separated from Theo’s Flow tholeiitic basalt indicate that Ir Os (±Pt) enrichments (>200 ppb) reflect the presence of PGM. Chromites from Fred’s Flow komatiitic basalt contain Ir-rich clusters, whereas Pt enrichments (>370 ppb) in Boston Creek ferropicritic basalt reflect the presence of Pt-rich compounds. The presence of PGE-bearing alloys in Theo’s Flow and Fred’s Flow is due to late S-supersaturation, whereas the presence of Pt-rich compounds in Boston Creek Flow reflects high state of melt oxidisation. The lack of PGE-bearing alloys in the olivines and chromites of komatiites can be explained by thermal instability of PGM, depletion in PGE at the mantle source, early S-supersaturation, the oxidisation conditions of the melt, or a combination of these factors.

Fiorentini, M. L.; Stone, W. E.; Beresford, S. W.; Barley, M. E.

2004-12-01

91

Insights into early Earth from Barberton komatiites: Evidence from lithophile isotope and trace element systematics  

NASA Astrophysics Data System (ADS)

Major, minor, and lithophile trace element abundances and Nd and Hf isotope systematics are reported for two sets of remarkably fresh, by Archean standards, samples of komatiitic lavas from the 3.48 Ga Komati and the 3.27 Ga Weltevreden Formations of the Barberton Greenstone Belt (BGB) in South Africa. These data are used to place new constraints on the thermal history of the early Archean mantle, on the timing of its differentiation, and on the origin and chemical nature of early mantle reservoirs and their evolution through time. Projected moderate to strong depletions of highly incompatible lithophile trace elements and water in the mantle sources of both komatiite systems, combined with the partitioning behavior of V during lava differentiation, are consistent with anhydrous conditions during generation of the komatiite magmas. Komati and Weltevreden lavas are inferred to have erupted with temperatures of ?1600 °C, and, thus, represent the hottest known lavas on Earth. The calculated mantle potential temperatures of ?1800 °C for both komatiite systems are 150-200 °C higher than those of contemporary ambient mantle. Combined, these observations are consistent with the origin of these BGB komatiite magmas in mantle plumes in the lower mantle. New Sm-Nd and Lu-Hf isotopic data allow precise determination of initial ?143Nd = +0.46 ± 0.10 and +0.50 ± 0.11 and initial ?176Hf = +1.9 ± 0.3 and +4.7 ± 0.8 for the Komati and the Weltevreden system komatiites, respectively. These positive initial values reflect prior fractionation of Sm/Nd and Lu/Hf in the mantle early in Earth history. Conversely, ?142Nd values are 0.0 ± 2.4 and +2.2 ± 4.1 for the Komati and the Weltevreden systems, respectively. These values overlap, within uncertainties, those of modern terrestrial rocks, thus, limiting the magnitudes of possible Sm/Nd fractionations generated by early Earth processes in the sources of these rocks. Combined 142,143Nd and Hf isotope and lithophile trace element systematics are consistent with formation and long-term isolation of deep-seated mantle domains with fractionated Sm/Nd and Lu/Hf at ca. 4400 Ma. These domains were likely generated as a result of crystallization of a primordial magma ocean, with Mg-perovskite and minor Ca-perovskite acting as fractionating phases. The inferred mantle domains were evidently mixed away by 2.7 Ga on the scale of mantle reservoirs sampled by late Archean komatiite lavas emplaced worldwide.

Puchtel, I. S.; Blichert-Toft, J.; Touboul, M.; Walker, R. J.; Byerly, G. R.; Nisbet, E. G.; Anhaeusser, C. R.

2013-05-01

92

Archean granite-greenstone tectonics at Kolar (South India): Interplay of diapirism and bulk inhomogeneous contraction during juvenile magmatic accretion  

NASA Astrophysics Data System (ADS)

The structural study of the Kolar greenstone belt and surrounding granite-gneiss terrains combined with U-Pb dating reveals that the middle and lower crustal tectonoplutonic pattern of the eastern Dharwar craton developed during a major magmatic accretion event between 2550 and 2530 Ma. The granite-greenstone pattern resulted from the interference of gravity-driven sagging of the greenstones (i.e., diapirism), E-W bulk inhomogeneous shortening combined with horizontal N-S stretching, and syntectonic juvenile pluton emplacement. Bulk inhomogeneous contraction is accommodated by the synchronous development of a pervasive, N-S trending vertical foliation, shallow stretching lineation, and conjugate strike-slip shear zone pattern within and outside the greenstone belt, resulting in regional horizontal pure shear deformation. The plutons around the greenstone belt record regional contraction by developing one set of strike-slip C-S fabrics of the shear zone pattern. The development of the granite-greenstone pattern was coeval and compatible with deformation during juvenile magmatic accretion, melting, and granulite metamorphism in the lower crust. The Kolar example points to a specific crustal rheology that allowed sagduction of the greenstones and regional distributed bulk inhomogeneous strain, due to mechanical homogeneity and low viscosity provided by large-scale melting during the accretion event. This example further suggests specific boundary conditions to the craton that allowed E-W inhomogeneous shortening to be accommodated by N-S stretching and spreading of the crust without significant tectonic thickening. Such tectonoplutonic pattern is specific to the Archean and may develop as a consequence of mantle plume activity in intracontinental settings.

Chardon, Dominique; Peucat, Jean-Jacques; Jayananda, Mudlappa; Choukroune, Pierre; Fanning, C. Mark

2002-06-01

93

Insights into early Earth from the Pt-Re-Os isotope and highly siderophile element abundance systematics of Barberton komatiites  

NASA Astrophysics Data System (ADS)

Highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance and Pt-Re-Os isotopic data are reported for well-preserved komatiites from the Komati and Weltevreden Formations of the Barberton Greenstone Belt in South Africa. The Re-Os data for whole-rock samples and olivine and chromite separates define isochrons with ages of 3484 ± 38 and 3263 ± 12 Ma for the Komati and Weltevreden systems, respectively. The respective initial 187Os/188Os = 0.10335 ± 15 (?187Os = +0.34 ± 0.15) and 0.10442 ± 4 (?187Os = -0.14 ± 0.04) are well within the range defined by chondritic meteorites. When considered together with the Re-Os data for late Archean komatiite systems, these data indicate that the mantle sources of most Archean komatiites evolved with essentially uniform long-term Re/Os that is well within the chondritic range. By contrast, the initial 186Os/188Os = 0.1198283 ± 9 (?186Os = -0.12 ± 0.08) and 0.1198330 ± 8 (?186Os = +0.22 ± 0.07) for the Komati and Weltevreden systems, respectively, are outside of known chondritic evolution paths, indicating that the mantle sources of these two komatiite systems evolved with fractionated time-integrated Pt/Os. The new 186,187Os isotopic data for these early Archean komatiite systems, combined with published 142,143Nd and 176Hf isotopic data for these systems, are consistent with formation and long-term isolation of deep-seated mantle domains with fractionated time-integrated Sm/Nd, Lu/Hf, and Pt/Os ratios, at ca. 4400 Ma. These domains may have been generated as a result of late-stage crystallization of a primordial magma ocean involving Mg-perovskite, Ca-perovskite and Pt-alloys acting as the fractionating phases. The inferred fractionated mantle domains were sampled by the early Archean komatiites, but were largely mixed away by 2.7 Ga, as evidenced by uniform time-integrated Sm/Nd, Lu/Hf, and Pt/Os ratios inferred for the sources of most late Archean komatiite systems. The calculated total Pt + Pd abundances present in the sources of the early Archean komatiite systems fall only 7-14% short of those present in estimates for the modern primitive mantle. These are also within the range of the total Pt + Pd abundances present in the sources of late Archean komatiite systems, indicating little change in the HSE abundances in the Archean mantle between 3.5 and 2.7 Ga. The new HSE data for the early Archean komatiite systems may implicate late accretion of HSE to the mantle prior to completion of crystallization of a final terrestrial magma ocean, followed by sluggish mixing of diverse, post-magma ocean domains characterized by variably fractionated lithophile element and HSE abundances.

Puchtel, Igor S.; Walker, Richard J.; Touboul, Mathieu; Nisbet, Euan G.; Byerly, Gary R.

2014-01-01

94

On shearing, magmatism and regional deformation in Neoarchean granite-greenstone systems: Insights from the Yilgarn Craton  

NASA Astrophysics Data System (ADS)

The structure of the Neoarchean Yilgarn Craton is dominated by craton-scale high-strain zones, mostly associated with highly-deformed elongate granitic bodies and transposed greenstone belts. These shear zones developed during widespread and prolonged magmatic activity that led to a nearly complete reworking of the felsic continental crust. The spatial, temporal and genetic relationships between such a voluminous and protracted event of crustal reworking and the development of the craton-scale shear zone network are unclear. Here, we combine new structural, geophysical and geochemical data to investigate the relationship between crustal-scale shear zones and large syntectonic plutons in the Yilgarn Craton of Western Australia. We propose that Archean granite-greenstone systems may have commonly evolved through the interaction of three fundamental geological processes: (I) emplacement of large scale syntectonic plutons; (II) activity of crustal-scale shear zones; (III) pervasive, largely syn-metamorphic polyphase deformation in greenstone belts adjacent to syntectonic plutons. We propose that the concept of “Archean regional deformation event” need to be reassessed: a regional event is probably pluton- (or batholith-) size, and the structural/metamorphic evolution of adjacent greenstone belts might have proceeded quite independently and potentially in a time-transgressive way, if those belts were not spatially related to the same syntectonic pluton.

Zibra, I.; Gessner, K.; Smithies, H. R.; Peternell, M.

2014-10-01

95

Gold mineralisation and alteration of Penakacherla schist belt, India, constraints on Archaean subduction and fluid processes  

Microsoft Academic Search

In the Dharwar Craton, southern India, gold deposits are found mostly along the six arcuate shear zones passing through late Archaean greenstone belts (2.7 Ga). One such shear zone complex extends for about 400 km within and along the Ramagiri–Hungund schist belt. The Penakacherla sector of this shear zone is excellently exposed, enabling a detailed investigation of synorogenic gold mineralisation

C. Manikyamba; S. M. Naqvi; M. Ram Mohan; T. Gnaneshwar Rao

2004-01-01

96

Greenstone: a comprehensive open-source digital library software system  

Microsoft Academic Search

This paper describes the Greenstone digital library software, a comprehensive, open-source system for the construction and presentation of information collections. Collections built with Greenstone offer effective full-text searching and metadata-based browsing facilities that are attractive and easy to use. Moreover, they are easily maintainable and can be augmented and rebuilt entirely automatically. The system is extensible: software \\

Ian H. Witten; Stefan J. Boddie; David Bainbridge; Rodger J. McNab

2000-01-01

97

Greenstone: A Comprehensive Open-Source Digital Library Software System  

Microsoft Academic Search

This paper describes the Greenstone digital library software, a comprehensive, open-source system for the construction and presentation of information collections. Collections built with Greenstone offer effective full-text searching and metadata-based browsing facilities that are attractive and easy to use. Moreover, they are easily maintainable and can be augmented and rebuilt entirely automatically. The system is extensible: software \\

Ian H. Witten; Rodger J. McNab; Stefan J. Boddie; David Bainbridge

1999-01-01

98

Age and tectonic setting of Late Archean greenstone-gneiss terrain in Henan Province, China, as revealed by single-grain zircon dating  

Microsoft Academic Search

We report precise U-Pb zircon ages for single grains of a metarhyodacite from the Late Archean Dengfeng greenstone belt in Henan Province, China, near the southern margin of the North China craton. Most grains belong to an igneous population whose U-Pb isotopic systematics define a straight line intersecting concordia at 2512 ±12Ma, and this is interpreted as the time of

Alfred Kröner; William Compston; Zhang Guo-Wei; Guo An-Lin; Wolfgang Todt

1988-01-01

99

Dynamic melting of the Precambrian mantle: evidence from rare earth elements of the amphibolites from the Nellore–Khammam Schist Belt, South India  

Microsoft Academic Search

The Nellore–Khammam Schist Belt (NKSB) in South India is a Precambrian greenstone belt sited between the Eastern Ghats Mobile Belt (EGMB) to the east and the Cratonic region to the west. The belt contains amphibolites, granite gneisses and metasediments including banded iron formations. Amphibolites occurring as dykes, sills and lenses—in and around an Archaean layered complex—form the focus of the

K. Vijaya Kumar; M. Narsimha Reddy; C. Leelanandam

2006-01-01

100

Geochemistry and petrology of greenstones from the Erdenetsogt formation, central Mongolia: New evidence for a middle Paleozoic mantle plume  

NASA Astrophysics Data System (ADS)

This research presents evidence of the plume-related formation of greenstones from the Erdenetsogt Formation (EF) hosted by Tsetserleg terrane of middle Paleozoic Hangay-Hentey accretionary complex, which is central part of the Central Asian Orogenic Belt (CAOB). Our new data can support middle Paleozoic evolution of plume-related magmatism of the paleo-oceanic plate and its accretionary processes, which significantly contributed to the continental growth of CAOB. EF is mainly made up of intensively deformed oceanic plate stratigraphy such as radiolarian/ribbon chert, red and green quartzites (metachert), fine to medium-grained sandstone, siltstone with minor amount of limestone, and some basaltic greenstones which have been discovered lately during geological mapping in the south Hangay region. The upper unit of this formation was dated by late Devonian conodonts from the chert. However, the chemistry of greenstones in this region has not been studied yet except brief study by Orolmaa (2008). The studied samples include metabasalts, dolerites, microgabbros, and occasional meta-picrites with mostly subophitic, intersertal, and partly intergranular textures. The common assembledge of phenocrysts is clinopyroxene (well-preserved in all greenstones) and plagioclase (replaced by albite). Also completely altered olivine containing relict Cr-spinel observed from metapicrite and porphyritic metabasalt. The composition of the primary clinopyroxene (augite) and Cr-spinel were analyzed by electron microprobe and bulk rock major and trace elements by XRF. On the basis of Ca +Na vs. Ti and Ca vs. Ti+Cr discrimination diagrams, clinopyroxenes display tholeiitic magma type and non-orogenic affinity. The relict spinels are 20-250 ?m in size. The Al2O3 wt.% vs. TiO2 wt.% variation of the spinels corresponds to the transitional affinity of OIB and MORB. The Cr and Mg numbers of the spinels show very limited values ranging from 55 to 68 and from 0.3 to 0.6, respectively, and implies highly depleted (high melting degree) magma compare with MORB, and more identical to spinel from Hawaiian tholeiitic basalts. From those facts, it is concluded that the Cr-spinel of greenstones may have been derived from a mantle plume source. Furthermore, notable exceptions of the Hangay greenstones are very low ratios of Nb/Zr and Zr/Y (0.05-0.08 and 0.2-0.5, respectively), whereas Hentey basalts show HIMU characteristic (Tsukada, 2006). The greenstones are slightly enriched in LREE and TiO2 (1.6-2.2 wt.%). We suggest that greenstones in Erdenetsogt formation may have been formed as plume-related oceanic island (hotspot or oceanic plateau) within paleo-oceanic plate located between the Siberian and the North China Cratons, and then accreted to the active continental margin of Siberian Craton during middle to late Paleozoic. This setting is analogous to the present southwest Pacific realm. Keywords: Hangay-Hentey accretionary complex, Erdenetsogt Formation, greenstones, clinopyroxene, Cr-spinel, mantle plume

Ganbat, E.; Ishiwatari, A.; Demberel, O.

2012-12-01

101

Source and tectono-metamorphic evolution of mafic and pelitic metasedimentary rocks from the central Quetico metasedimentary belt, Archean Superior Province  

E-print Network

the central Quetico metasedimentary belt, Archean Superior Province of Canada Franck Vallia* , Stephane to the Wabigoon subprovince to the north and Wawa greenstone belt to the south. The P-T-time path of this Archean, such as blueschist, that are common in modern accretionary prisms. Key words: Archean accretionary prism, provenance

Paris-Sud XI, Université de

102

Age of the Mulcahy Lake intrusion, northwest Ontario, and implications for the evolution of greenstone-granite terrains  

NASA Technical Reports Server (NTRS)

An investigation of zircon data from the Mulcahy Lake gabbro, a 63 sq km layered mafic intrusion in the Wabigoon subprovince of Ontario, which show that the gabbro crystallized at 2733.2 +1.0, -0.9 Ma, is considered. It is shown that the gabbro intrudes tholeiites of the Crow Lake-Savant Lake greenstone belt. Whole rock samples and mineral separates from the Mulcahy Lake intrusion are dated by Rb-Sr, Sm-Nd, and Ar-30-Ar-40 techniques. Disturbances in the system are revealed by the Rb-Sr data and an initial Sr ratio of 0.7007 for an age of 2733 Ma is indicated by samples with low Rb/Sr ratios. The age determined for the Sm-Nd data is 2744 + or 55 Ma with an epsilon Nd value of +2.6 + or - 1.2 which indicates a source region depleted in a light rare earth element. Primary hornblende is analyzed for Ar-40/Ar-39 and an age of 2703 + or - 20 is obtained. Some implications for the development of greenstone-granite belts are discussed.

Morrison, D. A.; Bogard, D. D.; Phinney, W. C.; Davis, D. W.; Wooden, J. L.; Ashwal, L. D.; Maczuga, D. E.

1985-01-01

103

Archean sedimentation and tectonics in southern Africa  

NASA Technical Reports Server (NTRS)

Sequences in the Barberton Mountain Land greenstone belt (southern Africa) were examined to determine the nature of the sedimentary rocks, their tectonic implications, and their bearing on the present large-scale structural condition of the belt. Also assessed was whether there was evidence for a significant component of shallow-water-deposited sedimentary rocks in the parent materials of the Limpopo belt. The nature of a largehigh strain zone on the southern margin of the central Limpopo belt was examined.

Kidd, W. S. F.

1984-01-01

104

Geochronological Constraints on Evolution of Singhbhum Mobile Belt and Associated Basic Volcanics of Eastern Indian Shield  

Microsoft Academic Search

The Singhbhum Mobile Belt (SMB) of the eastern Indian shield represents a roughly east-west-trending arcuate belt of folded supracrustals overlying the granite-greenstone basement of the Singhbhum-Orissa Craton along its northern, eastern and western margins and is bounded by the Chotanagpur Gneissic Complex to further north. The radiometric ages of the basement Singhbhum and equivalent granites and the intrusive anorogenic Mayurbhanj

Saumitra Misra; P. Thomas Johnson

2005-01-01

105

Precambrian Research 226 (2013) 116124 Contents lists available at SciVerse ScienceDirect  

E-print Network

of well- preserved Late Archean and Paleoproterozoic BIF. Efforts to push the understanding gained from Early Archean BIF. This study focuses on a unique occurrence of well-preserved and contextualized BIF from the Early Archean (3.2 Ga) Moodies Group, in the Barberton Greenstone Belt, South Africa

Fischer, Woodward

106

Early Life Recorded in Archean Pillow Lavas  

Microsoft Academic Search

Pillow lava rims from the Mesoarchean Barberton Greenstone Belt in South Africa contain micrometer-scale mineralized tubes that provide evidence of submarine microbial activity during the early history of Earth. The tubes formed during microbial etching of glass along fractures, as seen in pillow lavas from recent oceanic crust. The margins of the tubes contain organic carbon, and many of the

Harald Furnes; Neil R. Banerjee; Karlis Muehlenbachs; Hubert Staudigel; Maarten de Wit

2004-01-01

107

Boysagainstgirls Science doi:10.1126/  

E-print Network

Boysagainstgirls Science doi:10.1126/ science.1174705 (2009) Male cichlid fishes in East Africa South Africa's Barberton greenstone belt reveal that such currents in the core must have started by 3. When it does occur in males, it disrupts their patterning (bottom right), reducing their fitness

Kocher, Thomas D.

108

The oldest impact deposits on earth — First confirmation of an extraterrestrial component  

Microsoft Academic Search

The chromium isotopic compositions of samples from an early Archean (3.22 Ga) spherule bed (S4) from the Barberton Greenstone Belt, South Africa, are distinct from that in background rocks and other terrestrial samples. This positively confirms the presence of an extraterrestrial component in this bed and supports hypotheses of an impact origin. The source of the extraterrestrial Cr is most

Alexander Shukolyukov; Frank T. Kyte; Gtinter W. Lugmair; Donald R. Lowe; Gary R. Byerly

109

Geological Record of Life 3500 Ma Ago: Coping with the Rigors of a Young Earth during Late Accretion. Abstract Only.  

National Technical Information Service (NTIS)

Thin cherty sedimentary layers within the volcanic portions of the 3,500 to 3,300 Ma-old Onverwacht and Fig Tree Groups, Barberton Greenstone belt, South Africa, and Warrawoona Group, eastern Pilbara Block, Western Australia, contain an abundant record of...

D. R. Lowe

1989-01-01

110

Adding SOMLib capabilities to the Greenstone Digital Library System  

E-print Network

Adding SOMLib capabilities to the Greenstone Digital Library System Rudolf Mayer, Andreas Rauber. Many conventional digital library systems offer access to their collections only via full text or meta of a digital library by their content. In this paper, we present an integration of this system into the popular

Rauber,Andreas

111

Sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone terrane, western Dharwar Craton: Implications on pyroclastic volcanism and sedimentation in an active continental margin  

NASA Astrophysics Data System (ADS)

We report sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone belt of western Dharwar Craton which is associated with rhyolites, chlorite schists and pyroclastic rocks. The pyroclastic rocks of Yalavadahalli area of Shimoga greenstone belt host volcanogenic Pb-Cu-Zn mineralization. The sediment-infill volcanic breccia is clast-supported and comprises angular to sub-angular felsic volcanic clasts embedded in a dolomitic matrix that infilled the spaces in between the framework of volcanic clasts. The volcanic clasts are essentially composed of alkali feldspar and quartz with accessory biotite and opaques. These clasts have geochemical characteristics consistent with that of the associated potassic rhyolites from Daginkatte Formation. The rare earth elements (REE) and high field strength element (HFSE) compositions of the sediment-infill volcanic breccia and associated mafic and felsic volcanic rocks suggest an active continental margin setting for their generation. Origin, transport and deposition of these rhyolitic clasts and their aggregation with infiltrated carbonate sediments may be attributed to pyroclastic volcanism, short distance transportation of felsic volcanic clasts and their deposition in a shallow marine shelf in an active continental margin tectonic setting where the rhyolitic clasts were cemented by carbonate material. This unique rock type, marked by close association of pyroclastic volcanic rocks and shallow marine shelf sediments, suggest shorter distance between the ridge and shelf in the Neoarchean plate tectonic scenario.

Manikyamba, C.; Saha, Abhishek; Ganguly, Sohini; Santosh, M.; Lingadevaru, M.; Rajanikanta Singh, M.; Subba Rao, D. V.

2014-12-01

112

Tectono-stratigraphy of late Archaean greenstone terranes in the southern Eastern Goldfields, Western Australia  

Microsoft Academic Search

Late Archaean greenstone terranes in the southern part of the Eastern Goldfields are regionally extensive, faultbounded entities defined on the basis of small but distinct differences in stratigraphy and structure. The greenstones comprise volcano-sedimentary successions that were all deposited at the same time (c. 2720-2675 Ma) on sialic crust. Hence, the terranes are interpreted to represent contemporaneous, probably adjacent, basins.

C. P. Swager

1997-01-01

113

Growth of granite–greenstone terranes at convergent margins, and stabilization of Archean cratons  

Microsoft Academic Search

Archean granite–greenstone terranes represent juvenile continental crust formed in a variety of plate tectonic settings and metamorphosed through a complex series of structural and magmatic events. Most Archean granite greenstone terranes appear to have acquired their first-order structural and metamorphic characteristics at convergent plate margins, where large accretionary wedges similar in aspect to the Chugach, Makran, and Altaids grew through

Timothy M Kusky; Ali Polat

1999-01-01

114

Radiation Belts  

NSDL National Science Digital Library

The inner radiation belt, discovered by Van Allen, consists of very energetic protons, a by-product of collisions of cosmic ray ions with atoms in the atmosphere. This site provides information on the behavior and relative energies of the particles in the belts. Historic information about the discoveries made in 1958 by a University of Iowa team, headed by James Van Allen, is cited as well.

Stern, David

115

Early Proterozoic (2.04 GA) Phoshorites of Pechenga Greenstone Belt and Their Origin  

NASA Technical Reports Server (NTRS)

No principal differences have been found between microfossils described from Cambrian and Phanerozoic and the 2000 Ma phosphorites. Numerous samples revealed diverse microbial microstructures interpreted as cyanobacterial mats consisting of filamentous (1-3 microns in diameter, 20 microns in length), coccoidal (0.8-1.0 microns) and ellipsoidal or rod-shaped microfossils (0.8 microns in diameter, around 2 microns in length) which morphologically resemble modern Microcoleus and Siphonophycus, Thiocapsa, and Rhabdoderma, respectively, reported from alkali ne or saline environment_ The sequence of the early Palaeoproterozoic events which point to a significant oxidation of the hydrosphere, including the formation of phosphorites and changes in the phosphorous cycle, mimics the sequence which was repeated at the Neoproterozoic-Cembrian transition, implying that oxidation of the terrestrial atmosphere-hydrosphere system experienced an irregular cyclic development.

Rozanov, Alexei Yu.; Astafieva, Marina M.; Hoover, Richard B.

2007-01-01

116

Economic geology of the Copper Mountain Supracrustal Belt, Owl Creek Mountains, Fremont County, Wyoming  

SciTech Connect

The Archean stratigraphy and associated mineral deposits at Copper Mountain were investigated to determine if this supracrustal belt has potential commercial mineral deposits. It was concluded Copper Mountain lacks the stratigraphic and structural character of a classical greenstone belt, exhibits higher metamorphic grade, and may be better classified as a high-grade terrain. However, potential is noted for stratiform Au associated with iron formation, stratiform W associated with gneiss, and Cu-Au mineralization in strike veins. 63 refs., 9 figs., 3 tabs. (ACR)

Hausel, W.D.; Graff, P.J.; Albert, K.G.

1985-01-01

117

Gould's Belt  

E-print Network

The local velocity patterns of star forming regions, young OB stars, nearby OB associations, atomic and molecular gas are confronted with models of an expanding region. We test free expansion from a point or from a ring, expanding 2D shell, and expanding 3D belt with abrupt or gradual energy injection snow-plowing the ambient medium with or without the drag forces including fragmentation and porosity of the medium. There is no agreement on the expansion time, which varies from 30 - 100 Myr. The inclination of the Gould belt is not explained by the above models of expansion. An oblique impact of a high velocity cloud may explain it, but the observed velocity pattern is difficult to reproduce. The Gould's belt may be one of the many structures resulting from shell-shell collisions in the galactic plane. The origin of the Gould's belt may be connected to instabilities in the curling gas flows downstream from the Galaxy spiral arms, forming ISM clouds and star formation complexes.

Palouš, Jan

2014-01-01

118

The geological record of life 3500 MA ago: Coping with the rigors of a young earth during late accretion  

Microsoft Academic Search

Thin cherty sedimentary layers within the volcanic portions of the 3,500 to 3,300 Ma-old Onverwacht and Fig Tree Groups, Barberton Greenstone belt, South Africa, and Warrawoona Group, eastern Pilbara Block, Western Australia, contain an abundant record of early Archean life. Five principal types of organic and probably biogenic remains and or structures can be identifed: stromatolites, stromatolite detritus, carbonaceous laminite

Donald R. Lowe

1989-01-01

119

Laterally bendable belt conveyor  

DOEpatents

An endless, laterally flexible and bendable belt conveyor particularly adapted for coal mining applications in facilitating the transport of the extracted coal up- or downslope and around corners in a continuous manner is disclosed. The conveying means includes a flat rubber belt reinforced along the middle portion thereof along which the major portion of the belt tension is directed so as to cause rotation of the tubular shaped belt when trammed around lateral turns thus preventing excessive belt bulging distortion between adjacent belt supports which would inhibit belt transport. Pretension induced into the fabric reinforced flat rubber belt by conventional belt take-up means supports the load conveyed when the belt conveyor is making lateral turns. The carrying and return portions of the belt are supported and formed into a tubular shape by a plurality of shapers positioned along its length. Each shaper is supported from above by a monorail and includes clusters of idler rollers which support the belt. Additional cluster rollers in each shaper permit the belt supporting roller clusters to rotate in response to the belt's operating tension imposed upon the cluster rollers by induced lateral belt friction forces. The freely rotating roller clusters thus permit the belt to twist on lateral curves without damage to itself while precluding escape of the conveyed material by effectively enclosing it in the tube-shaped, inner belt transport length.

Peterson, William J. (Coraopolis, PA)

1985-01-01

120

Greenstone-hosted lode-gold mineralization at Dungash mine, Eastern Desert, Egypt  

NASA Astrophysics Data System (ADS)

The auriferous quartz ± carbonate veins at Dungash mine, central Eastern Desert of Egypt, are confined to ?E-trending dilation zones within variably foliated/sheared metavolcanic/volcaniclastic rocks. The vein morphology and internal structures demonstrate formation concurrent with a dextral shear system. The latter is attributed to flexural displacement of folded, heterogeneous rock blocks through transpression increment, late in the Neoproterozoic deformation history of the area. Geochemistry of the host metavolcanic/metavolcaniclastic rocks from the mine area suggests derivation from a low-K, calc-alkaline magma in a subduction-related, volcanic arc setting. In addition, chemistry of disseminated Cr-spinels further constrain on the back-arc basin setting and low-grade metamorphism, typical of gold-hosting greenstone belts elsewhere. Mineralogy of the mineralized veins includes an early assemblage of arsenopyrite-As-pyrite-gersdorffite ± pyrrhotite, a transitional pyrite-Sb-arsenopyrite ± gersdorffite assemblage, and a late tetrahedrite-chalcopyrite-sphalerite-galena-gold assemblage. Based on arsenopyrite and chlorite geothermometers, formation of gold-sulfide mineralization occurred between ?365 and 280 °C. LA-ICP-MS measurements indicate the presence of refractory Au in arsenian pyrite (up to 53 ppm) and Sb-bearing arsenopyrite (up to 974 ppm). Abundant free-milling gold associated with the late sulfide assemblage may have been mobilized and re-distributed by circulating, lower temperature ore fluids in the waning stages of the hydrothermal system. Based on the isotopic values of vein quartz and carbonate, the calculated average ?18OH2O values of the ore fluids are 5.0 ± 1.4‰ SMOW for quartz, and 3.3 ± 1.4‰ for vein carbonate. The measured carbonate ?13C values correspond to ore fluids with ?13CCO2 = -6.7 ± 0.7‰ PDB. These results suggest a mainly metamorphic source for ore fluids, in good agreement with the vein morphology, textures and hydrothermal alteration. The calculated ?34SH2S values for early, transitional, and late sulfide assemblages define three distinct ranges (?1.5-3.6‰), (?0.4-1.0‰), and (-3.7‰ to -1.9‰), respectively. The systematic evolution towards lighter ?34S values may be attributed to recrystallization, or to ore fluid buffering under variable physicochemical conditions. The shear zone-related setting, mineralogy and isotopic characteristics of gold mineralization in Dungash mine are comparable with other orogenic gold deposits in the region (e.g., Barramiya deposit), which may suggest a regional setting controlling gold metallogeny of the region. This setting should guide future exploration programs in the central Eastern Desert province.

Zoheir, Basem; Weihed, Pär

2014-11-01

121

Evolution of the Archaean granite-greenstone terranes of the Eastern Goldfields, Western Australia: SHRIMP U?Pb zircon constraints  

Microsoft Academic Search

Thirty-five high-precision SHRIMP U?Pb zircon dates (with an average 95% confidence error of ±6 Ma) have been obtained from the granite-greenstone terranes in the southern part of the Eastern Goldfields of Western Australia. These dates establish the timing of major deformation, metamorphism and granite intrusion events, and test inferred stratigraphic relationships within the greenstones. These new data reveal that felsic

D. R. Nelson

1997-01-01

122

TTGs in the making: Natural evidence from Inyoni shear zone (Barberton, South Africa)  

NASA Astrophysics Data System (ADS)

Despite the consensus that TTGs, the main constituents of the Archaean continental crust worldwide, originated by partial melting of garnet-bearing amphibolites, natural evidence is scarce. A large variety of Archaean amphibole-rich rocks, including migmatitic amphibolites and hornblende-rich cumulates, was exhumed as a tectonic melange in the Inyoni shear zone (ISZ) near Barberton (South Africa), likely at the time of emplacement of the 3.2 Ga Nelshoogte-Badplaas plutons. This unique collection provides the opportunity to investigate partial melting of garnet-amphibolites, as well as the differentiation processes occurring in the TTG magmas en route to the surface. The ISZ migmatitic amphibolites are characterized by quartz-plagioclase leucosomes in equilibrium with garnet, amphibole, titanite ± epidote. Garnet compositions are characterized by high almandine and grossular contents. Actually, the leucosomes and neosomes likely lost part of their melt component and mesosomes may have been also modified towards restite-rich compositions due to melt segregation. Restite-bearing rocks are very iron-rich according to their high contents in garnet. Besides, the Mg-rich compositions of the hornblende cumulates and their REE distribution patterns resemble those of the nearby TT (tonalite-trondhjemite) plutons. Thermobarometric estimates from the ISZ migmatitic rocks cluster in the range 720-800 °C and 1.1-1.2 GPa for the melting reaction and the derived geothermal gradient is ca 17-22 °C/km. These conditions are consistent with either water-present melting or, more likely, water-absent epidote-dehydration melting. Such a geothermal gradient is therefore assigned to the genesis of large volumes of medium-pressure TTG magmas, that will likely form at greater depth. Unmelted garnet-bearing amphibolites correspond to slightly lower conditions. The magmatic cumulates crystallized at ca 0.6 GPa. The cumulate rocks evidence that the TTG parental magmas en route to the surface experienced fractional crystallization of a large amount of amphibole before crystallizing as tonalite-trondhjemite plutons at slightly shallower depths (ca 0.5 GPa).

Nédélec, A.; Chevrel, M. O.; Moyen, J. F.; Ganne, J.; Fabre, S.

2012-11-01

123

Belt pinch experiments  

Microsoft Academic Search

The major belt pinch facilities around the world are discussed including the NRL Pharos, the Juelich TESI, the Juelich TENQ, the Garching ISAR IV, the Garching 1MJ, and the Lausanne pinch. The Lausanne belt pinch experiment is described in detail, consisting of streak photography, measurements of magnetic fields and currents, and Thomson scattering measurements. It is found that high beta

F. Hofmann; L. Bighel; J. M. Peiry

1976-01-01

124

Kuiper Belt Objects  

Microsoft Academic Search

The region of the solar system immediately beyond Neptune's orbit is densely populated with small bodies. This region, known as the Kuiper Belt, consists of objects that may predate Neptune, the orbits of which provide a fossil record of processes operative in the young solar system. The Kuiper Belt contains some of the Solar System's most primitive, least thermally processed

David Jewitt

1999-01-01

125

Exploring Main Belt Asteroids  

Microsoft Academic Search

Terrestrial planet formation in the main asteroid belt was interrupted when growing protoplanets became sufficiently massive to gravitationally perturb the local population, causing bodies to collide with increased energy, thus ending accretion and commencing fragmentation and disruption. Few of these protoplanets are thought to have survived unshattered (e.g., Ceres, Vesta, Pallas), leaving a main belt population dominated by fragments of

M. V. Sykes; S. M. Larson; R. Whiteley; U. Fink; R. Jedicke; J. Emery; R. Fevig; M. Kelley; A. W. Harris; S. Ostro; K. Reed; R. P. Binzel; A. Rivkin; C. Magri; W. Bottke; D. Durda; R. Walker; D. Davis; W. K. Hartmann; D. Sears; H. Yano; J. Granahan; A. Storrs; S. J. Bus; J. F. Bell; D. Tholen; A. Cellino

2001-01-01

126

Kuiper Belt Objects  

NASA Astrophysics Data System (ADS)

The region of the solar system immediately beyond Neptune's orbit is densely populated with small bodies. This region, known as the Kuiper Belt, consists of objects that may predate Neptune, the orbits of which provide a fossil record of processes operative in the young solar system. The Kuiper Belt contains some of the Solar System's most primitive, least thermally processed matter. It is probably the source of the short-period comets and Centaurs, and may also supply collisionally generated interplanetary dust. I discuss the properties of the Kuiper Belt and provide an overview of the outstanding scientific issues.

Jewitt, David

127

Belt conveyor apparatus  

DOEpatents

A belt conveyor apparatus according to this invention defines a conveyance path including a first pulley and at least a second pulley. An endless belt member is adapted for continuous travel about the pulleys and comprises a lower portion which engages the pulleys and an integral upper portion adapted to receive objects therein at a first location on said conveyance path and transport the objects to a second location for discharge. The upper belt portion includes an opposed pair of longitudinally disposed crest-like members, biased towards each other in a substantially abutting relationship. The crest-like members define therebetween a continuous, normally biased closed, channel along the upper belt portion. Means are disposed at the first and second locations and operatively associated with the belt member for urging the normally biased together crest-like members apart in order to provide access to the continuous channel whereby objects can be received into, or discharged from the channel. Motors are in communication with the conveyance path for effecting the travel of the endless belt member about the conveyance path. The conveyance path can be configured to include travel through two or more elevations and one or more directional changes in order to convey objects above, below and/or around existing structures.

Oakley, David J. (Richland, WA); Bogart, Rex L. (Kennewick, WA)

1987-01-01

128

Six Sigma Black Belts Fight For Quality  

E-print Network

a Black Belt performs. Table 2 Black Belt Tasks Mentor Cultivate a network of Six Sigma individualsSix Sigma Black Belts Fight For Quality Ron Scott Ross Finnestad Rodney Kalsow IE 361 mini-paper 9 Black Belts, Black Belts, and Green Belts. "Training individuals as Black Belts gives them the skills

Vardeman, Stephen B.

129

Radiation belt probes launched  

NASA Astrophysics Data System (ADS)

Storms on Earth delayed by only a few days the launch of NASA's Radiation Belt Storm Probes (RBSP), which blasted off on 30 August for a 2-year tour to explore the Van Allen radiation belts. The two satellites will help scientists learn about the processes that affect electrons and ions in the donut-shaped belts and how the belts change in the context of geomagnetic storms. “The information collected from these probes will benefit the public by allowing us to better protect our satellites and understand how space weather affects communications and technology on Earth,” said John Grunsfeld, associate administrator for NASA's Science Mission Directorate. Each probe carries an identical suite of instruments, including an Energetic Particle, Composition, and Thermal Plasma Suite; Electric and Magnetic Field Instrument Suite and Integrated Science; Electric Field and Waves Suite; Radiation Belt Storm Probes Ion Composition Experiment; and Relativistic Proton Spectrometer. RBSP is part of NASA's Living With a Star program and is managed for NASA by the Johns Hopkins University's Applied Physics Laboratory. For more information, see http://rbsp.jhuapl.edu.

Showstack, Randy

2012-09-01

130

Rust Belt Rebounds  

NSDL National Science Digital Library

This recent Census Brief (CENBR/98-7) looks at nonfarm business establishments, unemployment, crime, and new job generation in so-called "rust belt" metropolitan areas such as Detroit-Ann Arbor-Flint, MI and Cleveland-Akron, OH. The report notes an economic and demographic rebound, deemed a "statistical reversal of fortune," with some exceptions outside of the Midwest.

1998-01-01

131

Kuiper Belt & Oort Cloud  

NSDL National Science Digital Library

This NASA website provides information about the group of short-period comets in the Kuiper Belt. The article compares the sizes and composition of these objects to Earth and Pluto. Telescopic images and artists' conceptions illustrate the site. There is a link to a kid's page that has information over the same subject but more appropriate for children.

2007-07-03

132

Radiation belts of Jupiter  

Microsoft Academic Search

Pioneer 10 courted relativistic electrons throughout the magnetosphere ; of Jupiter, with the greatest fluxes being inside 20 Jupiter radii. The peak ; flux of electrons with energy greater than 50 MeV was 1.3 x 107 per square ; centimeter per second at the innermost penetration of the radiation belts. ; (auth);

R. W. Fillius; C. E. McIlwain

1974-01-01

133

Exploring Main Belt Asteroids  

Microsoft Academic Search

The asteroid belt is filled with fragments of disrupted protoplanets, of which only a few survive. It has been dynamically stirred and suffered substantial mass loss. Samples exist on the Earth as meteorites. Putting these pieces back together provides a window into an early chapter of solar system history, during and after its formation, capturing the earliest epoch of planet

M. V. Sykes; E. Asphaug; J. F. Bell; R. P. Binzel; W. Bottke; S. J. Bus; A. Cellino; P. Clark; D. R. Davis; M. C. de Sanctis; D. D. Durda; J. Emery; R. A. Fevig; U. Fink; J. Granahan; A. W. Harris; W. K. Hartmann; R. Jedicke; M. Kelley; S. M. Larson; D. J. Lien; C. Magri; S. J. Ostro; K. L. Reed; A. S. Rivkin; D. W. G. Sears; A. Storrs; D. J. Tholen; R. Walker; R. Whiteley; H. Yano

2002-01-01

134

Aluminum depletion in komatiites and garnet fractionation in the early Archean mantle: Hafnium isotopic constraints  

SciTech Connect

Hafnium isotopic compositions were measured in Al-depleted and Al-enriched komatiites from the 3,450 Ma old Barberton greenstone belt, southern Africa. All samples have initial {var epsilon}{sub Hf} values close to zero. Such values are at variance with the strongly negative or positive values that should be observed if these rocks came from old garnet-depleted or garnet-enriched layers, such as may have formed during the solidification of an ancient terrestrial magma ocean. The garnet fractionation observed in komatiites probably took place during the melting event.

Gruau, G. (Max Planck Institut fuer Chemie, Mainz (West Germany) Universite de Rennes (France)); Chauvel, C.; Arndt, N.T. (Max Planck Institut fuer Chemie, Mainz (West Germany)); Cornichet, J. (Universite de Rennes (France))

1990-11-01

135

Geometric analysis and significance of mesoscopic shear zones in the Precambrian gneisses around the Kolar Schist Belt, south India  

NASA Astrophysics Data System (ADS)

Mesoscopic shear zones are well preserved in the gneisses around the Kolar Schist Belt, located in the eastern part of the northern granite—greenstone association of the south Indian Precambrian terrain. The majority of these shear zones are of ductile to brittle—ductile type with both dextral and sinistral senses of movement. The detailed geometry and large-scale mapping show that sinistral shear zones strike dominantly NW, whereas dextral shear zones strike dominantly NE and form a conjugate pair. The bisectors of statistically preferred orientations of these two sets of shear zones indicate that they developed in response to an E-W subhorizontal compression which can be correlated to the late stage of the F2 folding seen inside the schist belt. Displacement vectors along these shear zones are invariably subhorizontal, precluding the possibility of overthrusting or underthrusting relationship between the schist belt and surrounding gneissic terrains. If the schist belt is a major shear zone, the displacement across it can not be more than 15 km.

Mukhopadhyay, Dilip K.; Haimanot, Beraki W.

136

Pandyan Mobile Belt  

Microsoft Academic Search

\\u000a Pandyan Mobile Belt (PMB) is the name given by Ramakrishnan (1993, 1988) to the Southern Granulite Terrain (SGT) situated\\u000a to the south of the E-W trending Palghat-Cauvery Shear Zone (PCSZ) (Fig. 8.1). The name Pandyan is adopted after the legendary\\u000a dynasty that ruled this part of South India in the historical past. Interestingly, the SGT has been defined variously by

Ram Sharma

137

Aster's Hoity Toity Belt  

NSDL National Science Digital Library

This is an annotated children's story about the Dawn mission to Vesta and Ceres in the asteroid belt. Learners will dissect the story for real and fictional objects and places in the solar system, and for those scientific concepts or processes that may be true. Support materials include the story with space for kids to illustrate, an audio recording of the story by the author and an extension activity.

138

49 CFR 393.93 - Seats, seat belt assemblies, and seat belt assembly anchorages.  

Code of Federal Regulations, 2010 CFR

...belt assemblies, and seat belt assembly anchorages. 393.93 Section 393.93 Transportation Other Regulations Relating to...SAFE OPERATION Miscellaneous Parts and Accessories § 393.93 Seats, seat belt assemblies, and seat belt...

2010-10-01

139

Moving belt metal detector  

NASA Astrophysics Data System (ADS)

The Johns Hopkins University Applied Physics Laboratory (APL) has developed a prototype metal detection survey system that will increase the search speed of conventional technology while maintaining high sensitivity. Higher search speeds will reduce the time to clear roads of landmines and improvised explosive devices (IED) and to locate unexploded ordnance (UXO) at Base Realignment and Closure (BRAC) sites, thus reducing remediation costs. The new survey sensor system is called the moving belt metal detector (MBMD) and operates by both increasing sensor speed over the ground while maintaining adequate sensor dwell time over the target for good signal-to-noise ratio (SNR) and reducing motion-induced sensor noise. The MBMD uses an array of metal detection sensors mounted on a flexible belt similar to a tank track. The belt motion is synchronized with the forward survey speed so individual sensor elements remain stationary relative to the ground. A single pulsed transmitter coil is configured to provide a uniform magnetic field along the length of the receivers in ground contact. Individual time-domain electromagnetic induction (EMI) receivers are designed to sense a single time-gate measurement of the total metal content. Each sensor module consists of a receiver coil, amplifier, digitizing electronics and a low power UHF wireless transmitter. This paper presents the survey system design concepts and metal detection data from various targets at several survey speeds. Although the laboratory prototype is designed to demonstrate metal detection survey speeds up to 10 m/s, higher speeds are achievable with a larger sensor array. In addition, the concept can be adapted to work with other sensor technologies not previously considered for moving platforms.

Nelson, Carl V.; Mendat, Deborah P.; Huynh, Toan B.

2006-05-01

140

Number Conveyor Belt  

NSDL National Science Digital Library

This activity for the interactive white board (free access with registration) allows a teacher to create an arithmetic sequence for students to watch being built as the sequence of numbers moves along a conveyor. Learners must determine the pattern being used so when the belt randomly stops, the missing number in the sequence can be dragged/ dropped into its place. The teacher sets the start number (0-19), the interval or common difference (1-10) and if the sequence will count up or down. This last option provides an opportunity to display patterns with integers.

2012-01-01

141

30 CFR 77.406 - Drive belts.  

Code of Federal Regulations, 2013 CFR

...SURFACE WORK AREAS OF UNDERGROUND COAL MINES Safeguards for Mechanical Equipment § 77.406 Drive belts. (a) Drive belts...shifted while in motion unless the machines are provided with mechanical shifters. (b) Belt dressing shall not be applied...

2013-07-01

142

30 CFR 77.406 - Drive belts.  

...SURFACE WORK AREAS OF UNDERGROUND COAL MINES Safeguards for Mechanical Equipment § 77.406 Drive belts. (a) Drive belts...shifted while in motion unless the machines are provided with mechanical shifters. (b) Belt dressing shall not be applied...

2014-07-01

143

30 CFR 77.406 - Drive belts.  

Code of Federal Regulations, 2010 CFR

...SURFACE WORK AREAS OF UNDERGROUND COAL MINES Safeguards for Mechanical Equipment § 77.406 Drive belts. (a) Drive belts...shifted while in motion unless the machines are provided with mechanical shifters. (b) Belt dressing shall not be applied...

2010-07-01

144

30 CFR 77.406 - Drive belts.  

Code of Federal Regulations, 2012 CFR

...SURFACE WORK AREAS OF UNDERGROUND COAL MINES Safeguards for Mechanical Equipment § 77.406 Drive belts. (a) Drive belts...shifted while in motion unless the machines are provided with mechanical shifters. (b) Belt dressing shall not be applied...

2012-07-01

145

30 CFR 77.406 - Drive belts.  

Code of Federal Regulations, 2011 CFR

...SURFACE WORK AREAS OF UNDERGROUND COAL MINES Safeguards for Mechanical Equipment § 77.406 Drive belts. (a) Drive belts...shifted while in motion unless the machines are provided with mechanical shifters. (b) Belt dressing shall not be applied...

2011-07-01

146

Geology, geochemistry and genesis of BIF of Kushtagi schist belt, Archaean Dharwar Craton, India  

NASA Astrophysics Data System (ADS)

The Banded Iron-Formation (BIF) of the Kushtagi schist belt, Dharwar Craton is interbedded with metavolcanics. The oxide fades cherty (Al2O3 < 2%) and shaley (Al2O3 > 2%) BIFs show large-scale variations in their major and trace elements abundance. Cherty Banded Iron-Formation (CBIF) is depleted in Al2O3, TiO2, Zr, Hf and other trace elements like Cr, Ni, Co, Rb, Sr, V, Y and REE in comparison to Shaley Banded Iron-Formation (SBIF). Depleted ?REE, positive Eu anomalies and the flat to HREE-enriched pattern of CBIF indicate that Fe and SiO2 for these BIFs were added to ambient ocean water by hydrothermal solutions at the AMOR vent sites. It is inferred that the higher amount of hydrothermal fluid flux with a higher exit temperature provided enormous quantities of iron and silica. Fine-grained sedimentation in the basin gave rise to the observed variability in the composition of BIF. During transgression a wave base was raised up, consequently deposition of CBIF became possible, whereas, during the regressive stage, these chemical sediments were buried by and/or mixed with the terrigenous sediments resulting in deposition of SBIF and interbedded shales. Volcaniclastic activity within the basin appears to have contributed significantly to the composition of some SBIF and shales. The hydrothermal exhalative hypothesis combined with the Archaean miniplate model explains most of the chemical features of the BIFs of greenstone belts.

Khan, R. M. K.; Naqvi, S. M.

1996-01-01

147

Physics and Automobile Safety Belts.  

ERIC Educational Resources Information Center

This collection of problems and experiments related to automobile safety belt usage is intended to serve as a supplement to a standard physics course. Its purpose is to convince the students that the use of safety belts to prevent injury or death is firmly supported by the considerations of physical quantities and laws which apply in a collision…

Kortman, Peter; Witt, C. Edwin

148

KUIPER BELT OBJECTS David Jewitt  

E-print Network

: Kuiper Belt Page 3 ABSTRACT The region of the solar system immediately beyond Neptune's orbit is densely­date Neptune, the orbits of which provide a fossil record of processes operating in the young solar system interplanetary dust. We discuss the properties of the Kuiper Belt and provide an overview of the outstanding

Jewitt, David C.

149

Evaluation of the technological feasibility, and cost of selected control alternatives necessary to meet the proposed Ohio SOâ regulations for industrial boilers and processes. Volume II. PPG Industries, Inc. , Barberton Plant. Final report  

Microsoft Academic Search

This report presents an evaluation by the GCA Corporation, GCA\\/Technology Division of technological feasibility and cost of complying with the proposed Ohio sulfur dioxide regulation (40 FR 52410, November 10, 1975) at PPG Industries' Barberton plant. The final USEPA Sulfur Dioxide Control Strategy for the State of Ohio Technical Support Documents, Vol. I and II (EPA 905\\/2-76-002) may be obtained

J. Sahagian; R. R. Hall

1976-01-01

150

Previously Undetected Radiation Belt Revealed  

NASA Video Gallery

Since their discovery over 50 years ago, the Earth'??s Van Allen radiation belts have been considered to consist of two distinct zones of trapped, highly energetic charged particles. Observations f...

151

Calculating Belt Velocity and Horsepower  

NSDL National Science Digital Library

In this Flash-based interactive object by James Bourassa and John Rosz from Fox Valley Technical College, learners are given the RPM, the pulley diameter, and the force, and proceed to calculate belt velocity and horsepower.

Bourassa, James; Rosz, John

2008-10-23

152

The earth's trapped radiation belts  

NASA Technical Reports Server (NTRS)

The near-earth charged particle environment is discussed in terms of spacecraft design criteria. Models are presented of the trapped radiation belts and based on in-situ data obtained from spacecraft.

Noll, R. B.; Mcelroy, M. B.

1975-01-01

153

Chaos on the conveyor belt.  

PubMed

The dynamics of a spring-block train placed on a moving conveyor belt is investigated both by simple experiments and computer simulations. The first block is connected by a spring to an external static point and, due to the dragging effect of the belt, the blocks undergo complex stick-slip dynamics. A qualitative agreement with the experimental results can be achieved only by taking into account the spatial inhomogeneity of the friction force on the belt's surface, modeled as noise. As a function of the velocity of the conveyor belt and the noise strength, the system exhibits complex, self-organized critical, sometimes chaotic, dynamics and phase transition-like behavior. Noise-induced chaos and intermittency is also observed. Simulations suggest that the maximum complexity of the dynamical states is achieved for a relatively small number of blocks (around five). PMID:23679502

Sándor, Bulcsú; Járai-Szabó, Ferenc; Tél, Tamás; Néda, Zoltán

2013-04-01

154

Belt conveyors for bulk materials. 6th ed.  

SciTech Connect

The 16 chapters are entitled: Belt conveyor general applications economics; Design considerations; Characteristics and conveyability of bulk materials; Capacities, belt widths and speeds; Belt conveyor idlers; Belt tension and power engineering; Belt selection; Pulleys and shafts; Curves; Steep angle conveying; Belt cleaners and accessories; Transfer points; Conveyor motor drives and controls; Operation, maintenance and safety; Belt takeups; and Emerging technologies. 6 apps.

NONE

2007-07-01

155

Composition and origin of fluids associated with lode gold deposits in a Mesoarchean greenstone belt (Warrawoona Syncline, Pilbara Craton, Western Australia) using synchrotron radiation X-ray fluorescence  

Microsoft Academic Search

Microthermometry and Raman spectroscopy techniques are routinely use to constrain ore-fluids ?18O and molar proportions of anhydrous gas species (CO2, CH4, N2). However, these methods remain imprecise concerning the ore-fluids composition and source. Synchrotron radiation X-ray fluorescence allows access to major and trace element concentrations (Cl, Br and K, Ca, Fe, Cu, Zn, As, Rb, Sr) of single fluid inclusion.

Nicolas Thébaud; Pascal Philippot; Patrice Rey; Jean Cauzid

2006-01-01

156

Mantle heterogeneity and crustal recycling in Archean granite-greenstone belts - Evidence from Nd isotopes and trace elements in the Rainy Lake area, Superior Province, Ontario, Canada  

NASA Technical Reports Server (NTRS)

Crustal evolution in the Rainy Lake area, Ontario is studied in terms of geochemical characteristics. The Nd isotope data are examined for heterogeneity of the Archean mantle, and the Sm/Nd depletion of the mantle is analyzed. The Nd isotope systematics of individual rock suites is investigated in order to understand the difference between crust and mantle sources; the precursors and petrogenetic processes are discussed. The correlation between SiO2 content and Nd values is considered. Rapid recycling of crustal components, which were previously derived from depleted mantle sources, is suggested based on the similarity of the initial Nd isotopic composition for both mantle-derived and crustally-derived rocks.

Shirey, Steven B.; Hanson, Gilbert N.

1986-01-01

157

Oxidized and reduced mineral assemblages in greenstone belt rocks of the St. Ives gold camp, Western Australia: vectors to high-grade ore bodies in Archaean gold deposits?  

NASA Astrophysics Data System (ADS)

Hydrothermal sulfide-oxide-gold mineral assemblages in gold deposits in the Archaean St. Ives gold camp in Western Australia indicate extremely variable redox conditions during hydrothermal alteration and gold mineralization in space and time. Reduced alteration assemblages (pyrrhotite-pyrite) occur in deposits in the southwest of the camp (e.g., Argo, Junction deposits) and moderately to strongly oxidized assemblages (magnetite-pyrite, hematite-pyrite) occur in deposits in the Central Corridor in the northeast (e.g., North Orchin, Revenge deposits). Reduced mineral assemblages flank the Central Corridor of oxidized deposits and, locally, cut across it along E-W trending faults. Oxidized mineral assemblages in the Central Corridor are focused on gravity lows which are interpreted to reflect abundant felsic porphyritic intrusions at about 1,000 m below present surface. Hydrothermal magnetite predates and is synchronous with early phases of gold-associated albite-carbonate-pyrite-biotite-chlorite hydrothermal alteration. Later-stage, gold-associated pyrite is in equilibrium with hematite. The spatial distribution and temporal sequence of iron sulfides and oxides with gold indicate the presence of at least two spatially restricted but broadly synchronous hydrothermal fluids with contrasting redox states. Sulfur isotope constraints support the argument that the different mineral assemblages reflect differences in redox conditions. The ? 34S values for pyrite for the St. Ives gold camp range between -8.4‰ and +5.1‰ with the negative values occurring in oxidized magnetite-rich domains and slightly negative or positive values occurring in reduced, pyrrhotitic domains. Preliminary spatial and paragenetic analysis of the distribution of iron sulfides and oxides in the St. Ives camp suggests that gold grades are highest where the redox state of the hydrothermal alteration assemblages switches from relatively reduced pyrrhotite-pyrite to relatively oxidized magnetite-pyrite and hematite-pyrite both in space and time. Gold deposition is inferred to have occurred where fluids of contrasting redox state mixed.

Neumayr, Peter; Walshe, John; Hagemann, Steffen; Petersen, Klaus; Roache, Anthony; Frikken, Peter; Horn, Leo; Halley, Scott

2008-03-01

158

Oxidized and reduced mineral assemblages in greenstone belt rocks of the St. Ives gold camp, Western Australia: vectors to high-grade ore bodies in Archaean gold deposits?  

Microsoft Academic Search

Hydrothermal sulfide–oxide–gold mineral assemblages in gold deposits in the Archaean St. Ives gold camp in Western Australia\\u000a indicate extremely variable redox conditions during hydrothermal alteration and gold mineralization in space and time. Reduced\\u000a alteration assemblages (pyrrhotite–pyrite) occur in deposits in the southwest of the camp (e.g., Argo, Junction deposits)\\u000a and moderately to strongly oxidized assemblages (magnetite–pyrite, hematite–pyrite) occur in deposits

Peter Neumayr; John Walshe; Steffen Hagemann; Klaus Petersen; Anthony Roache; Peter Frikken; Leo Horn; Scott Halley

2008-01-01

159

Fluid evolution in the H 2O-CH 4-CO 2-NaCl system during emerald mineralization at Gravelotte, Murchison Greenstone Belt, Northeast Transvaal, South Africa  

NASA Astrophysics Data System (ADS)

Fluid evolution during emerald mineralization at the Gravelotte emerald mine has been studied by microthermometry and laser Raman microprobe spectrometry. The emeralds and associated phenakites occur on the flanks of a highly metasomatised albitite pegmatoid body and in the biotite schists at and near its contact. The fluids lie in the H 2O-CH 4-CO 2-NaCl system and four types of inclusions are characterised based on time of trapping and fluid contents. The earliest type 1 inclusions, found in phenakites and the emeralds which formed from them, are low salinity (<6 wt% NaCl) with up to 18 mol% CH 4. The carbonic phase contains over 93 mol% CH 4 and variable small amounts of CO 2, C 2H 6, N 2, and H 2S. The solvus crest for this system lies at ?400°C, closer to the H 2O end of the join. With time the fluids become less CH 4 rich and more saline. The type 2 fluids are highly variable in both CH 4-CO 2 contents and salinity, reflecting mixing of type 1 fluids with higher salinity brines. The late type 3 and 4 inclusions are CH 4-CO 2-free high salinity inclusions with up to 38 wt% NaCl. Trapping conditions for the type 1 fluids were around 450-500°C and 4 kb based on model isochores and geologic evidence. During the trapping of type 2 inclusions, fluid pressures probably fluctuated due to opening and resealing of fractures. Approximate P- T ranges of trapping for these and other later inclusions have been defined, minimum trapping temperatures for types 2, 3, and 4 being, respectively, 250, 150, and 240°C, and pressures in the range of 1-4 kb. Calculations of ƒ O 2 show an initial low ƒ O 2 between QFM and the synthetic graphite-CH 4 buffer for the type 1 fluids. This rises to above QFM in the later stages. Such low initial values are uncharacteristic of granitic pegmatite systems, and it is suggested that the phenakites formed in the post-magmatic stage of alkali metasomatism when the albitization took place. In the later stages, phenakite was converted to emerald as alumina activities in the system increased. Concomitantly higher salinity brines, at least some of which are probably related to regional metamorphism in the area, were trapped under higher ƒ O 2 conditions. Metasomatic exchange with the mafic host rocks also increased as evidenced by the incorporation of Cr in the late emeralds. The energy necessary for the continuous growth of the later emeralds was probably supplied by regional metamorphism.

Nwe, Yin Yin; Morteani, Giulio

1993-01-01

160

Using the Abitibi Greenstone Belt to Understand Martian Hydrothermal Systems and the Potential for Biosignature Preservation in High Temperature Aqueous Environments  

NASA Technical Reports Server (NTRS)

Metabolic bone diseases like osteoporosis result from the disruption of normal bone mineral balance (BMB) resulting in bone loss. During spaceflight astronauts lose substantial bone. Bed rest provides an analog to simulate some of the effects of spaceflight; including bone and calcium loss and provides the opportunity to evaluate new methods to monitor BMB in healthy individuals undergoing environmentally induced-bone loss. Previous research showed that natural variations in the Ca isotope ratio occur because bone formation depletes soft tissue of light Ca isotopes while bone resorption releases that isotopically light Ca back into soft tissue (Skulan et al, 2007). Using a bed rest model, we demonstrate that the Ca isotope ratio of urine shifts in a direction consistent with bone loss after just 7 days of bed rest, long before detectable changes in bone mineral density (BMD) occur. The Ca isotope variations tracks changes observed in urinary N-teleopeptide, a bone resorption biomarker. Bone specific alkaline phosphatase, a bone formation biomarker, is unchanged. The established relationship between Ca isotopes and BMB can be used to quantitatively translate the changes in the Ca isotope ratio to changes in BMD using a simple mathematical model. This model predicts that subjects lost 0.25 +/- 0.07% (+/- SD) of their bone mass from day 7 to day 30 of bed rest. Given the rapid signal observed using Ca isotope measurements and the potential to quantitatively assess bone loss; this technique is well suited to study the short-term dynamics of bone metabolism.

Hurowitz, J.; Abelson, J.; Allwood, A.; Anderson, R.; Atkinson, B.; Beaty, D.; Bristow, T.; Ehlmann, B.; Eigenbrode, J.; Grotzinger, J.; Hand, K.; Halevy, I.; Knoll, A.; McCleese, D.; Milliken, R.; Russell, M.; Stolper, D.; Stolper, E.; Tosca, N.

2011-01-01

161

Fluid chemistry and evolution of hydrothermal fluids in an Archaean transcrustal fault zone network: The case of the Cadillac Tectonic Zone, Abitibi greenstone belt, Canada  

USGS Publications Warehouse

Detailed fluid geochemistry studies on hydrothermal quartz veins from the Rouyn-Noranda and Val-d'Or areas along the transcrustal Cadillac Tectonic Zone (CTZ) indicate that unmineralized (with respect to gold) sections of the CTZ contained a distinct CO2-dominated, H2S-poor hydrothermal fluid. In contrast, both gold mineralized sections of the CTZ (e.g., at Orenada #2) and associated higher order shear zones have a H2O-CO2 ?? CH4-NaCl hydrothermal fluid. Their CO2/H2S ratios indicate H2S-rich compositions. The Br/Cl compositions in fluid inclusions trapped in these veins indicate that hydrothermal fluids have been equilibrated with the crust. Oxygen isotope ratios from hydrothermal quartz veins in the CTZ are consistently 2??? more enriched than those of associated higher order shear zones, which are interpreted to be a function of greater fluid/rock ratios in the CTZ and lower fluid/rock ratios, and more efficient equilibration of the hydrothermal fluid with the wall rock, in higher order shear zones. An implication from this study is that the lower metal endowment of the transcrustal CTZ, when compared with the higher metal endowment in higher order shear zones (ratio of about 1 : 1000), may be the result of the lack of significant amounts of H2O-H2S rich fluids in most of the CTZ. In contrast, gold mineralization in the higher order shear zones appear to be controlled by the high H2S activity of the aqueous fluids, because gold was likely transported in a bisulfide complex and was deposited during sulfidation reactions in the wall rock and phase separation in the quartz veins. ?? 2007 NRC Canada.

Neumayr, P.; Hagemann, S. G.; Banks, D. A.; Yardley, B. W. D.; Couture, J. -F.; Landis, G. P.; Rye, R.

2007-01-01

162

Satellite Feature Identification: Conveyor Belts  

NSDL National Science Digital Library

Conveyor belts highlight important atmospheric processes that can be advantageous for making forecasts. They can be used for identifying general temperature patterns, defining the extent of cloud cover, predicting moisture return, evaluating stability, forecasting wind gusts, pinpointing cyclogenesis, and understanding the three-dimensional structure of the atmosphere. For short-term forecasts, they can even augment NWP showing the three-dimensional structure and portraying the same information as equivalent or wet-bulb potential temperature and potential vorticity surfaces. Conveyor belts make representing the total wind easier than using isobaric surfaces which only cut through the processes giving limited, two-dimensional views of the total wind. In this lesson, learn to identify conveyor belts using water vapour imagery. You'll be able to understand the structure of the conveyor belt's isentropic surfaces from the water vapour imagery and use that knowledge to enhance your forecasting. Further analysis will allow you to break your conveyor belts into branches for even more forecasting ability. It is highly encouraged that students review the "Deformation Zone Analysis" and "Inferring Three Dimensions from Water Vapour imagery" lessons before attempting this lesson.

Comet

2014-03-18

163

Trends in PVC conveyor belting  

SciTech Connect

The development of mechanical systems of extraction at the coal face necessitated the introduction of efficient methods of mineral transportation in deep-mining operations. The most popular system is the belt conveyor. Originally PVC was being evaluated as a rubber substitute, as in its liquid form it appeared to offer an easier route to fabric coating and impregnation for conveyor belt applications. However, it was not until 1950, when over 200 miners lost their lives due to an underground fire being spread by combustible rubber conveyor belts, that the full significance of the properties of PVC were appreciated. Following this tragedy, an intensive development program to produce a substitute for rubber was initiated. It had to have similar operational characteristics as rubber while incorporating the safety features of resistance to flame propagation and build-up of static electrical charges. It became evident that PVC could be compounded to realize these requirements and belting manufacturers immediately started to produce a new generation of belts based on the previouly proven mechanical characteristics of multiply fabrics, but substituting PVC for the rubber content. The advantages of PVC are discussed.

Hopwood, J.E.

1984-03-01

164

46 CFR 169.723 - Safety belts.  

Code of Federal Regulations, 2010 CFR

...and Equipment § 169.723 Safety belts. Each vessel must carry a harness type safety belt conforming to Offshore Racing Council (ORC) standards for each person on watch or required to work the vessel in heavy...

2010-10-01

165

30 CFR 77.1107 - Belt conveyors.  

Code of Federal Regulations, 2010 CFR

...Protection § 77.1107 Belt conveyors. Belt conveyors in locations where fire would create a hazard to personnel shall be provided with switches to stop the drive pulley automatically in the event of excessive...

2010-07-01

166

Radiation Belt Storm Probe Mission Trailer  

NASA Video Gallery

With launch scheduled for 2012, the Radiation Belt Storm Probe (RBSP) are two identical spacecraft that will investigate the doughnut shaped Van Allen radiation belts, the first discovery of the sp...

167

1 The Main Asteroid Belt Carolyn Crow: NASA's Dawn Mission The Main Asteroid Belt  

E-print Network

1 The Main Asteroid Belt Carolyn Crow: NASA's Dawn Mission The Main Asteroid Belt Written to the main asteroid belt to visit two of the largest protoplanets, Vesta and Ceres. Using sunlight, a mere accomplished by a spacecraft before. What compelled astronomers to send Dawn to the asteroid belt and what does

Waliser, Duane E.

168

Small Main-Belt Asteroid Lightcurve Survey  

NASA Technical Reports Server (NTRS)

The Small Main-Belt Asteroid Lightcurve Survey is the first to measure main-belt asteroid lightcurve properties for bodies with diameters smaller than 5 km. Attention is given to CCD lightcurves for 32 small main-belt asteroids. The objects of this sample have a mean rotational frequency which is faster than that of larger main-belt asteroids. All lightcurves were investigated for nonperiodic variations ascribable to free precession; no conclusive detection of this phenomenon has been made, however.

Binzel, Richard P.; Xu, Shui; Bus, Schelte J.; Bowell, Edward

1992-01-01

169

Structure of the Kuiper Belt Dust Disk  

Microsoft Academic Search

An overview of the Kuiper belt dust disk is provided in this chapter. Mutual collisions among Kuiper belt objects should produce a dust disk in the outer solar system similar to the observed circumstellar dust disks. As the Kuiper belt dust particles migrate toward the Sun due to Poynting-Robertson drag, they are perturbed by the giant planets. Mean-motion resonances with

J.-C. Liou; D. E. Kaufmann

2008-01-01

170

Pregnancy: Should I Use a Seat Belt?  

MedlinePLUS

... injury or death in the event of a car crash. You should wear a seat belt no matter where you sit in the car. How should I wear my seat belt? The ... belts keep you from being thrown from the car during an accident. The shoulder strap also keeps ...

171

The BELT Theory of Discipline.  

ERIC Educational Resources Information Center

The author concludes from his research that severe parental punishment (the use of a belt or its equivalent) is an almost necessary, if not sufficient, precursor to habitual male delinquency. He outlines his theory on the development of aggression and suggests ways for schools to counteract violence in the home. (Author/SJL)

Welsh, Ralph S.

1980-01-01

172

Hafnium-neodymium isotope systematics of the 2.7 Ga Gadwal greenstone terrane, Eastern Dharwar craton, India: Implications for the evolution of the Archean depleted mantle  

NASA Astrophysics Data System (ADS)

The Neoarchean Gadwal greenstone belt in the eastern Dharwar craton, India, hosts a well preserved metavolcanic sequence that is dominated by tholeiitic and calc-alkaline basalt-andesite-dacite-rhyolite series, which includes boninitic geochemical varieties. Bulk-rock Lu-Hf and Sm-Nd isotope systematics of these apparently arc-related volcanic rocks yield indistinguishable ages of 2.701 ± 0.024 Ga and 2.702 ± 0.026 Ga, respectively. On the basis of the close spatial association and identical ages of the different rock types we suggest 2.70 ± 0.03 Ga as the age of crystallization of the different rock types within the Gadwal metavolcanic sequence. In contrast, bulk-rock Pb-Pb isotope systematics of the same samples yield a significantly younger and less precise age of 2.466 Ga (+0.068/-0.110 Ga). We tentatively interpret this younger age to represent a metallogenic and crustal reworking event in the Dharwar craton, which disturbed the U-Pb system but not the Lu-Hf or Sm-Nd systems. The Gadwal metavolcanic rocks have positive initial ?Hf(2.70Ga) = + 1.6 to + 8.7 and slightly negative to positive ?Nd(2.70Ga) = -0.1 to + 3.0 values, consistent with an origin from a long term depleted source relative to a chondritic reservoir at ˜2.7 Ga. Lack of correlation between initial isotopic compositions and major or trace element indices of fractionation and alteration suggest that the observed isotope variability probably reflects compositional variation in the Gadwal source, similar to that observed in modern day island arcs. Two boninitic samples of the Gadwal sequence have ?Hf ˜ 8.3 and 8.7, and are more radiogenic than average depleted mantle for the time period 3.2 to 2.5 Ga (?Hf = 4 to 6). Early (perhaps Hadean) differentiation events that led to a depleted and heterogeneous mantle are apparent in the Nd and Hf isotope systematics of 3.7-3.8 Ga Isua supracrustal rocks. The radiogenic Hf isotopes of the Gadwal boninites and the Hf, Nd isotope systematics of rocks from other locations in the 3.4 to 2.5 Ga time period are consistent with the survival of fragments of an early depleted mantle later in the Archean. From ˜2.0 Ga to present, the time-integrated 176Lu/177Hf and 147Sm/144Nd of the depleted mantle appears nearly constant and similar to the present day average MORB source. These data indicate that progressive elimination of early (>4.5 Ga) formed heterogeneities in the depleted mantle dominated the history of the Archean mantle, and that portions of early depleted reservoirs survived through the Mesoarchean. These results have implications for the mixing scales for the early terrestrial mantle and the timing of the initiation of present day plate tectonics.

Khanna, Tarun C.; Bizimis, Michael; Yogodzinski, Gene M.; Mallick, Soumen

2014-02-01

173

The Virtual Radiation Belt Observatory  

NASA Astrophysics Data System (ADS)

ViRBO (Virtual Radiation Belt Observatory) is one of the domain-specific virtual observatories funded under the NASA Heliophysics Data Environment (HPDE) program that began development in 2006. In this work, we report on the search, display, and data access functionality of ViRBO along with plans for interaction with upcoming missions, including Radiation Belt Storms Probes (RBSP). We also describe the relationship between the services and data provided by ViRBO and the general architecture of the HPDE and the plan articulated in the 2010 Senior Review of Data Centers. The lessons learned in the development of ViRBO include issues related to (1) creating a user base given the limits of the types of activities a virtual observatory are charged with supporting and (2) dealing with limitations on existing software and standards when developing data services.

Weigel, R. S.; O'Brien, T. P.; Friedel, R. H.; Green, J. C.; Zhizhin, M.; Mishin, D. Y.

2010-12-01

174

The Scattered Kuiper Belt Objects  

NASA Astrophysics Data System (ADS)

We describe a continuing survey of the Kuiper Belt conducted at the 3.6-m Canada France Hawaii Telescope on Mauna Kea, Hawaii. The survey employs a 12288 x 8192 pixel CCD mosaic to image the sky to red magnitude 24. All detected objects are targeted for systematic follow-up observations, allowing us to determine their orbital characteristics. Three new members of the rare Scattered Kuiper Belt Object class have been identified, bringing the known population of such objects to four. The SKBOs are thought to have been scattered outward by Neptune, and are a potential source of the short-period comets. Using a Maximum Likelihood method, we place observational constraints on the total number and mass of the SKBOs.

Trujillo, C. A.; Jewitt, D. C.; Luu, J. X.

1999-09-01

175

China belting up or down? Seat belt wearing trends in Nanjing and Zhoushan  

Microsoft Academic Search

National seat belt wearing legislation became effective in China May 2004 and associated provincial and city regulations followed. Despite rapid motorisation seat belt studies in China have been scarce. Patterns and trends in urban seat belt wearing were observed for all driver, front and rear seating positions over the years 2005–2007 in two eastern cities Nanjing (Jiangsu Province) and Zhoushan

Virginia Routley; Joan Ozanne-Smith; Dan Li; Min Yu; Jianyue Wang; Junhe Zhang; Zhendong Tong; Ming Wu; Peihua Wang; Yu Qin

2008-01-01

176

Kuiper belts around nearby stars  

NASA Astrophysics Data System (ADS)

Context. The existence of dusty debris disks around a large fraction of solar type main-sequence stars, inferred from excess far-IR and submillimetre emission compared to that expected from stellar photospheres, suggests that leftover planetesimal belts analogous to the asteroid- and comet reservoirs of the solar system are common. Aims: Sensitive submillimetre observations are essential to detect and characterise cold extended dust originating from collisions of small bodies in disks, belts, or rings at Kuiper-belt distances (30-50 AU or beyond). Measurements of the flux densities at these wavelengths will extend existing IR photometry and permit more detailed modelling of the Rayleigh-Jeans tail of the disks spectral energy distribution (SED), effectively constraining dust properties and disk extensions. By observing stars spanning from a few up to several hundred Myr, the evolution of debris disks during crucial phases of planet formation can be studied. Methods: We observed 22 exo-Kuiper-belt candidates at 870 ?m, as part of a large programme with the LABOCA bolometer at the APEX telescope. Dust masses (or upper limits) were calculated from integrated 870 ?m fluxes, and fits to the SED of detected sources revealed the fractional dust luminosities fdust, dust temperatures Tdust, and power-law exponents ? of the opacity law. Results: A total of 10 detections with at least 3? significance were made, out of which five (HD 95086, HD 131835, HD 161868, HD 170773, and HD 207129) have previously never been detected at submillimetre wavelengths. Three additional sources are marginally detected with > 2.5? significance. The best-fit ? parameters all lie between 0.1 and 0.8, in agreement with previous results indicating the presence of significantly larger grains than those in the ISM. From our relatively small sample we estimate fdust ? t-?, with ? ~ 0.8-2.0, and identify an evolution of the characteristic radial dust distance Rdust that is consistent with the t1/3 increase predicted from models of self-stirred collisions in debris disks. Based on observations with APEX, Llano Chajnantor, Chile (OSO programme 081.F-9330(A)).

Nilsson, R.; Liseau, R.; Brandeker, A.; Olofsson, G.; Pilbratt, G. L.; Risacher, C.; Rodmann, J.; Augereau, J.-C.; Bergman, P.; Eiroa, C.; Fridlund, M.; Thébault, P.; White, G. J.

2010-07-01

177

Understanding Quaternions and the Dirac Belt Trick  

ERIC Educational Resources Information Center

The Dirac belt trick is often employed in physics classrooms to show that a 2n rotation is not topologically equivalent to the absence of rotation whereas a 4n rotation is, mirroring a key property of quaternions and their isomorphic cousins, spinors. The belt trick can leave the student wondering if a real understanding of quaternions and spinors…

Staley, Mark

2010-01-01

178

Apparatus for heat treating plastic belts  

NASA Technical Reports Server (NTRS)

Apparatus performs programed rotating, stretching/shrinking and heat treatment necessary to fabrication of high-performance plastic belts. Belts can be treated in lengths varying from 7 to 48 in., in widths up to 1 in., and in thicknesses up to approximately 0.003 in.

Topits, A., Jr.

1975-01-01

179

Resonant structure of the outer asteroid belt  

Microsoft Academic Search

An analysis of ordered and chaotic regions of motion in the outer asteroid belt has shown that once the eccentricity of Jupiter is introduced the chaotic regions of the circular model are quite easily depleted. This suggests that also objects in neighbouring regions must be strongly perturbed. Therefore it is not surprising that many outer belt asteroids have been reported

Andrea Milani; Anna M. Nobili

1984-01-01

180

The Aster's Hoity-Toity Belt  

E-print Network

The Aster's Hoity-Toity Belt Written by Jacinta Behne, McREL for NASA's Dawn Mission So, at the end was "Aster's Hoity-Toity Belt," but that was a thing of the past. Today, the Asters are a close, loving Carousel or the Asters "hoity-toity." And that's how we've come to know what today we call the Asteroid

181

Hannes: A mission to the asteroid belt  

Microsoft Academic Search

An asteroid belt mission is being studied by Swedish space authorities in cooperation with Russian, European, and American partners. The mission will perform a survey of the inner solar system with an emphasis on cosmogonic issues, i.e. it will study the importance of plasma processes in the formation and evolution of the solar system. For this purpose the asteroid belt

P. Rathsman; S. Grahn; S. Barabash; M. Yamauchi; A. Sukhanov; A. Zakharov; G. Marklund; C.-I. Lagerqvist; P. Magnusson; J. Woch

1996-01-01

182

DESIGN AND OPERATION OF BELT FILTER PRESSES  

EPA Science Inventory

Because early models of belt filter presses (developed from technology associated with the manufacture of paper) performed poorly, improved design and operation procedures for these presses were studied. Belt filter presses form part of a sludge dewatering system, and in terms of...

183

Use of seatbelts in cars with automatic belts.  

PubMed Central

Use of seatbelts in late model cars with automatic or manual belt systems was observed in suburban Washington, DC, Chicago, Los Angeles, and Philadelphia. In cars with automatic two-point belt systems, the use of shoulder belts by drivers was substantially higher than in the same model cars with manual three-point belts. This finding was true in varying degrees whatever the type of automatic belt, including cars with detachable nonmotorized belts, cars with detachable motorized belts, and especially cars with nondetachable motorized belts. Most of these automatic shoulder belts systems include manual lap belts. Use of lap belts was lower in cars with automatic two-point belt systems than in the same model cars with manual three-point belts; precisely how much lower could not be reliably estimated in this survey. Use of shoulder and lap belts was slightly higher in General Motors cars with detachable automatic three-point belts compared with the same model cars with manual three-point belts; in Hondas there was no difference in the rates of use of manual three-point belts and the rates of use of automatic three-point belts. PMID:1561301

Williams, A F; Wells, J K; Lund, A K; Teed, N J

1992-01-01

184

The Gould's Belt Distances Survey  

E-print Network

Very Long Baseline Interferometry (VLBI) observations can provide the position of compact radio sources with an accuracy of order 50 micro-arcseconds. This is sufficient to measure the trigonometric parallax and proper motions of any object within 500 pc of the Sun to better than a few percent. Because they are magnetically active, young stars are often associated with compact radio emission detectable using VLBI techniques. Here we will show how VLBI observations have already constrained the distance to the most often studied nearby regions of star-formation (Taurus, Ophiuchus, Orion, etc.) and have started to provide information on their internal structure and kinematics. We will then briefly describe a large project (called The Gould's Belt Distances Survey) designed to provide a detailed view of star-formation in the Solar neighborhood using VLBI observations.

Loinard, Laurent

2012-01-01

185

The Gould's Belt distance survey  

NASA Astrophysics Data System (ADS)

Very Long Baseline Interferometry (VLBI) observations can provide the position of compact radio sources with an accuracy of order 50 micro-arcseconds. This is sufficient to measure the trigonometric parallax and proper motions of any object within 500 pc of the Sun to better than a few percent. Because they are magnetically active, young stars are often associated with compact radio emission detectable using VLBI techniques. Here we will show how VLBI observations have already constrained the distance to the most often studied nearby regions of star-formation (Taurus, Ophiuchus, Orion, etc.) and have started to provide information on their internal structure and kinematics. We will then briefly describe a large project (called The Gould's Belt Distance Survey) designed to provide a detailed view of star-formation in the Solar neighborhood using VLBI observations.

Loinard, L.; Mioduszewski, A. J.; Torres, R. M.; Dzib, S.; Rodríguez, L. F.; Boden, A. F.

2011-10-01

186

The Gould's Belt distance survey  

E-print Network

Very Long Baseline Interferometry (VLBI) observations can provide the position of compact radio sources with an accuracy of order 50 micro-arcseconds. This is sufficient to measure the trigonometric parallax and proper motions of any object within 500 pc of the Sun to better than a few percent. Because they are magnetically active, young stars are often associated with compact radio emission detectable using VLBI techniques. Here we will show how VLBI observations have already constrained the distance to the most often studied nearby regions of star-formation (Taurus, Ophiuchus, Orion, etc.) and have started to provide information on their internal structure and kinematics. We will then briefly describe a large project (called The Gould's Belt Distance Survey) designed to provide a detailed view of star-formation in the Solar neighborhood using VLBI observations.

Loinard, L; Torres, R M; Dzib, S; Rodriguez, L F; Boden, A F

2011-01-01

187

Origin of the asteroid belt  

NASA Technical Reports Server (NTRS)

Earlier and current concepts relevant to the origin of the asteroid belt are discussed and are considered in the framework of the solar system origin. Numerical and analytical solutions of the dynamical theory of planetesimal accumulation are characterized by bifurcations into runaway and nonrunaway solutions, and it is emphasized that the differences in time scales resulting from runaway and nonrunaway growth can be more important than conventional time scale differences determined by heliocentric distances. It is concluded that, in principle, it is possible to combine new calculations with previous work to formulate a theory of the asteroidal accumulation consistent with the meteoritic record and with work on the formation of terrestrial planets. Problems remaining to be addressed before a mature theory can be formulated are discussed.

Wetherill, George W.

1989-01-01

188

Electric filter with movable belt electrode  

DOEpatents

A method and apparatus for removing airborne contaminants entrained in a gas or airstream includes an electric filter characterized by a movable endless belt electrode, a grounded electrode, and a filter medium sandwiched there between. Inclusion of the movable, endless belt electrode provides the driving force for advancing the filter medium through the filter, and reduces frictional drag on the filter medium, thereby permitting a wide choice of filter medium materials. Additionally, the belt electrode includes a plurality of pleats in order to provide maximum surface area on which to collect airborne contaminants. 4 figs.

Bergman, W.

1983-09-20

189

Depletion of the Outer Asteroid Belt  

PubMed

During the early history of the solar system, it is likely that the outer planets changed their distance from the sun, and hence, their influence on the asteroid belt evolved with time. The gravitational influence of Jupiter and Saturn on the orbital evolution of asteroids in the outer asteroid belt was calculated. The results show that the sweeping of mean motion resonances associated with planetary migration efficiently destabilizes orbits in the outer asteroid belt on a time scale of 10 million years. This mechanism provides an explanation for the observed depletion of asteroids in that region. PMID:8994031

Liou; Malhotra

1997-01-17

190

Noble metal abundances in an early Archean impact deposit  

NASA Technical Reports Server (NTRS)

Detailed analyses are reported on the concentrations of the noble metals Pd, Os, Ir, Pt, and Au in an early Archean spherule bed (S4) of probably impact origin from the lower Fig Tree Group, Barberton Greenstone Belt, South Africa. Compared to other sedimentary deposits of known or suspected impact origin, some noble metals are present in exceptionally high concentrations. Noble metal abundances are fractionated relative to abundances in chondrites with ratios of Os/Ir, Pt/Ir, Pd/Ir, and Au/Ir at only 80, 80, 41, and 2 percent of these values on CI chondrites. Although an extraterrestrial source is favored for the noble metal enrichment, the most plausible cause of the fractionation is by regional hydrothermal/metasomatic alteration.

Kyte, Frank T.; Zhou, Lei; Lowe, Donald R.

1992-01-01

191

Early Archean Spherule Beds-Confirmation of Impact Origin  

NASA Technical Reports Server (NTRS)

The oldest record of major impact events on Earth may be a number of early Archean (3.5 to 3.2 Ga) spherule beds that have been identified in the Barberton Greenstone Belt, South Africa. Several field, petrographic, and geochemical criteria distinguish these beds from typical volcanic and clastic sediments. These criteria include the wide geographic distribution of two beds in a variety of depositional environments, the presence of relict quench textures, absence of juvenile volcaniclastic debris within the beds, and extreme enrichment of Ir and other platinum group elements (PGE) as compared to surrounding sediments. Some researchers, however, argued for a terrestrial origin for spherule bed formation, possibly related to volcanism and gold mineralization.

Shukolyukov, A.; Kyte, F. T.; Lugmair, G. W.; Lowe, D. R.; Byerly, G. R.

2000-01-01

192

Magmatism and Tectonics in the Meso-Archean Pongola Supergroup, South Africa  

NASA Astrophysics Data System (ADS)

The Pongola Supergroup is one of the most extensive and well preserved volcano-sedimentary successions emplaced in a continental setting in the Meso-Archean (c. 2.95 Ga). It contrasts with both the older (Barberton type c.3.5 Ga) and younger (Belingwe type c.2.7 Ga) greenstone belts in southern Africa in that the sequence has not undergone the strong horizontal compressional tectonics typically related to greenstone belt-TTG environments. However, it is appropriate to compare this sequence with rocks of the Barberton greenstone belt by which the final phase of deposition preceded that of the juxtaposed Pongola basin with a relatively small time interval. The Pongola succession, which commenced with the first major magmatic event after the Barberton greenstone belt, overlies granitoids and remnants of greenstone belts in SE South Africa and in SW Swaziland. Formation was not in a continental rift environment but most likely in a marginal epicontinental basin with syn-depositional subsidence in a half-graben fault system in the type area. The Pongola rocks occur in two domains related to a NW-trending central basement high in the Kaapvaal Craton and achieving a maximum thickness of 8 km in the northern areas. The lower section (Nsuze group 3.7 km thick) is made up mainly of lavas and pyroclastic rocks and the upper section (Mozaan Group 4.3 km thick) is aranaceous sediments and argillites with a thick volcanic unit observed in the south-eastern facies. Chemical affinities of the lavas include tholeiite and calc-alkaline over the compositional range of basalt to rhyolite. There is a preponderance of andesites in the compositional array. The preservation of these rocks gives insight into the range of volcanic processes that took place at this stage of Earth history and in some areas it is possible to identify eruptions from a single source over several kilometres, as well as feeder-dyke systems to the lava flows. Simultaneous eruption of contrasting magmas from several vents is a feature of this uniquely preserved magmatic record. New precise zircon U-Pb ages give an indication that the entire basin formed in a remarkably short period of geological time between 2980 ±10 Ma and 2954 ±9 Ma, although complications arising from inherited zircons cannot be ruled out. While komatiites are not present in the Pongola a sequence of volcaniclastic rocks with well-preserved bombs of picrite composition and contained within a sandy matrix gives rise to a geochemical signature high in Cr and Ni which is the first evidence of an ultramafic component to this succession. Evidence of rapid deposition, a preponderance of intermediate lavas, discordance of bounding (earlier) crustal blocks and consistent structural trends in the area, are similar to features found in continental arc basins currently observed in the south-western USA, and may present an alternative model to those currently accepted for Archean terranes in early-formed cratons.

Wilson, Allan

2013-04-01

193

Seat belt use among African Americans, Hispanics, and Whites  

Microsoft Academic Search

Objectives: This study investigated seat belt use among White, Black, and Hispanic drivers, in cities in which standard enforcement of the belt use law is permitted (primary enforcement) and in cities in which a motorist has to be first cited for another offense (secondary enforcement). Socioeconomic and gender differences in belt use were also studied. Methods: Belt use observations were

JoAnn K. Wells; Allan F. Williams; Charles M. Farmer

2002-01-01

194

The Lifetime of Ice on Main Belt Asteroids  

E-print Network

The Lifetime of Ice on Main Belt Asteroids Norbert Sch¨orghofer University of Hawaii Astrophysical, and others #12;Main Belt Comets (MBCs) cometary activity asteroidal orbit Capture of minor bodies from other reservoirs into stable main belt asteroid orbits is rare MBCs have been in the main belt for a long time

Schörghofer, Norbert

195

INCREASED POWER DENSITY OF PUSH-BELT CVTs USING A NEW MARAGING STEEL FOR BELT MANUFACTURE  

Microsoft Academic Search

Since the commercial introduction of push-belt type continuously variable transmission (CVT) systems, customer specifications concerning power density (transmittable power, torque, transmission size, ratio coverage, and durability) have become increasingly demanding. Consequently, the increase of push-belt power density is a permanent goal for Van Doorne's Transmissie, Bosch Group. Maximum power density is mainly determined by the ability of the push-belt rings

Bert Pennings; Minh-Duc Tran; Michel Derks; Arjen Brandsma

196

Safety Belt Laws and Disparities in Safety Belt Use Among US High-School Drivers  

PubMed Central

Objectives. We compared reported safety belt use, for both drivers and passengers, among teenagers with learner’s permits, provisional licenses, and unrestricted licenses in states with primary or secondary enforcement of safety belt laws. Methods. Our data source was the 2006 National Young Driver Survey, which included a national representative sample of 3126 high-school drivers. We used multivariate, log-linear regression analyses to assess associations between safety belt laws and belt use. Results. Teenaged drivers were 12% less likely to wear a safety belt as drivers and 15% less likely to wear one as passengers in states with a secondary safety belt law than in states with a primary law. The apparent reduction in belt use among teenagers as they progressed from learner to unrestricted license holder occurred in only secondary enforcement states. Groups reporting particularly low use included African American drivers, rural residents, academically challenged students, and those driving pickup trucks. Conclusions. The results provided further evidence for enactment of primary enforcement provisions in safety belt laws because primary laws are associated with higher safety belt use rates and lower crash-related injuries and mortality. PMID:22515851

Winston, Flaura K.; Durbin, Dennis R.

2012-01-01

197

A study of binary Kuiper Belt objects  

E-print Network

About 105 bodies larger than 100km in diameter (Jewitt 1998) reside in the Kuiper Belt, beyond the orbit of Neptune. Since 1992 observational surveys have discovered over one thousand of these objects, believed to be fossil ...

Kern, Susan Diane

2006-01-01

198

Visualization of Radiation Belts from REPT Data  

NASA Video Gallery

This visualization, created using actual data from the Relativistic Electron-Proton Telescopes (REPT) on NASAâ??s Van Allen Probes, clearly shows the emergence of new third belt and second slot reg...

199

Seat Belt Use in 2012 - Overall Results  

MedlinePLUS

... contract number DTNH22-07-D-00057. Table 3 States With Primary Enforcement Seat Belt Laws* Alabama Alaska Arkansas California Connecticut Delaware District of Columbia Florida Georgia Hawaii Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland ...

200

14 CFR 31.63 - Safety belts.  

Code of Federal Regulations, 2012 CFR

...TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.63 Safety belts...subpart C of this part. (b) This section does not apply to balloons that incorporate a basket or gondola. [Amdt....

2012-01-01

201

14 CFR 31.63 - Safety belts.  

Code of Federal Regulations, 2010 CFR

...TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.63 Safety belts...Subpart C of this part. (b) This section does not apply to balloons that incorporate a basket or gondola. [Amdt....

2010-01-01

202

14 CFR 31.63 - Safety belts.  

Code of Federal Regulations, 2011 CFR

...TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Design Construction § 31.63 Safety belts...Subpart C of this part. (b) This section does not apply to balloons that incorporate a basket or gondola. [Amdt....

2011-01-01

203

Gaps in the Earths Radiation Belts  

NSDL National Science Digital Library

The Earth's radiation belts (violet & white) change considerably due to a number of influences, ranging from a changing solar wind to the lightning on the Earth. Here we see a range of variation in the electron flux in early December 2003. White indicates higher electron flux than violet. The gray curves represent the lines of the Earth's magnetic field. These radiation belts are constructed on a per-orbit basis with data from SAMPEX.

Bridgman, Tom; Green, James

2005-03-08

204

A photometric survey of outer belt asteroids  

NASA Technical Reports Server (NTRS)

Since 1989, we have been conducting a research program devoted to the study of the Trojans and outer belt asteroids (Hilda and Cybele groups), in order to characterize their rotational properties and shapes. As an outcome of several observational campaigns, we determined rotational periods and lightcurve amplitudes for 23 distant asteroids, using both CCD and photoelectric photometry. In this paper, we compare the rotational properties of main belt asteroids and Trojans, based on the preliminary results of this survey.

Dimartino, M.; Gonano-Beurer, M.; Mottola, Stefano; Neukum, G.

1992-01-01

205

The geological record of life 3500 Ma ago: Coping with the rigors of a young earth during late accretion  

NASA Technical Reports Server (NTRS)

Thin cherty sedimentary layers within the volcanic portions of the 3,500 to 3,300 Ma-old Onverwacht and Fig Tree Groups, Barberton Greenstone belt, South Africa, and Warrawoona Group, eastern Pilbara Block, Western Australia, contain an abundant record of early Archean life. Five principal types of organic and probably biogenic remains and or structures can be identifed: stromatolites, stromatolite detritus, carbonaceous laminite or flat stromalite, carbonaceous detrital particles, and microfossils. Early Archean stromatolites were reported from both the Barberton and eastern Pilbara greenstone belts. Systematic studies are lacking, but two main morphological types of stromatolites appear to be represented by these occurrences. Morphology of the stromalites is described. Preserved early Archean stromatolites and carbonaceous matter appear to reflect communities of photosynthetic cyanobacteria inhabiting shallow, probably marine environments developed over the surfaces of low-relief, rapidly subsiding, simatic volcanic platforms. The overall environmental and tectonic conditions were those that probably prevailed at Earth's surface since the simatic crust and oceans formed sometime before 3,800 Ma. Recent studies also suggest that these early Archean sequences contain layers of debris formed by large-body impacts on early Earth. If so, then these early bacterial communities had developed strategies for coping with the disruptive effects of possibly globe-encircling high-temperature impact vapor clouds, dust blankets, and impact-generated tsunamis. It is probable that these early Archean biogenic materials represent organic communities that evolved long before the beginning of the preserved geological record and were well adapted to the rigors of life on a young, volcanically active Earth during late bombardment. These conditions may have had parallels on Mars during its early evolution.

Lowe, Donald R.

1989-01-01

206

Decay rate of the second radiation belt  

NASA Technical Reports Server (NTRS)

Variations in the Earth's trapped (Van Allen) belts produced by solar flare particle events are not well understood. Few observations of increases in particle populations have been reported. This is particularly true for effects in low Earth orbit, where manned spaceflights are conducted. This paper reports the existence of a second proton belt and it's subsequent decay as measured by a tissue-equivalent proportional counter and a particle spectrometer on five Space Shuttle flights covering an eighteen-month period. The creation of this second belt is attributed to the injection of particles from a solar particle event which occurred at 2246 UT, March 22, 1991. Comparisons with observations onboard the Russian Mir space station and other unmanned satellites are made. Shuttle measurements and data from other spacecraft are used to determine that the e-folding time of the peak of the second proton belt. It was ten months. Proton populations in the second belt returned to values of quiescent times within eighteen months. The increase in absorbed dose attributed to protons in the second belt was approximately 20%. Passive dosimeter measurements were in good agreement with this value.

Badhwar, G. D.; Robbins, D. E.

1996-01-01

207

Seat belts: personal choice or necessity?  

PubMed

The use of occupant restrains in motor vehicles has become an issue which has received increasing legislative attention in recent years. This has occurred due to the supposition that seat belt use would be effective in preventing automobile related fatalities and injuries. Twenty-five states and the District of Columbia now have mandatory safety belt laws in effect which have increased usage rates from 20% or less prior to enactment of the law to between 50% and 70% after implementation. Safety belts have proven effective in minimizing morbidity and mortality. In a study of four states enforcing mandatory usage and neighboring states without seat belt laws as a comparison, between 250 and 350 fatalities were prevented. This extrapolates to an estimated 12,000-15,000 lives saved nationally if restraints were mandatory. Nebraska is one of two states in which a seat belt law has been enacted and subsequently repealed. As a result of the repeal, seat belt usage dropped from 40% in 1986 to 29% in 1987 with an associated increase in injuries. The economic impact associated with this increase in accident related injuries is enormous. The Nebraska repeal campaign was based on the issue of individual rights versus mandatory safety requirements. As health care providers we need to examine the validity of personal rights in comparison to the documented impact of personal restraints on the morbidity and mortality of accident victims. PMID:2362621

Blatchford, G J; Hill, A A; Edney, J A

1990-05-01

208

Rhyacian (2.23-2.20 Ga) juvenile accretion in the southern São Francisco craton, Brazil: Geochemical and isotopic evidence from the Serrinha magmatic suite, Mineiro belt  

NASA Astrophysics Data System (ADS)

The Serrinha magmatic suite (Mineiro belt) crops out in the southern edge of the São Francisco craton, comprising the Brito quartz-diorite, Brumado de Cima and Brumado de Baixo granodiorites, granophyres and felsic sub-volcanic and volcanic rocks, part of which intruded into the Nazareno greenstone belt. The suite rocks have petrographic features that are consistent with magma supercooling due to the low water content combined with volatile loss, leading to crystallization of quartz and alkaline feldspar at the rims of plagioclase phenocrysts (granophyric intergrowth). The investigated rocks are sub-alkaline, calc-alkaline and show low content in rare earth elements. The U-Pb zircon crystallization ages for the Brumado de Cima granodiorite [2227 ± 22 (23) Ma] and a coeval granophyre [2211 ± 22 (23) Ma], coupled with available single-zircon Pb evaporation ages for the Brito and Brumado de Baixo plutons, are significantly older than the "Minas orogeny" (ca. 2100-2050 Ga) of Quadrilátero Ferrífero area, eastward from the Serrinha suite. Our data establish an early Rhyacian event tectonically linked with the evolution of the Mineiro belt. The bulk Nd isotopic signature [low negative to positive ?Nd(t) values] of the Serrinha samples are consistent with the important role of Paleoproterozoic mantle components in the magma genesis. The integrated geologic, geochemical and isotopic information suggests that Paleoproterozoic evolution of the Mineiro belt initiated in a passive continental margin basin with deposition of the Minas Supergroup at ca. 2500 Ma. This stage was succeeded by outboard rupture of the oceanic lithosphere with development and coalescence of progressively younger magmatic arcs during Rhyacian time. One of the earliest arcs formed the Serrinha suite. The tectonic collage of the Serrinha and Ritápolis (2190-2120 Ma) arcs produced the NE-SW Lenheiro shear zone, resulting in mylonitization and recrystallization of both the granitoid intrusions and host rocks. As a matter of fact juxtaposition of distinct magmatic units in age and origin took place along the Lenheiros structure in this sector of the Mineiro belt.

Ávila, Ciro Alexandre; Teixeira, Wilson; Cordani, Umberto Giuseppe; Moura, Candido Augusto Veloso; Pereira, Ronaldo Mello

2010-03-01

209

Preservation of modern and ancient microbial ichnofossils in basaltic glass by titanite mineralization  

NASA Astrophysics Data System (ADS)

Subaqueous volcanic rocks are a relatively new setting in the search for early life on Earth but recent studies have demonstrated that submarine basaltic glass in pillow rims and hyaloclastites are suitable microbial habitats. Microbes rapidly colonize the glassy surfaces along fractures and cracks that have been exposed to water producing characteristic granular and/or tubular bioalteration structures. The minerals within these structures have been investigated using micro X-ray diffraction that confirms early formation of titanite and other mineral phases associated with microbial alteration structures in modern basaltic glass. Incipient titanite formation in modern samples implies that mineralization of these trace fossils is penecontemporaneous with bioalteration. The early precipitation of sub-micron titanite grains within the biologically etched alteration structures serves as an agent for preservation that may persist for geologically extended periods of time in the absence of later penetrative deformation. Titanite-mineralized microbial alteration structures have been observed in several Archean greenstone belts including the Abitibi greenstone belt (2.7 Ga), Pilbara craton (3.35 Ga), and the Barberton greenstone belt (3.5 Ga). The ubiquity of these bioalteration structures and their relative durability compared with many other purported trace fossils makes them attractive as a biomarker for Archean Earth and, potentially, Mars. Basaltic rocks are commonplace on Mars and could have easily come into contact with water in the past. Archean subaqueous volcanic rocks thus provide an excellent analogue for studies addressing the presence of early life on Mars and the potential for the preservation of traces of microbial life in the Martian crust.

Izawa, M. R.; Bridge, N. J.; Banerjee, N. R.; Flemming, R. L.; Mueller, W.; Muehlenbachs, K.; Chacko, T.

2008-12-01

210

Crustal blocks and accretionnary process in the Southern Damara belt (Namibia), new insights from high-resolution airborne geophysical surveys  

NASA Astrophysics Data System (ADS)

The Damara orogen developed during the pan-African orogeny that led to the assembly of Gondwana at the end of Neoproterozoic. Interpreted as a collision belt, it is divided into a N-S trending coastal arm (the Kaoko belt) and a NE-SW striking inland branch with a width of ca. 400 km, which can be traced for more than 1500 km from Namibia into Botswana and Zambia (Miller, 1983). Subduction of the Kalahari province in the South beneath the Congo province to the North led to the highly asymmetric nature of the Damara orogen. Combined interpretation of existing geological data and new high resolution airborne geophysical data (radiometric and magnetic datasets) has been conducted in the region of Rehoboth, situated within the Southern margin and foreland of the Damara orogen. Three contrasting stages of crustal accretion are differentiated. A Late Paleoproterozoic greenstone belt is mainly composed by large volcanic and plutonic mafic sequences depleted in radioelements. A magnetite-bearing quartzite constitutes a regional marker, followed by well-defined magnetic horizons. A major ignimbrite system, followed by a stage of rifting, is developed during Mesoproterozoic. The felsic volcanic-magmatic suite represents a major input of radioelements in the crust. In general, the introduction of such large amounts of K, Th and U is associated with orogenic and/or subduction processes. Orogenic processes are unlikely as no collision tectonics are recorded during Mesoproterozoic in this zone and an active margin situation (arc, back-arc) is the most probable geodynamic context for this region. The structural pattern within the granitic massifs is marked by: (i) a NW-SE fault system, contemporaneous of granite emplacement, (ii) NE-SW lineaments, in continuity with the Southern Damara shear zone system. Finally, the Neoproterozoic Damara sequence is deposited over this basement. Continental sediments of the Nosib Group display varied sources of eroded material and variation in radioelement content. The base of the Nama marine sediments is marked by a change in radioelement source, being depleted in K-Th and slightly enriched in U. In conclusion, high-resolution geophysical surveys from Namibia provide new datasets, which can be used to produce interpreted geological maps and give new insights on successive accretionnary processes.

Ledru, P.; Becker, T.; Hutchins, D.; Milesi, J. P.; Tourliere, B.; Truffert, C.; Wackerle, R.

2003-04-01

211

IDENTIFYING COLLISIONAL FAMILIES IN THE KUIPER BELT  

SciTech Connect

The identification and characterization of numerous collisional families-clusters of bodies with a common collisional origin-in the asteroid belt has added greatly to the understanding of asteroid belt formation and evolution. More recent study has also led to an appreciation of physical processes that had previously been neglected (e.g., the Yarkovsky effect). Collisions have certainly played an important role in the evolution of the Kuiper Belt as well, though only one collisional family has been identified in that region to date, around the dwarf planet Haumea. In this paper, we combine insights into collisional families from numerical simulations with the current observational constraints on the dynamical structure of the Kuiper Belt to investigate the ideal sizes and locations for identifying collisional families. We find that larger progenitors (r {approx} 500 km) result in more easily identifiable families, given the difficulty in identifying fragments of smaller progenitors in magnitude-limited surveys, despite their larger spread and less frequent occurrence. However, even these families do not stand out well from the background. Identifying families as statistical overdensities is much easier than characterizing families by distinguishing individual members from interlopers. Such identification seems promising, provided the background population is well known. In either case, families will also be much easier to study where the background population is small, i.e., at high inclinations. Overall, our results indicate that entirely different techniques for identifying families will be needed for the Kuiper Belt, and we provide some suggestions.

Marcus, Robert A.; Ragozzine, Darin; Murray-Clay, Ruth A.; Holman, Matthew J., E-mail: rmarcus@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

2011-05-20

212

Structure of the Kuiper Belt Dust Disk  

NASA Astrophysics Data System (ADS)

An overview of the Kuiper belt dust disk is provided in this chapter. Mutual collisions among Kuiper belt objects should produce a dust disk in the outer solar system similar to the observed circumstellar dust disks. As the Kuiper belt dust particles migrate toward the Sun due to Poynting-Robertson drag, they are perturbed by the giant planets. Mean-motion resonances with Neptune and gravitational scattering by Saturn and Jupiter alter their orbital evolution dramatically. Asa result, large-scale structures are created in the disk. Descriptions of the dynamics involved, and the numerical simulations required to unveil the disk features, are included. Implications for extrasolar planet detection from circumstellar dust disk modeling are also discussed.

Liou, J.-C.; Kaufmann, D. E.

213

Illinois PER Interactive Examples: Conveyor Belt  

NSDL National Science Digital Library

This is an interactive homework problem for introductory physics students relating to Newton's Second Law and kinetic friction. A box of known mass is dropped vertically onto a conveyor belt moving at a constant speed. The student must determine how much time it takes for the box to attain the same speed as the conveyor belt. A user-activated "help" sequence is provided for each step of the problem-solving, from conceptual analysis through quantitative calculation. To promote critical thinking, immediate feedback is received for both correct and incorrect responses. This item is part of a larger collection of interactive homework problems for introductory physics.

Gladding, Gary

2008-09-10

214

Electrical resistivity survey for groundwater investigations and shallow subsurface evaluation of the basaltic-greenstone formation of the urban Bulawayo aquifer  

NASA Astrophysics Data System (ADS)

Electrical resistivity surveying methods have been widely used to determine the thickness and resistivity of layered media for the purpose of assessing groundwater potential and siting boreholes in fractured unconfined aquifers. Traditionally, this has been done using one-dimensional (1D) vertical electrical sounding (VES) surveys. However, 1D VES surveys only model layered structures of the subsurface and do not provide comprehensive information for interpreting the structure and extent of subsurface hydro-geological features. As such the incorporation of two-dimensional (2D) geophysical techniques for groundwater prospecting has often been used to provide a more detailed interpretation of the subsurface hydro-geological features from which potential sites for successful borehole location are identified. In this study, 2D electrical resistivity tomography was combined with 1D VES to produce a subsurface resistivity model for assessing the availability of groundwater in the basaltic-greenstone formation of the Matsheumhlope well field in Bulawayo, Zimbabwe. Low resistivity readings (<50 ?m) towards the central region of the study area suggest a high groundwater potential, while high resistivities (>500 ?m) around the western margin of the study area suggests a low groundwater potential. 2D electrical resistivity surveys provide a more detailed subsurface structure and may assist in identifying the configuration of possible fractures which could conduct groundwater into the shallow subsurface of study area. It is concluded that 2D electrical resistivity methods is an effective tool for assessing the availability of groundwater in the highly weathered and fractured basaltic greenstone rocks. The methods provided a more precise hydro-geophysical model for the study area compared to the traditional VES. Results from this study are useful for technical groundwater management as they clearly identified suitable borehole locations for long term groundwater prospecting.

Muchingami, Innocent; Hlatywayo, D. J.; Nel, J. M.; Chuma, C.

215

The Kerala Khondalite Belt (KKB) of Southern India: An ensialic mobile belt  

NASA Technical Reports Server (NTRS)

The Proterozoic Kerala Khondalite belt of the Southern Indian Shield is described, a belt dominated by granulite grade (750 C, 5 to 6 kbar) supracrustal rocks whose protoliths included arkoses and shales with cratonic provenances. Rare earth elements and other geochemical signatures suggest a granitic source for these metasediments, possibly the spatially associated charnockite massifs. The presence of intercalated mafic gneisses, interpreted as basalts, implies a cratonic rift basin rather than a foreland basin setting. It was argued that the Kerala, as well as other early Proterozoic mobile belts formed during abortive continental rifting without major additions of new crust.

Chacko, Thomas; Meen, James K.; Kumar, G. R. Ravindra; Rogers, John J. W.

1988-01-01

216

30 CFR 56.14212 - Chains, ropes, and drive belts.  

Code of Federal Regulations, 2010 CFR

...56.14212 Chains, ropes, and drive belts. Chains, ropes, and drive belts shall be guided mechanically onto moving pulleys, sprockets, or drums except where equipment is designed specifically for hand...

2010-07-01

217

30 CFR 57.14212 - Chains, ropes, and drive belts.  

Code of Federal Regulations, 2010 CFR

...57.14212 Chains, ropes, and drive belts. Chains, ropes, and drive belts shall be guided mechanically onto moving pulleys, sprockets, or drums except where equipment is designed specifically for hand...

2010-07-01

218

30 CFR 57.4263 - Underground belt conveyors.  

Code of Federal Regulations, 2010 CFR

... § 57.4263 Underground belt conveyors. Fire protection shall be provided at the head, tail, drive, and take-up pulleys of underground belt conveyors. Provisions shall be made for extinguishing fires along the beltline. Fire protection...

2010-07-01

219

30 CFR 56.4503 - Conveyor belt slippage.  

Code of Federal Regulations, 2010 CFR

...belt-slippage shall be equipped with a detection system capable of automatically stopping the drive pulley. A person shall attend the belt at the drive pulley when it is necessary to operate the conveyor while temporarily bypassing the automatic...

2010-07-01

220

30 CFR 75.350 - Belt air course ventilation.  

...not be used to provide air to working sections...removed. (1) The belt air course must be separated with permanent ventilation controls from return air courses and from other...entry when the belt air flows over the loading...

2014-07-01

221

33 CFR 142.42 - Safety belts and lifelines.  

...2014-07-01 2014-07-01 false Safety belts and lifelines. 142.42 Section...CONTINENTAL SHELF ACTIVITIES WORKPLACE SAFETY AND HEALTH Personal Protective Equipment § 142.42 Safety belts and lifelines. (a)...

2014-07-01

222

Geochemical consequences of the metasomatic conversion of an Early Archean komatiite sequence into chert  

SciTech Connect

Duchac and Hanor (1985) have demonstrated from field and petrographic evidence that the stratiform, muscovite-bearing cherts of Skokhola Ridge, Barberton Mountain Land, South Africa, represent a pervasively silicified sequence of komatiites and komatiitic basalts of Early Archean age. Most alteration took place early, prior to any significant tectonic deformation. The isovolumetric nature of the alteration, as confirmed by excellent preservation of igneous textures, and the immobility of Al make it possible to quantify elemental gains and losses during metasomatism. The sequence was strongly depleted in Na, Mg, Ca, Sr, Fe, and Mn, and enriched in K, Rb, and Ba, Al, Y, Zr, Ti, and P were immobile. It is most likely that the sequence was altered by large volumes of ascending hydrothermal solutions, with the decrease in T upward favoring precipitation of silica and muscovite. The net effect was to convert an ultramafic igneous rock into a rock having a composition approaching that of the average sandstone. Such alteration, if regionally extensive, undoubtedly affected the geochemical evolution of both the Early Archean crust and hydrosphere in the Barberton greenstone belt.

Hanor, J.S.; Duchac, K.C.

1985-01-01

223

Confirmation of the Carolina slate belt as an exotic terrane.  

PubMed

An assemblage of Middle Cambrian Atlantic faunal province trilobites has been found in the rocks of the Carolina slate belt near Batesburg, South Carolina. Geologic and paleomagnetic data suggest that the Carolina slate belt and the adjacent Charlotte belt constitute an exotic terrane that was accreted to North America in early to middle Paleozoic time. PMID:17787733

Secor, D T; Samson, S L; Snoke, A W; Palmer, A R

1983-08-12

224

Geoecological reconnaissance in the Alpine belt of Southern Tibet  

Microsoft Academic Search

Along with four vegetation profiles taken in 1984 in S Tibet climatically induced regressive plant successions were observed. Recently, frost heaving-adapted plant communities of the free gelifluction belt have been descending toward the alpine belt. The hypso-zonal cyperaceae turfs of the alpine belt have been exfoliated by the Himalaya föhn, and the alpine steppe communities have been advancing for an

Georg Miehe

1988-01-01

225

A contribution to the kinematics of the Gould Belt  

Microsoft Academic Search

Observation data on O and B stars given by Lesh (1968, 1972) are used to investigate the velocity field of 818 stars within 2000 pc of the sun. An attempt was made to separate the Gould Belt from the galactic belt and to determine the parameters of the velocity field in both belts. The findings indicate that within the Gould

A. Tsioumis; W. Fricke

1979-01-01

226

46 CFR 111.105-27 - Belt drives.  

Code of Federal Regulations, 2010 CFR

...111.105-27 Belt drives. Each belt drive in a hazardous location must have: (a) A conductive belt; and (b) Pulleys, shafts, and driving equipment grounded to meet NFPA 77 (incorporated by reference, see 46 CFR 110.10-1)....

2010-10-01

227

Seat belts and trauma: Clinical clues for the surgeon  

Microsoft Academic Search

Since their introduction over 30 years ago, seat belts have reduced the overall mortality associated with motor vehicle accidents by as much as 50%. The position and adjustment of the seat belt appear to play an important role in preventing injury. The lap portion of the belt should be kept low on the abdomen at the level of the anterior

Jeanette M. Dolezal; Paul R. G. Cunningham

1999-01-01

228

Geological Processes on Kuiper Belt Objects  

E-print Network

in the Kuiper Belt. a = 39.5 AU Discovered February 18, 1930, at Lowell Observatory, Flagstaff, Arizona Naval Observatory M = 1.52 x 1021 kg, R = 603 km, = 1.65 g cm-3 Synthetic map by Marc Buie Charon #12 using Keck telescopes in Hawaii a = 68 AU (scattered disk) Surface is just like Pluto's: N2, CH4 M = 1

Shumway, John

229

SAMPEX: A Remarkable Radiation Belt Sentinel  

NASA Astrophysics Data System (ADS)

The NASA SAMPEX spacecraft launched in 1992 is expected to end its mission by December 2012 due to re-entry into the Earth's atmosphere. This space platform has revolutionized our views of the dynamic radiation belt environment. We show, using the SAMPEX data, that the near-Earth region of the magnetosphere responds powerfully to changes of driving forces from the Sun and the solar wind. The Earth's radiation belts and inner magnetosphere exhibit substantial differences in their characteristics as the Sun's magnetic field and solar wind plasma properties change over the approximately 11-year solar activity cycle. Solar coronal holes produce regular, recurrent fast solar wind streams in geospace, often enhancing highly relativistic electrons and causing recurrent geomagnetic storms. These phenomena are characteristic of the approach to sunspot minimum. On the other hand, major geomagnetic disturbances associated with aperiodic coronal mass ejections occur most frequently around sunspot maximum. Such disturbances also can often produce significant radiation belt enhancements. We describe the observational results that characterize the differences throughout the inner part of geospace during the course of the solar activity cycle. We conclude that SAMPEX has been a most successful and impactful mission for radiation belt studies.

Baker, D. N.

2012-12-01

230

Radiation Belts of Antiparticles in Planetary Magnetospheres  

Microsoft Academic Search

The Earth's radiation belts could be populated, besides with electrons and protons, also by antiparticles, such as positrons (Basilova et al., 1982) and antiprotons (pbar). Positrons are born in the decay of pions that are directly produced in nuclear reactions of trapped relativistic inner zone protons with the residual atmosphere at altitudes in the range of about 500 to 3000

G. I. Pugacheva; A. A. Gusev; U. B. Jayanthi; I. M. Martin; W. N. Spjeldvik

2007-01-01

231

Glauconite from the precambrian belt series, Montana  

USGS Publications Warehouse

Glauconite from the upper part of the Missoula Group of the Belt Series, Flathead County, Montana, has been dated at 1070 million years by potassium-argon and rubidium-strontium analyses. This is the first glauconite of Precambrian age reported in North America.

Gulbrandsen, R.A.; Goldich, S.S.; Thomas, H.H.

1963-01-01

232

Ankle injuries caused by seat belts.  

PubMed

Two cases of tri-malleolar frautures of the ankle caused by feet becoming entangled in loose seat belts are reported. Open reduction and internal fixation of all three malleolar fragments was carried out in each case with a satisfactory end result. PMID:478628

Dounis, E

1979-05-01

233

Radiation Belts Throughout the Solar System  

NASA Astrophysics Data System (ADS)

The several preceding decades of deep space missions have demonstrated that the generation of planetary radiation belts is a universal phenomenon. All strongly magnetized planets show well developed radiation regions, specifically Earth, Jupiter, Saturn, Uranus, and Neptune. The similarities occur despite the tremendous differences between the planets in size, levels of magnetization, external environments, and most importantly, in the fundamental processes that power them. Some planets like Jupiter are powered overwhelmingly by planetary rotation, much like astrophysical pulsars, whereas others, like Earth and probably Uranus, are powered externally by the interplanetary environment. Uranus is a particularly interesting case in that despite the peculiarities engendered by its ecliptic equatorial spin axis orientation, its magnetosphere shows dynamical behavior similar to that of Earth as well as radiation belt populations and associated wave emissions that are perhaps more intense than expected based on Earth-derived theories. Here I review the similarities and differences between the radiation regions of radiation belts throughout the solar system. I discuss the value of the comparative approach to radiation belt physics as one that allows critical factors to be evaluated in environments that are divorced from the special complex conditions that prevail in any one environment, such as those at Earth.

Mauk, B. H.

2008-12-01

234

Mean motion resonances. [of asteroid belt structure  

NASA Technical Reports Server (NTRS)

Recent research on the resonant structure of the asteroid belt is reviewed. The resonant mechanism is discussed, and analytical models for the study of mean motion resonances are examined. Numerical averaging methods and mapping methods are considered. It is shown how fresh insight can be obtained by means of a new semianalytical approach.

Froeschle, CL.; Greenberg, R.

1989-01-01

235

The importance of exploring the asteroid belt.  

PubMed

Following life's innate tendency to expand into every available space, technological civilizations will inevitably colonize the entire galaxy establishing space habitats around all its well-behaved stars. The most reasonable place in our solar system to test this possibility is the asteroid belt, which is an ideal source of raw materials for space colonies. PMID:11541562

Papagiannis, M D

1983-01-01

236

Hidden Mass in the Asteroid Belt  

Microsoft Academic Search

The total mass of the asteroid belt is estimated from an analysis of the motions of the major planets by processing high precision measurements of ranging to the landers Viking-1, Viking-2, and Pathfinder (1976–1997). Modeling of the perturbing accelerations of the major planets accounts for individual contributions of 300 minor planets; the total contribution of all remaining small asteroids is

G. A. Krasinsky; E. V. Pitjeva; M. V. Vasilyev; E. I. Yagudina

2002-01-01

237

The Gould Belt, the de Vaucouleurs-Dolidze Belt, and the Orion Arm  

E-print Network

Based on masers with measured trigonometric parallaxes, we have redetermined the spatial orientation parameters of the Local (Orion) arm. Using 23 sources (the Gould Belt objects were excluded), we have found that their spatial distribution can be approximated by a very narrow ellipsoid elongated in the direction L_1=77.1+/-2.9^o whose symmetry plane is inclined to the Galactic plane at an angle of 5.6+/-0.2^o. The longitude of the ascending node of the symmetry plane is l_\\Omega=70+/-3^o. A new estimate for the pitch angle of the Local spiral arm has been obtained by an independent method: i=12.9+/-2.9^o. Previously, a belt of young B stars, the de Vaucouleurs.Dolidze belt, was pointed out on the celestial sphere with parameters close to such an orientation. We have refined the spatial orientation parameters of this belt based on a homogeneous sample of protostars. The de Vaucouleurs.Dolidze belt can be identified with the Local arm, with the belt proper as a continuous band on the celestial sphere like the ...

Bobylev, V V

2014-01-01

238

VERO cells harbor a poly-ADP-ribose belt partnering their epithelial adhesion belt  

PubMed Central

Poly-ADP-ribose (PAR) is a polymer of up to 400 ADP-ribose units synthesized by poly-ADP-ribose-polymerases (PARPs) and degraded by poly-ADP-ribose-glycohydrolase (PARG). Nuclear PAR modulates chromatin compaction, affecting nuclear functions (gene expression, DNA repair). Diverse defined PARP cytoplasmic allocation patterns contrast with the yet still imprecise PAR distribution and still unclear functions. Based on previous evidence from other models, we hypothesized that PAR could be present in epithelial cells where cadherin-based adherens junctions are linked with the actin cytoskeleton (constituting the adhesion belt). In the present work, we have examined through immunofluorescence and confocal microscopy, the subcellular localization of PAR in an epithelial monkey kidney cell line (VERO). PAR was distinguished colocalizing with actin and vinculin in the epithelial belt, a location that has not been previously reported. Actin filaments disruption with cytochalasin D was paralleled by PAR belt disruption. Conversely, PARP inhibitors 3-aminobenzamide, PJ34 or XAV 939, affected PAR belt synthesis, actin distribution, cell shape and adhesion. Extracellular calcium chelation displayed similar effects. Our results demonstrate the existence of PAR in a novel subcellular localization. An initial interpretation of all the available evidence points towards TNKS-1 as the most probable PAR belt architect, although TNKS-2 involvement cannot be discarded. Forthcoming research will test this hypothesis as well as explore the existence of the PAR belt in other epithelial cells and deepen into its functional implications. PMID:25332845

Vilchez Larrea, Salome C.; Kun, Alejandra

2014-01-01

239

Palaeomagnetism of Archaean age rocks - what, how, and why?  

NASA Astrophysics Data System (ADS)

The extraordinary stability of remanent magnetisation held in some naturally-occurring ferromagnetic particles implies that even rocks that are billions of years old may record the ambient magnetic field conditions from the time that they formed. Certain rocks from the Barberton Greenstone Belt have demonstrated such a capacity and therefore represent an invaluable resource for palaeomagnetic studies of the early Earth. Here we review the challenges, successes, motivations, and future potential of palaeomagnetic studies applied to Archaean-age rocks in the context of the drill cores recently collected from the Barberton Greenstone Belt. The aims of such studies are two-fold: to study the geomagnetic field itself, and to use the direction of the field as preserved in the rocks to delineate polar wander. The Earth's magnetic field is generated in the core of the planet but also shields the atmosphere from erosion by the solar wind (which was much stronger in the Archaean). Consequently, the geomagnetic application of palaeomagnetism can inform us about conditions both at the surface and in the deep interior of the planet. Notable recent successes in this area include relatively robust observations that convection within the Earth's core was sustaining a stable field that appeared similar in character to today's 3.5 billion years ago and indeed that it was more stable on average 2.5 billion years ago than in the last few hundreds of millions of years. Observations of polar wander are more ambiguous. In the first instance, it is extremely difficult in such old rocks to distinguish apparent polar wander resulting from tectonic drift from that due to "true polar wander" - the motion of the entire crust and mantle relative to the Earth's rotation axis. Nevertheless, both of these are ultimately a consequence of mantle convection and therefore firm constraints on rates of simply "polar wander", would still be a useful constraint on geodynamic processes. Published palaeomagnetic results from the Pilbara Craton in Australia have been used to argue that rates of polar wander 3.5 billion years ago was up to five times faster than they are today. These controversial claims have not been backed up by preliminary results emerging from the palaeomagnetic study of Barberton rocks, however. These rather support that the Onverwacht formation did not drift far from the equator for the ~ 30 million year period during which the rocks comprising it formed.

Biggin, Andy; Roberts-Artal, Laura; Langereis, Cor

2013-04-01

240

Dynamics of a belt-drive system using a linear complementarity problem for the belt pulley contact description  

NASA Astrophysics Data System (ADS)

The aim of this study was to develop an efficient and realistic numerical model in order to predict the dynamic response of belt drives. The belt was modeled as a planar beam element based on an absolute nodal coordinate formulation. A viscoelastic material was adopted for the belt and the corresponding damping and stiffness matrices were determined. The belt-pulley contact was formulated as a linear complementarity problem together with a penalty method. This made it possible for us to accurately predict the contact forces, including the stick and slip zones between the belt and the pulley. The belt-drive model was verified by comparing it with the available analytical solutions. A good agreement was found. Finally, the applicability of the method was demonstrated by considering non-steady belt-drive operating conditions.

?epon, Gregor; Boltežar, Miha

2009-01-01

241

Geoelectric structure of the Dharwar Craton from magnetotelluric studies: Archean suture identified along the Chitradurga-Gadag schist belt  

NASA Astrophysics Data System (ADS)

Broad-band magnetotelluric data were collected at 50 stations over a 400 km long, approximately east-west profile over the granite-greenstone terrain of Dharwar, southern India. The tensor decomposed data were interpreted using a 2-D inversion scheme. The geoelectric model is suggestive of a suture along the Chitradurga-Gadag schist belt, formed by the thrusting of the West Dharwar Craton beneath its eastern counterpart, with an easterly dip of 20-30°. The thrust proposed here pre-dates the formation of these schists, which occurred during the Late Archean (2600 Ma). The accretionary wedge of the thrust and the depressed part of the West Dharwar Craton may have controlled the emplacement of the Chitradurga-Gadag and Shimoga-Dharwar schists. The subsequent weathering, the several episodes of tectonic activity witnessed during the Precambrian and the vertical block movements caused during the passage of the Indian Plate over the Reunion hotspot may have modified the crust, leading to the present-day geological configuration. Despite its age and several tectonothermal episodes, the signature of this thrust is adequately preserved in the Dharwar Craton. Several similarities with younger sutures, as is evident from the observed relics of the oceanic rocks present along the Chitradurga schist belt, suggest that the tectonic processes leading to this Archean event may have had a close resemblance to those witnessed in recent times. Magnetotelluric studies also image a zone of low resistivity at a depth of 40 km beneath the west Dharwar Craton. This seems to be a regional feature, extending to the north over a distance of at least 250 km beneath the Deccan volcanics. The low heat flow values and the high density associated with this feature make partial melting an unlikely explanation for the low resistivity. The grain boundary graphites and the sulphides deposited in the form of pyrites may have caused the low resistivity in the lithospheric mantle of the West Dharwar Craton, although the fluids generated and trapped in the mantle during the passage of the Indian Plate over the Reunion hotspot in the waning phase of its outburst could also be a possibility. The asthenosphere is delineated at a depth of about 100 km beneath the East Dharwar Craton.

Gokarn, S. G.; Gupta, G.; Rao, C. K.

2004-08-01

242

A belted kingfisher flies above KSC  

NASA Technical Reports Server (NTRS)

A belted kingfisher soars over the Merritt Island National Wildlife Refuge, which shares a boundary with Kennedy Space Center. The pigeon-sized, blue-gray male is identified by the blue-gray breast band; females show a chestnut belly band. The belted kingfisher ranges throughout the United States and Canada, wintering south to Panama and the West Indies. They dive into the water for fish and may also take crabs, crayfish, salamanders, lizards, mice and insects. The 92,000-acre refuge is a habitat for more than 310 species of birds, 25 mammals, 117 fishes and 65 amphibians and reptiles. The marshes and open water of the refuge also provide wintering areas for 23 species of migratory waterfowl, as well as a year-round home for great blue herons, great egrets, wood storks, cormorants, brown pelicans and other species of marsh and shore birds.

1999-01-01

243

Compositional structure of the asteroid belt  

NASA Technical Reports Server (NTRS)

A variety of observations, mainly albedos derived from 10 and 20 micron radiometry and eight-filter broadband spectrophotometry, were used to show that the asteroid belt is highly structured in composition. The bias-corrected distribution from 1.8 to 5.2 A.U. of the previously defined compositional types C,S,E,R, and M, plus type D and the newly described types F and P, are reported on. In terms of the relative abundances of the types discussed, the asteroid belt appears to be composed of at least six major compositionally distinct regions. The inferred composition of the asteroids in each semimajor axis region is consistent with the theory that the asteroids accreted from the solar nebula at or near their present location.

Gradie, J.; Tedesco, E.

1982-01-01

244

Monitoring 2005 Corn Belt Yields From Space  

Microsoft Academic Search

The U.S. corn belt, centered on Illinois, suffered extreme drought conditions during the 2005 growing season (Figure 1). The April-September rainfall ranked 10th lowest of the past 113 years (see http:\\/\\/www.ncdc.noaa.gov\\/oa\\/climate\\/research\\/monitoring.html#state). Throughout Illinois, counties were declared agricultural disaster areas and corn yields were predicted to be 30 percent less than the record year of 2004, which had the highest corn

Ping Zhang; Bruce T. Anderson; Ranga Myneni

2006-01-01

245

Compositional structure of the asteroid belt  

Microsoft Academic Search

A variety of observations, mainly albedos derived from 10 and 20 micron radiometry and eight-filter broadband spectrophotometry, were used to show that the asteroid belt is highly structured in composition. The bias-corrected distribution from 1.8 to 5.2 A.U. of the previously defined compositional types C,S,E,R, and M, plus type D and the newly described types F and P, are reported

J. Gradie; E. Tedesco

1982-01-01

246

The Size Distribution of Kuiper Belt Objects  

E-print Network

We describe analytical and numerical collisional evolution calculations for the size distribution of icy bodies in the Kuiper Belt. For a wide range of bulk properties, initial masses, and orbital parameters, our results yield power-law cumulative size distributions, N_C propto r^{-q}, with q_L = 3.5 for large bodies with radii of 10-100 km, and q_s = 2.5-3 for small bodies with radii lesss than 0.1-1 km. The transition between the two power laws occurs at a break radius of 1-30 km. The break radius is more sensitive to the initial mass in the Kuiper Belt and the amount of stirring by Neptune than the bulk properties of individual Kuiper Belt objects (KBOs). Comparisons with observations indicate that most models can explain the observed sky surface density of KBOs for red magnitudes, R = 22-27. For R 28, the model surface density is sensitive to the amount of stirring by Neptune, suggesting that the size distribution of icy planets in the outer solar system provides independent constraints on the formation of Neptune.

Scott J. Kenyon; Benjamin C. Bromley

2004-06-24

247

Meningococcal carriage in the African meningitis belt  

PubMed Central

Summary A meningococcal serogroup A polysaccharide/tetanus toxoid conjugate vaccine (PsA-TT) (MenAfriVac™) is being deployed in countries of the African meningitis belt. Experience with other polysaccharide/protein conjugate vaccines has shown that an important part of their success has been their ability to prevent the acquisition of pharyngeal carriage and hence to stop transmission and induce herd immunity. If PsA-TT is to achieve the goal of preventing epidemics, it must be able to prevent the acquisition of pharyngeal carriage as well as invasive meningococcal disease and whether PsA-TT can prevent pharyngeal carriage needs to be determined. To address this issue, a consortium (The African Meningococcal Carriage Consortium) (MenAfriCar) was established in 2009 to investigate the pattern of meningococcal carriage in countries of the African meningitis belt prior to and after the introduction of PsA-TT. This paper describes how the consortium was established, its objectives and the standardised field and laboratory methods that were used to achieve these objectives. The experience of the MenAfriCar Consortium will help in planning future studies on the epidemiology of meningococcal carriage in countries of the African meningitis belt and elsewhere. PMID:23682910

2014-01-01

248

Substyles of belting: phonatory and resonatory characteristics.  

PubMed

Belting has been described as speechlike, yell-like, or shouting voice production commonly used in contemporary commercial music genres and substantially differing from the esthetic of the Western classical voice tradition. This investigation attempts to describe phonation and resonance characteristics of different substyles of belting (heavy, brassy, ringy, nasal, and speechlike) and the classical style. A professional singer and voice teacher, skilled in these genres, served as the single subject. The recorded material was found representative according to a classification test performed by an expert panel. Subglottal pressure was measured as the oral pressure during the occlusion for the consonant /p/. The voice source and formant frequencies were analyzed by inverse filtering the audio signal. The subglottal pressure and measured flow glottogram parameters differed clearly between the styles heavy and classical assuming opposite extremes in most parameters. The formant frequencies, by contrast, showed fewer less systematic differences between the substyles but were clearly separated from the classical style with regard to the first formant. Thus, the differences between the belting substyles mainly concerned the voice source. PMID:21439776

Sundberg, Johan; Thalén, Margareta; Popeil, Lisa

2012-01-01

249

Radiation Belt Electron Loss mechanisms: New results  

NASA Astrophysics Data System (ADS)

The radiation belt electron precipitation (RBEP) into the topside ionosphere is a phenomenon which is known for several decades. However, the radiation belt source and loss mechanisms have not still well understood, including PBEP. Here we present the results of a systematic study of RBEP observations, as obtained from the satellite DEMETER and the series of POES satellites, in comparison with variation of seismic activity. We found that this type of RBEP bursts present special characteristics in the inner region of the inner radiation belt before large (M>7, or even M>5) earthquakes (EQs), as for instance characteristic (a) flux-time profiles, (b) energy spectrum, (c) electron flux temporal evolution, (d) spatial distributions and (e) they are associated with broad band VLF activity, some days before an EQ. The RBEP before EQs appears, not only as a burst, but as an increase of the normal electron background flux in large range of latitudes during magnetospheric storms. Recent results, in the presence of a magnetospheric storm and of strong seismic activity, seem to suggest an increase of the normal flux in the slot region as well. We found significant evidence that, among EQs-lightings-Earth based transmitters, seismic activity is that agent which probably make the main contribution to the RBEP at middle latitudes. Further research is in progress in order to further test the present results.

Anagnostopoulos, G.; Barlas, G.; Sidiropoulos, N.; Vassiliadis, V.

2013-09-01

250

A model for Jupiter's proton radiation belt  

NASA Technical Reports Server (NTRS)

A model for electron and proton energy and density in Jupiter's radiation belt is proposed. It is assumed that electrons diffuse inward from the solar wind. The Davis and Chang diffusion model, in which there is a very steep L-shell dependence in density and energy, is scaled outwards from the peak of the belts at about 1.5 to 2 Jupiter radii to the magnetopause as defined by the magnetic moment. The energetic electron density is calculated to be one billionth of the density in the solar wind, and that is assumed to be the trapping ratio of Jupiter's synchrotron belts. It is further assumed that the same figures apply to protons. The flux density at 80 MHz was measured by the Culgoora ring to be identical to that at 3000 MHz, implying a constant flux density of the synchrotron source of over 20 or 30 to 1 in frequency. It is suggested that the synchrotron spectrum is flat over more than an order of magnitude of frequency. Jupiter is an enormous synchrotron source and has a strong magnetic field, causing long diffusion times for electrons in the magnetosphere.

Warwick, J.

1972-01-01

251

Compositional variations in the Mesoarchean chromites of the Nuggihalli schist belt, Western Dharwar Craton (India): potential parental melts and implications for tectonic setting  

NASA Astrophysics Data System (ADS)

The chromite deposits in the Archean Nuggihalli schist belt are part of a layered ultramafic-mafic sequence within the Western Dharwar Craton of the Indian shield. The 3.1-Ga ultramafic-mafic units occur as sill-like intrusions within the volcano-sedimentary sequences of the Nuggihalli greenstone belt that are surrounded by the tonalite-trondhjemite-granodiorite (TTG) suite of rocks. The entire succession is exposed in the Tagdur mining district. The succession has been divided into the lower and the upper ultramafic units, separated by a middle gabbro unit. The ultramafic units comprise of deformed massive chromitite bodies that are hosted within chromite-bearing serpentinites. The chromitite bodies occur in the form of pods and elongated lenses (~60-500 m by ~15 m). Detailed electron microprobe studies reveal intense compositional variability of the chromite grains in silicate-rich chromitite (~50% modal chromite) and serpentinite (~2% modal chromite) throughout the entire ultramafic sequence. However, the primary composition of chromite is preserved in the massive chromitites (~60-75% modal chromite) from the Byrapur and the Bhaktarhalli mining district of the Nuggihalli schist belt. These are characterized by high Cr-ratios (Cr/(Cr + Al) = 0.78-0.86) and moderate Mg-ratios (Mg/(Mg + Fe2+) = 0.38-0.58). The compositional variability occurs due to sub-solidus re-equilibration in the accessory chromite in the serpentinite (Mg-ratio = 0.01-0.38; Cr-ratio = 0.02-0.99) and in silicate-rich chromitite (Mg-ratio = 0.06-0.48; Cr-ratio = 0.60-0.99). In the massive chromitites, the sub-solidus re-equilibration for chromite is less or absent. However, the re-equilibration is prominent in the co-existing interstitial and included olivine (Fo96-98) and pyroxene grains (Mg-numbers = 97-99). Compositional variability on the scale of a single chromite grain occurs in the form of zoning, and it is common in the accessory chromite grains in serpentinite and in the altered grains in chromitite. In the zoned grains, the composition of the core is modified and the rim is ferritchromit. In general, ferritchromit occurs as irregular patches along the grain boundaries and fractures of the zoned grains. In this case, ferritchromit formation is not very extensive. This indicates a secondary low temperature hydrothermal origin of ferritchromit during serpentinization. In some occurrences, the ferritchromit rim is very well developed, and only a small relict core appears to remain in the chromite grain. However, complete alteration of the chromite grains to ferritchromit without any remnant core is also present. The regular, well-developed and continuous occurrence of ferritchromit rims around the chromite grain boundaries, the complete alteration of the chromite grains and the modification of the core composition indicate the alteration in the Nuggihalli schist belt to be intense, pervasive and affected by later low-grade metamorphism. The primary composition of chromite has been used to compute the nature of the parental melt. The parental melt calculations indicate derivation from a high-Mg komatiitic basalt that is similar to the composition of the komatiitic rocks reported from the greenstone sequences of the Western Dharwar Craton. Tectonic discrimination diagrams using the primary composition of chromites indicate a supra-subduction zone setting (SSZ) for the Archean chromitites of Nuggihalli and derivation from a boninitic magma. The composition of the komatiitic basalts resembles those of boninites that occur in subduction zones and back-arc rift settings. Formation of the massive chromitites in Nuggihalli may be due to magma mixing process involving hydrous high-Mg magmas or may be related to intrusions of chromite crystal laden magma; however, there is little scope to test these models because the host rocks are highly altered, serpentinized and deformed. The present configurations of the chromitite bodies are related to the multistage deformation processes that are common in Archean greenstone belts.

Mukherjee, Ria; Mondal, Sisir K.; Rosing, Minik T.; Frei, Robert

2010-12-01

252

Radiation Belts of Antiparticles in Planetary Magnetospheres  

NASA Astrophysics Data System (ADS)

The Earth's radiation belts could be populated, besides with electrons and protons, also by antiparticles, such as positrons (Basilova et al., 1982) and antiprotons (pbar). Positrons are born in the decay of pions that are directly produced in nuclear reactions of trapped relativistic inner zone protons with the residual atmosphere at altitudes in the range of about 500 to 3000 km over the Earth's surface. Antiprotons are born by high energy (E > 6 GeV) cosmic rays in p+p - p+p+p+ pbar and in p+p - p+p+n+nbar reactions. The trapping and storage of these charged anti-particles in the magnetosphere result in radiation belts similar to the classical Van Allen belts of protons and electrons. We describe the mathematical techniques used for numerical simulation of the trapped positron and antiproton belt fluxes. The pion and antiproton yields were simulated on the basis of the Russian nuclear reaction computer code MSDM, a Multy Stage Dynamical Model, Monte Carlo code, (i.e., Dementyev and Sobolevsky, 1999). For estimates of positron flux there we have accounted for ionisation, bremsstrahlung, and synchrotron energy losses. The resulting numerical estimates show that the positron flux with energy >100 MeV trapped into the radiation belt at L=1.2 is of the order ~1000 m-2 s-1 sr-1, and that it is very sensitive to the shape of the trapped proton spectrum. This confined positron flux is found to be greater than that albedo, not trapped, mixed electron/positron flux of about 50 m-2 s-1 sr-1 produced by CR in the same region at the top of the geomagnetic field line at L=1.2. As we show in report, this albedo flux also consists mostly of positrons. The trapped antiproton fluxes produced by CR in the Earth's upper rarified atmosphere were calculated in the energy range from 10 MeV to several GeV. In the simulations we included a mathematic consideration of the radial diffusion process, both an inner and an outer antiproton source, losses of particles due to ionization process, annihilation, and nuclear interactions with the ambient matter. We have found that the Earth's antiproton belt possesses about 6-60 times larger antiproton fluxes compared to the galactic fluxes in interplanetary space during minimum and maximum solar activity at all energies in confinement zone. The radiation belt antiproton fluxes are spread into a wider L-shell range than its generation location around L=1.2. This is due to diffusion processes, and it demonstrates that radial diffusion as a relatively significant process for antimatter, even in the inner magnetosphere. Antimatter accumulated in the magnetospheres of solar system bodies may be of significance for space travel. It could be used as a propulsion for space missions to the outer planets and beyond. Antimatter has an energy density more than ten orders of magnitude higher than the best chemical propellants currently used in rocket systems. References: Basilova, R. N., A.A. Gusev, G.I. Pugacheva , Geom. and Aeronom. V. 22, p. 671-673, 1982.Chen, J., T. Dementyev, A.V., Sobolevsky, N.M. Radiation Measurements, 30, 553, 1999.

Pugacheva, G. I.; Gusev, A. A.; Jayanthi, U. B.; Martin, I. M.; Spjeldvik, W. N.

2007-05-01

253

Phyllosilicate absorption features in main-belt and outer-belt asteroid reflectance spectra.  

PubMed

Absorption features having depths up to 5% are identified in high-quality, high-resolution reflectance spectra of 16 dark asteroids in the main belt and in the Cybele and Hilda groups. Analogs among the CM2 carbonaceous chondrite meteorites exist for some of these asteroids, suggesting that these absorptions are due to iron oxides in phyllosilicates formed on the asteroidal surfaces by aqueous alteration processes. Spectra of ten additional asteroids, located beyond the outer edge of the main belt, show no discernible absorption features, suggesting that aqueous alteration did not always operate at these heliocentric distances. PMID:17748705

Vilas, F; Gaffey, M J

1989-11-10

254

Phyllosilicate absorption features in main-belt and outer-belt asteroid reflectance spectra  

NASA Technical Reports Server (NTRS)

Absorption features having depths up to 5 percent are identified in high-quality, high-resolution reflectance spectra of 16 dark asteroids in the main belt and in the Cybele and Hilda groups. Analogs among the CM2 carbonaceous chondrite meteorites exist for some of these asteroids, suggesting that these absorptions are due to iron oxides in phyllosilicates formed on the asteroidal surfaces by aqueous alteration processes. Spectra of ten additional asteroids, located beyond the outer edge of the main belt, show no discernible absorption features, suggesting that aqueous alteration did not always operate at these heliocentric distances.

Vilas, Faith; Gaffey, Michael J.

1989-01-01

255

Seat belt usage: A potential target for applied behavior analysis  

PubMed Central

Results of 1,579 observations of cars entering or exiting campus parking lots showed direct relationships between seat belt wearing and the intrusiveness of the engineering device designed to induce belt usage, and between device intrusiveness and system defeat. For example, all drivers with working interlocks or unlimited buzzer reminders were wearing a seat belt; but 62% of the systems with interlocks or unlimited buzzers had been defeated, and only 15.9% of the drivers in these cars were wearing a seat belt. The normative data indicated marked ineffectiveness of the negative reinforcement contingencies implied by current seat belt inducement systems; but suggested that unlimited buzzer systems would be the optimal system currently available if contingencies were developed to discourage the disconnection and circumvention of such systems. Positive reinforcement strategies are discussed that would be quite feasible for large-scale promotion of seat belt usage. PMID:16795638

Geller, E. Scott; Casali, John G.; Johnson, Richard P.

1980-01-01

256

Central Nevada overthrust belt: new and exciting frontier play  

SciTech Connect

Large, untested, thrust-related features along a newly described thrust belt in central Nevada could contain significant quantities of hydrocarbons. All producing fields in Nevada are found in upper plate fault blocks along this Early Cretaceous thrust belt. Hydrocarbons in these fields probably migrated from large thrust-related features that are yet to be tested. Exposures of thrust-belt indicators are found along this broad belt from the Keystone thrust of the Spring Mountains in southern Nevada to the Independent Mountains in northern Nevada. Thrust-related features in upper Paleozoic rocks are commonly associated with the Lower Cretaceous Newark Canyon Formation, which suggests an Early Cretaceous compressional event. In some areas, these features were draped by Oligocene volcanics and subsequently modified by Tertiary extension. Recognition of thrust-belt indicators, relationships of Mississippian source rocks and Devonian reservoir rocks, and preextention paleotopography is one of the keys in developing a profitable exploration model along this thrust belt.

Chamberlain, A.K.

1988-07-01

257

A population of comets in the main asteroid belt.  

PubMed

Comets are icy bodies that sublimate and become active when close to the Sun. They are believed to originate in two cold reservoirs beyond the orbit of Neptune: the Kuiper Belt (equilibrium temperatures of approximately 40 kelvin) and the Oort Cloud (approximately 10 kelvin). We present optical data showing the existence of a population of comets originating in a third reservoir: the main asteroid belt. The main-belt comets are unlike the Kuiper Belt and Oort Cloud comets in that they likely formed where they currently reside and may be collisionally activated. The existence of the main-belt comets lends new support to the idea that main-belt objects could be a major source of terrestrial water. PMID:16556801

Hsieh, Henry H; Jewitt, David

2006-04-28

258

Central Nevada overthrust belt: new and exciting frontier play  

Microsoft Academic Search

Large, untested, thrust-related features along a newly described thrust belt in central Nevada could contain significant quantities of hydrocarbons. All producing fields in Nevada are found in upper plate fault blocks along this Early Cretaceous thrust belt. Hydrocarbons in these fields probably migrated from large thrust-related features that are yet to be tested. Exposures of thrust-belt indicators are found along

1988-01-01

259

Diffusive Chaos in the Outer Asteroid Belt N. Murray and M. Holman  

E-print Network

Diffusive Chaos in the Outer Asteroid Belt N. Murray and M. Holman Canadian Institute asteroid belt similar to the Kirkwood gaps seen in the inner belt, in agreement with our recent numerical, such as the motion of small bodies in the Kuiper belt beyond Neptune or in the Asteroid belt between Mars and Jupiter

Murray, Norman

260

Passenger car size and driver seat belt use.  

PubMed Central

The National Highway Traffic Safety Administration (NHTSA) claims, on the basis of survey results, that seat belt use in small cars is twice as high as in large cars. The agency interprets this as being due in part to perceptions of higher risk by small car occupants. In fact, little is known about the factors motivating belt use, including whether risk perception is important. A reanalysis of the NHTSA data indicates that most of the differences in belt use by car size can be explained by higher use in imported cars, and by geographical differences in belt use in domestic cars. PMID:6837826

O'Neill, B; Williams, A F; Karpf, R S

1983-01-01

261

Magnetic refrigeration apparatus with belt of ferro or paramagnetic material  

DOEpatents

A magnetic refrigerator operating in the 12 to 77K range utilizes a belt which carries ferromagnetic or paramagnetic material and which is disposed in a loop which passes through the center of a solenoidal magnet to achieve cooling. The magnetic material carried by the belt, which can be blocks in frames of a linked belt, can be a mixture of substances with different Curie temperatures arranged such that the Curie temperatures progressively increase from one edge of the belt to the other. This magnetic refrigerator can be used to cool and liquefy hydrogen or other fluids.

Barclay, John A. (Madison, WI); Stewart, Walter F. (Marshall, WI); Henke, Michael D. (Los Alamos, NM); Kalash, Kenneth E. (Los Alamos, NM)

1987-01-01

262

Magnetic refrigeration apparatus with belt of ferro or paramagnetic material  

DOEpatents

A magnetic refrigerator operating in the 12 to 77 K range utilizes a belt which carries ferromagnetic or paramagnetic material and which is disposed in a loop which passes through the center of a solenoidal magnet to achieve cooling. The magnetic material carried by the belt, which can be blocks in frames of a linked belt, can be a mixture of substances with different Curie temperatures arranged such that the Curie temperatures progressively increase from one edge of the belt to the other. This magnetic refrigerator can be used to cool and liquefy hydrogen or other fluids.

Barclay, J.A.; Stewart, W.F.; Henke, M.D.; Kalash, K.E.

1986-04-03

263

The Overthrust Belt of Western North America  

SciTech Connect

The Overthrust Belt extends for 5000 mi (8000 km) from the Brooks Range in Alaska to the Sierra Madre Oriental in Mexico. It consists of northeastward vergent thrust and fold structures involving late Precambrian to early Tertiary sedimentary section. These sediments represent deposition off the western rift margin, formed in late Precambrian time, of the North American Precambrian craton. The northeastward thrusting continued throughout the Mesozoic as a response to the convergence of the East Pacific Plate with the North American Plate. This convergence resulted in subduction beneath the North American Plate except at the northwest end (the Brooks Range) where the result was obduction. Convergence ceased when the west edge of the East Pacific Plate reached the subduction zone. The sedimentary section involved in the Thrust Belt contains good Devonian to Cretaceous hydrocarbon source rocks, and Ordovician to traps related to the thrusting (simple thrust sheets, imbricate thrust sheets, folded thrust sheets, step anticlines, footwall cutoffs, footwall anticlines, etc.). Field methods involved in exploration for hydrocarbons include field geological mapping, remote sensing (aerial photography and Landsat imagery), various seismic refraction and seismic reflection techniques (including modern detailed three dimension surveys) and potential field methods such as gravity and magnetic surveying. Studies of the field data include paleontology, source rock and hydrocarbon migration studies, structural and stratigraphic analyses, and the processing of geophysical data. This work has succeeded in two major areas: the Western Canadian Rocky Mountain Foothills, a major gas province producing mainly from Paleozoic reservoirs; and the Wyoming-Idaho-Utah portion of the thrust belt, also a major gas producer from Paleozoic reservoirs and, in addition, a major oil producer from the Jurassic Nugget Sandstone.

Verrall, P.

1993-02-01

264

The Radiation Belt Storm Probes Mission: Advancing Our Understanding of the Earth's Radiation Belts  

NASA Technical Reports Server (NTRS)

We describe NASA's Radiation Belt Storm Probe (RBSP) mission, whose primary science objective is to understand, ideally to the point of predictability, the dynamics of relativistic electrons and penetrating ions in the Earth's radiation belts resulting from variable solar activity. The overarching scientific questions addressed include: 1. the physical processes that produce radiation belt enhancement events, 2. the dominant mechanisms for relativistic electron loss, and 3. how the ring current and other geomagnetic processes affect radiation belt behavior. The RBSP mission comprises two spacecraft which will be launched during Fall 2012 into low inclination lapping equatorial orbits. The orbit periods are about 9 hours, with perigee altitudes and apogee radial distances of 600 km and 5.8 RE respectively. During the two-year primary mission, the spacecraft orbits precess once around the Earth and lap each other twice in each local time quadrant. The spacecraft are each equipped with identical comprehensive instrumentation packages to measure, electrons, ions and wave electric and magnetic fields. We provide an overview of the RBSP mission, onboard instrumentation and science prospects and invite scientific collaboration.

Sibeck, David; Kanekal, Shrikanth; Kessel, Ramona; Fox, Nicola; Mauk, Barry

2012-01-01

265

An Evaluation Study of a CALL Application: With BELT or without BELT  

ERIC Educational Resources Information Center

The present study tried to evaluate the 6th grade students' attitudes towards the use of a CALL program which is called BELT Success used in English language learning course in a private school, the relationship to students' attitudes to their English language proficiency level, and finally teachers` experiences and opinions towards the use of…

Genc, Humeyra

2012-01-01

266

Great Ocean Conveyor Belt: Part I  

NSDL National Science Digital Library

The oceans are in constant flux. The movement of ocean water is readily observable in the rise and fall of the tides and the continual lapping of waves along the coastlines of continents and islands. Less obvious is the network of currents that constantly circulates ocean water from one side of the globe to another. This map illustrates the network of currents known as the great ocean conveyor belt, or the thermohaline conveyor, and shows which portions are travelled by warm and shallow, or cold and salty, currents. A background essay and discussion questions are included.

267

Water activities in the Kerala Khondalite Belt  

NASA Technical Reports Server (NTRS)

The author and colleagues presented their determinations of water activities in various granulite-facies rocks of the Kerala Khondalite Belt. Using mineral equilibria, thermodynamic data, and assumed geopressure-geotemperature conditions of 5.5 kbar and 750 C, they calculated uniformly low a(H2O) values of about 0.27 over a large geographic region. They suggested that these conditions were produced by the presence of abundant CO2-rich fluids, derived either from deeper levels or from metamorphic reactions involving graphite.

Chacko, Thomas; Kumar, G. R. Ravindra; Peterson, J. W.

1988-01-01

268

Aircraft radial-belted tire evaluation  

NASA Technical Reports Server (NTRS)

An overview is given of the ongoing joint NASA/FAA/Industry Surface Traction And Radial Tire (START) Program being conducted at NASA Langley's Aircraft Landing Dynamics Facility (ALDF). The START Program involves tests using three different tire sizes to evaluate tire rolling resistance, braking, and cornering performance throughout the aircraft ground operational speed range for both dry and wet runway surfaces. Preliminary results from recent 40 x 14 size bias-ply, radial-belted, and H-type aircraft tire tests are discussed. The paper concludes with a summary of the current program status and planned ALDF test schedule.

Yager, Thomas J.; Stubbs, Sandy M.; Davis, Pamela A.

1990-01-01

269

Dust bands in the asteroid belt  

NASA Technical Reports Server (NTRS)

This paper describes the original IRAS observations leading to the discovery of the three dust bands in the asteroid belt and the analysis of data. Special attention is given to an analytical model of the dust band torus and to theories concerning the origin of the dust bands, with special attention given to the collisional equilibrium (asteroid family), the nonequilibrium (random collision), and the comet hypotheses of dust-band origin. It is noted that neither the equilibrium nor nonequilibrium models, as currently formulated, present a complete picture of the IRAS dust-band observations.

Sykes, Mark V.; Greenberg, Richard; Dermott, Stanley F.; Nicholson, Philip D.; Burns, Joseph A.

1989-01-01

270

23 CFR Appendix D to Part 1240 - Determination of National Average Seat Belt Use Rate  

Code of Federal Regulations, 2011 CFR

... Determination of National Average Seat Belt Use Rate D Appendix D to Part 1240 Highways NATIONAL HIGHWAY TRAFFIC SAFETY...BELTS-ALLOCATIONS BASED ON SEAT BELT USE RATES Pt. 1240, App. D Appendix D to Part 1240—Determination of National...

2011-04-01

271

23 CFR Appendix D to Part 1240 - Determination of National Average Seat Belt Use Rate  

... Determination of National Average Seat Belt Use Rate D Appendix D to Part 1240 Highways NATIONAL HIGHWAY TRAFFIC SAFETY...BELTS-ALLOCATIONS BASED ON SEAT BELT USE RATES Pt. 1240, App. D Appendix D to Part 1240—Determination of National...

2014-04-01

272

23 CFR Appendix D to Part 1240 - Determination of National Average Seat Belt Use Rate  

Code of Federal Regulations, 2012 CFR

... Determination of National Average Seat Belt Use Rate D Appendix D to Part 1240 Highways NATIONAL HIGHWAY TRAFFIC SAFETY...BELTS-ALLOCATIONS BASED ON SEAT BELT USE RATES Pt. 1240, App. D Appendix D to Part 1240—Determination of National...

2012-04-01

273

Late Archean greenstone tectonics: Evidence for thermal and thrust-loading lithospheric subsidence from stratigraphic sections in the Slave Province, Canada  

NASA Technical Reports Server (NTRS)

How late Archean tectonics could be seen to have operated in the Slave Province is illustrated. Lithospheric thinning and stretching, with the formation of rifted margins (to continental or island arc fragments), and lithospheric flexural loading of the kind familiar in arcs and mountain belts could be discerned.

Kidd, W. S. F.; Kusky, T. M.; Bradley, D. C.

1988-01-01

274

LANL*: Radiation belt drift shell modeling  

NASA Astrophysics Data System (ADS)

LANL* calculates the magnetic drift invariant L*, used for modeling radiation belt dynamics and other space weather applications, six orders of magnitude (~ one million times) faster than convectional approaches that require global numerical field lines tracing and integration. It is based on a modern machine learning technique (feed-forward artificial neural network) by supervising a large data pool obtained from the IRBEM library, which is the traditional source for numerically calculating the L* values. The pool consists of about 100,000 samples randomly distributed within the magnetosphere (r: [1.03, 11.5] Re) and within a whole solar cycle from 1/1/1994 to 1/1/2005. There are seven LANL* models, each corresponding to its underlying magnetic field configuration that is used to create the data sample pool. This model has applications to real-time radiation belt forecasting, analysis of data sets involving tens of satellite-years of observations, and other problems in space weather.

Yu, Yiqun; Koller, Josef

2014-09-01

275

Geodynamic processes and deformation in orogenic belts  

NASA Astrophysics Data System (ADS)

The development of geosynclines and orogenic belts is related to lithosphere convergence. Initial sediment accumulation implying subsidence, and volcanic activity implying extension and rise of geotherms, are in most cases followed by folding and thrusting suggesting compression and by uplift. In terms of recent analogs, sediment accumulation and crustal extension are characteristic of back-arc spreading; subsequent compression would indicate continent—continent collision; and rise of geotherms most likely requires localized thermal flow (convection) in the asthenosphere. These events are here shown to agree with Andrews and Sleep's (1974) numerical model of asthenosphere flow at converging plate margins. Orthogeosynclinal subsidence appears to be a consequence of subcrustal ablation and lithosphere extension and thinning in active marginal basins. Arc and Andean type magmatism mark the reappearance of ablated and transported, relatively low-density subcrustal material. Collision slows and eventually stops the local convection cell, resulting in local heat accumulation and hence high- T, low- P metamorphism and granitization while marginal basin (orthogeosynclinal) deposits are being compressed into Alpine style orogenic structures. Moreover, closing of the marginal basin leads to subsidiary subduction, which in turn may be responsible for some Alpine style structures. Oceanic trench deposits may become incorporated in orogenic zones, as high- P, low- T metamorphic belts (thalassogeosynclines). Dynamic uplift is a fundamental characteristic of orogeny. Most rising and sinking in orogenic zones can be linked to those asthenosphere processes which are a consequence of Andrews-Sleep convection.

Dennis, John G.; Jacoby, Wolfgang R.

1980-03-01

276

CO depletion in the Gould Belt clouds  

NASA Astrophysics Data System (ADS)

We present a statistical comparison of CO depletion in a set of local molecular clouds within the Gould Belt using Sub-millimetre Common User Bolometer Array (SCUBA) and Heterodyne Array Receiver Programme (HARP) data. This is the most wide-ranging study of depletion thus far within the Gould Belt. We estimate CO column densities assuming local thermodynamic equilibrium and, for a selection of sources, using the radiative transfer code RADEX in order to compare the two column density estimation methods. High levels of depletion are seen in the centres of several dust cores in all the clouds. We find that in the gas surrounding protostars, levels of depletion are somewhat lower than for starless cores with the exception of a few highly depleted protostellar cores in Serpens and NGC 2024. There is a tentative correlation between core mass and core depletion, particularly in Taurus and Serpens. Taurus has, on average, the highest levels of depletion. Ophiuchus has low average levels of depletion which could perhaps be related to the anomalous dust grain size distribution observed in this cloud. High levels of depletion are often seen around the edges of regions of optical emission (Orion) or in more evolved or less dynamic regions such as the bowl of L1495 in Taurus and the north-western region of Serpens.

Christie, H.; Viti, S.; Yates, J.; Hatchell, J.; Fuller, G. A.; Duarte-Cabral, A.; Sadavoy, S.; Buckle, J. V.; Graves, S.; Roberts, J.; Nutter, D.; Davis, C.; White, G. J.; Hogerheijde, M.; Ward-Thompson, D.; Butner, H.; Richer, J.; Di Francesco, J.

2012-05-01

277

Fading of Jupiter's South Equatorial Belt  

NASA Technical Reports Server (NTRS)

One of Jupiter's most dominant features, the South Equatorial Belt, has historically gone through a "fading" cycle. The usual dark, brownish clouds turn white, and after a period of time, the region returns to its normal color. Understanding this phenomenon, the latest occurring in 2010, will increase our knowledge of planetary atmospheres. Using the near infrared camera, NSFCAM2, at NASA's Infrared Telescope Facility in Hawaii, images were taken of Jupiter accompanied by data describing the circumstances of each observation. These images are then processed and reduced through an IDL program. By scanning the central meridian of the planet, graphs were produced plotting the average values across the central meridian, which are used to find variations in the region of interest. Calculations using Albert4, a FORTRAN program that calculates the upwelling reflected sunlight from a designated cloud model, can be used to determine the effects of a model atmosphere due to various absorption, scattering, and emission processes. Spectra that were produced show ammonia bands in the South Equatorial Belt. So far, we can deduce from this information that an upwelling of ammonia particles caused a cloud layer to cover up the region. Further investigations using Albert4 and other models will help us to constrain better the chemical make up of the cloud and its location in the atmosphere.

Sola, Michael A.; Orton, Glenn; Baines, Kevin; Yanamandra-Fisher, Padma

2011-01-01

278

Exploration for uranium deposits, Grants mineral belt  

SciTech Connect

Uranium ore deposits in the Grants mineral belt, New Mexico, occur in fluvial sandstones in the Morrison Formation (Jurassic). Uranium mineralization is concentrated by a dark-gray to black substance that has been identified as humate, which is derived from decaying vegetation. Black ore is truncated by overlying sandstone in at least three ore deposits, documenting an early age for mineralization. Ore deposits in the Grants mineral belt vary greatly in size and shape, tend to occur in clusters, and often present difficult drill targets. Current exploration is largely a matter of drilling in stages to distinguish favorable from unfavorable ground on a wide spacing, to seek mineralization in favorable ground, and to conduct close-spaced drilling in mineralized areas. Criteria for favorability differ among exploration groups but generally include 1) presence of a host sandstone, 2) anomalous mineralization, 3) color of the host rock, 4) presence of carbonaceous matter, and 5) position of the area relative to mineralized trends. A description of the drilling sequence, from ore discovery to the development of a mine at the Johnny M deposit (in the east part of the Ambrosia Lake district), exemplifies the problem of predicting where orebodies may occur. A study of the drill data at the Johnny M indicates the uranium ore is not related to specific geologic features other than humate, which is commonly associated with coalified plant fragments in mudstone-rich parts of the host sandstone.

Fitch, D.C.

1980-01-01

279

WATER ICE IN THE KUIPER BELT  

SciTech Connect

We examine a large collection of low-resolution near-infrared spectra of Kuiper Belt objects (KBOs) and centaurs in an attempt to understand the presence of water ice in the Kuiper Belt. We find that water ice on the surface of these objects occurs in three separate manners: (1) Haumea family members uniquely show surfaces of nearly pure water ice, presumably a consequence of the fragmentation of the icy mantle of a larger differentiated proto-Haumea; (2) large objects with absolute magnitudes of H < 3 (and a limited number to H = 4.5) have surface coverings of water ice-perhaps mixed with ammonia-that appears to be related to possibly ancient cryovolcanism on these large objects; and (3) smaller KBOs and centaurs which are neither Haumea family members nor cold-classical KBOs appear to divide into two families (which we refer to as 'neutral' and 'red'), each of which is a mixture of a common nearly neutral component and either a slightly red or very red component that also includes water ice. A model suggesting that the difference between neutral and red objects due to formation in an early compact solar system either inside or outside, respectively, of the {approx}20 AU methanol evaporation line is supported by the observation that methanol is only detected on the reddest objects, which are those which would be expected to have the most of the methanol containing mixture.

Brown, M. E.; Fraser, W. C. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Schaller, E. L., E-mail: mbrown@caltech.edu [NASA Dryden Aircraft Operations Facility, Palmdale, CA 93550 (United States)

2012-06-15

280

Seat belt utilisation and awareness in UAE.  

PubMed

Seat belts (SBs) are effective devices for reducing injury risk due to traffic accidents. Seat belt wearing was made compulsory in the United Arab Emirates (UAE) in January 1999 for drivers and front seat passengers (FSPs). No comprehensive study has ever assessed SB wearing rates across the country. Also, little is known on drivers' awareness of the importance of wearing seatbelts and how human factors affect wearing habits. This study aims to determine SB wearing rates for drivers and FSPs in UAE through an observational field study. It also aims to investigate perceptions and behaviour of drivers on this issue as well as human factors that affect wearing rate through a randomly distributed questionnaire. The results of the field study show that the overall SB wearing rate across the country was 61% for drivers and 43.4% for FSPs and that there were significant differences between the seven emirates that constitute the country. The questionnaire results show that age, education level, gender, marital status and nationality of drivers affect wearing habits and perceptions. Future implications in terms of improving traffic safety awareness are discussed. PMID:23163241

Bendak, S; Al-Saleh, K

2013-01-01

281

How diverse is the asteroid belt?  

NASA Technical Reports Server (NTRS)

For approximately twenty years, many different asteroid taxonomies, which used many different observational data sets, have been developed to try to group asteroids into classes that contain members with similar spectral characteristics. However, to understand the structure of the asteroid belt, the resulting classes are only useful if they are grouping together asteroids with somewhat similar mineralogies and thermal histories. Until recently, these taxonomies have focused on spectral reflectance data from 0.3 to 1.1 microns and visual albedo. But in the last five years, observational data sets (e.g., 0.8 to 2.5 microns spectra, CCD spectra, 3 microns spectra, and radar albedos) for a small number of asteroids were compiled that can give a better mineralogical interpretation, but whose use in asteroid taxonomy was relatively limited. Analyses of these 'supplementary' data sets show that most asteroid classes contain members with different compositions and/or thermal histories. To understand the diversity of the asteroid belt, the number of objects with these observations must be expanded and used in the next generation of taxonomies.

Burbine, Thomas H.; Bell, Jeffrey F.

1993-01-01

282

Dust bands in the asteroid belt  

SciTech Connect

The Infrared Astronomical Satellite (IRAS) discovered three bands of dust: one above, below, and approximately in the plane of the ecliptic. These bands are located in the asteroid belt and are believed to arise from collisional activity. Debris from an asteroid collision, over time, fills a torus having peaks in particle number density near its inner and outer corners, corresponding to the locus of perihelia and aphelia, respectively. As a consequence of this geometry, such a swarm should produce two pairs of bands that straddle the ecliptic - a perihelion band pair and an aphelion band pair (which generally overlap along the line of sight from earth). Indeed, processing of the IRAS data now resolves the band structure into at least three such band pairs, with indications of several more pairs distributed over a large range of ecliptic latitudes. Some of these bands appear to be associated with major Hirayama asteroid families, while others are not. Possible origins of the observed dust bands include: (1) the gradual comminution of the asteroid belts as a whole, in which the local dust population is maximum where the concentration of asteroids is greatest (e.g. families); (2) one or a few large random asteroid collisions enhancing the local population of small debris, which in turn is comminuted into dust; and (3) the disintegration of one or more large comets. Dust bands are not necessarily constant features of the solar system.

Sykes, M.; Greenberg, R.; Dermott, S.; Nicholson, P.; Burns, J.

1989-09-08

283

Increasing Safety Belt Use by High Risk Drivers.  

National Technical Information Service (NTIS)

The objectives of the study were to: (1) identify groups of non-belt users who are most likely to become involved in highway crashes; and (2) develop and test communication programs designed to increase safety belt use by one or more of these groups. The ...

R. D. Blomberg, E. W. Bishop, J. M. Edwards

1991-01-01

284

Return of the Sacred Wampum Belts of the Iroquois.  

ERIC Educational Resources Information Center

Relates history and process by which 12 historic wampum belts were turned over to representatives of Onondaga Nation (New York), one of six Indian tribal communities of Iroquois Confederacy. Describes history of belts from pre-Columbian times to modern times. Compliments both the New York State Board of Regent and leaders of the Onondaga Nation…

Sullivan, Martin

1992-01-01

285

Gears and Belt Drives for Non-Uniform Transmission  

E-print Network

Gears and Belt Drives for Non-Uniform Transmission Hellmuth Stachel Abstract Ordinarily, gears and belt drives are used for uniform transmission of rotations between parallel axes. Here we focus on the nonuniform case, i.e., with non-constant transmission ratio. We treat the geometry of tooth profiles

Stachel, Hellmuth

286

Seat belt use among drinking drivers in Minnesota.  

PubMed Central

OBJECTIVES. Among the reasons cited for recent declines in alcohol-related traffic fatalities is the enactment of seat belt use laws by most states. It is suspected that drinking drivers are less likely to comply with such laws, although evidence on the relationship between belt use and drinking by drivers is sparse and conflicting. The purpose of this study was to examine the relationship of drinking to driver seat belt use. METHODS. Observational, self-report, and chemical breath test data were collected on nighttime drivers in 16 Minnesota communities during September, 1990. RESULTS. Drivers with an illegal blood alcohol concentration (> or = 100 mg/dL) were substantially less likely to be wearing a seat belt (odds ratio [OR] = 2.17). Belt use was also more common among females (OR = 2.02) and before midnight (OR = 1.47). Males who had been drinking were less likely to be belted. Belt use was related to drinking before, but not after, midnight. Belt use was not related to drinking status among college graduates, but it was strongly related to drinking status among those with less education. CONCLUSIONS. The present findings provide further argument for rapid implementation of passive countermeasures (airbags) and for development of creative, carefully focused interventions to target high-risk populations. PMID:7977909

Foss, R D; Beirness, D J; Sprattler, K

1994-01-01

287

30 CFR 57.4503 - Conveyor belt slippage.  

Code of Federal Regulations, 2010 CFR

...capable of automatically stopping the drive pulley. (b) Underground belt conveyors...capable of automatically stopping the drive pulley if slippage could cause ignition of the...person shall attend the belt at the drive pulley when it is necessary to operate the...

2010-07-01

288

The South Equatorial Belt of Jupiter, I: Its Life Cycle  

Microsoft Academic Search

The South Equatorial Belt (SEB) of Jupiter, located between latitudes ?10°S and ?20°S, represents the archetype of a cyclically changing band between the belt and zone stages. A new analysis of the historical records has been performed, using various published observations and additional data in visual wavelengths, which permit characterization of cloud morphology patterns, the zonal and meridional motions, the

A. Sanchez-Lavega; J. M. Gomez

1996-01-01

289

CORN BELT PLAIN RIVER AND STREAMS PROJECT - 3 BIOCRITERIA PRODUCTS  

EPA Science Inventory

This effort resulted in eight products, as follows: 1) Development of Index of Biotic Integrity Expectations for the Ecoregions of Indiana I. Central Corn Belt Plain; 2) Ibid. II. Huron-Erie Lake Plain; 3) Ibid III. Northern Indiana Till Plain; 4) Ibid .IV.Eastern Corn Belt Plain...

290

An Evaluation of the Seat Belt Education Campaign.  

ERIC Educational Resources Information Center

A seat belt education campaign conducted in Canada to dispel myths surrounding seat belts and promote a better understanding of their functions was evaluated. Two telephone surveys, each comprised of 4,000 respondents, were conducted. The first was done immediately before the campaign and the second immediately succeeding the campaign. Also, a…

Rochon, James

291

VIR, the imaging spectrometer for the asteroid belt exploration  

Microsoft Academic Search

We describe the journey Dawn mission to the asteroid belt. The objective of Dawn is to explore backward in time via its observations of the primitive bodies, Vesta and Ceres. Dawn is the ninth mission in NASA's Discovery Program and is the first interplanetary mission that will orbit two solar system bodies: the massive main belt asteroid Vesta and the

M. C. De Sanctis; A. Coradini; E. Ammannito; M. T. Capria; S. Fonte

2009-01-01

292

The Origin and Evolution of the Asteroid Main Belt  

Microsoft Academic Search

Using a fully autonomous spacecraft - Bering - we propose to detect and study sub-km asteroids from an orbit within the asteroid Main Belt. The main purpose of the proposed Bering mission is to detect a statistically significant sample of an expected population of approximately 10^(10) main belt asteroids in the size range 1 m to 1 km. These asteroids

Philip R. Bidstrup; Henning Haack; Anja C. Andersen; Rene Michelsen; John Leif Jorgensen

2005-01-01

293

Survey of current situation in radiation belt modeling.  

PubMed

The study of Earth's radiation belts is one of the oldest subjects in space physics. Despite the tremendous progress made in the last four decades, we still lack a complete understanding of the radiation belts in terms of their configurations, dynamics, and detailed physical accounts of their sources and sinks. The static nature of early empirical trapped radiation models, for examples, the NASA AP-8 and AE-8 models, renders those models inappropriate for predicting short-term radiation belt behaviors associated with geomagnetic storms and substorms. Due to incomplete data coverage, these models are also inaccurate at low altitudes (e.g., <1000 km) where many robotic and human space flights occur. The availability of radiation data from modern space missions and advancement in physical modeling and data management techniques have now allowed the development of new empirical and physical radiation belt models. In this paper, we will review the status of modern radiation belt modeling. PMID:15881789

Fung, Shing F

2004-01-01

294

Wampum Belts with Initials and/or Dates as Design Elements: A Preliminary Review of One Subcategory of Political Belts  

ERIC Educational Resources Information Center

Data on seventeen relatively well-documented examples as a preliminary review to an ongoing study of all that is known about belts that are a subcategory of the secular-political category is discussed. Evidence indicates that Wampum belts with initials and/or dates as design elements can clearly be demonstrated as but one subcategory of…

Becker, Marshall Joseph; Lainey, Jonathan

2004-01-01

295

Promote safe driving practices Seat belt use: Seat belts are the single most effective means of reducing deaths and  

E-print Network

in their life. Alcohol, certain prescription drugs, over-the-counter medications, and illegal drugs can allPromote safe driving practices Seat belt use: Seat belts are the single most effective means for work. Refrain from using cell phone to minimize distraction. Alcohol and drug impaired driving

Knowles, David William

296

Studying the Saturn Inner Radiation Belt  

NASA Astrophysics Data System (ADS)

In 2004 the MIMI/INCA detector onboard the Cassini spacecraft measured the significant flux of the energetic neutral atoms (ENA) coming from the area between the D-ring and the Saturn's atmosphere, what brought up the idea of the possible existence of the innermost radiation belt in this narrow gap. In the present study we estimate the possible sources for this radiation belt, assuming the two main processes: the double charge exchange of the ENAs, coming from the middle magnetosphere, what can bring the keV ions to the region of our interest, and the interaction of the Galactic Cosmic Rays (GCR) with the Saturn's atmosphere and rings, which due to CRAND process can produce the keV-MeV ions or electrons in the region. Both of these possible sources are possible to evaluate using the charged particle tracer. In our group we developed such charged particle tracer, which works in all different modes (Newton-Lorentz full equation of motion, guiding center or bounce averaged approximations), and allows using the different magnetic field models (from simple dipole magnetic field till complex realistic magnetic field model like Khurana model of Saturn's magnetosphere) for both forward and backward tracing simulations. This charged particle tracer was validated using the comparison of the simulation results and observations during several flybys of Cassini by icy moons of Saturn. Using the particle tracer we can calculate the access of GCRs to the atmosphere and rings of the planet and evaluate the filtering of the GCR spectrum that hits the atmosphere from the direction of the Saturn's main rings. Also we can investigate different non-dipolar effects which possible can change the Stroemer cutoff rigidities of GCRs, especially for the high-latitude atmosphere, which maps magnetically in the outer magnetosphere. We can also estimate the production of secondaries as well (and also from the multiple impacts of these secondaries on the rings or atmosphere) and evaluate the energy spectrum of neutrons, the decay of which leads to the production of final CRAND elements in the inner Saturnian radiation belts. Using this complex simulation we are going to predict the fluxes of energetic ions and electrons, which particle detector MIMI/LEMMS onboard the Cassini can measure during the so-called "proximal" orbits in 2017, when the Cassini spacecraft will pass directly through this diverse and enigmatic region extremely close to the planet.

Kotova, A.; Roussos, E.; Krupp, N.; Dandouras, I.

2013-09-01

297

The Kuiper Belt and Olbers Paradox  

E-print Network

We investigate the constraints that Olbers Paradox, applied to the Zodiacal Background as measured from space, sets on outer solar system objects. If extended to very faint limits, R = 40--50 mag, the steep optical luminosity function (LF) of Kuiper Belt objects (KBOs) at R less than 26 mag implies an infinitely bright night sky. Small KBOs with radii of 1 mm to 1 km must have a size distribution n(r) proportional to r^{-a}, with a = 3.5 or smaller to satisfy the known limits on the sky-surface brightness at optical and far-infrared wavelengths. Improved limits on the measured KBO surface brightness can yield direct estimates of the albedo, temperature, and size distribution for small KBOs in the outer solar system.

Scott J. Kenyon; Rogier A. Windhorst

2000-09-11

298

The Foundations of Radiation Belt Research  

NASA Astrophysics Data System (ADS)

The United States undertook the launching of an artificial Earth satellite as part of its contribution to the International Geophysical Year. The Vanguard program was established to meet that commitment, and it developed a launch vehicle, ground station network, and suite of scientific payloads, including the cosmic ray experiment proposed by James A. Van Allen. Although Vanguard eventually exceeded all of its pre-stated goals, the preemptive launches of Sputniks I and II by the Soviets in October and November 1957 spurred the U.S. into a frenzy of activity, resulting in the launches of Explorers I and III in January and March of 1958. The data from those two satellites quickly revealed the lower boundary of an unexpected region of high intensity radiation trapped in the Earth's magnetic field. The original announcement in May 1958 stated that the radiation was probably composed of either protons or electrons, and that, if electrons, it was probably bremsstrahlung formed in the satellite shell. Immediately following that announcement, approval was received for what became Explorer IV, whose announced purpose was to follow up on the new discovery. Another reason for the satellite, unmentioned at the time, was its inclusion as a component of the highly classified Argos program, a covert military program to test whether the detonation of nuclear devices at high altitude would inject measurable numbers of charged particles into durable trajectories in the Earth's magnetic field. Our team at Iowa produced the satellites under the oversight of, and with assistance by, the Army Ballistic Missile Agency in Huntsville, and with the contributions of key hardware from several other government laboratories. The project was completed in the unbelievably short period of seventy-seven days from approval to launch. Launched into a higher-inclination orbit than the earlier Explorers, Explorer IV confirmed the discovery and greatly expanded our understanding of the natural phenomenon. It also provided the first hint that there were two distinct radiation belts, although that conclusion was not reached until later. Although that new information was quickly announced, the results of the high altitude nuclear detonations were kept secret until well into 1959. They clearly revealed the charged particle shells created by the Argos nuclear detonations. The next major step in mapping and understanding the high-intensity radiation involved the launch of deep space probes Pioneers III and IV in December 1958 and March 1959. Although both launches fell short in their primary objective, to reach the moon, they traveled far enough from the Earth to fully meet the needs of the scientific experiment. They very clearly showed the two-radiation belt structure, and mapped its extent. They also showed the probable effect of a magnetic storm on 25 February, thus indicating the direct influence of solar activity on the outer belt. By the end of 1959, the existence of the Van Allen Radiation Belts and their general structure were solidly established, early information about the composition of the radiation was appearing in print, and energetic work was under way to understand the physics of the processes involved.

Ludwig, G. H.

2008-12-01

299

Ambient tremors in a collisional orogenic belt  

NASA Astrophysics Data System (ADS)

tectonic tremors have been regarded as an observation tied to interconnected fluids at depth, which have been well documented in worldwide subduction zones and transform faults but not in a collisional mountain belt. In this study we explore the general features of collisional tremors in Taiwan and discuss the possible generation mechanism. In the 4 year data, we find 231 ambient tremor episodes with durations ranging from 5 to 30 min. In addition to a coseismic slip-induced stress change from nearby major earthquake, increased tremor rate is also highly correlated with the active, normal faulting earthquake swarms at the shallower depth. Both the tremor and earthquake swarm activities are confined in a small, area where the high attenuation, high thermal anomaly, the boundary between high and low resistivity, and localized veins on the surfaces distributed, suggesting the involvement of fluids from metamorphic dehydration within the orogen.

Chuang, Lindsay Yuling; Chen, Kate Huihsuan; Wech, Aaron; Byrne, Timothy; Peng, Wei

2014-03-01

300

Artificial perturbations of the radiation belts  

NASA Technical Reports Server (NTRS)

A review is given of the properties of the radiation belts which have been produced by high-altitude nuclear detonations. The low-yield, Argus devices, 1, 2, and 3, and the Soviet test of 1 November 1962 injected intense electron fluxes in narrow L-shell intervals, with peaks at L = 1.72, 2.11, 2.17, and 1.77, respectively. The energy spectra of the electrons were indistinguishable from the equilibrium fission beta spectrum, and the fluxes initially decayed at rates approximately proportional to (time) sup -1.1. The high-yield devices, Starfish and the Soviet tests of 22 October and 28 October 1962, injected electrons over wide ranges. At L values near the lower boundary, the electron spectra appeared to be softer at the higher L values.

Cladis, J. B.

1972-01-01

301

Space cowboys odyssey: beyond the Gould Belt  

E-print Network

We present our new advanced model for population synthesis of close-by cooling NSs. Detailed treatment of the initial spatial distribution of NS progenitors and a detailed ISM structure up to 3 kpc give us an opportunity to discuss the strategy to look for new isolated cooling NSs. Our main results in this respect are the following: new candidates are expected to be identified behind the Gould Belt, in directions to rich OB associations, in particular in the Cygnus-Cepheus region; new candidates, on average, are expected to be hotter than the known population of cooling NS. Besides the usual approach (looking for soft X-ray sources), the search in 'empty' $\\gamma$-ray error boxes or among run-away OB stars may yield new X-ray thermally emitting NS candidates.

S. B. Popov; B. Posselt; F. Haberl; J. Trümper; R. Turolla; R. Neuhäuser

2007-10-08

302

What Drives the Global Conveyer Belt?  

NSDL National Science Digital Library

In this laboratory activity, students observe what happens when a fluid of one density is placed in a fluid of a different density. The fluids are salt water and fresh water, cold water and warm water. They generalize their results to describe what occurs in the world's oceans to drive the global conveyor belt pattern of ocean currents. There is an option to conduct an investigation taking quantitative measurements, which requires an immersible thermometer and a heat source. Assessment suggestions are included. The investigation is found in the teacher's guide accompanying the textbook, Climate Change, part of Global System Science (GSS), an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.

303

A Comprehensive Simulation Method for Examining Radiation Belt Dynamics  

NASA Astrophysics Data System (ADS)

The particles comprising the Van Allen radiation belts are affected by a variety of electromagnetic and electrostatic waves present in the magnetosphere. For example, the Van Allen Probes mission has recently uncovered evidence for heating in the radiation belts as a result of local kHz wave-particle interactions, violating the cyclotron invariant. Similarly, global variations at mHz frequencies commensurate with the particle drift frequency can lead to effective transport, heating, and loss within the radiation belts as a result of changes to the third adiabatic invariant. The wide variety of waves occurring over this disparate frequency range presents a fundamental challenge in constructing dynamic models of the radiation belts. In this effort we present results from a new method for tracking the global dynamics of the radiation belts. Here we examine a well-observed flux dropout and subsequent acceleration event occurring on 20 September 2007. We use 3d magnetohydrodynamic (MHD) simulations of the solar wind/magnetospheric interaction to track particles in a bounce-averaged formalism, combined with stochastic differential equation (SDE) simulations of local wave-particle interactions, to provide a comprehensive model of the radiation belts encompassing both large-scale transport and local heating and loss within the radiation belts.

Elkington, S. R.; Chan, A. A.; Zheng, L.

2013-12-01

304

Stride length asymmetry in split-belt locomotion.  

PubMed

The number of studies utilizing a split-belt treadmill is rapidly increasing in recent years. This has led to some confusion regarding the definitions of reported gait parameters. The purpose of this paper is to clearly present the definitions of the gait parameters that are commonly used in split-belt treadmill studies. We argue that the modified version of stride length for split-belt gait, which is different from the standard definition of stride length and actually is a measure of limb excursion, should be referred to as 'limb excursion' in future studies. Furthermore, the symmetry of stride length and stride time is specifically addressed. PMID:24041467

Hoogkamer, Wouter; Bruijn, Sjoerd M; Duysens, Jacques

2014-01-01

305

Contamination of the asteroid belt by primordial trans-Neptunian objects  

E-print Network

LETTERS Contamination of the asteroid belt by primordial trans-Neptunian objects Harold F. Levison1 Tsiganis5 The main asteroid belt, which inhabits a relatively narrow annulus 2.1­3.3 AU from the Sun- Neptunian objects into the outer belt. This result implies that the observed diversity of the asteroid belt

Morbidelli, Alessandro

306

Effect of one-way clutch on the nonlinear vibration of belt-drive systems with a continuous belt model  

NASA Astrophysics Data System (ADS)

This study focuses on the nonlinear steady-state response of a belt-drive system with a one-way clutch. A dynamic model is established to describe the rotations of the driving pulley, the driven pulley, and the accessory shaft. Moreover, the model considers the transverse vibration of the translating belt spans for the first time in belt-drive systems coupled with a one-way clutch. The excitation of the belt-drive system is derived from periodic fluctuation of the driving pulley. In automotive systems, this kind of fluctuation is induced by the engine firing harmonic pulsations. The derived coupled discrete-continuous nonlinear equations consist of integro-partial-differential equations and piece-wise ordinary differential equations. Using the Galerkin truncation, a set of nonlinear ordinary differential equations is obtained from the integro-partial-differential equations. Applying the Runge-Kutta time discretization, the time histories of the dynamic response are numerically solved for the driven pulley and the accessory shaft and the translating belt spans. The resonance areas of the coupled belt-drive system are determined using the frequency sweep. The effects of the one-way clutch on the belt-drive system are studied by comparing the frequency-response curves of the translating belt with and without one-way clutch device. Furthermore, the results of 2-term and 4-term Galerkin truncation are compared to determine the numerical convergence. Moreover, parametric studies are conducted to understand the effects of the system parameters on the nonlinear steady-state response. It is concluded that one-way clutch not only decreases the resonance amplitude of the driven pulley and shaft's rotational vibration, but also reduces the resonance region of the belt's transverse vibration.

Ding, Hu; Zu, Jean W.

2013-11-01

307

Public Access to Digital Material; A Call to Researchers: Digital Libraries Need Collaboration across Disciplines; Greenstone: Open-Source Digital Library Software; Retrieval Issues for the Colorado Digitization Project's Heritage Database; Report on the 5th European Conference on Digital Libraries, ECDL 2001; Report on the First Joint Conference on Digital Libraries.  

ERIC Educational Resources Information Center

These six articles discuss various issues relating to digital libraries. Highlights include public access to digital materials; intellectual property concerns; the need for collaboration across disciplines; Greenstone software for construction and presentation of digital information collections; the Colorado Digitization Project; and conferences…

Kahle, Brewster; Prelinger, Rick; Jackson, Mary E.; Boyack, Kevin W.; Wylie, Brian N.; Davidson, George S.; Witten, Ian H.; Bainbridge, David; Boddie, Stefan J.; Garrison, William A.; Cunningham, Sally Jo; Borgman, Christine L.; Hessel, Heather

2001-01-01

308

30 CFR 75.1108 - Approved conveyor belts.  

Code of Federal Regulations, 2010 CFR

...HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Fire Protection Fire Suppression Devices and Fire-Resistant Hydraulic Fluids on Underground Equipment § 75.1108 Approved conveyor belts. (a) Until December 31, 2009 conveyor...

2010-07-01

309

Periumbilical allergic contact dermatitis: blue jeans or belt buckles?  

PubMed

Nickel is the most ubiquitous contact allergen among children and adolescents. Metal blue jeans buttons and belts have been noted to cause nickel dermatitis around the umbilicus. For these children, traditional teaching is strict avoidance of all pants with metal snaps/buttons, particularly blue jeans. In this study we tested 90 pairs of blue jeans and 47 belts for nickel using the dimethylglyoxime spot test. Only 10% of blue jeans tested positive, while 53% of belts tested positive. Furthermore, 10 pairs of nickel-negative blue jeans remained negative after 10 washings. Overall we found no resistance to testing in clothing stores. From these results, we recommend that patients with allergic contact dermatitis secondary to nickel need not strictly avoid blue jeans and metal belt buckles. Rather, families should be encouraged to use the dimethylglyoxime spot test to test these items for nickel prior to purchase. PMID:15165199

Byer, Tara T; Morrell, Dean S

2004-01-01

310

Continuing scearch for a new type charging belt  

SciTech Connect

The EN Tandem accelerator at Oak Ridge National Laboratory (ORNL) operates to support a varied program of atomic physics research. As such, the demands on the accelerator often require a range of operation from {approximately}0.38 to 7.0 MV on the terminal, with low ripple and long term steady state operation. The standard charging belts obtained from the manufacture have generally given acceptable performance, but it is reasonable that modem manufacturing techniques and materials could increase belt lifetimes and improve accelerator performance, particularly voltage ripple. A new belt of significantly different construction from that of the conventional belts was specified, purchased, and installed in 1993. After 2800 hours of use at voltages from 0.38 to 5.8 MV, it was removed from the accelerator in early August 1995.

Jones, N.L.

1995-12-31

311

5. Detail, date stone in belt course above keystone, east ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. Detail, date stone in belt course above keystone, east portal of Tunnel 22, view to southeast, 380mm lens with electronic flash fill. - Southern Pacific Railroad Natron Cutoff, Tunnel 22, Milepost 581.85, Oakridge, Lane County, OR

312

32. photographer unknown undated AGGREGATE PLANT SHOWING MAIN BELT CONVEYOR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

32. photographer unknown undated AGGREGATE PLANT SHOWING MAIN BELT CONVEYOR UNITS AND STORAGE UNIT. - Bonneville Project, Columbia River, 1 mile Northeast of Exit 40, off Interstate 84, Bonneville, Multnomah County, OR

313

4. FORGE, ANVIL, PEDESTAL GRINDER, AND BELT DRIVES. NOTE WATERWHEEL ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. FORGE, ANVIL, PEDESTAL GRINDER, AND BELT DRIVES. NOTE WATERWHEEL NEEDLE VALVE CASTING HANGING ON THE WALL ABOVE THE FORGE. VIEW TO NORTH. - Santa Ana River Hydroelectric System, SAR-1 Machine Shop, Redlands, San Bernardino County, CA

314

"Abomination"--life as a Bible belt gay.  

PubMed

Drawing on observation, autoethnography, and audio-taped interviews, this article explores the religious backgrounds and experiences of Bible Belt gays. In the Bible Belt, Christianity is not confined to Sunday worship. Christian crosses, messages, paraphernalia, music, news, and attitudes permeate everyday settings. Consequently, Christian fundamentalist dogma about homosexuality-that homosexuals are bad, diseased, perverse, sinful, other, and inferior-is cumulatively bolstered within a variety of other social institutions and environments in the Bible Belt. Of the 46 lesbians and gay men interviewed for this study (age 18-74 years), most describe living through spirit-crushing experiences of isolation, abuse, and self-loathing. This article argues that the geographic region of the Bible Belt intersects with religious-based homophobia. Informants explained that negative social attitudes about homosexuality caused a range of harmful consequences in their lives including the fear of going to hell, depression, low self-esteem, and feelings of worthlessness. PMID:20391006

Barton, Bernadette

2010-01-01

315

46 CFR 111.105-27 - Belt drives.  

Code of Federal Regulations, 2012 CFR

...105-27 Section 111.105-27 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Hazardous Locations § 111.105-27 Belt drives. Each...

2012-10-01

316

Dynamics of the Earth's Radiation Belts and Inner Magnetosphere  

NASA Astrophysics Data System (ADS)

Trapped by Earth's magnetic field far above the planet's surface, the energetic particles that fill the radiation belts are a sign of the Sun's influence and a threat to our technological future. In the AGU monograph Dynamics of the Earth's Radiation Belts and Inner Magnetosphere, editors Danny Summers, Ian R. Mann, Daniel N. Baker, and Michael Schulz explore the inner workings of the magnetosphere. The book reviews current knowledge of the magnetosphere and recent research results and sets the stage for the work currently being done by NASA's Van Allen Probes (formerly known as the Radiation Belt Storm Probes). In this interview, Eos talks to Summers about magnetospheric research, whistler mode waves, solar storms, and the effects of the radiation belts on Earth.

Schultz, Colin

2013-12-01

317

Nanomaterial modifications on conductivity of coal conveyer belt  

SciTech Connect

By analyzing the macro electrical properties and the microscopic structure from SEM of nanomaterials modified mine transmission belt samples. The influences of the filling process of inorganic nano particle-filled rubber and PVC polymer on the physical properties of coal transmission belt is reviewed, as well as PTC and NTC effect on the stability of the physical properties and stability of materials. Influence of nano-materials and polymer materials for rubber and temperature changes in the plastic filled refining process. Crosslinker and major filler changes in the amount and filled plastic chain time on the conductivity of coal conveyer belt is studied. Influence of cure temperature. Cure time on the mechanical performance is studied. The microscopic mechanism of macro conductivity change of conveyer belt is discussed.

Zhang, J.C.; Zhang, Y.G.; Wang, T.T.; Yang, L.F.; Liu, S.M.; Yang, D.H.; Zhang, M.; Gao, X. [Zhongyuan University of Technology, Zhengzhou (China)

2008-08-15

318

29 CFR 1926.104 - Safety belts, lifelines, and lanyards.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Safety belts, lifelines, and lanyards...Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR...

2012-07-01

319

29 CFR 1926.104 - Safety belts, lifelines, and lanyards.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Safety belts, lifelines, and lanyards...Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR...

2013-07-01

320

29 CFR 1926.104 - Safety belts, lifelines, and lanyards.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Safety belts, lifelines, and lanyards...Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR...

2011-07-01

321

29 CFR 1926.104 - Safety belts, lifelines, and lanyards.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Safety belts, lifelines, and lanyards...Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR...

2010-07-01

322

Bunkhouse basement interior showing storage area and a conveyor belt ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Bunkhouse basement interior showing storage area and a conveyor belt (circa 1936) used to unload dry goods into the basement through an opening on the east side of the bunkhouse. - Sespe Ranch, Bunkhouse, 2896 Telegraph Road, Fillmore, Ventura County, CA

323

30 CFR 75.350 - Belt air course ventilation.  

Code of Federal Regulations, 2011 CFR

...Effective December 31, 2009, the air velocity in the belt entry must be at least...district manager may approve lower velocities in the ventilation plan based on specific mine conditions. Air velocities must be compatible with all...

2011-07-01

324

30 CFR 75.350 - Belt air course ventilation.  

Code of Federal Regulations, 2012 CFR

...Effective December 31, 2009, the air velocity in the belt entry must be at least...district manager may approve lower velocities in the ventilation plan based on specific mine conditions. Air velocities must be compatible with all...

2012-07-01

325

30 CFR 75.350 - Belt air course ventilation.  

Code of Federal Regulations, 2013 CFR

...Effective December 31, 2009, the air velocity in the belt entry must be at least...district manager may approve lower velocities in the ventilation plan based on specific mine conditions. Air velocities must be compatible with all...

2013-07-01

326

30 CFR 75.350 - Belt air course ventilation.  

Code of Federal Regulations, 2010 CFR

...Effective December 31, 2009, the air velocity in the belt entry must be at least...district manager may approve lower velocities in the ventilation plan based on specific mine conditions. Air velocities must be compatible with all...

2010-07-01

327

Preparation and characterization of highly planar flexible silver crystal belts.  

PubMed

We report a novel simple one-pot strategy for fabricating pure and highly planar silver (Ag) crystal belts. Unique single-crystal Ag belts (high width-to-thickness ratio ~50) were successfully synthesized in high yield (80 wt%) by reducing AgNO3 using N,N,N',N'-tetramethylethylenediamine (TEMED) as a reducing and a structure-determining agent in the presence of polyethylene glycol (PEG) under mild conditions. PMID:24287459

Varade, Dharmesh; Haraguchi, Kazutoshi

2014-01-21

328

The Gurupi Belt, northern Brazil: Lithostratigraphy, geochronology, and geodynamic evolution  

Microsoft Academic Search

The Gurupi Belt is located in northern Brazil on the southern margin of the São Luís Craton, which is dominated by juvenile calc-alkaline rocks formed in intra-oceanic island arcs between 2240 and 2150Ma. The Gurupi Belt consists of: (i) small lenses of an Archean metatonalite of 2594Ma; (ii) calc-alkaline\\/TTG tonalites and gneisses of 2147–2168Ma and juvenile Nd isotope signature, formed

Evandro L. Klein; Candido A. V. Moura; Robert S. Krymsky; William L. Griffin

2005-01-01

329

Equatorial irregularity belt and its movement during a magnetic storm  

NASA Technical Reports Server (NTRS)

Evidence for an equatorial irregularity belt and its movement during a magnetic storm has been obtained from Faraday rotation measurements at a chain of 140-MHz radio beacons receiving from the ATS-6 satellite. The stations covered a latitude region from the magnetic equator to the 45 deg N dip on the Indian subcontinent. An irregularity belt extending from the magnetic equator to about 27 deg N latitude was observed during the main phase of the magnetic storm of 10 January, 1976.

Vats, H. O.; Chandra, H.; Deshpande, M. R.; Rastogi, R. G.; Murthy, B. S.; Janve, A. V.; Rai, R. K.; Singh, M.; Gurm, H. S.; Jain, A. R.

1978-01-01

330

The role of salt in fold-and-thrust belts  

Microsoft Academic Search

Davis, D.M. and Engelder, T., 1985. The role of salt in fold-and-thrust belts. In: N.L. Carter and S. Uycda (Editors), Collision Tectonics: Deformation of Continental Lithosphere. Tectonophysics, 119: 67-88. The style of deformation in thin-skinned fold-and-thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks. Evaporites can

DAN M. DAVIS; TERRY ENGELDER

1985-01-01

331

Exploring fold and thrust belts in Google Earth  

NSDL National Science Digital Library

Google Earth enhances traditional geologic maps by allowing the viewer to explore three-dimensional map patterns and the interaction between structure and topography in dictating those map patterns. This activity overlays 4, 7.5' USGS quadrangles on Google Earth terrain and imagery data and encourages students to investigate common features of fold-and-thrust belts. Keywords: Google Earth, fold-and-thrust belt, visualization

Loveless, Jack

332

“Abomination”—Life as a Bible Belt Gay  

Microsoft Academic Search

Drawing on observation, autoethnography, and audio-taped interviews, this article explores the religious backgrounds and experiences of Bible Belt gays. In the Bible Belt, Christianity is not confined to Sunday worship. Christian crosses, messages, paraphernalia, music, news, and attitudes permeate everyday settings. Consequently, Christian fundamentalist dogma about homosexuality—that homosexuals are bad, diseased, perverse, sinful, other, and inferior—is cumulatively bolstered within a

Bernadette Barton

2010-01-01

333

V-type asteroids in the middle main belt  

Microsoft Academic Search

V-type asteroids are bodies whose surfaces are constituted of basalt. In the Main Asteroid Belt, most of these asteroids are assumed to come from the basaltic crust of Asteroid (4) Vesta. This idea is mainly supported by (i) the fact that almost all the known V-type asteroids are in the same region of the belt as (4) Vesta, i.e., the

F. Roig; D. Nesvorný; R. Gil-Hutton; D. Lazzaro

2008-01-01

334

Structure of possible long-lived asteroid belts  

Microsoft Academic Search

High-resolution simulations are used to map out the detailed structure of two long-lived stable belts of asteroid orbits in the inner Solar system. The Vulcanoid belt extends from 0.09 to 0.20au, though with a gaps at 0.15 and 0.18au corresponding to de-stabilizing mean motion resonances with Mercury and Venus. As collisional evolution proceeds slower at larger heliocentric distances, km-sized or

N. W. Evans; S. A. Tabachnik

2002-01-01

335

The Origin and Evolution of the Asteroid Main Belt  

Microsoft Academic Search

Using a fully autonomous spacecraft - Bering - we propose to detect and study\\u000asub-km asteroids from an orbit within the asteroid Main Belt. The main purpose\\u000aof the proposed Bering mission is to detect a statistically significant sample\\u000aof an expected population of approximately 10^(10) main belt asteroids in the\\u000asize range 1 m to 1 km. These asteroids

Philip R. Bidstrup; Henning Haack; Anja C. Andersen; Rene Michelsen; John Leif Jorgensen

2005-01-01

336

Sedimentology and facies of a Mississippi River meander belt  

SciTech Connect

The meander belt of the Mississippi River in Southeastern Missouri, consists of four facies: river channel, chute, levee, and abandoned channel fill. A depositional model and vertical sequences have been developed from drill cores, vibracores, fathometer surveys, and mapping of these facies. This model and the vertical sequences compare very well to ancient sequences. The vertical sequences observed in cores through the various facies systems have systematic variations and associations that serve as models for meander belt fluvial systems.

Pryor, W.A.; Jordan, D.W.

1988-01-01

337

Trapped belt variations and their effects on human space flights  

NASA Technical Reports Server (NTRS)

Variations in the Earth's trapped (Van Allen) belts produced by solar flare particle events are not well understood. This paper reports the existence of a second proton belt and its subsequent decay as measured by a tissue-equivalent proportional counter and a particle spectrometer on five Space Shuttle flights covering an 18-month period. The creation of this second belt is attributed to the injection of particles from a solar particle event which occurred at 2246 UT, March 22, 1991. Comparisons with observations onboard the Russian Mir space station and other unmanned satellites are made. Shuttle measurements and data from other spacecraft are used to determine that the e-folding time of the peak of the second proton belt was ten months. Proton populations in the second belt returned to values of quiescent times within 18 months. The increase in absorbed dose attributed to protons in the second belt was approximately 20 percent. Passive dosimeter measurements were in good agreement with this value.

Robbins, Donald E.; Badhwar, Gautam D.

1993-01-01

338

Tectonic setting of the Kolar Schist Belt, Karnataka, India  

NASA Technical Reports Server (NTRS)

The tectonic setting of the Kolar Schist Belt and why the belt may represent a late Archean suture was discussed. The isotopic and chronological evidence that suggest diverse origins of the various packages of supracrustal rocks within the schist belt and the two gneiss terrains adjoining the belt were summarized. The eastern and western amphibolites were derived from sources at similar depths in the mantle (probably at similar ages, ca. 2.7 Ga), but these sources had distinct trace element compositions and histories. A distinctive feature of these differences was shown by the differences between the east and west amphibolites on a Ce vs. Nd diagram. In the gneisses the age and isotopic evidence suggest that the two terranes had distinct histories until after 2520 Ma and by 2420 Ma (Ar-40/Ar-39 age of muscovite in the sheared margin of the schist belt). Based on these data, the schist belt probably represents the site of accretion of diverse fragments (terrains) to the margin of the craton in the latest Archean, possibly as an Archean analog to the Phanerozoic North American Cordillera.

Hanson, G. N.; Krogstad, E. J.; Rajamani, V.

1988-01-01

339

Promoting automobile safety belt use by young children.  

PubMed Central

A program using behavioral practice, assertiveness training, and social and contrived reinforcers was developed to establish and maintain automobile safety belt use by young children. Sixteen children (ages 4.8 to 7 years) who never used their safety belts during a 5-day preexperimental observation period were randomly assigned to two groups of eight each. A multiple baseline design across groups was used to evaluate the effectiveness of the training program. During the 8-day baseline period for Group 1, no children used their safety belts when unobtrusively observed while being driven from school. During the 26-day intervention period, the children were buckled up on 96% of the observations. Follow-up probes conducted 2-3 months after program discontinuance found safety belt use to range from 86% to 100%. For Group 2, the 14-day baseline safety belt use averaged 6% and increased to a mean of 81% during the 20-day training and maintenance program. Follow-up probes 2-3 months later found safety belt use to occur during 75% to 96% of the observations. Parent questionnaires indicated the generalizability and social validity of the program. PMID:3610893

Sowers-Hoag, K M; Thyer, B A; Bailey, J S

1987-01-01

340

Tectonic setting of the Kolar Schist Belt, Karnataka, India  

NASA Astrophysics Data System (ADS)

The tectonic setting of the Kolar Schist Belt and why the belt may represent a late Archean suture was discussed. The isotopic and chronological evidence that suggest diverse origins of the various packages of supracrustal rocks within the schist belt and the two gneiss terrains adjoining the belt were summarized. The eastern and western amphibolites were derived from sources at similar depths in the mantle (probably at similar ages, ca. 2.7 Ga), but these sources had distinct trace element compositions and histories. A distinctive feature of these differences was shown by the differences between the east and west amphibolites on a Ce vs. Nd diagram. In the gneisses the age and isotopic evidence suggest that the two terranes had distinct histories until after 2520 Ma and by 2420 Ma (Ar-40/Ar-39 age of muscovite in the sheared margin of the schist belt). Based on these data, the schist belt probably represents the site of accretion of diverse fragments (terrains) to the margin of the craton in the latest Archean, possibly as an Archean analog to the Phanerozoic North American Cordillera.

Hanson, G. N.; Krogstad, E. J.; Rajamani, V.

341

Radial transport in the Earth's radiation belts (Invited)  

NASA Astrophysics Data System (ADS)

For over forty years the standard approach to modeling the dynamics of the Earth's radiation belts has been based on a diffusion equation, which can be derived from the Vlasov equation using a quasilinear approximation. The radiation belt diffusion equation describes the evolution of a particle distribution function in a space of one or several of the three adiabatic invariants associated with the motions of a charged particle in a dipole magnetic field. Increasingly, observations and theoretical studies suggest that fully nonlinear transport, not modeled by quasilinear diffusion, plays an important role in radiation belt dynamics, e.g., the shock-drift mechanism modeled by Li et al. [1993]. This presentation will focus on radiation belt particle transport across magnetic L-shells (loosely called radial transport). Radial transport is thought to be one of the primary drivers of radiation belt dynamics. A comprehensive review of the known mechanisms of radial transport and some of their effects will be given, including those that can be modeled with a diffusion equation and those requiring a fully nonlinear treatment. Li, X., I. Roth, M. Temerin, J. R. Wygant, M. K. Hudson, and J. B. Blake, (1993), Simulations of the prompt energization and transport of radiation belt particles during the March 24, 1991 SSC, Geophys. Res. Lett., 20, 2423.

Kress, B. T.; Ukhorskiy, A. Y.; Hudson, M. K.

2010-12-01

342

Non-Linear Vibration of Power Transmission Belts  

NASA Astrophysics Data System (ADS)

Non-linear vibration of a prototypical power transmission belt system, which is excited by pulleys having slight eccentricity, is investigated through experimental and analytical methods. Laboratory measurements demonstrate the role of non-linearity in setting the belt's response, particularly in the near-resonance region, and at high running speeds. The belt is coated with a retroreflective medium so as to improve displacement and velocity measurements made through non-contact laser interferometry. A frequency crossing diagram relates the belt's speed-dependent excitation and natural frequencies, and is shown to be useful for identifying those speeds at which resonance is expected. Distinctive jump and hysteresis phenomena in the near-resonant response are observed experimentally, and are also studied with a model that includes non-linear stretching of the belt. In that regard, a modal perturbation solution is developed in the context of the asymptotic method of Krylov, Bogoliubov and Mitropolsky for a general, continuous, non-autonomous, gyroscopic system with weakly non-linear stiffness. The solution is subsequently specialized to the belt vibration problem at hand. Near- and exact-resonant response amplitudes are predicted by the perturbation method, and they are compared with those obtained by laboratory tests and by direct numerical simulation of the non-linear model.

Moon, J.; Wickert, J. A.

1997-03-01

343

Development of the western Idaho ultramafic belt  

SciTech Connect

The 164-mile-long western Idaho ultramafic belt contains small bodies of dunite, serpentinite, metaharzburgite, and clinopyroxenite that mainly lie near the suture zone joining the Blue Mountains island arc accreted terrane and the pre-Cretaceous continental crust. The main ultramafic areas are: (1) in the Cuddy Mountain-Sturgill Peak region, where sheared serpentinite occurs along a high-angle reverse fault zone between two subterranes of the Blue Mountain terrane, (2) in the New Meadows tectonic block where dunites, harzburgites, and chromitites occur with metamorphosed cherts, greywackes, and exhalative rocks, (3) near Riggins where serpentinite occurs in metasedimentary rocks of the Mesozoic-age Riggins Group, (4) in the South Fork Clearwater River region where anthophyllite metaharzburgites and Cr-rich clinopyroxenites are enclosed within gneissic equivalents of the Riggins Group and in Cretaceous-age felsic plutonic rocks, and (5) in the Lowell-Kamiah-Dworshak Reservoir region where additional anthophyllite metaharzburgites occur in Proterozoic-age metasedimentary rocks. After the ultramafic rocks were formed, plate convergence led to their obduction onto the Mesozoic margin of North America. Compression accompanying the docking of the Blue Mountains island arc and then the emplacement of the Idaho batholith metamorphosed most of the ultramafic bodies to the greenschist and amphibolite facies and remobilized them along faults to their present locations within host rocks of widely varying ages.

Bonnichsen, B. (Univ. of Idaho, Moscow, ID (United States). Idaho Geological Survey); Godchaux, M.M. (Mount Holyoke Coll., South Hadley, MA (United States). Dept. of Geology)

1993-04-01

344

Radiation Belt Electron Dynamics: Modeling Atmospheric Losses  

NASA Technical Reports Server (NTRS)

The first year of work on this project has been completed. This report provides a summary of the progress made and the plan for the coming year. Also included with this report is a preprint of an article that was accepted for publication in Journal of Geophysical Research and describes in detail most of the results from the first year of effort. The goal for the first year was to develop a radiation belt electron model for fitting to data from the SAMPEX and Polar satellites that would provide an empirical description of the electron losses into the upper atmosphere. This was largely accomplished according to the original plan (with one exception being that, for reasons described below, the inclusion of the loss cone electrons in the model was deferred). The main concerns at the start were to accurately represent the balance between pitch angle diffusion and eastward drift that determines the dominant features of the low altitude data, and then to accurately convert the model into simulated data based on the characteristics of the particular electron detectors. Considerable effort was devoted to achieving these ends. Once the model was providing accurate results it was applied to data sets selected from appropriate periods in 1997, 1998, and 1999. For each interval of -30 to 60 days, the model parameters were calculated daily, thus providing good short and long term temporal resolution, and for a range of radial locations from L = 2.7 to 3.9. .

Selesnick, R. S.

2003-01-01

345

Setouchi volcanic belt: home of sanukitoid  

NASA Astrophysics Data System (ADS)

The Setouchi volcanic belt (SVB) is located in the present forearc region, ˜80 km south of the Quaternary volcanic front and extends for about 600 km along the SW Japan arc, with five major volcanic regions. Among these, the occurrence of high-Mg andesitic sanukitoids is limited to the three central areas. Formation of the SVB parallel to the arc-trench system and the occurrence of calc-alkaline andesites in the SVB may indicate the involvement of the subducting lithosphere in producing Setouchi magmas. New K-Ar age data for Setouchi lavas confirmed an earlier suggestion that Setouchi magmatism took place within the short period of 12-15 Ma. This, together with the analyses of magnetic lineation on the Shikoku Basin sea floor, suggests that the magmatism was caused by subduction of very young lithosphere of the Philippine Sea plate. Such unusual subduction of a young, buoyant plate may have resulted from the southward drift of the SW Japanese arc sliver associated with the opening of the Japan Sea backarc basin.

Tatsumi, Y.

2003-04-01

346

Predicting Occultations by Kuiper Belt Objects  

NASA Astrophysics Data System (ADS)

Observation of stellar occultations by a planetesimal is a powerful technique to characterize many properties of the occulting object, including its size, shape, and atmospheric extent. This technique is extremely useful for Kuiper Belt Objects, the proximities of which make it virtually impossible to determine shape and atmospheric properties with any other remote sensing technique currently available. Our group has devised a new technique to predict when these rare occultations will occur. The technique makes use of a small 1 hr) set of observations with the MegaCam, from which a master point source catalog is produced with ~0.02” astrometric accuracy. The MegaCam observations are also used to correct the ephemerides of the target KBOs. The combined result is occultation predictions with precision of 2000 km or better - similar to the size of the target KBOs - as far into the future as 2016. I will present the results of a pilot study of 7 objects, and some preliminary efforts to catch the object, Quaoar, in the act of occultation. With observations made by the Acquisition Camera on Gemini-N of Quaoar’s close passage to a star, we have been able to place stringent upper limits on Quaoar’s atmosphere, with a surface pressure no more than ~90 nanobars and a mean surface temperature of no more than 44 K. These observations demonstrate the utility of occultation observations in characterizing remote planetesimals.

Fraser, Wesley; Gwyn, S.; Trujillo, C.; Brown, M. E.; Kavelaars, J.; Stephens, A.; Gimeno, G.

2013-10-01

347

Cretaceous biostratigraphy in the Wyoming thrust belt.  

USGS Publications Warehouse

In the Cretaceous section of the thrust belt, fossils are especially useful for dating and correlating repetitive facies of different ages in structurally complex terrain. The biostratigraphic zonation for the region is based on megafossils (chiefly ammonites) , which permit accurate dating and correlation of outcrop sections, and which have been calibrated with the radiometric time scale for the Western Interior. Molluscan and vertebrate zone fossils are difficult to obtain from the subsurface, however, and ammonites are restricted to rocks of marine origin. Palynomorphs (plant microfossils) have proven to be the most valuable fossils in the subsurface because they can be recovered from drill cuttings. Palynomorphs also are found in both marine and nonmarine rocks and can be used for correlation between facies. Stratigraphic ranges of selected Cretaceous marine and nonmarine palynomorphs in previously designated reference sections in Fossil Basin, Wyoming are correlated with the occurrence of ammonites and other zone fossils in the same sections. These correlations can be related to known isotopic ages, and they contribute to the calibration of palynomorph ranges in the Cretaceous of the Western Interior. -from Authors

Nichols, D. J.; Jacobson, S. R.

1982-01-01

348

Radiation belts study in RESONANCE project  

NASA Astrophysics Data System (ADS)

The Earth’s inner magnetosphere is an important part of space weather framework. Outer radiation belt is a home for numerous communication and navigation satellites. But besides this practical problem, this region is a theoretical nugget. Hot magnetospheric, cold plas¬mospheric, and, in contrast, high energy plasma coexist here. Such non-equilibrium state of plasma is glued by various plasma oscillations actively interacting with particles and resulting, in particular, in spatial and velocity diffusion. Diffusion influences acceleration and precipitation of particles and defines their life¬time in the Earth’s magnetosphere. The project RESONANCE is aimed to study the whole complex of these issues, both practical (space weather), and fundamental (nonlinear plasma dynamics). The project RESONANCE is a part of the Russian Federal State Program. Lavochkin Association is responsi¬ble for preparation and testing of the satellites. Space Research Institute of the Russian Academy of Sciences is a leading scientific organization. Besides Russian scientists, specialists from Austria, Bulgaria, Czech Re¬public, Finland, France, Germany, Greece, Poland, Slovakia, Ukraine, USA take part.

Mogilevsky, Mikhail; Demekhov, Andrei; Zelenyi, Lev; Petrukovich, Anatoly; Shklyar, David

349

Subaru Main Belt Asteroid Survey (SMBAS)—Size and color distributions of small main-belt asteroids  

Microsoft Academic Search

Since February, 2001, we have been conducting a series of survey observations to investigate the physical property of very small Main Belt Asteroids (sub-km MBAs) using the Subaru prime-focus camera (Suprime-Cam) attached to the 8.2m Subaru telescope. We call our surveys “SMBAS: Subaru Main-Belt Asteroids Survey”. This paper presents the results of the second SMBAS (SMBAS-II) which was performed in

F. Yoshida; T. Nakamura

2007-01-01

350

Processes on the Young Earth and the Habitats of Early Life  

NASA Astrophysics Data System (ADS)

Conditions at the surface of the young (Hadean and early Archean) Earth were suitable for the emergence and evolution of life. After an initial hot period, surface temperatures in the late Hadean may have been clement beneath an atmosphere containing greenhouse gases over an ocean-dominated planetary surface. The first crust was mafic and it internally melted repeatedly to produce the felsic rocks that crystallized the Jack Hills zircons. This crust was destabilized during late heavy bombardment. Plate tectonics probably started soon after and had produced voluminous continental crust by the mid Archean, but ocean volumes were sufficient to submerge much of this crust. In the Hadean and early Archean, hydrothermal systems around abundant komatiitic volcanism may have provided suitable sites to host the earliest living communities and for the evolution of key enzymes. Evidence from the Isua Belt, Greenland, suggests life was present by 3.8 Gya, and by the mid-Archean, the geological record both in the Pilbara in Western Australia and the Barberton Greenstone Belt in South Africa shows that microbial life was abundant, probably using anoxygenic photosynthesis. By the late Archean, oxygenic photosynthesis had evolved, transforming the atmosphere and permitting the evolution of eukaryotes.

Arndt, Nicholas T.; Nisbet, Euan G.

2012-05-01

351

Seat Belts Pay Off. The Use of Economic Incentives and Public Education to Increase Seat Belt Use in a Community. Final Report.  

ERIC Educational Resources Information Center

A six-month campaign to increase seat belt use in Chapel Hill and Carrboro, North Carolina centered around the idea of giving out economic incentives for seat belt wearing. The approach was to stop vehicles at random and give all belted vehicle occupants a small prize and a chance for a large cash prize. Precampaign activities involve collecting…

Campbell, B. J.; And Others

352

Reassessing the biogenicity of Earth's oldest trace fossil with implications for biosignatures in the search for early life.  

PubMed

Microtextures in metavolcanic pillow lavas from the Barberton greenstone belt of South Africa have been argued to represent Earth's oldest trace fossil, preserving evidence for microbial life in the Paleoarchean subseafloor. In this study we present new in situ U-Pb age, metamorphic, and morphological data on these titanite microtextures from fresh drill cores intercepting the type locality. A filamentous microtexture representing a candidate biosignature yields a U-Pb titanite age of 2.819 ± 0.2 Ga. In the same drill core hornfelsic-textured titanite discovered adjacent to a local mafic sill records an indistinguishable U-Pb age of 2.913 ± 0.31 Ga, overlapping with the estimated age of intrusion. Quantitative microscale compositional mapping, combined with chlorite thermodynamic modeling, reveals that the titanite filaments are best developed in relatively low-temperature microdomains of the chlorite matrix. We find that the microtextures exhibit a morphological continuum that bears no similarity to candidate biotextures found in the modern oceanic crust. These new findings indicate that the titanite formed during late Archean ca. 2.9 Ga thermal contact metamorphism and not in an early ca. 3.45 Ga subseafloor environment. We therefore question the syngenicity and biogenicity of these purported trace fossils. It is argued herein that the titanite microtextures are more likely abiotic porphyroblasts of thermal contact metamorphic origin that record late-stage retrograde cooling in the pillow lava country rock. A full characterization of low-temperature metamorphic events and alternative biosignatures in greenstone belt pillow lavas is thus required before candidate traces of life can be confirmed in Archean subseafloor environments. PMID:24912193

Grosch, Eugene G; McLoughlin, Nicola

2014-06-10

353

Reassessing the biogenicity of Earth’s oldest trace fossil with implications for biosignatures in the search for early life  

PubMed Central

Microtextures in metavolcanic pillow lavas from the Barberton greenstone belt of South Africa have been argued to represent Earth’s oldest trace fossil, preserving evidence for microbial life in the Paleoarchean subseafloor. In this study we present new in situ U–Pb age, metamorphic, and morphological data on these titanite microtextures from fresh drill cores intercepting the type locality. A filamentous microtexture representing a candidate biosignature yields a U–Pb titanite age of 2.819 ± 0.2 Ga. In the same drill core hornfelsic-textured titanite discovered adjacent to a local mafic sill records an indistinguishable U–Pb age of 2.913 ± 0.31 Ga, overlapping with the estimated age of intrusion. Quantitative microscale compositional mapping, combined with chlorite thermodynamic modeling, reveals that the titanite filaments are best developed in relatively low-temperature microdomains of the chlorite matrix. We find that the microtextures exhibit a morphological continuum that bears no similarity to candidate biotextures found in the modern oceanic crust. These new findings indicate that the titanite formed during late Archean ca. 2.9 Ga thermal contact metamorphism and not in an early ca. 3.45 Ga subseafloor environment. We therefore question the syngenicity and biogenicity of these purported trace fossils. It is argued herein that the titanite microtextures are more likely abiotic porphyroblasts of thermal contact metamorphic origin that record late-stage retrograde cooling in the pillow lava country rock. A full characterization of low-temperature metamorphic events and alternative biosignatures in greenstone belt pillow lavas is thus required before candidate traces of life can be confirmed in Archean subseafloor environments. PMID:24912193

Grosch, Eugene G.; McLoughlin, Nicola

2014-01-01

354

Timescale dependent deformation of orogenic belts?  

NASA Astrophysics Data System (ADS)

The principle aim to link geodetic, paleoseismologic and geologic estimates of fault slip is to extrapolate the respective rates from one timescale to the other to finally predict the recurrence interval of large earthquakes, which threat human habitats. This approach however, is based on two often implicitly made assumptions: a uniform slip distribution through time and space and no changes of the boundary conditions during the time interval of interest. Both assumptions are often hard to verify. A recent study, which analysed an exceptionally complete record of seismic slip for the Wasatch and related faults (Basin and Range province), ranging from 10 yr to 10 Myr suggests that such a link between geodetic and geologic rates might not exist, i.e., that our records of fault displacement may depend on the timescale over which they were measured. This view derives support from results of scaled 2D sandbox experiments, as well as numerical simulations with distinct elements, both of which investigated the effect of boundary conditions such as flexure, mechanic stratigraphy and erosion on the spatio-temporal distribution of deformation within bivergent wedges. We identified three types of processes based on their distinct spatio-temporal distribution of deformation. First, incremental strain and local strain rates are very short-lived are broadly distributed within the bivergent wedge and no temporal pattern could be established. Second, footwall shortcuts and the re-activation of either internal thrusts or of the retro shear-zone are irregularly distributed in time and are thus not predictable either, but last for a longer time interval. Third, the stepwise initiation and propagation of the deformation front is very regular in time, since it depends on the thickness of the incoming layer and on its internal and basal material properties. We consider the propagation of the deformation front as an internal clock of a thrust belt, which is therefore predictable. A deformation front advance cycle requires the longest timescale. Thus, despite known and constant boundary conditions during the simulations, we found only one regular temporal pattern of deformation in a steady active bivergent-wedge. We therefore propose that the structural inventory of an orogenic belt is hierarchically ordered with respect to accumulated slip, in analogy to the discharge pattern in a drainage network. The deformation front would have the highest, a branching splay the lowest order. Since kinematic boundary conditions control deformation front advance, its timing and the related maximum magnitude of finite strain, i.e. throw on the frontal thrust are predictable. However, the number of controlling factors, such as the degree of strain softening, the orientation of faults or fluid flow and resulting cementation of faults, responsible for the reactivation of faults increases with increasing distance from the deformation front. Since it is rarely possible to determine the complete network of forces within a wedge, the reactivation of lower order structures is not predictable in time and space. Two implications for field studies may emerge: A change of the propagation of deformation can only be determined, if at least two accretion cycles are sampled. The link between geodetic, paleoseismologic and geologic fault slip estimates can only be successfully derived if the position of the investigated fault within the hierarchical order has not changed over the time interval of interest.

Hoth, S.; Friedrich, A. M.; Vietor, T.; Hoffmann-Rothe, A.; Kukowski, N.; Oncken, O.

2004-12-01

355

Super-Comet or Big Asteroid Belt?  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Figure 1: Spectrograph of HD 69830

This graph of data from NASA's Spitzer Space Telescope demonstrates that the dust around a nearby star called HD 69830 (upper line) has a very similar composition to that of Comet Hale-Bopp. Spitzer spotted large amounts of this dust in the inner portion of the HD 69830 system.

The bumps and dips seen in these data, or spectra, represent the 'fingerprints' of various minerals. Spectra are created when an instrument called a spectrograph spreads light out into its basic parts, like a prism turning sunlight into a rainbow. These particular spectra reveal the presence of the silicate mineral called olivine, and more specifically, a type of olivine called forsterite, which is pictured in the inset box. Forsterite is a bright-green gem found on Earth, on the 'Green Sand Beach' of Hawaii among other places; and in space, in comets and asteroids.

Because the dust around HD 69830 has a very similar make-up to that of Comet Hale-Bopp, astronomers speculate that it might be coming from a giant comet nearly the size of Pluto. Such a comet may have been knocked into the inner solar system of HD 69830, where it is now leaving in its wake a trail of evaporated dust.

Nonetheless, astronomers say the odds that Spitzer has caught a 'super-comet' spiraling in toward its star - an unusual and relatively short-lived event - are slim. Instead, they favor the theory that the observed dust is actually the result of asteroids banging together in a massive asteroid belt.

The data of HD 69830's dust were taken by Spitzer's infrared spectrograph. The data of Comet Hale-Bopp were taken by the European Space Agency's Infrared Observatory Satellite. The picture of forsterite comes courtesy of Dr. George Rossman, California Institute of Technology, Pasadena.

2005-01-01

356

Mobile Belts, High Lithosphere Temperatures, and Subduction Zone Backarcs  

NASA Astrophysics Data System (ADS)

At many continental plate boundaries, there are mobile orogenic belts or zones of distributed deformation hundreds of kilometres wide. An important characteristic of "mobile belts" is a long geological history of ongoing deformation or of repeated deformation events that suggests long-term lithosphere weakness compared to cratons. Thus, they are "mobile" not just because they are subject to deforming forces, but also because they are weak. In contrast, Precambrian cratons have exhibited very little internal deformation for long geological periods, and are inferred to have long-term strength. We propose that most mobile belts are weak because they are hot, and they are hot because they are in backarcs or geologically recent backarcs. Most continental backarcs are observed to be hot; the temperature at the Moho is ~900C compared to ~400C for cratons, and the lithosphere thicknesses are 50-60 km compared to more than 250 km for cratons. The high temperatures result in thermal expansion and the common high elevations in backarc mobile belts, even where the crust is not thickened. Backarc mobile belt lithospheres are at least a factor of 10 weaker than those of cratons. Backarcs may be hot and have thin, weak lithospheres because of the water driven upward into the backarc mantle wedge from dehydration of the underlying subducting plate. The water reduces the effective asthenosphere viscosity and allows vigorous free convection. High backarc temperatures appear to decay after subduction stops, with a time constant of 50-100 m.y. Many continental mobile belts are hot enough for there to be a weak lower crust detachment so surface tectonics are decoupled from the upper mantle. For example, foreland thrusting at the craton edge of a mobile belt may be driven by continental margin plate boundary forces 100s of km away, with translation of the crust over a lower crust detachment.

Hyndman, R. D.

2003-12-01

357

The Evolution of the Main belt and NEA size Distributions  

NASA Astrophysics Data System (ADS)

The size distribution of the main belt is governed by collisional evolution as well as by the non-collisional removal of bodies due to the combination of radition forces and resonances. The NEA size distribution is governed in part by the size distribution of the main belt, its primary source, but differs somewhat from it due to the size dependent processes which deliver asteroids from the main belt to near earth space. These two size distributions provide a powerful constraint on any model of asteroid collisional evolution and NEA delivery. Additional constraints are provided by the cratering records on observed asteroids, such as Gaspra and Ida, and by the cosmic ray exposure (CRE) ages of meteorites, which indicate that meter-sized bodies have collisional lifetimes on the order of 10 Myr or more in the main belt. A collisional evolution model for the main belt which incorporates non-collisional removal processes can fit all of these constraints with reasonable parameter choices. The main parameters in our model are the strength vs. size scaling law and the removal rate of bodies from the main belt as a function of size. With removal rates consistent with the estimates of Bottke et al. (2002) and reasonable strength scaling laws, we are able to match the main belt size distributions observed by either the Sloan Digital Sky Survey or the Spacewatch Survey. The NEA population produced in our model is consistent with the observed NEA population, as determined by Rabinowitz (2000). In addition, lifetimes for meter-sized bodies are consistent with meteorite CRE ages. The inferred population of bodies from 1 m to 1 km is consistent with the cratering records on Gaspra and Ida. Asteroids larger than 10 km have mean collisional lifetimes > 4.5 Byr.

O'Brien, D. P.; Greenberg, R.

2002-09-01

358

Electrospun nanofiber belts made from high performance copolyimide  

NASA Astrophysics Data System (ADS)

Electrospun nanofibers based on copolyimides were made, aiming at finding a promising method for improving the mechanical properties of electrospun polyimide nanofibers. The copolyimide had a backbone consisting of 3,3',4,4'-biphenyl-tetracarboxylic dianhydride (BPDA), biphenylamide (BPA) and 4,4'-oxydianiline (ODA) residues. The structure and composition of the copolyimide was controlled by the ratio of rigid BPA and flexible ODA moieties. The electrospun copolyimide nanofibers were collected in the form of a belt using a rotating disc with a rim of 8 mm width. Scanning electron microscopy (SEM), infrared (IR) spectroscopy, x-ray scattering and tensile testing, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were used to characterize the nanofiber belts. The nanofibers had a diameter range from 80 to 300 nm and were well aligned in the belts. The thermal stability of the nanofiber belts was over 460 °C. The tensile test showed that the copolyimide nanofiber belts had much better mechanical properties than either of the flexible and rigid homo-polyimide (homo-PI) nanofiber belts. The tensile strength, modulus and elongation to break of the copolyimide nanofiber belt with BPA/ODA ratio of 40/60 are respectively 1.1 ± 0.1 GPa, 6.2 ± 0.7 GPa and 20.8 ± 1.2%, compared to 459 ± 36 MPa, 2.1 ± 0.3 GPa and 41.3 ± 2.2% for BPDA/ODA homo-PI as well as 384 ± 18 MPa, 11.5 ± 0.6 GPa and 3.9 ± 0.1% for BPDA/BPA homo-PI. The important feature is that the electrospun polymer nanofibers can be made very strong by using copolyimides as spinning materials.

Chen, Shuiliang; Hu, Ping; Greiner, Andreas; Cheng, Chuyun; Cheng, Haofang; Chen, Fangfang; Hou, Haoqing

2008-01-01

359

A new interpretation for the interference zone between the southern Brasília belt and the central Ribeira belt, SE Brazil  

NASA Astrophysics Data System (ADS)

In southeastern Brazil, the Neoproterozoic NNW-SSE trending southern Brasília belt is apparently truncated by the ENE-WSW central Ribeira belt. Different interpretations in the literature of the transition between these two belts motivated detailed mapping and additional age dating along the contact zone. The result is a new interpretation presented in this paper. The southern Brasília belt resulted from E-W collision between the active margin of the Paranapanema paleocontinent, on the western side, now forming the Socorro-Guaxupé Nappe, with the passive margin of the São Francisco paleocontinent on the eastern side. The collision produced an east vergent nappe stack, the Andrelândia Nappe System, along the suture. At its southern extreme the Brasília belt was thought to be cut off by a shear zone, the "Rio Jaguari mylonites", at the contact with the Embu terrane, pertaining to the Central Ribeira belt. Our detailed mapping revealed that the transition between the Socorro-Guaxupé Nappe (Brasília belt) and the Embu terrane (Ribeira belt) is not a fault but rather a gradational transition that does not strictly coincide with the Rio Jaguari mylonites. A typical Cordilleran type magmatic arc batholith of the Socorro-Guaxupé Nappe with an age of ca. 640 Ma intrudes biotite schists of the Embu terrane and the age of zircon grains from three samples of metasedimentary rocks, one to the south, one to the north and one along the mylonite zone, show a similar pattern of derivation from a Rhyacian source area with rims of 670-600 Ma interpreted as metamorphic overgrowth. We dated by LA-MC-ICPMS laser ablation (U-Pb) zircon grains from a calc-alkaline granite, the Serra do Quebra-Cangalha Batholith, located within the Embu terrane at a distance of about 40 km south of the contact with the Socorro Nappe, yielding an age of 680 ± 13 Ma. This age indicates that the Embu terrane was part of the upper plate (Socorro-Guaxupé Nappe) by this time. Detailed mapping indicates that the mylonite zone is not a plate boundary because motion along it is maximum a few tens of kilometres and the same litho-stratigraphic units are present on either side. Based on these arguments, the new interpretation is that the Embu terrane is the continuation of the Socorro-Guaxupé Nappe and therefore also part of the active margin of the Paranapanema paleocontinent. The Brasília belt is preserved even further within the central Ribeira belt than previously envisaged.

Trouw, Rudolph A. J.; Peternel, Rodrigo; Ribeiro, Andre; Heilbron, Mônica; Vinagre, Rodrigo; Duffles, Patrícia; Trouw, Camilo C.; Fontainha, Marcos; Kussama, Hugo H.

2013-12-01

360

Survey of current situation in radiation belt modeling  

NASA Technical Reports Server (NTRS)

The study of Earth's radiation belts is one of the oldest subjects in space physics. Despite the tremendous progress made in the last four decades, we still lack a complete understanding of the radiation belts in terms of their configurations, dynamics, and detailed physical accounts of their sources and sinks. The static nature of early empirical trapped radiation models, for examples, the NASA AP-8 and AE-8 models, renders those models inappropriate for predicting short-term radiation belt behaviors associated with geomagnetic storms and substorms. Due to incomplete data coverage, these models are also inaccurate at low altitudes (e.g., <1000 km) where many robotic and human space flights occur. The availability of radiation data from modern space missions and advancement in physical modeling and data management techniques have now allowed the development of new empirical and physical radiation belt models. In this paper, we will review the status of modern radiation belt modeling. Published by Elsevier Ltd on behalf of COSPAR.

Fung, Shing F.

2004-01-01

361

Angle stations in or for endless conveyor belts  

DOEpatents

In an angle station for an endless conveyor belt, there are presented to each incoming run of the belt stationary curved guide members (18, 19) of the shape of a major segment of a right-circular cylinder and having in the part-cylindrical portion (16 or 17) thereof rectangular openings (15) arranged in parallel and helical paths and through which project small freely-rotatable rollers (14), the continuously-changing segments of the curved surfaces of which projecting through said openings (15) are in attitude to change the direction of travel of the belt (13) through 90.degree. during passage of the belt about the part-cylindrical portion (16 or 17) of the guide member (18 or 19). The rectangular openings (15) are arranged with their longer edges lengthwise of the diagonals representing the mean of the helix but with those of a plurality of the rows nearest to each end of the part-cylindrical portion (16 or 17) slightly out of axial symmetry with said diagonals, being slightly inclined in a direction about the intersections (40) of the diagonals of the main portion of the openings, to provide a "toe-in" attitude in relation to the line of run of the endless conveyor belt.

Steel, Alan (Glasgow, GB6)

1987-04-07

362

The Kolar Schist Belt: A possible Archaean suture zone  

NASA Astrophysics Data System (ADS)

The Kolar Schist Belt represents a N-S trending discontinuity in the structures, lithologies, and emplacement and metamorphic ages of late Archean gneisses. The suggestion of a much older basement on the west side of the belt is not seen on the east. Within the schist belt amphibolites from each side have distinctly different chemical characteristics, suggesting different sources at similar mantle depths. These amphibolites were probably not part of a single volcanic sequence, but may have formed about the same time in two completely different settings. Could the amphibolites with depleted light REE patterns represent Archean ocean floor volcanics which are derived from a mantle source with a long term depletion of the light REE? Why are the amphibolites giving an age which may be older than the exposed gneisses immediately on either side of the belt? These results suggest that it is necessary to seriously consider whether the Kolar Schist Belt may be a suture between two late Archean continental terranes.

Hanson, G. N.; Krogstad, E. J.; Ragamani, V.; Balakrishnan, S.

363

Fall Protection Characteristics of Safety Belts and Human Impact Tolerance  

PubMed Central

Abstract: Many fatal accidents due to falls from heights have occurred at construction sites not only in Japan but also in other countries. This study aims to determine the fall prevention performance of two types of safety belts: a body belt1), which has been used for more than 40?yr in the Japanese construction industry as a general type of safety equipment for fall accident prevention, and a full harness2, 3), which has been used in many other countries. To determine human tolerance for impact trauma, this study discusses features of safety belts with reference4,5,6,7,8,9) to relevant studies in the medical science, automobile crash safety, and aircrew safety. For this purpose, simple drop tests were carried out in a virtual workplace to measure impact load, head acceleration, and posture in the experiments, the Hybrid-III pedestrian model10) was used as a human dummy. Hybrid-III is typically employed in official automobile crash tests (New Car Assessment Program: NCAP) and is currently recognized as a model that faithfully reproduces dynamic responses. Experimental results shows that safety performance strongly depends on both the variety of safety belts used and the shock absorbers attached onto lanyards. These findings indicate that fall prevention equipment, such as safety belts, lanyards, and shock absorbers, must be improved to reduce impact injuries to the human head and body during falls. PMID:25345426

HINO, Yasumichi; OHDO, Katsutoshi; TAKAHASHI, Hiroki

2014-01-01

364

Local Acceleration of Radiation Belt Electrons: Where? When? and How?  

NASA Astrophysics Data System (ADS)

Two broad classes of processes are capable of accelerating radiation belt electrons to ultra-relativistic energies: radial acceleration by inward diffusion from a high-altitude source population and local acceleration of an in situ source population by wave-particle interactions. Recently the Van Allen Probes mission provided unambiguous observations of local acceleration for one of the first radiation belt enhancement events of the mission on October 8-9, 2012 [Reeves et al., 2013]. Now, with over a year of Van Allen Probes observations, it is possible to conduct a larger survey of radiation belt enhancement events. Level 4 phase space densities recently been made available by the RBSP-ECT science operations center using data from the Magnetic Electron Ion Spectrometer (MagEIS) [Blake et al., 2013] and Van Allen Probes magnetic ephemeris files [Henderson et al., 2013]. In this presentation we survey the radial profiles of phase space density as a function of the magnetic invariants (mu, K, and L*) for characteristic signatures of local acceleration through wave particle interactions. We examine how many radiation belt enhancement events show signatures of local acceleration and determine where the peak acceleration occurred. We compare the observations with the expectations from theories of local acceleration in order to better understand the generation mechanisms and the relative roles of local acceleration and radial diffusion in controlling radiation belt dynamics.

Reeves, G. D.; Henderson, M. G.; Morley, S.; Larsen, B.; Friedel, R. H.; Claudepierre, S. G.; Fennell, J. F.; Blake, J. B.; Boyd, A. J.; Spence, H.; Kanekal, S. G.; Baker, D. N.; Skoug, R. M.; Funsten, H. O.

2013-12-01

365

Fall protection characteristics of safety belts and human impact tolerance.  

PubMed

Many fatal accidents due to falls from heights have occurred at construction sites not only in Japan but also in other countries. This study aims to determine the fall prevention performance of two types of safety belts: a body belt(1)), which has been used for more than 40?yr in the Japanese construction industry as a general type of safety equipment for fall accident prevention, and a full harness(2, 3)), which has been used in many other countries. To determine human tolerance for impact trauma, this study discusses features of safety belts with reference(4,5,6,7,8,9)) to relevant studies in the medical science, automobile crash safety, and aircrew safety. For this purpose, simple drop tests were carried out in a virtual workplace to measure impact load, head acceleration, and posture in the experiments, the Hybrid-III pedestrian model(10)) was used as a human dummy. Hybrid-III is typically employed in official automobile crash tests (New Car Assessment Program: NCAP) and is currently recognized as a model that faithfully reproduces dynamic responses. Experimental results shows that safety performance strongly depends on both the variety of safety belts used and the shock absorbers attached onto lanyards. These findings indicate that fall prevention equipment, such as safety belts, lanyards, and shock absorbers, must be improved to reduce impact injuries to the human head and body during falls. PMID:25345426

Hino, Yasumichi; Ohdo, Katsutoshi; Takahashi, Hiroki

2014-10-27

366

The binary Kuiper-belt object 1998 WW31.  

PubMed

The recent discovery of a binary asteroid during a spacecraft fly-by generated keen interest, because the orbital parameters of binaries can provide measures of the masses, and mutual eclipses could allow us to determine individual sizes and bulk densities. Several binary near-Earth, main-belt and Trojan asteroids have subsequently been discovered. The Kuiper belt-the region of space extending from Neptune (at 30 astronomical units) to well over 100 AU and believed to be the source of new short-period comets-has become a fascinating new window onto the formation of our Solar System since the first member object, not counting Pluto, was discovered in 1992 (ref. 13). Here we report that the Kuiper-belt object 1998 WW31 is binary with a highly eccentric orbit (eccentricity e approximately 0.8) and a long period (about 570 days), very different from the Pluto/Charon system, which was hitherto the only previously known binary in the Kuiper belt. Assuming a density in the range of 1 to 2 g cm-3, the albedo of the binary components is between 0.05 and 0.08, close to the value of 0.04 generally assumed for Kuiper-belt objects. PMID:11961547

Veillet, Christian; Parker, Joel Wm; Griffin, Ian; Marsden, Brian; Doressoundiram, Alain; Buie, Marc; Tholen, David J; Connelley, Michael; Holman, Matthew J

2002-04-18

367

The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids  

E-print Network

We have developed a model-independent analytical method for debiasing the four-dimensional (a,e,i,H) distribution obtained in any asteroid observation program and have applied the technique to results obtained with the 0.9m Spacewatch Telescope. From 1992 to 1995 Spacewatch observed ~3740 deg^2 near the ecliptic and made observations of more than 60,000 asteroids to a limiting magnitude of V~21. The debiased semi-major axis and inclination distributions of Main Belt asteroids in this sample with 11.5asteroids with H asteroids is complete to about absolute magnitudes 12.75, 12.25 and 11.25 in the inner, middle and outer regions of the belt respectively. The number distribution as a function of absolute magnitude cannot be represented by a single power-law (10^{alpha H}) in any region. We were able to define broad ranges in H in each part of the belt where alpha was nearly constant. Within these ranges of H the slope does not correspond to the value of 0.5 expected for an equilibrium cascade in self-similar collisions (Dohnanyi, 1971). The value of alpha varies with absolute magnitude and shows a `kink' in all regions of the belt for H~13. This absolute magnitude corresponds to a diameter ranging from about 8.5 to 12.5 km depending on the albedo or region of the belt.

R. Jedicke; T. S. Metcalfe

1998-01-05

368

JOVIAN EARLY BOMBARDMENT: PLANETESIMAL EROSION IN THE INNER ASTEROID BELT  

SciTech Connect

The asteroid belt is an open window on the history of the solar system, as it preserves records of both its formation process and its secular evolution. The progenitors of the present-day asteroids formed in the Solar Nebula almost contemporary to the giant planets. The actual process producing the first generation of asteroids is uncertain, strongly depending on the physical characteristics of the Solar Nebula, and the different scenarios produce very diverse initial size-frequency distributions (SFDs). In this work, we investigate the implications of the formation of Jupiter, plausibly the first giant planet to form, on the evolution of the primordial asteroid belt. The formation of Jupiter triggered a short but intense period of primordial bombardment, previously unaccounted for, which caused an early phase of enhanced collisional evolution in the asteroid belt. Our results indicate that this Jovian Early Bombardment caused the erosion or the disruption of bodies smaller than a threshold size, which strongly depends on the SFD of the primordial planetesimals. If the asteroid belt was dominated by planetesimals less than 100 km in diameter, the primordial bombardment would have caused the erosion of bodies smaller than 200 km in diameter. If the asteroid belt was instead dominated by larger planetesimals, the bombardment would have resulted in the destruction of bodies as big as 500 km.

Turrini, D.; Coradini, A.; Magni, G., E-mail: diego.turrini@ifsi-roma.inaf.it [Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via Fosso del Cavaliere 100, 00133, Rome (Italy)

2012-05-01

369

Structure of Possible Long-lived Asteroid Belts  

E-print Network

High resolution simulations are used to map out the detailed structure of two long-lived stable belts of asteroid orbits in the inner Solar system. The Vulcanoid belt extends from 0.09 to 0.20 astronomical units (au), though with a gaps at 0.15 and 0.18 au corresponding to de-stabilising mean motion resonances with Mercury and Venus. As collisional evolution proceeds slower at larger heliocentric distances, kilometre-sized or larger Vulcanoids are most likely to be found in the region between 0.16 and 0.18 au. The optimum location in which to search for Vulcanoids is at geocentric ecliptic longitudes roughly between 9 and 10 degrees. Dynamically speaking, the Earth-Mars belt between 1.08-1.28 au is an extremely stable repository for asteroids on nearly circular orbits. It is interrupted at 1.21 au due to the 3:4 commensurability with the Earth, while secular resonances with Saturn are troublesome beyond 1.17 au. These detailed maps of the fine structure of the belts can be used to plan search methodologies. Strategies for detecting members of the belts are discussed, including the use of infrared wide-field imaging with VISTA, and forthcoming European Space Agency satellite missions like GAIA and BepiColombo.

N. W. Evans; S. A. Tabachnik

2002-04-24

370

Seat belt use among overweight and obese adolescents.  

PubMed

Motor vehicle crashes are the leading cause of death for adolescents. Previous studies with adults found an association between weight status and decreased use of seat belts. Research has also found significantly higher morbidity and mortality rates in obese individuals who are involved in motor vehicle crashes. If these relationships hold true in obese adolescents they represent additional risk factors for complications from motor vehicle trauma. Given the prevalence of obesity in adolescents (17.4%) and the increased risk of harm associated with obese individuals involved in motor vehicle crashes, this study explored whether there was an association between obesity in adolescents and their use of seat belts. Initial investigation found that rarely/never wearing seat belts was significantly greater for African Americans (22.6%), 18 years of age or older (19.4%), lived with adults other than both parents (15.7%), and males (15.4%). Bivariate logistic regression analysis controlling for demographic variables found that there was no statistically significant difference between overweight and normal weight adolescents. However, obese students were 1.72 times as likely as normal weight students to never or rarely wear their seat belts when riding in a car as a passenger. In particular, obese females and obese students in the middle school age ranges were statistically significantly more likely than normal weight students to never or rarely wear their seat belts. PMID:21181247

Price, James H; Dake, Joseph A; Balls-Berry, Joyce E; Wielinski, Margaret

2011-08-01

371

23 CFR 1240.11 - Determination of State seat belt use rate for calendar years 1996 and 1997.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Determination of State seat belt use rate for calendar years 1996 and 1997. 1240...TRANSPORTATION GUIDELINES SAFETY INCENTIVE GRANTS FOR USE OF SEAT BELTS-ALLOCATIONS BASED ON SEAT BELT USE RATES Determination of Allocations §...

2011-04-01

372

23 CFR 1240.12 - Determination of State seat belt use rate for calendar year 1998 and beyond.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Determination of State seat belt use rate for calendar year 1998 and beyond. 1240...TRANSPORTATION GUIDELINES SAFETY INCENTIVE GRANTS FOR USE OF SEAT BELTS-ALLOCATIONS BASED ON SEAT BELT USE RATES Determination of Allocations §...

2010-04-01

373

23 CFR 1240.12 - Determination of State seat belt use rate for calendar year 1998 and beyond.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Determination of State seat belt use rate for calendar year 1998 and beyond. 1240...TRANSPORTATION GUIDELINES SAFETY INCENTIVE GRANTS FOR USE OF SEAT BELTS-ALLOCATIONS BASED ON SEAT BELT USE RATES Determination of Allocations §...

2011-04-01

374

Recent Developments in the Radiation Belt Environment Model  

NASA Technical Reports Server (NTRS)

The fluxes of energetic particles in the radiation belts are found to be strongly controlled by the solar wind conditions. In order to understand and predict the radiation particle intensities, we have developed a physics-based Radiation Belt Environment (RBE) model that considers the influences from the solar wind, ring current and plasmasphere. Recently, an improved calculation of wave-particle interactions has been incorporated. In particular, the model now includes cross diffusion in energy and pitch-angle. We find that the exclusion of cross diffusion could cause significant overestimation of electron flux enhancement during storm recovery. The RBE model is also connected to MHD fields so that the response of the radiation belts to fast variations in the global magnetosphere can be studied.Weare able to reproduce the rapid flux increase during a substorm dipolarization on 4 September 2008. The timing is much shorter than the time scale of wave associated acceleration.

Fok, M.-C.; Glocer, A.; Zheng, Q.; Horne, R. B.; Meredith, N. P.; Albert, J. M.; Nagai, T.

2010-01-01

375

A plan to clear energetic protons from the radiation belt  

NASA Astrophysics Data System (ADS)

The Earth's radiation belts have been a known hazard to satellites since at least 1962, when an American high-altitude nuclear weapons test named Starfish Prime produced an artificial belt that disabled the first commercial communications satellite, TelStar 1. In the years since the Cold War, thousands of satellites have been put into orbit, and surface charging, high-energy protons, high-energy electrons known as "killer electrons," and other hazards of the inner magnetosphere have continued to take their toll. Satellites can be hardened against these radiation hazards, but some researchers have recently floated a more radical idea: If specially designed transmitters are put into space and set to emit tightly tuned waves, known as electromagnetic ion cyclotron (EMIC) waves, they could potentially push the highly energetic protons out of the Earth's inner radiation belt, clearing the satellite's path.

Schultz, Colin

2013-11-01

376

The Living with a Star Radiation Belt Storm Probes  

NASA Technical Reports Server (NTRS)

The goal of NASA's Living With a Star Radiation Belt Storm Probe mission is to understand, ideally to the point of predictability, how populations of relativistic electrons and ions in space form or change in response to the variable inputs of energy from the Sun. The investigations selected for this 2-spacecraft mission scheduled for launch in early 2012 address this task by making extensive observations of the plasma waves, thermal, ring current, and relativistic particle populations, and DC electric and magnetic fields within the Earth's inner and outer radiation belts. We first describe the current mission concept within the scope of NASA's strategic plan and the Vision for Exploration, and then consider how its observations will be used to define and quantify the processes that accelerate, transport, and remove particles in the Earth's radiation belts.

Sibeck, D. G.; Mauk, B. H.; Grebowsky, J. M.; Fox, N. J.

2007-01-01

377

Radiation Belt Environment Model: Application to Space Weather and Beyond  

NASA Technical Reports Server (NTRS)

Understanding the dynamics and variability of the radiation belts are of great scientific and space weather significance. A physics-based Radiation Belt Environment (RBE) model has been developed to simulate and predict the radiation particle intensities. The RBE model considers the influences from the solar wind, ring current and plasmasphere. It takes into account the particle drift in realistic, time-varying magnetic and electric field, and includes diffusive effects of wave-particle interactions with various wave modes in the magnetosphere. The RBE model has been used to perform event studies and real-time prediction of energetic electron fluxes. In this talk, we will describe the RBE model equation, inputs and capabilities. Recent advancement in space weather application and artificial radiation belt study will be discussed as well.

Fok, Mei-Ching H.

2011-01-01

378

An anomalous basaltic meteorite from the innermost main belt.  

PubMed

Triangulated observations of fireballs allow us to determine orbits and fall positions for meteorites. The great majority of basaltic meteorites are derived from the asteroid 4 Vesta. We report on a recent fall that has orbital properties and an oxygen isotope composition that suggest a distinct parent body. Although its orbit was almost entirely contained within Earth's orbit, modeling indicates that it originated from the innermost main belt. Because the meteorite parent body would likely be classified as a V-type asteroid, V-type precursors for basaltic meteorites unrelated to Vesta may reside in the inner main belt. This starting location is in agreement with predictions of a planetesimal evolution model that postulates the formation of differentiated asteroids in the terrestrial planet region, with surviving fragments concentrated in the innermost main belt. PMID:19762639

Bland, Philip A; Spurny, Pavel; Towner, Martin C; Bevan, Alex W R; Singleton, Andrew T; Bottke, William F; Greenwood, Richard C; Chesley, Steven R; Shrbeny, Lukas; Borovicka, Jiri; Ceplecha, Zdenek; McClafferty, Terence P; Vaughan, David; Benedix, Gretchen K; Deacon, Geoff; Howard, Kieren T; Franchi, Ian A; Hough, Robert M

2009-09-18

379

Dynamical Effects from Asteroid Belts for Planetary Systems  

E-print Network

The orbital evolution and stability of planetary systems with interaction from the belts is studied using the standard phase-plane analysis. In addition to the fixed point which corresponds to the Keplerian orbit, there are other fixed points around the inner and outer edges of the belt. Our results show that for the planets, the probability to move stably around the inner edge is larger than the one to move around the outer edge. It is also interesting that there is a limit cycle of semi-attractor for a particular case. Applying our results to the Solar System, we find that our results could provide a natural mechanism to do the orbit rearrangement for the larger Kuiper Belt Objects and thus successfully explain the absence of these objects beyond 50 AU.

Ing-Guey Jiang; Li-Chin Yeh

2003-09-08

380

Response of radiation belt simulations to different radial diffusion coefficients  

NASA Astrophysics Data System (ADS)

Resonant interactions between Ultra Low Frequency (ULF) waves and relativistic electrons may violate the third adiabatic invariant of motion, which produces radial diffusion in the electron radiation belts. This process plays an important role in the formation and structure of the outer electron radiation belt and is important for electron acceleration and losses in that region. Two parameterizations of the resonant wave-particle interaction of electrons with ULF waves in the magnetosphere by Brautigam and Albert [2000] and Ozeke et al. [2012] are evaluated using the Versatile Electron Radiation Belt (VERB) diffusion code to estimate their relative effect on the radiation belt simulation. The period of investigation includes quiet time and storm time geomagnetic activity and is compared to data based on satellite observations. Our calculations take into account wave-particle interactions represented by radial diffusion transport, local acceleration, losses due to pitch-angle diffusion, and mixed diffusion. We show that the results of the 3D diffusion simulations depend on the assumed parametrization of waves. The differences between the simulations and potential missing physical mechanisms are discussed. References Brautigam, D. H., and J. M. Albert (2000), Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm, J. Geophys. Res., 105(A1), 291-309, doi:10.1029/1999JA900344 Ozeke, L. G., I. R. Mann, K. R. Murphy, I. J. Rae, D. K. Milling, S. R. Elkington, A. A. Chan, and H. J. Singer (2012), ULF wave derived radiation belt radial diffusion coefficients, J. Geophys. Res., 117, A04222, doi:10.1029/2011JA017463.

Drozdov, A.; Shprits, Y.; Subbotin, D.; Kellerman, A. C.

2013-12-01

381

Searching for Chips of Kuiper Belt Objects in Meteorites  

NASA Technical Reports Server (NTRS)

The Nice model [1&2] describes a scenario whereby the Jovian planets experienced a violent reshuffling event approx.3:9 Ga the giant planets moved, existing small body reservoirs were depleted or eliminated, and new reservoirs were created in particular locations. The Nice model quantitatively explains the orbits of the Jovian planets and Neptune [1], the orbits of bodies in several different small body reservoirs in the outer solar system (e.g., Trojans of Jupiter [2], the Kuiper belt and scattered disk [3], the irregular satellites of the giant planets [4], and the late heavy bombardment on the terrestrial planets approx.3:9 Ga [5]. This model is unique in plausibly explaining all of these phenomena. One issue with the Nice model is that it predicts that transported Kuiper Belt Objects (KBOs) (things looking like D class asteroids) should predominate in the outer asteroid belt, but we know only about 10% of the objects in the outer main asteroid belt appear to be D-class objects [6]. However based upon collisional modeling, Bottke et al. [6] argue that more than 90% of the objects captured in the outer main belt could have been eliminated by impacts if they had been weakly-indurated objects. These disrupted objects should have left behind pieces in the ancient regoliths of other, presumably stronger asteroids. Thus, a derived prediction of the Nice model is that ancient regolith samples (regolith-bearing meteorites) should contain fragments of collisionally-destroyed Kuiper belt objects. In fact KBO pieces might be expected to be present in most ancient regolith- bearing meteorites [7&8].

Zolensky, M. E.; Ohsumi, K.; Briani, G.; Gounelle, M.; Mikouchi, T.; Satake, W.; Kurihara, T.; Weisberg, M. K.; Le, L.

2009-01-01

382

Kinematics of thrust belt development in the external Dinarides, Croatia  

NASA Astrophysics Data System (ADS)

Many compressional orogenic systems include foreland fold-and-thrust belts, but the relationship between foreland thrust belt kinematics and hinterland crustal thickening, and their dependence on numerous additional factors such as variable accretionary flux, fault friction, surface processes, crustal flow, and pre-existing structure remains controversial. The Dinaric orogen may provide an important opportunity to isolate the relative importance of some of these factors. The external Dinarides are composed primarily of carbonate strata. Their insensitivity to climatic variability may potentially mitigate this important source of uncertainty relative to many other fold and thrust belts. As a first step toward understanding the kinematics of the external Dinarides, we measured present-day crustal velocity along a N13°E profile across the southern Adria microplate and external Dinarides collision zone. We used these data to develop an elastic dislocation model representing contemporary fold and thrust belt kinematics and decollement geometry. At the latitude of the Dalmatian Islands, the model fault plane reaches the surface some 80~km seaward of mapped SW-verging thrusts of Eocene and perhaps Neogene age along the coastal areas, consistent with SW-migrating deformation in an active fold and thrust belt. South of the Dalmatian Islands, however, the modern deformation front appears to be located within about 1~km of the older mapped faults. The largest known earthquakes in the system (~M7) are associated with this southern stationary-width part of the system. Possible explanations for along-strike variability in thrust belt kinematics include along-strike changes in decollement friction, clastic sediment availability and drainage network connectivity, accretionary flux associated with variable Adria carbonate platform thickness, retroarc exhumation, and subaerial distribution of pro-wedge carbonates.

Bennett, R. A.; Hreinsdottir, S.; Buble, G.; Fay, N. P.; Casale, G.; Gendaszek, A.; Cowan, D.; Basic, T.; Bacic, Z.; Marjanovic, M.

2007-12-01

383

Early Proterozoic transcontinental orogenic belts in the United States  

SciTech Connect

It has been recognized for many years that Early Proterozoic orogenic rocks in the western US range from 1.8 to 1.6 Ga, with a general distribution such that 1.8 to 1.7 Ga rocks underlie Colorado, northern Arizona, and northern New Mexico and 1.7 to 1.6 Ga rocks underlie southern Arizona and southern New Mexico. Recent U-Pb geochronologic and Sm-Nd isotopic studies by a variety of research groups have refined crustal history in the western region and have extended knowledge eastward into the buried midcontinent basement. As a result, the authors propose that 1.8 Ga to 1.6 Ga crust of the US by divided into two distinct, but overlapping, orogenic belts: a 1.8 to 1.7 Ga Inner Accretionary Belt and a 1.7 to 1.6 Ga Outer Tectonic Belt. The Inner Accretionary Belt (IAB) comprises rock suites with compositions and isotopic signatures compatible with origin as juvenile crustal terranes formed as oceanic or off-shore and related terranes that were accreted to southern Laurentia between 1.8 and 1.6 Ga. The IAB includes the Yavapai Province of Arizona, Early Proterozoic basement of Colorado and southern Wyoming, and the basement of Nebraska. The Mojave Province of California may be part of this belt, although it also includes components derived from older Proterozoic or Archean crust. Extension of the IAB eastward from Nebraska is uncertain at present, although coeval rocks that may be eastern manifestations of this 1.8 to 1.7 Ga orogenesis occur in Wisconsin (1.76 Ga granite-rhyolite suite), Ontario (Killarney granite), Labrador (Makkovic Province) and southern Greenland (Ketilidian orogen). The Outer Tectonic Belt (OTB) comprises rock suites which have compositions, structures, and isotopic signature compatible with origin in continental margin tectonic settings between 1.7 and 1.6 Ga.

Van Schmus, W.R. (Univ. of Kansas, Lawrence, KS (United States). Dept. of Geology); Bickford, M.E. (Syracuse Univ., NY (United States). Dept. of Geology); Condie, K.C. (New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. Geoscience)

1993-02-01

384

The Belt voice: Acoustical measurements and esthetic correlates  

NASA Astrophysics Data System (ADS)

This dissertation explores the esthetic attributes of the Belt voice through spectral acoustical analysis. The process of understanding the nature and safe practice of Belt is just beginning, whereas the understanding of classical singing is well established. The unique nature of the Belt sound provides difficulties for voice teachers attempting to evaluate the quality and appropriateness of a particular sound or performance. This study attempts to provide answers to the question "does Belt conform to a set of measurable esthetic standards?" In answering this question, this paper expands on a previous study of the esthetic attributes of the classical baritone voice (see "Vocal Beauty", NATS Journal 51,1) which also drew some tentative conclusions about the Belt voice but which had an inadequate sample pool of subjects from which to draw. Further, this study demonstrates that it is possible to scientifically investigate the realm of musical esthetics in the singing voice. It is possible to go beyond the "a trained voice compared to an untrained voice" paradigm when evaluating quantitative vocal parameters and actually investigate what truly beautiful voices do. There are functions of sound energy (measured in dB) transference which may affect the nervous system in predictable ways and which can be measured and associated with esthetics. This study does not show consistency in measurements for absolute beauty (taste) even among belt teachers and researchers but does show some markers with varying degrees of importance which may point to a difference between our cognitive learned response to singing and our emotional, more visceral response to sounds. The markers which are significant in determining vocal beauty are: (1) Vibrancy-Characteristics of vibrato including speed, width, and consistency (low variability). (2) Spectral makeup-Ratio of partial strength above the fundamental to the fundamental. (3) Activity of the voice-The quantity of energy being produced. (4) Consistency of the voice-How low is the variability in the energy patterns of the voice.

Bounous, Barry Urban

385

"Nonempty" Gap Between Radiation Belts: The First Observations  

NASA Astrophysics Data System (ADS)

The first space experiments carried out in 1958 by the scientific groups of James Van Allen (United States) on board the first Explorer satellites and Sergey Vernov (Soviet Union) on board the satellite Sputnik 3 led to the discovery of the Earth's radiation belts—the particles (mainly protons and electrons) captured by the magnetic field of the Earth. Two scientific groups independently came to the conclusion that the electrons in the geomagnetic trapping region fill two areas, inner and outer radiation belts, unlike the protons, which fill the whole trapping region [see, e.g., Lemaire, 2000].

Panasyuk, Mikhail

2013-12-01

386

Structural evolution of the Kolar Schist Belt, South India  

NASA Astrophysics Data System (ADS)

The structural evolution of the Kolar Schist Belt was discussed. Evidence was described from structures in the ferrigenous quartzite within the schist belt for two periods of nearly coaxial isoclinal folding attributable to E-W compression. This folding was followed by collapse of the F sub 1/F sub 2 folds, forming open F sub 3 folds with NNE-SSW axes. Finally, a period of N-S shortening caused a broad warping of the earlier N-S trending fold axes. There is evidence within the gneisses for shearing produced by similar, nearly E-W compression.

Mukhopahyay, Dilip K.

387

Structural evolution of the Kolar Schist Belt, South India  

NASA Technical Reports Server (NTRS)

The structural evolution of the Kolar Schist Belt was discussed. Evidence was described from structures in the ferrigenous quartzite within the schist belt for two periods of nearly coaxial isoclinal folding attributable to E-W compression. This folding was followed by collapse of the F sub 1/F sub 2 folds, forming open F sub 3 folds with NNE-SSW axes. Finally, a period of N-S shortening caused a broad warping of the earlier N-S trending fold axes. There is evidence within the gneisses for shearing produced by similar, nearly E-W compression.

Mukhopahyay, Dilip K.

1988-01-01

388

Zodiacal emission. III - Dust near the asteroid belt  

NASA Technical Reports Server (NTRS)

Properties of the zodiacal dust bands are derived from fits to Infrared Astronomical Satellite profiles of the ecliptic. Three observations lead to the conclusion that the dust-band material is spread over a range of heliocentric distances between the asteroid belt and the sun: parallax, color temperature, and wavelength dependence of the band latitudes. The orientations of the midplanes of the bands are found to be typical of asteroids. A model of 'migrating bands', wherein dust is produced near the asteroid belt and spirals into the sun under the influence of Poynting-Robertson drag, is used to explain the range of heliocentric distances of dust-band material.

Reach, William T.

1992-01-01

389

A Spectroscopically Unique Main Belt Asteroid: 10537 (1991 RY16)  

E-print Network

We present visible and near-infrared reflectance spectra and interpreted surface mineralogy for asteroid 10537 (1991 RY16). The spectrum of this object is without precedent amongst the Main Belt asteroids. A unique absorption band centered at 0.63 microns could be attributed to one of several mineralogies. Pronounced 1- and 2-micron absorption bands suggest that the composition of 10537 is a mixture of pyroxenes and olivine and that it originated from a parent body that was partially or fully differentiated. The closest available analog is the large Main Belt asteroid 349 Dembowska but 10537 may be an isolated fragment from a completely eroded parent body.

Nicholas A. Moskovitz; Samuel Lawrence; Robert Jedicke; Mark Willman; Nader Haghighipour; Schelte J. Bus; Eric Gaidos

2008-06-13

390

Structure of Possible Long-lived Asteroid Belts  

Microsoft Academic Search

High resolution simulations are used to map out the detailed structure of two\\u000along-lived stable belts of asteroid orbits in the inner Solar system. The\\u000aVulcanoid belt extends from 0.09 to 0.20 astronomical units (au), though with a\\u000agaps at 0.15 and 0.18 au corresponding to de-stabilising mean motion resonances\\u000awith Mercury and Venus. As collisional evolution proceeds slower at

N. W. Evans; S. A. Tabachnik

2002-01-01

391

14 CFR 121.317 - Passenger information requirements, smoking prohibitions, and additional seat belt requirements.  

Code of Federal Regulations, 2011 CFR

... Passenger information requirements, smoking prohibitions, and additional seat belt... Passenger information requirements, smoking prohibitions, and additional seat belt...operate an airplane on a flight on which smoking is prohibited by part 252 of this...

2011-01-01

392

14 CFR 121.317 - Passenger information requirements, smoking prohibitions, and additional seat belt requirements.  

... Passenger information requirements, smoking prohibitions, and additional seat belt... Passenger information requirements, smoking prohibitions, and additional seat belt...operate an airplane on a flight on which smoking is prohibited by part 252 of this...

2014-01-01

393

14 CFR 121.317 - Passenger information requirements, smoking prohibitions, and additional seat belt requirements.  

Code of Federal Regulations, 2010 CFR

... Passenger information requirements, smoking prohibitions, and additional seat belt... Passenger information requirements, smoking prohibitions, and additional seat belt...operate an airplane on a flight on which smoking is prohibited by part 252 of this...

2010-01-01

394

14 CFR 121.317 - Passenger information requirements, smoking prohibitions, and additional seat belt requirements.  

Code of Federal Regulations, 2013 CFR

... Passenger information requirements, smoking prohibitions, and additional seat belt... Passenger information requirements, smoking prohibitions, and additional seat belt...operate an airplane on a flight on which smoking is prohibited by part 252 of this...

2013-01-01

395

14 CFR 121.317 - Passenger information requirements, smoking prohibitions, and additional seat belt requirements.  

Code of Federal Regulations, 2012 CFR

... Passenger information requirements, smoking prohibitions, and additional seat belt... Passenger information requirements, smoking prohibitions, and additional seat belt...operate an airplane on a flight on which smoking is prohibited by part 252 of this...

2012-01-01

396

Geophys. Res. Lett., 17, 3265, 1998. The Global Response of Relativistic Radiation Belt  

E-print Network

Geophys. Res. Lett., 17, 3265, 1998. 1 The Global Response of Relativistic Radiation Belt Electrons., The Global Response of Relativistic Radiation Belt Electrons, Geophys. Res. Lett., 17, 3265, 1998. 2

Reeves, Geoffrey D.

397

30 CFR 75.1101-10 - Water sprinkler systems; fire warning devices at belt drives.  

...2014-07-01 false Water sprinkler systems; fire warning devices at belt drives. 75...SAFETY STANDARDS-UNDERGROUND COAL MINES Fire Protection § 75.1101-10 Water sprinkler systems; fire warning devices at belt drives....

2014-07-01

398

14 CFR 135.128 - Use of safety belts and child restraint systems.  

Code of Federal Regulations, 2012 CFR

14 Aeronautics and Space 3 2012-01-01 2012-01-01...false Use of safety belts and child restraint systems. 135...135.128 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION...128 Use of safety belts and child restraint...

2012-01-01

399

14 CFR 135.128 - Use of safety belts and child restraint systems.  

Code of Federal Regulations, 2010 CFR

14 Aeronautics and Space 3 2010-01-01 2010-01-01...false Use of safety belts and child restraint systems. 135...135.128 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION...128 Use of safety belts and child restraint...

2010-01-01

400

14 CFR 135.128 - Use of safety belts and child restraint systems.  

Code of Federal Regulations, 2013 CFR

14 Aeronautics and Space 3 2013-01-01 2013-01-01...false Use of safety belts and child restraint systems. 135...135.128 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION...128 Use of safety belts and child restraint...

2013-01-01

401

14 CFR 135.128 - Use of safety belts and child restraint systems.  

14 Aeronautics and Space 3 2014-01-01 2014-01-01...false Use of safety belts and child restraint systems. 135...135.128 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION...128 Use of safety belts and child restraint...

2014-01-01

402

14 CFR 135.128 - Use of safety belts and child restraint systems.  

Code of Federal Regulations, 2011 CFR

14 Aeronautics and Space 3 2011-01-01 2011-01-01...false Use of safety belts and child restraint systems. 135...135.128 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION...128 Use of safety belts and child restraint...

2011-01-01

403

The recent breakup of an asteroid in the main-belt region  

E-print Network

............................................................................................................................................................................. The present population of asteroids in the main belt is largely the result of many past collisions1 tens of major collisions (that is, asteroid families) have been observed in the main belt9.............................................................. The recent breakup of an asteroid

Nesvorny, David

404

The effect of polyesterurethane belt surface roughness on Listeria monocytogenes biofilm formation and its cleaning efficiency  

Microsoft Academic Search

Contamination of surfaces in direct contact with food in the processing line is the major cause of finished product cross-contamination, especially conveyor belt surfaces that transfer food products. Polyesterurethane (PSU) is one of the materials widely used in conveyor belt systems; therefore, the objective of this study was to examine the effect of PSU conveyor belt surface roughness on the

Yuphakhun Chaturongkasumrit; Hajime Takahashi; Suwimon Keeratipibul; Takashi Kuda; Bon Kimura

2011-01-01

405

14 CFR 25.785 - Seats, berths, safety belts, and harnesses.  

...structure, and each safety belt or harness and...the occupant, seat, safety belt, and harness for...by assuming that the critical load in the forward...need not be applied to safety belts for berths. ...must have a restraint system consisting of a...

2014-01-01

406

Observations of the transport through the belt sea and an investigation of the momentum balance  

Microsoft Academic Search

The Fehmarn Belt is a main channel in the Belt Sea and plays an important role in the exchange of water between the Baltic Sea and the North Sea. This article deals with the discharge through the Fehmarn Belt. Data given by seven stations measuring water level, salinity, temperature, wind speed and direction, and currents over the period 15 October

Flemming Jakobsen; Christophe Trébuchet

2000-01-01

407

Long-Term Benefits of Prompts to Use Safety Belts among Drivers Exiting Senior Communities  

ERIC Educational Resources Information Center

Senior drivers are vulnerable to automobile crashes and subsequent injury and death. Safety belts reduce health risks associated with auto crashes. Therefore, it is important to encourage senior drivers to wear safety belts while driving. Using a repeated baseline design (AAB), we previously reported that motivating signs boosted safety belt usage…

Cox, Cory D.; Cox, Brian S.; Cox, Daniel J.

2005-01-01

408

23 CFR Appendix D to Part 1240 - Determination of National Average Seat Belt Use Rate  

Code of Federal Regulations, 2010 CFR

... Determination of National Average Seat Belt Use Rate D Appendix D to Part 1240 Highways...TRANSPORTATION GUIDELINES SAFETY INCENTIVE GRANTS FOR USE OF SEAT BELTS-ALLOCATIONS BASED ON SEAT BELT USE RATES Pt. 1240, App. D Appendix D to...

2010-04-01

409

The New Horizons Mission to Pluto, the Kuiper Belt, and Beyond  

E-print Network

: KBOs at 40+ AU `Kuiper Belts' surrounding stars in Orion, B Pictoris #12;2006:Team using HST discoversThe New Horizons Mission to Pluto, the Kuiper Belt, and Beyond Henry Throop Sr. Research Scientist system #12;1995: Detection of Kuiper Belt Objects (KBOs) show that Pluto is just the first of many... Red

Throop, Henry

410

Uranium deposits of The Grants, New Mexico mineral belt. [Geology, geochronology, clay mineralogy, trace element analysis  

Microsoft Academic Search

The Grants mineral belt forms a SE-trending linear belt of U deposits at the southern margin of the San Juan basin. The following geologic studies of the belt were made: stratigraphy, structures, tectonic history, ore deposits and their mineralogy, authigenic minerals, detrital minerals, clay minerals, geochronology, etc. Trace element analyses were carried out, including the U content of rocks. 13

Brookins

1975-01-01

411

Assessment of the static fit of automobile lap-belt systems on front-seat passengers  

Microsoft Academic Search

While automobile seat belts are recognized as reducing injury in frontal collisions, the lap belt can cause injury to the abdominal contents during impact. A lap belt which is malpositioned, i.e., above the anterior superior iliac spines (ASIS) of the pelvis before impact, is suggested as a causative factor in many of these injuries. A questionnaire was completed by 198

R. P. WELLS; R. W. NORMAN; P. BISHOP; D. A. RANNEY

1986-01-01

412

Radiation Belt Activity Indices and Solar Proton Event Alarm on the CRATERRE Project Web Site  

E-print Network

Radiation Belt Activity Indices and Solar Proton Event Alarm on the CRATERRE Project Web Site D--Two Radiation Belt Activity Indices, based on electron flux measurement >300 keV and >1.6 MeV, and one Solar updated. Index Terms- CRATERRE project, Radiation belts activity, Space environment I. INTRODUCTION

413

Effect of the belt grinding on the surface texture: Modeling of the contact and abrasive wear  

Microsoft Academic Search

Belt grinding is a finishing manufacturing process, which usually follows a hard turning operation. Experimental investigations show that the belt grinding process improves the surface texture and leads to compressive residual stresses.To study the contact between the belt constituted by abrasive grains and the surface, in particular to understand the physical of abrasion, a three-dimensional numerical model is established and

A. Jourani; M. Dursapt; H. Hamdi; J. Rech; H. Zahouani

2005-01-01

414

Plate tectonic model for the Carboniferous evolution of the New England Fold Belt  

Microsoft Academic Search

The New England Fold Belt forms the easternmost, youngest part of the Tasman Fold Belt System. For much of Late Palaeozoic time, it was a convergent plate margin at the edge of the Australian continent. At present, the New England Fold Belt is separated into the Yarrol Province in the north and the New England Province in the south by

C. G. Murray; C. L. Fergusson; P. G. Flood; W. G. Whitaker; R. J. Korsch

1987-01-01

415

At several localities around the world, thrust belts have developed on both sides of  

E-print Network

that the bivergence of thrusting in island arcs can develop without reversal of subduction polarity, without subarc1522 ABSTRACT At several localities around the world, thrust belts have developed on both sides). In these localities, the overall vergence of the backarc thrust belt is opposite to that of the forearc thrust belt

ten Brink, Uri S.

416

Linking the collisional history of the main asteroid belt to itsdynamical excitation and depletion  

Microsoft Academic Search

The main belt is believed to have originally contained an Earth mass or more of material, enough to allow the asteroids to accrete on relatively short timescales. The present-day main belt, however, only contains ˜5×10 Earth masses. Numerical simulations suggest that this mass loss can be explained by the dynamical depletion of main belt material via gravitational perturbations from planetary

William F. Bottke; Daniel D. Durda; D. Nesvorn'y; Robert Jedicke; Alessandro Morbidelli; D. Vokrouhlick'y; Harold F. Levison

2005-01-01

417

EVIDENCE FOR A COLOR DEPENDENCE IN THE SIZE DISTRIBUTION OF MAIN-BELT ASTEROIDS Paul Wiegert  

E-print Network

EVIDENCE FOR A COLOR DEPENDENCE IN THE SIZE DISTRIBUTION OF MAIN-BELT ASTEROIDS Paul Wiegert ($1 km) main-belt asteroids with the 3.6 m Canada-France-Hawaii Telescope. We observed in two filters in the middle and outer belt, but the CSD of those asteroids seen in the r0 filter is consistently

Wiegert, Paul

418

A spectroscopic comparison of HED meteorites and V-type asteroids in the inner Main Belt  

E-print Network

A spectroscopic comparison of HED meteorites and V-type asteroids in the inner Main Belt Nicholas A Asteroids, Composition Asteroid Vesta Meteorites a b s t r a c t V-type asteroids in the inner Main Belt (a causes of this offset are discussed. Amongst these inner Main Belt asteroids we do not find evidence

Moskovitz, Nicholas

419

LETTER doi:10.1038/nature09456 A recent disruption of the main-belt asteroid  

E-print Network

LETTER doi:10.1038/nature09456 A recent disruption of the main-belt asteroid P/2010 A2 David Jewitt report observations of P/2010A2, a previously unknown inner-belt asteroid with a peculiar, comet elements, however, are those of a main-belt asteroid (semimajor axis a 5 2.290 astronomical units (AU

Jewitt, David C.

420

An agecolour relationship for main-belt S-complex asteroids  

E-print Network

............................................................................................................................................................................. Asteroid collisions in the main belt eject fragments that may eventually land on Earth as meteorites1 of the rate of space weathering on S-complex main-belt asteroids using a relation- ship between the ages of space weathering on main-belt asteroids (Fig. 1). Our method uses asteroid families that are genetically

Nesvorny, David

421

Exploring the asteroid belt with ion propulsion: Dawn mission history, status and plans  

E-print Network

Exploring the asteroid belt with ion propulsion: Dawn mission history, status and plans C Vesta, the second most massive asteroid in the main belt, and to 1 Ceres, the most massive. The third- hood of the present asteroid belt the process was cut short by the gravitational stirring of the gas

Zuber, Maria

422

Reducing Asteroid Belt Correlated Noise from Earth–Mars Ranging Data  

Microsoft Academic Search

To aid the more complete and precise utilization of Earth–Mars radar range data, filtering techniques are developed which reduce the effects of asteroid belt correlated noise, which now degrades such data. Because of the dynamical regularities in asteroid belt motion, there is a corresponding regularity in the belt's total perturbation of a planet's orbit. A correlated structure for this disturbance

Kenneth Nordtvedt

1997-01-01

423

Radiation belt electron precipitation by man-made VLF transmissions  

Microsoft Academic Search

Enhancements of drift-loss cone fluxes in the inner radiation belt have been observed to coincide with the geographic location of the powerful VLF transmitter NWC. In this paper we expand upon the earlier study to examine the occurrence frequency of drift-loss cone enhancements observed above transmitters and the intensity of the flux enhancements and to demonstrate the linkage to transmitter

Rory J. Gamble; Craig J. Rodger; Mark A. Clilverd; Jean-André Sauvaud; Neil R. Thomson; S. L. Stewart; Robert J. McCormick; Michel Parrot; Jean-Jacques Berthelier

2008-01-01

424

Shape, size and multiplicity of main-belt asteroids  

Microsoft Academic Search

This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (?5% of the primary

F. Marchis; M. Kaasalainen; E. F. Y. Hom; J. Berthier; J. Enriquez; D. Hestroffer; D. Le Mignant; I. de Pater

2006-01-01

425

Accretion in the Early Kuiper Belt II. Fragmentation  

E-print Network

We describe new planetesimal accretion calculations in the Kuiper Belt that include fragmentation and velocity evolution. All models produce two power law cumulative size distributions, N_C propto r^{-q}, with q = 2.5 for radii less than 0.3-3 km and q = 3 for radii exceeding 1-3 km. The power law indices are nearly independent of the initial mass in the annulus, the initial eccentricity of the planetesimal swarm, and the initial size distribution of the planetesimal swarm. The transition between the two power laws moves to larger radii as the initial eccentricity increases. The maximum size of objects depends on their intrinsic tensile strength; Pluto formation requires a strength exceeding 300 erg per gram. Our models yield formation timescales for Pluto-sized objects of 30-40 Myr for a minimum mass solar nebula. The production of several `Plutos' and more than 10^5 50 km radius Kuiper Belt objects leaves most of the initial mass in 0.1-10 km radius objects that can be collisionally depleted over the age of the solar system. These results resolve the puzzle of large Kuiper Belt objects in a small mass Kuiper Belt.

Scott J. Kenyon; Jane X. Luu

1999-04-09

426

Radiation Belt Storm Probes (RBSP) Payload Safety Introduction Briefing  

NASA Technical Reports Server (NTRS)

Mission of the Geospace Radiation Belt Storm Probes (RBSP) is: Gain s cientific understanding (to the point of predictability) of how populations of relativistic electrons and ions in space form or change in response to changes in solar activity and the solar wind.

Loftin, Chuck; Lampert, Dianna; Herrburger, Eric; Smith, Clay; Hill, Stuart; VonMehlem, Judi

2008-01-01

427