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Sample records for early archaean granite-greenstone

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

    PubMed

    Krüner, A; Byerly, G R; Lowe, D R

    1991-04-01

    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.

  2. 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)

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

    1991-01-01

    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.

  3. Crustal structure of the Archaean granite-greenstone terrane in the northern portion of the Kaapvaal Craton

    NASA Technical Reports Server (NTRS)

    Debeer, J. H.; Stettler, E. H.; Barton, J. M., Jr.; Vanreenen, D. D.; Bearncombe, J. R.

    1986-01-01

    Recent investigations of the electrical resistivity, gravity and aeromagnetic signatures of the various granite-greenstone units in the northern portion of the Kaapvaal craton have revealed three features of significance: (1) the Archean greenstone belts are shallow features, rarely exceeding 5 km in depth; (2) the high resistivity upper crustal layer typical of the lower grade granite-greenstone terranes is absent in the granulite facies terrane; and (3) the aeromagnetic lineation patterns allow the granite-greenstone terrane to be subdivided into geologically recognizable tectono-metamorphic domains on the basis of lineation frequency and direction. A discussion follows.

  4. Extension of the Archaean Madibe-Kraaipan granite-greenstone terrane in southeast Botswana: Constraints from gravity and magnetic data

    NASA Astrophysics Data System (ADS)

    Ramotoroko, Calistus D.; Ranganai, Rubeni T.; Nyabeze, Peter

    2016-11-01

    The main goal of this study is to use suitably processed potential field data between longitude 24°E to 26°E and latitude 25°S to 26.5°S to gain a better geological and structural understanding of the extension of the Madibe-Kraaipan granite-greenstone terrane in southeast Botswana. Specifically, 150 new gravity measurements at 2-4 km intervals are reduced and later merged with existing gravity data in Botswana and South Africa for an integrated crustal interpretation with regional aeromagnetic data. Gravity and aeromagnetic anomalies of the region present partly coincident medium to high amplitude regions alternating with low zones. Analysis of the data revealed the existence of relatively narrow Nsbnd S trending rocks of dense and high magnetic intensity extending to the village of Mmathethe, corresponding to the northern extent of the Kraaipan greenstone belt. Much of the north-central area forms a broad magnetic low and gravity high implying Kraaipan metavolcanic rocks are more extensively developed in this area than previously recognized, under a blanket of Kalahari sediments that are ∼55 m thick as indicated by borehole data. The whole area lies within an ENE-trending Pre-Transvaal dyke swarm visible on the regional aeromagnetic data and much clearer on (proprietary) high resolution aeromagnetic data. The derivative and analytic signal techniques applied for both gravity and magnetic data spatially map the greenstone belt and multiple granite plutons very well. Depth estimates obtained by the 3D Euler method in combination with two-dimensional power spectrum technique locate the high magnetic intensity horizon at around 4.0 km. The depths were further confirmed by gravity model results along two profiles across the granite-greenstone terrane in Botswana and South Africa in a W-E direction. The models show generally steep-sided bodies of comparable width with a maximum depth extent of 4.7 km for the greenstones and 4.4 km for the younger plutons. The

  5. Archaean greenstone belts and associated granitic rocks - A review

    NASA Astrophysics Data System (ADS)

    Anhaeusser, Carl R.

    2014-12-01

    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

  6. The transition from an Archean granite-greenstone terrain into a charnockite terrain in southern India

    NASA Technical Reports Server (NTRS)

    Condie, K. C.; Allen, P.

    1983-01-01

    In southern India, it is possible to study the transition from an Archean granite-greenstone terrain (the Karnataka province) into high grade charnockites. The transition occurs over an outcrop width of 20-35 km and appears to represent burial depths ranging from 15 to 20 km. Field and geochemical studies indicate that the charnockites developed at the expense of tonalites, granites, and greenstones. South of the transition zone, geobarometer studies indicate burial depths of 7-9 kb.

  7. Growth of early continental crust by partial melting of eclogite.

    PubMed

    Rapp, Robert P; Shimizu, Nobumichi; Norman, Marc D

    2003-10-09

    The tectonic setting in which the first continental crust formed, and the extent to which modern processes of arc magmatism at convergent plate margins were operative on the early Earth, are matters of debate. Geochemical studies have shown that felsic rocks in both Archaean high-grade metamorphic ('grey gneiss') and low-grade granite-greenstone terranes are comprised dominantly of sodium-rich granitoids of the tonalite-trondhjemite-granodiorite (TTG) suite of rocks. Here we present direct experimental evidence showing that partial melting of hydrous basalt in the eclogite facies produces granitoid liquids with major- and trace-element compositions equivalent to Archaean TTG, including the low Nb/Ta and high Zr/Sm ratios of 'average' Archaean TTG, but from a source with initially subchondritic Nb/Ta. In modern environments, basalts with low Nb/Ta form by partial melting of subduction-modified depleted mantle, notably in intraoceanic arc settings in the forearc and back-arc regimes. These observations suggest that TTG magmatism may have taken place beneath granite-greenstone complexes developing along Archaean intraoceanic island arcs by imbricate thrust-stacking and tectonic accretion of a diversity of subduction-related terranes. Partial melting accompanying dehydration of these generally basaltic source materials at the base of thickened, 'arc-like' crust would produce compositionally appropriate TTG granitoids in equilibrium with eclogite residues.

  8. Comment on "Early Archaean microorganisms preferred elemental sulfur, not sulfate".

    PubMed

    Bao, Huiming; Sun, Tao; Kohl, Issaku; Peng, Yongbo

    2008-03-07

    Philippot et al. (Reports, 14 September 2007, p. 1534) interpreted multiple-sulfur isotopic compositions of approximately 3.5-billion-year-old marine sulfide deposits as evidence that early Archaean microorganisms were not sulfate reducers but instead metabolized elemental sulfur. However, their data can be better explained by a scenario involving poor mixing of photochemical and surface sulfide sources.

  9. Argon isotopic composition of Archaean atmosphere probes early Earth geodynamics.

    PubMed

    Pujol, Magali; Marty, Bernard; Burgess, Ray; Turner, Grenville; Philippot, Pascal

    2013-06-06

    Understanding the growth rate of the continental crust through time is a fundamental issue in Earth sciences. The isotopic signatures of noble gases in the silicate Earth (mantle, crust) and in the atmosphere afford exceptional insight into the evolution through time of these geochemical reservoirs. However, no data for the compositions of these reservoirs exists for the distant past, and temporal exchange rates between Earth's interior and its surface are severely under-constrained owing to a lack of samples preserving the original signature of the atmosphere at the time of their formation. Here, we report the analysis of argon in Archaean (3.5-billion-year-old) hydrothermal quartz. Noble gases are hosted in primary fluid inclusions containing a mixture of Archaean freshwater and hydrothermal fluid. Our analysis reveals Archaean atmospheric argon with a (40)Ar/(36)Ar value of 143 ± 24, lower than the present-day value of 298.6 (for which (40)Ar has been produced by the radioactive decay of the potassium isotope (40)K, with a half-life of 1.25 billion years; (36)Ar is primordial in origin). This ratio is consistent with an early development of the felsic crust, which might have had an important role in climate variability during the first half of Earth's history.

  10. Early Archaean collapse basins, a habitat for early bacterial life.

    NASA Astrophysics Data System (ADS)

    Nijman, W.

    For a better definition of the sedimentary environment in which early life may have flourished during the early Archaean, understanding of the basin geometry in terms of shape, depth, and fill is a prerequisite. The basin fill is the easiest to approach, namely from the well exposed, low-grade metamorphic 3.4 - 3.5 Ga rock successions in the greenstone belts of the east Pilbara (Coppin Gap Greenstone Belt and North Pole Dome) in West Australia and of the Barberton Greenstone Belt (Buck Ridge volcano-sedimentary complex) in South Africa. They consist of mafic to ultramafic volcanic rocks, largely pillow basalts, with distinct intercalations of intermediate to felsic intrusive and volcanic rocks and of silicious sediments. The, partly volcaniclastic, silicious sediments of the Buck Ridge and North Pole volcano-sedimentary complexes form a regressive-transgressive sequence. They were deposited close to base level, and experienced occasional emersion. Both North Pole Chert and the chert of the Kittys Gap volcano-sedimentary complex in the Coppin Gap Greenstone Belt preserve the flat-and-channel architecture of a shallow tidal environment. Thickness and facies distribution appear to be genetically linked to systems, i.e. arrays, of syn-depositionally active, extensional faults. Structures at the rear, front and bottoms of these fault arrays, and the fault vergence from the basin margin towards the centre characterize the basins as due to surficial crustal collapse. Observations in the Pilbara craton point to a non-linear plan view and persistence for the basin-defining fault patterns over up to 50 Ma, during which several of these fault arrays became superposed. The faults linked high-crustal level felsic intrusions within the overall mafic rock suite via porphyry pipes, black chert veins and inferred hydrothermal circulations with the overlying felsic lavas, and more importantly, with the cherty sediments. Where such veins surfaced, high-energy breccias, and in the

  11. A simple tectonic model for crustal accretion in the Slave Province: A 2.7-2.5 Ga granite greenstone terrane

    NASA Technical Reports Server (NTRS)

    Hoffman, P. F.

    1986-01-01

    A prograding (direction unspecified) trench-arc system is favored as a simple yet comprehensive model for crustal generation in a 250,000 sq km granite-greenstone terrain. The model accounts for the evolutionary sequence of volcanism, sedimentation, deformation, metamorphism and plutonism, observed througout the Slave province. Both unconformable (trench inner slope) and subconformable (trench outer slope) relations between the volcanics and overlying turbidities; and the existence of relatively minor amounts of pre-greenstone basement (microcontinents) and syn-greenstone plutons (accreted arc roots) are explained. Predictions include: a varaiable gap between greenstone volcanism and trench turbidite sedimentation (accompanied by minor volcanism) and systematic regional variations in age span of volcanism and plutonism. Implications of the model will be illustrated with reference to a 1:1 million scale geological map of the Slave Province (and its bounding 1.0 Ga orogens).

  12. Preliminary report on the geology and gold mineralization of the South Pass granite-greenstone terrain, Wind River Mountains, western Wyoming (US)

    NASA Technical Reports Server (NTRS)

    Hausel, W. D.

    1986-01-01

    The South Pass granite-greenstone terrain lies near the southern tip of the Wind River Mountains of western Wyoming. This Archean supracrustal pile has been Wyoming's most prolific source of gold and iron ore. From 1962 to 1983, more than 90 million tons of iron ore were recovered from oxide-facies banded iron formation, and an estimated 325,000 ounces of gold were mined from metagreywacke-hosted shears and associated placers. Precambrian rocks at South Pass are unconformably overlain by Paleozoic sediments along the northeast flank, and a Tertiary pediment buries Archean supracrustals on the west and south. To the northwest, the supracrustals terminate against granodiorite of the Louis Lake batholith; to the east, the supracrustals terminate against granite of the Granite Mountains batholith. The Louis Lake granodiorite is approximately 2,630 + or - 20 m.y. old, and the Granite Mountains granite averages 2,600 m.y. old. The geometry of the greenstone belt is best expressed as a synform that has been modified by complex faulting and folding. Metamorphism is amphibolite grade surrounding a small island of greenschist facies rocks. The younger of the Archean supracrustal successions is the Miners Delight Formation. This unit yielded a Rb-Sr isochron of 2,800 m.y. A sample of galena from the Snowbird Mine within the Miners Delight Formation yielded a model age averaging 2,750 m.y. The Snowbird mineralization appears to be syngenetic and is hosted by metavolcanics of calc-alkaline affinity. Discussion follows.

  13. Evidence of Archaean life - A brief appraisal

    NASA Technical Reports Server (NTRS)

    Schopf, J. W.

    1976-01-01

    Attention is called to the question of whether the meagerness of the Archaean fossil record is a function of a sparsity of preserved, cratonal, fossiliferous facies, or whether the abrupt break in the known fossil record near the Archaean-Proterozoic boundary reflects a major event in biological evolution. The paper then reviews the currently available geochemical and paleobiological data on Archaean biota. The occurrence of stromatolites in the Archaean, and the carbon isotopic composition of Archaean organic matter, both suggest strongly the existence of an Archaean biota. The presence of relatively abundant and morphologically complex microorganisms in deposits of early Proterozoic age seems to be certain evidence for a prior episode of Archaean evolution.

  14. Metamorphism of the ca. 3800 Ma supracrustal rocks at Isua, West Greenland: implications for early Archaean crustal evolution

    NASA Astrophysics Data System (ADS)

    Boak, Jeremy L.; Dymek, Robert F.

    1982-06-01

    A detailed mineralogical and petrological study has been carried out on samples from two clastic metasedimentary lithologies from the ˜ 3800 Ma Isua Supracrustal Belt, West Greenland. Semipelitic to pelitic "garnet-biotite schist" contains the limiting AKFM assemblage: muscovite-biotite-garnet-staurolite (+ quartz + plagioclase + ilmenite), whereas "muscovite-biotite gneiss", derived from felsic volcanogenic graywacke, locally contains kyanite (+ quartz+ plagioclase + Ca-, Mn-rich garnet). Temperatures calculated from Fe-Mg partitioning between coexisting garnet- biotite indicate equilibration for garnet coresat T ˜550°C, and ˜460°C for garnet rims. We interpret the higher T as a minimum estimate for prograde regional metamorphism which we argue occurred before 3600 Ma, whereas the lower T reflects later retrogression as indicated by the development of chlorite ± sericite in many samples. The presence of kyanite as the stable aluminosilicate polymorph, combined with phase assemblage data, indicate P ˜5 kbar during prograde metamorphism, and a depthof burial of at least 15 km. The Isua supracrustals are the oldest comprehensively dated rocks on Earth, and the metamorphic mineral assemblages reported here constitute the earliest direct record of thermal regimes in Archaean crust. Therefore, characterization of the metamorphic history of the Isua region places an important constraint on models of early Earth history. Our data and observations indicate that prograde regional metamorphism at Isua occurred at conditions which are considered "normal" for an orogenic system, with a metamorphic thermal gradient ˜35°C/km. Moreover, our results contraindicate the universal occurrence of "thin" Archaean crust and excessively "steep" crustal thermal gradients as proposed by some investigators. Such conclusion appears at odds with estimates for higher terrestrial heat production during the early Archaean, but can be resolved by appealing to more rapid convection and

  15. Geochemical and biologic constraints on the Archaean atmosphere and climate - A possible solution to the faint early Sun paradox.

    NASA Astrophysics Data System (ADS)

    Rosing, Minik T.; Bird, Dennis K.; Sleep, Norman H.; Bjerrum, Christian J.

    2010-05-01

    There is ample geological evidence that Earth's climate resembled the present during the Archaean, despite a much lower solar luminosity. This was cast as a paradox by Sagan and Mullen in 1972. Several solutions to the paradox have been suggested, mostly focusing on adjustments of the radiative properties of Earth's atmosphere e.g. Kasting (1993), by increasing the mixing ratio of CO2 and/or adding various other greenhouse gasses. We have used banded iron formation (BIF), which are chemical sediments precipitated out of the Archaean ocean to characterize the composition of the atmosphere. The stability relations of magnetite, which is ubiquitous in Archaean BIFs, preclude CO2 mixing ratios much higher than the present atmospheric level. Likewise, magnetite stability is consistent with atmospheric H2 controlled at the lower limit for H2 metabolism by methanogenic phototrophic organisms. In the absence of substantial compensation for the lower solar irradiance by greenhouse gasses in the atmosphere, we have examined the factors that controlled Earth's albedo. These are primarily the surface albedo of Earth and the abundance and properties of clouds. We have applied a model that takes into account the apparent growth of Earth continents (Collerson and Kamber 1999) and the absence of land vegetation during the Precambrian for the evolution of the surface albedo, and a model for the abundance and properties of clouds that takes into account the lower abundance of biogenic cloud condensation nuclei in a less productive prokaryotic world. The higher transparency of the atmosphere for short wave incoming solar radiation and the lower surface albedo on an early Earth dominated by oceans, provided sufficient compensation for the lower solar irradiance to allow the presence of liquid oceans, even at greenhouse gas concentrations broadly similar to the present day values. We therefore suggest that the thermostasis during Earth geologic record, is not paradoxical, but is the

  16. Evidence for extreme mantle fractionation in early Archaean ultramafic rocks from northern Labrador

    NASA Technical Reports Server (NTRS)

    Collerson, Kenneth D.; Campbell, Lisa M.; Weaver, Barry L.; Palacz, Zenon A.

    1991-01-01

    Samarium-neodymium isotope data for tectonically interleaved fragments of lithospheric mantle and meta-komatiite from the North Atlantic craton provide the first direct record of mantle differentiation before 3,800 Myr ago. The results confirm the magnitude of light-rare-earth-element depletion in the early mantle, and also its depleted neodymium isotope composition. The mantle fragments were able to retain these ancient geochemical signatures by virtue of having been tectonically incorporated in buoyant felsic crust, thus escaping recycling and homogenization by mantle convection.

  17. The early archaean crustal history of West Greenland as recorded by detrital zircons

    NASA Technical Reports Server (NTRS)

    Kinny, P. D.; Compston, W.; Mcgregor, V. R.

    1988-01-01

    The isotope systematics of some of the oldest samples on Earth from both Greenland and Australia was discussed. The antiquity was confirmed of the 4.1 to 4.2 Ga zircons from Western Australia; the model Lu-Hf age of these zircons, as measured with the ANU ion probe is 4.14 + or - 0.24 Ga, although the oldest preserved rock units there are anorthosites with a Lu-Hf model age of about 3.73 Ga. U-Pb ion probe ages of detrital zircons ranging between 2.87 and 3.89 Ga from an Akilia association quartzite was reported, whose age of deposition is probably around 3.8 Ga. It was argued that the younger age in this range are discordant because of late Pb-loss, probably associated with a high grade metamorphic event at about 3.6 Ga. It was also argued that the earliest crust in West Greenland and elsewhere is about 3.9 Ga, but in some places, such as Western Australia, crustal evolution took place much earlier, perhaps starting as far back as 4.3 Ga. This would account for the presence in that terrane of abundant K rich granitoid, the paucity of tonalitic and trondhjemitic materials, and the existence of Eu anomalies in early Archean sediments.

  18. Fossil Microorganisms in Archaean deposits of Northern Karelia

    NASA Technical Reports Server (NTRS)

    Astafieva, M. M.; Hoover, R. B.; Rozanov, A. Y.; Vrevskiy, A. B.

    2005-01-01

    Newly found biomorphic microstructures from the Upper Archaean (lopian) rocks from Northern Karelia are described. The presence of various microorganisms of bacterial nature and even cyanobacteria (and possibly eukaryotic forms) is suggested. The necessity of employing methods of electron microscopy, as well as traditional methods, while studying the very early manifestations of life in Archaean and Early Proterozoic is noted.

  19. Oxygen produced by cyanobacteria in simulated Archaean conditions partly oxidizes ferrous iron but mostly escapes-conclusions about early evolution.

    PubMed

    Rantamäki, Susanne; Meriluoto, Jussi; Spoof, Lisa; Puputti, Eeva-Maija; Tyystjärvi, Taina; Tyystjärvi, Esa

    2016-12-01

    The Earth has had a permanently oxic atmosphere only since the great oxygenation event (GOE) 2.3-2.4 billion years ago but recent geochemical research has revealed short periods of oxygen in the atmosphere up to a billion years earlier before the permanent oxygenation. If these "whiffs" of oxygen truly occurred, then oxygen-evolving (proto)cyanobacteria must have existed throughout the Archaean aeon. Trapping of oxygen by ferrous iron and other reduced substances present in Archaean oceans has often been suggested to explain why the oxygen content of the atmosphere remained negligible before the GOE although cyanobacteria produced oxygen. We tested this hypothesis by growing cyanobacteria in anaerobic high-CO2 atmosphere in a medium with a high concentration of ferrous iron. Microcystins are known to chelate iron, which prompted us also to test the effects of microcystins and nodularins on iron tolerance. The results show that all tested cyanobacteria, especially nitrogen-fixing species grown in the absence of nitrate, and irrespective of the ability to produce cyanotoxins, were iron sensitive in aerobic conditions but tolerated high concentrations of iron in anaerobicity. This result suggests that current cyanobacteria would have tolerated the high-iron content of Archaean oceans. However, only 1 % of the oxygen produced by the cyanobacterial culture was trapped by iron, suggesting that large-scale cyanobacterial photosynthesis would have oxygenated the atmosphere even if cyanobacteria grew in a reducing ocean. Recent genomic analysis suggesting that ability to colonize seawater is a secondary trait in cyanobacteria may offer a partial explanation for the sustained inefficiency of cyanobacterial photosynthesis during the Archaean aeon, as fresh water has always covered a very small fraction of the Earth's surface. If oxygenic photosynthesis originated in fresh water, then the GOE marks the adaptation of cyanobacteria to seawater, and the late-Proterozoic increase

  20. Petrogenetic constraints for the genesis of Archaean sanukitoid suites: geochemistry and isotopic evidence from Karelia, Baltic Shield

    NASA Astrophysics Data System (ADS)

    Kovalenko, A.; Clemens, J. D.; Savatenkov, V.

    2005-01-01

    New Sm-Nd isotope data are presented for late Archaean sanukitoid suites of the Karelian granite-greenstone terrane of the Baltic Shield. Within the terrane, there are regional variations in the Nd isotope compositions of the sanukitoids. Sanukitoids in the youngest Central Karelian domain have Nd isotope characteristics similar to depleted mantle, whereas those from the older West Karelian and Vodlozero domains have lower initial ɛNd values. The isotopic heterogeneity of the sanukitoids is interpreted to result from variations in the time interval between mantle source enrichment and the partial melting that produced the sanukitoid magmas. We therefore suggest a two-stage model of the generation of sanukitoid magmas. During first stage, the mantle was metasomatised by fluids and/or melts generated during subduction or tectonic underplating. Later, between 2.74 and 2.70 Ga, a tectonothermal anomaly generated the sanukitoid magmas by melting of the previously metasomatised mantle. Most of the sanukitoid intrusions are cut by calc-alkaline lamprophyre dykes that have the similar geochemical signatures to their sanukitoid wall rocks. New Sm-Nd isotope data for these lamprophyres suggest a genetic kinship between the sanukitoids and the lamprophyres. Comparison between chemical signatures of sanukitoids and modern, subduction-related magmas shows that Archaean sanukitoids actually have no modern analogues. Sanukitoid melts can be modelled as partial melts of mantle that had been metasomatised a short time previously. The melts could have been in equilibrium with residues containing Ol, Cpx plus minor Phl and Grt, at a pressure of about 2.5 GPa and a temperature of 1150-1230 °C. The small percentage of residual phlogopite would retain Rb in the mantle and explain the peculiar signature of low-Rb and high Ba and Sr, characteristic of the sanukitoids. We envisage a temporal evolution of the composition of the mantle in this region. This pattern of evolution controlled

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  2. The Hadean-Archaean environment.

    PubMed

    Sleep, Norman H

    2010-06-01

    A sparse geological record combined with physics and molecular phylogeny constrains the environmental conditions on the early Earth. The Earth began hot after the moon-forming impact and cooled to the point where liquid water was present in approximately 10 million years. Subsequently, a few asteroid impacts may have briefly heated surface environments, leaving only thermophile survivors in kilometer-deep rocks. A warm 500 K, 100 bar CO(2) greenhouse persisted until subducted oceanic crust sequestered CO(2) into the mantle. It is not known whether the Earth's surface lingered in a approximately 70 degrees C thermophile environment well into the Archaean or cooled to clement or freezing conditions in the Hadean. Recently discovered approximately 4.3 Ga rocks near Hudson Bay may have formed during the warm greenhouse. Alkalic rocks in India indicate carbonate subduction by 4.26 Ga. The presence of 3.8 Ga black shales in Greenland indicates that S-based photosynthesis had evolved in the oceans and likely Fe-based photosynthesis and efficient chemical weathering on land. Overall, mantle derived rocks, especially kimberlites and similar CO(2)-rich magmas, preserve evidence of subducted upper oceanic crust, ancient surface environments, and biosignatures of photosynthesis.

  3. The Hadean-Archaean Environment

    PubMed Central

    Sleep, Norman H.

    2010-01-01

    A sparse geological record combined with physics and molecular phylogeny constrains the environmental conditions on the early Earth. The Earth began hot after the moon-forming impact and cooled to the point where liquid water was present in ∼10 million years Subsequently, a few asteroid impacts may have briefly heated surface environments, leaving only thermophile survivors in kilometer-deep rocks. A warm 500 K, 100 bar CO2 greenhouse persisted until subducted oceanic crust sequestered CO2 into the mantle. It is not known whether the Earth's surface lingered in a ∼70°C thermophile environment well into the Archaean or cooled to clement or freezing conditions in the Hadean. Recently discovered ∼4.3 Ga rocks near Hudson Bay may have formed during the warm greenhouse. Alkalic rocks in India indicate carbonate subduction by 4.26 Ga. The presence of 3.8 Ga black shales in Greenland indicates that S-based photosynthesis had evolved in the oceans and likely Fe-based photosynthesis and efficient chemical weathering on land. Overall, mantle derived rocks, especially kimberlites and similar CO2-rich magmas, preserve evidence of subducted upper oceanic crust, ancient surface environments, and biosignatures of photosynthesis. PMID:20516134

  4. Feldspar palaeo-isochrons from early Archaean TTGs: Pb-isotope evidence for a high U/Pb terrestrial Hadean crust

    NASA Astrophysics Data System (ADS)

    Kamber, B. S.; Whitehouse, M. J.; Moorbath, S.; Collerson, K. D.

    2001-12-01

    Feldspar lead-isotope data for 22 early Archaean (3.80-3.82 Ga) tonalitic gneisses from an area south of the Isua greenstone belt (IGB),West Greenland, define a steep linear trend in common Pb-isotope space with an apparent age of 4480+/-77 Ma. Feldspars from interleaved amphibolites yield a similar array corresponding to a date of 4455+/-540 Ma. These regression lines are palaeo-isochrons that formed during feldspar-whole rock Pb-isotope homogenisation a long time (1.8 Ga) after rock formation but confirm the extreme antiquity (3.81 Ga) of the gneissic protoliths [1; this study]. Unlike their whole-rock counterparts, feldspar palaeo-isochrons are immune to rotational effects caused by the vagaries of U/Pb fractionation. Hence, comparison of their intercept with mantle Pb-isotope evolution models yields meaningful information regarding the source history of the magmatic precursors. The locus of intersection between the palaeo-isochrons and terrestrial mantle Pb-isotope evolution lines shows that the gneissic precursors of these 3.81 Ga gneisses were derived from a source with a substantially higher time-integrated U/Pb ratio than the mantle. Similar requirements for a high U/Pb source have been found for IGB BIF [2], IGB carbonate [3], and particularly IGB galenas [4]. Significantly, a single high U/Pb source that separated from the MORB-source mantle at ca. 4.3 Ga with a 238U/204Pb of ca. 10.5 provides a good fit to all these observations. In contrast to many previous models based on Nd and Hf-isotope evidence we propose that this reservoir was not a mantle source but the Hadean basaltic crust which, in the absence of an operating subduction process, encased the early Earth. Differentiation of the early high U/Pb basaltic crust could have occurred in response to gravitational sinking of cold mantle material or meteorite impact, and produced zircon-bearing magmatic rocks. The subchondritic Hf-isotope ratios of ca. 3.8 Ga zircons support this model [5] provided that

  5. Fossil evidence of Archaean life

    PubMed Central

    Schopf, J. William

    2006-01-01

    Evidence for the existence of life during the Archaean segment of Earth history (more than 2500 Myr ago) is summarized. Data are presented for 48 Archaean deposits reported to contain biogenic stromatolites, for 14 such units reported to contain 40 morphotypes of putative microfossils, and for 13 especially ancient, 3200–3500 Myr old geologic units for which available organic geochemical data are also summarized. These compilations support the view that life's existence dates from more than or equal to 3500 Myr ago. PMID:16754604

  6. Evolution of the Archaean crust by delamination and shallow subduction.

    PubMed

    Foley, Stephen F; Buhre, Stephan; Jacob, Dorrit E

    2003-01-16

    The Archaean oceanic crust was probably thicker than present-day oceanic crust owing to higher heat flow and thus higher degrees of melting at mid-ocean ridges. These conditions would also have led to a different bulk composition of oceanic crust in the early Archaean, that would probably have consisted of magnesium-rich picrite (with variably differentiated portions made up of basalt, gabbro, ultramafic cumulates and picrite). It is unclear whether these differences would have influenced crustal subduction and recycling processes, as experiments that have investigated the metamorphic reactions that take place during subduction have to date considered only modern mid-ocean-ridge basalts. Here we present data from high-pressure experiments that show that metamorphism of ultramafic cumulates and picrites produces pyroxenites, which we infer would have delaminated and melted to produce basaltic rocks, rather than continental crust as has previously been thought. Instead, the formation of continental crust requires subduction and melting of garnet-amphibolite--formed only in the upper regions of oceanic crust--which is thought to have first occurred on a large scale during subduction in the late Archaean. We deduce from this that shallow subduction and recycling of oceanic crust took place in the early Archaean, and that this would have resulted in strong depletion of only a thin layer of the uppermost mantle. The misfit between geochemical depletion models and geophysical models for mantle convection (which include deep subduction) might therefore be explained by continuous deepening of this depleted layer through geological time.

  7. Geological constraints on detecting the earliest life on Earth: a perspective from the Early Archaean (older than 3.7 Gyr) of southwest Greenland.

    PubMed

    Fedo, Christopher M; Whitehouse, Martin J; Kamber, Balz S

    2006-06-29

    At greater than 3.7 Gyr, Earth's oldest known supracrustal rocks, comprised dominantly of mafic igneous with less common sedimentary units including banded iron formation (BIF), are exposed in southwest Greenland. Regionally, they were intruded by younger tonalites, and then both were intensely dynamothermally metamorphosed to granulite facies (the highest pressures and temperatures generally encountered in the Earth's crust during metamorphism) in the Archaean and subsequently at lower grades until about 1500 Myr ago. Claims for the first preserved life on Earth have been based on the occurrence of greater than 3.8 Gyr isotopically light C occurring as graphite inclusions within apatite crystals from a 5 m thick purported BIF on the island of Akilia. Detailed geologic mapping and observations there indicate that the banding, first claimed to be depositional, is clearly deformational in origin. Furthermore, the mineralogy of the supposed BIF, being dominated by pyroxene, amphibole and quartz, is unlike well-known BIF from the Isua Greenstone Belt (IGB), but resembles enclosing mafic and ultramafic igneous rocks modified by metasomatism and repeated metamorphic recrystallization. This scenario parsimoniously links the geology, whole-rock geochemistry, 2.7 Gyr single crystal zircon ages in the unit, an approximately 1500 Myr age for apatites that lack any graphite, non-MIF sulphur isotopes in the unit and an inconclusive Fe isotope signature. Although both putative body fossils and carbon-12 enriched isotopes in graphite described at Isua are better explained by abiotic processes, more fruitful targets for examining the earliest stages in the emergence of life remain within greater than 3.7 Gyr IGB, which preserves BIF and other rocks that unambiguously formed at Earth's surface.

  8. Geological constraints on detecting the earliest life on Earth: a perspective from the Early Archaean (older than 3.7 Gyr) of southwest Greenland

    PubMed Central

    Fedo, Christopher M; Whitehouse, Martin J; Kamber, Balz S

    2006-01-01

    At greater than 3.7 Gyr, Earth's oldest known supracrustal rocks, comprised dominantly of mafic igneous with less common sedimentary units including banded iron formation (BIF), are exposed in southwest Greenland. Regionally, they were intruded by younger tonalites, and then both were intensely dynamothermally metamorphosed to granulite facies (the highest pressures and temperatures generally encountered in the Earth's crust during metamorphism) in the Archaean and subsequently at lower grades until about 1500 Myr ago. Claims for the first preserved life on Earth have been based on the occurrence of greater than 3.8 Gyr isotopically light C occurring as graphite inclusions within apatite crystals from a 5 m thick purported BIF on the island of Akilia. Detailed geologic mapping and observations there indicate that the banding, first claimed to be depositional, is clearly deformational in origin. Furthermore, the mineralogy of the supposed BIF, being dominated by pyroxene, amphibole and quartz, is unlike well-known BIF from the Isua Greenstone Belt (IGB), but resembles enclosing mafic and ultramafic igneous rocks modified by metasomatism and repeated metamorphic recrystallization. This scenario parsimoniously links the geology, whole-rock geochemistry, 2.7 Gyr single crystal zircon ages in the unit, an approximately 1500 Myr age for apatites that lack any graphite, non-MIF sulphur isotopes in the unit and an inconclusive Fe isotope signature. Although both putative body fossils and carbon-12 enriched isotopes in graphite described at Isua are better explained by abiotic processes, more fruitful targets for examining the earliest stages in the emergence of life remain within greater than 3.7 Gyr IGB, which preserves BIF and other rocks that unambiguously formed at Earth's surface. PMID:16754603

  9. Fossil Microorganisms in Archaean

    NASA Technical Reports Server (NTRS)

    Astafleva, Marina; Hoover, Richard; Rozanov, Alexei; Vrevskiy, A.

    2006-01-01

    Ancient Archean and Proterozoic rocks are the model objects for investigation of rocks comprising astromaterials. The first of Archean fossil microorganisms from Baltic shield have been reported at the last SPIE Conference in 2005. Since this confeence biomorphic structures have been revealed in Archean rocks of Karelia. It was determined that there are 3 types of such bion structures: 1. structures found in situ, in other words microorganisms even-aged with rock matrix, that is real Archean fossils biomorphic structures, that is to say forms inhabited early formed rocks, and 3. younger than Archean-Protherozoic minerali microorganisms, that is later contamination. We made attempt to differentiate these 3 types of findings and tried to understand of burial of microorganisms. The structures belongs (from our point of view) to the first type, or real Archean, forms were under examination. Practical investigation of ancient microorganisms from Green-Stone-Belt of Northern Karelia turns to be very perspective. It shows that even in such ancient time as Archean ancient diverse world existed. Moreover probably such relatively highly organized cyanobacteria and perhaps eukaryotic formes existed in Archean world.

  10. Contributions to late Archaean sulphur cycling by life on land

    NASA Astrophysics Data System (ADS)

    Stüeken, Eva E.; Catling, David C.; Buick, Roger

    2012-10-01

    Evidence in palaeosols suggests that life on land dates back to at least 2.76Gyr ago. However, the biogeochemical effects of Archaean terrestrial life are thought to have been limited, owing to the lack of a protective ozone shield from ultraviolet radiation for terrestrial organisms before the rise of atmospheric oxygen levels several hundred million years later. Records of chromium delivery from the continents suggest that microbial mineral oxidation began at least 2.48Gyr ago but do not indicate when the terrestrial biosphere began to dominate important biogeochemical cycles. Here we combine marine sulphur abundance data with a mass balance model of the sulphur cycle to estimate the effects of the Archaean and early Proterozoic terrestrial biosphere on sulphur cycling. We find that terrestrial oxidation of pyrite by microbes using oxygen has contributed a substantial fraction of the total sulphur weathering flux since at least 2.5Gyr ago, with probable evidence of such activity 2.7-2.8Gyr ago. The late Archaean onset of terrestrial sulphur cycling is supported by marine molybdenum abundance data and coincides with a shift to more sulphidic ocean conditions. We infer that significant microbial land colonization began by 2.7-2.8Gyr ago. Our identification of pyrite oxidation at this time provides further support for the appearance of molecular oxygen several hundred million years before the Great Oxidation Event.

  11. Fractional Crystallisation of Archaean Trondhjemite Magma at 12-7 Kbar: Constraints on Rheology of Archaean Continental Crust

    NASA Astrophysics Data System (ADS)

    Sarkar, Saheli; Saha, Lopamudra; Satyanarayan, Manavalan; Pati, Jayanta

    2015-04-01

    fractionating from the magma are mostly clinopyroxene with minor orthopyroxene. Plagioclase crystals appear at pressures ≤ 15 kbar. Plagioclase crystals are mostly albitic in composition (XAb ~0.70-0.75). At each pressure, with progressive cooling and fractionation of solid phases, crystal-melt ratio becomes significantly higher, magma becomes more depleted in Al2O3, MgO, with significant increase in K2O/Na2O ratio and water content. With progressive cooling and fractionation, overall composition of the magma changes from trondhjemitic to granitic, with increase in viscosity from 4.5 poise to 5.5 poise. The study thus reveals that fractional crystallization of trondhemitic magmas at different depths can form more potassic granitic magma with higher viscosity. As Hf isotope signatures from most Archaean TTGs reveal longer crustal residence, it is likely that granitic magmas that became more common in the Neoarchaean period, could also possibly been derived by fractional crystallization from trondhjemitic magmas in Mesoarchaean time. Granitic magmas hence generated have much higher viscosity compared to the parent trondhjemitic magma. Low viscosity of trondhjemitic magmas and low crystal-melt ratios in the initial stages of crystallization (as derived in this study), may be the cause of formation of large bodies of TTGs in Early Archaean period. Close to Neoarchaean period more granitic magmas are observed. In this study it has been observed that crystallization of these magmas lead to high crystal-melt ratios and the magmas have higher viscosity. Such change in composition from Early to Neoarchaean time must have made Archaean crusts stronger and hence more prone to deformation. This observation hence support occurrence of Phanerozoic style signatures from poly-deformed terrains of Neoarchaean time.

  12. Novel protein families in archaean genomes.

    PubMed Central

    Ouzonis, C; Kyrpides, N; Sander, C

    1995-01-01

    In a quest for novel functions in archaea, all archaean hypothetical open reading frames (ORFs), as annotated in the Swiss-Prot protein sequence database, were used to search the latest databases for the identification of characterized homologues. Of the 95 hypothetical archaean ORFs, 25 were found to be homologous to another hypothetical archaean ORF, while 36 were homologous to non-archaean proteins, of which as many as 30 were homologous to a characterized protein family. Thus the level of sequence similarity in this set reaches 64%, while the level of function assignment is only 32%. Of the ORFs with predicted functions, 12 homologies are reported here for the first time and represent nine new functions and one gene duplication at an acetyl-coA synthetase locus. The novel functions include components of the transcriptional and translational apparatus, such as ribosomal proteins, modification enzymes and a translation initiation factor. In addition, new enzymes are identified in archaea, such as cobyric acid synthase, dCTP deaminase and the first archaean homologues of a new subclass of ATP binding proteins found in fungi. Finally, it is shown that the putative laminin receptor family of eukaryotes and an archaean homologue belong to the previously characterized ribosomal protein family S2 from eubacteria. From the present and previous work, the major implication is that archaea seem to have a mode of expression of genetic information rather similar to eukaryotes, while eubacteria may have proceeded into unique ways of transcription and translation. In addition, with the detection of proteins in various metabolic and genetic processes in archaea, we can further predict the presence of additional proteins involved in these processes. PMID:7899076

  13. Komatiites reveal a hydrous Archaean deep-mantle reservoir

    NASA Astrophysics Data System (ADS)

    Sobolev, Alexander V.; Asafov, Evgeny V.; Gurenko, Andrey A.; Arndt, Nicholas T.; Batanova, Valentina G.; Portnyagin, Maxim V.; Garbe-Schönberg, Dieter; Krasheninnikov, Stepan P.

    2016-03-01

    Archaean komatiites (ultramafic lavas) result from melting under extreme conditions of the Earth’s mantle. Their chemical compositions evoke very high eruption temperatures, up to 1,600 degrees Celsius, which suggests even higher temperatures in their mantle source. This message is clouded, however, by uncertainty about the water content in komatiite magmas. One school of thought holds that komatiites were essentially dry and originated in mantle plumes while another argues that these magmas contained several per cent water, which drastically reduced their eruption temperature and links them to subduction processes. Here we report measurements of the content of water and other volatile components, and of major and trace elements in melt inclusions in exceptionally magnesian olivine (up to 94.5 mole per cent forsterite). This information provides direct estimates of the composition and crystallization temperature of the parental melts of Archaean komatiites. We show that the parental melt for 2.7-billion-year-old komatiites from the Abitibi greenstone belt in Canada contained 30 per cent magnesium oxide and 0.6 per cent water by weight, and was depleted in highly incompatible elements. This melt began to crystallize at around 1,530 degrees Celsius at shallow depth and under reducing conditions, and it evolved via fractional crystallization of olivine, accompanied by minor crustal assimilation. As its major- and trace-element composition and low oxygen fugacities are inconsistent with a subduction setting, we propose that its high H2O/Ce ratio (over 6,000) resulted from entrainment into the komatiite source of hydrous material from the mantle transition zone. These results confirm a plume origin for komatiites and high Archaean mantle temperatures, and evoke a hydrous reservoir in the deep mantle early in Earth’s history.

  14. Komatiites reveal a hydrous Archaean deep-mantle reservoir.

    PubMed

    Sobolev, Alexander V; Asafov, Evgeny V; Gurenko, Andrey A; Arndt, Nicholas T; Batanova, Valentina G; Portnyagin, Maxim V; Garbe-Schönberg, Dieter; Krasheninnikov, Stepan P

    2016-03-31

    Archaean komatiites (ultramafic lavas) result from melting under extreme conditions of the Earth's mantle. Their chemical compositions evoke very high eruption temperatures, up to 1,600 degrees Celsius, which suggests even higher temperatures in their mantle source. This message is clouded, however, by uncertainty about the water content in komatiite magmas. One school of thought holds that komatiites were essentially dry and originated in mantle plumes while another argues that these magmas contained several per cent water, which drastically reduced their eruption temperature and links them to subduction processes. Here we report measurements of the content of water and other volatile components, and of major and trace elements in melt inclusions in exceptionally magnesian olivine (up to 94.5 mole per cent forsterite). This information provides direct estimates of the composition and crystallization temperature of the parental melts of Archaean komatiites. We show that the parental melt for 2.7-billion-year-old komatiites from the Abitibi greenstone belt in Canada contained 30 per cent magnesium oxide and 0.6 per cent water by weight, and was depleted in highly incompatible elements. This melt began to crystallize at around 1,530 degrees Celsius at shallow depth and under reducing conditions, and it evolved via fractional crystallization of olivine, accompanied by minor crustal assimilation. As its major- and trace-element composition and low oxygen fugacities are inconsistent with a subduction setting, we propose that its high H2O/Ce ratio (over 6,000) resulted from entrainment into the komatiite source of hydrous material from the mantle transition zone. These results confirm a plume origin for komatiites and high Archaean mantle temperatures, and evoke a hydrous reservoir in the deep mantle early in Earth's history.

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

    PubMed

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

    2006-08-03

    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.

  16. The effect of thicker oceanic crust in the Archaean on the growth of continental crust through time

    NASA Technical Reports Server (NTRS)

    Wilks, M. E.

    1988-01-01

    Present crustal evolution models fail to account for the generation of the large volume of continental crust in the required time intervals. All Archaean plate tectonic models, whether invoking faster spreading rates, similar to today's spreading rates, or longer ridge lengths, essentially propose that continental crust has grown by island arc accretion due to the subduction of oceanic crust. The petrological differences that characterize the Archaean from later terrains result from the subduction of hotter oceanic crust into a hotter mantle. If the oceanic crust was appreciably thicker in the Archaean, as geothermal models would indicate, this thicker crust is surely going to have an effect on tectonic processes. A more valid approach is to compare the possible styles of convergence of thick oceanic crust with modern convergence zones. The best modern analog occurs where thick continental crust is colliding with thick continental crust. Oceanic crustal collision on the scale of the present-day Himalayan continental collision zone may have been a frequent occurrence in the Archaean, resulting in extensive partial melting of the hydrous underthrust oceanic crust to produce voluminous tonalite melts, leaving a depleted stabilized basic residuum. Present-day island arc accretion may not have been the dominant mechanism for the growth of the early Archaean crust.

  17. Volcanological constraints of Archaean tectonics

    NASA Technical Reports Server (NTRS)

    Thurston, P. C.; Ayres, L. D.

    1986-01-01

    Volcanological and trace element geochemical data can be integrated to place some constraints upon the size, character and evolutionary history of Archean volcanic plumbing, and hence indirectly, Archean tectonics. The earliest volcanism in any greenhouse belt is almost universally tholeitic basalt. Archean mafic magma chambers were usually the site of low pressure fractionation of olivine, plagioclase and later Cpx + or - an oxide phase during evolution of tholeitic liquids. Several models suggest basalt becoming more contaminated by sial with time. Data in the Uchi Subprovince shows early felsic volcanics to have fractionated REE patterns followed by flat REE pattern rhyolites. This is interpreted as initial felsic liquids produced by melting of a garnetiferous mafic source followed by large scale melting of LIL-rich sial. Rare andesites in the Uchi Subprovince are produced by basalt fractionation, direct mantle melts and mixing of basaltic and tonalitic liquids. Composite dikes in the Abitibi Subprovince have a basaltic edge with a chill margin, a rhyolitic interior with no basalt-rhyolite chill margin and partially melted sialic inclusions. Ignimbrites in the Uchi and Abitibi Subprovinces have mafic pumice toward the top. Integration of these data suggest initial mantle-derived basaltic liquids pond in a sialic crust, fractionate and melt sial. The inirial melts low in heavy REE are melts of mafic material, subsequently melting of adjacent sial produces a chamber with a felsic upper part underlain by mafic magma.

  18. Ancient micrometeorites suggestive of an oxygen-rich Archaean upper atmosphere.

    PubMed

    Tomkins, Andrew G; Bowlt, Lara; Genge, Matthew; Wilson, Siobhan A; Brand, Helen E A; Wykes, Jeremy L

    2016-05-12

    It is widely accepted that Earth's early atmosphere contained less than 0.001 per cent of the present-day atmospheric oxygen (O2) level, until the Great Oxidation Event resulted in a major rise in O2 concentration about 2.4 billion years ago. There are multiple lines of evidence for low O2 concentrations on early Earth, but all previous observations relate to the composition of the lower atmosphere in the Archaean era; to date no method has been developed to sample the Archaean upper atmosphere. We have extracted fossil micrometeorites from limestone sedimentary rock that had accumulated slowly 2.7 billion years ago before being preserved in Australia's Pilbara region. We propose that these micrometeorites formed when sand-sized particles entered Earth's atmosphere and melted at altitudes of about 75 to 90 kilometres (given an atmospheric density similar to that of today). Here we show that the FeNi metal in the resulting cosmic spherules was oxidized while molten, and quench-crystallized to form spheres of interlocking dendritic crystals primarily of magnetite (Fe3O4), with wüstite (FeO)+metal preserved in a few particles. Our model of atmospheric micrometeorite oxidation suggests that Archaean upper-atmosphere oxygen concentrations may have been close to those of the present-day Earth, and that the ratio of oxygen to carbon monoxide was sufficiently high to prevent noticeable inhibition of oxidation by carbon monoxide. The anomalous sulfur isotope (Δ(33)S) signature of pyrite (FeS2) in seafloor sediments from this period, which requires an anoxic surface environment, implies that there may have been minimal mixing between the upper and lower atmosphere during the Archaean.

  19. Phosphate oxygen isotopic evidence for a temperate and biologically active Archaean ocean.

    PubMed

    Blake, Ruth E; Chang, Sae Jung; Lepland, Aivo

    2010-04-15

    Oxygen and silicon isotope compositions of cherts and studies of protein evolution have been interpreted to reflect ocean temperatures of 55-85 degrees C during the early Palaeoarchaean era ( approximately 3.5 billion years ago). A recent study combining oxygen and hydrogen isotope compositions of cherts, however, makes a case for Archaean ocean temperatures being no greater than 40 degrees C (ref. 5). Ocean temperature can also be assessed using the oxygen isotope composition of phosphate. Recent studies show that (18)O:(16)O ratios of dissolved inorganic phosphate (delta(18)O(P)) reflect ambient seawater temperature as well as biological processing that dominates marine phosphorus cycling at low temperature. All forms of life require and concentrate phosphorus, and as a result of biological processing, modern marine phosphates have delta(18)O(P) values typically between 19-26 per thousand (VSMOW), highly evolved from presumed source values of approximately 6-8 per thousand that are characteristic of apatite in igneous rocks and meteorites. Here we report oxygen isotope compositions of phosphates in sediments from the 3.2-3.5-billion-year-old Barberton Greenstone Belt in South Africa. We find that delta(18)O(P) values range from 9.3 per thousand to 19.9 per thousand and include the highest values reported for Archaean rocks. The temperatures calculated from our highest delta(18)O(P) values and assuming equilibrium with sea water with delta(18)O = 0 per thousand (ref. 12) range from 26 degrees C to 35 degrees C. The higher delta(18)O(P) values are similar to those of modern marine phosphate and suggest a well-developed phosphorus cycle and evolved biologic activity on the Archaean Earth.

  20. Archaean Crustal Growth, Proterozoic Terrane Amalgamation and the Pan-African Orogeny, as Recorded in the NE African Sedimentary Record.

    NASA Astrophysics Data System (ADS)

    Najman, Y.; Fielding, L.; Millar, I.; Butterworth, P.; Andò, S.; Padoan, M.; Barfod, D. N.; Kneller, B. C.

    2015-12-01

    The cratons of Central Africa are formed of various blocks of Archaean and Palaeoproterozoic crust, flanked or truncated by Palaeoproterozoic to Mesoproterozoic orogenic belts. The geology of east Africa has largely been shaped by the events of the Pan-African Orogeny when east and west Gondwana collided to form 'Greater Gondwana' at the end of the Neoproterozoic. The Pan-African orogeny in NE Africa involved the collision of Archaean cratons and the Saharan Metacraton with the Arabian Nubian Shield, a terrane comprising Neoproterozoic juvenile oceanic island arcs. Phanerozoic cover sedimentary rocks, eroded from the Pan-African orogenies, blanket much of NE Africa. Detrital data from these Phanerozoic cover sedimentary rocks, and modern rivers draining both the cover the basement, provide a wealth of information on basement evolution, of particular relevance for regions where the basement itself is poorly exposed due to ancient or modern sedimentary cover. From samples collected in Uganda, Ethiopia, Sudan and Egypt, we provide combined U-Pb and Hf-isotope zircon, U-Pb rutile and Ar-Ar mica datasets, heavy mineral analyses, and bulk trace element data, from Archaean basement, Phanerozoic cover and modern river sediment from the Nile and its tributaries to document the evolution of the North African crust. The data document early crust-forming events in the Congo Craton and Sahara Metacraton, phased development of the Arabian Nubian Shield culminating in the Neoproterozoic assembly of Gondwana during the Pan African Orogeny, and the orogen's subsequent erosion, with deposition of voluminous Phanerozoic cover.

  1. A possible nitrogen crisis for Archaean life due to reduced nitrogen fixation by lightning.

    PubMed

    Navarro-González, R; McKay, C P; Mvondo, D N

    2001-07-05

    Nitrogen is an essential element for life and is often the limiting nutrient for terrestrial ecosystems. As most nitrogen is locked in the kinetically stable form, N2, in the Earth's atmosphere, processes that can fix N2 into biologically available forms-such as nitrate and ammonia-control the supply of nitrogen for organisms. On the early Earth, nitrogen is thought to have been fixed abiotically, as nitric oxide formed during lightning discharge. The advent of biological nitrogen fixation suggests that at some point the demand for fixed nitrogen exceeded the supply from abiotic sources, but the timing and causes of the onset of biological nitrogen fixation remain unclear. Here we report an experimental simulation of nitrogen fixation by lightning over a range of Hadean (4.5-3.8 Gyr ago) and Archaean (3.8-2.5 Gyr ago) atmospheric compositions, from predominantly carbon dioxide to predominantly dinitrogen (but always without oxygen). We infer that, as atmospheric CO2 decreased over the Archaean period, the production of nitric oxide from lightning discharge decreased by two orders of magnitude until about 2.2 Gyr. After this time, the rise in oxygen (or methane) concentrations probably initiated other abiotic sources of nitrogen. Although the temporary reduction in nitric oxide production may have lasted for only 100 Myr or less, this was potentially long enough to cause an ecological crisis that triggered the development of biological nitrogen fixation.

  2. Zircon Lu-Hf systematics: Evidence for the episodic development of Archaean greenstone belts

    NASA Technical Reports Server (NTRS)

    Smith, P. E.; Tatsumoto, M.; Farquhar, R. M.

    1986-01-01

    A combined U-Th-Pb and Lu-Hf isotopic study of zircons was undertaken in order to determine the provenance and age of an Archean granite-greenstone terrain and to test the detailed application of the Lu-Hf system in various Archean zircons. The eastern Wawa subprovince of the Superior province consists of the low grade Michipicoten and Gamitagama greenstone belts and the granitic terrain. The Hf isotopic data indicate that the typical lithological features of a greenstone belt cycle could be accommodated in a crustal growth model that involved decreasing depth of melting in three isotopically distinct reservoirs: mantle, lower crust and upper crust. The model age of the sources given by the intersection of the lower crustal curve with the bulk earth evolution curve is about 2900 My, in good agreement with the zircon U-Pb basement age. This linear array also has a similar intersection age to that of Proterozoic carbonatite complexes. The general convergence of the other reservoir vectors around this age suggests that mantle depletion, crustal extraction and intracrustal differentiation were all part of the same episodic event. It is also apparent that recycling of older basement was important in the formation of many of the later greenstone belt rocks.

  3. Rainy Lake wrench zone: An example of an Archaean subprovince boundary in northwestern Ontario

    NASA Technical Reports Server (NTRS)

    Poulsen, K. H.

    1986-01-01

    The Superior Province of the Canadian Shield comprises an alternation of subprovinces with contrasting lithological, structural and metamorphic styles. Rocks of the Rainly Lake area form a fault bounded wedge between two of these subprovinces, the Wabigoon granite-greenstone terrain to the north and the Quetico metasedimentary terrain to the south. The Quetico and Seine River-Rainy Lake Faults bound this wedge within which interpretation of the stratigraphy has been historically contentious. In the eastern part of the wedge, volcanic rocks and coeval tonalitic sills are unconformably overlain by fluviatile conglomerate and arenite of the Seine Group; in the western part of the wedge, metamorphosed wacke and mudstone of the Coutchiching Group are cut by granodioritic plutons. The Coutchiching Group has previously been correlated with the Seine Group and with the turbiditic Quetico metasediments of the Quetico Subprovince and these correlations are the cornerstone of earlier tectonic models which relate the subprovinces. The structural geology of the Rainy Lake area is characterized by attributes which compare favourably with the known characteristics of dextral wrench or 'transpressive zones based both on experimental data and natural examples. Much of this deformation involved the Seine Group, the youngest stratigraphic unit in the area, and predates the emplacement of late-to-post-tectonic granodioritic plutons for which radiometric data indicate a Late Archean age.

  4. Implications of a reducing and warm (not hot) Archaean ambient mantle for ancient element cycles

    NASA Astrophysics Data System (ADS)

    Aulbach, Sonja

    2016-04-01

    There is considerable uncertainty regarding the oxygen partial pressure (fO2) and potential temperature (TP) of the ambient convecting mantle throughout Earth's history. Rare Archaean eclogite suites have elemental and isotopic compositions indicative of formation of crustal protoliths in oceanic spreading ridges, hence unaffected by continental sources. These include some eclogite xenoliths derived from cratonic mantle lithosphere and orogenic eclogites marking the exhumation of oceanic crust at Pacific-type margins. Their compositions may retain a memory of the thermal and redox state of the Archaean convecting mantle sources that gave rise to their low-pressure protoliths. Archaean eclogites have TiO2-REE relationships consistent with fractional crystallisation of olivine±plagioclase and cpx during formation of picritic protoliths from a melt that separated from a garnet-free peridotite source, implying intersection of the solidus at ≤2.5 to 3.0 GPa [1]. Low melt fractions (<0.25) inferred from samples with the least fractionated (lowest TiO2) protoliths further argue against deep intersection of the mantle solidus. This suggests a moderately elevated TP ~ 1420-1470 degrees C (lower than some estimates for the ambient convecting mantle at that time [2]), which would support an early onset of plate tectonics [3] and emergence of continents [4], heralding a transition to modern chemical cycles. Moderate TP further indicates that deep recycling of carbon and water, though reduced compared to today, may have been possible in the Archaean [5,6]. Carefully screened eclogites have V/Sc (reflecting the redox state of the ambient mantle during protolith formation [7]) corresponding to ΔFMQ corrected to 1 GPa as low as -1.7 at 3 Ga [1]. Such low oxygen fugacities have consequences for the location of the peridotite solidus and for the types of melts generated during redox melting [5,8]. They also modulate the redox state of volatiles liberated at oceanic spreading

  5. Archaean asteroid impacts, banded iron formations and MIF-S anomalies: A discussion

    NASA Astrophysics Data System (ADS)

    Glikson, Andrew

    2010-05-01

    on impact spherule size distribution ( Melosh, H.J., Vickery, A.M. [1991] Nature, 350, 494-497) suggest projectiles several tens of kilometers in diameter (Byerly and Lowe, 1994; Shukloyukov, A., Kyte, F.T., Lugmair, G.W., Lowe, D.R., Byerly, G.R. [2000]. In: Koeberl, C., Gilmour, I. (Eds.), Impacts and the Early Earth, Springer-Verlag, Berlin, pp. 99-116; Kyte, F.T., Shukloyukov, A., Lugmair, G.W., Lowe, D.R., Byerly, G.R. [2003] Geology, 31, 283-286). Due to incomplete preservation these impacts represent a minimum rate of the Archaean impact flux. High UV radiation associated with low ozone levels in the Archaean atmosphere may have been further enhanced by large impacts, accentuating MIF-S anomalies. The appearance of iron-rich sediments above late and mid-Archaean impact ejecta units (Glikson, A.Y. [2006] Earth Planet. Sci. Lett., 246, 149-160; Glikson, A.Y., Vickers, J. [2007] Earth Planet. Sci. Lett., 254, 214-226) may be related either to microbial oxidation of ferrous iron or, alternatively, photochemical oxidation of ferrous to ferric iron. Given post-2.45 Ga diluting of possible MIF-S anomalies by the oxygenating ocean sulfate reservoir (Pavlov, A.A., Kasting, J.F. [2002] Astrobiology, 2, 27-41), similar MIF-S anomalies may have been associated with Proterozoic and Phanerozoic impacts, although to date little evidence exists in this regard (Marouka, T., Koeberl, C., Newton, J., Gilmour, I., Bohor, B.F. [2002] Geological Society of America Special Paper 356, pp. 337-344; Koeberl, C., Thiemens, M. [2008] Multi-sulfur isotopes in cretaceous-tertiary boundary samples from the Western interior-search for photochemical effects 2008. Joint Meeting of the Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM. (abstract)). Detailed sampling and

  6. The elusive Hadean enriched reservoir revealed by 142Nd deficits in Isua Archaean rocks.

    PubMed

    Rizo, Hanika; Boyet, Maud; Blichert-Toft, Janne; O'Neil, Jonathan; Rosing, Minik T; Paquette, Jean-Louis

    2012-11-01

    The first indisputable evidence for very early differentiation of the silicate Earth came from the extinct (146)Sm-(142)Nd chronometer. (142)Nd excesses measured in 3.7-billion-year (Gyr)-old rocks from Isua (southwest Greenland) relative to modern terrestrial samples imply their derivation from a depleted mantle formed in the Hadean eon (about 4,570-4,000 Gyr ago). As dictated by mass balance, the differentiation event responsible for the formation of the Isua early-depleted reservoir must also have formed a complementary enriched component. However, considerable efforts to find early-enriched mantle components in Isua have so far been unsuccessful. Here we show that the signature of the Hadean enriched reservoir, complementary to the depleted reservoir in Isua, is recorded in 3.4-Gyr-old mafic dykes intruding into the Early Archaean rocks. Five out of seven dykes carry (142)Nd deficits compared to the terrestrial Nd standard, with three samples yielding resolvable deficits down to -10.6 parts per million. The enriched component that we report here could have been a mantle reservoir that differentiated owing to the crystallization of a magma ocean, or could represent a mafic proto-crust that separated from the mantle more than 4.47 Gyr ago. Our results testify to the existence of an enriched component in the Hadean, and may suggest that the southwest Greenland mantle preserved early-formed heterogeneities until at least 3.4 Gyr ago.

  7. Tilting and transpression of an Archaean anorthosite in northern Ontario

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.; Lagroix, France; King, David

    1998-08-01

    An Archaean anorthosite complex crops out over more than 300 km 2 at the junction between an Archaean metasedimentary accretionary prism (Quetico Belt) and a volcanic greenstone terrain to the north (Wabigoon Belt). The anorthosite is feebly deformed and weakly foliated. However, anisotropies of low field susceptibility (AMS) and anhysteretic remanence (AARM) define consistent magnetic fabric directions extending over subareas >25 km 2 in extent. Whereas magnetic fabrics cannot define strain magnitudes, they normally provide reliable indications of finite strain orientations, even where the fabrics developed by stress-controlled nucleation during a progressive noncoaxial strain history. The field schistosity S 1, being the oldest foliation, rotated closest to the shear plane. AMS foliation due to preferred crystallographic orientation of silicates and pyrrhotite as well as preferred dimensional orientation of magnetite lies at a greater angle to the shear plane; because it formed late then S 1 had less time to rotate. The few measurements of the youngest AARM foliation caused by magnetite and pyrrhotite suggest that it may lie at a still greater angle to the shear plane. Thus, S 1 and succeeding magnetic foliations provide a cryptic shear-sense indicator. They reveal relative motions along the terrain boundary that include transpression due to NW-SE shortening causing dextral E-W shear with a north-side-up component. Palaeomagnetic data confirm a progressive northwards steepening of the anorthosite sills that is consistent with northwards subduction of the accretionary prism to the south.

  8. Mantle hydrous-fluid interaction with Archaean granite.

    NASA Astrophysics Data System (ADS)

    Słaby, E.; Martin, H.; Hamada, M.; Śmigielski, M.; Domonik, A.; Götze, J.; Hoefs, J.; Hałas, S.; Simon, K.; Devidal, J.-L.; Moyen, J.-F.; Jayananda, M.

    2012-04-01

    Water content/species in alkali feldspars from late Archaean Closepet igneous bodies as well as growth and re-growth textures, trace element and oxygen isotope composition have been studied (Słaby et al., 2011). Both processes growth and re-growth are deterministic, however they differ showing increasing persistency in element behaviour during interaction with fluids. The re-growth process fertilized domains and didn't change their oxygen-isotope signature. Water speciation showed persistent behaviour during heating at least up to 600oC. Carbonate crystals with mantle isotope signature are associated with the recrystallized feldspar domains. Fluid-affected domains in apatite provide evidence of halide exchange. The data testify that the observed recrystallization was a high-temperature reaction with fertilized, halide-rich H2O-CO2 mantle-derived fluids of high water activity. A wet mantle being able to generate hydrous plumes, which appear to be hotter during the Archean in comparison to the present time is supposed by Shimizu et al. (2001). Usually hot fluids, which can be strongly carbonic, precede asthenospheric mantle upwelling. They are supposed to be parental to most recognized compositions, which can be derived by their immiscible separation into saline aqueous-silicic and carbonatitic members (Klein-BenDavid et al., 2007). The aqueous fractions are halogen-rich with a significant proportion of CO2. Both admixed fractions are supposed to be fertile. The Closepet granite emplaced in a major shear zone that delimitates two different terrains. Generally such shear zones, at many places, are supposed to be rooted deep into the mantle. The drain, that favoured and controlled magma ascent and emplacement, seemed to remain efficient after granite crystallization. In the southern part of the Closepet batholiths an evidence of intensive interaction of a lower crust fluid (of high CO2 activity) is provided by the extensive charnockitization of amphibolite facies (St

  9. Sink or swim? Geodynamic and petrological model constraints on the fate of Archaean primary crust

    NASA Astrophysics Data System (ADS)

    Kaus, B.; Johnson, T.; Brown, M.; VanTongeren, J. A.

    2013-12-01

    Ambient mantle potential temperatures in the Archaean were significantly higher than 1500 °C, leading to a high percent of melting and generating thick MgO-rich primary crust underlain by highly residual mantle. However, the preserved volume of this crust is low suggesting much of it was recycled. Here we couple calculated phase equilibria for hydrated and anhydrous low to high MgO crust compositions and their complementary mantle residues with 2-D numerical geodynamic models to investigate lithosphere dynamics in the early Earth. We show that, with increasing ambient mantle potential temperature, the density of primary crust increases more dramatically than the density of residual mantle decreases and the base of MgO-rich primary crust becomes gravitationally unstable with respect to the underlying mantle even when fully hydrated. To study this process we use geodynamic models that include the effects of melt extraction, crust formation and depletion of the mantle in combination with laboratory-constrained dislocation and diffusion creep rheologies for the mantle. The models show that the base of the gravitationally unstable lithosphere delaminates through relatively small-scale Rayleigh-Taylor instabilities, but only if the viscosity of the mantle lithosphere is sufficiently low. Thickening of the crust above upwelling mantle and heating at the base of the crust are the main mechanisms that trigger the delamination process. Scaling laws were developed that are in good agreement with the numerical simulations and show that the key parameters that control the instability are the density contrast between crust and underlying mantle lithosphere, the thickness of the unstable layer and the effective viscosity of the upper mantle. Depending on uncertainties in the melting relations and rheology (hydrous or anhydrous) of the mantle, this process is shown to efficiently recycle the crust above potential temperatures of 1550-1600 °C. However, below these temperatures

  10. Generation of continental crust in the northern part of the Borborema Province, northeastern Brazil, from Archaean to Neoproterozoic

    NASA Astrophysics Data System (ADS)

    de Souza, Zorano Sérgio; Kalsbeek, Feiko; Deng, Xiao-Dong; Frei, Robert; Kokfelt, Thomas Find; Dantas, Elton Luiz; Li, Jian-Wei; Pimentel, Márcio Martins; Galindo, Antonio Carlos

    2016-07-01

    (TZ). Early Neoproterozoic volcanism at 1091 Ma, and A-type plutonism, from 920 to 775 Ma, mark the intracontinental magmatism in the TZ. In the Seridó Domain, the Late Neoproterozoic registers several events of plutonism, at 600-593, 575-560, 548-533, 528-510, 495-450 Ma. These rocks cover ca. 15% of the area, while Neoproterozoic supracrustal rocks cover ca. 30%. The most important magmatic event is that at 575 Ma, consistent with the peak of widespread transpression and synchronous high temperature metamorphism. The Neoproterozoic rocks are mostly K-enriched alkaline or transitional to calc-alkaline. Inherited Archaean and Palaeoproterozoic zircons and Nd model ages, as well as moderate to strongly negative (-21 to -9) epsilon Nd, and persistent negative anomalies for Ta-Nb, Ti and P indicate significant crustal contributions in their genesis. While a convergent setting (subduction zone) could explain the Archaean and Palaeoproterozoic units, this is not so for the Neoproterozoic rocks which mimic the geochemical and isotopic features of the older sources. In the study area, the peak of juvenile accretion (mantle derived magmas) took place in the Archaean (3.4-2.7 Ga) and Palaeproterozoic (2.4-2.11 Ga), whereas crustal recycling predominated in the Neoproterozoic.

  11. Evidence of Meso-Archaean subduction from the Torckler-Tango Layered Complex, Rauer Group, Prydz bay, East Antarctica

    NASA Astrophysics Data System (ADS)

    McCallum, C. A.; Harley, S. L.

    2010-12-01

    The Archaean Torckler Tango Layered complex (TTLC) of the Rauer Group, East Antarctica, consists of a series of elongate mega-boudins that can be traced over a strike length of 7 km, enclosed within and intruded by c. 2.8 Ga homogeneous tonalitic orthogneisses. Despite later granulite facies metamorphism (860-900°C, 0.7 GPa) original igneous structures and layering features of the TTLC are very well preserved. Graded and cross stratified layering is evident, as are load-cast structures and geopetal structures. Isotopic and LILE signatures indicate that crustal contamination has been negligible and that metamorphic disturbances have been minor. As a result, the whole rock chemistry of the TTLC is considered to reflect its igneous protoliths. This whole rock geochemistry is distinctive, with high MgO (av. 15.8 wt%), high Mg# (av. 79.1) low TiO2 (av.< 0.33 wt%), and high SiO2 (av. 52.5 wt%). The TTLC can be subdivided into two geochemical groupings based upon Al2O3 and Cr abundances, which provide clear evidence for the crystal fractionation and accumulation processes active within the complex. Trace-element and REE element ratios show coherent trends. Based on its systematic major element (Al2O3/TiO2 ~40), trace element ratios Ti/Zr vs. Zr (Ti/Zr ~34-59 at Zr ~15-40 ppm), and negative HSFE anomalies, the TTLC is similar in geochemistry to both modern, neo-Proterozoic and Archaean boninitic rocks. Magmatic zircons define an intrusive age for the TTLC of ca. 3280 ± 22 Ma. HSFE ratios, and whole rock Nd isotope ratios recalculated back to this age, are consistent with a juvenile depleted source for the primary magma. The TTLC is therefore interpreted as the intrusive equivalent of a boninite, produced through the shallow melting of refractory mantle and supportive of the operation of subduction-like processes in the early-mid Archaean.

  12. Archaean Greenstone Belt Architecture and Stratigraphy: are Comparisons With Ophiolites and Oceanic Plateaux Valid?

    NASA Astrophysics Data System (ADS)

    Bedard, J. H.; Bleeker, W.; Leclerc, F.

    2005-12-01

    Archaean greenstone belts and coeval plutonic belts (dominated by TTGs, tonalite-tronhjemite-granodiorite), are commonly interpreted to represent assembled fragments of oceanic crust, oceanic plateaux or juvenile arc terranes, variably reworked by Archaean orogenic processes related to the operation of plate tectonics. However, many of the lava successions that have been interpreted to represent accreted oceanic plateaux are demonstrably ensialic, can be correlated over long distances along-strike, have depositional contacts onto older continental crustal rocks, show tholeiitic to calc-alkaline cyclicity, and have isotopic signatures indicating assimilation of older felsic crust. Inferred Archaean ophiolites do not have sheeted dyke complexes or associated mantle rocks, and cannot be proven to be oceanic terranes formed by seafloor-spreading. Archaean supracrustal sequences are typically dominated by tholeiitic to komatiitic lavas, typically interpreted to represent the products of decompression melting of mantle plumes. Subordinate proportions of andesites, dacites and rhyolites also occur, and these, together with the coeval TTGs, are generally interpreted to represent arc magmas. In the context of uniformitarian interpretations, the coeval emplacement of putative arc- and plume-related magmas requires extremely complex geodynamic scenarios. However, the relative rarity of the archetypal convergent margin magma type (andesite) in Archaean sequences, and the absence of Archaean blueschists, ultra-high-pressure terranes, thrust and fold belts, core complexes and ophiolites, along with theoretical arguments against Archaean subduction, together imply that Archaean cratonic crust was not formed through uniformitarian plate-tectonic processes. A simpler interpretation involves soft intraoceanic collisions of thick (30-50km), plume-related, basaltic-komatiitic oceanic plateaux, with ongoing mafic magmatism leading to anatexis of the hydrated plateau base to generate

  13. PGE mineralization in the late Archaean iron-rich mafic-ultramafic Hanumalapur Complex, Karnataka, India

    NASA Astrophysics Data System (ADS)

    Alapieti, T. T.; Devaraju, T. C.; Kaukonen, R. J.

    2008-01-01

    An unusually thick sulfur-poor mineralized zone enriched in platinum-group elements (PGE) is described in the Hanumalapur Complex, Shimoga District, Karnataka State, India. This promising occurrence was discovered in the early 1990s and the best samples at the time of writing have yielded Pt+Pd concentrations in excess of six ppm. The western part of the area concerned belongs to the late Archaean Dharwar Super Group (3000-2500 Ma), while the eastern part is occupied predominantly by a granite-gneiss terrain ˜3000 Ma in age. Ten mafic-ultramafic complexes which host interesting vanadium-bearing titanomagnetite occurrences are encountered in the western part, one of which is the Hanumalapur Complex. The PGE mineralized zone in this complex may be divided into four mineralogically distinctive types, which are, in descending order of PGE content: 1) a silicate-hosted Pd type, 2) a silicate-hosted Pt type, 3) a base-metal sulfide-hosted Pd type, and 4) an oxide-hosted PGE type. The genesis of the mineralization is somewhat unclear at this point of investigation, especially because of complete re-crystallization, but the evidence gathered so far suggests something different than a traditional orthomagmatic model requiring magma mixing processes and resulting in sulfide immiscibility. This is backed-up by the general lack of base metal sulfides in favor of chromite, although pure chlorite-amphibole and chlorite-albite-epidote-amphibole rocks may contain significant PGE concentrations regardless of the amount of chromite. The PGM textures show little evidence of hydrothermal alteration and remobilization, but the PGE mineralogy itself displays some characteristics of fluid action, as it seems that there are some OH-bearing Pt and Pd minerals present.

  14. An Archaean heavy bombardment from a destabilized extension of the asteroid belt.

    PubMed

    Bottke, William F; Vokrouhlický, David; Minton, David; Nesvorný, David; Morbidelli, Alessandro; Brasser, Ramon; Simonson, Bruce; Levison, Harold F

    2012-05-03

    The barrage of comets and asteroids that produced many young lunar basins (craters over 300 kilometres in diameter) has frequently been called the Late Heavy Bombardment (LHB). Many assume the LHB ended about 3.7 to 3.8 billion years (Gyr) ago with the formation of Orientale basin. Evidence for LHB-sized blasts on Earth, however, extend into the Archaean and early Proterozoic eons, in the form of impact spherule beds: globally distributed ejecta layers created by Chicxulub-sized or larger cratering events4. At least seven spherule beds have been found that formed between 3.23 and 3.47 Gyr ago, four between 2.49 and 2.63 Gyr ago, and one between 1.7 and 2.1 Gyr ago. Here we report that the LHB lasted much longer than previously thought, with most late impactors coming from the E belt, an extended and now largely extinct portion of the asteroid belt between 1.7 and 2.1 astronomical units from Earth. This region was destabilized by late giant planet migration. E-belt survivors now make up the high-inclination Hungaria asteroids. Scaling from the observed Hungaria asteroids, we find that E-belt projectiles made about ten lunar basins between 3.7 and 4.1 Gyr ago. They also produced about 15 terrestrial basins between 2.5 and 3.7 Gyr ago, as well as around 70 and four Chicxulub-sized or larger craters on the Earth and Moon, respectively, between 1.7 and 3.7 Gyr ago. These rates reproduce impact spherule bed and lunar crater constraints.

  15. Asteroids and Archaean crustal evolution: Tests of possible genetic links between major mantle/crust melting events and clustered extraterrestrial bombardments

    NASA Technical Reports Server (NTRS)

    Glikson, A. Y.

    1992-01-01

    Since the oldest intact terrestrial rocks of ca. 4.0 Ga and oldest zircon xenocrysts of ca. 4.3 Ga measured to date overlap with the lunar late heavy bombardment, the early Precambrian record requires close reexamination vis a vis the effects of megaimpacts. The identification of microtektite-bearing horizons containing spinals of chondritic chemistry and Ir anomalies in 3.5-3.4-Ga greenstone belts provides the first direct evidence for large-scale Archaean impacts. The Archaean crustal record contains evidence for several major greenstone-granite-forming episodes where deep upwelling and adiabatic fusion of the mantle was accompanied by contemporaneous crustal anatexis. Isotopic age studies suggest evidence for principal age clusters about 3.5, 3.0, and 2.7 (+/- 0.8) Ga, relics of a ca. 3.8-Ga event, and several less well defined episodes. These peak events were accompanied and followed by protracted thermal fluctuations in intracrustal high-grade metamorphic zones. Interpretations of these events in terms of internal dynamics of the Earth are difficult to reconcile with the thermal behavior of silicate rheologies in a continuously convecting mantle regime. A triggering of these episodes by mantle rebound response to intermittent extraterrestrial asteroid impacts is supported by (1) identification of major Archaean impacts from microtektite and distal ejecta horizons marked by Ir anomalies; (2) geochemical and experimental evidence for mantle upwelling, possibly from levels as deep as the transition zone; and (3) catastrophic adiabatic melting required to generate peridotitic komatites. Episodic differentiation/accretion growth of sial consequent on these events is capable of resolving the volume problem that arises from comparisons between modern continental crust and the estimated sial produced by continuous two-stage mantle melting processes. The volume problem is exacerbated by projected high accretion rates under Archaean geotherms. It is suggested that

  16. Modulation of oxygen production in Archaean oceans by episodes of Fe(II) toxicity

    NASA Astrophysics Data System (ADS)

    Swanner, Elizabeth D.; Mloszewska, Aleksandra M.; Cirpka, Olaf A.; Schoenberg, Ronny; Konhauser, Kurt O.; Kappler, Andreas

    2015-02-01

    Oxygen accumulated in the surface waters of the Earth's oceans and atmosphere several hundred million years before the Great Oxidation Event between 2.4 and 2.3 billion years ago. Before the Great Oxidation Event, periods of enhanced submarine volcanism associated with mantle plume events supplied Fe(II) to sea water. These periods generally coincide with the disappearance of indicators of the presence of molecular oxygen in Archaean sedimentary records. The presence of Fe(II) in the water column can lead to oxidative stress in some organisms as a result of reactions between Fe(II) and oxygen that produce reactive oxygen species. Here we test the hypothesis that the upwelling of Fe(II)-rich, anoxic water into the photic zone during the late Archaean subjected oxygenic phototrophic bacteria to Fe(II) toxicity. In laboratory experiments, we found that supplying Fe(II) to the anoxic growth medium housing a common species of planktonic cyanobacteria decreased both the efficiency of oxygenic photosynthesis and their growth rates. We suggest that this occurs because of increasing intracellular concentrations of reactive oxygen species. We use geochemical modelling to show that Fe(II) toxicity in conditions found in the late Archaean photic zone could have substantially inhibited water column oxygen production, thus decreasing fluxes of oxygen to the atmosphere. We therefore propose that the timing of atmospheric oxygenation was controlled by the timing of submarine, plume-type volcanism, with Fe(II) toxicity as the modulating factor.

  17. The dehydration, rehydration and tectonic setting of greenstone belts in a portion of the northern Kaapvaal Craton, South Africa

    NASA Technical Reports Server (NTRS)

    Vanreenen, D. D.; Barton, J. M., Jr.; Roering, C.; Vanschalkwyk, J. C.; Smit, C. A.; Debeer, J. D.; Stettler, E. H.

    1986-01-01

    High-grade gneiss terranes and low-grade granite-greenstone terranes are well known in several Archaean domains. The geological relationship between these different crustal regions, however, is still controversial. One school of thought favors fundamental genetic differences between high-grade and low-grade terranes while others argue for a depth-controlled crustal evolution. The detailed examination of well-exposed Archaean terranes at different metamorphic grades, therefore, is not only an important source of information about the crustal levels exposed, but also is critical to the understanding of the possible tectonic and metamorphic evolution of greenstone belts with time. Three South African greenstone belts are compared.

  18. Earth science: A resolution of the Archaean paradox

    NASA Astrophysics Data System (ADS)

    Moresi, Louis

    2013-09-01

    A model of early Earth, in which heat from the interior is carried to the surface through volcanic heat pipes, suggests that our planet 4 billion years ago had more in common with Jupiter's moon Io than with today's Earth. See Article p.501

  19. High but balanced sedimentation and subsidence rates (Moodies Group, Barberton Greenstone Belt), followed by basin collapse: Implication for Archaean tectonics

    NASA Astrophysics Data System (ADS)

    Heubeck, Christoph; Lowe, Donald R.; Byerly, Gary R.

    2010-05-01

    top of the underlying Fig Tree Group (Schoongezicht Fm.; Byerly et al., 1996), implying that ca. 2000m of Moodies sandstones and subordinate siltstones and conglomerates were deposited in not more than a few (0-6) Ma. Their comparatively low degree of facies variation and lithological change implies a balance between rates of sediment supply and of subsidence, creating thick stacked units. Ferruginous shales and thin BIFs of the upper Moodies Group suggest that background 'Fig-Tree-style' sedimentation continued during Moodies time but was mostly overwhelmed by the apparently brief but massive influx of medium- to coarse-grained quartzose sediment. Because two progressive unconformities, marking Moodies basin uplift and onset of renewed overall BGB shortening, occur only 50 m above this dated unit, they are likely of a similar age and imply that dominant NW-SE-directed shortening in the BGB began shortly after 3230+-6 Ma. The combination of these new data with published information thus suggest that the Moodies Basin formed after 3225+-6 Ma (i.e., at the earliest at 3231) but was already largely filled and began to be deformed by 3231+-6 (i.e., at the latest by 3225). Moodies deposition thus happened geologically nearly instantaneously following the end of Fig Tree volcanism, took very little time and deposited large volumes of sediments on a rapidly subsiding basement just prior to large-scale BGB deformation. REFERENCES Byerly, G.R., Kroner, A., Lowe, D.R., Todt W., Walsh, M.M., 1996, Prolonged magmatism and time constraints for sediment deposition in the early Archean Barberton greenstone belt: Evidence from the Upper Onverwacht and Fig Tree groups: Precambrian Research, 78, p. 125-138. Eriksson, K.A., 1979, Marginal marine depositional processes from the Archaean Moodies Group, Barberton Mountain Land, South Africa: Evidence and significance: Precambrian Res., 8, p. 153-182. Heubeck, C. and Lowe, D.R., 1994, Depositional and tectonic setting of the Archaean

  20. Coupled Fe and S Isotope Evidence for Archaean Microbial Fe(III) and Sulphate Reduction

    NASA Astrophysics Data System (ADS)

    Archer, C.; Vance, D.

    2004-12-01

    The development of transition metal stable isotope geochemistry over recent years, fuelled by advances in analytical technology, has permitted new approaches to established geochemical problems. One such application is the understanding and tracing of early Earth biogeochemistry, with a particular emphasis on the activities of primitive microbial life, where evidence from traditional isotope systems has so far been equivocal. The earliest forms of microbial respiration are thought to involve sulphate or Fe (III) reduction, {e.g. 1,2} or perhaps both, and as such combined Fe-S isotope systems provide a potentially powerful tool to trace these processes. Here we report a Zn-Fe-S data set from sulphide and pyrite grains from the 2.7 Ga Belingwe Belt, associated with sulphate reducing microbial communities. Analyses of individual mm size sulphide and pyrite grains show large depletions of light Fe isotopes, as well as a large variation in Fe isotope composition with a range of -0.7 to -2.7 \\permil. Furthermore these variations are correlated with depletions in light S isotopes measured from the same samples, which range in isotope composition from -3 to -18 \\permil 3. Zn isotopes also show significant positive fractionations, up to 0.8\\permil, particularly in organic rich black shales. The most striking feature of our dataset is a tight correlation between sulphur and iron isotopes. This relationship is most readily explained in terms of a reducing sedimentary environment. In modern anoxic sediments dissimilatory bacterial Fe (III) reduction, and further down the sediment column, sulphate reduction produce solubilised light Fe2+ and S2-, which in solution together immediately react to form isotopically depleted sulphides and ultimately pyrite. Experimental constraints4 and measurements of natural pyrite from modern sedimentary settings (S. Severmann, pers comm) demonstrate that the solid sulphide produced is light in Fe. We will present a quantitative diagenetic

  1. Anorthosites and anorthosites: Contrasting plagioclase-rich rocks in the Archaean and Proterozoic

    SciTech Connect

    Owens, B.E. . Dept. of Earth Planetary Sciences)

    1993-03-01

    Anorthosites -- rocks consisting predominantly of plagioclase feldspar -- have figured prominently in at least two distinct intervals of Earth history: the late-Archaean and mid-Proterozoic. Archaean anorthosites (AA) are a key component of high-grade gneiss terranes, where they typically form laterally extensive deformed sheets or sills up to a km thick. In contrast, Proterozoic anorthosites (PA) form plutons or plutonic complexes, and are most abundant in a quasi-continuous belt across NE N. America. In addition to these temporal and structural contrasts, AA and PA display markedly different mineralogical and geochemical properties, including, respectively: (1) equant plagioclase megacrysts vs. tabular megacrysts; (2) highly calcic compositions vs. intermediate to alkalic compositions; (3) amphibole vs. olivine or orthopyroxene as the dominant mafic mineral; (4) the presence of chromite, locally in ore-grade layers vs. massive, cross-cutting Fe-Ti oxide ores; (5) low levels of Sr and Ba vs. high to extreme levels; (6) high levels of ferromagnesian trace elements vs. low levels; (7) Ga/Al values typical of basaltic plagioclase vs. much lower values; and (8) moderately vs. extremely fractionated REE patterns. Given these contrasts, it appears that the only property AA and PA share is their plag-rich nature, suggesting that there must be more than one process (and probably multiple processes) capable of producing anorthosite.

  2. A Large-Magnitude Biological Source of H2 to the Archaean Atmosphere?

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Bebout, Brad M.; DesMarais, David J.; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    The appearance of photosynthetic microbial communities on Earth was a critical juncture in the chemical evolution of the oceans and atmosphere. The use of sunlight as an energy source frees life from a dependence on geochemical energy sources; global biospheric productivity, as well as the biological influence on planetary chemistry, can be greatly enhanced as a result. To understand the potential biogeochemical impacts of the transition to a photosynthetic biosphere, we examined chemical cycling in potential modern analogs of these Archaean photosynthetic communities - microbial mats from Baja California, Mexico. The primary role of photosynthetic members in the mat community is to extract reducing power (electrons) from water and use it to 'fix' carbon dioxide into organic carbon (biomolecules); however, when exposed to a simulated Archaean atmosphere of very low oxygen content, these organisms divert a substantial fraction of the captured reducing power into the production of molecular hydrogen. Globally, this mechanism of hydrogen production could have outstripped geologic sources by 2 to 4 orders of magnitude. A large-magnitude H2 flux to the environment offers the potential to enhance the global distribution and productivity of H2-consuming organisms, and also to contribute significantly to oxidation of the oceans and atmosphere by via escape to space.

  3. Witwatersrand gold deposits formed by volcanic rain, anoxic rivers and Archaean life

    NASA Astrophysics Data System (ADS)

    Heinrich, Christoph A.

    2015-03-01

    The Witwatersrand Basin in South Africa is one of the best-preserved records of fluvial sedimentation on an Archaean continent. The basin hosts the worlds biggest gold resource in thin pebble beds, but the process for gold enrichment is debated. Mechanical accumulation of gold particles from flowing river water is the prevailing hypothesis, yet there is evidence for hydrothermal mobilization of gold by fluids invading the metasedimentary rocks after their burial. Earth's atmosphere three billion years ago was oxygen free, but already sustained some of the oldest microbial life on land. Here I use thermodynamic modelling and mass-balance calculations to show that these conditions could have led to the chemical transport and precipitation of gold in anoxic surface waters, reconciling the evidence for fluvial deposition with evidence for hydrothermal-like chemical reactions. I suggest that the release of sulphurous gases from large volcanic eruptions created acid rain that enabled the dissolution and transport of gold in surface waters as sulphur complexes. Precipitation of the richest gold deposits could have been triggered by chemical reduction of the dissolved gold onto organic material in shallow lakes and pools. I conclude that the Witwatersrand gold could have formed only during the Archaean, after the emergence of continental life but before the rise of oxygen in the Earth's atmosphere.

  4. Evidence for recycled Archaean oceanic mantle lithosphere in the Azores plume.

    PubMed

    Schaefer, Bruce F; Turner, Simon; Parkinson, Ian; Rogers, Nick; Hawkesworth, Chris

    2002-11-21

    The compositional differences between mid-ocean-ridge and ocean-island basalts place important constraints on the form of mantle convection. Also, it is thought that the scale and nature of heterogeneities within plumes and the degree to which heterogeneous material endures within the mantle might be reflected in spatial variations of basalt composition observed at the Earth's surface. Here we report osmium isotope data on lavas from a transect across the Azores archipelago which vary in a symmetrical pattern across what is thought to be a mantle plume. Many of the lavas from the centre of the plume have lower 187Os/188Os ratios than most ocean-island basalts and some extend to subchondritic 187Os/188Os ratios-lower than any yet reported from ocean-island basalts. These low ratios require derivation from a depleted, harzburgitic mantle, consistent with the low-iron signature of the Azores plume. Rhenium-depletion model ages extend to 2.5 Gyr, and we infer that the osmium isotope signature is unlikely to be derived from Iberian subcontinental lithospheric mantle. Instead, we interpret the osmium isotope signature as having a deep origin and infer that it may be recycled, Archaean oceanic mantle lithosphere that has delaminated from its overlying oceanic crust. If correct, our data provide evidence for deep mantle subduction and storage of oceanic mantle lithosphere during the Archaean era.

  5. Late-Archaean Potassic Granite from the Bundelkhand Craton, Central India

    NASA Astrophysics Data System (ADS)

    Sarkar, Saheli; Saha, Lopamudra; Nasipuri, Pritam; Pati, Jayanta Kumar; Patole, Vishal

    2014-05-01

    Late-Archaean granitoids, show wide range of compositional variation: (i) TTG like granitoids with strongly fractionated REE patterns, which can be both Na-rich and K-Mg-rich (Sanukitoids) (ii) K-rich, Mg-poor biotite granites with less fractionated REE patterns and showing negative Eu-anomalies (type area, the Closepet Granite, Eastern Dharwar Craton, India). Amongst them Late-Archaean Sanukitoid or K-rich Closepet-type granitoids are most widely reported from the Archaean Cratons world-wide: Superior Province, Canada, Pilbara Craton, Yilgarn Craton, Antarctica, Limpopo Belt, Dharwar Craton. Several models proposed so far for the origin of these granitoids mostly include partial melting of hydrated basalts, reaction of slab melts with mantle wedge peridotites, re-melting of an enriched mantle and then mixing of the resulting melt with the anatectic melt generated during the melting of continental crust in subduction zone settings. The Closepet-type potassic biotite-rich granites were mostly produced by re-melting of TTG-like continental basements most likely in a subduction zone setting. Most of the proposed models suggest such partial melting to have taken place in garnet-stability field and some in orthopyroxene-stability field. In this study we report late-Archaean (~2.61-2.5 Ga) potassic granite from the Bundelkhand Craton in central India. The Late-Archaean granitoids recorded from the craton are intrusive into the high-grade supracrustal rocks of the craton. They are classified as coarse grained grey, pink porphyritic granite, medium granied pink granite, granite porphyry and fine-grained pink granite. The supracrustal rocks of the craton have been metamorphosed at ~2.78 Ga under high-pressure conditions (~17-18 kbar)- medium temperature (600ºC) in a subduction zone setting. The intrusions of the granitoids at ~2.6-2.5 Ga mark the stability of the craton. The pink-porphyritic granite studied here preserves plagioclase-potash feldspar

  6. Raindrop imprints in the Late Archaean-Early Proterozoic Ventersdorp Supergroup, South Africa

    NASA Astrophysics Data System (ADS)

    van der Westhuizen, W. A.; Grobler, N. J.; Loock, J. C.; Tordiffe, E. A. W.

    1989-02-01

    Well preserved raindrop imprints occur in Ventersdorp rocks of Randian age (±2.7 Ga) on mudflakes at five different stratigraphic levels in a sequence which consists of alternating beds of arkose and tuff. The raindrop imprints indicate that an atmosphere did exist, and that the arkose was deposited in an environment periodically exposed to the atmosphere. These are, as far as is known, the oldest raindrop craters ever to be described. Special conditions governing their formation and preservation are given.

  7. A fresh look at the fossil evidence for early Archaean cellular life

    PubMed Central

    Brasier, Martin; McLoughlin, Nicola; Green, Owen; Wacey, David

    2006-01-01

    The rock record provides us with unique evidence for testing models as to when and where cellular life first appeared on Earth. Its study, however, requires caution. The biogenicity of stromatolites and ‘microfossils’ older than 3.0 Gyr should not be accepted without critical analysis of morphospace and context, using multiple modern techniques, plus rejection of alternative non-biological (null) hypotheses. The previous view that the co-occurrence of biology-like morphology and carbonaceous chemistry in ancient, microfossil-like objects is a presumptive indicator of biogenicity is not enough. As with the famous Martian microfossils, we need to ask not ‘what do these structures remind us of?’, but ‘what are these structures?’ Earth's oldest putative ‘microfossil’ assemblages within 3.4–3.5 Gyr carbonaceous cherts, such as the Apex Chert, are likewise self-organizing structures that do not pass tests for biogenicity. There is a preservational paradox in the fossil record prior to ca 2.7 Gyr: suitable rocks (e.g. isotopically light carbonaceous cherts) are widely present, but signals of life are enigmatic and hard to decipher. One new approach includes detailed mapping of well-preserved sandstone grains in the ca 3.4 Gyr Strelley Pool Chert. These can contain endolithic microtubes showing syngenicity, grain selectivity and several levels of geochemical processing. Preliminary studies invite comparison with a class of ambient inclusion trails of putative microbial origin and with the activities of modern anaerobic proteobacteria and volcanic glass euendoliths. PMID:16754605

  8. Deep origin and hot melting of an Archaean orogenic peridotite massif in Norway.

    PubMed

    Spengler, Dirk; van Roermund, Herman L M; Drury, Martyn R; Ottolini, Luisa; Mason, Paul R D; Davies, Gareth R

    2006-04-13

    The buoyancy and strength of sub-continental lithospheric mantle is thought to protect the oldest continental crust (cratons) from destruction by plate tectonic processes. The exact origin of the lithosphere below cratons is controversial, but seems clearly to be a residue remaining after the extraction of large amounts of melt. Models to explain highly melt-depleted but garnet-bearing rock compositions require multi-stage processes with garnet and clinopyroxene possibly of secondary origin. Here we report on orogenic peridotites (fragments of cratonic mantle incorporated into the crust during continent-continent plate collision) from Otrøy, western Norway. We show that the peridotites underwent extensive melting during upwelling from depths of 350 kilometres or more, forming a garnet-bearing cratonic root in a single melting event. These peridotites appear to be the residue after Archaean aluminium depleted komatiite magmatism.

  9. Why Archaean TTG cannot be generated by MORB melting in subduction zones

    NASA Astrophysics Data System (ADS)

    Martin, Hervé; Moyen, Jean-François; Guitreau, Martin; Blichert-Toft, Janne; Le Pennec, Jean-Luc

    2014-06-01

    Until recently it was assumed that the Archaean continental crust (made of TTGs: tonalites, trondhjemites, and granodiorites) was generated through partial melting of MORB-like basalts in hot subduction environments, where the subducted oceanic crust melted at high pressure, leaving a garnet-bearing amphibolitic or eclogitic residue. However, recent geochemical models as well as basalt melting experiments have precluded MORB as a plausible source for TTGs. Rather, geochemical and experimental evidences indicate that formation of TTG required a LILE-enriched source, similar to oceanic plateau basalts. Moreover, subduction is a continuous process, while continental growth is episodic. Several “super-growth events” have been identified at ~ 4.2, ~ 3.8, ~ 3.2, ~ 2.7, ~ 1.8, ~ 1.1, and ~ 0.5 Ga, which is inconsistent with the regular pattern that would be expected from a subduction-driven process. In order to account for this periodicity, it has been proposed that, as subduction proceeds, descending residual slabs accumulate at the 660-km seismic discontinuity. When stored oceanic crust exceeds a certain mass threshold, it rapidly sinks into the mantle as a cold avalanche, which induces the ascent of mantle plumes that in turn produce large amounts of magmas resulting in oceanic plateaus. However, melting at the base of thick oceanic plateaus does not appear to be a realistic process that can account for TTG genesis. Modern oceanic plateaus contain only small volumes (≤ 5%) of felsic magmas generally formed by high degrees of fractional crystallization of basaltic magmas. The composition of these felsic magmas drastically differs from that of TTGs. In Iceland, the interaction between a mantle plume and the mid-Atlantic ridge gives rise to an anomalously (Archaean-like) high geothermal gradient resulting in thick basaltic crust able to melt at shallow depth. Even in this favorable context though, the characteristic Archaean TTG trace element signature is not being

  10. Archaean zircons in Miocene oceanic hotspot rocks establish ancient continental crust beneath Mauritius

    NASA Astrophysics Data System (ADS)

    Ashwal, Lewis D.; Wiedenbeck, Michael; Torsvik, Trond H.

    2017-01-01

    A fragment of continental crust has been postulated to underlie the young plume-related lavas of the Indian Ocean island of Mauritius based on the recovery of Proterozoic zircons from basaltic beach sands. Here we document the first U-Pb zircon ages recovered directly from 5.7 Ma Mauritian trachytic rocks. We identified concordant Archaean xenocrystic zircons ranging in age between 2.5 and 3.0 Ga within a trachyte plug that crosscuts Older Series plume-related basalts of Mauritius. Our results demonstrate the existence of ancient continental crust beneath Mauritius; based on the entire spectrum of U-Pb ages for old Mauritian zircons, we demonstrate that this ancient crust is of central-east Madagascar affinity, which is presently located ~700 km west of Mauritius. This makes possible a detailed reconstruction of Mauritius and other Mauritian continental fragments, which once formed part of the ancient nucleus of Madagascar and southern India.

  11. A Proposal for Formation of Archaean Stromatolites before the Advent of Oxygenic Photosynthesis

    PubMed Central

    Allen, John F.

    2016-01-01

    Stromatolites are solid, laminar structures of biological origin. Living examples are sparsely distributed and formed by cyanobacteria, which are oxygenic phototrophs. However, stromatolites were abundant between 3.4 and 2.4 Gyr, prior to the advent of cyanobacteria and oxygenic photosynthesis. Here I propose that many Archaean stromatolites were seeded at points of efflux of hydrogen sulfide from hydrothermal fields into shallow water, while their laminar composition arose from alternating modes of strictly anoxygenic photosynthetic metabolism. These changes were a redox regulatory response of gene expression to changing hydrogen sulfide concentration, which fluctuated with intermittent dilution by tidal action or by rainfall into surface waters. The proposed redox switch between modes of metabolism deposited sequential microbial mats. These mats gave rise to alternating carbonate sediments predicted to retain evidence of their origin in differing ratios of isotopes of carbon and sulfur and in organic content. The mats may have arisen either by replacement of microbial populations or by continuous lineages of protocyanobacteria in which a redox genetic switch selected between Types I and II photosynthetic reaction centers, and thus between photolithoautotrophic and photoorganoheterotrophic metabolism. In the latter case, and by 2.4 Gyr at the latest, a mutation had disabled the redox genetic switch to give simultaneous constitutive expression of both Types I and II reaction centers, and thus to the ability to extract electrons from manganese and then water. By this simple step, the first cyanobacterium had the dramatic advantage of emancipation from limiting supplies of inorganic electron donors, produced free molecular oxygen as a waste product, and initiated the Great Oxidation Event in Earth’s history at the transition from the Archaean to the Paleoproterozoic. PMID:27895626

  12. Oxidation state of iron in komatiitic melt inclusions indicates hot Archaean mantle

    SciTech Connect

    Berry, A.J.; Danyushevsky, L.; O'Neill, H.C.; Newville, M.; Sutton, S.R.

    2008-10-16

    Komatiites are volcanic rocks mainly of Archaean age that formed by unusually high degrees of melting of mantle peridotite. Their origin is controversial and has been attributed to either anhydrous melting of anomalously hot mantle or hydrous melting at temperatures only modestly greater than those found today. Here we determine the original Fe{sup 3+}/{Sigma}Fe ratio of 2.7-Gyr-old komatiitic magma from Belingwe, Zimbabwe, preserved as melt inclusions in olivine, to be 0.10 {+-} 0.02, using iron K-edge X-ray absorption near-edge structure spectroscopy. This value is consistent with near-anhydrous melting of a source with a similar oxidation state to the source of present-day mid-ocean-ridge basalt. Furthermore, this low Fe{sup 3+}/{Sigma}Fe value, together with a water content of only 0.2--0.3 wt%, excludes the possibility that the trapped melt contained significantly more water that was subsequently lost from the inclusions by reduction to H{sub 2} and diffusion. Loss of only 1.5 wt% water by this mechanism would have resulted in complete oxidation of iron (that is, the Fe{sup 3+}/{Sigma}Fe ratio would be {approx}1). There is also no petrographic evidence for the loss of molecular water. Our results support the identification of the Belingwe komatiite as a product of high mantle temperatures ({approx}1,700 C), rather than melting under hydrous conditions (3--5-wt% water), confirming the existence of anomalously hot mantle in the Archaean era.

  13. Recoupling the Nd-Hf isotope record of the early Earth? Evidence from the Pilbara craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Kemp, T.; Vervoort, J. D.; Smithies, H.; Hickman, A.; Van Kranendonk, M. J.

    2011-12-01

    Geochemical evidence has long been used to argue for mass exchange between the earliest terrestrial crust and mantle, yet the apparently decoupled Nd-Hf isotope record preserved by the oldest rocks implicates differentiation processes unlike those associated with modern plate tectonics. This debate has, however, been staged in areas of great geological complexity, where the veracity of whole rock radiogenic isotope data is questionable, or involved inferences from ancient detrital zircons whose provenance is enigmatic. Here, we report the Nd and Hf isotope compositions of samples from the Paleoarchaean to Neoarchaean Pilbara craton, a superbly preserved, archetypal granite-greenstone belt in Western Australia. We have analyzed Nd-Hf isotopes in mafic rocks and Hf isotopes in zircons of interleaved felsic units to monitor the effects of whole-rock isotope disturbance and to track the evolution of crust and mantle reservoirs. Mafic samples range from ~3.52 Ga komatiites and basalts of the Warrawoona Group, whose eruption is attributed to mantle plume activity, through to younger (3.12-2.95 Ga) basalts, calc-alkaline basalts and boninites similar to those of intra-oceanic volcanic arcs. Felsic rocks (3.48-2.85 Ga) include dacite and rhyolite units from the greenstone belts and their coeval plutonic counterparts in the granitic complexes. Additionally, the Hf isotope composition of the oldest (3.65-3.73 Ga) detrital zircons from intra-cratonic basins were measured to explore the pre-3.5 Ga history of the craton and to test whether this developed on an older, but unexposed, continental substrate. Results are summarized as follows. Collectively, the Pilbara samples exhibit greater variability in initial 143Nd/144Nd than in 176Hf/177Hf, as has been observed in other ancient Archaean terranes (J. Vervoort et al. Nature 379,1996). Epsilon Hf values of the mafic samples increase from +1.1 at 3.53 Ga to +3.0 at 3.2 Ga, before falling sharply to -3.3 by 2.95 Ga. Epsilon Nd

  14. 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)

    Shirey, Steven B.; Hanson, Gilbert N.

    1986-01-01

    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.

  15. Late-orogenic basins in the Archaean Superior Province, Canada: characteristics and inferences

    NASA Astrophysics Data System (ADS)

    Mueller, W. U.; Corcoran, P. L.

    1998-09-01

    The late-orogenic Archaean Duparquet, Kirkland and Stormy basins of the Canadian Superior Province are characterized by bounding crustal-scale faults and abundant porphyry stock emplacement. Lava flows and pyroclastic deposits are restricted to the Kirkland and Stormy basins, and coarse clastic detritus characterizes the Duparquet basin. Seven distinct lithofacies are identified: (1) mafic volcanic, (2) felsic volcanic, (3) pyroclastic, (4) volcaniclastic, (5) conglomerate-sandstone, (6) sandstone-argillite (± conglomerate), and (7) argillite-sandstone (± tuffaceous sandstone). The mafic and felsic volcanic lithofacies represent effusive lava flows, the pyroclastic lithofacies is formed of subaerial surge and airfall deposits and the volcaniclastic lithofacies is composed of reworked volcanic debris. The conglomerate-sandstone lithofacies is interpreted as alluvial fan, fan delta or proximal braided stream deposits, whereas the sandstone-argillite lithofacies is consistent with sandy-dominated flood- or braidplain deposits. A dominantly shallow-water lacustrine setting is inferred for the argillite-sandstone lithofacies. These different lithofacies record the basin history and can be used to identify basin-forming processes. Lithofacies stacking and rapid lateral changes of lithological units in conjunction with interformational unconformities and basin margin faults suggest tectonically induced sedimentation. Volcanism can also influence basin evolution and the delicate balance between erosion, sedimentation, and prevalent transport processes is affected by volcanic input. Catastrophic influx of pyroclastic material facilitated mass-wasting processes and formation of non-confined hyperconcentrated flood flow deposits account for local congestion of alluvial or fluvial dispersal patterns. Confined stream flow processes govern sedimentation during intravolcanic phases or prominent tectonic uplift. In addition, climate which controls the weathering processes

  16. Crustal reflectivity near the Archaean-Proterozoic boundary in northern Sweden and implications for the tectonic evolution of the area

    NASA Astrophysics Data System (ADS)

    Juhlin, C.; Elming, S.-Å.; Mellqvist, C.; Öhlander, B.; Weihed, P.; Wikström, A.

    2002-07-01

    Sm-Nd isotope ratios of 1.9-1.8 Ga granitoids delineate the Archaean-Proterozoic boundary in northern Sweden, an important feature in the Fennoscandian Shield. The boundary strikes approximately WNW-ESE and is defined as a c. 20 km wide zone with juvenile Palaeoproterozoic rocks to the SSW and Archaean and Proterozoic rocks, derived to a large extent from Archaean sources, to the NNE. It therefore constitutes the strongly reworked margin of the old Archaean craton. Extrapolation of the boundary offshore into the Bothnian Bay and correlation with the marine reflection seismic BABEL Lines 2 and 3/4 indicates that the boundary dips to the south-southwest, consistent with interpretation of the Sm-Nd data. In order to tie the BABEL results with onshore surface geology and obtain detailed images of the uppermost crust a short (30 km of subsurface coverage) pilot profile was acquired in the Luleå area of northern Sweden during August 1999. The profile consisted of a high-resolution shallow component (1 kg shots) and a lower-resolution deep component (12 kg shots). Both components image most of the reflective crust, with the deep component providing a better image below 10 s. Comparison of signal penetration curves with data acquired over the Trans-Scandinavian Igneous Belt (a large batholith) indicate the transparent nature of the crust there to be caused by geological factors, not acquisition parameters. Lower crustal reflectivity patterns on the Luleå test profile are similar to those observed on the BABEL lines, suggesting the same lower crust onshore as offshore. Interpreted Archaean reflective upper crust in the NE extends below more transparent Proterozoic crust in the SW. This transparent crust contains a number of high-amplitude reflectors that may represent shear zones and/or mafic rock within granite intrusions. A marked boundary in the magnetic field in the SW has been interpreted as being the result of a gently west-dipping contact zone between meta

  17. High-resolution magnetotelluric studies of the Archaean-Proterozoic border zone in the Fennoscandian Shield, Finland

    NASA Astrophysics Data System (ADS)

    Vaittinen, K.; Korja, T.; Kaikkonen, P.; Lahti, I.; Smirnov, M. Yu.

    2012-03-01

    The Archaean-Proterozoic collisional zone is a complex mixture of the Archaean complexes [e.g. Iisalmi Complex (IC)], Proterozoic supracrustal belts [e.g. Kainuu Belt (KB) and Savo Belt (SB)] and oceanic arc lithologies in the central Fennoscandian Shield. The zone was formed in the Savo orogeny when the Keitele microcontinent collided with the Archaean Karelian craton in the Palaeoproterozoic time. The crustal architecture of this palaeosuture is studied using new broad-band magnetotelluric data from 104 sites. 2-D conductivity models across the border zone between the Palaeoproterozoic Svecofennian Domain and the Archaean Karelian province are constrained using the recent, partly collocated reflection seismic data from the Finnish Reflection Experiment (FIRE). Dimensionality analyses, in particular the Q-function analysis, show that magnetotelluric data represent reasonably well regional 2-D structure at periods <100 s, which is the longest period used in this study. Strike determinations gave a stable strike of N15W. For the inversions, the data are projected into three parallel profiles with an azimuth of N75E. The determinant inversion is selected as the most suitable method for the data set. Especially the phase data are useable only from the determinant since one of the polarizations have the out-of-quadrant phase at several sites. The interpreted final, geological more appropriate models, where smoother thick conductive areas are replaced by thinner layers, are constructed from the results of the unconstrained smooth inversions with the help of forward modelling, synthetic and prior model inversions and reflection seismic models. The two major sets of crustal conductors are identified. They have an opposite dip and together they form a bowl-shaped conductor. In the west, the eastward dipping SB conductors are located at the bottom of the formation underlain by the Keitele microcontinent. The SB conductors extend to the east possibly cutting the westward

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

    NASA Astrophysics Data System (ADS)

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

    1996-01-01

    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.

  19. A Field Trip to the Archaean in Search of Darwin’s Warm Little Pond

    PubMed Central

    Damer, Bruce

    2016-01-01

    Charles Darwin’s original intuition that life began in a “warm little pond” has for the last three decades been eclipsed by a focus on marine hydrothermal vents as a venue for abiogenesis. However, thermodynamic barriers to polymerization of key molecular building blocks and the difficulty of forming stable membranous compartments in seawater suggest that Darwin’s original insight should be reconsidered. I will introduce the terrestrial origin of life hypothesis, which combines field observations and laboratory results to provide a novel and testable model in which life begins as protocells assembling in inland fresh water hydrothermal fields. Hydrothermal fields are associated with volcanic landmasses resembling Hawaii and Iceland today and could plausibly have existed on similar land masses rising out of Earth’s first oceans. I will report on a field trip to the living and ancient stromatolite fossil localities of Western Australia, which provided key insights into how life may have emerged in Archaean, fluctuating fresh water hydrothermal pools, geological evidence for which has recently been discovered. Laboratory experimentation and fieldwork are providing mounting evidence that such sites have properties that are conducive to polymerization reactions and generation of membrane-bounded protocells. I will build on the previously developed coupled phases scenario, unifying the chemical and geological frameworks and proposing that a hydrogel of stable, communally supported protocells will emerge as a candidate Woese progenote, the distant common ancestor of microbial communities so abundant in the earliest fossil record. PMID:27231942

  20. Archaean zircons in Miocene oceanic hotspot rocks establish ancient continental crust beneath Mauritius

    PubMed Central

    Ashwal, Lewis D.; Wiedenbeck, Michael; Torsvik, Trond H.

    2017-01-01

    A fragment of continental crust has been postulated to underlie the young plume-related lavas of the Indian Ocean island of Mauritius based on the recovery of Proterozoic zircons from basaltic beach sands. Here we document the first U–Pb zircon ages recovered directly from 5.7 Ma Mauritian trachytic rocks. We identified concordant Archaean xenocrystic zircons ranging in age between 2.5 and 3.0 Ga within a trachyte plug that crosscuts Older Series plume-related basalts of Mauritius. Our results demonstrate the existence of ancient continental crust beneath Mauritius; based on the entire spectrum of U–Pb ages for old Mauritian zircons, we demonstrate that this ancient crust is of central-east Madagascar affinity, which is presently located ∼700 km west of Mauritius. This makes possible a detailed reconstruction of Mauritius and other Mauritian continental fragments, which once formed part of the ancient nucleus of Madagascar and southern India. PMID:28140395

  1. Archaean zircons in Miocene oceanic hotspot rocks establish ancient continental crust beneath Mauritius.

    PubMed

    Ashwal, Lewis D; Wiedenbeck, Michael; Torsvik, Trond H

    2017-01-31

    A fragment of continental crust has been postulated to underlie the young plume-related lavas of the Indian Ocean island of Mauritius based on the recovery of Proterozoic zircons from basaltic beach sands. Here we document the first U-Pb zircon ages recovered directly from 5.7 Ma Mauritian trachytic rocks. We identified concordant Archaean xenocrystic zircons ranging in age between 2.5 and 3.0 Ga within a trachyte plug that crosscuts Older Series plume-related basalts of Mauritius. Our results demonstrate the existence of ancient continental crust beneath Mauritius; based on the entire spectrum of U-Pb ages for old Mauritian zircons, we demonstrate that this ancient crust is of central-east Madagascar affinity, which is presently located ∼700 km west of Mauritius. This makes possible a detailed reconstruction of Mauritius and other Mauritian continental fragments, which once formed part of the ancient nucleus of Madagascar and southern India.

  2. Gold deposits in the late Archaean Nzega-Igunga greenstone belt, central plateau of tanzania

    SciTech Connect

    Feiss, P.G.; Siyomana, S.

    1985-01-01

    2.2 m oz of gold have been produced, since 1935, from late Archaean (2480-2740 Ma) greenstone belts of the Central Plateau, Tanzania. North and east of Nzega (4/sup 0/12'S, 3/sup 0/11'E), 18% of the exposed basement, mainly Dodoman schists and granites, consists of metavolcanics and metasediments of the Nyanzian and Kavirondian Series. Four styles of mineralization are observed. 1. Stratabound quartz-gold veins with minor sulfides. Host rocks are quartz porphyry, banded iron formation (BIF), magnetite quartzite, and dense, cherty jasperite at the Sekenke and Canuck mines. The Canuck veins are on strike from BIF's in quartz-eye porphyry of the Igusule Hills. 2. Stratabound, disseminated gold in coarse-grained, crowded feldspar porphyry with lithic fragments and minor pyrite. At Bulangamilwa, the porphyry is conformable with Nyanzian-aged submarine (.) greenstone, volcanic sediment, felsic volcanics, and sericite phyllite. The deposits are on strike with BIF of the Wella Hills, which contains massive sulfide with up to 15% Pb+Zn. 3. Disseminated gold in quartz-albite metasomes in Nyanzian greenstones. At Kirondatal, alteration is associated with alaskites and feldspar porphyry dikes traceable several hundred meters into post-Dodoman diorite porphyry. Gold is with pyrite, arsenopyrite, pyrrhotite, minor chalcopyrite, and sphalerite as well as tourmalinite and silica-cemented breccias. 4. Basal Kavirondian placers in metaconglomerates containing cobbles and boulders of Dodoman and Nyanzian rocks several hundred meters up-section from the stratabound, disseminated mineralization at Bulangamilwa.

  3. Volcanic environments of ore formation in the late Archaean Abitibi greenstone belt of Canada

    SciTech Connect

    Ludden, J.N.

    1985-01-01

    The tectonic and petrological evolution of the late Archaean Abitibi greenstone belt indicate both emergent and submergent volcanism played a role in its metallogenesis. At approximately 2700 m.y. the southern volcanic zone (SVZ) of the Abitibi belt was dominated by a rift-related tectonic and volcanic evolution in a transcurrent (wrench) fault regime. The tholeiitic and komatiitic magmas and associated differentiated volcanic rocks had access to shallow crustal levels allowing the development of submarine hydrothermal systems and syngenetic Cu-Zn (Noranda type) massive sulfide ore bodies. These deposits formed along a 300 km. axis in submerging, fault bounded, basins. In contrast, the northern volcanic zone (the Chibougamau-Chapais area) formed at 2720 m.y and was characterized by emergent volcanoes emplaced on a continental crust and cored by coeval diorite-tonalite plutons. Mafic magma was inhibited from the crust by fractionated and contaminated magmas. This resulted in the emplacement of hydrous calc-alkaline magmas and associated porphyry-type epigenetic Cu(Au) massive sulfides. Au-lode deposits are predominantly located near major shear-zones in the SVZ. The are forming solutions were released as a result of burial due to wrench faulting. The dynamic regime of the rifted SVZ may have resulted in the syngenetic massive sulfides, the Au-lode deposits, metamorphism and sedimentation being synchronous on a regional scale, whilst on a local scale, Au-lodes superimpose and replace massive sulfides, iron formation and metamorphic isograds.

  4. Archaean and Palaeoproterozoic metamorphic events in the Orekhov-Pavlograd compressional zone, Ukrainian Shield

    NASA Astrophysics Data System (ADS)

    Yurchenko, A. V.

    2012-04-01

    The Orekhov-Pavlograd zone (OPZ) is located between the Mesoarchaean-Neoarchaean Middle Dnieper Province and the Mesoarchaean-Palaeoproterozoic Azov Province in the eastern Ukrainian Shield. The OPZ consists of Archaean and Palaeoproterozoic high-grade metamorphic rocks. According U-Pb isotope analyses Archaean methaigneous rocks have age of 3.5-3.3 Ga, and latest AR events dated form both individual grains and metamorphic rims in the tonalite and the granitic vein occurred at about 2.88 Ga ego. Paleoproterozoic zircons from a hornblende granulite have a concordia age of 2.08 Ga [1]. P-T conditions of the 3.5-3.3 Ga processes calculated from the Ti content in zircon are of 730-760°C. Metamorphic event dated as 2.88 Ga is more preserved and detected in some amphibolites after mafic dykes. According to different methods of hornblende-plagioclase geothermometry along with Al- and Ti-geobarometry of hornblende, the amphibolites have formed at temperature of 735-749 °C and pressure of 5.2 to 7.8 kbar. P-T conditions of Paleoproterozoic metamorphic processes have been calculated for a Paleoproterozoic high-Al paragneiss and mafic rocks. On the base of the computer software THERIAK-DOMINO [2], near-isothermal decompression from ca. 8.5 to 6.0 kbar at 650 °C and then to 5.8 kbar at 740 °C has been determined for small irregular garnet grains (grs 4-7% and XMg 0.36-0.37) associated with the same biotite and plagioclase. P-T conditions obtained by means of the P-T pseudosection calculation are identical within errors to those defined by the Grt + Bt + Pl + Ozt geothermometer by [3] and the geobarometer by [4], T = 675 °C and P = 5.6 kbar. Temperature and pressure calculated for assemblage Grt-Pl-Opx-Amph-Ilm-Ru (mafic rock) by using the TWEEQU method shows: 1) high values of pressure and temperature (ca. 7 kbar and 800 °C) are linked with the first metamorphic event with Opx-Cpx assemblage, 2) moderate values (ca. 5 kbar and ca. 600 °C) are referred to the second

  5. Archaean to Paleozoic mantle plumes in the N-E Baltic shield

    NASA Astrophysics Data System (ADS)

    Bayanova, T.

    2003-04-01

    In Archaean the largest alkaline province occurred in the Keivy terrane. U-Pb dated zircon from alkaline and nepheline syenite (Ponoy, Zapadnokeivsky, Belaya Tundra and Saharjok) gave the age of 2.75-2.61Ga. The alkaline granite of the terrane belongs to A-type granite and has high HFSE and low Y/Nb and Yb/Ta ratios typical of enriched mantle. Nepheline syenite of Saharjok massif corresponds to analogous of the OIB-magma. ɛNd(T) ranges from +0.6 to -9.0 and reflects high metamorphic alterations of the rocks. ɛSr(T) shows a large scatter from -10000 to +100 for alkaline granite and from +100 to +5000 for subalkaline rocks which is interpreted as long-term magmatic differentiation. On ɛSr-ɛNd diagram less-altered alkaline granosyenite and alkaline gabbro lie in EM2 field (Zozulya and Bayanova, 2002). He^3/He^4 ratio for ilmenite from Ponoy massif is 0.6x10-6 suggesting contribution of mantle helium (Vetrin et al., 2000). U-Pb ages for zircons from the alkaline massifs are quite similar to those of 2613±18 and 2611±10 Ma for baddeleyite and zircon from Siilinjarvi's carbonatite. Geochronological results for the Kola alkaline massifs of the Baltic Shield increase well-known world data (Blichert-Toft et al., 1996). Close U-Pb ages are yielded by zircons from anorthosite of Achinsky, Tsaga and Medvezhje-Schuchjeozersky terranes. Duration of magmatism and isotope signatures for the rocks and minerals from alkaline and anorthosite association reflect the Archaean plume existence. In Proterozoic there are distinguished two 350 km-long belts of the PGE-bearing intrusions: Mt. Generalskaya, Monchepluton, Pana massif and Imandra Lopolith - Northern belt and Finnish Russian Southern belt with Penikat, Koiliismaa, Kontilainen and Olanga-group intrusions and Burakovsky massif in Karelia. U-Pb precise zircon-baddeleyite ages for the different parts of the intrusions (gabbronorite, gabbropegmatite and anorthosite) show 100 m.y. (2.5-2.4 Ga) duration of the mantle plume. Rocks

  6. Anomalous sulphur isotopes in plume lavas reveal deep mantle storage of Archaean crust.

    PubMed

    Cabral, Rita A; Jackson, Matthew G; Rose-Koga, Estelle F; Koga, Kenneth T; Whitehouse, Martin J; Antonelli, Michael A; Farquhar, James; Day, James M D; Hauri, Erik H

    2013-04-25

    Basaltic lavas erupted at some oceanic intraplate hotspot volcanoes are thought to sample ancient subducted crustal materials. However, the residence time of these subducted materials in the mantle is uncertain and model-dependent, and compelling evidence for their return to the surface in regions of mantle upwelling beneath hotspots is lacking. Here we report anomalous sulphur isotope signatures indicating mass-independent fractionation (MIF) in olivine-hosted sulphides from 20-million-year-old ocean island basalts from Mangaia, Cook Islands (Polynesia), which have been suggested to sample recycled oceanic crust. Terrestrial MIF sulphur isotope signatures (in which the amount of fractionation does not scale in proportion with the difference in the masses of the isotopes) were generated exclusively through atmospheric photochemical reactions until about 2.45 billion years ago. Therefore, the discovery of MIF sulphur in these young plume lavas suggests that sulphur--probably derived from hydrothermally altered oceanic crust--was subducted into the mantle before 2.45 billion years ago and recycled into the mantle source of Mangaia lavas. These new data provide evidence for ancient materials, with negative Δ(33)S values, in the mantle source for Mangaia lavas. Our data also complement evidence for recycling of the sulphur content of ancient sedimentary materials to the subcontinental lithospheric mantle that has been identified in diamond-hosted sulphide inclusions. This Archaean age for recycled oceanic crust also provides key constraints on the length of time that subducted crustal material can survive in the mantle, and on the timescales of mantle convection from subduction to upwelling beneath hotspots.

  7. The Archaean-Paleoproterozoic transition: First results of detrital zircon U-Pb-geochronology and provenance from the FAR DEEP drill cores

    NASA Astrophysics Data System (ADS)

    Gärtner, C.; Bahlburg, H.; Melezhik, V. A.; Lepland, A.; Berndt, J.; Kooijman, E.; Far Deep Scientists, The

    2010-05-01

    The Archaean-Paleoproterozoic transition is marked by several events that were important for the evolution of the Earth system. We applied U-Pb-geochronology on detrital zircons by LA-ICP-MS to improve age constraints on the duration of three of these events: 1) the Huronian Glaciation, which is the first known worldwide glaciation, 2) the Lomagundi-Jatuli event, characterized by a large excursion of δ13C in carbonate sediments and 3) the Shunga event, the first deposition of very Corg-rich sediments, so-called 'shungites'. During the Fennoscandian Arctic Russia - Drilling Early Earth Project (FAR DEEP), which is part of the International Continental Scientific Drilling Program (ICDP), volcano-sedimentary successions of early Paleoproterozoic age were drilled in the Pechenga and Imandra-Varzuga Greenstone belts, as well as in the Onega basin in Russian Fennoscandia. The first results of detrital zircon dating provided an age range from 1.85 up to 3.5 Ga having one prominent age-group of 2.5-2.9 Ga for each sample. The youngest ages in individual samples vary due to their stratigraphic position. The youngest zircons from the Seidorechka Sedimentary Formation below Huronian glacial deposits in the Imandra-Varzuga Greenstone Belt yielded ages around 2.42 Ga, which are interpreted as the age close to the onset of the Huronian Glaciation. Zircon ages from the Polisarka Sedimentary Formation above Huronian diamictites in the Imandra-Varzuga Greenstone Belt indicate that the glaciation had ended at 2.22 Ga. The youngest zircon ages from the sequence containing isotopically heavy carbonates of the Kuetsjärvi Sedimentary Formation in the Pechenga Greenstone Belt suggest that the Lomagundi-Jatuli event started around 2.32 Ga and that its end is younger than 2.06 Ga. Age constraints of ca. 2.0-1.9 Ga for the beginning of the Shunga Event were obtained by dating zircons from the Kolasjoki Sedimentary Formation in the Pechenga Greenstone Belt. Considering the error, these

  8. Audio-magnetotelluric investigation of allochthonous iron formations in the Archaean Reguibat shield (Mauritania): structural and mining implications

    NASA Astrophysics Data System (ADS)

    Bronner, G.; Fourno, J. P.

    1992-11-01

    The M'Haoudat range, considered as an allochthonous unit amid the strongly metamorphosed Archaean basement (Tiris Group), belongs to the Lower Proterozoic Ijil Group, weakly metamorphosed, constituted mainly by iron quartzites including red jaspers and high grade iron ore. Audio-magnetotelluric (AMT) soundings (frequency range 1-7500 HZ) were performed together with the systematic survey of the range (SNIM mining company). The non-linear least squares method was used to perform a smoothness-constrained data model. The obvious AMT resistivity contrasts between the M'Haoudat Unit (150-3500 ohm. m) and the Archaean basement (20 000 ohm. m) allow to state precisely that the two thrust surfaces, on both sides of the range, join together at a depth which increases from North-West to South-East, as the ore bodies. Inside the steeply dipping M'Haoudat Unit, the main beds of iron quartzites (1500-3500 ohm. m), schists (1000-1500 ohm. m) and hematite ores (150-300 ohm. m) were distinguished when their thickness exceeded 30 to 50 m. The existence of an hydrostatic level (1-50 ohm. m) and the steeply dipping architecture, very likely responsible for the lack of resistivity contrast on the upper part of some profiles, complicate the interpretation at high frequencies the thin layers being poorly defined.

  9. Orogenic gold mineralisation hosted by Archaean basement rocks at Sortekap, Kangerlussuaq area, East Greenland

    NASA Astrophysics Data System (ADS)

    Holwell, D. A.; Jenkin, G. R. T.; Butterworth, K. G.; Abraham-James, T.; Boyce, A. J.

    2013-04-01

    A gold-bearing quartz vein system has been identified in Archaean basement rocks at Sortekap in the Kangerlussuaq region of east Greenland, 35 km north-northeast of the Skaergaard Intrusion. This constitutes the first recorded occurrence of Au mineralisation in the metamorphic basement rocks of east Greenland. The mineralisation can be classified as orogenic style, quartz vein-hosted Au mineralisation. Two vein types have been identified based on their alteration styles and the presence of Au mineralisation. Mineralised type 1 veins occur within sheared supracrustal units and are hosted by garnet-bearing amphibolites, with associated felsic and ultramafic intrusions. Gold is present as native Au and Au-rich electrum together with arsenopyrite and minor pyrite and chalcopyrite in thin alteration selvages in the immediate wall rocks. The alteration assemblage of actinolite-clinozoisite-muscovite-titanite-scheelite-arsenopyrite-pyrite is considered to be a greenschist facies assemblage. The timing of mineralisation is therefore interpreted as being later and separate event to the peak amphibolite facies metamorphism of the host rocks. Type 2 quartz veins are barren of mineralisation, lack significant alteration of the wall rocks and are considered to be later stage. Fluid inclusion microthermometry of the quartz reveals three separate fluids, including a high temperature ( T h = 300-350 °C), H2O-CO2-CH4 fluid present only in type 1 veins that in interpreted to be responsible for the main stage of Au deposition and sulphidic wall rock alteration. It is likely that the carbonic fluids were actually trapped at temperatures closer to 400 °C. Two other fluids were identified within both vein types, which comprise low temperature (100-200 °C) brines, with salinities of 13-25 wt% eq. NaCl and at least one generation of low salinity aqueous fluids. The sources and timings of the secondary fluids are currently equivocal but they may be related to the emplacement of

  10. Mineralogical and geochemical characteristics of the Archaean LCT pegmatite deposit Cattlin Creek, Ravensthorpe, Western Australia

    NASA Astrophysics Data System (ADS)

    Bauer, Matthias; Dittrich, Thomas; Seifert, Thomas; Schulz, Bernhard

    2014-05-01

    The LCT (lithium-cesium-tantalum) pegmatite Cattlin Creek is located about 550 km ESE of Perth, Western Australia. The complex-type, rare-element pegmatite is hosted in metamorphic rocks of the Archaean Ravensthorpe greenstone belt, which constitutes of the southern edge of the Southern Cross Terranes of the Yilgarn Craton. The deposit is currently mined for both lithium and tantalum by Galaxy Resources Limited since 2010. The pegmatitic melt intruded in a weak structural zone of crossing thrust faults and formed several pegmatite sills, of which the surface nearest mineralized pegmatite body is up to 21 m thick. The Cattlin Creek pegmatite is characterized by an extreme fractionation that resulted in the enrichment of rare elements like Li, Cs, Rb, Sn and Ta, as well as the formation of a vertical zonation expressed by distinct mineral assemblages. The border zone comprises a fine-grained mineral assemblage consisting of albite, quartz, muscovite that merges into a medium-grained wall zone and pegmatitic-textured intermediate zones. Those zones are manifested by the occurrence of megacrystic spodumene crystals with grain sizes ranging from a couple of centimeters up to several metres. The core zone represents the most fractionated part of the pegmatite and consists of lepidolite, cleavelandite, and quartz. It also exhibits the highest concentrations of Cs (0.5 wt.%), Li (0.4 wt.%), Rb (3 wt.%), Ta (0.3 wt.%) and F (4 wt.%). This zone was probably formed in the very last crystallization stage of the pegmatite and its minerals replaced earlier crystallized mineral assemblages. Moreover, the core zone hosts subordinate extremely Cs-enriched (up to 13 wt.% Cs2O) mineral species of beryl. The chemical composition of this beryl resamples that of the extreme rare beryl-variety pezzotaite. Other observed subordinate, minor and accessory minerals comprise tourmaline, garnet, cassiterite, apatite, (mangano-) columbite, tantalite, microlite (Bi-bearing), gahnite, fluorite

  11. Multifractal spatial organisation in hydrothermal gold systems of the Archaean Yilgarn craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Munro, Mark; Ord, Alison; Hobbs, Bruce

    2015-04-01

    A range of factors controls the location of hydrothermal alteration and gold mineralisation in the Earth's crust. These include the broad-scale lithospheric architecture, availability of fluid sources, fluid composition and pH, pressure-temperature conditions, microscopic to macroscopic structural development, the distribution of primary lithologies, and the extent of fluid-rock interactions. Consequently, the spatial distribution of alteration and mineralization in hydrothermal systems is complex and often considered highly irregular. However, despite this, do they organize themselves in a configuration that can be documented and quantified? Wavelets, mathematical functions representing wave-like oscillations, are commonly used in digital signals analysis. Wavelet-based multifractal analysis involves incrementally scanning a wavelet across the dataset multiple times (varying its scale) and recording its degree of fit to the signal at each interval. This approach (the wavelet transform modulus maxima method) highlights patterns of self-similarity present in the dataset and addresses the range of scales over which these patterns replicate themselves (expressed by their range in 'fractal dimension'). Focusing on seven gold ore bodies in the Archaean Yilgarn craton of Western Australia, this study investigates whether different aspects of hydrothermal gold systems evolve to organize themselves spatially as multifractals. Four ore bodies were selected from the Sunrise Dam deposit (situated in the Laverton tectonic zone of the Kurnalpi terrane) in addition to the Imperial, Majestic and Salt Creek gold prospects, situated in the Yindarlgooda dome of the Mount Monger goldfield (approximately 40km due east of Kalgoorlie). The Vogue, GQ, Cosmo East and Astro ore bodies at Sunrise Dam were chosen because they exhibit different structural geometries and relationships between gold and associated host-rock alteration styles. Wavelet-based analysis was conducted on 0.5m and 1m

  12. Paleoproterozoic rejuvenation and replacement of Archaean lithosphere: Evidence from zircon U-Pb dating and Hf isotopes in crustal xenoliths at Udachnaya, Siberian craton

    NASA Astrophysics Data System (ADS)

    Moyen, J.-F.; Paquette, J.-L.; Ionov, D. A.; Gannoun, A.; Korsakov, A. V.; Golovin, A. V.; Moine, B. N.

    2017-01-01

    Cratons represent the oldest preserved lithospheric domains. Their lithosphere (lithospheric mantle welded to overlying Precambrian crystalline basement) is considered to be particularly robust and long-lived due to the protecting presence of buoyant and rigid "keels" made up of residual harzburgites. Although the cratons are mostly assumed to form in the Archaean, the timing of their formation remains poorly constrained. In particular, there are very few datasets describing concurrently the age of both the crustal and mantle portions of the lithosphere. In this study, we report new U-Pb ages and Hf isotope compositions for zircons in crustal xenoliths from the Udachnaya kimberlite in the central Siberian craton; this dataset includes samples from both the upper and lower portions of the crust. The zircon ages agree well with model melt-extraction Re-Os ages on refractory peridotite xenoliths from the same pipe; taken together they allow an integrated view of lithosphere formation. Our data reveal that the present day upper crust is Archaean, whereas both the lower crust and the lithospheric mantle yield Paleoproterozoic ages. We infer that the deep lithosphere beneath the Siberian craton was not formed in a single Archaean event, but grew in at least two distinct events, one in the late Archaean and the other in the Paleoproterozoic. Importantly, a complete or large-scale delamination and rejuvenation of the Archaean lower lithosphere (lower crust and lithospheric mantle) took place in the Paleoproterozoic. This further demonstrates that craton formation can be a protracted, multi-stage process, and that the present day crust and mantle may not represent complementary reservoirs formed through the same tectono-magmatic event. Further, deep cratonic lithosphere may be less robust and long living than often assumed, with rejuvenation and replacement events throughout its history.

  13. Archaean microbial consortia of the 2.7-2.6 Ga Ngesi Gp. (Belingwe) sediments, Zimbabwe

    NASA Astrophysics Data System (ADS)

    Grassineau, N. V.; Nisbet, E. G.; Thomazo, C.

    2011-12-01

    microbial ecology can be deduced. S isotopes imply the presence of sulphate reducers, and most probably sulphide oxidisers in sulphureta. C isotopes in stromatolites imply the presence of cyanobacteria carrying out oxygenic photosynthesis. C isotopes also record more extreme fractionation involving methanogenesis. The presence of methanotrophs to reconvert the methane to carbon dioxide and organic matter is also a likely inference, supported by the 'light' carbonate in the Cheshire shales. Both the Archaean carbonate reefs and the muddy bottoms probably hosted patchworks of microbial consortia, dependent on small-scale physical (and chemical) variation in the sediment reflecting local depositional facies and diagenetic processes, as well as external factors such as tides, currents and seasonality.

  14. Large Transition-Metal Isotope Fractionations Associated with Archaean Microbial Communities

    NASA Astrophysics Data System (ADS)

    Archer, C.; Vance, D.

    2001-12-01

    Transition metal stable isotopes potentially have many useful geochemical and biogeochemical applications. Because of the relatively small differences in mass between isotopes it is thought that these elements are not substantially fractionated by high temperature terrestrial processes. However low temperature, and in particular, biological processes may produce significant fractionations. Recent advances in multicollector ICP technology have overcome previous analytical difficulties and made the necessary high precision isotopic measurements possible. Here we present data that illustrate some technical aspects of transition metal isotope geochemistry by multi-collector ICP-MS. In addition, we report data for Fe and preliminary data for Zn isotopes in Archaean sulphide samples associated with sulphate-reducing bacteria in microbial communities from the 2.7 Ga Belingwe belt, Zimbabwe. We have employed the same chemical separation procedures reported previously1. However, we have observed fractionation artefacts associated with matrix elements (mainly Ti and Fe) in the Zn fraction which we have eradicated by the addition of a small column to further purify the separated Zn. Instrument mass bias has been corrected for Fe using standard bracketing and for Zn using Cu-doping. We have also found that careful matching of Cu/Zn ratios in standards and samples is necessary in order to avoid very systematic mass-bias artefacts associated with the instrument. For example, the 66Zn/64Zn ratio for standards and samples, mass-bias corrected using 65Cu/63Cu, changes by 1.1 per mil as the Cu/Zn ratio changes from 1 to 0.1. The change is only 0.3 per mil, however, as the Cu/Zn ratio changes from 1 to 10. These changes are associated with non-linear variations in the Cu signal and are tentatively attributed to space-charge effects in the ICP source/expansion area. Multiple analyses (n=12, processed separately through the chemistry) of USGS standard basalt BCR-1, during two different

  15. Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth.

    PubMed

    Nutman, A P; Mojzsis, S J; Friend, C R

    1997-01-01

    A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages of 3865 +/- 11 Ma and 3840 +/- 8 Ma (2 sigma) can be calculated by different approaches. Three other methods of assessing the zircon data yield ages of >3830 Ma. The BIFs are interpreted as water-lain sediments, which with a minimum age of approximately 3850 Ma, are the oldest sediments yet documented. These rocks provide proof that by approximately 3850 Ma (1) there was a hydrosphere, supporting the chemical sedimentation of BIF, and that not all water was stored in hydrous minerals, and (2) that conditions satisfying the stability of liquid water imply surface temperatures were similar to present. Carbon isotope data of graphitic microdomains in apatite from the Akilia island BIF are consistent with a bio-organic origin (Mojzsis et al. 1996), extending the record of life on Earth to >3850 Ma. Life and surface water by approximately 3850 Ma provide constraints on either the energetics or termination of the late meteoritic bombardment event (suggested from the lunar cratering record) on Earth.

  16. Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth

    NASA Technical Reports Server (NTRS)

    Nutman, A. P.; Mojzsis, S. J.; Friend, C. R.; Bada, J. L. (Principal Investigator)

    1997-01-01

    A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages of 3865 +/- 11 Ma and 3840 +/- 8 Ma (2 sigma) can be calculated by different approaches. Three other methods of assessing the zircon data yield ages of >3830 Ma. The BIFs are interpreted as water-lain sediments, which with a minimum age of approximately 3850 Ma, are the oldest sediments yet documented. These rocks provide proof that by approximately 3850 Ma (1) there was a hydrosphere, supporting the chemical sedimentation of BIF, and that not all water was stored in hydrous minerals, and (2) that conditions satisfying the stability of liquid water imply surface temperatures were similar to present. Carbon isotope data of graphitic microdomains in apatite from the Akilia island BIF are consistent with a bio-organic origin (Mojzsis et al. 1996), extending the record of life on Earth to >3850 Ma. Life and surface water by approximately 3850 Ma provide constraints on either the energetics or termination of the late meteoritic bombardment event (suggested from the lunar cratering record) on Earth.

  17. No climate paradox under the faint early Sun.

    PubMed

    Rosing, Minik T; Bird, Dennis K; Sleep, Norman H; Bjerrum, Christian J

    2010-04-01

    Environmental niches in which life first emerged and later evolved on the Earth have undergone dramatic changes in response to evolving tectonic/geochemical cycles and to biologic interventions, as well as increases in the Sun's luminosity of about 25 to 30 per cent over the Earth's history. It has been inferred that the greenhouse effect of atmospheric CO(2) and/or CH(4) compensated for the lower solar luminosity and dictated an Archaean climate in which liquid water was stable in the hydrosphere. Here we demonstrate, however, that the mineralogy of Archaean sediments, particularly the ubiquitous presence of mixed-valence Fe(II-III) oxides (magnetite) in banded iron formations is inconsistent with such high concentrations of greenhouse gases and the metabolic constraints of extant methanogens. Prompted by this, and the absence of geologic evidence for very high greenhouse-gas concentrations, we hypothesize that a lower albedo on the Earth, owing to considerably less continental area and to the lack of biologically induced cloud condensation nuclei, made an important contribution to moderating surface temperature in the Archaean eon. Our model calculations suggest that the lower albedo of the early Earth provided environmental conditions above the freezing point of water, thus alleviating the need for extreme greenhouse-gas concentrations to satisfy the faint early Sun paradox.

  18. Late-Archaean crustal growth in the Lewisian Complex of Northwest Scotland: Diachroneity in magmatic accretion and implications for models of crustal growth

    NASA Technical Reports Server (NTRS)

    Whitehouse, M. J.

    1988-01-01

    The Lewisian Complex of northwestern Scotland is an Archaean basement terrain that was reworked during the Proterozoic. Previous geochronological studies have established that the complex represents an entirely new crustal addition during late-Archaean times, and the difference between a Sm-Nd accretion date of 2920 + or - 50 Ma and a Pb/Pb metamorphic date of 2680 + or - 70 Ma was interpreted as indicating a crustal accretion-differentiation superevent (CADS) lasting 240 + or - 110 Ma. A combined Rb-Sr, Pb/Pb, and Sm-Nd isotopic study reported was applied to the Lewisian CADS to attempt to address the problem of whether this comprised a short regional scale magmatic accretion event followed approximately 200 Ma later by regional high-grade metamorphism, or a long period of episodic or semi-continuous magmatic accretion prior to high-grade metamorphism.

  19. Stable isotope study of the Archaean rocks of the Vredefort impact structure, central Kaapvaal Craton, South Africa

    NASA Astrophysics Data System (ADS)

    Fagereng, Åke; Harris, Chris; La Grange, Mandy; Stevens, Gary

    2008-01-01

    The Vredefort dome in the Kaapvaal Craton was formed as a result of the impact of a large meteorite at 2.02 Ga. The central core of Archaean granitic basement rocks is surrounded by a collar of uplifted and overturned strata of the Witwatersrand Supergroup, exposing a substantial depth section of the Archaean crust. Orthogneisses of the core show little variation in whole-rock δ 18O value, with the majority being between 8 and 10‰, with a mean of 9.2‰ ( n = 35). Quartz and feldspar have per mil differences that are consistent with O-isotope equilibrium at high temperatures, suggesting minimal interaction with fluids during subsequent cooling. These data refute previous suggestions that the Outer Granite Gneiss (OGG) and Inlandsee Leucogranofels (ILG) of the core represent middle and lower crust, respectively. Granulite-facies greenstone remnants from the ILG have δ 18O values that are on average 1.5‰ higher than the ILG host rocks and are unlikely, therefore, to represent the residuum from the partial melting event that formed the host rock. Witwatersrand Supergroup sedimentary rocks of the collar, which were metamorphosed at greenschist-to amphibolite-facies conditions, generally have lower δ 18O values than the core rocks with a mean value for metapelites of 7.7‰ ( n = 45). Overall, through an ˜20 km thick section of crust, there is a general increase in whole-rock δ 18O value with increasing depth. This is the reverse of what is normal in the crust, largely because the collar rocks have δ 18O values that are unusually low in comparison with metamorphosed sedimentary rocks worldwide. The collar rocks have δD values ranging from -35 to -115‰ (average -62‰, n = 29), which are consistent with interaction with water of meteoric origin, having a δD of about -25 to -45‰. We suggest that fluid movement through the collar rocks was enhanced by impact-induced secondary permeability in the dome structure.

  20. Selection for Protein Kinetic Stability Connects Denaturation Temperatures to Organismal Temperatures and Provides Clues to Archaean Life

    PubMed Central

    Romero-Romero, M. Luisa; Risso, Valeria A.; Martinez-Rodriguez, Sergio; Gaucher, Eric A.; Ibarra-Molero, Beatriz; Sanchez-Ruiz, Jose M.

    2016-01-01

    The relationship between the denaturation temperatures of proteins (Tm values) and the living temperatures of their host organisms (environmental temperatures: TENV values) is poorly understood. Since different proteins in the same organism may show widely different Tm’s, no simple universal relationship between Tm and TENV should hold, other than Tm≥TENV. Yet, when analyzing a set of homologous proteins from different hosts, Tm’s are oftentimes found to correlate with TENV’s but this correlation is shifted upward on the Tm axis. Supporting this trend, we recently reported Tm’s for resurrected Precambrian thioredoxins that mirror a proposed environmental cooling over long geological time, while remaining a shocking ~50°C above the proposed ancestral ocean temperatures. Here, we show that natural selection for protein kinetic stability (denaturation rate) can produce a Tm↔TENV correlation with a large upward shift in Tm. A model for protein stability evolution suggests a link between the Tm shift and the in vivo lifetime of a protein and, more specifically, allows us to estimate ancestral environmental temperatures from experimental denaturation rates for resurrected Precambrian thioredoxins. The TENV values thus obtained match the proposed ancestral ocean cooling, support comparatively high Archaean temperatures, and are consistent with a recent proposal for the environmental temperature (above 75°C) that hosted the last universal common ancestor. More generally, this work provides a framework for understanding how features of protein stability reflect the environmental temperatures of the host organisms. PMID:27253436

  1. Selection for Protein Kinetic Stability Connects Denaturation Temperatures to Organismal Temperatures and Provides Clues to Archaean Life.

    PubMed

    Romero-Romero, M Luisa; Risso, Valeria A; Martinez-Rodriguez, Sergio; Gaucher, Eric A; Ibarra-Molero, Beatriz; Sanchez-Ruiz, Jose M

    2016-01-01

    The relationship between the denaturation temperatures of proteins (Tm values) and the living temperatures of their host organisms (environmental temperatures: TENV values) is poorly understood. Since different proteins in the same organism may show widely different Tm's, no simple universal relationship between Tm and TENV should hold, other than Tm≥TENV. Yet, when analyzing a set of homologous proteins from different hosts, Tm's are oftentimes found to correlate with TENV's but this correlation is shifted upward on the Tm axis. Supporting this trend, we recently reported Tm's for resurrected Precambrian thioredoxins that mirror a proposed environmental cooling over long geological time, while remaining a shocking ~50°C above the proposed ancestral ocean temperatures. Here, we show that natural selection for protein kinetic stability (denaturation rate) can produce a Tm↔TENV correlation with a large upward shift in Tm. A model for protein stability evolution suggests a link between the Tm shift and the in vivo lifetime of a protein and, more specifically, allows us to estimate ancestral environmental temperatures from experimental denaturation rates for resurrected Precambrian thioredoxins. The TENV values thus obtained match the proposed ancestral ocean cooling, support comparatively high Archaean temperatures, and are consistent with a recent proposal for the environmental temperature (above 75°C) that hosted the last universal common ancestor. More generally, this work provides a framework for understanding how features of protein stability reflect the environmental temperatures of the host organisms.

  2. Shear wave velocity structure of the lower crust in southern Africa: Evidence for compositional heterogeneity within Archaean and Proterozoic terrains

    NASA Astrophysics Data System (ADS)

    Kgaswane, Eldridge M.; Nyblade, Andrew A.; Juliã, Jordi; Dirks, Paul H. G. M.; Durrheim, Raymond J.; Pasyanos, Michael E.

    2009-12-01

    The nature of the lower crust across the southern African shield has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations located in Botswana, South Africa and Zimbabwe. For large parts of both Archaean and Proterozoic terrains, the velocity models obtained from the inversions show shear wave velocities ≥4.0 km/s below ˜20-30 km depth, indicating a predominantly mafic lower crust. However, for much of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain in South Africa, as well as for the western part of the Tokwe terrain in Zimbabwe, shear wave velocities of ≤3.9 km/s are found below ˜20-30 km depth, indicating an intermediate-to-felsic lower crust. The areas of intermediate-to-felsic lower crust in South Africa coincide with regions where Ventersdorp rocks have been preserved, suggesting that the more evolved composition of the lower crust may have resulted from crustal reworking and extension during the Ventersdorp tectonomagmatic event at c. 2.7 Ga.

  3. A Sm-Nd and Pb isotope study of Archaean greenstone belts in the southern Kaapvaal Craton, South Africa

    NASA Technical Reports Server (NTRS)

    Wilson, A. H.; Carlson, R. W.

    1989-01-01

    An Sm-Nd and Pb study on a wide variety of lithologies in Archaean greenstone belt fragments in the southern Kaapvaal Craton reveals a complex petrogenetic history. The fragments are important because they represent a 350 km transect through the craton south of Barberton to its southern margin. The Commondale greenstone belt yields a precise Sm-Nd age of 3334 + or - 18 Ma on an exceptionally well preserved peridotite suite of komatiitic affinity. The wide range of Sm/Nd from 0.6 to 1.0 is attributed to the unusual occurrence of orthopyroxene in the spinifex-bearing rocks. A considerably younger age of about 3.2 Ga is suggested for the Nondweni greenstone belt close to the southern margin of the craton on the basis of separate Sm-Nd isochrons on individual lithologies ranging from komatiite, through komatiitic basalt and basalt to felsic volcanic rocks. On the basis of the present study the greenstone belts appear to have been emplaced at progressively younger ages toward the southern margin of the craton.

  4. New insights into typical Archaean structures in greenstone terranes of western Ontario

    NASA Technical Reports Server (NTRS)

    Schwerdtner, W. M.

    1986-01-01

    Ongoing detailed field work in selected granitoid complexes of the western Wabigoon and Wawa Subprovinces, southern Canadian Shield, has led to several new conclusions: (1) Prominent gneiss domes are composed of prestrained tonalite-granodiorite and represent dense hoods of magmatic granitoid diapirs; (2) the deformation history of the prestrained gneiss remains to be unraveled; (3) the gneiss lacked a thick cover of mafic metavolcanics or other dense rocks at the time of magmatic diaprisim; (4) the synclinoral structure of large greenstone belts is older than the late gneiss domes and may have been initiated by volcano-tectonic processes; (5) small greenstone masses within the gneiss are complexly deformed, together with the gneiss; and, (6) no compelling evidence has been found of ductile early thrusting in the gneiss terranes. Zones of greenstone enclaves occur in hornblende-rich contaminated tonalite and are apt to be deformed magmatic septa. Elsewhere, the tonalite gneiss is biotite-rich and hornblende-poor. These conclusions rest on several new pieces of structural evidence; (1) oval plutons of syenite-diorite have magmatic strain fabrics and sharp contacts that are parallel to an axial-plane foliation in the surrounding refolded gneiss; (2) gneiss domes are lithologically composite and contain large sheath-like structures which are deformed early plutons, distorted earlier gneiss domes, or early ductile nappes produced by folding of planar plutonic septa, and (3) the predomal attitudes of gneissosity varied from point to point.

  5. Shear Wave Velocity Structure of Southern African Crust: Evidence for Compositional Heterogeneity within Archaean and Proterozoic Terrains

    SciTech Connect

    Kgaswane, E M; Nyblade, A A; Julia, J; Dirks, P H H M; Durrheim, R J; Pasyanos, M E

    2008-11-11

    Crustal structure in southern Africa has been investigated by jointly inverting receiver functions and Rayleigh wave group velocities for 89 broadband seismic stations spanning much of the Precambrian shield of southern Africa. 1-D shear wave velocity profiles obtained from the inversion yield Moho depths that are similar to those reported in previous studies and show considerable variability in the shear wave velocity structure of the lower part of the crust between some terrains. For many of the Archaean and Proterozoic terrains in the shield, S velocities reach 4.0 km/s or higher over a substantial part of the lower crust. However, for most of the Kimberley terrain and adjacent parts of the Kheis Province and Witwatersrand terrain, as well as for the western part of the Tokwe terrain, mean shear wave velocities of {le} 3.9 km/s characterize the lower part of the crust along with slightly ({approx}5 km) thinner crust. These findings indicate that the lower crust across much of the shield has a predominantly mafic composition, except for the southwest portion of the Kaapvaal Craton and western portion of the Zimbabwe Craton, where the lower crust is intermediate-to-felsic in composition. The parts of the Kaapvaal Craton underlain by intermediate-to-felsic lower crust coincide with regions where Ventersdorp rocks have been preserved, and thus we suggest that the intermediate-to-felsic composition of the lower crust and the shallower Moho may have resulted from crustal melting during the Ventersdorp tectonomagmatic event at c. 2.7 Ga and concomitant crustal thinning caused by rifting.

  6. Constraints on ocean carbonate chemistry and pCO2 in the Archaean and Palaeoproterozoic

    NASA Astrophysics Data System (ADS)

    Blättler, C. L.; Kump, L. R.; Fischer, W. W.; Paris, G.; Kasbohm, J. J.; Higgins, J. A.

    2017-01-01

    One of the great problems in the history of Earth’s climate is how to reconcile evidence for liquid water and habitable climates on early Earth with the Faint Young Sun predicted from stellar evolution models. Possible solutions include a wide range of atmospheric and oceanic chemistries, with large uncertainties in boundary conditions for the evolution and diversification of life and the role of the global carbon cycle in maintaining habitable climates. Increased atmospheric CO2 is a common component of many solutions, but its connection to the carbon chemistry of the ocean remains unknown. Here we present calcium isotope data spanning the period from 2.7 to 1.9 billion years ago from evaporitic sedimentary carbonates that can test this relationship. These data, from the Tumbiana Formation, the Campbellrand Platform and the Pethei Group, exhibit limited variability. Such limited variability occurs in marine environments with a high ratio of calcium to carbonate alkalinity. We are therefore able to rule out soda ocean conditions during this period of Earth history. We further interpret this and existing data to provide empirical constraints for carbonate chemistry of the ancient oceans and for the role of CO2 in compensating for the Faint Young Sun.

  7. A basin on an unstable ground: Correlation of the Middle Archaean Moodies Basin, Barberton Greenstone Belt, South Africa

    NASA Astrophysics Data System (ADS)

    Ohnemueller, Frank; Heubeck, Christoph; Kirstein, Jens; Gamper, Antonia

    2010-05-01

    time and immediately predates the initiation of basin shortening. Basin compartmentalization was likely due to the movement along a group of major faults (Sheba, Haki, Barbrook, Saddleback Faults) between the present Saddleback and Eureka Synclines, creating at least two subbasins in late Moodies time. Even though sediment provenance thus became localized, intensive Archaean weathering likely contributed to generate petrographically similar quartz-rich sandstones in fault-bounded minibasins. The late-Moodies minibasins may have become connected occasionally, allowing concurrent deposition of thin BIFs. A similar phase of movement along the major transcurrent Inyoka Fault may be responsible for the distinct petrographic character of Moodies sandstones south of that fault.

  8. Mechanisms for strain localization within Archaean craton: A structural study from the Bundelkhand Tectonic Zone, north-central India

    NASA Astrophysics Data System (ADS)

    Sarkar, Saheli; Patole, Vishal; Saha, Lopamudra; Pati, Jayanta Kumar; Nasipuri, Pritam

    2015-04-01

    The transformation of palaeo-continents involve breakup, dispersal and reassembly of cratonic blocks by collisional suturing that develop a network of orogenic (mobile) belts around the periphery of the stable cratons. The nature of deformation in the orogenic belt depends on the complex interaction of fracturing, plastic deformation and diffusive mass transfer. Additionally, the degree and amount of melting during regional deformation is critical as the presence of melt facilitates the rate of diffusive mass transfer and weakens the rock by reducing the effective viscosity of the deformed zone. The nature of strain localization and formation of ductile shear zones surrounding the cratonic blocks have been correlated with Proterozoic-Palaeozoic supercontinent assembly (Columbia, Rodinia and Gondwana reconstruction). Although, a pre-Columbia supercontinent termed as Kenorland has been postulated, there is no evidence that supports the notion due to lack of the presence of shear zones within the Archaean cratonic blocks. In this contribution, we present the detailed structural analysis of ductile shear zones within the Bundelkhand craton. The ductlile shear zone is termed as Bundelkhand Tectonic Zone (BTZ) that extends east-west for nearly 300 km throughout the craton with a width of two-three kilometer . In the north-central India, the Bundelkhand craton is exposed over an area of 26,000 sq. The craton is bounded by Central Indian Tectonic zone in the south, the Great Boundary fault in the west and by the rocks of Lesser Himalaya in the north. A series of tonalite-trondjhemite-granodiorite gneiss are the oldest rocks of the Bundelkhand craton that also contains a succession of metamorphosed supracrustal rocks comprising of banded iron formation, quartzite, calc-silicate and ultramafic rocks. K-feldspar bearing granites intrude the tonalite-trondjhemite-granodiorite and the supracrustal rocks during the time span of 2.1 to 2.5 Ga. The TTGs near Babina, in central

  9. Archaean associations of volcanics, granulites and eclogites of the Belomorian province, Fennoscandian Shield and its geodynamic interpretation

    NASA Astrophysics Data System (ADS)

    Slabunov, Alexander

    2013-04-01

    An assembly of igneous (TTG-granitoids and S-type leucogranites and calc-alkaline-, tholeiite-, kometiite-, boninite- and adakite-series metavolcanics) and metamorphic (eclogite-, moderate-pressure (MP) granulite- and MP amphibolite-facies rocks) complexes, strikingly complete for Archaean structures, is preserved in the Belomorian province of the Fennoscandian Shield. At least four Meso-Neoarchaean different-aged (2.88-2.82; 2.81-2.78; ca. 2.75 and 2.735-2.72 Ga) calc-alkaline and adakitic subduction-type volcanics were identified as part of greenstone belts in the Belomorian province (Slabunov, 2008). 2.88-2.82 and ca. 2.78 Ga fore-arc type graywacke units were identified in this province too (Bibikova et al., 2001; Mil'kevich et al., 2007). Ca.2.7 Ga volcanics were generated in extension structures which arose upon the collapse of an orogen. The occurrence of basalt-komatiite complexes, formed in most greenstone belts in oceanic plateau settings under the influence of mantle plumes, shows the abundance of these rocks in subducting oceanic slabs. Multiple (2.82-2.79; 2.78-2.76; 2.73-2.72; 2.69-2.64 Ga) granulite-facies moderate-pressure metamorphic events were identified in the Belomorian province (Volodichev, 1990; Slabunov et al., 2006). The earliest (2.82-2.79 Ga) event is presumably associated with accretionary processes upon the formation of an old continental crust block. Two other events (2.78-2.76; 2.73-2.72 Ga) are understood as metamorphic processes in suprasubduction setting. Late locally active metamorphism is attributed to the emplacement of mafic intrusions upon orogen collapse. Three groups of crustal eclogites with different age were identified in the Belomorian province: Mesoarchaean (2.88-2.86 and 2.82-2.80 Ga) eclogites formed from MORB and oceanic plateau type basalts and oceanic high-Mg rocks (Mints et al., 2011; Shchipansky at al., 2012); Neoarchaean (2.72 Ga) eclogites formed from MORB and oceanic plateau type basalts. The formation of

  10. U-Pb geochronology on detrital zircons from FAR-DEEP cores, Fennoscandian Shield - age constraints for events of the Archaean-Palaeoproterozoic transition and provenance

    NASA Astrophysics Data System (ADS)

    Gaertner, C.; Martin, A.; Bahlburg, H.; Lepland, A.; Melezhik, V.; Prave, A. R.; Condon, D. J.; Berndt, J.; Kooijman, E.; Far-Deep Scientists

    2010-12-01

    The Archaean-Palaeoproterozoic transition is marked by several environmental events that were important for the evolution of the Earth system and occurred coeval with plate tectonic reorganisations including the break-up of the supercontinent Kenorland. We applied U-Pb-geochronology on detrital zircons by LA-ICP-MS and ID-TIMS to improve age constraints of these events, recorded in the 2.5-2.0 Ga rock successions of the Fennoscandian Shield and including the Huronian glaciation and the Lomagundi-Jatuli positive excursion of δ13C in sedimentary carbonates. The detrital zircons provided ages ranging from 3.5 to 1.9 Ga with dominant age populations in the range of 2.9-2.5 Ga for most samples. Youngest zircon ages from the Seidorechka Sedimentary and Polisarka formations in the Imandra-Varzuga Greenstone Belt and the Neverskrukk Formation in the Pechenga Greenstone Belt constrain, for the first time, the deposition of glacial diamictites on the Fennoscandian Shield to between 2.43 and 2.2 Ga. Similar ages have been reported for glacial deposits in Canada and South Africa, consistent with a global glaciation at that time. The youngest detrital zircon ages derived from the Kuetsjärvi Sedimentary Fm, containing isotopically heavy carbonates, and from the overlying Kolasjoki Sedimentary Fm in the Pechenga Greenstone Belt indicate that deposition of carbonates corresponding to the Lomagundi-Jatuli δ13C excursion took place between 2.3 Ga and 2.06 Ga, in agreement with previous ages from these formations. Detrital zircon populations of c. 2.06 Ga and c. 1.92 Ga characterise the lower and upper parts of the Kolasjoki Sedimentary Fm, respectively. These units are separated by an unconformity of unknown duration, but the age distributions may indicate a significant hiatus because these are considerably younger than the 2.0-1.97 Ga ages reported from the overlying Pilgujärvi Sedimentary and Volcanic fms. Alternatively, the younger cluster of ages may record deformation

  11. 146Sm-142Nd evidence from Isua metamorphosed sediments for early differentiation of the Earth's mantle.

    PubMed

    Caro, Guillaume; Bourdon, Bernard; Birck, Jean-Louis; Moorbath, Stephen

    2003-05-22

    Application of the 147Sm-143Nd chronometer (half-life of 106 Gyr) suggests that large-scale differentiation of the Earth's mantle may have occurred during the first few hundred million years of its history. However, the signature of mantle depletion found in early Archaean rocks is often obscured by uncertainties resulting from open-system behaviour of the rocks during later high-grade metamorphic events. Hence, although strong hints exist regarding the presence of differentiated silicate reservoirs before 4.0 Gyr ago, both the nature and age of early mantle differentiation processes remain largely speculative. Here we apply short-lived 146Sm-142Nd chronometry (half-life of 103 Myr) to early Archaean rocks using ultraprecise measurement of Nd isotope ratios. The analysed samples are well-preserved metamorphosed sedimentary rocks from the 3.7-3.8-Gyr Isua greenstone belt of West Greenland. Our coupled isotopic calculations, combined with an initial epsilon 143Nd value from ref. 6, constrain the mean age of mantle differentiation to 4,460 +/- 115 Myr. This early Sm/Nd fractionation probably reflects differentiation of the Earth's mantle during the final stage of terrestrial accretion.

  12. Isotope composition and volume of Earth's early oceans.

    PubMed

    Pope, Emily C; Bird, Dennis K; Rosing, Minik T

    2012-03-20

    Oxygen and hydrogen isotope compositions of Earth's seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen's was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 ± 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth's oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH(4) and CO(2) concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth.

  13. Isotope composition and volume of Earth’s early oceans

    PubMed Central

    Pope, Emily C.; Bird, Dennis K.; Rosing, Minik T.

    2012-01-01

    Oxygen and hydrogen isotope compositions of Earth’s seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen’s was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 ± 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth’s oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH4 and CO2 concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth. PMID:22392985

  14. Ca isotope fingerprints of early crust-mantle evolution

    NASA Astrophysics Data System (ADS)

    Kreissig, K.; Elliott, T.

    2005-01-01

    The utility of 40Ca/ 44Ca as a tracer of pre-existing crustal contributions in early Archaean cratons has been explored to identify traces of Hadean crust and to assess the style of continental growth. The relatively short half-life of 40K (˜1.3 Gy) means that its decay to 40Ca occurs dominantly during early Earth History. If Archaean crust had a significant component derived from a more ancient protolith, as anticipated by "steady state" crustal evolution models, this should be clearly reflected in radiogenic 40Ca/ 44Ca ratios (or positive initial ɛ Ca) in different Archaean cratons. A high precision thermal ionisation technique has been used to analyse the 40Ca/ 44Ca ratios of plagioclase separates and associated whole rocks in ˜3.6 Ga (early Archaean) samples from Zimbabwe and West Greenland. Three out of four tonalite, trondhjemite, granodiorite (TTG) suite samples from Zimbabwe display initial 40Ca/ 44Ca ratios indistinguishable from our measured modern MORB value (i.e., ɛ Ca(3.6) ˜ 0). Greenland samples, however, are very diverse ranging from ɛ Ca(3.7) = 0.1 in mafic pillow lavas and felsic sheets from the Isua supracrustal belt, up to very radiogenic signatures (ɛ Ca(3.7) = 2.9) in both mafic rocks of the Akilia association and felsic TTG from the coastal Amîtsoq gneisses. At face value, these results imply the Zimbabwe crust is juvenile whereas most Greenland samples include an earlier crustal component. Yet the west Greenland craton, as with many Archaean localities, has experienced a complex geological history and the interpretation of age-corrected initial isotope values requires great care. Both felsic and mafic samples from Greenland display ɛ Ca(3.7) so radiogenic that they are not readily explained by crustal growth scenarios. The presence of such radiogenic 40Ca/ 44Ca found in low K/Ca plagioclases requires Ca isotope exchange between plagioclase and whole rock during later metamorphic event(s). In addition the unexpectedly radiogenic Ca

  15. Zircon from Mesoproterozoic sediments sheds light on the subduction-collision history at the eastern active continental margin of the Archaean Kalahari-Grunehogna Craton

    NASA Astrophysics Data System (ADS)

    Marschall, H.; Hawkesworth, C. J.; Leat, P. T.; Dhuime, B.; Storey, C.

    2013-12-01

    The Grunehogna Craton (East Antarctica) was a part of the Archean Kalahari Craton of southern Africa prior to Gondwana breakup. Granite from the basement of the craton has been dated by U-Pb zircon dating to 3,067 Ma with inherited grains showing ages of up to 3,433 Ma [1]. At the eastern margin of the craton, the Ahlmannryggen nunataks comprise an ~2000 m thick pile of clastic and volcanic sediments of the Ritscherflya Supergroup. These were sourced from eroding a proximal active continental arc as demonstrated through the age distribution and internal zoning of detrital zircon [2]. Detrital zircon grains from the Ritscherflya Supergroup show an age distribution with a dominant age peak at ~1,130 Ma, i.e., close to the sedimentation age. Older age peaks include those at 1370 Ma, 1725 Ma, 1880 Ma, 2050 Ma, and 2700 Ma. Palaeo- and Mesoarchaean zircon grains (2800-3445 Ma) were also discovered, corresponding to the age of the Kalahari-Grunehogna Craton basement. Most significantly we found a number of inherited Archaean cores in ~1130 Ma zircons. They demonstrate that the volcanic arc was indeed located on Archaean continental crust, rather than in Mesoproterozoic, intra-oceanic island arcs. The age spectrum of the zircons bears strong evidence for (i) derivation of the entire Ritscherflya sediment sequence from an active continental convergent margin; (ii) a cratonic provenance of part of the sediments from population peaks coinciding with major tectono-thermal events in the Kalahari Craton; (iii) at least some of the active volcanism being located on cratonic basement rather than a juvenile island arc. Detrital zircons in the ~1130 Ma age group show several distinct populations in their Hf isotopic compositions. The dominant group shows negative ɛHf values of -11.5 corresponding to a model age (TDM) of ~2700 Ma (average crustal 176Lu/177Hf = 0.015). A smaller group shows ɛHf values of +2 to +6, which may represent mantle-derived subduction-zone volcanism at

  16. Early impact basins and the onset of plate tectonics. Ph.D. Thesis - Maryland Univ.

    NASA Technical Reports Server (NTRS)

    Frey, H.

    1977-01-01

    The fundamental crustal dichotomy of the Earth (high and low density crust) was established nearly 4 billion years ago. Therefore, subductable crust was concentrated at the surface of the Earth very early in its history, making possible an early onset for plate tectonics. Simple thermal history calculations spanning 1 billion years show that the basin forming impact thins the lithosphere by at least 25%, and increases the sublithosphere thermal gradients by roughly 20%. The corresponding increase in convective heat transport, combined with the highly fractured nature of the thinned basin lithosphere, suggest that lithospheric breakup or rifting occurred shortly after the formation of the basins. Conditions appropriate for early rifting persisted from some 100,000,000 years following impact. We suggest a very early stage of high temperature, fast spreading "microplate" tectonics, originating before 3.5 billion years ago, and gradually stabilizing over the Archaean into more modern large plate or Wilson Cycle tectonics.

  17. Oceanic plateau model for continental crustal growth in the Archaean: A case study from the Kostomuksha greenstone belt, NW Baltic Shield

    NASA Astrophysics Data System (ADS)

    Samsonov, A. V.; Shchipansky, A. A.; Jochum, K. P.; Mezger, K.; Hofmann, A. W.; Puchtel, I. S.

    1998-02-01

    Field studies combined with chemical and isotope data indicate that the Kostomuksha greenstone belt in the NW Baltic Shield consists of two lithotectonic terranes, one mafic igneous and the other sedimentary, separated by a major shear zone. The former contains submarine komatiite-basalt lavas and volcaniclastic lithologies, and the latter is composed of shelf-type rocks and BIF. Komatiitic and basaltic samples yield Sm-Nd and Pb-Pb isochron ages of 2843+/-39 and 2813+/-78 Ma, respectively. Their trace-element compositions resemble those of recent Pacific oceanic flood basalts with primitive-mantle normalized Nb/Th of 1.5-2.1 and Nb/La of 1.0-1.5. This is in sharp contrast with island arc and most continental magmas, which are characterized by Nb/(Th,La)N≪1. Calculated initial Nd-isotope compositions (ɛNd(T)=+2.8 to +3.4) plot close to an evolution line previously inferred for major orogens (``MOMO''), which is also consistent with the compositions of recent oceanic plateaux. The high liquidus temperatures of the komatiite magmas (1550°C) and their Al-depleted nature require an unusually hot (1770°C) mantle source for the lavas (>200°C hotter than the ambient mantle at 2.8 Ga), and are consistent with their formation in a deep mantle plume in equilibrium with residual garnet. This plume had the thermal potential to produce oceanic crust with an average thickness of ~30 km underlain by a permanently buoyant refractory lithospheric mantle keel. Nb/U ratios in the komatiites and basalts calculated on the basis of Th-U-Pb relationships range from 35 to 47 and are thus similar to those observed in modern MORB and OIB. This implies that some magma source regions of the Kostomuksha lavas have undergone a degree of continental material extraction comparable with those found in the modern mantle. The mafic terrane is interpreted as a remnant of the upper crustal part of an Archaean oceanic plateau. When the newly formed plateau reached the active continental margin

  18. Oceanic plateau model for continental crustal growth in the Archaean: A case study from the Kostomuksha greenstone belt, NW Baltic Shield

    NASA Astrophysics Data System (ADS)

    Puchtel, I. S.; Hofmann, A. W.; Mezger, K.; Jochum, K. P.; Shchipansky, A. A.; Samsonov, A. V.

    1998-02-01

    Field studies combined with chemical and isotope data indicate that the Kostomuksha greenstone belt in the NW Baltic Shield consists of two lithotectonic terranes, one mafic igneous and the other sedimentary, separated by a major shear zone. The former contains submarine komatiite-basalt lavas and volcaniclastic lithologies, and the latter is composed of shelf-type rocks and BIF. Komatiitic and basaltic samples yield Sm-Nd and Pb-Pb isochron ages of 2843±39 and 2813±78 Ma, respectively. Their trace-element compositions resemble those of recent Pacific oceanic flood basalts with primitive-mantle normalized Nb/Th of 1.5-2.1 and Nb/La of 1.0-1.5. This is in sharp contrast with island arc and most continental magmas, which are characterized by Nb/(Th,La) N≪1. Calculated initial Nd-isotope compositions ( ɛNd( T)=+2.8 to +3.4) plot close to an evolution line previously inferred for major orogens ("MOMO"), which is also consistent with the compositions of recent oceanic plateaux. The high liquidus temperatures of the komatiite magmas (1550°C) and their Al-depleted nature require an unusually hot (1770°C) mantle source for the lavas (>200°C hotter than the ambient mantle at 2.8 Ga), and are consistent with their formation in a deep mantle plume in equilibrium with residual garnet. This plume had the thermal potential to produce oceanic crust with an average thickness of ˜30 km underlain by a permanently buoyant refractory lithospheric mantle keel. Nb/U ratios in the komatiites and basalts calculated on the basis of Th-U-Pb relationships range from 35 to 47 and are thus similar to those observed in modern MORB and OIB. This implies that some magma source regions of the Kostomuksha lavas have undergone a degree of continental material extraction comparable with those found in the modern mantle. The mafic terrane is interpreted as a remnant of the upper crustal part of an Archaean oceanic plateau. When the newly formed plateau reached the active continental margin

  19. Determined Initial lead for South Of Isua (SOI) terrain suggests a single homogeneous source for it and possibly other archaean rocks

    NASA Astrophysics Data System (ADS)

    Tera, F.

    2011-12-01

    other rocks from Isua Greenstone Belt (1) and Amîtsoq gneiss (4) fall inside the TULIP triangle of SOI, suggesting potential derivation of these Archaean rocks from the same homogeneous source.

  20. Analysis of tectonic movements utilizing remote sensor products in the Southern Espinhaco (SE) region

    NASA Astrophysics Data System (ADS)

    Veneziani, Paulo; Tavaresdemattos, Juercio; Ohara, Tomoyuki

    1989-06-01

    The area under study, the Southern Espinhaco Region, Minas Gerais State, Brazil, comprises metasedimentary sequences of Proterozoic, a typical granite-greenstone belt of Archaean age, gneiss, mignatites, granulites, and metasedimentary, and mafic to felsic units attributed to undifferentiated Precambrian. The region suffered a complex geologic evolution, including polycyclic and polymetamorphic events. Deformations occurred during the deposition of sediments (synsedimentary) due to compressive forces acting repeatedly during the geologic history of the region, resulting in superimposed orogenesis. The ruptile, ruptile-ductile tectonics that were part of different events registered in the petrographic and structural record were analyzed by LANDSAT (MSS, RBV, and TM) and radar images, aeromagnetic data, and field work. The main results of this research are: identification of 7 sets of joint zones which are controlled along N-S, EW and NW-SE directions during the Archaean to Late Proterozoic events; identification of sinistral transcurrent movements along N50-60W lineaments during the compressive phase of Late Proterozoic; occurrence of different tectonic movements (compression and tension) along the main directions of fracturing; finally the analysis of lithostratigraphic and fracturing data permits to envisage the geologic history of Proterozoic evolution of the region characterized by mechanism compatible to intraplate tectonic movements (ensialic environment).

  1. Contribution to the geochronology of the basement of the Central African Republic

    NASA Astrophysics Data System (ADS)

    Lavreau, J.; Poidevin, J. L.; Ledent, D.; Liegeois, J. P.; Weis, D.

    The age and isotope geology of the most striking geological elements of the basement in the south-central CAR have been investigated. The granite-greenstone belts of Bandas and Dekoa, as well as the amphibolitic complexes and associated gneisses of the Ouham and the Mbomou rivers, belong to the Archaean period. Granitic bodies intruding the post-Archaean Quartzito-schistose or "intermediate" series are of Lower Proterozoic Eburnean age. All former units have suffered on a limited scale from the Panafrican reactivation, as they belong to autochtonous areas constituting either a foreland or lateral ramps relatively to thrust belts developing during the latter period. The granulitic areas of central CAR are of Panafrican age. They have, together with the associated gneisses, been tectonized during the same period of orogeny. The granulites result from the remobilization of a crustal segment of Lower Proterozoic or older age. As a result of this tectonic complexity, it is no longer licit to put all the granulitic and gneissic series of the CAR in a single stratigraphic unit.

  2. High-K calc-alkaline magmatism at the Archaean-Proterozoic boundary: implications for mantle metasomatism and continental crust petrogenesis. Example of the Bulai pluton (Central Limpopo Belt, South Africa)

    NASA Astrophysics Data System (ADS)

    Laurent, Oscar; Martin, Hervé; Doucelance, Régis; Moyen, Jean-François; Paquette, Jean-Louis

    2010-05-01

    The Neoarchaean Bulai pluton, intrusive within the supracrustal granulites of the Central Limpopo Belt (Limpopo Province, South Africa) is made up of large volumes of porphyritic granodiorites with subordinate enclaves and dykes which have monzodioritic and charno-enderbitic compositions. New U-Pb LA-ICP-MS dating on separated zircons yielded pluton emplacement ages ranging between 2.60 and 2.63 Ga, which are slightly older than previous proposed ages (~ 2.57-2.61 Ga). The whole-rock major- and trace-element composition of the Bulai pluton evidences unequivocal affinities with "high-Ti" late-Archaean sanukitoids. It belongs to a high-K calc-alkaline differentiation suite, with metaluminous affinities (0.7 < A/CNK < 1) and relatively high Mg# (0.4-0.6). These rocks have "juvenile" affinities, such as eNd ranging between -0.5 and 0.5, and in addition, are very rich in all incompatible trace elements, which is particularly obvious in monzodioritic enclaves and enderbites where primitive mantle-normalized LILE and LREE contents are up to 300. These characteristics point to an enriched mantle source for the Bulai batholith. Chondrite normalized, REE patterns are strongly fractionated ([La/Yb]N ~ 25-80), mainly due to high LREE contents (LaN ~ 250-630), and chiefly high HFSE contents (Nb ~ 15-45 ppm ; up to 770 ppm Zr) indicate that the metasomatic agent is a silicic melt rather than a hydrous fluid. Moreover, based on high Nb/Ta, Th/Rb, La/Rb and low Sr/Nd and Ba/La, we suggest that the metasomatic agent is a granitic melt generated by melting of terrigenous sediments. Interactions of this melt with mantle peridotites implies that sediments are located under a mantle slice; geometry which is easily achieved in subduction zone settings. This conclusion is supported by the fact that Bulai trace element patterns are very similar to those of sub-actual potassic magmas generated in magmatic arc environments by interactions between mantle and terrigenous sediments (e.g. Sunda

  3. Contrasting geochemistry of arc-related metagranitoids in the Kerala Khondalite Belt, southern India: evidence for flat to steep transition in subduction style at the end of the Archaean

    NASA Astrophysics Data System (ADS)

    Gr, R.; Chettootty, S.

    2012-12-01

    The Kerala Khondalite Belt (KKB) occupying southernmost part of the south Indian granulite terrain (SGT) is characterized by the presence of high-grade metagranitoids equilibrated at granulite-facies (ca. 7 to 9.5 kbar and 840-1070 °C) conditions. The mechanisms of granulite genesis within the SGT are poorly understood as these metagranitoids have not been unequivocally correlated to the important evolutionary models applicable to granulite genesis like crustal thickening during continental collision or magmatic underplating. Recent studies suggesting subduction-accretion-collision geodynamic model for the genesis of KKB metagranitoids implores the role of classical mechanisms for the petrogenesis of granulites in this region. In this contribution, we present and synthesize the contrasting major, trace, and REE geochemical patterns of tonalitic and high-K granitic rocks of the KKB as a consequence of the change in geodynamic setting. The contrasting granitoid groups of the KKB comprise (i) tonalites with characteristic Archaean tonalite-trondhjemite-granodiorite (TTG) affinity and (ii) high-K granites showing geochemical patterns archetypal of the post-Archaean granites. The tonalite groups show low-K, magnesian character with moderate to high SiO2 (57-76 wt.%) contents, moderate LREE (average LaN = 154), low HREE (average YbN = 6), characteristic high Sr/Y (27-934; average 331) and high [La/Yb]N (average 39) ratios, and strongly positive and/or no europium (Eu/Eu* = 0.7 to 1.67) anomalies. The geochemical features suggests that protolith for the tonalites are derived from partial melting of a subducting slab/thickened lower continental crust composed of mafic composite source rocks (eclogitic or basaltic crust) in the Neoarchaean (ca. 2.73-2.89 Ga). The absence of volcanism associated with the tonalite genesis possibly indicates that the subducting lithosphere was an old and cold plate. On contrary, the high-K granite group show ferroan nature, low to moderate

  4. Tectonomagmatic evolution of the Archaean basement of the Quadrilátero Ferrífero province (southeast Brazil): the tonalite-trondhjemite-granodiorite (TTG) to calc-alkaline granodiorite-granite transition

    NASA Astrophysics Data System (ADS)

    Farina, Federico; Albert, Capucine; Lana, Cristiano; Stevens, Gary; Moreira, Hugo; Hippertt, João Pedro

    2014-05-01

    The Archaean Southern São Francisco craton (Quadrilátero Ferrífero, Brazil) is a typical dome-and-keel province characterized by kilometer-scale gneiss-granitic domes surrounded by elongated keels of folded supracrustal rocks. The tectonomagmatic evolution of the three largest domes in the craton (namely the Bação, Bonfim and Belo Horizonte domes) occurred between 3200 and 2700 Ma. The domes expose several phases of TTG gneisses and plutons intruded by leucogranite sheets, pegmatitic dykes and bodies of calc-alkaline ("potassic") granodiorite and granite. LA-ICP-MS zircon U-Pb data allow three main periods of magmatism to be defined. These are described as the Santa Barbara (SB), Rio das Velhas I (RVI) and Rio das Velhas II (RVII) events (Lana et al., 2013). The oldest discernable evolution of the craton began at 3200 Ma (SB event) with the formation of TTG gneisses that are poorly preserved in the exposed record. This event is also attested by the occurrence of inherited zircons in younger TTGs as well as by the fact that zircons with a ca. 3200 Ma age represent a significant subset in the detrital zircon population of the greenstone belt succession. This evidence suggests that the Palaeoarchaean TTG crust has been reworked as well as eroded during tectonic denudation. The following magmatic event (RVI), which generated most of the TTG crust of the Southern São Francisco craton, took place between 2930-2870 Ma. Gneisses formed during this event have geochemical features similar to the middle-pressure TTG group defined by Moyen (2010) suggesting that they formed in equilibrium with a garnet-rich, plagioclase-poor amphibole-bearing residuum. These TTGs have K2O/Na2O between 0.3 and 0.7, Sr content between 250-500 ppm and Sr/Y lower than 150. Finally, the RVII event occurred between 2780-2700 Ma producing both TTG-like) and potassic (calc-alkaline) granitoids. In particular, calc-alkaline granitoids, distributed over an area of ˜25,000 km2, were emplaced

  5. Atmospheric composition and climate on the early Earth.

    PubMed

    Kasting, James F; Howard, M Tazewell

    2006-10-29

    Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85 degrees C. We argue, following others, that this interpretation is incorrect-the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot.A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4Ga were probably caused by the rise of atmospheric O2 and a concomitant decrease in greenhouse warming by CH4. Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere.

  6. Atmospheric composition and climate on the early Earth

    PubMed Central

    Kasting, James F; Howard, M. Tazewell

    2006-01-01

    Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85°C. We argue, following others, that this interpretation is incorrect—the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot. A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4 Ga were probably caused by the rise of atmospheric O2 and a concomitant decrease in greenhouse warming by CH4. Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9 Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere. PMID:17008214

  7. Relationship between high- and low-grade Archean terranes: Implications for early Earth paleogeography

    NASA Technical Reports Server (NTRS)

    Eriksson, K. A.

    1986-01-01

    The Western Gneiss Terrain (WGT) of the Yilgarn Block, Western Australia was studied. The WGT forms an arcuate belt of Archean gneisses that flank the western margin of the Yilgarn Block. In general the WGT is composed of high-grade orthogneisses and paragneisses which contain supracrustal belts composed largely of siliciclastic metasediments and subordinate iron formation. The platformal nature of the metasedimentary belts and lack of obvious metavolcanic lithologies contrasts with the composition of typical Yilgarn greenstones to the east. Radiometric data from WGT rocks indicates that these rocks are significantly older than Yilgarn rocks to the east (less than 3.3 Ga) and this has led to the suggestion that the WGT represents sialic basement to Yilgarn granite-greenstone belts. The Mount Narryer region exposes the northernmost occurrence of high-grade metasediments within the WGT and consists of quartz-rich clastic metasediments at upper amphibolite to granulite grade. Most occurrences of supracrustal rocks in this region comprise isolated lenses within the gneissic basement. However, at Mount Narryer a unique sequence of metaclastics with preserved bedding provide an unusual window into the parentage of similar supracrustal bodies in this region.

  8. Granitic rocks and metasediments in Archean crust, Rainy Lake area, Ontario: ND isotope evidence for mantle-like SM/ND sources

    NASA Technical Reports Server (NTRS)

    Shirey, S. B.; Hanson, G. N.

    1983-01-01

    Granitoids, felsic volcanic rocks and clastic metasediments are typical rocks in Archean granite-greenstone belts that could have formed from preexisting continentasl crust. The petrogenesis of such rocks is assessed to determine the relative roles of new crust formation or old crust formation or old crust recycling in the formation of granite-greenstone belts.

  9. Buds from the tree of life: linking compartmentalized prokaryotes and eukaryotes by a non-hyperthermophile common ancestor and implications for understanding Archaean microbial communities

    NASA Astrophysics Data System (ADS)

    Fuerst, John A.; Nisbet, Euan G.

    2004-07-01

    The origin of the first nucleated eukaryote and the nature of the last common ancestor of the three domains of life are major questions in the evolutionary biology of cellular life on Earth, the solutions to which may be linked. Planctomycetes are unusual compartmentalized bacteria that include a membrane-bounded nucleoid. The possibility that they constitute a very deep branch of the domain Bacteria suggests a model for the evolution of the three domains of life from a last common ancestor that was a mesophile or moderate thermophile with a compartmentalized eukaryote-like cell plan. Planctomycetes and some members of the domain Archaea may have retained cell compartmentalization present in an original eukaryote-like last common ancestor of the three domains of life. The implications of this model for possible habitats of the early evolution of domains of cellular life and for interpretation of geological evidence relating to those habitats and the early emergence of life are examined here.

  10. Origin and evolution of the Amazonian craton

    NASA Technical Reports Server (NTRS)

    Gibbs, A. K.; Wirth, K. R.

    1986-01-01

    The Amazonian craton appears to be formed and modifed by processes much like those of the better-known Precambrian cratons, but the major events did not always follow conventional sequences nor did they occur synchronously with those of other cratons. Much of the craton's Archean style continental crust formation, recorded in granite-greenstone and high-grade terranes, occurred in the Early Proterozoic: a period of relative quiescence in many other Precambrian regions. The common Archean to Proterozoic transition in geological style did not occur here, but an analogous change from abundant marine volcanism to dominantly continental sedimentary and eruptive styles occurred later. Amazonian geology is summarized, explaining the evolution of the craton.

  11. Late Archaean crust-mantle interactions: geochemistry of LREE-enriched mantle derived magmas. Example of the Closepet batholith, southern India

    NASA Astrophysics Data System (ADS)

    Jayananda, M.; Martin, H.; Peucat, J.-J.; Mahabaleswar, B.

    1995-03-01

    The Closepet batholith in South India is generally considered as a typical crustal granite emplaced 2.5 Ga ago and derived through partial melting of the surrounding Peninsular Gneisses (3.3 to 3.0 Ga). In the field, it appears as a composite batholith made up of at least two groups of intrusions. (a) An early SiO2-poor group (clinopyroxene quartz-monzonite and porphyritic phyritic monzogranite) is located in the central part of the batholith. These rocks display a narrow range in both initial 87Sr/86Sr (0.7017 0.7035) and ɛNd(-0.9to -4.1). (b) A later SiO2-rich group (equigranular grey and pink granites) is located along the interface between the SiO2-poor group and the Peninsular Gneisses. They progressively grade into migmatised Peninsular Gneisses, thus indicating their anatectic derivation. Their isotopic characteristics vary over a wide range (87Sr/86Sr ratios=0.7028 0.7336 and ɛNd values from-2.7 to-8.3, at 2.52 Ga). Field and geochronological evidence shows that the two groups are broadly contemporaneous (2.518 2.513 Ga) and mechanically mixed. This observation is supported by the chemical data that display well defined mixing trends in the ɛSr vs ɛNd and elemental variation diagrams. The continuous chemical variation of the two magmatic bodies is interpreted in terms of interaction and mixing of two unrelated end-members derived from different source regions (enriched peridotitic mantle and Peninsular Gneisses). It is proposed that the intrusion of mantle-derived magmas into mid-crustal levels occurred along a transcurrent shear zone; these magmas supplied additional heat and fluids that initiated anatexis of the surrounding crust. During this event, large-scale mixing occurred between mantle and crustal melts, thus generating the composite Closepet batholith. The mantle-derived magmatism is clearly associated with granulite facies metamorphism 2.51±0.01 Ga ago. Both are interpreted as resulting from a major crustal accretion event, possibly related

  12. Generation of an Archaean H/sub 2/O-CO/sub 2/ fluid enriched in Au, W and Mo by fractional crystallization in the Mink Lake intrusion, NW Ontario

    SciTech Connect

    Burrows, D.R.; Spooner, E.T.C.

    1985-01-01

    Fractional crystallization (FC) of the post-tectonic trondhjemitic Mink Lake intrusion in NW Ontario resulted in a residual H/sub 2/O-CO/sub 2/ low salinity fluid with an isotopic composition (delta /sup 13/C/sub cc/ x = -3.3 per thousand +/- 0.4 per thousand (1s), delta/sup 18/O/sub cc/ + 10.7 to 15.9 per thousand, deltaD/sub FI/ -70 +/- 9 per thousand (1s) and delta /sup 34/S/sub py/ +0.4 to +2.90 per thousand) compatible with magmatic derivation and extremely similar to that in vein quartz-carbonate-pyrite +/- scheelite, +/- tourmaline, +/- MoS/sub 2/ +/- telluride systems characteristic of major Archaean lode gold deposits. Inward FC of the granodiorite magma (69-71% SiO/sub 2/, Na/sub 2/O/K/sub 2/O = 1.6-3.9), as indicated by trace and REE data, produced a sequence of microgranites and aplitic dykes with mean values by INNA (n=10) for Au of 2.3ppb, Mo = 22ppm and W = 7.3ppm as compared to mean background values in the granodiorite of Au <1ppb, Mo less than or equal to 1ppm with W less than or equal to 3.7ppm (n=4). The latest aplites are observed to coexist with a H/sub 2/O-CO/sub 2/ mixture and are characterized by carbonate alteration selvages and minor MoS/sub 2/. Subsequent separation of the H/sub 2/O-CO/sub 2/ fluid and interaction with an otherwise fresh granodiorite within the already solidified southern margin, produced MoS/sub 2/ mineralized sub-horizontal quartz veins and larger tabular lenses of carbonate alteration without internal veining. Such zones are anomalously enriched (n=10) in Au (anti x = 153 pbb, range 2-570ppb) Mo (anti x 660ppm, range 1-2500ppm and W (anti x = 61 ppm, range 23-95 ppm).

  13. The Tonalite-Trondhjemite-Granodiorite (TTG) to Calc-alkaline Granodiorite-Granite Transition: Evolution of the Archaean Basement of the Quadrilátero Ferrífero Province (Southeast Brazil)

    NASA Astrophysics Data System (ADS)

    Farina, F.; Albert, C.; Lana, C.; Stevens, G.

    2014-12-01

    The Bação, Bonfim and Belo Horizonte domes are the largest domes in the Archaean Southern São Francisco craton (Quadrilátero Ferrífero, Brazil). These domes are mainly formed by fine-grained banded gneisses typically intruded by leucogranitic veins and by weakly foliated granites, cropping out as large batholiths and small scale-domains closely associated to the gneisses. Granites and gneisses have high silica content (70-76 wt%), K2O ranging from 2wt% to 6wt%, Sr from 600 to 40 ppm and La/Yb from 150 to 5. Based on their K2O/Na2O ratios, these rocks are subdivided in three groups: sodic (K2O/Na2O≤0.7), transitional (0.7

  14. An Early, Transient, Impact-driven Tectonic Regime in the Hadean?

    NASA Astrophysics Data System (ADS)

    O'Neill, C.; Marchi, S.; Zhang, S.

    2015-12-01

    The earliest preserved crust formed in a tectonic regime that different from present in several significant ways. Earth was still losing a significant fraction of its primordial heat, and heat production was declining more rapidly than in any period subsequently. Additionally, a waning impact flux provided an important thermal - and mechanical - forcing on the early Earth. These factors affect tectonics in a number of ways - internal velocities are faster, and internal viscosities lower due to hotter internal temperatures. Previous modelling of the tectonic evolution of the Earth under these conditions suggests that the early Earth may have exhibited periods of hot stagnant-lid convection - where vigorous internal convection - and volcanic activity - occurred under a tectonically quiescent lid. As the Earth cooled the planet would have transited into an episodic regime - characterised by periods of tectonic quiescence interspersed by extreme tectonic activity. Such scenarios explain a number of facets of the early Earth, including its observed slow mixing rates, inefficient cooling, and its paleomagnetic and tectonic history. Here we expand these models to incorporate the effects of major impacts. We find tectonic forcing due to impacts to be a major dynamic driver during the Hadean, with major return flow driving horizontal surface deformation, and transient subduction events. Such events may be reflected in the Hadean zircon record. Post this impact-dominated phase, models suggest an over-heated Earth may have then experienced a long phase of stagnant-lid convection, lasting till the meso-Archaean.

  15. Early Earth

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2015-05-01

    Earth has continents, subduction and mobile lid plate tectonics, but details of the early evolution are poorly understood. Here I summarize the Hadean-Archean record, review evidence for a hotter Earth and consider geodynamic models for early Earth.

  16. [Early Intervention.

    ERIC Educational Resources Information Center

    Pawl, Jeree, Ed.

    1992-01-01

    This newsletter focuses on the theme of early intervention which infants and young children with special needs in nine brief articles: "Early Intervention: A Matter of Context" (Samuel J. Meisels); "Early Intervention Research: Asking and Answering Meaningful Questions" (Jack P. Shonkoff); "From Case Management to Service…

  17. Hf-Nd isotope evidence for a transient dynamic regime in the early terrestrial mantle

    PubMed

    Albarede; Blichert-Toft; Vervoort; Gleason; Rosing

    2000-03-30

    Modern basalts have seemingly lost all 'memory' of the primitive Earth's mantle except for an ambiguous isotopic signal observed in some rare gases. Although the Earth is expected to have reached a thermal steady state within several hundred million years of accretion, it is not known how and when the initial chemical fractionations left over from planetary accretion (and perhaps a stage involving a magma ocean) were overshadowed by fractionations imposed by modern-style geodynamics. Because of the lack of samples older than 4 Gyr, this early dynamic regime of the Earth is poorly understood. Here we compare published Hf-Nd isotope data on supracrustals from Isua, Greenland, with similar data on lunar rocks and the SNC (martian) meteorites, and show that, about 3.8 Gyr ago, the geochemical signature of the Archaean mantle was partly inherited from the initial differentiation of the Earth. The observed features seem to indicate that the planet at that time was still losing a substantial amount of primordial heat. The survival of remnants from an early layering in the modern deep mantle may account for some unexplained seismological, thermal and geochemical characteristics of the Earth as observed today.

  18. Effects of differentiation on the geodynamics of the early Earth

    NASA Astrophysics Data System (ADS)

    Piccolo, Andrea; Kaus, Boris; White, Richard; Johnson, Tim

    2016-04-01

    Archean geodynamic processes are not well understood, but there is general agreement that the mantle potential temperature was higher than present, and that as a consequence significant amounts of melt were produced both in the mantle and any overlying crust. This has likely resulted in crustal differentiation. An early attempt to model the geodynamic effects of differentiation was made by Johnson et al. (2014), who used numerical modeling to investigate the crust production and recycling in conjunction with representative phase diagrams (based on the inferred chemical composition of the primary melt in accordance with the Archean temperature field). The results of the simulations show that the base of the over-thickened primary basaltic crust becomes gravitational unstable due to the mineral assemblage changes. This instability leads to the dripping of dense material into the mantle, which causes an asthenospheric return flow, local partial melting and new primary crust generation that is rapidly recycled in to mantle. Whereas they gave important insights, the previous simulations were simplified in a number of aspects: 1) the rheology employed was viscous, and both elasticity and pressure-dependent plasticity were not considered; 2) extracted mantle melts were 100% transformed into volcanic rocks, whereas on the present day Earth only about 20-30% are volcanic and the remainder is plutonic; 3) the effect of a free surface was not studied in a systematic manner. In order to better understand how these simplifications affect the geodynamic models, we here present additional simulations to study the effects of each of these parameters. Johnson, T.E., Brown, M., Kaus, B., and VanTongeren, J.A., 2014, Delamination and recycling of Archaean crust caused by gravitational instabilities: Nature Geoscience, v. 7, no. 1, p. 47-52, doi: 10.1038/NGEO2019.

  19. Early Risers

    ERIC Educational Resources Information Center

    Asquith, Chistina

    2002-01-01

    In this article, the author features Bard High School Early College, the first public school in the country to offer a free, full-time college curriculum--and all the credits that go with it--to high schoolers. In Bard's four-year program, students race through high school requirements in 9th and 10th grades, then take college courses in 11th and…

  20. Volcaniclastic habitats for early life on Earth and Mars: A case study from ˜3.5 Ga-old rocks from the Pilbara, Australia

    NASA Astrophysics Data System (ADS)

    Westall, Frances; Foucher, Frédéric; Cavalazzi, Barbara; de Vries, Sjoukje T.; Nijman, Wouter; Pearson, Victoria; Watson, Jon; Verchovsky, Alexander; Wright, Ian; Rouzaud, Jean-Noel; Marchesini, Daniele; Anne, Severine

    2011-08-01

    Within the context of present and future in situ missions to Mars to investigate its habitability and to search for traces of life, we studied the habitability and traces of past life in ˜3.5 Ga-old volcanic sands deposited in littoral environments an analogue to Noachian environments on Mars. The environmental conditions on Noachian Mars (4.1-3.7 Ga) and the Early Archaean (4.0-3.3 Ga) Earth were, in many respects, similar: presence of liquid water, dense CO 2 atmosphere, availability of carbon and bio-essential elements, and availability of energy. For this reason, information contained in Early Archaean terrestrial rocks concerning habitable conditions (on a microbial scale) and traces of past life are of relevance in defining strategies to be used to identify past habitats and past life on Mars. One such example is the 3.446 Ga-old Kitty's Gap Chert in the Pilbara Craton, NW. Australia. This formation consists of volcanic sediments deposited in a coastal mudflat environment and is thus a relevant analogue for sediments deposited in shallow water environments on Noachian Mars. Two main types of habitat are represented, a volcanic (lithic) habitat and planar stabilized sediment surfaces in sunlit shallow waters. The sediments hosted small (<1 μm in size) microorganisms that formed colonies on volcanic particle surfaces and in pore waters within the volcanic sediments, as well as biofilms on stabilised sediment surfaces. The microorganisms included coccoids, filaments and rare rod-shaped organisms associated with microbial polymer (EPS). The preserved microbial community was apparently dominated by chemotrophic organisms but some locally transported filaments and filamentous mat fragments indicate that possibly photosynthetic mats formed nearby. Both microorganisms and sediments were silicified during very early diagenesis. There are no macroscopic traces of fossilised life in these volcanic sediments and sophisticated instrumentation and specialized sample

  1. Early Astronomy

    NASA Astrophysics Data System (ADS)

    Thurston, Hugh

    The earliest investigations that can be called scientific are concerned with the sky: they are the beginnings of astronomy. Many early civilizations produced astronomical texts, and several cultures that left no written records left monuments and artifacts-ranging from rock paintings to Stonehenge-that show a clear interest in astronomy. Civilizations in China, Mesopotamia, India and Greece had highly developed astronomies, and the astronomy of the Mayas was by no means negligible. Greek astronomy, as developed by the medieval Arab philosophers, evolved into the astronomy of Copernicus. This displaced the earth from the central stationary position that almost all earlier astronomies had assumed. Soon thereafter, in the first decades of the seventeenth century, Kepler found the true shape of the planetary orbits and Galileo introduced the telescope for astronomical observations.

  2. Early Pregnancy Loss

    MedlinePlus

    ... is called early pregnancy loss , miscarriage , or spontaneous abortion . How common is early pregnancy loss? Early pregnancy ... testes that can fertilize a female egg. Spontaneous Abortion: The medical term for early pregnancy loss. Trimester: ...

  3. Identifying early Earth microfossils in unsilicified sediments

    NASA Astrophysics Data System (ADS)

    Javaux, Emmanuelle J.; Asael, Dan; Bekker, Andrey; Debaille, Vinciane; Derenne, Sylvie; Hofmann, Axel; Mattielli, Nadine; Poulton, Simon

    2013-04-01

    The search for life on the early Earth or beyond Earth requires the definition of biosignatures, or "indices of life". These traditionally include fossil molecules, isotopic fractionations, biosedimentary structures and morphological fossils interpreted as remnants of life preserved in rocks. This research focuses on traces of life preserved in unsilicified siliciclastic sediments. Indeed, these deposits preserve well sedimentary structures indicative of past aqueous environments and organic matter, including the original organic walls of microscopic organisms. They also do not form in hydrothermal conditions which may be source of abiotic organics. At our knowledge, the only reported occurrence of microfossils preserved in unsilicified Archean sediments is a population of large organic-walled vesicles discovered in shales and siltstones of the 3.2 Ga Moodies Group, South Africa. (Javaux et al, Nature 2010). These have been interpreted as microfossils based on petrographic and geochemical evidence for their endogenicity and syngeneity, their carbonaceous composition, cellular morphology and ultrastructure, occurrence in populations, taphonomic features of soft wall deformation, and the geological context plausible for life, as well as lack of abiotic explanation falsifying a biological origin. Demonstrating that carbonaceous objects from Archaean rocks are truly old and truly biological is the subject of considerable debate. Abiotic processes are known to produce organics and isotopic signatures similar to life. Spheroidal pseudofossils may form as self-assembling vesicles from abiotic CM, e.g. in prebiotic chemistry experiments (Shoztak et al, 2001), from meteoritic lipids (Deamer et al, 2006), or hydrothermal fluids (Akashi et al, 1996); by artifact of maceration; by migration of abiotic or biotic CM along microfractures (VanZuilen et al, 2007) or along mineral casts (Brasier et al, 2005), or around silica spheres formed in silica-saturated water (Jones and

  4. Archean geotherms and supracrustal assemblages

    NASA Astrophysics Data System (ADS)

    Condie, Kent C.

    1984-06-01

    Metamorphic mineral assemblages suggest the existence of variable geotherms and lithospheric thicknesses beneath late Archean continental crust. Archean granite-greenstone terranes reflect steep geotherms (50-70°C/km) while high-grade terranes reflect moderate geotherms similar to present continental crust with high heat flow (25-40°C/km). Corresponding lithosphere thicknesses for each terrane during the late Archean are 35-50 km and 50-75 km, respectively. Early Archean (⩾ 3.0 b.y.) greenstones differ from late Archean (˜ 2.7 b.y.) greenstones by the rarity or absence of andesite and graywacke and the relative abundance of pelite, quartzite, and komatiite. Mature clastic sediments in early greenstones reflect shallow-water, stable-basin deposition. Such rocks, together with granite-bearing conglomerate and felsic volcanics imply the existence of still older granitic source terranes. The absence or rarity of andesite in early greenstones reflects the absence of tectonic conditions in which basaltic and tonalitic magmas are modified to produce andesite. A model is presented in which early Archean greenstones form at the interface between tonalite islands and oceanic lithosphere, over convective downcurrents; high-grade supracrustals form on stable continental edges or interiors; and late Archean greenstones form in intracontinental rifts over mantle plumes.

  5. U-Pb LA-ICP-MS detrital zircon ages from the Cambrian of Al Qarqaf Arch, central-western Libya: Provenance of the West Gondwanan sand sea at the dawn of the early Palaeozoic

    NASA Astrophysics Data System (ADS)

    Altumi, Muftah Mahmud; Elicki, Olaf; Linnemann, Ulf; Hofmann, Mandy; Sagawe, Anja; Gärtner, Andreas

    2013-03-01

    Detrital zircons from various stratigraphic levels of the sandstone-dominated Cambrian Hasawnah Formation of the Al Qarqaf Arch type area (central-western Libya, Saharan Metacraton area) were geochronologically investigated for the first time by LA-ICP-MS techniques for U, Th, and Pb isotopes. Of 720 analyzed grains, 329 were concordant. Of the total, about 60% of the U-Pb zircon ages are Neoproterozoic and earliest Cambrian and cluster at c. 700-680, 670-650, 615-610, 590, 570-560, and c. 540-525 Ma. These zircon populations are interpreted as detrital material derived from the Pan-African and possibly to a smaller proportion from the Cadomian orogen situated marginal to northwestern Gondwana. A few slightly older Neoproterozoic ages (c. 950-750 Ma) point to rifting events related to the dispersal of the Rodinia supercontinent. A minority of zircons became formed during the configuration of Rodinia and cluster around the Mesoproterozoic-Neoproterozoic boundary (1039 ± 11, 1006 ± 12 and 993 ± 13 Ma). Further, some early Mesoproterozoic zircon ages had been found (1592 ± 39 and 1475 ± 20 Ma). The potential source area for the Mesoproterozoic zircons is interpreted to have been far distant from the Al Qarqaf Arch, probably concealed within the Arabian-Nubian Shield or situated in Chad, or in the Congo and Tanzania cratons. There is still no evidence for the existence of massive Mesoproterozoic crust in the Saharan Metacraton area. A considerable proportion (28%) of zircons represents Palaeoproterozoic populations at c. 2.4-2.3 Ga, and c. 2.2-1.6 Ga. Less than 5% of all zircons are Archaean in age (c. 3.4-3.25 Ga, c. 2.95-2.7 Ga, c. 2.6-2.5 Ga). A potential source area for Palaeoproterozoic and Archaean zircon grains is the West African Craton and the western part of the Saharan Metacraton. The best candidates for the main source region for the sandstones of the Hasawnah Formation in the Al Qarqaf Arch type area are the Neoproterozoic-early Cambrian orogens of

  6. Early Bilingual Reading.

    ERIC Educational Resources Information Center

    Titone, Renzo

    1985-01-01

    This discussion reviews literature on early bilingualism and early reading in two languages and summarizes a research project aimed at developing the experimental conditions for teaching early bilingual reading in institutional settings. The review notes positive effects of early reading generally and of early bilingual literacy on intellectual…

  7. Paleoenvironmental signals and paleoclimatic condition of the Early Maastrichtian oil shales from Central Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Fathy, Douaa; Wagreich, Michael; Zaki, Rafat; Mohamed, Ramadan S. A.

    2016-04-01

    Early Maastrichtian oil shales are hosted in the Duwi Formation of the Central Eastern Desert, Egypt. The examined member represents up to 20% of the total Duwi Formation. This interval is mainly composed of siliciclastic facies, phosphorites facies and carbonate facies. Oil shales microfacies is mainly composed of smectite, kaolinite, calcite, fluorapatite, quartz and pyrite. They are enriched in a number of major elements and trace metals in particular Ca, P, V, Ni, Cr, Sr, Zn, Mo, Nb, U and Y compared to the post-Archaean Australian shale (PAAS). Chondrite-normalized REEs patterns of oil shales for the studied area display light rare earth elements enrichment relatively to heavy rare earth elements with negative Ce/Ce* and Eu/Eu* anomalies. The most remarkable indicators for redox conditions are enrichments of V, Mo, Ni, Cr, U content and depletion of Mn content. Besides, V/V+Ni, V/Ni, U/Th, Ni/Co, authigentic uranium ratios with presence of framboidal shape of pyrite and its size are reflecting the deposition of these shales under marine anoxic to euxinic environmental conditions. Additionally, the ratio of Strontium (Sr) to Barium (Ba) Sr/Ba reflected highly saline water during deposition. Elemental ratios critical to paleoclimate and paleoweathering (Rb /Sr, Al2O3/TiO2), CIA values, binary diagram between (Al2O3+K2O+Na2O) and SiO2 and types of clay minerals dominated reflect warm to humid climate conditions prevailing during the accumulation of these organic-rich petroleum source rocks.

  8. Ultramafic Terranes and Associated Springs as Analogs for Mars and Early Earth

    NASA Technical Reports Server (NTRS)

    Blake, David; Schulte, Mitch; Cullings, Ken; DeVincezi, D. (Technical Monitor)

    2002-01-01

    Putative extinct or extant Martian organisms, like their terrestrial counterparts, must adopt metabolic strategies based on the environments in which they live. In order for organisms to derive metabolic energy from the natural environment (Martian or terrestrial), a state of thermodynamic disequilibrium must exist. The most widespread environment of chemical disequilibrium on present-day Earth results from the interaction of mafic rocks of the ocean crust with liquid water. Such environments were even more pervasive and important on the Archean Earth due to increased geothermal heat flow and the absence of widespread continental crust formation. The composition of the lower crust and upper mantle of the Earth is essentially the-same as that of Mars, and the early histories of these two planets are similar. It follows that a knowledge of the mineralogy, water-rock chemistry and microbial ecology of Earth's oceanic crust could be of great value in devising a search strategy for evidence of past or present life on Mars. In some tectonic regimes, cross-sections of lower oceanic crust and upper mantle are exposed on land as so-called "ophiolite suites." Such is the case in the state of California (USA) as a result of its location adjacent to active plate margins. These mafic and ultramafic rocks contain numerous springs that offer an easily accessible field laboratory for studying water/rock interactions and the microbial communities that are supported by the resulting geochemical energy. A preliminary screen of Archaean biodiversity was conducted in a cold spring located in a presently serpentinizing ultramafic terrane. PCR and phylogenetic analysis of partial 16s rRNA, sequences were performed on water and sediment samples. Archaea of recent phylogenetic origin were detected with sequences nearly identical to those of organisms living in ultra-high pH lakes of Africa.

  9. The oxidation state of Hadean magmas and implications for early Earth's atmosphere.

    PubMed

    Trail, Dustin; Watson, E Bruce; Tailby, Nicholas D

    2011-11-30

    Magmatic outgassing of volatiles from Earth's interior probably played a critical part in determining the composition of the earliest atmosphere, more than 4,000 million years (Myr) ago. Given an elemental inventory of hydrogen, carbon, nitrogen, oxygen and sulphur, the identity of molecular species in gaseous volcanic emanations depends critically on the pressure (fugacity) of oxygen. Reduced melts having oxygen fugacities close to that defined by the iron-wüstite buffer would yield volatile species such as CH(4), H(2), H(2)S, NH(3) and CO, whereas melts close to the fayalite-magnetite-quartz buffer would be similar to present-day conditions and would be dominated by H(2)O, CO(2), SO(2) and N(2) (refs 1-4). Direct constraints on the oxidation state of terrestrial magmas before 3,850 Myr before present (that is, the Hadean eon) are tenuous because the rock record is sparse or absent. Samples from this earliest period of Earth's history are limited to igneous detrital zircons that pre-date the known rock record, with ages approaching ∼4,400 Myr (refs 5-8). Here we report a redox-sensitive calibration to determine the oxidation state of Hadean magmatic melts that is based on the incorporation of cerium into zircon crystals. We find that the melts have average oxygen fugacities that are consistent with an oxidation state defined by the fayalite-magnetite-quartz buffer, similar to present-day conditions. Moreover, selected Hadean zircons (having chemical characteristics consistent with crystallization specifically from mantle-derived melts) suggest oxygen fugacities similar to those of Archaean and present-day mantle-derived lavas as early as ∼4,350 Myr before present. These results suggest that outgassing of Earth's interior later than ∼200 Myr into the history of Solar System formation would not have resulted in a reducing atmosphere.

  10. Plate tectonics hiati as the cause of global glaciations: 1. Early Proterozoic events and the rise of oxygen

    NASA Astrophysics Data System (ADS)

    Osmaston, M. F.

    2003-04-01

    Plate tectonics is the main way in which the Earth's internal heat is brought to the surface and lost, so it seems that global tectonics should not stop and start. Consequently the long-standing fact that, globally, no orogenic granitoid or greenstone U-Pb ages have been found in the 2.45--2.22 Ga interval has been attributed to defective sampling. Here I argue that this interval was indeed a prolonged hiatus in plate tectonics, being the first of two. The other, but differently caused, was in the late Proterozoic and is the topic of Part 2. The feature common to both hiati, and relevant to global glaciation, is that mid-ocean ridges (MORs) die and subside, potentially lowering sea-level by several kilometres, causing loss of atmospheric CO2 by weathering and an increase in planetary albedo. For the origin of the first hiatus we must first go back to formation of the core. The current iron-percolation model is invalidated by the fact that its corollary, the arrival of a water and siderophile-rich "late veneer" at the end of percolation, would be required to arrive some 60 Ma after the Moon, which never had a late veneer, was already in Earth orbit. The available alternative [1] would have given the early Earth a wet and low-viscosity convecting mantle able to dispose of the early heat with high efficiency; so that by 2.8 Ga MORs began to deepen, exposing cratons to massive weathering which lowered atmospheric CO2. The well-documented late Archaean acceleration of crustal addition to cratons, or, more precisely, of TTG-granitoid intrusion of greenstone belts, is also, paradoxically, evidence of waning mantle heat. Such wide-belt intrusion, grouped into quasi-coeval 'events', are examples of post-subduction magmatism (PSM), marking interruption of flat-slab subduction under a greenstone belt when a microcraton arrived [2]. On each occasion the TTG, derived from the subducted and reheated oceanic crust, advected subducting-plate heat to the surface that would

  11. Early Beginnings: Early Literacy Knowledge and Instruction

    ERIC Educational Resources Information Center

    National Institute for Literacy, 2009

    2009-01-01

    The National Early Literacy Panel was convened in 2002 to conduct a synthesis of the most rigorous scientific research available on the development of early literacy skills in children from birth to age 5. The primary purpose of the panel was to identify research evidence that would contribute to decisions in educational policy and practice that…

  12. Early Childhood Systems: Transforming Early Learning

    ERIC Educational Resources Information Center

    Kagan, Sharon Lynn, Ed.; Kauertz, Kristie, Ed.

    2012-01-01

    In this seminal volume, leading authorities strategize about how to create early childhood systems that transcend politics and economics to serve the needs of all young children. The authors offer different interpretations of the nature of early childhood systems, discuss the elements necessary to support their development, and examine how…

  13. Crustal-scale thrusting and origin of the Montreal River monocline-A 35-km-thick cross section of the midcontinent rift in northern Michigan and Wisconsin

    USGS Publications Warehouse

    Cannon, W.F.; Peterman, Z.E.; Sims, P.K.

    1993-01-01

    A structurally simple, 35-km-thick, north facing stratigraphic succession of Late Archean to Middle Proterozoic rocks is exposed near the Montreal River, which forms the border between northern Wisconsin and Michigan. This structure, the Montreal River monocline, is composed of steeply dipping to vertical sedimentary rocks and flood basalts of the Keweenawan Supergroup (Middle Proterozoic) along the south limb of the Midcontinent rift, and disconformably underlying sedimentary rocks of the Marquette Range Supergroup (Early Proterozoic). These rocks lie on an Archean granite-greenstone complex, about 10 km of which is included in the monocline. This remarkable thickness of rocks appears to be essentially structurally intact and lacks evidence of tectonic thickening or repetition.Tilting to form the monocline resulted from southward thrusting on listric faults of crustal dimension. The faults responsible for the monocline are newly recognized components of a well-known regional fault system that partly closed and inverted the Midcontinent rift system. Resetting of biotite ages on the upper plate of the faults indicates that faulting and uplift occurred at about 1060 +/−20 Ma and followed very shortly after extension that formed the Midcontinent rift system.

  14. Early Retirement Programs.

    ERIC Educational Resources Information Center

    Everett, Peter W.

    1984-01-01

    Early retirement programs offer individuals an alternative to the work ethic while allowing them to maintain job security. Examples are given of several early, partial, and phased retirement programs currently being used in universities and public school systems. (DF)

  15. Autism: Why Act Early?

    MedlinePlus

    ... What's this? Submit Button Past Emails CDC Features Autism: Why Act Early? Language: English Español (Spanish) Recommend ... helped the world make sense." Florida teenager with Autism Spectrum Disorder "Because my parents acted early, I ...

  16. Early Childhood Centers

    ERIC Educational Resources Information Center

    Butin, Dan; Woolums, Jennifer

    2009-01-01

    Early childhood centers have become a common and necessary part of millions of Americans' lives. More women in the workforce, longer workweeks, and educational research supporting the importance of early education have all contributed to the rise of early childhood centers throughout the United States. Today, more than 30 percent of children under…

  17. Reframing Early Childhood Leadership

    ERIC Educational Resources Information Center

    Stamopoulos, Elizabeth

    2012-01-01

    Rapid changes in Australian education have intensified the role of early childhood leaders and led to unprecedented challenges. The Australian Curriculum (ACARA, 2011), mandated Australian "National Quality Framework" (NQF) for Early Childhood Education & Care (DEEWR, 2010b) and the "National Early Years Learning Framework"…

  18. Early Perceptual Learning

    ERIC Educational Resources Information Center

    Goldstone, Robert L.; Son, Ji Y.; Byrge, Lisa

    2011-01-01

    Bhatt and Quinn (2011) present a compelling case that human learning is "early" in two very different, but interacting, senses. Learning is "developmentally" early in that even infants show strikingly robust adaptation to the structures present in their world. Learning is also early in an information processing sense because infants adapt their…

  19. Thrust exhumation of the Southern Marginal Zone of the Limpopo Complex in the Neoarchaean: link of distinct high-grade shear zones with DC and IC P-T-t paths

    NASA Astrophysics Data System (ADS)

    Smit, C. Andre; van Reenen, Dirk D.

    2010-05-01

    The Limpopo Complex is a ~750km long E-W trending zone of predominantly granulite facies rocks situated between the Archaean Kaapvaal and Zimbabwe cratons of southern Africa. Large ductile shear zones are an integral part of the Limpopo architecture, defining the boundaries between the belt and the adjacent cratons and are interpreted to have been responsible for uplift (exhumation) of over thickened crust during the Neoarchaean [10 and references therein; 1]. The Hout River Shear Zone forms the terrane boundary between the granite-greenstone terrane of the Kaapvaal craton in the south and the high-grade Southern Marginal Zone (SMZ) of the Limpopo Complex in the north. Integrated structural, metamorphic, magmatic and age data collected over a period of more than 30 years provide convincing evidence for a Neoarchean high-grade tectono-metamorphic event that affected the SMZ in the interval ~2.72 - 2.60 Ga [4; 5, 6; 7; 2; 8; 9; 11]. The thrust-controlled exhumation of the SMZ is demonstrated by the convergence of a retrograde P-T path in the hanging wall (SMZ) and a prograde P-T loop in the footwall (Kaapvaal Craton) of the steeply SW-verging Hout River Shear Zone [4; 5]. The coeval ages (~2.69 Ga) of the two contrasting metamorphic histories are indicated by geochronological data [2; 3]. In addition, the establishment of a retrograde isograd and zone of rehydrated granulites in the hanging wall by hydrous CO2-rich fluids derived by dehydration of the low-grade rocks in the footwall provides another convincing link between the two contrasting metamorphic environments [10]. Distinct retrograde P-T paths [4; 6; 8] linked to distinct shear deformational events document evidence for a two-stage post-peak exhumation history of the SMZ: (i) granulites sampled far from the contact with the cool rocks of the Kaapvaal Craton are characterized by P-T paths with two distinct decompression-cooling (DC) stages (DC=>DC paths), (ii) granulites sampled close to this contact are

  20. Archaean lode gold deposits: the solute source problem

    SciTech Connect

    Kerrich, R.

    1985-01-01

    On a regional scale lode gold deposits typically occur throughout the entire spectrum of greenstone belt stratigraphy. In the Abitibi Belt lode deposits are sited at the base of the volcanic cycle (Noranda), at the boundary of two volcanic cycles (Timmins) and in the stratigraphically highest groups at Kirkland Lake and Bousquet. The gold deposits are preferentially disposed along major structures apparently demarking rift zones, where extension was accommodated by listric normal faults that subsequently acted as thrusts during compression. These major structures were also sites of emplacement of trondhjemite magmas, lamprophyres and potassic basalts. From previous work Abitibi Belt volcanism spans 2725 to 2703 Ma, batholith emplacement 2675 to 2685 Ma (U-Pb on zircons), and the terminal Matachewan dyke swarm which transects all major structures is 2690 +/- 93 Ma. The lode deposits have age corrected /sup 87/Sr//sup 86/Sr initials of 0.7015 to 0.7025, as well as more radiogenic Pb and higher ..mu.. relative to contemporaneous mantle Sr and Pb isotope ratios. Tourmaline, scheelite, piemontite and apatites separated from 14 deposits all possess /sup 87/Sr//sup 86/Sr 0.7015 to 0.7025. These more radiogenic values contra-indicate a direct mantle source for Sr and Pb, but rather indicate that all mineralizing fluids carry contributions from a felsic crustal source having a significant production of Rb, U and Th radiogenic daughter nuclides as well as from komatiites and tholeiites. Gold, along with an array of lithophile elements including K, Rb, Pb, Li, Sr and CO/sub 2/ were distilled from this mixed source.

  1. A mid-Archaean ophiolite complex, Barberton Mountain land

    NASA Technical Reports Server (NTRS)

    Dewit, M. J.; Hart, R.; Hart, R.

    1986-01-01

    New field observations and structurally restored geologic sections through the southern part of 3.5-3.6 Ga Barberton greenstone belt show that its mafic to ultramafic rocks form a pseudostratigraphy comparable to that of Phanerozoic ophiolites; this ancient ophiolite is referred to as the Jamestown ophiolite complex. It consists of an intrusive-extrusive mafic-ultramafic section, underlain by a high-temperature tectono-metamorphic residual peridotitic base, and is capped by a chert-shale sequence which it locally intrudes. Geochemical data support an ophiolitic comparison. Fraction of high temperature melting PGE's 2500 C in the residual rocks suggest a lower mantle origin for the precursors of this crust. An oceanic rather than arc-related crustal section can be inferred from the absence of contemporaneous andesites. The entire simatic section has also been chemically altered during its formation by hyrothermal interaction with the Archean hydrosphere. The most primitive parent liquids, from which the extrusive sequence evolved, may have been picritic in character. Rocks with a komatiitic chemistry may have been derived during crystal accumulation from picrite-crystal mushes (predominantly olivine-clinopyroxene) and/or by metasomatism during one or more subsequent episodes of hydration-dehydration. The Jamestown ophiolite complex provides the oldest record with evidence for the formation of oceanic lithosphere at constructive tectonic boundaries.

  2. A mid-Archaean ophiolite complex, Barberton Mountain land

    NASA Astrophysics Data System (ADS)

    Dewit, M. J.; Hart, R.; Hart, R.

    New field observations and structurally restored geologic sections through the southern part of 3.5-3.6 Ga Barberton greenstone belt show that its mafic to ultramafic rocks form a pseudostratigraphy comparable to that of Phanerozoic ophiolites; this ancient ophiolite is referred to as the Jamestown ophiolite complex. It consists of an intrusive-extrusive mafic-ultramafic section, underlain by a high-temperature tectono-metamorphic residual peridotitic base, and is capped by a chert-shale sequence which it locally intrudes. Geochemical data support an ophiolitic comparison. Fraction of high temperature melting PGE's 2500 C in the residual rocks suggest a lower mantle origin for the precursors of this crust. An oceanic rather than arc-related crustal section can be inferred from the absence of contemporaneous andesites. The entire simatic section has also been chemically altered during its formation by hyrothermal interaction with the Archean hydrosphere. The most primitive parent liquids, from which the extrusive sequence evolved, may have been picritic in character. Rocks with a komatiitic chemistry may have been derived during crystal accumulation from picrite-crystal mushes (predominantly olivine-clinopyroxene) and/or by metasomatism during one or more subsequent episodes of hydration-dehydration. The Jamestown ophiolite complex provides the oldest record with evidence for the formation of oceanic lithosphere at constructive tectonic boundaries.

  3. What traces of life can we expect on Mars? Lessons from the early Earth

    NASA Astrophysics Data System (ADS)

    Westall, F.

    2008-09-01

    crytic but abundant evidence of past life [3] in the form of fossilised microbial colonies on the surfaces of detrital volcanic grains, in fine volcanic dust deposits, and in the pores of scoriaceous pumice, etc (Fig. 2). Again, these traces can be identified only through petrographic thin section and SEM study. The bulk organic carbon contents of these rocks is very low, ~0.01-0.05% and their C-isotope signature (~ - 25 ‰), although indicative of life, could also be produced through abiological processes [5]. Only the combination of multiple analytical techniques, of which high resolution microscopy is one of the most fundamental, permitted a biogenic origin to be attributed to these structures. Biolaminated sediments, including domal stromatolites, in Early Archaean terrains are the result of anaerobic photosynthetic activity [6-9]. Photosynthesis is a relatively evolved metabolism. Evidence of photosynthetic activity is preserved in the rhythmic laminations found in sediments deposited at the edges of shallow basins due to the growth of photosynthetic microbial mats on the sediment surfaces. These laminations, ranging from a few tens of microns to packets up to a couple of millimetres in thickness, are macroscopically and microscopically visible (Fig. 3). Given sufficient tectonic stability of the shallow water, carbonate platform environments in which they form, photosynthetic microorganisms on the early Earth formed domical stromatolites. In the case of biolaminated sediments, bulk organic carbon contents are again low (0.01 %) but the individual biolaminae have a higher carbon content (0.07%). Certain highly carbonaceous biomaminated cherts have carbon contents ranging up to 0.5% [10]. Photosynthetic organisms, however, are not only restricted to stable substrates and may also be planktonic, living free in the upper layers of water bodies. Evidence of planktonic microorganisms on the early Earth has been suggested by [10]. Whether floating in the ocean or forming

  4. Optimizing Early Retirement Decisions.

    DTIC Science & Technology

    2007-11-02

    the military. The U.S. Army’s early retirement program is a temporary one designed to allow some soldiers to leave the service prior to 20 years of...whether it makes financial sense for an officer to select early retirement . A spreadsheet formulation is developed and used to indicate if and when...an officer should select early retirement . The program investigates the decision that various civilian salary levels and various assumed discount rates.

  5. Early Childhood Education.

    ERIC Educational Resources Information Center

    Elkind, David

    In five sections, this paper explores dimensions of early childhood education: schooling generally construed as nonparental instruction in knowledge, values, and skills. Section 1 looks at some of the factors which have contributed to the rapid growth of early childhood education in modern times. Section 2 briefly highlights the contributions of…

  6. FRAME: the early days.

    PubMed

    Rowan, Andrew N

    2009-12-01

    The article reviews the early history of FRAME from the perspective of its first "Scientific Administrator". The roles of Mrs Hegarty the founder, and other early contributors to FRAME's development are described. In addition, the article discusses FRAME's strategic approach to the subject and how Mrs Hegarty's background influenced the development of that approach.

  7. Jamaica on Early Maps.

    ERIC Educational Resources Information Center

    Richason, Benjamin F., Jr.

    1983-01-01

    Columbus sighted Jamaica during his second voyage and was marooned there for more than a year during his fourth. The succession of early maps of Jamaica betrays its slow development and its unimportance to early colonizers. Modern tourism is the elusive "gold" which the Spanish fortune hunters did not find. (CS)

  8. Early College High Schools

    ERIC Educational Resources Information Center

    Dessoff, Alan

    2011-01-01

    For at-risk students who stand little chance of going to college, or even finishing high school, a growing number of districts have found a solution: Give them an early start in college while they still are in high school. The early college high school (ECHS) movement that began with funding from the Bill and Melinda Gates Foundation 10 years ago…

  9. Rethinking Early Childhood Education

    ERIC Educational Resources Information Center

    Pelo, Ann, Ed.

    2008-01-01

    "Rethinking Early Childhood Education" is alive with the conviction that teaching young children involves values and vision. This anthology collects inspiring stories about social justice teaching with young children. Included here is outstanding writing from childcare teachers, early-grade public school teachers, scholars, and parents.…

  10. Assessing Early Literacy.

    ERIC Educational Resources Information Center

    Hodges, Carol A.

    Criticisms leveled at readiness tests in general by a variety of early childhood groups and at reading tests in general by reading researchers certainly appear to be valid for traditional paper and pencil reading readiness tests. These reading readiness tests have not kept pace with advances in early literacy instructional techniques, such as…

  11. Early Retirement Payoff

    ERIC Educational Resources Information Center

    Fitzpatrick, Maria D.; Lovenheim, Michael F.

    2014-01-01

    As public budgets have grown tighter over the past decade, states and school districts have sought ways to control the growth of spending. One increasingly common strategy employed to rein in costs is to offer experienced teachers with high salaries financial incentives to retire early. Although early retirement incentive (ERI) programs have been…

  12. Problematising Early School Leaving

    ERIC Educational Resources Information Center

    Ross, Alistair; Leathwood, Carole

    2013-01-01

    Early school leaving has been identified as a key policy priority across Europe. In this article, we critically discuss the underpinning assumptions and rationale for this policy focus, challenging the association that is made between early school leaving, economic growth and employment. We suggest that ESL is important, not because it is…

  13. The early universe.

    NASA Astrophysics Data System (ADS)

    Kolb, E. W.; Turner, M. S.

    This monograph is a broad survey that provides an insightful look at cosmology and an up-to-date accounting of modern ideas in particle physics as they relate to cosmology, particularly to the early history of the universe. A companion volume "The early universe: reprints" is published in 1988 (see 46.003.074).

  14. Crustal Strain Patterns in Magmatic and Amagmatic Early Stage Rifts: Border Faults, Magma Intrusion, and Volatiles

    NASA Astrophysics Data System (ADS)

    Ebinger, C. J.; Keir, D.; Roecker, S. W.; Tiberi, C.; Aman, M.; Weinstein, A.; Lambert, C.; Drooff, C.; Oliva, S. J. C.; Peterson, K.; Bourke, J. R.; Rodzianko, A.; Gallacher, R. J.; Lavayssiere, A.; Shillington, D. J.; Khalfan, M.; Mulibo, G. D.; Ferdinand-Wambura, R.; Palardy, A.; Albaric, J.; Gautier, S.; Muirhead, J.; Lee, H.

    2015-12-01

    Rift initiation in thick, strong continental lithosphere challenges current models of continental lithospheric deformation, in part owing to gaps in our knowledge of strain patterns in the lower crust. New geophysical, geochemical, and structural data sets from youthful magmatic (Magadi-Natron, Kivu), weakly magmatic (Malawi, Manyara), and amagmatic (Tanganyika) sectors of the cratonic East African rift system provide new insights into the distribution of brittle strain, magma intrusion and storage, and time-averaged deformation. We compare and contrast time-space relations, seismogenic layer thickness variations, and fault kinematics using earthquakes recorded on local arrays and teleseisms in sectors of the Western and Eastern rifts, including the Natron-Manyara basins that developed in Archaean lithosphere. Lower crustal seismicity occurs in both the Western and Eastern rifts, including sectors on and off craton, and those with and without central rift volcanoes. In amagmatic sectors, lower crustal strain is accommodated by slip along relatively steep border faults, with oblique-slip faults linking opposing border faults that penetrate to different crustal levels. In magmatic sectors, seismicity spans surface to lower crust beneath both border faults and eruptive centers, with earthquake swarms around magma bodies. Our focal mechanisms and Global CMTs from a 2007 fault-dike episode show a local rotation from ~E-W extension to NE-SE extension in this linkage zone, consistent with time-averaged strain recorded in vent and eruptive chain alignments. These patterns suggest that strain localization via widespread magma intrusion can occur during the first 5 My of rifting in originally thick lithosphere. Lower crustal seismicity in magmatic sectors may be caused by high gas pressures and volatile migration from active metasomatism and magma degassing, consistent with high CO2 flux along fault zones, and widespread metasomatism of xenoliths. Volatile release and

  15. Earth's early biosphere.

    PubMed

    Des Marais, D J

    1998-05-01

    Understanding our own early biosphere is essential to our search for life elsewhere, because life arose on Earth very early and rocky planets shared similar early histories. The biosphere arose before 3.8 Ga ago, was exclusively unicellular and was dominated by hyperthermophiles that utilized chemical sources of energy and employed a range of metabolic pathways for CO2 assimilation. Photosynthesis also arose very early. Oxygenic photosynthesis arose later but still prior to 2.7 Ga. The transition toward the modern global environment was paced by a decline in volcanic and hydrothermal activity. These developments allowed atmospheric O2 levels to increase. The O2 increase created new niches for aerobic life, most notably the more advanced Eukarya that eventually spawned the megascopic fauna and flora of our modern biosphere.

  16. Early School Screening Practices

    ERIC Educational Resources Information Center

    Maitland, Suzanne; And Others

    1974-01-01

    To ascertain the prevalence of early school screening practices, the specific tests employed, and the use made of the test results, a survey was conducted of a representative sample of 980 school districts in the United States. (Author)

  17. Earth's early biosphere

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.

    1998-01-01

    Understanding our own early biosphere is essential to our search for life elsewhere, because life arose on Earth very early and rocky planets shared similar early histories. The biosphere arose before 3.8 Ga ago, was exclusively unicellular and was dominated by hyperthermophiles that utilized chemical sources of energy and employed a range of metabolic pathways for CO2 assimilation. Photosynthesis also arose very early. Oxygenic photosynthesis arose later but still prior to 2.7 Ga. The transition toward the modern global environment was paced by a decline in volcanic and hydrothermal activity. These developments allowed atmospheric O2 levels to increase. The O2 increase created new niches for aerobic life, most notably the more advanced Eukarya that eventually spawned the megascopic fauna and flora of our modern biosphere.

  18. Budgeting for Early Retirements.

    ERIC Educational Resources Information Center

    Johnson, Donald R.

    1999-01-01

    School business administrators are devoting a significant portion of their time to retirement-related issues. Describes the retirement systems in place in Illinois and provides some budgeting examples for retirements and early retirements of school district personnel. (MLF)

  19. Supporting Early Learning Act

    THOMAS, 113th Congress

    Rep. Himes, James A. [D-CT-4

    2014-02-03

    06/13/2014 Referred to the Subcommittee on Early Childhood, Elementary, and Secondary Education. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  20. Early Learning Innovation Act

    THOMAS, 111th Congress

    Rep. Himes, James A. [D-CT-4

    2009-10-29

    12/08/2009 Referred to the Subcommittee on Early Childhood, Elementary, and Secondary Education. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  1. Early Learning Alignment Act

    THOMAS, 111th Congress

    Rep. Altmire, Jason [D-PA-4

    2010-09-29

    11/18/2010 Referred to the Subcommittee on Early Childhood, Elementary, and Secondary Education. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  2. Biogeochemistry: Early phosphorus redigested

    NASA Astrophysics Data System (ADS)

    Poulton, Simon W.

    2017-02-01

    Atmospheric oxygen was maintained at low levels throughout huge swathes of Earth's early history. Estimates of phosphorus availability through time suggest that scavenging from anoxic, iron-rich oceans stabilized this low-oxygen world.

  3. Early Life Stages

    EPA Pesticide Factsheets

    Childhood should be viewed as a sequence of lifestages, from birth through infancy and adolescence. When assessing early life risks, consideration is given to risks resulting from fetal exposure via the pregnant mother, as well as postnatal exposures.

  4. Greenstone belt tectonics: Thermal constraints

    NASA Technical Reports Server (NTRS)

    Bickle, M. J.; Nisbet, E. G.

    1986-01-01

    Archaean rocks provide a record of the early stages of planetary evolution. The interpretation is frustrated by the probable unrepresentative nature of the preserved crust and by the well known ambiguities of tectonic geological synthesis. Broad constraints can be placed on the tectonic processes in the early Earth from global scale modeling of thermal and chemical evolution of the Earth and its hydrosphere and atmosphere. The Archean record is the main test of such models. Available general model constraints are outlined based on the global tectonic setting within which Archaean crust evolved and on the direct evidence the Archaean record provides, particularly the thermal state of the early Earth.

  5. Early Dementia Screening.

    PubMed

    Panegyres, Peter K; Berry, Renee; Burchell, Jennifer

    2016-01-21

    As the population of the world increases, there will be larger numbers of people with dementia and an emerging need for prompt diagnosis and treatment. Early dementia screening is the process by which a patient who might be in the prodromal phases of a dementing illness is determined as having, or not having, the hallmarks of a neurodegenerative condition. The concepts of mild cognitive impairment, or mild neurocognitive disorder, are useful in analyzing the patient in the prodromal phase of a dementing disease; however, the transformation to dementia may be as low as 10% per annum. The search for early dementia requires a comprehensive clinical evaluation, cognitive assessment, determination of functional status, corroborative history and imaging (including MRI, FDG-PET and maybe amyloid PET), cerebrospinal fluid (CSF) examination assaying Aβ1-42, T-τ and P-τ might also be helpful. Primary care physicians are fundamental in the screening process and are vital in initiating specialist investigation and treatment. Early dementia screening is especially important in an age where there is a search for disease modifying therapies, where there is mounting evidence that treatment, if given early, might influence the natural history-hence the need for cost-effective screening measures for early dementia.

  6. Early Dementia Screening

    PubMed Central

    Panegyres, Peter K.; Berry, Renee; Burchell, Jennifer

    2016-01-01

    As the population of the world increases, there will be larger numbers of people with dementia and an emerging need for prompt diagnosis and treatment. Early dementia screening is the process by which a patient who might be in the prodromal phases of a dementing illness is determined as having, or not having, the hallmarks of a neurodegenerative condition. The concepts of mild cognitive impairment, or mild neurocognitive disorder, are useful in analyzing the patient in the prodromal phase of a dementing disease; however, the transformation to dementia may be as low as 10% per annum. The search for early dementia requires a comprehensive clinical evaluation, cognitive assessment, determination of functional status, corroborative history and imaging (including MRI, FDG-PET and maybe amyloid PET), cerebrospinal fluid (CSF) examination assaying Aβ1–42, T-τ and P-τ might also be helpful. Primary care physicians are fundamental in the screening process and are vital in initiating specialist investigation and treatment. Early dementia screening is especially important in an age where there is a search for disease modifying therapies, where there is mounting evidence that treatment, if given early, might influence the natural history—hence the need for cost-effective screening measures for early dementia. PMID:26838803

  7. Early Intervention in Psychosis

    PubMed Central

    McGorry, Patrick D.

    2015-01-01

    Abstract Early intervention for potentially serious disorder is a fundamental feature of healthcare across the spectrum of physical illness. It has been a major factor in the reductions in morbidity and mortality that have been achieved in some of the non-communicable diseases, notably cancer and cardiovascular disease. Over the past two decades, an international collaborative effort has been mounted to build the evidence and the capacity for early intervention in the psychotic disorders, notably schizophrenia, where for so long deep pessimism had reigned. The origins and rapid development of early intervention in psychosis are described from a personal and Australian perspective. This uniquely evidence-informed, evidence-building and cost-effective reform provides a blueprint and launch pad to radically change the wider landscape of mental health care and dissolve many of the barriers that have constrained progress for so long. PMID:25919380

  8. Why Early Intervention Works

    PubMed Central

    Guralnick, Michael J.

    2011-01-01

    A systems perspective is put forward designed to place the many diverse conceptual and practice approaches and accomplishments in the early intervention field within a common framework. Complex reciprocal patterns of influence are described emphasizing risk and protective factors operating at 3 levels: child social and cognitive competence, family patterns of interaction, and family resources. It is argued that this framework can provide an understanding with respect to why early intervention works when it does as well as establish a new assessment and intervention approach firmly grounded in developmental science. PMID:21532932

  9. 75 FR 20830 - Early Learning

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-21

    ... auditorium at the Center for Early Education, 3245 E. Exposition Avenue, Denver, CO. Early Learning Topic... Early Learning AGENCY: Office of the Secretary, Department of Education. ACTION: Notice of public..., is seeking input from State agencies responsible for early learning and development,...

  10. Early Indian People.

    ERIC Educational Resources Information Center

    Doermann, Elisabeth

    1979-01-01

    Using bits and pieces of the past such as charred bits of wood from campfires, broken pieces of clay pots, stone spearpoints and arrowheads, and shell or copper ornaments, the archaeologist tries to put together the story of early Indian people in the Minnesota region. A short story, one of eight articles, re-creates the kill of an Itasca bison…

  11. Identifying Early School Leaving

    ERIC Educational Resources Information Center

    Poole, Millicent E.

    1978-01-01

    Using a matched sample of students who stay in school and those who drop out, or leave early, an attempt was made, via multiple discriminant analysis, to identify the significant characteristics which distinguish "drop outs" from their peers who remain at school. Results indicated that both types of students have similar value orientations and…

  12. Early Childhood: Psychomotor Skills.

    ERIC Educational Resources Information Center

    National Center on Educational Media and Materials for the Handicapped, Columbus, OH.

    Selected from the National Instructional Materials Information System (NIMIS)--a computer based on-line interactive retrieval system on special education materials--the bibliography covers 31 materials for teaching psychomotor skills at the early childhood level. Entries are presented in order of NIMIS accession number and include the following…

  13. Teachers in Early Christianity

    ERIC Educational Resources Information Center

    Markowski, Michael

    2008-01-01

    This article presents the idea that the Early Church supported teachers as one of the ministry offices within the local church. These teachers worked to mature the spiritual life of the congregation and so helped to free the pastoral ministry to focus on other duties, many of which fall on pastors. Most ministers, pastors, and others teach at one…

  14. Early Communicative Skills.

    ERIC Educational Resources Information Center

    MacKay, Gilbert F.; Dunn, William R.

    Intended for parents and teachers, the manual offers guidelines for developing communication skills in severely and profoundly mentally handicapped children. An introduction helps the reader determine a suitable starting point and provides a description of early communication skills; Part II describes the five stages in communication development.…

  15. Early Childhood Military Education?

    ERIC Educational Resources Information Center

    Pelo, Ann

    2011-01-01

    Does the country's national security rely on top-quality early childhood education? Yes, say the military leaders of Mission: Readiness, an organization led by retired military commanders that promotes investment in education, child health, and parenting support. Actually, the generals are right, but for all the wrong reasons. The generals' aim is…

  16. Early Developments, 1998.

    ERIC Educational Resources Information Center

    Little, Loyd, Ed.

    1998-01-01

    This document consists of the two 1998 issues of a journal reporting new research in early child development conducted by the Frank Porter Graham Child Development Center at the University of North Carolina at Chapel Hill. In the Spring 1998 issue, articles highlight the Center's diverse cross-cultural projects and global research, training and…

  17. Early Childhood Kits.

    ERIC Educational Resources Information Center

    National Center on Educational Media and Materials for the Handicapped, Columbus, OH.

    Selected from the National Instructional Materials Information System (NIMIS)--a computer based on-line interactive retrieval system on special education materials, the bibliography covers 80 kits for developing skills at the early childhood level. Entries are presented in order of NIMIS accession number and include the following information:…

  18. Early Grades Ideas.

    ERIC Educational Resources Information Center

    Classroom Computer Learning, 1985

    1985-01-01

    Presents a collection of computer-oriented teaching activities for the early grades. They include creating musical tones using Atari PILOT, a simulation of traffic lights, teacher-friendly password protection, drawing the alphabet using Logo, and using the Commodore 64's special character graphics. (JN)

  19. Preventing Early Learning Failure.

    ERIC Educational Resources Information Center

    Sornson, Bob, Ed.

    Noting that thousands of young children with the capacity to experience school success do not because they are unprepared for school learning activities, have experienced physical or emotional setbacks that cause them to be at risk for early learning failure, have never experienced limits on their behavior, or have mild sensory or motor deficits,…

  20. Early stage colon cancer.

    PubMed

    Freeman, Hugh James

    2013-12-14

    Evidence has now accumulated that colonoscopy and removal of polyps, especially during screening and surveillance programs, is effective in overall risk reduction for colon cancer. After resection of malignant pedunculated colon polyps or early stage colon cancers, long-term repeated surveillance programs can also lead to detection and removal of asymptomatic high risk advanced adenomas and new early stage metachronous cancers. Early stage colon cancer can be defined as disease that appears to have been completely resected with no subsequent evidence of involvement of adjacent organs, lymph nodes or distant sites. This differs from the clinical setting of an apparent "curative" resection later pathologically upstaged following detection of malignant cells extending into adjacent organs, peritoneum, lymph nodes or other distant sites, including liver. This highly selected early stage colon cancer group remains at high risk for subsequent colon polyps and metachronous colon cancer. Precise staging is important, not only for assessing the need for adjuvant chemotherapy, but also for patient selection for continued surveillance. With advanced stages of colon cancer and a more guarded outlook, repeated surveillance should be limited. In future, novel imaging technologies (e.g., confocal endomicroscopy), coupled with increased pathological recognition of high risk markers for lymph node involvement (e.g., "tumor budding") should lead to improved staging and clinical care.

  1. Early Grades Ideas.

    ERIC Educational Resources Information Center

    Classroom Computer Learning, 1984

    1984-01-01

    Presents computer-oriented teaching suggestions suitable for early grades. They include creating houses and stained glass ornaments using Logo, recording class activities with a database management program, making mazes with graphics programs, making drawings with a KoalaPad, and using a program to introduce computers to non-English speaking…

  2. Creativity: The Early Years

    ERIC Educational Resources Information Center

    Shade, Rick; Shade, Patti Garrett

    2016-01-01

    There is a myth that some people are creative and others are not. However, all children are born creative. They love to explore, ask questions, and are incredibly imaginative. Parents are key in nurturing their child's creativity in the early years. This article offers resources and strategies parents can use at different ages and stages (newborn,…

  3. Early Childhood Trauma

    ERIC Educational Resources Information Center

    National Child Traumatic Stress Network, 2010

    2010-01-01

    Early childhood trauma generally refers to the traumatic experiences that occur to children aged 0-6. Because infants' and young children's reactions may be different from older children's, and because they may not be able to verbalize their reactions to threatening or dangerous events, many people assume that young age protects children from the…

  4. Early Childhood Education.

    ERIC Educational Resources Information Center

    Advocate, 1995

    1995-01-01

    This special theme issue of the journal "The Advocate," offers articles on early interventions for preschoolers with special needs, including three articles in Spanish. Contents include: "Providing An Orientation for Life" (Galen D. Kirkland); "AFC Fights Cuts in Education at 'Speak Out' Rally" (Nadine Renazile);…

  5. Early Education Workshop

    ERIC Educational Resources Information Center

    Hallum, Rosemary; Newhart, Edith Hom

    1978-01-01

    Early childhood classes traditionally have used a "multi-" approach to education that is based on young children's growth and development. Offers a variety of multisensory and multimedia activities in many curriculum areas that can be useful in the busy end-of-school weeks. (Author/RK)

  6. Music in Early Childhood.

    ERIC Educational Resources Information Center

    Feierabend, John

    1990-01-01

    Argues that music activities in early childhood education foster a variety of developmental skills. Analyzes Howard Gardner's theory of multiple intelligences, contending that music intelligence is a separate intelligence. Provides ways to identify and promote musical intelligence. Suggests methods for encouraging musical development. Using songs…

  7. Documenting Early Science Learning.

    ERIC Educational Resources Information Center

    Jones, Jacqueline; Courtney, Rosalea

    2002-01-01

    Three principles that guide documentation and assessment of children's early science understanding are: collect a variety of forms of evidence, collect evidence over a period of time, and collect evidence on the understanding of groups of children as well as individuals. Information and insights gained from this process help teachers plan future…

  8. Early hominin auditory capacities

    PubMed Central

    Quam, Rolf; Martínez, Ignacio; Rosa, Manuel; Bonmatí, Alejandro; Lorenzo, Carlos; de Ruiter, Darryl J.; Moggi-Cecchi, Jacopo; Conde Valverde, Mercedes; Jarabo, Pilar; Menter, Colin G.; Thackeray, J. Francis; Arsuaga, Juan Luis

    2015-01-01

    Studies of sensory capacities in past life forms have offered new insights into their adaptations and lifeways. Audition is particularly amenable to study in fossils because it is strongly related to physical properties that can be approached through their skeletal structures. We have studied the anatomy of the outer and middle ear in the early hominin taxa Australopithecus africanus and Paranthropus robustus and estimated their auditory capacities. Compared with chimpanzees, the early hominin taxa are derived toward modern humans in their slightly shorter and wider external auditory canal, smaller tympanic membrane, and lower malleus/incus lever ratio, but they remain primitive in the small size of their stapes footplate. Compared with chimpanzees, both early hominin taxa show a heightened sensitivity to frequencies between 1.5 and 3.5 kHz and an occupied band of maximum sensitivity that is shifted toward slightly higher frequencies. The results have implications for sensory ecology and communication, and suggest that the early hominin auditory pattern may have facilitated an increased emphasis on short-range vocal communication in open habitats. PMID:26601261

  9. Early hominin auditory capacities.

    PubMed

    Quam, Rolf; Martínez, Ignacio; Rosa, Manuel; Bonmatí, Alejandro; Lorenzo, Carlos; de Ruiter, Darryl J; Moggi-Cecchi, Jacopo; Conde Valverde, Mercedes; Jarabo, Pilar; Menter, Colin G; Thackeray, J Francis; Arsuaga, Juan Luis

    2015-09-01

    Studies of sensory capacities in past life forms have offered new insights into their adaptations and lifeways. Audition is particularly amenable to study in fossils because it is strongly related to physical properties that can be approached through their skeletal structures. We have studied the anatomy of the outer and middle ear in the early hominin taxa Australopithecus africanus and Paranthropus robustus and estimated their auditory capacities. Compared with chimpanzees, the early hominin taxa are derived toward modern humans in their slightly shorter and wider external auditory canal, smaller tympanic membrane, and lower malleus/incus lever ratio, but they remain primitive in the small size of their stapes footplate. Compared with chimpanzees, both early hominin taxa show a heightened sensitivity to frequencies between 1.5 and 3.5 kHz and an occupied band of maximum sensitivity that is shifted toward slightly higher frequencies. The results have implications for sensory ecology and communication, and suggest that the early hominin auditory pattern may have facilitated an increased emphasis on short-range vocal communication in open habitats.

  10. Isolation in Early Childhood.

    ERIC Educational Resources Information Center

    Rogers, Sinclair

    This paper presents information on isolated children and describes a study being undertaken to examine the role of isolation in reported cases of child abuse and neglect. The effects of extreme isolation on language and psychological development are emphasized. The importance of early socialization is seen in relation to normal development.…

  11. Early malignant syphilis*

    PubMed Central

    Ortigosa, Yara Martins; Bendazzoli, Paulo Salomão; Barbosa, Angela Marques; Ortigosa, Luciena Cegatto Martins

    2016-01-01

    Early malignant syphilis is a rare and severe variant of secondary syphilis. It is clinically characterized by lesions, which can suppurate and be accompanied by systemic symptoms such as high fever, asthenia, myalgia, and torpor state. We report a diabetic patient with characteristic features of the disease showing favorable evolution of the lesions after appropriate treatment. PMID:28300925

  12. Early Adolescent Ego Development.

    ERIC Educational Resources Information Center

    James, Michael A.

    1980-01-01

    Presented are the theoretical characteristics of social identity in early adolescence (ages 10 to 15). It is suggested that no longer is identity thought to begin with adolescence, but may have its beginnings in the preteen years. The article draws heavily on Eriksonian concepts. (Editor/KC)

  13. Early Humour Production

    ERIC Educational Resources Information Center

    Hoicka, Elena; Akhtar, Nameera

    2012-01-01

    The current studies explored early humour as a complex socio-cognitive phenomenon by examining 2- and 3-year-olds' humour production with their parents. We examined whether children produced novel humour, whether they cued their humour, and the types of humour produced. Forty-seven parents were interviewed, and videotaped joking with their…

  14. Early Developments, 2002.

    ERIC Educational Resources Information Center

    Winton, Pam, Ed.; Buysse, Virginia, Ed.

    2002-01-01

    This document consists of the three 2002 issues of a journal reporting new research in early child development conducted by the Frank Porter Graham Child Development Center (FPG) at the University of North Carolina at Chapel Hill. Articles in the Winter 2002 issue highlight some current work at FPG on factors that enhance or inhibit social and…

  15. Early Developments, 2000.

    ERIC Educational Resources Information Center

    Little, Loyd, Ed.

    2000-01-01

    This document consists of the three 2000 issues of a journal reporting new research in early child development conducted by the Frank Porter Graham Child Development Center at the University of North Carolina at Chapel Hill. Articles in the spring 2000 issue focus on a follow-up study of the Abecedarian Project, children of depressed mothers,…

  16. Tectonic evolution of the Gaoua region, Burkina Faso: Implications for mineralization

    NASA Astrophysics Data System (ADS)

    Baratoux, L.; Metelka, V.; Naba, S.; Ouiya, P.; Siebenaller, L.; Jessell, M. W.; Naré, A.; Salvi, S.; Béziat, D.; Franceschi, G.

    2015-12-01

    The interpretation of high-resolution airborne geophysical data integrated with field structural and lithological observations were employed in the creation of a litho-structural framework for the Gaoua region, Burkina Faso. The granite-greenstone domain of Paleoproterozoic age was affected by multiple deformation and mineralization events. The early tectonic phase is characterized by the emplacement of voluminous tholeiitic and calc-alkaline lavas, probably in a volcanic arc setting. The copper mineralization in Gongondy, Dienemera and Mt Biri is concentrated in a diorite/andesite breccia, and is interpreted as porphyry-copper style formed at an early stage of the evolution of the area. Evidence for the first deformation event D1Ga corresponding to N-S shortening was only found in the E-W trending mafic unit bordering the Gaoua batholith to the south. A second deformation phase D2Ga occurred under greenschist facies conditions and lead to a development of more or less penetrative metamorphic foliation and its subsequent folding under overall E-W compression. At later stages, the D2Ga switched to a transcurrent regime characterized by intense N-S to NW-trending steeply dipping shear zones. The first significant gold mineralization event is related to this transcurrent tectonic phase. During subsequent D3Ga, intense network of brittle to brittle-ductile NW and NE faults developed. Economic gold concentrations are attributed to the D3Ga event and are associated with the remobilization of early disseminated low grade gold concentrations. Significant deposits in the area are Nassara, Gomblora, Batié West and Kampti. The last deformation event D4Ga resulted in E-W trending thrust faults and crenulation cleavage planes, under overall N-S compression. No mineralization events related to this stage have been seen.

  17. Samuel Goudsmit - Early Influences

    NASA Astrophysics Data System (ADS)

    Goudsmit, Esther

    2010-03-01

    Samuel Goudsmit, born in 1902 in The Hague, Netherlands, earned his Ph.D. at the University of Leiden in 1926 with Paul Ehrenfest. The present talk will describe some aspects of his background and early formative years in order to provide context for the broad range of his professional life. Sam belonged to a large tribe of paternal and maternal uncles, aunts and first cousins; including his parents, grandparents and sister Ro, they numbered forty. Sam was the first of the tribe to be educated beyond high school. Early interests as a child and later as a university student in the Netherlands prefigured his significant and diverse contributions in several realms including not only physics but also teaching, Egyptology and scientific Intelligence. Bibliographic sources will include: The American Institute of Physics' Oral History Transcripts and photographs from the Emilio Segre visual archives, memoirs and conversations of those who knew Sam and also letters to his daughter, Esther.

  18. Early intervention in schizophrenia.

    PubMed

    Kulhara, Parmanand; Banerjee, Anindya; Dutt, Alakananda

    2008-04-01

    Early intervention (EI) programs in schizophrenia and other psychoses are aimed at early detection (ED) of the disease; prevent conversion to manifested psychosis and phase-specific treatment to reduce development of chronic disabilities. EI strategies include targeting people at "high risk" for developing schizophrenia, intervening in prodromal phase of schizophrenia, and reducing the "duration of untreated psychosis" (DUP). Services are delivered by a specialized team and are usually resource intensive. Several strategies like treatment with antipsychotics, family interventions, and cognitive behavior therapy have been tried with modest success in prodromal patients. Significant ethical reservations exist regarding exposing prodromal patients to the stigma of labeling as "high risk for schizophrenia" and side effects of psychotropics in the absence of clear evidence of efficacy in favor of ED, intervention by specialist teams, and phase-specific interventions in prodrome of psychosis. More research is warranted to demonstrate the risk-benefit and cost-benefit of such interventions before these can be routinely recommended.

  19. Early determinants of obesity.

    PubMed

    Ong, Ken K

    2010-01-01

    High rates of overweight and obesity even in very young children argue the case for strategies to prevent overweight from very young ages. Historical studies, prospective birth cohorts, and more recently genetic studies all indicate that the rapid weight gain trajectory to later obesity starts in the first months of life, even from birth. Early puberty and age at menarche are consequences of rapid infant weight gain and childhood overweight, and in turn these adolescent traits are predictive for obesity, diabetes, hypertension and cardiovascular disease events in later life. Understanding of the nutritional, parental and wider determinants of rapid infant weight gain are informing the development of obesity prevention strategies starting in early life. Such strategies could be further refined by future studies that address the specific regulation of infant adiposity, and also by studies that explore whether these life-course trajectories are modifiable during adolescence.

  20. Early bioenergetic evolution

    PubMed Central

    Sousa, Filipa L.; Thiergart, Thorsten; Landan, Giddy; Nelson-Sathi, Shijulal; Pereira, Inês A. C.; Allen, John F.; Lane, Nick; Martin, William F.

    2013-01-01

    Life is the harnessing of chemical energy in such a way that the energy-harnessing device makes a copy of itself. This paper outlines an energetically feasible path from a particular inorganic setting for the origin of life to the first free-living cells. The sources of energy available to early organic synthesis, early evolving systems and early cells stand in the foreground, as do the possible mechanisms of their conversion into harnessable chemical energy for synthetic reactions. With regard to the possible temporal sequence of events, we focus on: (i) alkaline hydrothermal vents as the far-from-equilibrium setting, (ii) the Wood–Ljungdahl (acetyl-CoA) pathway as the route that could have underpinned carbon assimilation for these processes, (iii) biochemical divergence, within the naturally formed inorganic compartments at a hydrothermal mound, of geochemically confined replicating entities with a complexity below that of free-living prokaryotes, and (iv) acetogenesis and methanogenesis as the ancestral forms of carbon and energy metabolism in the first free-living ancestors of the eubacteria and archaebacteria, respectively. In terms of the main evolutionary transitions in early bioenergetic evolution, we focus on: (i) thioester-dependent substrate-level phosphorylations, (ii) harnessing of naturally existing proton gradients at the vent–ocean interface via the ATP synthase, (iii) harnessing of Na+ gradients generated by H+/Na+ antiporters, (iv) flavin-based bifurcation-dependent gradient generation, and finally (v) quinone-based (and Q-cycle-dependent) proton gradient generation. Of those five transitions, the first four are posited to have taken place at the vent. Ultimately, all of these bioenergetic processes depend, even today, upon CO2 reduction with low-potential ferredoxin (Fd), generated either chemosynthetically or photosynthetically, suggesting a reaction of the type ‘reduced iron → reduced carbon’ at the beginning of bioenergetic evolution

  1. Hands of early primates.

    PubMed

    Boyer, Doug M; Yapuncich, Gabriel S; Chester, Stephen G B; Bloch, Jonathan I; Godinot, Marc

    2013-12-01

    Questions surrounding the origin and early evolution of primates continue to be the subject of debate. Though anatomy of the skull and inferred dietary shifts are often the focus, detailed studies of postcrania and inferred locomotor capabilities can also provide crucial data that advance understanding of transitions in early primate evolution. In particular, the hand skeleton includes characteristics thought to reflect foraging, locomotion, and posture. Here we review what is known about the early evolution of primate hands from a comparative perspective that incorporates data from the fossil record. Additionally, we provide new comparative data and documentation of skeletal morphology for Paleogene plesiadapiforms, notharctines, cercamoniines, adapines, and omomyiforms. Finally, we discuss implications of these data for understanding locomotor transitions during the origin and early evolutionary history of primates. Known plesiadapiform species cannot be differentiated from extant primates based on either intrinsic hand proportions or hand-to-body size proportions. Nonetheless, the presence of claws and a different metacarpophalangeal [corrected] joint form in plesiadapiforms indicate different grasping mechanics. Notharctines and cercamoniines have intrinsic hand proportions with extremely elongated proximal phalanges and digit rays relative to metacarpals, resembling tarsiers and galagos. But their hand-to-body size proportions are typical of many extant primates (unlike those of tarsiers, and possibly Teilhardina, which have extremely large hands). Non-adapine adapiforms and omomyids exhibit additional carpal features suggesting more limited dorsiflexion, greater ulnar deviation, and a more habitually divergent pollex than observed plesiadapiforms. Together, features differentiating adapiforms and omomyiforms from plesiadapiforms indicate increased reliance on vertical prehensile-clinging and grasp-leaping, possibly in combination with predatory behaviors in

  2. Early Treatment in Shock

    DTIC Science & Technology

    2008-06-01

    dipeptide , and arginine have shown efficacy. (3,4) Studies with crocetin have also shown efficacy (5), but this agent is not available in a form which...in humans, while alanine-glutamine dipeptide is not approved in the United States. Crocetin is still in early Phase I studies, and will be...4. Alanine-glutamine dipeptide (AGD) studies are presented here. It should be noted that AGD is used widely in the clinical situation (in Europe

  3. Guideline for Early Interventions

    DTIC Science & Technology

    2006-04-01

    desensitization and reprocessing ( EMDR ) as a early mental health intervention, following mass violence and disasters, is a treatment of choice over other...village. Military operations take place under the eye of the world and are surrounded by high political attention. International missions far exceed...consistently reduce risks of later post-traumatic stress disorder or related adjustment difficulties. • There is no evidence that eye movement

  4. Early Training Estimation System

    DTIC Science & Technology

    1980-08-01

    are needed. First, by developing earlier and more accurate estimates of training requirements, the training planning process can begin earlier, and...this period and these questions require training input data and (2) the early training planning process requires a solid foundation on which to...development of initial design, task, skill, and training estimates? provision of input into training planning and acquisition documents: 2-39 provision

  5. Early anaerobic metabolisms

    PubMed Central

    Canfield, Don E; Rosing, Minik T; Bjerrum, Christian

    2006-01-01

    Before the advent of oxygenic photosynthesis, the biosphere was driven by anaerobic metabolisms. We catalogue and quantify the source strengths of the most probable electron donors and electron acceptors that would have been available to fuel early-Earth ecosystems. The most active ecosystems were probably driven by the cycling of H2 and Fe2+ through primary production conducted by anoxygenic phototrophs. Interesting and dynamic ecosystems would have also been driven by the microbial cycling of sulphur and nitrogen species, but their activity levels were probably not so great. Despite the diversity of potential early ecosystems, rates of primary production in the early-Earth anaerobic biosphere were probably well below those rates observed in the marine environment. We shift our attention to the Earth environment at 3.8 Gyr ago, where the earliest marine sediments are preserved. We calculate, consistent with the carbon isotope record and other considerations of the carbon cycle, that marine rates of primary production at this time were probably an order of magnitude (or more) less than today. We conclude that the flux of reduced species to the Earth surface at this time may have been sufficient to drive anaerobic ecosystems of sufficient activity to be consistent with the carbon isotope record. Conversely, an ecosystem based on oxygenic photosynthesis was also possible with complete removal of the oxygen by reaction with reduced species from the mantle. PMID:17008221

  6. Early intervention for psychosis

    PubMed Central

    Marshall, Max; Rathbone, John

    2014-01-01

    Background Proponents of early intervention have argued that outcomes might be improved if more therapeutic efforts were focused on the early stages of schizophrenia or on people with prodromal symptoms. Early intervention in schizophrenia has two elements that are distinct from standard care: early detection, and phase-specific treatment (phase-specific treatment is a psychological, social or physical treatment developed, or modified, specifically for use with people at an early stage of the illness). Early detection and phase-specific treatment may both be offered as supplements to standard care, or may be provided through a specialised early intervention team. Early intervention is now well established as a therapeutic approach in America, Europe and Australasia. Objectives To evaluate the effects of: (a) early detection; (b) phase-specific treatments; and (c) specialised early intervention teams in the treatment of people with prodromal symptoms or first-episode psychosis. Search methods We searched the Cochrane Schizophrenia Group Trials Register (March 2009), inspected reference lists of all identified trials and reviews and contacted experts in the field. Selection criteria We included all randomised controlled trials (RCTs) designed to prevent progression to psychosis in people showing prodromal symptoms, or to improve outcome for people with first-episode psychosis. Eligible interventions, alone and in combination, included: early detection, phase-specific treatments, and care from specialised early intervention teams. We accepted cluster-randomised trials but excluded non-randomised trials. Data collection and analysis We reliably selected studies, quality rated them and extracted data. For dichotomous data, we estimated relative risks (RR), with the 95% confidence intervals (CI). Where possible, we calculated the number needed to treat/harm statistic (NNT/H) and used intention-to-treat analysis (ITT). Main results Studies were diverse, mostly small

  7. Early Intervention/Early Childhood Special Education: Recommended Practices.

    ERIC Educational Resources Information Center

    Odom, Samuel L.; McLean, Mary E.

    This book's 15 chapters elaborate on specific educational practices in early intervention and early childhood special education, recommended by a task force of the Council for Exceptional Children's Division of Early Childhood. The selected practices were identified through a process involving analysis of expert opinions, professional consensus,…

  8. Research Priorities for Early Intervention and Early Childhood Special Education

    ERIC Educational Resources Information Center

    Division for Early Childhood, Council for Exceptional Children, 2006

    2006-01-01

    It is now widely accepted that investments in comprehensive and coordinated early intervention services will generate long-term benefits for children and families. Additional research is needed to continue to improve all aspects of service delivery in early intervention and early childhood special education, with a particular focus on conditions…

  9. Expressive Education in Early Childhood.

    ERIC Educational Resources Information Center

    Mori, Kimie

    1996-01-01

    Presents a concise overview of early childhood music education in Japan. Japanese early childhood education stresses the natural development of childhood, as well as cultivation of expressive activities. Discusses teaching methods, creative activities, and educational guidelines (MJP)

  10. Early Life Exposures and Cancer

    Cancer.gov

    Early-life events and exposures have important consequences for cancer development later in life, however, epidemiological studies of early-life factors and cancer development later in life have had significant methodological challenges.

  11. Early lunar magnetism.

    PubMed

    Garrick-Bethell, Ian; Weiss, Benjamin P; Shuster, David L; Buz, Jennifer

    2009-01-16

    It is uncertain whether the Moon ever formed a metallic core or generated a core dynamo. The lunar crust and returned samples are magnetized, but the source of this magnetization could be meteoroid impacts rather than a dynamo. Here, we report magnetic measurements and 40Ar/39Ar thermochronological calculations for the oldest known unshocked lunar rock, troctolite 76535. These data imply that there was a long-lived field on the Moon of at least 1 microtesla approximately 4.2 billion years ago. The early age, substantial intensity, and long lifetime of this field support the hypothesis of an ancient lunar core dynamo.

  12. Early modern mathematical instruments.

    PubMed

    Bennett, Jim

    2011-12-01

    In considering the appropriate use of the terms "science" and "scientific instrument," tracing the history of "mathematical instruments" in the early modern period is offered as an illuminating alternative to the historian's natural instinct to follow the guiding lights of originality and innovation, even if the trail transgresses contemporary boundaries. The mathematical instrument was a well-defined category, shared across the academic, artisanal, and commercial aspects of instrumentation, and its narrative from the sixteenth to the eighteenth century was largely independent from other classes of device, in a period when a "scientific" instrument was unheard of.

  13. Crowdsourced earthquake early warning.

    PubMed

    Minson, Sarah E; Brooks, Benjamin A; Glennie, Craig L; Murray, Jessica R; Langbein, John O; Owen, Susan E; Heaton, Thomas H; Iannucci, Robert A; Hauser, Darren L

    2015-04-01

    Earthquake early warning (EEW) can reduce harm to people and infrastructure from earthquakes and tsunamis, but it has not been implemented in most high earthquake-risk regions because of prohibitive cost. Common consumer devices such as smartphones contain low-cost versions of the sensors used in EEW. Although less accurate than scientific-grade instruments, these sensors are globally ubiquitous. Through controlled tests of consumer devices, simulation of an M w (moment magnitude) 7 earthquake on California's Hayward fault, and real data from the M w 9 Tohoku-oki earthquake, we demonstrate that EEW could be achieved via crowdsourcing.

  14. Crowdsourced earthquake early warning

    PubMed Central

    Minson, Sarah E.; Brooks, Benjamin A.; Glennie, Craig L.; Murray, Jessica R.; Langbein, John O.; Owen, Susan E.; Heaton, Thomas H.; Iannucci, Robert A.; Hauser, Darren L.

    2015-01-01

    Earthquake early warning (EEW) can reduce harm to people and infrastructure from earthquakes and tsunamis, but it has not been implemented in most high earthquake-risk regions because of prohibitive cost. Common consumer devices such as smartphones contain low-cost versions of the sensors used in EEW. Although less accurate than scientific-grade instruments, these sensors are globally ubiquitous. Through controlled tests of consumer devices, simulation of an Mw (moment magnitude) 7 earthquake on California’s Hayward fault, and real data from the Mw 9 Tohoku-oki earthquake, we demonstrate that EEW could be achieved via crowdsourcing. PMID:26601167

  15. Early Childhood Update, Fall 1995.

    ERIC Educational Resources Information Center

    Kimmerly, Lynn, Ed.

    1995-01-01

    This newsletter provides a periodic update on the activities of the Early Childhood Research Working Group (ECRWG), organized in early 1995 by the U.S. Department of Education and other federal government departments and agencies to promote interagency cooperation and public-private partnerships in early childhood research. This edition contains…

  16. Value-Added Early Learning

    ERIC Educational Resources Information Center

    Dichter, Harriet

    2011-01-01

    Elected state leaders often prioritize economic prosperity and competitiveness, which provides an important opportunity too rarely taken for investing in early education. In 2003, Pennsylvania recognized the connection between early education and the economy, and smartly embraced early learning as part of its economic prosperity and…

  17. Early Childhood Workforce Index, 2016

    ERIC Educational Resources Information Center

    Whitebook, Marcy; McLean, Caitlin; Austin, Lea J. E.

    2016-01-01

    The State of the Early Childhood Workforce (SECW) Initiative is a groundbreaking multi-year project to shine a steady spotlight on the nation's early childhood workforce. The SECW Initiative is designed to challenge entrenched ideas and policies that maintain an inequitable and inadequate status quo for early educators and for the children and…

  18. The Effectiveness of Early Intervention.

    ERIC Educational Resources Information Center

    Guralnick, Michael J., Ed.

    This book reviews research on the effectiveness of early intervention for children with disabilities or who are at risk. Program factors for children at risk and with disabilities, the effects of early intervention on different types of disabilities, and the outcomes of early intervention are explored. Chapters include: "Second-Generation Research…

  19. Ethnographic Knowledge for Early Childhood

    ERIC Educational Resources Information Center

    Adair, Jennifer Keys

    2010-01-01

    The policy brief "Ethnographic Knowledge for Early Childhood" details the contributions of current ethnographic research in the area of early childhood education. The brief's main purpose is to demonstrate how ethnography (as a methodology) helps us better understand the context of early childhood programs, the types of settings and…

  20. Early Childhood Special Music Education

    ERIC Educational Resources Information Center

    Darrow, Alice-Ann

    2011-01-01

    The process of early intervention is a critical component of Early Childhood Special Music Education. Early intervention is the process of providing services, education, and support to young children who have disabilities or to children who are at-risk of developing needs that may affect their physical, cognitive, or emotional development. The…

  1. Early Attrition among Suicidal Clients

    ERIC Educational Resources Information Center

    Surgenor, P. W. G.; Meehan, V.; Moore, A.

    2016-01-01

    The study aimed to identify the level of suicidal ideation in early attrition clients and their reasons for the early termination of their therapy. The cross-sectional design involved early attrition clients (C[subscript A]) who withdrew from therapy before their second session (n = 61), and continuing clients who (C[subscript C]) progressed…

  2. Early intervention in schizophrenia

    PubMed Central

    Kulhara, Parmanand; Banerjee, Anindya; Dutt, Alakananda

    2008-01-01

    Early intervention (EI) programs in schizophrenia and other psychoses are aimed at early detection (ED) of the disease; prevent conversion to manifested psychosis and phase-specific treatment to reduce development of chronic disabilities. EI strategies include targeting people at “high risk" for developing schizophrenia, intervening in prodromal phase of schizophrenia, and reducing the “duration of untreated psychosis" (DUP). Services are delivered by a specialized team and are usually resource intensive. Several strategies like treatment with antipsychotics, family interventions, and cognitive behavior therapy have been tried with modest success in prodromal patients. Significant ethical reservations exist regarding exposing prodromal patients to the stigma of labeling as “high risk for schizophrenia" and side effects of psychotropics in the absence of clear evidence of efficacy in favor of ED, intervention by specialist teams, and phase-specific interventions in prodrome of psychosis. More research is warranted to demonstrate the risk-benefit and cost-benefit of such interventions before these can be routinely recommended. PMID:19742227

  3. [Early onset diabetes mellitus].

    PubMed

    Busiah, K; Vaivre-Douret, L; Yachi, C; Cavé, H; Polak, M

    2013-12-01

    Neonatal diabetes mellitus is a rare condition (1/90,000 to 1/260,000 live births) defined as mild-to-severe hyperglycemia within the first year of life. Permanent neonatal diabetes mellitus requires lifelong therapy, whereas transient form resolves early in life but may relapse later on. Two main physiopathological mechanisms may explain this disease: β cell functional impairment or absence (pancreas agenesis or β cells destruction). The main genetic causes of β cells impairment are 6q24 abnormalities and mutations in ABCC8 or KCNJ11 potassium channel (KATP channel) genes. Compared to the KATP subtype, the 6q24 subtype had specific features: developmental defects involving the heart, kidneys, or urinary tract, intrauterine growth restriction, and early diagnosis. Remission of neonatal diabetes mellitus occurred in 51% of probands at a median age of 17 weeks. Recurrence was common at pubertal age, with no difference between the 6q24 and KATP-channel groups (82% vs 86%, p=0.36, respectively). Patients with mutations in ABCC8 or KCNJ11 genes had developmental delay with or without epilepsy but also developmental coordination disorder (particularly visual-spatial dyspraxia) or attention deficits in all of those who underwent in-depth neuropsychomotor investigations.

  4. Early management of osteoarthritis.

    PubMed

    Altman, Roy Davis

    2010-03-01

    Osteoarthritis (OA) is highly prevalent and increasing in frequency; the number of patients with OA has increased by nearly 30% over the past 10 years. The primary symptom of OA is pain. Pain and other symptoms of OA may have a profound effect on quality of life (QOL), affecting both physical function and psychological parameters. The economic costs of OA are high, and include those related to treatment, those for individuals and their families who must adapt their lives and homes to the disease, and those due to lost work productivity. These considerable humanistic and economic burdens of OA provide motivation for early identification and treatment. Early diagnosis is assisted by knowledge of risk factors. Classification criteria for OA of the hand, hip, and knee developed by the American College of Rheumatology assist in diagnosis. The European League Against Rheumatism has developed an elaborate system for diagnosis of OA of the hand. Several societies have developed therapeutic guidelines, with general overall agreement between publications. Therapy of OA is multimodal and requires a combination of pharmacologic and nonpharmacologic treatments.

  5. [In-patient (early) rehabilitation].

    PubMed

    Wallesch, Claus-W; Lautenschläger, Sindy

    2017-04-01

    It is difficult to develop the financing and hospital provision of interventions for early rehabilitation within the diagnosis-related group (DRG) system. In addition to a range of partially rehabilitative complex interventions, the system recognizes three main forms of early rehabilitative interventions: geriatric, neurological/neurosurgical, and interdisciplinary and others. In this article, the appropriate definitions and cost-effectiveness of these procedures are analyzed and compared. The early rehabilitative interventions are characterized by constant cooperation in the therapeutic team, especially neurological early rehabilitation through the incorporation of nursing as a therapeutic profession. Whereas geriatric and neurological early rehabilitation are reflected in the DRG system, the former provided in many general hospitals and the latter mainly in specialized institutions, interdisciplinary early rehabilitation has only occasionally been represented in the DRG system so far. If all acute in-patients who require early rehabilitation should receive such an intervention, an additional fee must be implemented for this this interdisciplinary service.

  6. Can Halogen Enrichment in Reduced Enstatite Chondrites Provide Clues to Volatile Accretion in the Early Earth?

    NASA Astrophysics Data System (ADS)

    Clay, P. L.; Burgess, R.; Busemann, H.; Ruzié, L.; Joachim, B.; Ballentine, C.

    2013-12-01

    Understanding how the Earth obtained and ultimately retained its volatiles is important for our overall understanding of large scale planetary evolution. Numerous models exist for the heterogeneous accretion of volatiles to early Earth, but accounting for all elements through accretion of typical planetary building blocks (e.g., CI chondrites) is difficult. Proto-planetary collisions resulting in the accretion of volatile-poor material under reducing conditions followed by accretion of volatile-rich material under oxidizing conditions has been suggested in such models [e.g., 1]. The heavy halogens (Cl, Br and I), a group of moderately volatile elements, are excellent tracers of planetary processing due to their low abundance and incompatible nature. Therefore characterizing halogen abundance and distribution in materials that accreted to form the planets, e.g., primitive meteorites, is crucial. One group of primitive meteorites, the enstatite chondrites (EC's), are amongst the most reduced materials in the solar system as evidenced by their unique mineral assemblage. Yet despite forming under ultra-reducing conditions, they are enriched in the moderately volatile elements, such as the halogens. The ECs are of particular interest owing to their oxygen isotopic composition which plots along the terrestrial fractionation line, linking them isotopically to the Earth-Moon system. These samples can thus potentially provide clues on the accretion of moderately volatile element rich material under reducing conditions, such as it may have existed during the early stages of Earth's accretion. Chlorine, Br and I concentrations in ECs were determined through step-heating small neutron-irradiated samples (0.3 to 3.3 mg) and measured by mass spectrometry using the noble gas proxy isotopes 38ArCl/Cl, 80KrBr/Br and 128XeI/I. The EH chondrites are consistently enriched in the heavy halogens (up to 330 ppm Cl, 2290 ppb Br and 180 ppb I), compared to other ordinary and carbonaceous

  7. Soviet early warning satellites

    NASA Astrophysics Data System (ADS)

    Perry, G. E.

    1982-02-01

    Satellite orbits and groups for the Cosmos spacecraft are discussed, noting that the orbits are configured to provide full early warning system coverage. The regular crossing of a ground track which includes all the Minuteman bases in the U.S. is noted, as are time constraints for the launch into a suitable orbit without introducing orbital anomalies. Cosmos 1024 was observed to need four corrections in order to reach a point where free libration over a fixed ground station was possible for a year until replacement by the Cosmos 1124 occurred. The current configuration is a total of nine satellites with 40 deg spacing, which yields full coverage, although it is indicated that only three satellites ever operate simultaneously.

  8. Early Cutaneous Lupus Erythematosus

    PubMed Central

    Sams, Wiley M.

    1966-01-01

    Cutaneous disorders which manifest themselves on the exposed parts are more likely than are hidden lesions to cause the patient to seek professional services promptly. Usually he consults his family physician or the community dermatologist. The physician who first sees the patient is dependent upon his own resources for management and diagnosis. A background of experience, a measure of energy and an inquisitive attitude are the necessary ingredients for successful management. The difficulties involved in differentiating early lupus erythematosus and polymorphic light eruptions cannot be invariably resolved even with the most complete review. The course of the disorder and the response to environmental factors supply important clues. Investigative work, especially in the field of immunology, offers hope for the solution of some of our problems. PMID:5909872

  9. Early stellar evolution

    NASA Technical Reports Server (NTRS)

    Stahler, Steven W.

    1994-01-01

    Research into the formation and early evolution of stars is currently an area of great interest and activity. The theoretical and observational foundations for this development are reviewed in this paper. By now, the basic physics governing cloud collapse is well understood, as is the structure of the resulting protostars. However, the theory predicts protostellar luminosities that are greater than those of most infrared sources. Observationally, it is thought that protostars emit powerful winds that push away remnant cloud gas, but both the origin of these winds and the nature of their interaction with ambient gas are controversial. Finally, the theory of pre-main-sequence stars has been modified to incorporate more realistic initial conditions. This improvement helps to explain the distribution of such stars in the H-R diagram. Many important issues, such as the origin of binary stars and stellar clusters, remain as challenges for future research.

  10. Icebergs on early Mars

    NASA Astrophysics Data System (ADS)

    Uceda, E.; Fairen, A.; Woodworth-Lynas, C.; Palmero Rodriguez, A.

    2015-12-01

    The smooth topography of the Martian northern lowlands has been classically equated to an ancient ocean basin. The High-Resolution Imaging Science Experiment (HiRISE) onboard the Mars Reconnaissance Orbiter (MRO) is providing unprecedented images of the Martian surface at scales of 25 to 32 cm per pixel. The analysis of this high-resolution imaging reveals the presence of three differentiated geomorphologies throughout the northern lowlands of Mars and the Hellas basin, which are informative of the presence of icebergs floating in ancient oceans and/or seas. These morphologies are: (i) scattered scour marks, including curvilinear furrows several km long and some meters deep; (ii) boulders ranging in size from 0.5 m to ~2 m in diameter, distributed forming clusters with sizes from several hundred meters to 1-2 km; and (iii) flat-topped and conical circular fractured mounds. The association of plough marks, clusters of boulders and mounds on the northern plains of Mars can be related to the dual processes of ice keel scouring and ice rafting of both glacial and non-glacial detritus by a floating ice canopy and icebergs. These processes are well documented on Earth and result in distinct morphologies on the ocean floor, which are analogous to features observed in the Martian basins. Importantly, the features are located in elevated areas of the northern plains and Hellas, near the dichotomy boundary and on local topographic highs. Such distribution is expected, as these relatively shoal areas are where the iceberg-related features should occur on Mars: these areas had shallow water depths, less than the iceberg's keel depth, and therefore keels reached through the full depth of the water column to impinge on the sediments below. The presence of icebergs floating in cold oceans early in Mars' history imply the occurrence of continental glaciers forming in the highlands and streaming northward towards the lowlands, and towards the Hellas and Argyre Basins. Glacier

  11. NGIPS Early Design Space Assessment

    DTIC Science & Technology

    2014-07-17

    advantageous . Neglect of electrical dynamics has proven very useful for early -stage design space exploration [4]-[6], [8]. However, these approaches are...Technical Report 3. DATES COVERED (From - To) 03/01/2012-03/31/2014 4. TITLE AND SUBTITLE NGIPS Early Design Space Assessment 5a. CONTRACT...perform shipboard power system performance metric refinements, early - stage assessment computational tool investigation, and the application of these

  12. Cyber Early Warning System (CEWAS)

    DTIC Science & Technology

    2006-03-01

    AFRL-IF-RS-TR-2006-103 Final Technical Report March 2006 CYBER EARLY WARNING SYSTEM (CEWAS) Telcordia Technologies...ONLY (Leave blank) 2. REPORT DATE MARCH 2006 3. REPORT TYPE AND DATES COVERED Final Aug 04 – Dec 06 4. TITLE AND SUBTITLE CYBER EARLY WARNING ...that are in their initial stages or in progress. 4 The Enhanced InFilter system has the capability to provide early notification of cyber

  13. Can Pancreatic Cancer Be Found Early?

    MedlinePlus

    ... Team About Pancreatic Cancer? Pancreatic Cancer Early Detection, Diagnosis, and Staging Can Pancreatic Cancer Be Found Early? Pancreatic cancer is hard to find early. The pancreas is deep inside the body, so early tumors ...

  14. Neodymium and lead isotope evidence for enriched early Archean crust in North America

    NASA Technical Reports Server (NTRS)

    Bowring, Samuel A.; Housh, Todd B.; Isachsen, Clark E.; Podosek, Frank A.; King, Janet E.

    1989-01-01

    Neodymium and lead isotope measurements and uranium-lead zircon geochronology from Archaean gneisses of the Slave Province in the Northwest Territories of Canada are reported. The gneisses contain zircons with cores older than 3.842 Gyr and an epsilon(Nd) (3.7 Gyr) of - 4.8. This is the oldest reported chondritic model age for a terrestrial sample and provides evidence for strongly enriched pre-3.8-Gyr crust, a reservoir complementary to the depleted mantle already in existence by 3.8 Gyr before the present.

  15. [The early diagnosis of spondyloarthritis].

    PubMed

    Novak, Srdan

    2011-01-01

    The most frequent early symptoms of spondyloarthritides are inflammatory back pain and asymetric peripheral arthritis. Currently the mean delay between the onset of first symptoms and diagnosing ankylosing spondylitis which is the frequent type of spondyloarthritis is over 5 years. The availability of effective therapies makes an early diagnosis mandatory. The clinical symptoms of inflammatory back pain, active inflamation on MR, and positivity for HLA-B27 are the most important parameters for an early diagnosis of spondyloarthritis, especially in combination. Moreover, the combination of clinical and laboratory parameters is necessary for the early diagnosis.

  16. Early humour production.

    PubMed

    Hoicka, Elena; Akhtar, Nameera

    2012-11-01

    The current studies explored early humour as a complex socio-cognitive phenomenon by examining 2- and 3-year-olds' humour production with their parents. We examined whether children produced novel humour, whether they cued their humour, and the types of humour produced. Forty-seven parents were interviewed, and videotaped joking with their children. Other parents (N= 113) completed a survey. Parents reported children copy jokes during the first year of life, and produce novel jokes from 2 years. In play sessions, 3-year-olds produced mostly novel humorous acts; 2-year-olds produced novel and copied humorous acts equally frequently. Parents reported children smile, laugh, and look for a reaction when joking. In play sessions, 2- and 3-year-olds produced these behaviours more when producing humorous versus non-humorous acts. In both parent reports and play sessions, they produced novel object-based (e.g., underwear on head) and conceptual humour (e.g., 'pig says moo') and used wrong labels humorously (e.g., calling a cat a dog). Thus, parent report and child behaviour both confirm that young children produce novel humorous acts, and share their humour by smiling, laughing, and looking for a reaction.

  17. Biosignatures of early earths

    NASA Technical Reports Server (NTRS)

    Pilcher, Carl B.

    2003-01-01

    A major goal of NASA's Origins Program is to find habitable planets around other stars and determine which might harbor life. Determining whether or not an extrasolar planet harbors life requires an understanding of what spectral features (i.e., biosignatures) might result from life's presence. Consideration of potential biosignatures has tended to focus on spectral features of gases in Earth's modern atmosphere, particularly ozone, the photolytic product of biogenically produced molecular oxygen. But life existed on Earth for about 1(1/2) billion years before the buildup of atmospheric oxygen. Inferred characteristics of Earth's earliest biosphere and studies of modern microbial ecosystems that share some of those characteristics suggest that organosulfur compounds, particularly methanethiol (CH(3)SH, the sulfur analog of methanol), may have been biogenic products on early Earth. Similar production could take place on extrasolar Earth-like planets whose biota share functional chemical characteristics with Earth life. Since methanethiol and related organosulfur compounds (as well as carbon dioxide) absorb at wavelengths near or overlapping the 9.6-microm band of ozone, there is potential ambiguity in interpreting a feature around this wavelength in an extrasolar planet spectrum.

  18. Early Alzheimer's disease genetics.

    PubMed

    Schellenberg, Gerard D

    2006-01-01

    The genetics community working on Alzheimer's disease and related dementias has made remarkable progress in the past 20 years. The cumulative efforts by multiple groups have lead to the identification of three autosomal dominant genes for early onset AD. These are the amyloid-beta protein precursor gene (APP), and the genes encoding presenilin1 and 2. The knowledge derived from this work has firmly established Abeta as a critical disease molecule and lead to candidate drugs currently in treatment trials. Work on a related disease, frontotemporal dementia with parkinsonism - chromosome 17 type has also added to our understanding of pathogenesis by revealing that tau, the protein component of neurofibrillary tangles, is also a critical molecule in neurodegeneration. Lessons learned that still influence work on human genetics include the need to recognize and deal with genetic heterogeneity, a feature common to many genetic disorders. Genetic heterogeneity, if recognized, can be source of information. Another critical lesson is that clinical, molecular, and statistical scientists need to work closely on disease projects to succeed in solving the complex problems of common genetic disorders.

  19. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    John S. Abughazaleh; Mushtaq Ahmed; Ashok Anand; John H. Anderson; Charles Benham; Fred D. Brent; Thomas E. Chance; William K. Davis; Raymond F. Drnevich; Larry Hall; Ming He; Stephen A. Lang; Jimmy O. Ong; Sarah J. Patel; George Potoczniak; Adela G. Sanchez; Charles H. Schrader; Lalit S. Shah; Phil J. Shires; Rae Song

    2000-10-26

    The overall objective of this project is the three phase development of an Early Entrance Coproduction Plant (EECP) which produces at least one product from at least two of the following three categories: (1) electric power (or heat), (2) fuels, and (3) chemicals. The objective is to have these products produced by technologies capable of using synthesis gas derived from coal and/or other carbonaceous feedstock. The objective of Phase I is to determine the feasibility and define the concept for the EECP located at a specific site and to develop a Research, Development, and Testing Plan (RD and T) for implementation in Phase II. The objective of Phase II is to implement the RD and T as outlined in the Phase I RD and T Plan to enhance the development and commercial acceptance of coproduction technology that produces high-value products, particularly those that are critical to our domestic fuel and power requirements. The project will resolve critical knowledge and technology gaps on the integration of gasification and downstream processing to coproduce some combination of power, fuels, and chemicals from coal and other feedstocks. The objective of Phase III is to develop an engineering design package and a financing plan for an EECP located at a specific site. The project's intended result is to provide the necessary technical, economic, and environmental information that will be needed to move the EECP forward to detailed design, construction, and operation by industry.

  20. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    John S. Abughazaleh; Mushtaq Ahmed; Ashok Anand; John H. Anderson; Charles Benham; Fred D. Brent; Thomas E. Chance; William K. Davis; Raymond F. Drnevich; Larry Hall; Ming He; Stephen A. Lang; David Mintner; Wendy Moore; Jimmy O. Ong; George Potoczniak; Adela G. Sanchez; Charles H. Schrader; Lalit S. Shah; Kalapi D. Sheth; Phil J. Shires; Rae Song

    2001-05-17

    The overall objective of this project is the three-phase development of an Early Entrance Coproduction Plant (EECP) that produces at least one product from at least two of the following three categories: Electric power (or heat); Fuels; and Chemicals. The objective is to have these products produced by technologies capable of using synthesis gas derived from coal and/or some other carbonaceous feedstock, such as petroleum coke. The objective of Phase I was to determine the feasibility and define the concept for the EECP located at a specific site and to develop a Research, Development, and Testing (RD and T) Plan for implementation in Phase II. This objective has now been accomplished. A specific site, Motiva Refinery in Port Arthur, Texas, has been selected as the location best suited for the EECP. The accomplishments of Phase I are discussed in detail in this Phase I Concept Report. A RD and T Plan and a preliminary project financing plan have been developed and are submitted separately from this report.

  1. Biosignatures of early earths.

    PubMed

    Pilcher, Carl B

    2003-01-01

    A major goal of NASA's Origins Program is to find habitable planets around other stars and determine which might harbor life. Determining whether or not an extrasolar planet harbors life requires an understanding of what spectral features (i.e., biosignatures) might result from life's presence. Consideration of potential biosignatures has tended to focus on spectral features of gases in Earth's modern atmosphere, particularly ozone, the photolytic product of biogenically produced molecular oxygen. But life existed on Earth for about 1(1/2) billion years before the buildup of atmospheric oxygen. Inferred characteristics of Earth's earliest biosphere and studies of modern microbial ecosystems that share some of those characteristics suggest that organosulfur compounds, particularly methanethiol (CH(3)SH, the sulfur analog of methanol), may have been biogenic products on early Earth. Similar production could take place on extrasolar Earth-like planets whose biota share functional chemical characteristics with Earth life. Since methanethiol and related organosulfur compounds (as well as carbon dioxide) absorb at wavelengths near or overlapping the 9.6-microm band of ozone, there is potential ambiguity in interpreting a feature around this wavelength in an extrasolar planet spectrum.

  2. The Early Experiments

    NASA Astrophysics Data System (ADS)

    Garvey, Gerald

    2013-04-01

    Stuart Freedman obtained his PhD at Berkley with an experimental thesis providing very strong evidence against theories requiring local hidden variables. He then came to Princeton in 1972 and began collaboration on a search for second-class currents. These measurements are quite difficult as the effects are the order of 1%, demonstrating Freedman's drive to take on hard but important experiments. After carrying out some relatively standard nuclear physics measurements he moved on to Stanford in 1976. There, Freedman was involved in identifying measurements sensitive to the existence of light axions. He also carried out searches for various exotica that might be produced from cosmic rays or the SLAC beam stop. During this time he was collaborating with us at Argonne investigating nuclear parity violation and time-like axial beta decay. In 1982 Freedman came to Argonne where he worked on fundamental issues in neutron beta decay. He also initiated what was to become one of his trademarks, demonstrating that surprising peaks in the e^+-e^- spectrum observed in very heavy ion collisions were spurious. He further launched his first neutrino oscillation experiment. This period of early research was marked by a remarkable diversity of subject matter and approach.

  3. Early Diagnosis of Leptospirosis

    PubMed Central

    Babic-Erceg, Andrea; Karlovic-Martinkovic, Diana; Santini, Marija; Persic, Zdenka; Vilibic-Cavlek, Tatjana

    2014-01-01

    A 25-years old man from Zagreb, Croatia, was admitted to the University Hospital for Infectious Diseases four days after the onset of symptoms such as fever, intense pain in the calves and anuria. The patient owned a rabbit and, before the onset of the disease, repaired some rubber pipes damaged by rodents. At admission, he had a severe clinical picture with fever, hypotension, jaundice, immobility, and pain in leg muscles. Treatment with ceftriaxone was initiated in combination with volume restitution. Renal failure soon ensued. Consequently continuous venovenous hemodiaphiltration therapy was performed. Due to acute respiratory distress syndrome, the patient was mechanically ventilated. The patient’s condition gradually improved and he recovered fully from multi-organ failure. Diagnosis was confirmed by a microscopic agglutination test (MAT) covering 15 leptospira serovars and real-time polymerase-chain reaction (PCR). The first serum sample taken on day 6 tested negative for leptospira, while PCR showed positive results for leptospiral DNA. The second serum sample taken on day 13 tested positive for serovar Canicola serogroup Canicola, serovar Patoc, serovar Grippotyphosa serogroup Grippotyphosa and serovar Tarassovi serogroup Tarassovi (titre 4000, 4000, 1000 and 2000, respectively), while PCR was negative. This report highlights the benefits of combining MAT and PCR methods in early diagnosis of leptospirosis. PMID:25002958

  4. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Mushtaq Ahmed; John H. Anderson; Charles Benham; Earl R. Berry; Fred Brent; Belma Demirel; Ming He; Troy Raybold; Manuel E. Quintana; Lalit S. Shah; Kenneth A. Yackly

    2003-06-09

    The overall objective of this project is the three phase development of an Early Entrance Coproduction Plant (EECP) which produces at least one product from at least two of the following three categories: (1) electric power (or heat), (2) fuels, and (3) chemicals. The objective is to have these products produced by technologies capable of using synthesis gas derived from coal and/or other carbonaceous feedstocks. The objectives of Phase I were to determine the feasibility and define the concept for the EECP located at a specific site; develop a Research, Development, and Testing (RD&T) Plan for implementation in Phase II; and prepare a Preliminary Project Financing Plan. The objective of Phase II is to implement the work as outlined in the Phase I RD&T Plan to enhance the development and commercial acceptance of coproduction technology that produces high-value products, particularly those that are critical to our domestic fuel and power requirements. The project will resolve critical knowledge and technology gaps on the integration of gasification and downstream processing to coproduce some combination of power, fuels, and chemicals from coal and/or other carbonaceous feedstocks. The objective of Phase III is to develop an engineering design package and a financing and testing plan for an EECP located at a specific site. The project's intended result is to provide the necessary technical, economic, and environmental information needed by industry to move the EECP forward to detailed design, construction, and operation.

  5. Biosignatures of Early Earths

    NASA Astrophysics Data System (ADS)

    Pilcher, Carl B.

    2003-11-01

    A major goal of NASA's Origins Program is to find habitable planets around other stars and determine which might harbor life. Determining whether or not an extrasolar planet harbors life requires an understanding of what spectral features (i.e., biosignatures) might result from life's presence. Consideration of potential biosignatures has tended to focus on spectral features of gases in Earth's modern atmosphere, particularly ozone, the photolytic product of biogenically produced molecular oxygen. But life existed on Earth for about 1½ billion years before the buildup of atmospheric oxygen. Inferred characteristics of Earth's earliest biosphere and studies of modern microbial ecosystems that share some of those characteristics suggest that organosulfur compounds, particularly methanethiol (CH3SH, the sulfur analog of methanol), may have been biogenic products on early Earth. Similar production could take place on extrasolar Earth-like planets whose biota share functional chemical characteristics with Earth life. Since methanethiol and related organosulfur compounds (as well as carbon dioxide) absorb at wavelengths near or overlapping the 9.6-μm band of ozone, there is potential ambiguity in interpreting a feature around this wavelength in an extrasolar planet spectrum.

  6. Early Childhood Development in Saskatoon, Saskatchewan. Understanding the Early Years

    ERIC Educational Resources Information Center

    Willms, J. Douglas

    2002-01-01

    Understanding the Early Years (UEY) is a national research initiative. It provides communities with information to enable them to make informed decisions about the best policies and most appropriate programs for families with young children. It seeks to provide information about the influence of community factors on children's early development…

  7. Critical Questions about Early Intervention and Early Childhood Special Education

    ERIC Educational Resources Information Center

    Winer, Abby; Hebbeler, Kathy; Nelson, Robin; Gundler, Darla; Cate, Debbie; Hudson, Laura; Taylor, Cornelia; Peters, Mary Louise

    2015-01-01

    What is a high-quality statewide data system? One characteristic is that it provides the information needed to address important questions about early intervention and early childhood special education. But what are those questions? What questions should data users, such as program directors, advocates, and policymakers, be asking? The Center for…

  8. Early Attachment Relationships and the Early Childhood Curriculum

    ERIC Educational Resources Information Center

    Cortazar, Alejandra; Herreros, Francisca

    2010-01-01

    This article explores the relationship between attachment theory and the early childhood curriculum. During the first years of life children develop early attachment relationships with their primary caregivers. These attachment relationships, either secure or insecure, will shape children's socio-emotional development. In the USA, the predominant…

  9. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    John H. Anderson; William K. Davis; Thomas W. Sloop

    2001-03-21

    As part of the Department of Energy's (DOE) Gasification Technologies and Transportation Fuels and Chemicals programs, DOE and Texaco are partners through Cooperative Agreement DE-FC26-99FT40658 to determine the feasibility of developing, constructing and operating an Early Entrance Coproduction Plant (EECP). The overall objective of the project is the three-phase development of an EECP that produces at least one product from at least two of the following three categories: Electric power (or heat); Fuels; and Chemicals. The objective is to have these products produced by technologies capable of using synthesis gas derived from coal and/or some other carbonaceous feedstock, such as petroleum coke. The objective of Phase I was to determine the feasibility and define the concept for the EECP located at a specific site and to develop a Research, Development, and Testing (RD and T) Plan for implementation in Phase II. This objective has now been accomplished. A specific site, Motiva Refinery in Port Arthur, Texas, has been selected as the location best suited for the EECP. The specific work requirements of Phase I included: Prepare an EECP Preliminary Concept Report covering Tasks 2-8 specified in the Cooperative Agreement; Develop a Research, Development, and Testing (RD and T) Plan as specified in Task 9 of the Cooperative Agreement for implementation in Phase II; and Develop a Preliminary Project Financing Plan for the EECP Project as specified in Task 10 of the Cooperative Agreement. This document is the Preliminary Project Financing Plan for the design, construction, and operation of the EECP at the Motiva Port Arthur Refinery.

  10. Franco, the Early Days

    NASA Astrophysics Data System (ADS)

    Siemssen, R. H.

    2004-04-01

    As this meeting is to honour Franco on the occasion of his 60 birthday I thought that it might be fitting to report on some early reminiscences of Franco of the pre-IBA days. Franco first came to Groningen in 1972 for a seminar on the invitation of Alex Lande. Alex and Franco had known each other from the Niels Bohr Institute in Copenhagen, where they had collaborated. In 1972 both Alex and I had been freshly appointed at Groningen, Alex on the Faculty of the Theory Department, and I myself as the new director of the KVI. A position for a Senior Scientist in theory had been newly created at the KVI with the aim to establish a strong in-house theory group. Needless to say that everyone who met Franco was deeply impressed by him. We thus were extremely happy to be able to entice Franco to join the KVI as a Senior Scientist in 1974, after he had spent a few weeks in Groningen in 1973 as a visitor. So characteristic of Franco he immediately took a strong interest in the experimental program as evidenced by the following publications on the weak-coupling description of three-nucleon pickup in the (p, α) reaction [1] and the spreading width of deep-hole states [2]. Both topics appear to have maintained their actuality, looking at the many papers that have been published since on these and related topics. But this brief citation of the "other Franco" would not do justice to him without mentioning the diverse palette of Franco's work also listed in the KVI 1974 Annual Report, reflecting Franco's extremely broad and diversified scientific interests. [3-10]...

  11. Early amplification options.

    PubMed

    Gabbard, Sandra Abbott; Schryer, Jennifer

    2003-01-01

    Children with permanent hearing loss have been remediated with hearing amplification devices for decades. The influx of young infants identified with hearing loss through successful newborn hearing screening programs has established a need for amplification resources for infants within the first six months of life. For the approximately two of every 1000 infants born who are identified with bilateral hearing loss [Mehl and Thomson, 1998, Pediatrics 101, p. e4], the use of amplification is commonly the first step in treating the sequella of their loss. The use of hearing aids, combined with early intervention, has been shown to significantly improve the speech and language skills of young children with hearing loss [Yoshinaga-Itano, 2000, Seminars in Hearing 21, p. 309]. Speech and language delays have contributed to compromised academic performance of school aged children with hearing loss [Johnson et al., 1997, Educational Audiology Handbook, Singular Publishing, San Diego]. Most hard-of-hearing and deaf children use hearing aids and other assistive listening devices every day throughout their lifetime and the life expectancy of a hearing aid is only five to eight years. The current challenge for pediatric audiologists is selecting and evaluating the available amplification to provide the best options for children and their families. Amplification technology has seen an explosion in growth the past few years and the options continue to expand rapidly. This article examines currently available amplification technology and reviews the selection criteria that may be used for infants and young children. Issues such as style, type, amplification features, signal processing strategies, and verification and validation tools are also discussed.

  12. Early Solar System Chronology

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.; Davis, A. M.

    2003-12-01

    Chondritic Meteorites as Probes of Early Solar System EvolutionThe evolutionary sequence involved in the formation of relatively low-mass stars, such as the Sun, has been delineated in recent years through impressive advances in astronomical observations at a variety of wavelengths, combined with improved numerical and theoretical models of the physical processes thought to occur during each stage. From the models and the observational statistics, it is possible to infer in a general way how our solar system ought to have evolved through the various stages from gravitational collapse of a fragment of a molecular cloud to the accretion of planetary-sized bodies (e.g., Cameron, 1995; Alexander et al., 2001; Shu et al., 1987; André et al., 2000; see Chapters 1.04, 1.17, and 1.20). However, the details of these processes remain obscured, literally from an astronomical perspective, and the dependence of such models on various parameters requires data to constrain the specific case of our solar system's origin.Fortunately, the chondritic meteorites sample aspects of this evolution. The term "chondrite" (or chondritic) was originally applied to meteorites bearing chondrules, which are approximately millimeter-sized solidified melt droplets consisting largely of mafic silicate minerals and glass commonly with included metal or sulfide. However, the meaning of chondritic has been expanded to encompass all extraterrestrial materials that are "primitive," i.e., are undifferentiated samples having nearly solar elemental composition. Thus, the chondrites represent a type of cosmic sediment, and to a first approximation can be thought of as "hand samples" of the condensable portion of the solar nebula. The latter is a general term referring to the phase(s) of solar system evolution intermediate between molecular cloud collapse and planet formation. During the nebular phase, the still-forming Sun was an embedded young-stellar object (YSO) enshrouded by gas and dust, which was

  13. Promoting Health in Early Childhood

    ERIC Educational Resources Information Center

    Rossin-Slater, Maya

    2015-01-01

    Children who are healthy early in life--from conception to age five--not only grow up to be healthier adults, they are also better educated, earn more, and contribute more to the economy. The United States lags behind other advanced countries in early childhood health, threatening both the health of future generations and the nation's long-term…

  14. Missouri: Early Head Start Initiative

    ERIC Educational Resources Information Center

    Center for Law and Social Policy, Inc. (CLASP), 2012

    2012-01-01

    Missouri's Early Head Start/Child Care Partnership Project expands access to Early Head Start (EHS) services for children birth to age 3 by developing partnerships between federal Head Start, EHS contractors, and child care providers. Head Start and EHS contractors that participate in the initiative provide services through community child care…

  15. Expertise of Early Childhood Educators

    ERIC Educational Resources Information Center

    Happo, Iiris; Määttä, Kaarina

    2011-01-01

    Every preschool age child in Finland has the right to day care and the expertise of educators is multidimensional. The aim of this article is to clarify the expertise of those early childhood educators, who have the competence of kindergarten teachers (n = 80). The data consisted of the early educators' stories of their growth towards expertise.…

  16. Family Influences on Early Development.

    ERIC Educational Resources Information Center

    Silber, Sharon

    1989-01-01

    The article reviews the literature concerning family influences on early childhood development. Implications of this literature for intervention planning with high risk children and families are suggested. Topics covered include the early parent-child relationship, disciplinary strategies, stimulation, parental instruction and expectations, the…

  17. Voluntary Incentive Early Retirement Programs.

    ERIC Educational Resources Information Center

    Research Dialogues, 1988

    1988-01-01

    Arrangements in educational institutions for voluntary early retirement programs are discussed. Retirement at any age can be a profound and stressful lifetime change; and it can also represent a welcome transition into newly satisfying and rewarding opportunities. The focus is on: mandatory retirement (exceptions and the new meaning of "early");…

  18. Early Childhood Inclusion in Spain

    ERIC Educational Resources Information Center

    Giné, Climent; Balcells-Balcells, Anna; Cañadas, Margarita; Paniagua, Gema

    2016-01-01

    This article describes early childhood inclusion in educational settings in Spain. First, we address the legislative framework of preschool education in Spain and offer a brief analysis of some relevant issues, including the current situation of early childhood education and inclusion at this stage. Second, current policies and practices relating…

  19. Wyoming Early Childhood Readiness Standards.

    ERIC Educational Resources Information Center

    Wyoming State Dept. of Education, Cheyenne.

    Because children entering kindergarten come with a variety of preschool and home experiences, and accordingly, with varying levels of school readiness, the Wyoming Early Childhood Readiness Standards have been developed to provide a more consistent definition of school readiness. The goal for the Standards is to provide early childhood educators…

  20. Teachers in Early Childhood Policy

    ERIC Educational Resources Information Center

    Kilderry, Anna

    2014-01-01

    This paper examines teacher accountability and authority in early childhood policy. It reports on data from a study that investigated the influences affecting early childhood teacher decision-making at the preschool level in Victoria, Australia. Using a question raised by Ball "Where are the teachers in all this [policy]?" provided a…

  1. Early osteoarthritis of the knee.

    PubMed

    Madry, Henning; Kon, Elizaveta; Condello, Vincenzo; Peretti, Giuseppe M; Steinwachs, Matthias; Seil, Romain; Berruto, Massimo; Engebretsen, Lars; Filardo, Giuseppe; Angele, Peter

    2016-06-01

    There is an increasing awareness on the importance in identifying early phases of the degenerative processes in knee osteoarthritis (OA), the crucial period of the disease when there might still be the possibility to initiate treatments preventing its progression. Early OA may show a diffuse and ill-defined involvement, but also originate in the cartilage surrounding a focal lesion, thus necessitating a separate assessment of these two entities. Early OA can be considered to include a maximal involvement of 50 % of the cartilage thickness based on the macroscopic ICRS classification, reflecting an OARSI grade 4. The purpose of this paper was to provide an updated review of the current status of the diagnosis and definition of early knee OA, including the clinical, radiographical, histological, MRI, and arthroscopic definitions and biomarkers. Based on current evidence, practical classification criteria are presented. As new insights and technologies become available, they will further evolve to better define and treat early knee OA.

  2. Early Diagnosis and Early Intervention in Cerebral Palsy

    PubMed Central

    Hadders-Algra, Mijna

    2014-01-01

    This paper reviews the opportunities and challenges for early diagnosis and early intervention in cerebral palsy (CP). CP describes a group of disorders of the development of movement and posture, causing activity limitation that is attributed to disturbances that occurred in the fetal or infant brain. Therefore, the paper starts with a summary of relevant information from developmental neuroscience. Most lesions underlying CP occur in the second half of gestation, when developmental activity in the brain reaches its summit. Variations in timing of the damage not only result in different lesions but also in different neuroplastic reactions and different associated neuropathologies. This turns CP into a heterogeneous entity. This may mean that the best early diagnostics and the best intervention methods may differ for various subgroups of children with CP. Next, the paper addresses possibilities for early diagnosis. It discusses the predictive value of neuromotor and neurological exams, neuroimaging techniques, and neurophysiological assessments. Prediction is best when complementary techniques are used in longitudinal series. Possibilities for early prediction of CP differ for infants admitted to neonatal intensive care and other infants. In the former group, best prediction is achieved with the combination of neuroimaging and the assessment of general movements, in the latter group, best prediction is based on carefully documented milestones and neurological assessment. The last part reviews early intervention in infants developing CP. Most knowledge on early intervention is based on studies in high-risk infants without CP. In these infants, early intervention programs promote cognitive development until preschool age; motor development profits less. The few studies on early intervention in infants developing CP suggest that programs that stimulate all aspects of infant development by means of family coaching are most promising. More research is urgently needed

  3. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    David Storm; Govanon Nongbri; Steve Decanio; Ming He; Lalit Shah; Charles Schrader; Earl Berry; Peter Ricci; Belma Demirel; Charles Benham; Mark Bohn

    2004-01-12

    The overall objective of this project is the three phase development of an Early Entrance Coproduction Plant (EECP) which uses petroleum coke to produce at least one product from at least two of the following three categories: (1) electric power (or heat), (2) fuels, and (3) chemicals using ChevronTexaco's proprietary gasification technology. The objective of Phase I is to determine the feasibility and define the concept for the EECP located at a specific site; develop a Research, Development, and Testing (RD&T) Plan to mitigate technical risks and barriers; and prepare a Preliminary Project Financing Plan. The objective of Phase II is to implement the work as outlined in the Phase I RD&T Plan to enhance the development and commercial acceptance of coproduction technology. The objective of Phase III is to develop an engineering design package and a financing and testing plan for an EECP located at a specific site. The project's intended result is to provide the necessary technical, economic, and environmental information needed by industry to move the EECP forward to detailed design, construction, and operation. The partners in this project are Texaco Energy Systems LLC or TES (a subsidiary of ChevronTexaco), General Electric (GE), Praxair, and Kellogg Brown & Root (KBR) in addition to the U.S. Department of Energy (DOE). TES is providing gasification technology and Fischer-Tropsch (F-T) technology developed by Rentech, Inc., GE is providing combustion turbine technology, Praxair is providing air separation technology, and KBR is providing engineering. During Phase I, a design basis for the Fischer-Tropsch Synthesis section was developed based on limited experience with the specified feed gas and operating conditions. The objective of this Task in Phase II RD&T work was to confirm the performance of the F-T reactor at the set design conditions. Although much of the research, development, and testing work were done by TES outside of this project, several important

  4. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Fred D. Brent; Lalit Shah; Earl Berry; Charles H. Schrader; John Anderson; Ming He; James F. Stevens; Centha A. Davis; Michael Henley; Jerome Mayer; Harry Tsang; Jimell Erwin; Jennifer Adams; Michael Tillman; Chris Taylor; Marjan J. Roos; Robert F. Earhart

    2004-01-27

    The overall objective of this project is the three phase development of an Early Entrance Coproduction Plant (EECP) which uses petroleum coke to produce at least one product from at least two of the following three categories: (1) electric power (or heat), (2) fuels, and (3) chemicals using ChevronTexaco's proprietary gasification technology. The objective of Phase I is to determine the feasibility and define the concept for the EECP located at a specific site; develop a Research, Development, and Testing (RD&T) Plan to mitigate technical risks and barriers; and prepare a Preliminary Project Financing Plan. The objective of Phase II is to implement the work as outlined in the Phase I RD&T Plan to enhance the development and commercial acceptance of coproduction technology. The objective of Phase III is to develop an engineering design package and a financing and testing plan for an EECP located at a specific site. The project's intended result is to provide the necessary technical, economic, and environmental information needed by industry to move the EECP forward to detailed design, construction, and operation. The partners in this project are Texaco Energy Systems LLC or TES (a subsidiary of ChevronTexaco), General Electric (GE), Praxair, and Kellogg Brown & Root (KBR) in addition to the U.S. Department of Energy (DOE). TES is providing gasification technology and Fischer-Tropsch (F-T) technology developed by Rentech, GE is providing combustion turbine technology, Praxair is providing air separation technology, and KBR is providing engineering. Each of the EECP subsystems was assessed for technical risks and barriers. A plan was developed to mitigate the identified risks (Phase II RD&T Plan, October 2000). The potential technical and economic risks to the EECP from Task 2.5 can be mitigated by demonstrating that the end-use products derived from the upgrading of the F-T synthesis total liquid product can meet or exceed current specifications for the manufacture

  5. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    John Anderson; Charles Schrader

    2004-01-26

    In 1999, the U. S. Department of Energy (DOE) awarded a Cooperative Agreement to Texaco Energy Systems Inc. to provide a preliminary engineering design of an Early Entrance Coproduction Plant (EECP). Since the award, continuous and diligent work has been undertaken to achieve the design of an economical facility that makes strides toward attaining the goal of DOE's Vision 21 Program. The objective of the EECP is to convert coal and/or petroleum coke to power while coproducing transportation fuels, chemicals, and useful utilities such as steam. This objective is being pursued in a three-phase effort through the partnership of the DOE with prime contractor Texaco Energy Systems, LLC. (TES), the successor to Texaco Energy Systems, Inc. The key subcontractors to TES include General Electric (GE), Praxair, and Kellogg Brown and Root. ChevronTexaco provided gasification technology and Rentech Inc.'s Fischer-Tropsch (F-T) technology that has been developed for non-natural gas sources. GE provided gas turbine technology for the combustion of low energy content gas. Praxair provided air separation technology and KBR provided engineering to integrate the facility. A conceptual design was completed in Phase I and the report was accepted by the DOE in May 2001. The Phase I work identified risks and critical research, development, and testing that would improve the probability of technical success of the EECP. The objective of Phase II was to mitigate the risks by executing research, development, and testing. Results from the Phase II work are the subject of this report. As the work of Phase II concluded, it became evident that sufficient, but not necessarily complete, technical information and data would be available to begin Phase III - Preliminary Engineering Design. Work in Phase II requires additional technical development work to correctly apply technology at a specific site. The project's intended result is to provide the necessary technical, economic, and environmental

  6. What Works Clearinghouse Quick Review: "Early College, Early Success: Early College High School Initiative Impact Study"

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2013

    2013-01-01

    The study examined in this quick review concerns whether attending Early College High Schools increased postsecondary outcomes. This study is a randomized experiment examining the impact of Early Colleges on a number of outcomes. The study had relatively low attrition rates (approximately 7% in the intervention group and 13% in the comparison…

  7. Early traumatic events in psychopaths.

    PubMed

    Borja, Karina; Ostrosky, Feggy

    2013-07-01

    The relationship between diverse early traumatic events and psychopathy was studied in 194 male inmates. Criminal history transcripts were revised, and clinical interviews were conducted to determine the level of psychopathy using the Psychopathy Checklist-Revised (PCL-R) Form, and the Early Trauma Inventory was applied to assess the incidence of abuse before 18 years of age. Psychopathic inmates presented a higher victimization level and were more exposed to certain types of intended abuse than sociopathic inmates, while the sum of events and emotional abuse were associated with the PCL-R score. Our studies support the influence of early adverse events in the development of psychopathic offenders.

  8. Early Warning and the Tank

    DTIC Science & Technology

    1989-06-01

    recharge the batteries. Naturally, this makes the tank more detectable. THE PEWS EARLY WARNING SYSTEM U.S. tank platoons currently have one Platoon... Early Warning System ( PEWS ) per platoon. These con- tain 10 seismic sensors which can be placed a kilometer or so foreward. A panel of lights indicates...BRL-.MR-3’E i" MEMORANDUM REPORT BRL-MR-3767 ’B𔃽BRL EARLY WARNING AND THE TANK FRED L. BUNN s IN JUN 16 1989 " JUNE 1989 APPROVED FOR PUBLIC RELEASE

  9. Mars and the early Sun

    NASA Technical Reports Server (NTRS)

    Whitmire, D. P.; Doyle, L. R.; Reynolds, R. T.; Whitman, P. G.

    1993-01-01

    Global mean temperatures near 273 K on early Mars are difficult to explain in the context of standards solar evolution models. Even assuming maximum CO2 greenhouse warming, the required flux is approximately 15 percent too low. Here we consider two astrophysical models that could increase the flux by this amount. The first model is a nonstandard solar model in which the early Sun had a mass somewhat greater than today's mass (1.02-1.06 solar mass). The second model is based on a standard evolutionary solar model, but the ecliptic flux is increased due to focusing by an (expected) heavily spotted early Sun.

  10. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Charles Benham; Mark Bohn; John Anderson; Earl Berry; Fred Brent; Ming He; Randy Roberts; Lalit Shah; Marjan Roos

    2003-09-15

    The 1999 U. S. Department of Energy (DOE) award to Texaco Energy Systems Inc. (presently Texaco Energy Systems LLC, a subsidiary of ChevronTexaco) was made to provide a Preliminary Engineering Design of an Early Entrance Coproduction Plant (EECP). Since the award presentation, work has been undertaken to achieve an economical concept design that makes strides toward the DOE Vision 21 goal. The objective of the EECP is to convert coal and/or petroleum coke to electric power plus transportation fuels, chemicals and useful utilities such as steam. The use of petroleum coke was added as a fuel to reduce the cost of feedstock and also to increase the probability of commercial implementation of the EECP concept. This objective has been pursued in a three phase effort through the partnership of the DOE with prime contractor Texaco Energy Systems LLC and subcontractors General Electric (GE), Praxair, and Kellogg Brown and Root (KBR). ChevronTexaco is providing gasification technology and Rentech's Fischer-Tropsch technology that has been developed for non-natural gas feed sources. GE is providing gas turbine technology for the combustion of low energy content gas. Praxair is providing air separation technology, and KBR is providing engineering to integrate the facility. The objective of Phase I was to determine the feasibility and define the concept for the EECP located at a specific site; develop a Research, Development, and Testing (RD&T) Plan to mitigate technical risks and barriers; and prepare a Preliminary Project Financing Plan. The objective of Phase II is to implement the work as outlined in the Phase I RD&T Plan to enhance the development and commercial acceptance of coproduction technology. The objective of Phase III is to develop an engineering design package and a financing and testing plan for an EECP located at a specific site. Phase I Preliminary Concept Report was completed in 2000. The Phase I Preliminary Concept Report was prepared based on making

  11. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    John H. Anderson; Charles Benham; Earl R. Berry; Ming He; Charles H. Schrader; Lalit S. Shah; O.O. Omatete; T.D. Burchell

    2004-01-12

    The overall objective of this project is the three phase development of an Early Entrance Coproduction Plant (EECP) which uses petroleum coke to produce at least one product from at least two of the following three categories: (1) electric power (or heat), (2) fuels, and (3) chemicals using ChevronTexaco's proprietary gasification technology. The objective of Phase I is to determine the feasibility and define the concept for the EECP located at a specific site; develop a Research, Development, and Testing (RD&T) Plan to mitigate technical risks and barriers; and prepare a Preliminary Project Financing Plan. The objective of Phase II is to implement the work as outlined in the Phase I RD&T Plan to enhance the development and commercial acceptance of coproduction technology. The objective of Phase III is to develop an engineering design package and a financing and testing plan for an EECP located at a specific site. The project's intended result is to provide the necessary technical, economic, and environmental information needed by industry to move the EECP forward to detailed design, construction, and operation. The partners in this project are Texaco Energy Systems LLC or TES (a subsidiary of ChevronTexaco), General Electric (GE), Praxair, and Kellogg Brown & Root (KBR) in addition to the U.S. Department of Energy (DOE). TES is providing gasification technology and Fischer-Tropsch (F-T) technology developed by Rentech, GE is providing combustion turbine technology, Praxair is providing air separation technology, and KBR is providing engineering. During Phase I the team identified several potential methods to reduce or minimize the environmental impact of the proposed EECP. The EECP Project Team identified F-T catalyst disposal, beneficial gasifier slag usage (other than landfill), and carbon dioxide recovery for the gas turbine exhaust for study under this task. Successfully completing the Task 2.10 RD&T provides additional opportunities for the EECP to meet the

  12. Early African Hominids: Pedagogic Patterns.

    ERIC Educational Resources Information Center

    Newman, James L.

    1984-01-01

    By studying early African hominids, students can learn about the interactive testing and creative aspects of scientific thinking and sharpen their geographical skills. It is impossible to study this topic without giving prominence to space and time. (RM)

  13. [Early diagnosis of skin cancer].

    PubMed

    Kolm, Isabell; Hofbauer, Günther; Braun, Ralph P

    2010-09-01

    The skin is the most affected organ by cancer. The incidence rates of skin cancer are steadily increasing, both for melanoma and non-melanoma skin cancers (squamous cell carcinoma, basal cell carcinoma). Over 90 % of the death cases from skin cancers attribute to melanoma. Survival from melanoma is strongly related to tumour thickness. Therefore early detection is the most important step to improve prognosis. In the last years a number of new non invasive techniques for the early diagnosis of melanoma have been developed which are superior to the naked eye examination. In this overview article we present some non-invasive diagnostic techniques like total body photography, digital dermoscopy and confocal microscopy which in addition to dermoscopy assist the dermatologist in differentiating nevi from early melanomas.Non-melanoma skin cancer can be prevented by accurate sun protection. Early squamous cell carcinomas and basal cell carcinomas can be treated either invasively or non-invasively with excellent prognosis.

  14. Sweetening Early-Retirement Programs.

    ERIC Educational Resources Information Center

    Hoffman, Jeffrey S.

    1990-01-01

    Early retirement programs do not necessarily result in the greatest savings. To ensure a successful program, employers must consider all factors that influence an employee's decision to participate. (JOW)

  15. Rural Early Education Access Act

    THOMAS, 111th Congress

    Rep. Hare, Phil [D-IL-17

    2009-03-26

    05/14/2009 Referred to the Subcommittee on Early Childhood, Elementary, and Secondary Education. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  16. Starting Early Starting Right Act

    THOMAS, 111th Congress

    Rep. Baldwin, Tammy [D-WI-2

    2009-12-16

    02/23/2010 Referred to the Subcommittee on Early Childhood, Elementary, and Secondary Education. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  17. Nonverbal Communication during Early Childhood.

    ERIC Educational Resources Information Center

    Knott, Gladys P.

    1979-01-01

    A brief overview and synthesis of current knowledge on the development of nonverbal communication in young children is presented, and implications for teacher-child interactions during the early school years are suggested. (JD)

  18. Developmental Milestones of Early Literacy

    MedlinePlus

    ... developmental milestones of early literacy. Younger Than 6 Months: Never Too Young Unlike solid foods , it is ... counts, so have fun with it! 6–12 Months: Developing a Taste for Books Whatever babies are ...

  19. Physics in the early universe

    NASA Astrophysics Data System (ADS)

    Huang, Qing-Guo

    In this paper, I will give a brief overview of the physics in the early universe, in particular, the inflation scenario. The predictions and the latest constraints on the inflation models will be discussed in detail.

  20. Epigenetics of Early Child Development

    PubMed Central

    Murgatroyd, Chris; Spengler, Dietmar

    2011-01-01

    Comprehensive clinical studies show that adverse conditions in early life can severely impact the developing brain and increase vulnerability to mood disorders later in life. During early postnatal life the brain exhibits high plasticity which allows environmental signals to alter the trajectories of rapidly developing circuits. Adversity in early life is able to shape the experience-dependent maturation of stress-regulating pathways underlying emotional functions and endocrine responses to stress, such as the hypothalamo–pituitary–adrenal (HPA) system, leading to long-lasting altered stress responsivity during adulthood. To date, the study of gene–environment interactions in the human population has been dominated by epidemiology. However, recent research in the neuroscience field is now advancing clinical studies by addressing specifically the mechanisms by which gene–environment interactions can predispose individuals toward psychopathology. To this end, appropriate animal models are being developed in which early environmental factors can be manipulated in a controlled manner. Here we will review recent studies performed with the common aim of understanding the effects of the early environment in shaping brain development and discuss the newly developing role of epigenetic mechanisms in translating early life conditions into long-lasting changes in gene expression underpinning brain functions. Particularly, we argue that epigenetic mechanisms can mediate the gene–environment dialog in early life and give rise to persistent epigenetic programming of adult physiology and dysfunction eventually resulting in disease. Understanding how early life experiences can give rise to lasting epigenetic marks conferring increased risk for mental disorders, how they are maintained and how they could be reversed, is increasingly becoming a focus of modern psychiatry and should pave new guidelines for timely therapeutic interventions. PMID:21647402

  1. NASA Early Career Fellowship Program

    NASA Astrophysics Data System (ADS)

    Smith, H. D.

    2012-12-01

    The Early Career Fellowship program was established in 2005 to facilitate the integration of outstanding early career planetary science researchers into established research funding programs by providing tools and experience useful to maintain a successful research program. Executing a successful research program requires a few key elements such as: successful proposal writing; adequate (paid) research time; management of a laboratory; collaboration and networking; frequent and high-quality publications; and adequate start-up equipment funds. These elements may be particularly critical for early career researchers searching for a tenure- track or equivalent position. The Early Career Fellowship program recognizes the importance of these skills and provides extra funding and resources to begin a successful research program. For consideration into The Early Career Fellowship program, the candidate needs to be the P. I. or Science P.I. of a funded research proposal from one of the participating R&A program areas, be within 7 years of earning a PhD, hold a non-tenure track position, and indicate the early career candidacy when submitting the research proposal. If the research proposal is funded and the discipline scientist nominates the candidate as an early career fellow, the candidate is then considered a Fellow and eligible to propose for Step 2. Upon obtaining a tenure-track equivalent position the Fellow submits a Step 2 proposal for up to one hundred thousand dollars in start-up funds. Start-up funds may be used for salary; undergraduate and/or graduate research assistants; supplies and instrument upgrades; travel to conferences, meetings, and advisory groups; time and travel for learning new skills; publication page charges; books and journal subscriptions; computer time and/or specialized software; and other justified research-specific needs. The early career fellowship program provides resources that a more established scientist would have acquired allowing

  2. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Fred D. Brent; Lalit Shah; Earl Berry; Charles H. Schrader; John Anderson; J. Erwin; Matthew G. Banks; Terry L. Ullman

    2004-01-12

    The overall objective of this project is the three phase development of an Early Entrance Coproduction Plant (EECP) which uses petroleum coke to produce at least one product from at least two of the following three categories: (1) electric power (or heat), (2) fuels, and (3) chemicals using ChevronTexaco's proprietary gasification technology. The objective of Phase I is to determine the feasibility and define the concept for the EECP located at a specific site; develop a Research, Development, and Testing (RD&T) Plan to mitigate technical risks and barriers; and prepare a Preliminary Project Financing Plan. The objective of Phase II is to implement the work as outlined in the Phase I RD&T Plan to enhance the development and commercial acceptance of coproduction technology. The objective of Phase III is to develop an engineering design package and a financing and testing plan for an EECP located at a specific site. The project's intended result is to provide the necessary technical, economic, and environmental information needed by industry to move the EECP forward to detailed design, construction, and operation. The partners in this project are Texaco Energy Systems LLC or TES (a subsidiary of ChevronTexaco), General Electric (GE), Praxair, and Kellogg Brown & Root (KBR) in addition to the U.S. Department of Energy (DOE). TES is providing gasification technology and Fischer-Tropsch (F-T) technology developed by Rentech, GE is providing combustion turbine technology, Praxair is providing air separation technology, and KBR is providing engineering. Each of the EECP subsystems was assessed for technical risks and barriers. A plan was developed to mitigate the identified risks (Phase II RD&T Plan, October 2000). Phase II RD&T Task 2.6 identified as potential technical risks to the EECP the fuel/engine performance and emissions of the F-T diesel fuel products. Hydrotreating the neat F-T diesel product reduces potentially reactive olefins, oxygenates, and acids levels

  3. Natural course of early COPD

    PubMed Central

    Rhee, Chin Kook; Kim, Kyungjoo; Yoon, Hyoung Kyu; Kim, Jee-Ae; Kim, Sang Hyun; Lee, Sang Haak; Park, Yong Bum; Jung, Ki-Suck; Yoo, Kwang Ha; Hwang, Yong Il

    2017-01-01

    Background and objective Few studies have examined the natural course of early COPD. The aim of this study was to observe the natural course of early COPD patients. We also aimed to analyze medical utilization and costs for early COPD during a 6-year period. Methods Patients with early COPD were selected from Korean National Health and Nutrition Examination Survey (KNHANES) data. We linked the KNHANES data of patients with early COPD to National Health Insurance data. Results A total of 2,397 patients were enrolled between 2007 and 2012. The mean forced expiratory volume in 1 second (FEV1) was 78.6%, and the EuroQol five dimensions questionnaire (EQ-5D) index value was 0.9. In total, 110 patients utilized health care for COPD in 2007, and this number increased to 179 in 2012. The total mean number of days used per person increased from 4.9 in 2007 to 7.8 in 2012. The total medical cost per person also increased from 248.8 US dollar (USD) in 2007 to 780.6 USD in 2013. A multiple linear regression revealed that age, lower body mass index, lower FEV1 (%), and lower EQ-5D score were significantly associated with medical costs. Conclusion Even in early COPD patients, some of them eventually progressed and utilized health care for COPD. PMID:28255237

  4. [Autism: An early neurodevelopmental disorder].

    PubMed

    Bonnet-Brilhault, F

    2017-04-01

    With approximately 67 million individuals affected worldwide, autism spectrum disorder (ASD) is the fastest growing neurodevelopmental disorder (United Nations, 2011), with a prevalence estimated to be 1/100. In France ASD affects approximately 600,000 individuals (from childhood to adulthood, half of whom are also mentally retarded), who thus have a major handicap in communication and in adapting to daily life, which leads autism to be recognized as a national public health priority. ASD is a neurodevelopmental disorder that affects several domains (i.e., socio-emotional, language, sensori-motor, executive functioning). These disorders are expressed early in life with an age of onset around 18 months. Despite evidence suggesting a strong genetic link with ASD, the genetic determinant remains unclear. The clinical picture is characterized by impairments in social interaction and communication and the presence of restrictive and repetitive behaviors (DSM-5, ICD-10). However, in addition to these two main dimensions there is significant comorbidity between ASD and other neurodevelopmental disorders such as attention deficit hyperactivity disorder or with genetic and medical conditions. One of the diagnostic features of ASD is its early emergence: symptoms must begin in early childhood for a diagnosis to be given. Due to brain plasticity, early interventions are essential to facilitate clinical improvement. Therefore, general practitioners and pediatricians are on the front line to detect early signs of ASD and to guide both medical explorations and early rehabilitation.

  5. Can Ovarian Cancer Be Found Early?

    MedlinePlus

    ... Ovarian Cancer Early Detection, Diagnosis, and Staging Can Ovarian Cancer Be Found Early? About 20% of ovarian cancers ... cancer in its earliest stage. Ways to find ovarian cancer early Regular women's health exams During a pelvic ...

  6. Generation of early Archean felsic volcanics and TTG gneisses through crustal melting, eastern Kaapvaal craton, southern Africa

    NASA Astrophysics Data System (ADS)

    Kröener, A.; Hoffmann, J.; Xie, H.; Wu, F.; Münker, C.; Hegner, E.; Wong, J.; Wan, Y.; Liu, D.

    2012-12-01

    crustal protolith, whereas some analyses suggest input from a juvenile source. Hf crustal model ages are 3.61-3.89 Ga and again imply a heterogeneous but predominantly crustal source. The oldest TTG gneisses of the AGC with zircon ages of 3.60-3.66 Ga occur in NW Swaziland. Whole-rock ɛNd(t)-values range from -2.0 to +0.9, and ɛHf(t)-values are -3.3 to +4.6. Hf-in-zircon isotopic data are similar to the BGB felsic rocks, and most analyses show negative ɛHf(t)-values, suggesting zircon derivation from an older crustal protolith, whereas only a few analyses suggest juvenile input. Hf crustal model ages are 3.79-4.13 Ga and again imply a heterogeneous source. Our data challenge the popular view that early Archaean TTGs and greenstones are principally of juvenile origin and formed in primitive arc or oceanic environments. We suggest extensive and continuous recycling of earliest-formed granitoid crust and mixing with juvenile material to produce successive generations of TTGs and associated felsic volcanic rocks in the eastern Kaapvaal craton.

  7. Developing and Exploiting a Unique Seismic Data Set from South African Gold Mines for Source Characterization and Wave Propagation

    DTIC Science & Technology

    2007-09-01

    the University of the Witwatersrand . RESEARCH ACCOMPLISHED Three complimentary data sets are being assembled in this project: (1) high...frequency in-mine seismic data from three mines along the northwestern edge of the Witwatersrand basin, (2) seismograms from mine events recorded at...Seismicity The Witwatersrand basin is part of a granite-greenstone complex constituting the basement of the Kaapvaal craton. The basement evolved

  8. Early Experience & Multisensory Perceptual Narrowing

    PubMed Central

    Lewkowicz, David J.

    2014-01-01

    Perceptual narrowing is a reflection of early experience and contributes in key ways to perceptual and cognitive development. In general, findings have shown that unisensory perceptual sensitivity in early infancy is broadly tuned such that young infants respond to, and discriminate, native as well as non-native sensory inputs, whereas older infants only respond to native inputs. Recently, my colleagues and I discovered that perceptual narrowing occurs at the multisensory processing level as well. The present article reviews this new evidence and puts it in the larger context of multisensory perceptual development and the role that perceptual experience plays in it. Together, the evidence on unisensory and multisensory narrowing shows that early experience shapes the emergence of perceptual specialization and expertise. PMID:24435505

  9. Early Literacy and Early Numeracy: The Value of Including Early Literacy Skills in the Prediction of Numeracy Development

    ERIC Educational Resources Information Center

    Purpura, David J.; Hume, Laura E.; Sims, Darcey M.; Lonigan, Cristopher J.

    2011-01-01

    The purpose of this study was to examine whether early literacy skills uniquely predict early numeracy skills development. During the first year of the study, 69 3- to 5-year-old preschoolers were assessed on the Preschool Early Numeracy Skills (PENS) test and the Test of Preschool Early Literacy Skills (TOPEL). Participants were assessed again a…

  10. Early recognition of growth abnormalities permitting early intervention

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Normal growth is a sign of good health. Monitoring for growth disturbances is fundamental to children's health care. Early detection and diagnosis of the causes of short stature allows management of underlying medical conditions, optimizing attainment of good health and normal adult height. This rev...

  11. The Early Diabetes Intervention Program--is early actually late?

    PubMed

    Bergman, Michael

    2014-11-01

    This Commentary briefly reviews the background of prediabetes including its definition and pathophysiology and describes as well the natural course of glycemic deterioration as it follows a continuum. Research efforts in identifying glucose and other biomarkers for the early detection of high-risk individuals are summarized.

  12. Early Learning: Program Quality in Early Childhood Education. Annotated Bibliography

    ERIC Educational Resources Information Center

    Hite, Jenny

    2014-01-01

    Overwhelmingly, research shows that program quality is a major determinant in the achievement gains for young children who participate in early education programs. Teacher quality, in particular, is closely related to positive educational outcomes for preschool participants. Research shows that children in programs whose lead and supporting…

  13. Belle II Early Physics Program

    NASA Astrophysics Data System (ADS)

    Stottler, Zachary; Belle Collaboration, II

    2017-01-01

    The Belle II experiment at the SuperKEKB collider is a major upgrade of the KEK `` B factory'' facility in Tsukuba, Japan. First beams are planned for early 2017 and first physics data will be recorded in the middle of 2018 during Phase 2 commissioning, while the Belle II detector is still missing its vertex detector system. In this talk we describe the physics program for this early data. The program will focus on bottomonium spectroscopy at different center-of-mass energies, in particular at the ϒ(3 S) and ϒ(6 S) resonances, amongst other energy points.

  14. Researching Early Childhood Education: European Perspectives.

    ERIC Educational Resources Information Center

    David, Tricia, Ed.

    At a time when crucial questions concerning the nature of early childhood and early childhood education are being increasingly examined worldwide, an exploration of the issues, priorities, and methodologies of research in early childhood education may provide valuable material for debate. This book focuses on research in early childhood education…

  15. Early Childhood Intervention in China

    ERIC Educational Resources Information Center

    Zheng, Yuzhu; Maude, Susan P.; Brotherson, Mary Jane

    2015-01-01

    With rapid economic development and increasing awareness of the importance of early childhood intervention (ECI), China is re-examining its social and educational practices for young children with disabilities. This re-examination may have a significant impact on young children with disabilities in China. It may also set an example for other…

  16. The Early Years: Integrating Design

    ERIC Educational Resources Information Center

    Ashbrook, Peggy; Nellor, Sue

    2015-01-01

    Engineering is such a common part of children's work in early childhood programs that teachers can simply look around the room to identify examples where students have engaged in engineering practices. This article presents a classroom activity that integrates engineering design by building on the everyday problems that young children encounter in…

  17. Maine: Early Head Start Initiatives

    ERIC Educational Resources Information Center

    Center for Law and Social Policy, Inc. (CLASP), 2012

    2012-01-01

    Maine has two initiatives that build on Early Head Start (EHS). The first initiative, Fund for a Healthy Maine, has since 2001 provided tobacco settlement money to existing Head Start and EHS programs to expand the number of children who receive full-day, full-year services. Local programs have the option of using these funds for EHS, depending on…

  18. Early Childhood Inclusion in Israel

    ERIC Educational Resources Information Center

    Al-Yagon, Michal; Aram, Dorit; Margalit, Malka

    2016-01-01

    This article describes conceptual aspects, current policies and practices, and research representing the Israeli perspective regarding early childhood inclusion (ECI) at preschool ages (3-6 years). We review legislative, historical, attitudinal, philosophical, practical, empirical, and cultural issues regarding ECI in Israel. Finally, we focus on…

  19. HPLC: Early and Recent Perspectives.

    ERIC Educational Resources Information Center

    Karger, Barry L.

    1997-01-01

    Provides a perspective on what it was like in the early days of high-performance liquid chromatography (HPLC) and several of the key developments. Focuses on the advances in HPLC generally, and more specifically for the biological sciences, that were necessary for the method to reach the preeminent stage of today. Contains 20 references. (JRH)

  20. Suicidal Behavior among Early Adolescents.

    ERIC Educational Resources Information Center

    Gover, F. Jill

    There is a great deal of concern about teenage suicide. This study obtained a prevalence rate of suicidal behaviors among non-psychiatric early adolescents (ages 11-16) and investigated personal and family variables that may characterize the young teenagers who report varying degrees of suicidal behavior. A self-report questionnaire was…

  1. Bullying in Early Educational Settings

    ERIC Educational Resources Information Center

    Kirves, Laura; Sajaniemi, Nina

    2012-01-01

    The aim of this research was to study the prevalence of bullying in early educational settings in Finnish kindergartens. In addition, the study investigated whether bullying in kindergartens differs from school bullying and what forms bullying takes among under-school-age children. Two kinds of data were collected for the study: data from a survey…

  2. Early Childhood Education. PREP-37.

    ERIC Educational Resources Information Center

    Chow, Stanley; And Others

    Programs that represent major curriculum development efforts in early childhood education are described as to goals and objectives, content and materials, classroom activities, parent involvement, professional and paraprofessional training, administrative requirements and costs, program development and evaluation, and program history and present…

  3. Choreography of early thalamocortical development.

    PubMed

    Molnár, Zoltán; Higashi, Shuji; López-Bendito, Guillermina

    2003-06-01

    Thalamic axons, which carry most of the information from the sensory environment, are amongst the first projections to reach the cerebral cortex during embryonic development. It has been proposed that the scaffold of early generated cells in the ventral thalamus, internal capsule and preplate play a pivotal role in their deployment through sharp gene expression boundaries. These ideas were recently evaluated in various strains of mutant mice. In Tbr1, Gbx2, Pax6 KO both thalamic and corticofugal projections fail to traverse the striatocortical junction. In both Emx2 and Pax6 KO brains, the misrouted thalamic afferents are accompanied by displacements of the pioneering projections from the internal capsule. Regardless of their altered route, thalamic afferents in the reeler and L1 KO mice seem to be able to redistribute themselves on the cortical sheet and establish normal periphery-related representation in the somatosensory cortex. Early neural activity delivered through the thalamic projections is thought to be involved in the realignment process of thalamic axons at the time of their accumulation in the subplate layer. However, axonal growth and the early topographic arrangement of thalamocortical fiber pathways appear normal in the Snap25 KO, where action potential mediated synaptic vesicle release is disrupted. We therefore suggest that intercellular communication mediated by constitutive secretion of transmitters or growth factors might play a dominant role during early thalamocortical development.

  4. Early and Late Retirement Exits

    ERIC Educational Resources Information Center

    Brougham, Ruby R.; Walsh, David A.

    2009-01-01

    The current study proposes that personal need fulfillment (relatedness, generativity, identity, growth, and finances) predicts early and late retirement intentions. The personal needs of 160 full-time older employees were measured by personal goals, job satisfactions, job characteristics, and intrinsic motivation. Results suggest that the personal…

  5. Early Prevention of School Failure.

    ERIC Educational Resources Information Center

    Anderson, Kent C.

    The Early Prevention of School Failure (EPSF) program developed by Dr. Luceille Werner is presented. The program is designed to identify and remediate developmental deficiencies of four-, five-, and six-year-old children and has been accepted in the National Diffusion Network as a nationally validated program. The main program components are…

  6. Early Writing: A Developmental Approach.

    ERIC Educational Resources Information Center

    Goetz, Elizabeth; And Others

    This document consists of four papers on the acquisition of writing skills by young children. The first paper provides a historical and developmental perspective on early writing. Children's development of manual dexterity is briefly overviewed and aspects of the educational approaches of Pestalozzi, Montessori, Chomsky, Rogers and Ashton-Warner…

  7. Physical Education in Early Childhood

    ERIC Educational Resources Information Center

    Stork, Steve; Sanders, Stephen W.

    2008-01-01

    This article examines the incidence and quality of physical activity instruction during early childhood. Although the positive effect of physical activity on the cognitive, social, and physical development of young children is generally acknowledged, there is little emphasis nationally on ensuring appropriate physical educational experiences…

  8. The Inquiring Eye: Early Modernism.

    ERIC Educational Resources Information Center

    Wisotzki, Paula

    This teaching guide introduces students to early 20th century European and American art. Through critically viewing and discussing art images and participating in related activities, students are encouraged to explore the historical and cultural context within which the art was created. This guide includes background information and an overview…

  9. Early Children's Literature and Aging

    ERIC Educational Resources Information Center

    McGuire, Sandra L.

    2016-01-01

    Increased longevity is a worldwide phenomenon placing emphasis on the need for preparation for life's later years. Today's children will be the older adults of tomorrow. A resource that can help to educate them about aging and prepare them for the long life ahead is early children's literature (Preschool-Primary). This literature can provide…

  10. Regional Early Childhood Policy Review

    ERIC Educational Resources Information Center

    Evans, Judith

    2008-01-01

    The UNESCO-UNICEF joint regional policy review project was launched in September 2006 with the aim to support the countries of Asia-Pacific region in meeting the first goal of Education For All (EFA) on Early Childhood Care and Education (ECCE) by identifying, documenting and sharing good practices as well as constraints and challenges in early…

  11. Language in Early Childhood Education.

    ERIC Educational Resources Information Center

    Cazden, Courtney B., Ed.

    Eight articles about oral language education for preschool children are presented. They are: (1) a point of view on oral language education--"Suggestions from Studies of Early Language Acquisition,""Language Programs for Young Children: Notes from England and Wales," and "The Issue of Structure," by Courtney Cazden; (2) suggestions for curriculum…

  12. Early Child Care in Hungary.

    ERIC Educational Resources Information Center

    Hermann, Alice; Komlosi, Sandor

    The theoretical conceptions of the child and the socialization processes involved in a socialist pedagogical theory are described in this monograph on early child care in Hungary. In emphasizing the partnership between family and state in the care of the young child, this book traces the central role played by government planning in the midst of…

  13. Drug Prevention for Early Childhood.

    ERIC Educational Resources Information Center

    American Council for Drug Education, Rockville, MD.

    Noting that attitudes and habits formed very early in life can have an impact on a child's decision to use drugs or remain drug free later in life, this packet of materials introduces preschool children to the important skills and attitudes they will need to avoid drug use later on. None of the materials provided for children directly addresses…

  14. Early Childhood Inclusion in Australia

    ERIC Educational Resources Information Center

    Kemp, Coral R.

    2016-01-01

    From the introduction of early intervention services in Australian in the mid-1970s, the families of children with intellectual and multiple disabilities have been encouraged to enroll their children in local preschools and childcare centers. Children with disabilities have also accessed a range of alternatives to full inclusion, such as reverse…

  15. Early Marriage: A Propositional Formulation

    ERIC Educational Resources Information Center

    Bartz, Karen Winch; Nye, F. Ivan

    1970-01-01

    Consequences of early marriage are reviewed and stated as three propositions involving social class placement following marriage, divorce rate, and negative affect. Three derived propositions are obtained from these. Theoretical family propositions are related to exchange theory and shown to be special cases of it. Presented at American…

  16. Handbook of Early Literacy Research.

    ERIC Educational Resources Information Center

    Neuman, Susan B., Ed.; Dickinson, David K., Ed.

    This handbook brings together leading authorities to provide a comprehensive account of current knowledge in the early literacy field. The chapters are: (1)"Introduction" (Neuman and Dickinson); (2) "Emergent Literacy: Development from Prereaders to Readers" (Whitehurst and Lonigan); (3) "A Sociocultural Perspective on…

  17. The Early Childhood Coaching Handbook

    ERIC Educational Resources Information Center

    Rush, Dathan D.; Shelden, M'Lisa L.

    2011-01-01

    Evidence-based and highly effective, "coaching" helps early childhood practitioners support other professionals and families as they enhance existing knowledge, develop new skills, and promote healthy development of young children. This hands-on guide shows professionals how to conduct skillful coaching in any setting--home, school, or community.…

  18. Early Childhood Educator's Nutrition Handbook.

    ERIC Educational Resources Information Center

    Olson, Christine; And Others

    This nutrition handbook is designed to provide enough information on nutrition and food habits to enable early childhood educators to add a nutrition dimension to children's learning activities. Topics covered are the role of nutrition in growth during the preschool years; nutrients and their functions; selecting a healthy diet; common nutritional…

  19. Early Childhood: Child, Teacher, Parent

    ERIC Educational Resources Information Center

    Baroody, Christie

    2006-01-01

    The field of early childhood holds promising keys to unlocking many of the mysteries in learning. Educators in the field, given the right tools, have the potential to have a profound impact on the long-term success of their students. The design of this curriculum comes directly out of the incredible possibilities set in motion while exploring…

  20. Early Childhood Assessment: Recent Advances.

    ERIC Educational Resources Information Center

    Shaughnessy, Michael F.; Greathouse, Dan

    As concern about the developmental progress of preschoolers has increased, the number of assessment instruments available has expanded. This paper reviews recent advances in early childhood assessment and evaluation, and describes several screening and assessment instruments. Varying information is presented for each test, but may include a…

  1. School Starters' Early Structure Sense

    ERIC Educational Resources Information Center

    Lüken, Miriam M.

    2012-01-01

    I analyse low and high achieving children's competences regarding pattern and structure at the beginning of formal schooling comparatively. The aim is to evaluate the range of school starters' early structure sense. The results suggest overall high pre-instructional competences which, however, differ strongly between the mathematical high and low…

  2. Boys' Bodies in Early Childhood

    ERIC Educational Resources Information Center

    Drummond, Murray

    2012-01-01

    This paper is based on qualitative research data from a project investigating early childhood boys' constructions of masculinities in relation to sport, health and the body. The focus group data, with 33 boys, has been collected in each of the boys' first three years at school. It is part of the data that will be collected over eight years with…

  3. The Climate of Early Mars

    NASA Astrophysics Data System (ADS)

    Wordsworth, Robin D.

    2016-06-01

    The nature of the early martian climate is one of the major unanswered questions of planetary science. Key challenges remain, but a new wave of orbital and in situ observations and improvements in climate modeling have led to significant advances over the past decade. Multiple lines of geologic evidence now point to an episodically warm surface during the late Noachian and early Hesperian periods 3-4 Ga. The low solar flux received by Mars in its first billion years and inefficiency of plausible greenhouse gases such as CO2 mean that the steady-state early martian climate was likely cold. A denser CO2 atmosphere would have caused adiabatic cooling of the surface and hence migration of water ice to the higher-altitude equatorial and southern regions of the planet. Transient warming caused melting of snow and ice deposits and a temporarily active hydrological cycle, leading to erosion of the valley networks and other fluvial features. Precise details of the warming mechanisms remain unclear, but impacts, volcanism, and orbital forcing all likely played an important role. The lack of evidence for glaciation across much of Mars's ancient terrain suggests the late Noachian surface water inventory was not sufficient to sustain a northern ocean. Though mainly inhospitable on the surface, early Mars may nonetheless have presented significant opportunities for the development of microbial life.

  4. Early Signs of Entrepreneurial Giftedness

    ERIC Educational Resources Information Center

    Shavinina, Larisa V.

    2008-01-01

    Although successful entrepreneurship is important for the economic prosperity of any society, one should acknowledge that entrepreneurial giftedness is terra incognita from a research viewpoint. This article analyzes early manifestations of entrepreneurial giftedness in the cases of Richard Branson, Michael Dell, and Bill Gates and thus opens a…

  5. Minnesota: Early Head Start Initiatiive

    ERIC Educational Resources Information Center

    Center for Law and Social Policy, Inc. (CLASP), 2012

    2012-01-01

    Minnesota provides supplemental state funding to existing federal Head Start and Early Head Start (EHS) grantees to increase their capacity to serve additional infants, toddlers, and pregnant women. The initiative was started in 1997 when the state legislature earmarked $1 million of the general state Head Start supplemental funds for children…

  6. The Early Years: "Life" Science

    ERIC Educational Resources Information Center

    Ashbrook, Peggy

    2013-01-01

    Talking about death as part of a life cycle is often ignored or spoken about in hushed tones in early childhood. Books with "life cycle" in the title often do not include the death of the living organism in the information about the cycle. The concept of a complete life cycle does not appear in "A Framework for K-12 Science…

  7. Early Components to Childhood Literacy.

    ERIC Educational Resources Information Center

    Crown, Sid

    Within the fundamental context of "how children learn to read," attention is drawn towards an understanding of the "components" that are necessary for the child to move from oral language to early literacy. Looking at this transition requires the educator to consider whether literacy can develop as naturally for the child as speaking, or if not,…

  8. Early Childhood Inclusion in Croatia

    ERIC Educational Resources Information Center

    Ljubešic, Marta; Šimleša, Sanja

    2016-01-01

    This article explains early childhood inclusion in Croatia from its beginnings up to challenges in current policy and practice. The first preschool education for children with disabilities dates back to the 1980s and was provided in special institutions. In the last 10 years, mainstream kindergartens have been enrolling children with disabilities…

  9. Assessment in Early Childhood Education.

    ERIC Educational Resources Information Center

    Paget, Kathleen D.

    1985-01-01

    A review of assessment in early childhood education focuses on historical highlights, issues in complying with P.L. 94-142, current practices (multiscore, mulitdomain, and multimeasure processes), critical issues (specifically, the reliability and validity of instruments and procedures used), and recommended practices. (CL)

  10. Early Prediction of Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Collins, D.; Feynman, J.

    2000-01-01

    A detailed conceptual design has been developed for a mission and microspacecraft that can provide information needed to answer key questions about the physics of space weather and also both provide and validate a system for early warning of hazardous space weather.

  11. EARLY TRAINING PROJECT. INTERIM REPORT.

    ERIC Educational Resources Information Center

    GRAY, SUSAN W.; KLAUS, RUPERT A.

    THE EARLY TRAINING PROJECT ATTEMPTED TO IMPROVE THE INTELLECTUAL FUNCTIONING AND PERSONAL ADJUSTMENT OF CULTURALLY DISADVANTAGED CHILDREN THROUGH SPECIAL EXPERIENCES IN THE 15- OR 24-MONTHS PRECEDING FIRST GRADE AND IN THE FIRST YEAR OF SCHOOL. THE PROCEDURES OF THE PROJECT CONSISTED OF TWO TRAINING SEQUENCES. THE FIRST SEQUENCE INVOLVED TWO…

  12. Early Childhood Education in Cuba.

    ERIC Educational Resources Information Center

    Miller, Susan A.

    2002-01-01

    Describes the four levels of the early childhood education system in Cuba. Includes information on home visit programs for new parents, child care programs, preschool programs, programs for 5-year-olds, and primary school programs. Emphasizes that parents, relatives, teachers, and the larger community share the responsibility of educating young…

  13. Early Intervention Approaches. Chapter 9.

    ERIC Educational Resources Information Center

    1996

    This collection of papers presented at a 1996 conference on children's mental health focuses on early intervention approaches. Papers have the following titles and authors: (1) "Child Maltreatment and Prenatal Exposure to Alcohol and Other Drugs: Some Preliminary Findings" (Patrick A. Curtis and Mary Wood Schneider); (2) "Evaluation…

  14. Handbook of Early Childhood Education

    ERIC Educational Resources Information Center

    Pianta, Robert C., Ed.

    2012-01-01

    Comprehensive and authoritative, this forward-thinking book reviews the breadth of current knowledge about early education and identifies important priorities for practice and policy. Robert C. Pianta and his associates bring together foremost experts to examine what works in promoting all children's school readiness and social-emotional…

  15. Do Schools Begin Too Early?

    ERIC Educational Resources Information Center

    Edwards, Finley

    2012-01-01

    School start times vary considerably, both across the nation and within individual communities, with some schools beginning earlier than 7:30 a.m. and others after 9:00 a.m. Proponents of later start times, who have received considerable media attention in recent years, argue that many students who have to wake up early for school do not get…

  16. ABCs of Early Mathematics Experiences

    ERIC Educational Resources Information Center

    Hensen, Laurie E.

    2005-01-01

    Children begin to develop mathematical thinking before they enter school. Art, baking, playing with blocks, counting numbers, games, puzzles, singing, playing with pretend money, water play all these early mathematical experiences help the children to learn in the elementary school years.

  17. Early Learning Theories Made Visible

    ERIC Educational Resources Information Center

    Beloglovsky, Miriam; Daly, Lisa

    2015-01-01

    Go beyond reading about early learning theories and see what they look like in action in modern programs and teacher practices. With classroom vignettes and colorful photographs, this book makes the works of Jean Piaget, Erik Erikson, Lev Vygotsky, Abraham Maslow, John Dewey, Howard Gardner, and Louise Derman-Sparks visible, accessible, and easier…

  18. Documentary Elements in Early Films.

    ERIC Educational Resources Information Center

    Sanderson, Richard A.

    Focusing on documentary elements, this study examines the film content and film techniques of 681 motion pictures produced in the United States prior to 1904. Analysis of films by type, subject matter, and trends in subject matter shows that one-third of the early films are documentary in type and three-fourths of the films use subject matter of a…

  19. FUNdamental Movement in Early Childhood.

    ERIC Educational Resources Information Center

    Campbell, Linley

    2001-01-01

    Noting that the development of fundamental movement skills is basic to children's motor development, this booklet provides a guide for early childhood educators in planning movement experiences for children between 4 and 8 years. The booklet introduces a wide variety of appropriate practices to promote movement skill acquisition and increased…

  20. Freshwater Fossil Pearls from the Nihewan Basin, Early Early Pleistocene

    PubMed Central

    Li, Su-Ping; Yao, Pei-Yi; Li, Jin-Feng; Ferguson, David Kay; Min, Long-Rui; Chi, Zhen-Qing; Wang, Yong; Yao, Jian-Xin; Sha, Jin-Geng

    2016-01-01

    Fossil blister pearls attached to the shells of an Anodonta mollusk from China, early Early Pleistocene, are reported here for the first time. The pearls were investigated in detail using a variety of methods. Micro-CT scanning of the fossil pearls was carried out to discover the inner structure and the pearl nucleus. Using CTAn software, changes in the gray levels of the biggest pearl, which reflect the changing density of the material, were investigated. The results provide us with some clues on how these pearls were formed. Sand grains, shell debris or material with a similar density could have stimulated the development of these pearls. X-ray diffraction analysis of one fossil pearl and the shell to which it was attached reveals that only aragonite exists in both samples. The internal structures of our fossil shells and pearls were investigated using a Scanning Electron Microscope. These investigations throw some light on pearl development in the past. PMID:27760154

  1. Famines in Africa: is early warning early enough?

    PubMed Central

    Kim, Jeeyon Janet; Guha-Sapir, Debarati

    2012-01-01

    Following the second Sahelian famine in 1984–1985, major investments were made to establish Early Warning Systems. These systems help to ensure that timely warnings and vulnerability information are available to decision makers to anticipate and avert food crises. In the recent crisis in the Horn of Africa, alarming levels of acute malnutrition were documented from March 2010, and by August 2010, an impending food crisis was forecast. Despite these measures, the situation remained unrecognised, and further deteriorated causing malnutrition levels to grow in severity and scope. By the time the United Nations officially declared famine on 20 July 2011, and the humanitarian community sluggishly went into response mode, levels of malnutrition and mortality exceeded catastrophic levels. At this time, an estimated 11 million people were in desperate and immediate need for food. With warnings of food crises in the Sahel, South Sudan, and forecast of the drought returning to the Horn, there is an immediate need to institutionalize change in the health response during humanitarian emergencies. Early warning systems are only effective if they trigger an early response. PMID:22745628

  2. "How Early Is Early?" or "How Late Is Late?": Thinking through Some Issues in Early Intervention

    ERIC Educational Resources Information Center

    Mercieca, Daniela; Mercieca, Duncan P.

    2014-01-01

    Early intervention comes in-between the lives of children, families and teachers. This article uses part of a report written by an educational psychologist about a little girl to question the nature of intervention through Rancière's writings. As children and parents are seen as put into the position of inadequacy, they require such…

  3. Abnormal early cleavage events predict early embryo demise: sperm oxidative stress and early abnormal cleavage.

    PubMed

    Burruel, Victoria; Klooster, Katie; Barker, Christopher M; Pera, Renee Reijo; Meyers, Stuart

    2014-10-13

    Human embryos resulting from abnormal early cleavage can result in aneuploidy and failure to develop normally to the blastocyst stage. The nature of paternal influence on early embryo development has not been directly demonstrated although many studies have suggested effects from spermatozoal chromatin packaging, DNA damage, centriolar and mitotic spindle integrity, and plasma membrane integrity. The goal of this study was to determine whether early developmental events were affected by oxidative damage to the fertilizing sperm. Survival analysis was used to compare patterns of blastocyst formation based on P2 duration. Kaplan-Meier survival curves demonstrate that relatively few embryos with short (<1 hr) P2 times reached blastocysts, and the two curves diverged beginning on day 4, with nearly all of the embryos with longer P2 times reaching blastocysts by day 6 (p < .01). We determined that duration of the 2nd to 3rd mitoses were sensitive periods in the presence of spermatozoal oxidative stress. Embryos that displayed either too long or too short cytokineses demonstrated an increased failure to reach blastocyst stage and therefore survive for further development. Although paternal-derived gene expression occurs later in development, this study suggests a specific role in early mitosis that is highly influenced by paternal factors.

  4. A Study of the Relationship between Early Childhood Program Attributes and Early Childhood Reading Achievement

    ERIC Educational Resources Information Center

    Washington, Novella M.

    2012-01-01

    This quantitative correlational study focuses on the relationship between early childhood program attributes and early childhood reading success. Data will be gathered from early childhood sites with grades prekindergarten through second grade in which early childhood program attributes exist and early childhood reading is measured by the…

  5. Early detection of tubular dysfunction.

    PubMed

    Piscator, M

    1991-11-01

    The determination of low-molecular-weight proteins in urine as a tool for early detection of damage to the proximal tubules is briefly discussed. Beta 2-microglobulin, retinol-binding protein and alpha 1-microglobulin are at present the most widely used markers for tubular dysfunction. The determination of beta 2-microglobulin has earlier been the method of choice, but due to its instability at low pH there are certain disadvantages. Available data indicate that alpha 1-microglobulin may replace beta 2-microglobulin for screening purposes. The low-molecular-weight proteins are at present the best markers for early detection of tubular dysfunction; other constituents are not as well suited for this, even if the determination of urine enzymes has its supporters.

  6. Early chiropractic education in Oregon

    PubMed Central

    Keating, Joseph C

    2002-01-01

    Chiropractic education in the northwestern United States has its origins in the Marsh School & Cure in 1904. Most of the early schools were located in Portland, Oregon, including the D.D. Palmer College of Chiropractic (1908-1910), and several of these had merged by 1912 or 1913 to form the Pacific Chiropractic College, forerunner of today's Western States College. The latter was organized as a non-profit institution during the Great Depression, and struggled not only to survive but to create a higher standard. The early broad-scope of chiropractic training in the state probably encouraged the liberal scope of practice enjoyed in Oregon to this day. ImagesFigure 2Figure 3Figure 4Figure 6Figure 7Figure 8Figure 9Figure 11Figure 12Figure 13Figure 14Figure 15Figure 16Figure 18Figure 19Figure 20Figure 21Figure 22Figure 24

  7. Shocks in the Early Universe

    NASA Astrophysics Data System (ADS)

    Pen, Ue-Li; Turok, Neil

    2016-09-01

    We point out a surprising consequence of the usually assumed initial conditions for cosmological perturbations. Namely, a spectrum of Gaussian, linear, adiabatic, scalar, growing mode perturbations not only creates acoustic oscillations of the kind observed on very large scales today, it also leads to the production of shocks in the radiation fluid of the very early Universe. Shocks cause departures from local thermal equilibrium as well as create vorticity and gravitational waves. For a scale-invariant spectrum and standard model physics, shocks form for temperatures 1 GeV early as 10-30 sec after the big bang.

  8. Early Detection of Huntington Disease

    PubMed Central

    Paulsen, Jane S.

    2013-01-01

    SUMMARY Huntington disease (HD) is a devastating illness, although its autosomal dominant genetic transmission allows a unique opportunity to study apparently healthy individuals before manifest disease. Attempts to study early disease are not unique in neurology (e.g., Mild Cognitive Impairment, Vascular Cognitive Impairment), but studying otherwise-healthy appearing individuals who will go on with nearly 99% certainty to manifest the symptoms of brain disease does provide distinct but valuable information about the true natural history of the disease. The field has witnessed an explosion of research examining possible early indicators of HD during what is now referred to as the “prodrome” of HD. A NIH study in its ninth year (PREDICT-HD) has offered a glimpse into the transition from an apparently healthy state to an obviously diseased state, and can serve as a model for many other genetic diseases, both neurological and non-neurological. PMID:24348095

  9. Rethinking early Earth phosphorus geochemistry

    PubMed Central

    Pasek, Matthew A.

    2008-01-01

    Phosphorus is a key biologic element, and a prebiotic pathway leading to its incorporation into biomolecules has been difficult to ascertain. Most potentially prebiotic phosphorylation reactions have relied on orthophosphate as the source of phosphorus. It is suggested here that the geochemistry of phosphorus on the early Earth was instead controlled by reduced oxidation state phosphorus compounds such as phosphite (HPO32−), which are more soluble and reactive than orthophosphates. This reduced oxidation state phosphorus originated from extraterrestrial material that fell during the heavy bombardment period or was produced during impacts, and persisted in the mildly reducing atmosphere. This alternate view of early Earth phosphorus geochemistry provides an unexplored route to the formation of pertinent prebiotic phosphorus compounds, suggests a facile reaction pathway to condensed phosphates, and is consistent with the biochemical usage of reduced oxidation state phosphorus compounds in life today. Possible studies are suggested that may detect reduced oxidation state phosphorus compounds in ancient Archean rocks. PMID:18195373

  10. Shocks in the Early Universe.

    PubMed

    Pen, Ue-Li; Turok, Neil

    2016-09-23

    We point out a surprising consequence of the usually assumed initial conditions for cosmological perturbations. Namely, a spectrum of Gaussian, linear, adiabatic, scalar, growing mode perturbations not only creates acoustic oscillations of the kind observed on very large scales today, it also leads to the production of shocks in the radiation fluid of the very early Universe. Shocks cause departures from local thermal equilibrium as well as create vorticity and gravitational waves. For a scale-invariant spectrum and standard model physics, shocks form for temperatures 1  GeVearly as 10^{-30}  sec after the big bang.

  11. The early days of incineration

    SciTech Connect

    Valenti, M.

    1995-05-01

    Landfills reaching capacity, beaches fouled with trash, neighborhood residents protesting waste disposal sites in their backyards, and municipalities forced to recycle. Sound familiar? These issues might have been taken from today`s headlines, but they were also problems facing mechanical engineers a century ago. Conditions such as these were what led engineers to design the first incinerators for reducing the volume of municipal garbage, as well as for producing heat and electricity. The paper discusses these early days.

  12. Early BHs: simulations and observations

    NASA Astrophysics Data System (ADS)

    Cappelluti, Nico; di-Matteo, Tiziana; Schawinski, Kevin; Fragos, Tassos

    We report recent investigations in the field of Early Black Holes. We summarize recent theoretical and observational efforts to understand how Black Holes formed and eventually evolved into Super Massive Black Holes at high-z. This paper makes use of state of the art computer simulations and multiwavelength surveys. Although non conclusive, we present results and hypothesis that pose exciting challenges to modern astrophysics and to future facilities.

  13. Early Childhood Education in Portugal.

    ERIC Educational Resources Information Center

    Vasconcelos, Teresa

    This booklet provides an overview of the policy and status of early childhood education in Portugal and includes the text of Law 5/97, the Framework Law for Pre-School Education, as well as the Curriculum Guidelines for Pre-School Education adopted by Portugal's government. Two of Law 5/97's nine main goals are: (1) to promote the child's personal…

  14. Early perceptions of an epidemic.

    PubMed

    Anderson, Warwick H

    2008-11-27

    This article surveys some descriptions of the Fore people made on early contact in the 1950s by patrol officers, social anthropologists and medical doctors. Sorcery accusations and cannibalism initially impressed these outside observers, though gradually they came to realize that a strange and fatal condition called kuru was a major affliction of the Fore, especially women and children. Fore attributed kuru to sorcery, anthropologists speculated on psychosomatic causes and medical officers began to wonder if it was a mysterious encephalitis.

  15. Early steps in neural development.

    PubMed

    Callebaut, Marc; Van Nueten, Emmy; Van Passel, Hanalie; Harrisson, Fernand; Bortier, Hilde

    2006-07-01

    We studied early neurulation events in vitro by transplanting quail Hensen's node, central prenodal regions (before the nodus as such develops), or upper layer parts of it on the not yet definitively committed upper layer of chicken anti-sickle regions (of unincubated blastoderms), eventually associated with central blastoderm fragments. We could demonstrate by this quail-chicken chimera technique that after the appearance of a pronounced thickening of the chicken upper layer by the early inductive effect of neighboring endophyll, a floor plate forms by insertion of Hensen's node-derived quail cells into the median part of the groove. This favors, at an early stage, the floor plate "allocation" model that postulates a common origin for notochord and median floor plate cells from the vertebrate's secondary major organizer (Hensen's node in this case). A comparison is made with results obtained after transplantation of similar Hensen's nodes in isolated chicken endophyll walls or with previously obtained results after the use of the grafting procedure in the endophyll walls of whole chicken blastoderms.

  16. The early eukaryotic fossil record.

    PubMed

    Javaux, Emmanuelle J

    2007-01-01

    The Precambrian era records the evolution of the domain Eucarya. Although the taxonomy of fossils is often impossible to resolve beyond the level of domain, their morphology and chemistry indicate the evolution of major biological innovations. The late Archean record for eukaryotes is limited to trace amounts of biomarkers. Morphological evidence appears in late Paleoproterozoic and early Mesoproterozoic (1800-1300 Ma) rocks. The moderate diversity of preservable eukaryotic organisms includes cell walls without surface ornament (but with complex ultrastructure), with regularly distributed surface ornamentation, and with irregularly or regularly arranged processes. Collectively, these fossils suggest that eukaryotes with flexible membranes and cytoskeletons existed in mid-Proterozoic oceans. The late Mesoproterozoic-early Neoproterozoic (1300-750 Ma) is a time of diversification and evolution when direct evidence for important biological innovations occurs in the fossil record such as multicellularity, sex, photosynthesis, biomineralization, predation, and heterotrophy. Members of extant clades can be recognized and include bangiophyte red algae, xanthophyte algae, cladophorale green algae, euglyphid, lobose, and filose amoebae and possible fungi. In the late Neoproterozoic, besides more diversification of ornamented fossils, florideophyte red algae and brown algae diversify, and animals take the stage. The record of biological innovations documented by the fossils shows that eukaryotes had evolved most cytological and molecular complexities very early in the Proterozoic but environmental conditions delayed their diversification within clades until oxygen level and predation pressure increased significantly.

  17. Oxygen and Early Animal Evolution

    NASA Astrophysics Data System (ADS)

    Xiao, S.

    2012-12-01

    It is often hypothesized that the rise of animals was triggered by an increase in O2 levels in the atmosphere and oceans. However, this hypothesis is remarkably difficult to test, because the timing of animal divergences is poorly resolved, the physiology of early animals is often unknown, estimates of past pO2 levels come with large error bars, and causal relationships between oxygenation and animal evolution are difficult to establish. Nonetheless, existing phylogenetic, paleontological, and geochemical data indicate that the evolution of macroscopic animals and motile macrometazoans with energetically expensive lifestyles may be temporally coupled with ocean oxygenation events in the Ediacaran Period. Thus, it is plausible that ocean oxygenation may have been a limiting factor in the early evolution of macroscopic, complex, and metabolically aggressive animals (particularly bilaterian animals). However, ocean oxygenation and animal evolution were likely engaged in two-way interactions: Ediacaran oxygenation may have initially lifted a physiological barrier for the evolution of animal size, motility, and active lifestyles, but subsequent animal diversification in the Paleozoic may have also changed oceanic redox structures. Viewed in a broader context, the early evolutionary history of animals was contingent upon a series of events, including genetic preparation (developmental genetics), environmental facilitation (oceanic oxygenation), and ecological escalation (Cambrian explosion), but the rise of animals to ecological importance also had important geobiological impacts on oceanic redox structures, sedimentary fabrics, and global geochemical cycles.

  18. Early diagnosis of lung cancer

    NASA Astrophysics Data System (ADS)

    Saccomanno, Geno; Bechtel, Joel J.

    1991-06-01

    Lung cancer remains the leading cause of death in the United States. Although the incidence of cigarette smoking is decreasing in the United States it appears to be increasing worldwide. The five-year survival rate has not improved in cases with advanced disease, but several articles have indicated that survival can be improved in cases diagnosed early by sputum cytology and chest x-ray. In cases diagnosed while the lesion is in the in-situ stage or measures less than 1 cm in diameter, surgical excision and/or radiation therapy improves survival; therefore, the early diagnosis of high-risk patients should be vigorously pursued. A recent study at a community hospital in Grand Junction, Colorado, presented 45 lung cancer cases diagnosed with positive sputum cytology and negative chest x-ray, and indicates that early diagnosis does improve survival. This study has been conducted during the past six years; 16 cases have survived three years and six cases show five-year survival.

  19. The zebrafish early arrest mutants.

    PubMed

    Kane, D A; Maischein, H M; Brand, M; van Eeden, F J; Furutani-Seiki, M; Granato, M; Haffter, P; Hammerschmidt, M; Heisenberg, C P; Jiang, Y J; Kelsh, R N; Mullins, M C; Odenthal, J; Warga, R M; Nüsslein-Volhard, C

    1996-12-01

    This report describes mutants of the zebrafish having phenotypes causing a general arrest in early morphogenesis. These mutants identify a group of loci making up about 20% of the loci identified by mutants with visible morphological phenotypes within the first day of development. There are 12 Class I mutants, which fall into 5 complementation groups and have cells that lyse before morphological defects are observed. Mutants at three loci, speed bump, ogre and zombie, display abnormal nuclei. The 8 Class II mutants, which fall into 6 complementation groups, arrest development before cell lysis is observed. These mutants seemingly stop development in the late segmentation stages, and maintain a body shape similar to a 20 hour embryo. Mutations in speed bump, ogre, zombie, specter, poltergeist and troll were tested for cell lethality by transplanting mutant cells into wild-type hosts. With poltergeist, transplanted mutant cells all survive. The remainder of the mutants tested were autonomously but conditionally lethal: mutant cells, most of which lyse, sometimes survive to become notochord, muscles, or, in rare cases, large neurons, all cell types which become postmitotic in the gastrula. Some of the genes of the early arrest group may be necessary for progression though the cell cycle; if so, the survival of early differentiating cells may be based on having their terminal mitosis before the zygotic requirement for these genes.

  20. Early Time Points Perfusion Imaging

    PubMed Central

    Kwong, Kenneth K.; Reese, Timothy G.; Nelissen, Koen; Wu, Ona; Chan, Suk-Tak; Benner, Thomas; Mandeville, Joseph B.; Foley, Mary; Vanduffel, Wim; Chesler, David A.

    2010-01-01

    The aim was to investigate the feasibility of making relative cerebral blood flow (rCBF) maps from MR images acquired with short TR by measuring the initial arrival amount of Gd-DTPA evaluated within a time window before any contrast agent has a chance to leave the tissue. We named this rCBF measurement technique utilizing the early data points of the Gd-DTPA bolus the “early time points” method (ET), based on the hypothesis that early time point signals were proportional to rCBF. Simulation data were used successfully to examine the ideal behavior of ET while monkey’s MRI results offered encouraging support to the utility of ET for rCBF calculation. A better brain coverage for ET could be obtained by applying the Simultaneous Echo Refocusing (SER) EPI technique. A recipe to run ET was presented, with attention paid to the noise problem around the time of arrival (TOA) of the contrast agent. PMID:20851196

  1. Early Childhood Special Education and Early Intervention Personnel Preparation Standards of the Division for Early Childhood: Field Validation

    ERIC Educational Resources Information Center

    Cochran, Deborah C.; Gallagher, Peggy A.; Stayton, Vicki D.; Dinnebeil, Laurie A.; Lifter, Karin; Chandler, Lynette K.; Christensen, Kimberly A.

    2012-01-01

    Results of the field validation survey of the revised initial and new advanced Council for Exceptional Children (CEC) Division for Early Childhood (DEC) early childhood special education (ECSE)/early intervention (EI) personnel standards are presented. Personnel standards are used as part of educational accountability systems and in teacher…

  2. Comment on "Zircon thermometer reveals minimum melting conditions on earliest Earth" I.

    PubMed

    Glikson, Andrew

    2006-02-10

    Watson and Harrison (Reports, 6 May 2005, p. 841) proposed a model for early Earth magmatism based on crystallization temperatures of Hadean zircons. However, detrital zircon populations are skewed relative to the composition of their source terrains, Archaean isotopic and geochemical mantle signatures preclude reincorporation of Hadean continental crust into the early mantle, and the effects of early impacts should be considered.

  3. Detrital zircon U-Pb geochronology and whole-rock Nd-isotope constraints on sediment provenance in the Neoproterozoic Sergipano orogen, Brazil: From early passive margins to late foreland basins

    NASA Astrophysics Data System (ADS)

    Oliveira, E. P.; McNaughton, N. J.; Windley, B. F.; Carvalho, M. J.; Nascimento, R. S.

    2015-11-01

    SHRIMP U-Pb detrital zircon geochronology and depleted-mantle Nd-model ages of clastic rocks were combined to understand the sediment provenance in the Neoproterozoic Sergipano Belt. The Sergipano is the main orogenic belt between the Borborema province and the São Francisco Craton, eastern South America; it is divisible into several lithostratigraphic domains from North to South: Canindé, Poço Redondo-Marancó, Macururé, Vaza Barris, and Estância. Nd model ages (TDM) and detrital zircon U-Pb SHRIMP geochronology indicate that the protoliths of clastic metasedimentary rocks from the Marancó and Macururé domains were mostly derived from eroded late Mesoproterozoic to early Neoproterozoic rocks (1000-900 Ma), whereas detritus of similar rocks from the Canindé domain came from a younger source (ca. 700 Ma and 1000 Ma). Samples from the Vaza Barris domain show the greatest scatter of both TDM and zircon ages amongst all domains, but with important contributions from Proterozoic sources (690-1050 Ma and ca. 2100 Ma) and less from Archaean sources. The Estância domain samples have zircon population peaks at 570 Ma, 600 Ma, and 920-980 Ma, with a few older grains; one diamictite contains only ca. 2150 Ma zircon grains. Our preliminary results support a model in which sediments of the Marancó and Macururé domains were deposited on a continental margin of the ancient Borborema plate before its collision with the São Francisco Craton; the Canindé domain is likely to be an aborted Neoproterozoic rift assemblage within the southern part of the Borborema plate (Pernambuco-Alagoas massif). The basal units of the Vaza Barris and Estância domains have clast sources from the São Francisco Craton and are best interpreted as passive margin sediments. However, the uppermost units of the Estância and Vaza Barris domains come from foreland basins formed during collision of Borborema plate with the São Francisco Craton.

  4. An Early Retirement Option for Australian Academics?

    ERIC Educational Resources Information Center

    Over, Ray

    1987-01-01

    Issues of early retirement of college and university faculty are examined as they relate to Australia's aging faculty population, and the conditions necessary to promote early retirement successfully in this context are considered. (MSE)

  5. Can Multiple Myeloma Be Found Early?

    MedlinePlus

    ... Myeloma Early Detection, Diagnosis, and Staging Can Multiple Myeloma Be Found Early? It’s difficult to diagnose multiple ... Your Doctor About Multiple Myeloma? More In Multiple Myeloma About Multiple Myeloma Causes, Risk Factors, and Prevention ...

  6. Can Prostate Cancer Be Found Early?

    MedlinePlus

    ... Prostate Cancer Early Detection, Diagnosis, and Staging Can Prostate Cancer Be Found Early? Screening is testing to find ... Health Care Team About Prostate Cancer? More In Prostate Cancer About Prostate Cancer Causes, Risk Factors, and Prevention ...

  7. The Early Development of Kinetic Theory.

    ERIC Educational Resources Information Center

    Whitaker, Robert D.

    1979-01-01

    A review of the work of Bernoulli and other early contributors to kinetic theory. One significant point is that the most outstanding work in this early period was done by a little-known Scotsman, John J. Waterston. (BB)

  8. Can Testicular Cancer Be Found Early?

    MedlinePlus

    ... Testicular Cancer Early Detection, Diagnosis, and Staging Can Testicular Cancer Be Found Early? Most testicular cancers can be ... Ask Your Doctor About Testicular Cancer? More In Testicular Cancer About Testicular Cancer Causes, Risk Factors, and Prevention ...

  9. Can Thymus Cancer Be Found Early?

    MedlinePlus

    ... Thymus Cancer Early Detection, Diagnosis, and Staging Can Thymus Cancer Be Found Early? Screening is testing for ... Ask Your Doctor About Thymus Cancer? More In Thymus Cancer About Thymus Cancer Causes, Risk Factors, and ...

  10. Can Thyroid Cancer Be Found Early?

    MedlinePlus

    ... Thyroid Cancer Early Detection, Diagnosis, and Staging Can Thyroid Cancer Be Found Early? Many cases of thyroid cancer ... Health Care Team About Thyroid Cancer? More In Thyroid Cancer About Thyroid Cancer Causes, Risk Factors, and Prevention ...

  11. Breast Cancer Early Detection and Diagnosis

    MedlinePlus

    ... En Español Category Cancer A-Z Breast Cancer Breast Cancer Early Detection and Diagnosis Breast cancer is sometimes ... cancer screening is so important. Learn more. Can Breast Cancer Be Found Early? Breast cancer is sometimes found ...

  12. Early Allergies -- Payback for a Mild Winter?

    MedlinePlus

    ... Early Allergies -- Payback for a Mild Winter? Early blooms may start you sneezing and sniffling ahead of ... dormant, Caudle said. Also, trees are starting to bloom in many parts of the United States, in ...

  13. Do 'Early Birds' Get the Healthier Worm?

    MedlinePlus

    ... medlineplus.gov/news/fullstory_163902.html Do 'Early Birds' Get the Healthier Worm? Late-to-bed types ... 2017 FRIDAY, March 3, 2017 (HealthDay News) -- Early birds may have a leg up over night owls ...

  14. Can Wilms Tumor Be Found Early?

    MedlinePlus

    ... Wilms Tumor Early Detection, Diagnosis, and Staging Can Wilms Tumor Be Found Early? Wilms tumors are usually found ... Your Child’s Doctor About Wilms Tumor? More In Wilms Tumor About Wilms Tumor Causes, Risk Factors, and Prevention ...

  15. Can Soft Tissue Sarcomas Be Found Early?

    MedlinePlus

    ... Tissue Sarcoma Early Detection, Diagnosis, and Staging Can Soft Tissue Sarcomas Be Found Early? People who have ... Your Doctor About Soft Tissue Sarcomas? More In Soft Tissue Sarcoma About Soft Tissue Sarcoma Causes, Risk ...

  16. Sedimentary rocks of early Mars.

    PubMed

    Malin, M C; Edgett, K S

    2000-12-08

    Layered and massive outcrops on Mars, some as thick as 4 kilometers, display the geomorphic attributes and stratigraphic relations of sedimentary rock. Repeated beds in some locations imply a dynamic depositional environment during early martian history. Subaerial (such as eolian, impact, and volcaniclastic) and subaqueous processes may have contributed to the formation of the layers. Affinity for impact craters suggests dominance of lacustrine deposition; alternatively, the materials were deposited in a dry, subaerial setting in which atmospheric density, and variations thereof mimic a subaqueous depositional environment. The source regions and transport paths for the materials are not preserved.

  17. Essay: early American genetics journals.

    PubMed

    Crow, James F

    2005-09-01

    Before the Second World War, there were only two North-American journals exclusively devoted to genetics - the Journal of Heredity and Genetics. In the late 1940s, Genetics spawned two progeny - the American Journal of Human Genetics and Evolution. This article recounts the early days of these journals, their influential and often colourful founding editors, and their contents. It emphasizes the contrast between those years, when a reader had a realistic chance of keeping up with the whole field, and the current plethora of journals that makes it impossible to keep up with even the tables of contents.

  18. Early Attempts at Hip Arthroplasty

    PubMed Central

    Gomez, Pablo F; Morcuende, Jose A

    2005-01-01

    Over the last three centuries, treatment of hip arthritides has evolved from rudimentary surgery to modern total hip arthroplasty (THA), which is considered one of the most successful surgical interventions ever developed. We here review the history of the early hip arthroplasty procedures for hip arthritis that preceded Charley total hip arthroplasty. An evaluation of such past enterprises is relevant, and reminds us of the ephemeral nature of human industriousness, and how medical research and procedures are not isolated developments, but correlate to the social, economical, and cultural framework of their time. PMID:16089067

  19. Early History of Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Ramsey, N. F.

    1999-06-01

    The early history of magnetic resonance to around 1950 is discussed from the point of view of a participant in it. I. I. Rabi's theory of space quantization in a gyrating magnetic field and his molecular beam experiments in the 1930s laid the foundation of the magnetic resonance method, which he and his associates subsequently pursued and developed further at Columbia University, leading eventually to the development of NMR after World War II and the invention of the separated oscillatory fields method in 1950.

  20. The Environment of Early Mars

    NASA Astrophysics Data System (ADS)

    Matsubara, Yo

    2013-12-01

    A hydrologic routing model was applied to the Noachian cratered highlands to establish the climatic conditions required to maintain lakes and valley networks on early Mars. We used the ratio of precipitation and evaporation (the X-ratio) to express climatic conditions. Simulations were conducted using various X-ratios. The results from the lake analysis showed that many of the lakes that were not identified as overflowing probably overflowed as well. Because overflowing lakes can place constrain on possible climatic condition of early Mars, it is essential to identify as many overflowing craters as possible to understand the environment of early Mars. The multiple regression analyses indicate that incision depth is strongly influenced by gradient and weakly related to discharge. The factors determining incision depend partly on the type of channel bed. However, post-flow modification of the valleys precludes direct determination of bed morphology. We found through both lake and incision depth analysis that climatic conditions on early Mars were at least as moist as those that occurred in the Great Basin region during the Pleistocene (X ≤ 4). We also report on two studies motivated by the occurrence of sinuous paleochannels on Mars. Unconfined meanders require cohesive channel banks, which is obtained commonly by a vegetation cover coupled with high suspended sediment load. The Quinn River, Nevada is a sinuous channel that flows through lacustrine sediments resulting in the river having both bed and banks composed of sediment containing at least 40% mud. In addition, ion chromatography data and SEM images indicate the presence of high solute concentrations. In the absence of vegetation, bank cohesion is provided by mud with salts aiding flocculation and possibly providing additional cohesion through cementation. A 1D depth-averaged linearized meander evolution model was calibrated using the field data collected at the Quinn River. Both approaches gave similar

  1. Early rheumatoid disease. I. Onset.

    PubMed Central

    Fleming, A; Crown, J M; Corbett, M

    1976-01-01

    We describe features with onset in 102 patients seen within the first year of rheumatoid disease. The male:female ratio was approximately 3:4, suggesting a near equal sex incidence at onset. The disease started more often in the colder months and was usually insodious, symmetrical, and involved the upper limbs. The patients were followed prospectively and outcome was assessed after a mean of 4.5 years. Older patients fared worse and there was a trend for a poorer prognosis to be indicated by an insidious onset and early progression to symmetrical involvement. PMID:970994

  2. Early detection of contagious diseases

    DOEpatents

    Colston, Jr., Billy W.; Milanovich, Fred P.; Estacio, Pedro; Chang, John

    2011-08-09

    This invention provides an electronic proximity apparatus and a surveillance method using such an apparatus for alerting individuals that are exposed to a contagious disease. When a person becomes symptomatic and is diagnosed as positive for a given contagious agent, individuals that have recently maintained a threshold proximity with respect to an infected individual are notified and advised to seek immediate medial care. Treatment of individuals in the very early phases of infection (pre-symptomatic) significantly reduces contagiousness of the infected population first exposed to the contagious disease, thus preventing spread of the disease throughout the general population.

  3. Relaxin secretion in early pregnancy.

    PubMed

    Quagliarello, J; Steinetz, B G; Weiss, G

    1979-01-01

    Relaxin is a peptide hormone produced solely by the corpus luteum of pregnant women. Extracts of human pregnancy corpora lutea have relaxin activity in bioassay systems. This activity can be measured in a heterologous porcine radioimmunoassay (RIA). Immunoreactive relaxin was undetectable in the RIA in 51 nonpregnant women. In conception cycles, relaxin immunoactivity is detectable in peripheral blood by the time of the missed menses. Relaxin detection may be used as a pregnancy test. Relaxin may be an important luteal factor, together with progesterone, in early pregnancy maintenance.

  4. Global Trends in Early Childhood Education: 2009

    ERIC Educational Resources Information Center

    Neugebauer, Roger; Goodeve, Emily

    2009-01-01

    As early childhood professionals from 78 countries prepare to travel to Belfast for the 2009 World Forum on Early Care and Education, these authors surveyed a sampling of those who will be attending on the current trends in early childhood education in their country. Delegates from over 40 countries responded, and in reviewing the reports from…

  5. Challenges and Limitations in Early Intervention

    ERIC Educational Resources Information Center

    Hadders-Algra, Mijna

    2011-01-01

    Research over the past three decades has shown that early intervention in infants biologically at risk of developmental disorders, irrespective of the presence of a brain lesion, is associated with improved cognitive development in early childhood without affecting motor development. However, at present it is unknown whether early intervention is…

  6. Perceived Stress and Canadian Early Childcare Educators

    ERIC Educational Resources Information Center

    Wagner, Shannon L.; Forer, Barry; Cepeda, Ivan L.; Goelman, Hillel; Maggi, Stefania; D'Angiulli, Amedeo; Wessel, Julie; Hertzman, Clyde; Grunau, Ruth E.

    2013-01-01

    Background: Occupational stress for early childcare educators is an area of apparent understudy in the literature. The present study attempted to address this gap and provide some updated data regarding the experiences of this occupational group. Methods: Early childhood workers across a variety of early childhood education settings (N = 69)…

  7. Survival After Early and Normal Retirement

    ERIC Educational Resources Information Center

    Haynes, Suzanne G.; And Others

    1978-01-01

    Describes an epidemiological study of the patterns and correlates of survival after early (age 62 to 64) and normal retirement (age 65). Death rates were significantly elevated during the first, fourth, and fifth years after early retirement. Pre-retirement health status was the only significant predictor of survival after early retirement.…

  8. Early Years: Where Does Science Fit In?

    ERIC Educational Resources Information Center

    Rogers, Victoria

    2012-01-01

    Science provides foundations for people to understand what is happening around them, supplies information for developments to be made and explains why things happen. As a science and early years specialist, the author often wondered how early years and science can be combined. Where is the place of science within the Early Years Foundation Stage…

  9. Changing Views on Male Early Childhood Teachers.

    ERIC Educational Resources Information Center

    Robinson, Bryan E.

    1981-01-01

    Traces the changing views on the role and status of male early childhood education teachers in the forties and fifties (male prohibition), the sixties and early seventies (the macho image), and the late seventies and early eighties (the age of androgyny).

  10. Gender Equity in the Early Years

    ERIC Educational Resources Information Center

    Browne, Naima

    2004-01-01

    This book critically evaluates the extent to which current early years policies, provision and practice promote and foster gender equity. It explores the rationale for the drive to employ more men in the early years field and examines the link made between "underachievement" in boys and the "feminine: nature of early years…

  11. Early Learning and Educational Technology Policy Brief

    ERIC Educational Resources Information Center

    Lee, Joan

    2016-01-01

    Recognizing the growth of technology use in early learning settings, the U.S. Department of Education and U.S. Department of Health and Human Services collaborated in the development of the "Early Learning and Educational Technology Policy Brief" to promote developmentally appropriate use of technology in homes and early learning…

  12. International Handbook of Early Childhood Education.

    ERIC Educational Resources Information Center

    Woodill, Gary A., Ed.; And Others

    The first of two introductory essays in this handbook presents a historical perspective on international early childhood education; the second provides a cross-national analysis of themes in late 20th century child care and early education. The bulk of the document consists of essays that review early childhood, preschool, primary, or elementary…

  13. Dispersing Waves: Innovation in Early Childhood Education

    ERIC Educational Resources Information Center

    Meade, Anne, Ed.

    2010-01-01

    Early childhood education Centres of Innovation (COI) were established in 2002 as part of the 10-year plan for early childhood education, "Pathways to the Future/Nga Huarahi Arataki." In COI projects, innovative early childhood teaching teams reflect on and investigate their practices through action research, and share their findings…

  14. Examining Text Complexity in the Early Grades

    ERIC Educational Resources Information Center

    Fitzgerald, Jill; Elmore, Jeff; Hiebert, Elfrieda H.; Koons, Heather H.; Bowen, Kimberly; Sanford-Moore, Eleanor E.; Stenner, A. Jackson

    2016-01-01

    The Common Core raises the stature of texts to new heights, creating a hubbub. The fuss is especially messy at the early grades, where children are expected to read more complex texts than in the past. But early-grades teachers have been given little actionable guidance about text complexity. The authors recently examined early-grades texts to…

  15. Early Childhood Inclusion in the United Kingdom

    ERIC Educational Resources Information Center

    Blackburn, Carolyn

    2016-01-01

    A policy-to-practice paper is presented of early childhood inclusion in England. The article aims to report the benefits of early intervention services and early childhood inclusion for children with special educational needs and disabilities (SEND), document the chronology of policy development, and discuss research evidence about…

  16. Michigan Early Adolescent Survey: Final Report.

    ERIC Educational Resources Information Center

    Keith, Joanne; And Others

    This document contains the final report from the Michigan Early Adolescent Survey, a study undertaken to: (1) develop a profile of Michigan early adolescents that focused on out-of-school time and included biological, psychological, and sociological information; (2) develop a profile of families which included early adolescents; (3) assess the…

  17. Leadership in Early Childhood Special Education

    ERIC Educational Resources Information Center

    Arora, Samita Berry

    2013-01-01

    With the demands of high quality early childhood special education programs within public school settings, there is a need to place emphasis on research and training regarding early childhood leaders and managers in this complex and diverse field. The focus of this research is to examine what early childhood special education (ECSE) leadership…

  18. Early Childhood Education: A Selected, Annotated Bibliography.

    ERIC Educational Resources Information Center

    Yan, Rose, Comp.

    This bibliography on early childhood (toddler to about age six) and early childhood education is divided into three main sections: annotations of monographs and selected papers, notes on journal articles, and abstracts of research reports. These are followed by a brief section on nonconventional (usually mixed media) materials on early childhood…

  19. Early Childhood Education: The Case of Turkey

    ERIC Educational Resources Information Center

    Usakli, Hakan

    2010-01-01

    It is now widely recognized that early childhood education has paramount significance for the well-being of societies. In this study, the current situation of early childhood education in Turkey is discussed mainly in terms of its perception by the government, the school enrollment rate and the quality of early childhood education programs. The…

  20. Early Care and Education in Ghana.

    ERIC Educational Resources Information Center

    Morrison, Johnetta Wade

    2001-01-01

    Examines the present state of early care and education in Ghana. Includes historical background related to mission schools and day nurseries prior to independence from Britain. Describes the current registration and supervision of early childhood programs, the types of preschool facilities, and future plans for early childhood development.…

  1. Narrative Identity and Early Childhood Education

    ERIC Educational Resources Information Center

    Farquhar, Sandy

    2012-01-01

    An intensification of interest in early childhood by government, parents, and employers, focuses primarily on the provision of private early childhood education services outside of the home. With a focus on New Zealand, the paper argues that the form of early education now promoted is a particular form of care and education that moves children…

  2. The Essential Value of Early Education.

    ERIC Educational Resources Information Center

    Stedman, Donald J.

    1988-01-01

    The article reviews the literature on the effectiveness of early stimulation programs to prevent intellectual or social retardation. It summarizes findings and recommends continued use and development of early stimulation as a primary prevention strategy. Also stressed is early identification of preschoolers with potential or apparent…

  3. Evaluating and Supporting Early Childhood Teachers

    ERIC Educational Resources Information Center

    Passe, Angèle Sancho

    2015-01-01

    There's a lot of conversation in the early childhood community on evaluating teachers to improve their performance. Raising the quality of early care and education is a priority for policymakers and practitioners on local, state, and federal levels. As a result, much attention is being focused on early childhood educators to ensure that they do a…

  4. Visualization of early chromosome condensation

    PubMed Central

    Kireeva, Natashe; Lakonishok, Margot; Kireev, Igor; Hirano, Tatsuya; Belmont, Andrew S.

    2004-01-01

    Current models of mitotic chromosome structure are based largely on the examination of maximally condensed metaphase chromosomes. Here, we test these models by correlating the distribution of two scaffold components with the appearance of prophase chromosome folding intermediates. We confirm an axial distribution of topoisomerase IIα and the condensin subunit, structural maintenance of chromosomes 2 (SMC2), in unextracted metaphase chromosomes, with SMC2 localizing to a 150–200-nm-diameter central core. In contrast to predictions of radial loop/scaffold models, this axial distribution does not appear until late prophase, after formation of uniformly condensed middle prophase chromosomes. Instead, SMC2 associates throughout early and middle prophase chromatids, frequently forming foci over the chromosome exterior. Early prophase condensation occurs through folding of large-scale chromatin fibers into condensed masses. These resolve into linear, 200–300-nm-diameter middle prophase chromatids that double in diameter by late prophase. We propose a unified model of chromosome structure in which hierarchical levels of chromatin folding are stabilized late in mitosis by an axial “glue.” PMID:15353545

  5. [Early childhood growth and development].

    PubMed

    Arce, Melitón

    2015-01-01

    This article describes and discusses issues related to the process of childhood growth and development, with emphasis on the early years, a period in which this process reaches critical speed on major structures and functions of the human economy. We reaffirm that this can contribute to the social availability of a generation of increasingly better adults, which in turn will be able to contribute to building a better world and within it a society that enjoys greater prosperity. In the first chapter, we discuss the general considerations on the favorable evolution of human society based on quality of future adults, meaning the accomplishments that today’s children will gain. A second chapter mentions the basics of growth and development in the different fields and the various phenomena that occur in it. In the third we refer to lost opportunities and negative factors that can affect delaying the process and thereby result in not obtaining the expected accomplishments. In the fourth, conclusions and recommendations are presented confirming the initial conception that good early child care serves to build a better society and some recommendations are formulated to make it a good practice.

  6. [Early diagnosis of ectopic pregnancy].

    PubMed

    Belics, Zoran; Gérecz, Balázs; Csákány, M György

    2014-07-20

    Ectopic pregnancy is a high-risk condition that occurs in 2% of reported pregnancies. This percentage is fivefold higher than that registered in the 1970s. Since 1970 there has been a two-fold increase in the ratio of ectopic pregnancies to all reported pregnancies in Hungary and in 2012 7.4 ectopic pregnancies per thousand registered pregnancies were reported. Recently, the majority (80%) of cases can be diagnosed in early stage, and the related mortality objectively decreased in the past few decades to 3.8/10,000 ectopic pregnancies. If a woman with positive pregnancy test has abdominal pain and/or vaginal bleeding the physician should perform a work-up to safely exclude the possibility of ectopic pregnancy. The basis of diagnosis is ultrasonography, especially vaginal ultrasound examination and measurement of the β-subunit of human chorionic gonadotropin. The ultrasound diagnosis is based on the visualization of an ectopic mass rather than the inability to visualize an intrauterine pregnancy. In some questionable cases the diagnostic uterine curettage or laparoscopy may be useful. The actuality of this topic is justified by practical difficulties in obtaining correct diagnosis, especially in the early gestational time.

  7. Early identification of motor delay

    PubMed Central

    Harris, Susan R.

    2016-01-01

    Objective To describe the Harris Infant Neuromotor Test (HINT), an infant neuromotor test using Canadian norms published in 2010 that could be used to screen for motor delay during the first year of life. Quality of evidence Extensive research has been published on the intrarater, interrater, and test-retest reliability and the content, concurrent, predictive, and known-groups validity of the HINT, as well as on the sensitivity, specificity, and positive and negative predictive values of parental concerns, as assessed by the HINT. Most evidence is level II. Main message Diagnosing motor delays during the first year of life is important because these often indicate more generalized developmental delays or specific disabilities, such as cerebral palsy. Parental concerns about their children’s motor development are strongly predictive of subsequent diagnoses involving motor delay. Conclusion Only through early identification of developmental motor delays, initially with screening tools such as the HINT, is it possible to provide referrals for early intervention that could benefit both the infant and the family. PMID:27521388

  8. Characterizing the Early Impact Bombardment

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.

    2005-01-01

    The early bombardment revealed in the larger impact craters and basins on the moon was a major planetary process that affected all bodies in the inner solar system, including the Earth and Mars. Understanding the nature and timing of this bombardment is a fundamental planetary problem. The surface density of lunar impact craters within a given size range on a given lunar surface is a measure of the age of that surface relative to other lunar surfaces. When crater densities are combined with absolute radiometric ages determined on lunar rocks returned to Earth, the flux of large lunar impactors through time can be estimated. These studies suggest that the flux of impactors producing craters greater than 1 km in diameter has been approximately constant over the past approx. 3 Gyr. However, prior to 3.0 - 3.5 Gyr the impactor flux was much larger and defines an early bombardment period. Unfortunately, no lunar surface feature older than approx. 4 Gyr is accurately dated, and the surface density of craters are saturated in most of the lunar highlands. This means that such data cannot define the impactor flux between lunar formation and approx. 4 Gyr ago.

  9. Early Soil Moisture Field Experiments

    NASA Astrophysics Data System (ADS)

    Schmugge, T.

    2008-12-01

    Before the large scale field experiments described in the call for papers, there were a number of experiments devoted to a single parameter, e.g. soil moisture. In the early 1970's, before the launch of the first microwave radiometer by NASA, there were a number of aircraft experiments to determine utility of these sensors for land observations. For soil moisture, these experiments were conducted in southwestern United States over irrigated agricultural areas which could provide a wide range of moisture conditions on a given day. The radiometers covered the wavelength range from 0.8 to 21 cm. These experiments demonstrated that it is possible to observe soil moisture variations remotely using a microwave radiometer with a sensitivity of about 3 K / unit of soil moisture. The results also showed that the longer wavelengths were better, with a radiometer at the 21 cm wavelength giving the best results. These positive results led to the development of Push Broom Microwave Radiometer (PBMR) and the Electrically Scanned Thinned Array Radiometer (ESTAR) instruments at the 21-cm wavelength. They have been used extensively in the large-scale experiments such as HAPEX-MOBILHY, FIFE, Monsoon90, SMEX, etc. The multi-beam nature of these instruments makes it possible to obtain more extensive coverage and thus to map spatial variations of surface soil moisture. Examples of the early results along with the more recent soil moisture maps will be presented.

  10. The Planck Mission: Early Results

    SciTech Connect

    Marco Bersanelli

    2012-03-07

    The ESA Planck space mission, launched on May 14, 2009, is dedicated to high precision measurements of the cosmic microwave background (CMB), the first light of the universe, both in temperature and polarization. The satellite observes the full sky from a far-Earth orbit with two cryogenic instruments in the 30-850 GHz range at the focal plane of a 1.5-meter telescope. The primary objective of Planck is to measure with unprecedented precision the key cosmological parameters and to provide accurate tests of physics in the early universe. Planck has recently completed the fifth full-sky survey. The data analysis is underway. The first cosmology results are expected in early 2013 while a number of astrophysical results have been recently delivered to the community, including galactic and extragalactic astrophysics and a rich catalogue of radio and infrared sources. These results demonstrate the excellent in-orbit performance of the instruments and give excellent prospects for the forthcoming cosmological results.

  11. Early history of scapular fractures.

    PubMed

    Bartoníček, Jan; Kozánek, Michal; Jupiter, Jesse B

    2016-01-01

    The first to use the term Scapula was Vesalius (1514-1564) and thus it has remained ever since. Probably the oldest injured scapula, from 250 million years ago, was described by Chinese authors of a skeletal examination of a fossilised remains of a dinosaur Yangchuanosaurus hepingensis. In humans, the oldest known scapular fractures date back to the prehistoric and early historic times. In ancient times, a fracture of acromion was described in the treatises of Hippocrates. Early modern history of the treatment of scapular fractures is closely interlinked with the history of the French surgery. The first to point out the existence of these fractures were Petit, Du Verney and Desault in the 18th century. The first study devoted solely to scapular fractures was published by Traugott Karl August Vogt in 1799. Thomas Callaway published in 1849 an extensive dissertation on injuries to the shoulder girdle, in which he discussed a number of cases known at that time. The first radiograph of a scapular fracture was published by Petty in 1907. Mayo Robson (1884), Lambotte (1913) and Lane (1914) were pioneers in the surgical treatment of these fractures, followed in 1923 by the French surgeons Lenormat, Dujarrier and Basset. The first internal fixation of the glenoid fossa, including a radiograph, was published by Fischer in 1939.

  12. Early detection and early intervention of hearing handicapped children.

    PubMed

    Victor, P

    1992-01-01

    Early detection means the detection of hearing impairment in an infant under 2 years of age. It is vital as language and other sound-related mental development takes place within the first 3 years of life, and delay leads to secondary disabilities. The delay in language development may be observed by attentive parents at 10-12 months of age and by some not until 3-4 years of age. The family physician often detects a false-positive response, and a child specialist's opinion often is not much different. Most ear, nose, and throat departments have some provisions for audiological testing, however, the audiological section's role is to identify and assess cases for middle ear surgery. Early intervention consists of 1) the provision of amplification, 2) medical assistance, and 3) educational assistance. Pre school programs are held in nursery day schools where deaf children are given 4 hours of daily assistance for 3 years preparing them for placement in the ordinary hearing school in Class I. Special schools for the deaf in India include 1) oral schools without individual hearing aids but with group hearing aids, 2) oral and aural schools with individual hearing aids and group hearing aids, and 3) combined method schools without individual hearing aids and with or without group hearing aids. The evaluation of a program in New Delhi, after its 6 years of existence, sought to identify the strong points and weaknesses in the management of deaf children. This role model was disseminated through 4 series of Max Mueller Bhavan's All India Workshops for parents and teachers of hearing impaired children held at New Delhi, Bombay, Madras, Bangalore and Calcutta between 1981 and 1985. The parents and the professionals who attend these courses publicize them further. Many of them visited the programs in New Delhi with the desire to establish this role model in their school or city.

  13. Recent Coverage of Early Childhood Education Approaches in Open Access Early Childhood Journals

    ERIC Educational Resources Information Center

    Keskin, Burhanettin

    2016-01-01

    A content analysis of the coverage of the major approaches to early childhood education in the early childhood research journals, published between 2010 and 2014, that are early childhood research oriented and have free online access were investigated. Among 21 journals in early childhood education, two journals were selected for the content…

  14. Structure of the surface layer of the methanogenic archaean Methanosarcina acetivorans

    SciTech Connect

    Arbing, Mark A.; Chan, Sum; Shin, Annie; Phan, Tung; Ahn, Christine J.; Rohlin, Lars; Gunsalus, Robert P.

    2012-09-05

    Archaea have a self-assembling proteinaceous surface (S-) layer as the primary and outermost boundary of their cell envelopes. The S-layer maintains structural rigidity, protects the organism from adverse environmental elements, and yet provides access to all essential nutrients. We have determined the crystal structure of one of the two 'homologous' tandem polypeptide repeats that comprise the Methanosarcina acetivorans S-layer protein and propose a high-resolution model for a microbial S-layer. The molecular features of our hexameric S-layer model recapitulate those visualized by medium resolution electron microscopy studies of microbial S-layers and greatly expand our molecular view of S-layer dimensions, porosity, and symmetry. The S-layer model reveals a negatively charged molecular sieve that presents both a charge and size barrier to restrict access to the cell periplasmic-like space. The {beta}-sandwich folds of the S-layer protein are structurally homologous to eukaryotic virus envelope proteins, suggesting that Archaea and viruses have arrived at a common solution for protective envelope structures. These results provide insight into the evolutionary origins of primitive cell envelope structures, of which the S-layer is considered to be among the most primitive: it also provides a platform for the development of self-assembling nanomaterials with diverse functional and structural properties.

  15. The photochemical origins of life and photoreaction of ferrous ion in the archaean oceans

    NASA Technical Reports Server (NTRS)

    Mauzerall, David C.

    1990-01-01

    A general argument is made for the photochemical origins of life. A constant flux of free energy is required to maintain the organized state of matter called life. Solar photons are the unique source of the large amounts of energy probably required to initiate this organization and certainly required for the evolution of life to occur. The completion of this argument will require the experimental determination of suitable photochemical reactions. It is shown that biogenetic porphyrins readily photooxidize substrates and emit hydrogen in the presence of a catalyst. These results are consistent with the Granick hypothesis, which relates a biosynthetic pathway to its evolutionary origin. It has been shown that photoexcitation of ferrous ion at neutral pH with near ultraviolet light produces hydrogen with high quantum yield. This same simple system may reduce carbon dioxide to formaldehyde and further products. These reactions offer a solution to the dilemma confronting the Oparin-Urey-Miller model of the chemical origin of life. If carbon dioxide is the main form of carbon on the primitive earth, the ferrous photoreaction may provide the reduced carbon necessary for the formation of amino acids and other biogenic molecules. These results suggest that this progenitor of modern photosynthesis may have contributed to the chemical origins of life.

  16. Significance of the late Archaean granulite facies terrain boundaries, Southern West Greenland

    NASA Technical Reports Server (NTRS)

    Friend, C. R. L.; Nutman, A. P.; Mcgregor, V. R.

    1988-01-01

    Three distinct episodes and occurrences of granulite metamorphism in West Greenland are described: (1) the oldest fragmentary granulites occur within the 3.6-Ga Amitsoq gneisses and appear to have formed 200 Ma after the continental crust in which they lie (Spatially associated rapakivi granites have zircon cores as old as 3.8 Ga, but Rb-Sr, whole-rock Pb-Pb, and all other systems give 3.6 Ga, so these granulites apparently represent a later metamorphic event); (2) 3.0-Ga granulites of the Nordlandet Peninsula NW of Godthaab, developed immediately after crustal formation in hot, dry conditions, are carbonate-free, associated with voluminous tonalite, and formed at peak metamorphic conditions of 800 C and 7 to 8 kbar (Synmetamorphic trondhjemite abounds and the activity of H2O has been indicated by Pilar to have varied greatly); and (3) 2.8-Ga granulites south of Godthaab, lie to the south of retrogressed amphibolite terranes. Prograde amphibolite-granulite transitions are clearly preserved only locally at the southern end of this block, near Bjornesund, south of Fiskenaesset. Progressively deeper parts of the crust are exposed from south to north as a major thrust fault is approached. Characteristic big hornblende pegmatites, which outcrop close to the thrust in the east, have been formed by replacement of orthopyroxene. Comparable features were not seen in South Indian granulites. It was concluded that no one mechanism accounts for the origin of all granulites in West Greenland. Various processes have interacted in different ways, and what happened in individual areas must be worked out by considering all possible processes.

  17. Transpression as the main deformational event in an Archaean greenstone belt, northeastern Minnesota

    NASA Technical Reports Server (NTRS)

    Hudleston, P. J.; Schultz-Ela, D.; Bauer, R. L.; Southwick, D. L.

    1986-01-01

    Deformed and metamorphosed sedimentary and volcanic rocks of the Vermilion district constitute an Archean greenstone belt trending east-west between higher grade rocks of the Vermilion Granitic Complex to the north and the Giants Range batholith to the south. Metamorphic grade is low throughout, being lowest in the center of the belt (chlorite zone of the greenschist facies). All the measured strain, a cleavage or schistosity, and a mineral lineation in this belt are attributed to the main phase of deformation D sub 2 that followed an earlier nappe-forming event D sub 1, which left little evidence of penetrative fabric. Previous work assumed that the D sub 2 deformation resulted from north-south compression across the district. It is now believed that a significant component of this deformation resulted from dextral shear across the whole region. Thus the Vermilion fault, a late-state largely strike-slip structure that bounds the Vermilion district to the north, may simply be the latest, most brittle expression of a shear regime that was much more widespread in space and time. Features that are indicative of shear include ductile shear zones with sigmoidal foliation patterns, highly schistose zones with the development of shear bands, feldspar clasts or pyrite cubes with asymmetric pressure shadows, and the fact that the asymmetry of the F sub 2 folds is predominantly Z for at least 15 km south of the Vermilion fault.

  18. Structure of the surface layer of the methanogenic archaean Methanosarcina acetivorans.

    PubMed

    Arbing, Mark A; Chan, Sum; Shin, Annie; Phan, Tung; Ahn, Christine J; Rohlin, Lars; Gunsalus, Robert P

    2012-07-17

    Archaea have a self-assembling proteinaceous surface (S-) layer as the primary and outermost boundary of their cell envelopes. The S-layer maintains structural rigidity, protects the organism from adverse environmental elements, and yet provides access to all essential nutrients. We have determined the crystal structure of one of the two "homologous" tandem polypeptide repeats that comprise the Methanosarcina acetivorans S-layer protein and propose a high-resolution model for a microbial S-layer. The molecular features of our hexameric S-layer model recapitulate those visualized by medium resolution electron microscopy studies of microbial S-layers and greatly expand our molecular view of S-layer dimensions, porosity, and symmetry. The S-layer model reveals a negatively charged molecular sieve that presents both a charge and size barrier to restrict access to the cell periplasmic-like space. The β-sandwich folds of the S-layer protein are structurally homologous to eukaryotic virus envelope proteins, suggesting that Archaea and viruses have arrived at a common solution for protective envelope structures. These results provide insight into the evolutionary origins of primitive cell envelope structures, of which the S-layer is considered to be among the most primitive: it also provides a platform for the development of self-assembling nanomaterials with diverse functional and structural properties.

  19. Geochemical investigation of Archaean Bimodal and Dwalile metamorphic suites, Ancient Gneiss Complex, Swaziland

    USGS Publications Warehouse

    Hunter, D.R.; Barker, F.; Millard, H.T.

    1984-01-01

    The bimodal suite (BMS) comprises leucotonalitic and trondhjemitic gneisses interlayered with amphibolites. Based on geochemical parameters three main groups of siliceous gneiss are recognized: (i) SiO2 14%, and fractionated light rare-earth element (REE) and flat heavy REE patterns; (ii) SiO2 and Al2O3 contents similar to (i) but with strongly fractionated REE patterns with steep heavy REE slopes; (iii) SiO2 > 73%, Al2O3 < 14%, Zr ??? 500 ppm and high contents of total REE having fractionated light REE and flat heavy REE patterns with large negative Eu anomalies. The interlayered amphibolites have major element abundances similar to those of basaltic komatiites, Mg-tholeiites and Fe-rich tholeiites. The former have gently sloping REE patterns, whereas the Mg-tholeiites have non-uniform REE patterns ranging from flat (??? 10 times chondrite) to strongly light REE-enriched. The Fe-rich amphibolites have flat REE patterns at 20-30 times chondrite. The Dwalile metamorphic suite, which is preserved in the keels of synforms within the BMS, includes peridotitic komatiites that have depleted light REE patterns similar to those of compositionally similar volcanics in the Onverwacht Group, Barberton, basaltic komatiites and tholeiites. The basaltic komatiites have REE patterns parallel to those of the BMS basaltic komatiites but with lower total REE contents. The Dwalile tholeiites have flat REE patterns. The basic and ultrabasic liquids were derived by partial melting of a mantle source which may have been heterogeneous or the heterogeneity may have resulted from sequential melting of the mantle source. The Fe-rich amphibolites were derived either from liquids generated at shallow levels or from liquids generated at depth which subsequently underwent extensive fractionation. ?? 1984.

  20. Archaean wrench-fault tectonics in the Abitibi greenstone belt of Canada

    NASA Technical Reports Server (NTRS)

    Hubert, C.

    1986-01-01

    A tectonic model is proposed in which the southern Abitibi belt formed in a series of rift basins which dissected an earlier formed volcanic arc. Comparisons can be made with Phanerozoic areas such as, the Hokuroko basin of Japan, the Taupo volcanic zone of new Zealand and the Sumatra and Nicaragua volcanic arcs. In addition the identification of the major E - W thrust shears make it possible to speculate that the southern Abitibi belt comprises a collage of blocks of terrane which have been accreted against a more stable continental margin or microcontinent. If this interpretation is correct analogies can be made with the SW margin of the U.S.A. in which recently formed blocks of volcanic terrane are being accreted against its western margin.

  1. Gneiss-charnockite-granite connection in the archaean crust of Karnataka Craton, India

    NASA Technical Reports Server (NTRS)

    Ananthaiyer, G. V.

    1988-01-01

    It is explained that the big picture of the Indian crust contains essentially three components: (1) the upper crust, which is composed of platformal sedimentary sequences (including banded iron formations), (2) the middle crust, which is represented by the Peninsular gneiss, and (3) the deep crust, which is composed predominantly of charnockites. The charnockitization controversy was addressed by stating that CO2 is absolutely not essential for charnockite formation, and it is suggested rather that molecular hydrogen movements play an important role.

  2. Tectonic setting and evolution of late Archaean greenstone belts of Superior Province, Canada

    NASA Technical Reports Server (NTRS)

    Card, K. D.

    1986-01-01

    Late Archean (3.0-2.5 Ga) greenstone belts are a major component of the Superior Province of the Canadian Shield where alternating, metavolcanic - rich and metasedimentary - rich subprovinces form a prominent central striped region bordered in part by high-grade gneiss subprovinces, the Pikiwitonei and Minto in the north, and the Minnesota River Valley in the south. The high-grade gneiss subprovinces are characterized by granulite facies gneiss of plutonic and supracrustal origin, and by abundant plutonic rocks. Minnesota River Valley has rocks older than 3.5 Ga; absolute ages of Pikiwitonei and Minto rocks are unknown but Minto does have north-south structural trends distinctive from the dominant east-west structures of Superior Province. A discussion follows.

  3. Carbon isotope evidence for a magmatic origin for Archaean gold-quartz vein ore deposits

    NASA Technical Reports Server (NTRS)

    Burrows, D. R.; Wood, P. C.; Spooner, E. T. C.

    1986-01-01

    Sediments from three sites in the Santa Barbara Basin were examined with a 160X power light microscope and TEM equipment to characterize the magnetostatic bacteria (MB) in the samples. Both the free magnetite and the crystals in the MB in the samples had lengths from 40-60 nm in length and increased in size from one end to the next. An intact magnetosome was also observed. Scanning the sediments with saturation isothermal remanent magnetization (SIRM) and altering field demagnetization techniques using a SQUID magnetometer yielded coercivity spectra which showed that the primary remanence carrier in the sediments was single domain magnetite. Although it is expected that the predominance of the bacterial magnetite component will decrease with depth in the open ocean basin, single-domain bacteria as old as 50 Myr have been observed in oceanic sediments.

  4. Early Earth differentiation [rapid communication

    NASA Astrophysics Data System (ADS)

    Walter, Michael J.; Trønnes, Reidar G.

    2004-09-01

    The birth and infancy of Earth was a time of profound differentiation involving massive internal reorganization into core, mantle and proto-crust, all within a few hundred million years of solar system formation ( t0). Physical and isotopic evidence indicate that the formation of iron-rich cores generally occurred very early in planetesimals, the building blocks of proto-Earth, within about 3 million years of t0. The final stages of terrestrial planetary accretion involved violent and tremendously energetic giant impacts among core-segregated Mercury- to Mars-sized objects and planetary embryos. As a consequence of impact heating, the early Earth was at times partially or wholly molten, increasing the likelihood for high-pressure and high-temperature equilibration among core- and mantle-forming materials. The Earth's silicate mantle harmoniously possesses abundance levels of the siderophile elements Ni and Co that can be reconciled by equilibration between iron alloy and silicate at conditions comparable to those expected for a deep magma ocean. Solidification of a deep magma ocean possibly involved crystal-melt segregation at high pressures, but subsequent convective stirring of the mantle could have largely erased nascent layering. However, primitive upper mantle rocks apparently have some nonchondritic major and trace element refractory lithophile element ratios that can be plausibly linked to early mantle differentiation of ultra-high-pressure mantle phases. The geochemical effects of crystal fractionation in a deep magma ocean are partly constrained by high-pressure experimentation. Comparison between compositional models for the primitive convecting mantle and bulk silicate Earth generally allows, and possibly favors, 10-15% total fractionation of a deep mantle assemblage comprised predominantly of Mg-perovskite and with minor but geochemically important amounts of Ca-perovskite and ferropericlase. Long-term isolation of such a crystal pile is generally

  5. Mission to Very Early Earth

    SciTech Connect

    Hutcheon, I D; Weber, P K; Fallon, S J; Smith, J B; Aleon, J; Ryerson, F J; Harrison, T M; Cavosie, A J; Valley, J W

    2007-03-13

    The Hadean Earth is often viewed as an inhospitable and, perhaps, unlikely setting for the rise of primordial life. However, carbonaceous materials supplied by accreting meteorites and sources of chemical energy similar to those fueling life around modern deep-sea volcanic vents would have been present in abundance. More questionable are two other essential ingredients for life - liquid water and clement temperatures. Did the Hadean Earth possess a hydrosphere and temperate climate compatible with the initiation of biologic activity? If so, the popular model of an excessively hot planetary surface characterized by a basaltic crust, devoid of continental material is invalid. Similarly, establishment of an Hadean hydrosphere prior to the cessation of heavy asteroid bombardment may mean that primitive life could have evolved and then been extinguished, only to rise again. The most effective means of determining the environmental conditions on this young planet is through geochemical analysis of samples retrieved from the Early Earth. While rocks older than 4 billion years (4 Ga) have not been found, individual zircon grains, the detritus of rocks long since eroded away, have been identified with ages as old as 4.4 Ga - only {approx}160 million years younger than the Earth itself. If we can use the geochemical information contained in these unique samples to infer the nature of their source rocks and the processes that formed them, we can place constraints on the conditions prevailing at the Earth's surface shortly after formation. This project utilizes a combined analytical and experimental approach to gather the necessary geochemical data to determine the parameters required to relate the zircons to their parent materials. Mission to Early Earth involves dating, isotopic and chemical analyses of mineral and melt inclusions within zircons and of the zircons themselves. The major experimental activity at LLNL focused on the partitioning of trace elements between zircon

  6. Biogenicity of an Early Quaternary iron formation, Milos Island, Greece.

    PubMed

    Chi Fru, E; Ivarsson, M; Kilias, S P; Frings, P J; Hemmingsson, C; Broman, C; Bengtson, S; Chatzitheodoridis, E

    2015-05-01

    A ~2.0-million-year-old shallow-submarine sedimentary deposit on Milos Island, Greece, harbours an unmetamorphosed fossiliferous iron formation (IF) comparable to Precambrian banded iron formations (BIFs). This Milos IF holds the potential to provide clues to the origin of Precambrian BIFs, relative to biotic and abiotic processes. Here, we combine field stratigraphic observations, stable isotopes of C, S and Si, rock petrography and microfossil evidence from a ~5-m-thick outcrop to track potential biogeochemical processes that may have contributed to the formation of the BIF-type rocks and the abrupt transition to an overlying conglomerate-hosted IF (CIF). Bulk δ(13) C isotopic compositions lower than -25‰ provide evidence for biological contribution by the Calvin and reductive acetyl-CoA carbon fixation cycles to the origin of both the BIF-type and CIF strata. Low S levels of ~0.04 wt.% combined with δ(34) S estimates of up to ~18‰ point to a non-sulphidic depository. Positive δ(30) Si records of up to +0.53‰ in the finely laminated BIF-type rocks indicate chemical deposition on the seafloor during weak periods of arc magmatism. Negative δ(30) Si data are consistent with geological observations suggesting a sudden change to intense arc volcanism potentially terminated the deposition of the BIF-type layer. The typical Precambrian rhythmic rocks of alternating Fe- and Si-rich bands are associated with abundant and spatially distinct microbial fossil assemblages. Together with previously proposed anoxygenic photoferrotrophic iron cycling and low sedimentary N and C potentially connected to diagenetic denitrification, the Milos IF is a biogenic submarine volcano-sedimentary IF showing depositional conditions analogous to Archaean Algoma-type BIFs.

  7. Art, antiquarianism and early anatomy.

    PubMed

    Guest, Clare E L

    2014-12-01

    Discussions of the early relationship between art and anatomy are shaped by Vasari's account of Florentine artists who dissected bodies in order to understand the causes of movement, and the end of movement in action. This account eclipses the role of the study of antiquities in Renaissance anatomical illustration. Beyond techniques of presentation, such as sectioning and analytic illustration, or a preoccupation with the mutilated fragment, antiquarianism offered a reflection on the variant and the role of temperament which could be adapted for anatomical purposes. With its play on ambiguities of life and death, idealisation and damage, antiquarianism also provided a way of negotiating the difficulties of content inherent in anatomical illustration. As such, it goes beyond exclusively historical interest to provoke reflection on the modes, possibilities and humane responsibilities of medical illustration.

  8. Attention engagement in early infancy.

    PubMed

    Perra, Oliver; Gattis, Merideth

    2012-12-01

    We report a longitudinal study investigating developmental changes in the structure of attention engagement during early infancy. Forty-three infants were observed monthly from 2 to 4 months. Attention engagement was assessed from play interactions with parents, using a coding system developed by Bakeman and Adamson (1984). The results indicated a developmental transition in attention engagement at 3 months: after this age infants engaged for longer periods and in a wider variety of states. Most infants displayed person engagement at 2 months, passive joint engagement at 3 months, and object engagement at 4 months. To address whether emerging abilities of attention engagement allow infants to follow the attention of social partners, we compared attention engagement to performance on an experimental measure of attention control (reported by Perra & Gattis, 2010). Analyses revealed a positive relation between passive joint engagement and checking back, suggesting that changes in passive joint engagement reflect the development in attention control.

  9. Microdosing in early lead discovery.

    PubMed

    Jekunen, A P; Pauwels, E K J; Kairemo, K J A

    2010-03-01

    Microdosing provides a tool to enhance drug development by initiating human studies prior to Phase I studies. The purpose is to assist in the go versus no-go decision-making process and to eliminate early ineffective compounds from the drug pipeline. Selection of multiple potential leads can be performed at the clinical stage instead of in preclinical studies. The microdosing approach can be easily used for a molecularly targeted potential drug compound with a known mechanism of action. It provides useful data regarding accessibility and biodistribution that can be used in many estimations benefiting the development of the molecule. In addition, steady state and genetic investigations are becoming possible. Microdosing has a sparing effect on timelines and costs, however, the real importance is not yet known because, although it is known to be widely performed, only a few original reports have been published.

  10. Establishing Pluripotency in Early Development

    PubMed Central

    Paranjpe, Sarita S.; Veenstra, Gert Jan C.

    2015-01-01

    The earliest steps of embryonic development involve important changes in chromatin and transcription factor networks, which are orchestrated to establish pluripotent cells that will form the embryo. DNA methylation, histone modifications, the pluripotency regulatory network of transcription factors, maternal factors and newly translated proteins all contribute to these transitions in dynamic ways. Moreover, these dynamics are linked to the onset of zygotic transcription. We will review recent progress in our understanding of chromatin state and regulation of gene expression in the context of embryonic development in vertebrates, in particular mouse, Xenopus and zebrafish. We include work on mouse embryonic stem cells and highlight work that illustrates how early embryonic dynamics establish gene regulatory networks and the state of pluripotency. PMID:25857441

  11. Reduplication facilitates early word segmentation.

    PubMed

    Ota, Mitsuhiko; Skarabela, Barbora

    2017-02-06

    This study explores the possibility that early word segmentation is aided by infants' tendency to segment words with repeated syllables ('reduplication'). Twenty-four nine-month-olds were familiarized with passages containing one novel reduplicated word and one novel non-reduplicated word. Their central fixation times in response to these as well as new reduplicated and non-reduplicated words introduced at test showed that familiarized reduplicated words were segmented better than familiarized non-reduplicated words. These results demonstrate that infants are predisposed to segment words with repeated phonological elements, and suggest that register-specific words in infant-directed speech may have evolved in response to this learning bias.

  12. Principles of early drug discovery

    PubMed Central

    Hughes, JP; Rees, S; Kalindjian, SB; Philpott, KL

    2011-01-01

    Developing a new drug from original idea to the launch of a finished product is a complex process which can take 12–15 years and cost in excess of $1 billion. The idea for a target can come from a variety of sources including academic and clinical research and from the commercial sector. It may take many years to build up a body of supporting evidence before selecting a target for a costly drug discovery programme. Once a target has been chosen, the pharmaceutical industry and more recently some academic centres have streamlined a number of early processes to identify molecules which possess suitable characteristics to make acceptable drugs. This review will look at key preclinical stages of the drug discovery process, from initial target identification and validation, through assay development, high throughput screening, hit identification, lead optimization and finally the selection of a candidate molecule for clinical development. PMID:21091654

  13. Early afterdepolarizations and cardiac arrhythmias.

    PubMed

    Weiss, James N; Garfinkel, Alan; Karagueuzian, Hrayr S; Chen, Peng-Sheng; Qu, Zhilin

    2010-12-01

    Early afterdepolarizations (EADs) are an important cause of lethal ventricular arrhythmias in long QT syndromes and heart failure, but the mechanisms by which EADs at the cellular scale cause arrhythmias such as polymorphic ventricular tachycardia (PVT) and torsades de pointes (TdP) at the tissue scale are not well understood. Here we summarize recent progress in this area, discussing (1) the ionic basis of EADs, (2) evidence that deterministic chaos underlies the irregular behavior of EADs, (3) mechanisms by which chaotic EADs synchronize in large numbers of coupled cells in tissue to overcome source-sink mismatches, (4) how this synchronization process allows EADs to initiate triggers and generate mixed focal reentrant ventricular arrhythmias underlying PVT and TdP, and (5) therapeutic implications.

  14. Early detection of lung cancer

    PubMed Central

    Midthun, David E.

    2016-01-01

    Most patients with lung cancer are diagnosed when they present with symptoms, they have advanced stage disease, and curative treatment is no longer an option. An effective screening test has long been desired for early detection with the goal of reducing mortality from lung cancer. Sputum cytology, chest radiography, and computed tomography (CT) scan have been studied as potential screening tests. The National Lung Screening Trial (NLST) demonstrated a 20% reduction in mortality with low-dose CT (LDCT) screening, and guidelines now endorse annual LDCT for those at high risk. Implementation of screening is underway with the desire that the benefits be seen in clinical practice outside of a research study format. Concerns include management of false positives, cost, incidental findings, radiation exposure, and overdiagnosis. Studies continue to evaluate LDCT screening and use of biomarkers in risk assessment and diagnosis in attempt to further improve outcomes for patients with lung cancer. PMID:27158468

  15. Early education opportunities in metoritics

    NASA Astrophysics Data System (ADS)

    Peterson, Chris

    2014-02-01

    Cloudbait Observatory and the Denver Museum of Nature and Science have been operating an allsky camera network in Colorado since 2001. Most of the cameras are hosted at middle schools (ages 12-14) and high schools (ages 15-18), with some notable exceptions targeting even younger students. In addition to generating a rich collection of scientific data, this program has been very successful at introducing students to "real science", where relevant data is collected and analyzed, and the opportunity for new discovery and even publication is present. I will discuss our experience with exploring meteoritics with pre-college age students and the value to both our science program and to early science education.

  16. Early Earthquakes of the Americas

    NASA Astrophysics Data System (ADS)

    Ni, James

    2004-11-01

    Robert Kovach's second book looks at the interplay of earthquake and volcanic events, archeology, and history in the Americas. Throughout history, major earthquakes have caused the deaths of millions of people and have damaged countless cities. Earthquakes undoubtedly damaged prehistoric cities in the Americas, and evidence of these events could be preserved in archeological records. Kovach asks, Did indigenous native cultures-Indians of the Pacific Northwest, Aztecs, Mayas, and Incas-document their natural history? Some events have been explicitly documented, for example, in Mayan codices, but many may have been recorded as myth and legend. Kovach's discussions of how early cultures dealt with fearful events such as earthquakes and volcanic eruptions are colorful, informative, and entertaining, and include, for example, a depiction of how the Maya would talk to maize plants in their fields during earthquakes to reassure them.

  17. Early sexual experience and prostitution.

    PubMed

    James, J; Meyerding, J

    1977-12-01

    The authors compared several aspects of early sexual experience found in two earlier studies of prostitutes with results of research on "normal" women. The prostitutes had in common many negative experiences not found or found less often in other populations of young women. These include incestuous and/or coerced sex, lack parental guidance, intercouse at a young age, and few or no meaningful relationships with males. These women had discovered that sex could lead to a kind of status, even though that status is negatively labeled by the wider culture. In a society that values women on the basis of their sexuality, a woman who views herself as "debased" may see prostitution as a viable alternative--perhaps the only alternative.

  18. Principles of early drug discovery.

    PubMed

    Hughes, J P; Rees, S; Kalindjian, S B; Philpott, K L

    2011-03-01

    Developing a new drug from original idea to the launch of a finished product is a complex process which can take 12-15 years and cost in excess of $1 billion. The idea for a target can come from a variety of sources including academic and clinical research and from the commercial sector. It may take many years to build up a body of supporting evidence before selecting a target for a costly drug discovery programme. Once a target has been chosen, the pharmaceutical industry and more recently some academic centres have streamlined a number of early processes to identify molecules which possess suitable characteristics to make acceptable drugs. This review will look at key preclinical stages of the drug discovery process, from initial target identification and validation, through assay development, high throughput screening, hit identification, lead optimization and finally the selection of a candidate molecule for clinical development.

  19. [Early outcomes of Asperger's syndrome].

    PubMed

    Bobrov, A E; Somova, V M

    2013-01-01

    Mental state of adult patients, who since childhood had features of Asperger's syndrome (AS), was studied. We examined 107 patients (89 men and 18 women). At the moment of inclusion in the study, all the patients met criteria of ICD=10 for AS. This was confirmed by the examination of the patients with the help of ASDASQ and ASDI scales. Based on the results of psychopathological and psychological five variants of AS outcomes in the age of early adulthood were identified as follows: integrated, inhibitory, peculiar, border-line and hypernormative. At the moment of examination, psychosocial compensation was observed in 38% of patients, only 28% of patients were on treatment and 20% had a history of transitory psychotic episodes. The authors conclude that the results of the study suggest the relatively favorable prognosis of AS. The differential clinical evaluation of this group as well as implication of adequate psychosocial and psychotherapeutic methods in their treatment is needed.

  20. Deafness and Diversity: Early Intervention.

    PubMed

    Jackson, Rebecca L; Ammerman, Sarah B; Trautwein, Blane A

    2015-01-01

    earlier identification has increased the number of infants identified with hearing loss. A significant and growing proportion of children who are D/deaf or hard of hearing have a disability (DWD). Literature related to infants and toddlers who are DWD is scarce because of the heterogeneity of the population and because many disabilities may go undiagnosed until a child is older. Service availability, professional preparation, and use of evidence-based practices must improve to best meet the needs of these children and their families. An examination of theory, research, and practice in early intervention for children who are DWD revealed a lack of qualified professionals and a need for targeted instruction in teacher preparation programs and for technological advances paired with treatment (e.g., telepractice). Increased transdisciplinary collaboration and technology utilization in teacher preparation hold promise as ways of improving service provision to young children who are DWD.

  1. Early Evolution of Prestellar Cores

    NASA Astrophysics Data System (ADS)

    Horedt, G. P.

    2013-08-01

    Prestellar cores are approximated by singular polytropic spheres. Their early evolution is studied analytically with a Bondi-like scheme. The considered approximation is meaningful for polytropic exponents γ between 0 and 6/5, implying radial power-law density profiles between r -1 and r -2.5. Gravitationally unstable Jeans and Bonnor-Ebert masses differ at most by a factor of 3.25. Tidally stable prestellar cores must have a mean density contrast >~ 8 with respect to the external parent cloud medium. The mass-accretion rate relates to the cube of equivalent sound speed, as in Shu's seminal paper. The prestellar masses accreted over 105 years cover the whole stellar mass spectrum; they are derived in simple closed form, depending only on the polytropic equation of state. The stellar masses that can be formed via strict conservation of angular momentum are at most of the order of a brown dwarf.

  2. Early Triassic seawater sulfate drawdown

    NASA Astrophysics Data System (ADS)

    Song, Huyue; Tong, Jinnan; Algeo, Thomas J.; Song, Haijun; Qiu, Haiou; Zhu, Yuanyuan; Tian, Li; Bates, Steven; Lyons, Timothy W.; Luo, Genming; Kump, Lee R.

    2014-03-01

    The marine sulfur cycle is intimately linked to global carbon fluxes, atmospheric composition, and climate, yet relatively little is known about how it responded to the end-Permian biocrisis, the largest mass extinction of the Phanerozoic. Here, we analyze carbonate-associated-sulfate (CAS) from three Permo-Triassic sections in South China in order to document the behavior of the C-S cycle and its relationship to marine environmental changes during the mass extinction and its aftermath. We find that δ34SCAS varied from +9‰ to +44‰ at rates up to 100‰ Myr-1 during the Griesbachian-Smithian substages of the Early Triassic. We model the marine sulfur cycle to demonstrate that such rapid variation required drawdown of seawater sulfate concentrations to ⩽4 mM and a reduction in its residence time to ⩽200 kyr. This shorter residence time resulted in positive covariation with δ13Ccarb due to strong coupling of the organic carbon and pyrite burial fluxes. Carbon and sulfur isotopic shifts were associated with contemporaneous changes in climate, marine productivity, and microbial sulfate reduction rates, with negative shifts in δ13Ccarb and δ34SCAS linked to warming, decreased productivity, and reduced sulfate reduction. Sustained cooling during the Spathian re-invigorated oceanic overturning circulation, reduced marine anoxia, and limited pyrite burial. As seawater sulfate built to higher concentrations during the Spathian, the coupling of the marine C and S cycles came to an end and a general amelioration of marine environmental conditions set the stage for a recovery of invertebrate faunas. Variation in seawater sulfate during the Early Triassic was probably controlled by climate change, possibly linked to major eruptive phases of the Siberian Traps.

  3. Early history of neck dissection.

    PubMed

    Rinaldo, Alessandra; Ferlito, Alfio; Silver, Carl E

    2008-12-01

    With the exception of distant metastases, the presence of lymph node metastasis in the neck is accepted as the single most important adverse independent prognostic factor and an indicator of survival in squamous carcinoma of the head and neck. Neck dissection in its various forms is the standard surgical treatment for clinical, subclinical and subpathologic metastatic cancer to the neck. The pertinent literature from the beginning of the nineteenth century to the middle of the twentieth century was reviewed. The four giants of late nineteenth century surgery: von Langenbeck, Billroth, von Volkmann and Kocher developed and reported the early cases of different types of neck dissection. Butlin, in England, conceived and developed the concept of elective neck dissection. In 1888, the Polish surgeon Jawdyńsky reported and described in detail the first successful extended en bloc neck dissection. Crile, in 1905 and 1906, reported the first significant series of radical en bloc neck dissections, bringing this procedure to the attention of the medical world as an effective operation with reproducible technique and results. The greatest impetus to the status of this surgical procedure came from Martin and colleagues, who published a monumental report in 1951 of 1,450 cases that established the place and technique of radical neck dissection in the modern treatment of head and neck cancer. Neck dissection, for treatment of cervical lymph node metastases in head and neck cancer, was conceived and attempted in the nineteenth century, with some limited success reported by the end of that era. An effective operation was described and reported in the early twentieth century and evolved by the mid century into a fundamental tool in the management of patients with head and neck cancer.

  4. Imaging in early rheumatoid arthritis.

    PubMed

    McQueen, Fiona M

    2013-08-01

    Imaging in early rheumatoid arthritis (RA) has undergone extraordinary change in recent years and new techniques are now available to help the clinician diagnose and manage patients much more effectively than previously. While established modalities such as plain radiography (X-Ray) remain important, especially for detection of erosions and determining the progression of joint damage, there are many instances where ultrasound (US), magnetic resonance imaging (MRI) and computed tomography (CT) scanning provide added information. MRI and US are now used regularly by clinicians to help diagnose RA in the pre-radiographic stage as they offer improved visualisation of joint erosions. They also have the potential to provide prognostic information as MRI bone oedema/osteitis is linked to the later development of erosions and power Doppler ultrasound (PDUS) joint positivity is also a predictor of joint damage. Nuclear imaging techniques such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) are also highly sensitive for detecting joint change in early RA and pre-RA but not yet used clinically mainly because of accessibility and radiation exposure. MRI, US, scintigraphy, SPECT and PET have all been shown to detect sub-clinical joint inflammation in patients in clinical remission, a state that is now the goal of most treat-to-target management strategies. Thus, imaging may be used to direct therapeutic decision making and MRI is also now being used in clinical trials to determine the impact of disease-suppressing therapy on the course of synovitis and osteitis. As is the case for all tests, it would be unwise to rely completely on any one imaging result, as false positives and negatives can occur for all modalities. Thus, the clinician needs to choose the most relevant and reliable imaging test, while also striving to minimise patient discomfort, radiation burden and economic impact.

  5. What Predicts Early Smoking Milestones?

    PubMed Central

    Roberts, Megan E.; Colby, Suzanne M.; Jackson, Kristina M.

    2015-01-01

    Objective: As many cigarette smokers begin experimenting before age 16, prevention efforts require a comprehensive understanding of smoking predictors during adolescence. Research has made many advances in understanding the predictors of smoking initiation, yet more precision is still needed to determine whether the patterns of prediction differ across early smoking milestones. The purpose of this study was to use a sample of young adolescents to examine the predictors of two key milestones in smoking initiation: first puff and first cigarette. Method: Data came from an ongoing, prospective project examining psychosocial factors related to adolescent substance use. At Time 1 (T1), the sample was 1,023 Rhode Island middle school students (ages 10–15 years; M = 12.2). T1 measures included empirically supported risk and protective factors, as well as current smoking. Follow-up surveys assessed smoking behavior over the ensuing year (T2 smoking). Results: Cigarette availability was the most robust predictor of smoking milestones, increasing the likelihood of both first puff and first cigarette in cross-sectional and prospective analyses. Multivariable analyses also showed specificity, where some factors were only associated with one time point (e.g., age and T1 puff and cigarette), whereas others were only associated with one milestone (e.g., parental monitoring and whole cigarette at both time points). Conclusions: This study found different patterns of predictors for two early smoking milestones. Such findings are the first to suggest that puff and whole cigarette are distinct smoking milestones and reaffirm arguments that researchers should distinguish the various stages of smoking initiation when examining the broader period of onset/initiation. PMID:25785801

  6. Nutrient insult in early pregnancy.

    PubMed

    Coad, Jane; Al-Rasasi, Buthaina; Morgan, Jane

    2002-02-01

    Nutrient insults in early pregnancy, such as nutrient deprivation during famines, are often associated with an unfavourable outcome. Suboptimal nutrition in the early stage of gestation has been linked to a number of adverse effects on fetal growth and development. Historically, nausea and vomiting in pregnancy (NVP) was an important contributor to pregnancy-related mortality; indeed, Charlotte Bronte died from starvation and dehydration after suffering very severe NVP 4 months into her first pregnancy (Gaskell, 1858). Although NVP seldom now progresses to be life-threatening, it affects the majority of pregnant women, and potentially presents a challenge to nutrient intake in the most vulnerable period of development. Symptoms range from mild (nausea only) to severe (a level of vomiting that restricts nutrient intake and ultimately threatens metabolic and electrolyte balance). Although NVP has been documented for thousands of years, its cause has not yet been satisfactorily elucidated, but seems to be related to endocrinological changes. Pregnant women also frequently report dietary cravings and aversions during pregnancy which can be linked to both the incidence and severity of NVP. Paradoxically, NVP appears to be positively associated with a favourable outcome of pregnancy, including increased birth weight and gestational age. The mechanisms by which NVP favours the outcome of pregnancy are not known. They may be related to women increasing their nutrient intake to alleviate symptoms, improving the quality of their diet or reducing energy expenditure. Alternatively, adaptation to a reduced nutrient intake might stimulate the expression of growth factors and affect placentation or metabolism, thus favouring fetal growth when NVP resolves.

  7. The early Earth atmosphere and early life catalysts.

    PubMed

    Ramírez Jiménez, Sandra Ignacia

    2014-01-01

    Homochirality is a property of living systems on Earth. The time, the place, and the way in which it appeared are uncertain. In a prebiotic scenario two situations are of interest: either an initial small bias for handedness of some biomolecules arouse and progressed with life, or an initial slight excess led to the actual complete dominance of the known chiral molecules. A definitive answer can probably never be given, neither from the fields of physics and chemistry nor biology. Some arguments can be advanced to understand if homochirality is necessary for the initiation of a prebiotic homochiral polymer chemistry, if this homochirality is suggesting a unique origin of life, or if a chiral template such as a mineral surface is always required to result in an enantiomeric excess. A general description of the early Earth scenario will be presented in this chapter, followed by a general description of some clays, and their role as substrates to allow the concentration and amplification of some of the building blocks of life.

  8. Can Breast Cancer in Men Be Found Early?

    MedlinePlus

    ... in Men Early Detection, Diagnosis, and Staging Can Breast Cancer in Men Be Found Early? Early detection improves ... be treated successfully. Differences affecting early detection of breast cancers in men and women There are many similarities ...

  9. Screening Early Literacy: Ideology, Illusion, and Intervention.

    ERIC Educational Resources Information Center

    Crossland, Howard

    1994-01-01

    Examines the ideology and expectations of early screening for linguistic difficulties in young children, discusses effective intervention, and presents an alternative to screening: formative assessment. (SK)

  10. Early predictors of boys’ antisocial trajectories

    PubMed Central

    SHAW, DANIEL S.; HYDE, LUKE W.; BRENNAN, LAURETTA M.

    2012-01-01

    Despite the large number of studies tracing patterns of youth antisocial behavior (AB) during adolescence, few have prospective data on the developmental precursors of AB beginning during infancy. Using a cohort of 268 low-income boys first assessed at 18 months, the current study examined predictors of early- and late-starting trajectories of AB assessed during early childhood and early adolescence. Four trajectory groups were identified, including early- and late-starting groups, a low stable group, and a high decreasing group, characterized by multiple risk factors during early childhood and early adolescence. During early childhood, parenting and maternal depression discriminated two AB trajectory groups, an early-starting and a high decreasing group, who would go on to demonstrate a high preponderance of juvenile court involvement (60% to 79%) and elevated rates of clinical depression 13 to 15 years later. The results were discussed in reference to targeting malleable family risk factors during early childhood associated with patterns of AB and mental health disorders during adolescence. PMID:22781860

  11. Raising the continental crust

    NASA Astrophysics Data System (ADS)

    Campbell, Ian H.; Davies, D. Rhodri

    2017-02-01

    The changes that occur at the boundary between the Archean and Proterozoic eons are arguably the most fundamental to affect the evolution of Earth's continental crust. The principal component of Archean continental crust is Granite-Greenstone Terranes (GGTs), with granites always dominant. The greenstones consist of a lower sequence of submarine komatiites and basalts, which erupted onto a pre-existing Tonalite-Trondhjemite-Granodiorite (TTG) crust. These basaltic rocks pass upwards initially into evolved volcanic rocks, such as andesites and dacites and, subsequently, into reworked felsic pyroclastic material and immature sediments. This transition coincides with widespread emplacement of granitoids, which stabilised (cratonised) the continental crust. Proterozoic supra-crustal rocks, on the other hand, are dominated by extensive flat-lying platform sequences of mature sediments, which were deposited on stable cratonic basements, with basaltic rocks appreciably less abundant. The siliceous TTGs cannot be produced by direct melting of the mantle, with most hypotheses for their origin requiring them to be underlain by a complimentary dense amphibole-garnet-pyroxenite root, which we suggest acted as ballast to the early continents. Ubiquitous continental pillow basalts in Archean lower greenstone sequences require the early continental crust to have been sub-marine, whereas the appearance of abundant clastic sediments, at higher stratigraphic levels, shows that it had emerged above sea level by the time of sedimentation. We hypothesise that the production of komatiites and associated basalts, the rise of the continental crust, widespread melting of the continental crust, the onset of sedimentation and subsequent cratonisation form a continuum that is the direct result of removal of the continent's dense amphibole-garnet-pyroxenite roots, triggered at a regional scale by the arrival of a mantle plume at the base of the lithosphere. Our idealised calculations suggest

  12. Early-Onset Neonatal Sepsis

    PubMed Central

    Simonsen, Kari A.; Anderson-Berry, Ann L.; Delair, Shirley F.

    2014-01-01

    SUMMARY Early-onset sepsis remains a common and serious problem for neonates, especially preterm infants. Group B streptococcus (GBS) is the most common etiologic agent, while Escherichia coli is the most common cause of mortality. Current efforts toward maternal intrapartum antimicrobial prophylaxis have significantly reduced the rates of GBS disease but have been associated with increased rates of Gram-negative infections, especially among very-low-birth-weight infants. The diagnosis of neonatal sepsis is based on a combination of clinical presentation; the use of nonspecific markers, including C-reactive protein and procalcitonin (where available); blood cultures; and the use of molecular methods, including PCR. Cytokines, including interleukin 6 (IL-6), interleukin 8 (IL-8), gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α), and cell surface antigens, including soluble intercellular adhesion molecule (sICAM) and CD64, are also being increasingly examined for use as nonspecific screening measures for neonatal sepsis. Viruses, in particular enteroviruses, parechoviruses, and herpes simplex virus (HSV), should be considered in the differential diagnosis. Empirical treatment should be based on local patterns of antimicrobial resistance but typically consists of the use of ampicillin and gentamicin, or ampicillin and cefotaxime if meningitis is suspected, until the etiologic agent has been identified. Current research is focused primarily on development of vaccines against GBS. PMID:24396135

  13. Casebooks in Early Modern England:

    PubMed Central

    Kassell, Lauren

    2014-01-01

    summary Casebooks are the richest sources that we have for encounters between early modern medical practitioners and their patients. This article compares astrological and medical records across two centuries, focused on England, and charts developments in the ways in which practitioners kept records and reflected on their practices. Astrologers had a long history of working from particular moments, stellar configurations, and events to general rules. These practices required systematic notation. Physicians increasingly modeled themselves on Hippocrates, recording details of cases as the basis for reasoned expositions of the histories of disease. Medical records, as other scholars have demonstrated, shaped the production of medical knowledge. Instead, this article focuses on the nature of casebooks as artifacts of the medical encounter. It establishes that casebooks were serial records of practice, akin to diaries, testimonials, and registers; identifies extant English casebooks and the practices that led to their production and preservation; and concludes that the processes of writing, ordering, and preserving medical records are as important for understanding the medical encounter as the records themselves. PMID:25557513

  14. VIRUS early installation and commissioning

    NASA Astrophysics Data System (ADS)

    Tuttle, Sarah E.; Hill, Gary J.; Vattiat, Brian L.; Lee, Hanshin; Drory, Niv; Kelz, Andreas; Ramsey, Jason; Peterson, Trent; Noyola, Eva; DePoy, Darren L.; Marshall, Jennifer L.; Chonis, Taylor S.; Dalton, Gavin; Fabricius, Maximilian; Farrow, Daniel; Good, John M.; Haynes, Dionne M.; Indahl, Briana; Jahn, Thomas; Kriel, Hermanus; Nicklas, Harald; Montesano, Francesco; Prochaska, Travis; Allen, Richard D.; Landriau, Martin; MacQueen, Phillip J.; Roth, Martin M.; Savage, Richard; Snigula, Jan M.

    2016-08-01

    VIRUS is a massively replicated spectrograph built for HETDEX, the Hobby Eberly Telescope Dark Energy Experiment. It consists of 156 channels within 78 units fed by 34944 fibers over the 22 arcminute field of the upgraded HET. VIRUS covers a relatively narrow bandpass (350-550nm) at low resolution (R 700) to target the emission of Lyman-alpha emitters (LAEs) for HETDEX. VIRUS is a first demonstration of industrial style assembly line replication in optical astronomy. Installation and testing of VIRUS units began in November of 2015. This winter we celebrated the first on sky instrument activity of the upgraded HET, using a VIRUS unit and LRS2-R (the upgraded facility Low Resolution Spectrograph for the HET). Here we describe progress in VIRUS installation and commissioning through June 2016. We include early sky data obtained to characterize spectrograph performance and on sky performance of the newly upgraded HET. As part of the instrumentation for first science light at the HET, the IFU fed spectrographs were used to test a full range of telescope system functionality including the field calibration unit (FCU).We also use placement of strategic IFUs to map the new HET field to the fiber placement, and demonstrate actuation of the dithering mechanism key to HETDEX observations.

  15. Early detection of materials degradation

    NASA Astrophysics Data System (ADS)

    Meyendorf, Norbert

    2017-02-01

    Lightweight components for transportation and aerospace applications are designed for an estimated lifecycle, taking expected mechanical and environmental loads into account. The main reason for catastrophic failure of components within the expected lifecycle are material inhomogeneities, like pores and inclusions as origin for fatigue cracks, that have not been detected by NDE. However, material degradation by designed or unexpected loading conditions or environmental impacts can accelerate the crack initiation or growth. Conventional NDE methods are usually able to detect cracks that are formed at the end of the degradation process, but methods for early detection of fatigue, creep, and corrosion are still a matter of research. For conventional materials ultrasonic, electromagnetic, or thermographic methods have been demonstrated as promising. Other approaches are focused to surface damage by using optical methods or characterization of the residual surface stresses that can significantly affect the creation of fatigue cracks. For conventional metallic materials, material models for nucleation and propagation of damage have been successfully applied for several years. Material microstructure/property relations are well established and the effect of loading conditions on the component life can be simulated. For advanced materials, for example carbon matrix composites or ceramic matrix composites, the processes of nucleation and propagation of damage is still not fully understood. For these materials NDE methods can not only be used for the periodic inspections, but can significantly contribute to the material scientific knowledge to understand and model the behavior of composite materials.

  16. Early flavor experiences: research update.

    PubMed

    Mennella, J A; Beauchamp, G K

    1998-07-01

    Anyone who has observed infants for any period of time can testify to the intense activity occurring in and around their mouths--the primary site for learning in the first few months of life. Before they are even able to crawl, infants have learned much about their new sensory world. Though recent research we have begun to explore the impact of these early experiences on infants' acceptance of solid foods and how they explore objects in their environment. We have also begun to focus on the sensory experiences of the formula-fed infant, in particular, how their responses to particular formulas, which are extremely unpalatable to older children and adults, change during infancy. This is a relatively new and exciting area of study, with much research yet to be done. It is clear, however, that infants are not passive receptacles for flavored foods. Parents who offer a variety of foods will provide both a nutritious, well-balanced diet, as well as an opportunity for their children's own personal preferences to develop.

  17. Noncommutativity in the early universe

    NASA Astrophysics Data System (ADS)

    Oliveira-Neto, G.; Silva de Oliveira, M.; Monerat, G. A.; Corrêa Silva, E. V.

    In the present work, we study the noncommutative version of a quantum cosmology model. The model has a Friedmann-Robertson-Walker (FRW) geometry, the matter content is a radiative perfect fluid and the spatial sections have zero constant curvature. In this model, the scale factor takes values in a bounded domain. Therefore, its quantum mechanical version has a discrete energy spectrum. We compute the discrete energy spectrum and the corresponding eigenfunctions. The energies depend on a noncommutative parameter β. We compute the scale factor expected value () for several values of β. For all of them, oscillates between maxima and minima values and never vanishes. It gives an initial indication that those models are free from singularities, at the quantum level. We improve this result by showing that if we subtract a quantity proportional to the standard deviation of a from , this quantity is still positive. The behavior, for the present model, is a drastic modification of the behavior in the corresponding commutative version of the present model. There, grows without limits with the time variable. Therefore, if the present model may represent the early stages of the universe, the results of the present paper give an indication that may have been, initially, bounded due to noncommutativity. We also compute the Bohmian trajectories for a, which are in accordance with , and the quantum potential Q. From Q, we may understand why that model is free from singularities, at the quantum level.

  18. Early evolution of the bilateria.

    PubMed

    Hausdorf, B

    2000-03-01

    The phylogeny of the Bilateria and especially the early steps in the evolution of the bilaterian bauplan are still a controversial topic. In this context the relationships of the platyhelminths and the nematodes play a crucial role. Previous molecular studies of the relationships of these groups, which were based on 18S ribosomal DNA sequences, yielded conflicting results. In the present study a new framework is developed for the phylogenetic analysis of bilaterian relationships, using concatenated amino acid sequences of several nuclear genes. In this analysis, the rhabditophoran platyhelminths are probably the sister group of all other analyzed Bilateria, the Eubilateria, which are characterized by a one-way intestine with an anus. The Eubilateria are split into the nematode lineage and the coelomates. The phylogenetic results of the present study indicate that genetic features found in the model organisms Caenorhabditis and Drosophila might be found in all Eubilateria. Estimations of the divergence times show that the major bilaterian phyla did not originate in an explosive radiation during the Cambrian but rather that the Bilateria have a several hundred million years long Precambrian history.

  19. Inflation in the early universe.

    NASA Astrophysics Data System (ADS)

    Carmeli, M.

    1998-04-01

    In this talk it will be assumed that gravitation is negligible. Under this assumption, the receding velocities of galaxies and the distances between them in the Hubble expansion are united into a four-dimensional pseudo-Euclidean manifold, similarly to space and time in ordinary special relativity. The Hubble law is assumed and is written in an invariant way that enables one to derive a four-dimensional transformation which is similar to the Lorentz transformation. The parameter in the new transformation is the ratio between the cosmic time to the Hubble time. Accordingly, the new transformation relates physical quantities at different cosmic times in the limit of weak or negligible gravitation. The transformation is then applied to the problem of the expansion of the Universe at the very early stage when gravity was negligible and thus the transformation is applicable. The author calculates the ratio of the volumes of the Universe at two different times T1 and T2 after the big bang. The result conforms with the standard inflationary universe theory, but now it is obtained without assuming that the Universe is propelled by antigravity.

  20. Early detection and rapid response

    USGS Publications Warehouse

    Westbrooks, Randy G.; Eplee, Robert E.; Simberloff, Daniel; Rejmánek, Marcel

    2011-01-01

    Prevention is the first line of defense against introduced invasive species - it is always preferable to prevent the introduction of new invaders into a region or country. However, it is not always possible to detect all alien hitchhikers imported in cargo, or to predict with any degree of certainty which introduced species will become invasive over time. Fortunately, the majority of introduced plants and animals don't become invasive. But, according to scientists at Cornell University, costs and losses due to species that do become invasive are now estimated to be over $137 billion/year in the United States. Early detection and rapid response (EDRR) is the second line of defense against introduced invasive species - EDRR is the preferred management strategy for preventing the establishment and spread of invasive species. Over the past 50 years, there has been a gradual shift away from large and medium scale federal/state single-agency-led weed eradication programs in the United States, to smaller interagency-led projects involving impacted and potential stakeholders. The importance of volunteer weed spotters in detecting and reporting suspected new invasive species has also been recognized in recent years.

  1. Early diagnosis of resistant pathogens

    PubMed Central

    2013-01-01

    Infections with organisms that are resistant to various anti-microbial agents pose a serious challenge to effective management of infections. Resistance to antimicrobial agents, which may be intrinsic or acquired, has been noted in a wide variety of microorganisms causing human infections. These include resistance to antiviral agents in HIV, HBV, CMV and influenza virus, anti-parasitic agents in Plasmodium falciparum, anti-fungal agents in certain Candida species and MDR (multidrug-resistant) tuberculosis. It is however, the problem of multidrug-resistant bacterial infections (caused by MRSA, VRE, ESBL/AmpC/metallo-β lactamase producers and colistin-resistant Gram-negative bacilli) that has become a cause of major concern in clinical settings. Infections with these organisms can increase morbidity, mortality, increase the cost of therapy and increase the duration of hospitalization. The objective of this article is to review the question how early diagnosis of these infections, affects the overall management of infected or colonized patients, with regard to antimicrobial therapy. PMID:23302786

  2. A supertree of early tetrapods.

    PubMed Central

    Ruta, Marcello; Jeffery, Jonathan E; Coates, Michael I

    2003-01-01

    A genus-level supertree for early tetrapods is built using a matrix representation of 50 source trees. The analysis of all combined trees delivers a long-stemmed topology in which most taxonomic groups are assigned to the tetrapod stem. A second analysis, which excludes source trees superseded by more comprehensive studies, supports a deep phylogenetic split between lissamphibian and amniote total groups. Instances of spurious groups are rare in both analyses. The results of the pruned second analysis are mostly comparable with those of a recent, character-based and large-scale phylogeny of Palaeozoic tetrapods. Outstanding areas of disagreement include the branching sequence of lepospondyls and the content of the amniote crown group, in particular the placement of diadectomorphs as stem diapsids. Supertrees are unsurpassed in their ability to summarize relationship patterns from multiple independent topologies. Therefore, they might be used as a simple test of the degree of corroboration of nodes in the contributory analyses. However, we urge caution in using them as a replacement for character-based cladograms and for inferring macroevolutionary patterns. PMID:14667343

  3. Genetics of early embryo survival

    SciTech Connect

    Niswander, L.; Edstroem, J.E.; Rinchik, E.M.; Magnuson, T.

    1989-01-01

    The albino-deletion complex represents one of the few regions of the mouse genome where a set of specific developmental defects are associated with a series of overlapping chromosomal deletions. A total of 37 deletions exist, all of which remove the region of mouse chromosome 7 that surrounds and includes the albino coat-color locus. The complementation patterns among these deletion chromosomes indicate that at least 9 distinct functional units exist in this region. Two of these units contain genes whose expression is required around the time the basic body plan is being established in the early postimplantation embryo. Embryos homozygous for the deletions that remove one of these units develop to day 8.5. Extensive development of the extraembryonic structures occurs, and the three primary germ layers form but there is no organization of mesoderm into somites or induction of the neural axis. Embryos homozygous for deletions that remove the second region, as well as the first, do not undergo gastrulation, and there is no development of the extraembryonic structures. 10 refs., 2 figs., 1 tab.

  4. Cosmology and the early universe

    NASA Astrophysics Data System (ADS)

    Joshi, Abhigna

    2017-01-01

    In the beginning the universe was in a hot dense state nearly 13.8 billion years ago. The thermal history of the universe was traced back to an era when the temperature was about 1012K. At this early time, the universe was filled with particles-mostly photons and leptons- whose interactions are hopefully weak enough to allow this medium to be treated as a more or less ideal gas. However, if we look back a little further, into the first 0.0001 second of cosmic history when the temperature was above 1012K. At such temperatures, there will be present in thermal equilibrium copious numbers of strongly interacting particles-mostly masons and baryons-with a mean interparticle distance less than a Compton wavelength. These particles will be in a state of continual mutual interaction, and cannot reasonably be expected to obey any simple equation of state. The inflationary epoch lasted from 10-36seconds after the Big Bang to sometime between 10-33and 10-32seconds. Matter and energy created in this time. Right after that space expanded exponentially with enormous rate of 74.3 +/-2.1Km per second per Mpc. Undergraduate student and researcher of the string theory, quantum gravity, cosmology and quantum biology.

  5. Early vision and focal attention

    NASA Astrophysics Data System (ADS)

    Julesz, Bela

    1991-07-01

    At the thirty-year anniversary of the introduction of the technique of computer-generated random-dot stereograms and random-dot cinematograms into psychology, the impact of the technique on brain research and on the study of artificial intelligence is reviewed. The main finding-that stereoscopic depth perception (stereopsis), motion perception, and preattentive texture discrimination are basically bottom-up processes, which occur without the help of the top-down processes of cognition and semantic memory-greatly simplifies the study of these processes of early vision and permits the linking of human perception with monkey neurophysiology. Particularly interesting are the unexpected findings that stereopsis (assumed to be local) is a global process, while texture discrimination (assumed to be a global process, governed by statistics) is local, based on some conspicuous local features (textons). It is shown that the top-down process of "shape (depth) from shading" does not affect stereopsis, and some of the models of machine vision are evaluated. The asymmetry effect of human texture discrimination is discussed, together with recent nonlinear spatial filter models and a novel extension of the texton theory that can cope with the asymmetry problem. This didactic review attempts to introduce the physicist to the field of psychobiology and its problems-including metascientific problems of brain research, problems of scientific creativity, the state of artificial intelligence research (including connectionist neural networks) aimed at modeling brain activity, and the fundamental role of focal attention in mental events.

  6. Topics in Early Literacy, Teacher Preparation, and International Perspectives on Early Care. Advances in Early Education and Day Care.

    ERIC Educational Resources Information Center

    Reifel, Stuart, Ed.

    This volume looks at three different broad topics that are of continuing interest for early education and care. The first part of the volume furthers the view of children's acquisition of literacy and how that acquisition takes place. The second part addresses preparation of professionals in early childhood education. The third part provides…

  7. A Review of the Isotopic and Trace Element Evidence for Mantle and Crustal Processes in the Hadean and Archean: implications for the Onset of Plate Tectonic Subduction

    NASA Astrophysics Data System (ADS)

    Smart, Katie A.; Tappe, Sebastian; Stern, Richard A.; Webb, Susan J.; Ashwal, Lewis D.

    2016-03-01

    Plate tectonics plays a vital role in the evolution of our planet. Geochemical analysis of Earth’s oldest continental crust suggests that subduction may have begun episodically about 3.8 to 3.2 billion years ago, during the early Archaean or perhaps more than 3.8 billion years ago, during the Hadean. Yet, mantle rocks record evidence for modern-style plate tectonics beginning only in the late Archaean, about 3 billion years ago. Here we analyse the nitrogen abundance, as well as the nitrogen and carbon isotopic signatures of Archaean placer diamonds from the Kaapvaal craton, South Africa, which formed in the upper mantle 3.1 to 3.5 billion years ago. We find that the diamonds have enriched nitrogen contents and isotopic compositions compared with typical mantle values. This nitrogen geochemical fingerprint could have been caused by contamination of the mantle by nitrogen-rich Archaean sediments. Furthermore, the carbon isotopic signature suggests that the diamonds formed by reduction of an oxidized fluid or melt. Assuming that the Archaean mantle was more reduced than the modern mantle, we argue that the oxidized components were introduced to the mantle by crustal recycling at subduction zones. We conclude, on the basis of evidence from mantle-derived diamonds, that modern-style plate tectonics operated as early as 3.5 billion years ago.

  8. Early Life Bereavement and Schizophrenia

    PubMed Central

    Liang, Hong; Olsen, Jørn; Yuan, Wei; Cnattingus, Sven; Vestergaard, Mogens; Obel, Carsten; Gissler, Mika; Li, Jiong

    2016-01-01

    Abstract We aimed to examine whether early life bereavement, as indicator of severe stress, was associated with an increased risk of schizophrenia later in life. Based on population registers, we established a cohort of all children born in Denmark (N = 1 686 416) and Sweden (N = 2 563 659) from 1973 to 1997. Children were categorized as exposed if they lost a first-degree relative during the first 18 years of life. Outcome is the first diagnosis of schizophrenia as either inpatient or outpatient. Log-linear Poisson regression models were used to estimate incidence rate ratios (IRRs). A total of 188,850 children (4.6%) experienced death of a first-degree relative from birth to 18 years of age. Compared with unexposed children, those exposed had overall a 39% higher risk of schizophrenia (= 1.39, 95% CI [confidence interval]: 1.32–1.47). The IRR was particularly high if the family member committed suicide (aIRR = 2.11, 95% CI: 1.90–2.34) or died due to an injury or accident (aIRR = 1.44, 95% CI: 1.27–1.63). The IRR of schizophrenia decreased with increasing child's age at bereavement (P < 0.0001). Children who experienced >1 death during the first 18 years of life (aIRR = 1.79, 95% CI: 1.46–2.19) had a higher risk than those with a single death (aIRR = 1.37, 95% CI: 1.30–1.45). The study suggested that exposure to death of a first-degree relative before 18 years was associated with an increased risk of schizophrenia in later life. The complex mechanisms behind these associations remain to be elucidated. PMID:26817875

  9. Seeing Touches Early in Life

    PubMed Central

    Addabbo, Margaret; Longhi, Elena; Bolognini, Nadia; Senna, Irene; Tagliabue, Paolo; Macchi Cassia, Viola; Turati, Chiara

    2015-01-01

    The sense of touch provides fundamental information about the surrounding world, and feedback about our own actions. Although touch is very important during the earliest stages of life, to date no study has investigated infants’ abilities to process visual stimuli implying touch. This study explores the developmental origins of the ability to visually recognize touching gestures involving others. Looking times and orienting responses were measured in a visual preference task, in which participants were simultaneously presented with two videos depicting a touching and a no-touching gesture involving human body parts (face, hand) and/or an object (spoon). In Experiment 1, 2-day-old newborns and 3-month-old infants viewed two videos: in one video a moving hand touched a static face, in the other the moving hand stopped before touching it. Results showed that only 3-month-olds, but not newborns, differentiated the touching from the no-touching gesture, displaying a preference for the former over the latter. To test whether newborns could manifest a preferential visual response when the touched body part is different from the face, in Experiment 2 newborns were presented with touching/no-touching gestures in which a hand or an inanimate object—i.e., a spoon- moved towards a static hand. Newborns were able to discriminate a hand-to-hand touching gesture, but they did not manifest any preference for the object-to-hand touch. The present findings speak in favour of an early ability to visually recognize touching gestures involving the interaction between human body parts. PMID:26366563

  10. From early wireless to Everest.

    PubMed

    Allen, A

    1998-01-01

    Medical information has been transmitted using wireless technologies for almost 80 years. A "wired wireless" electronic stethoscope was developed by the U.S. Army Signal Corps in the early 1920's, for potential use in ship-to-shore transmission of cardiac sounds. [Winters SR. Diagnosis by wireless. Scientific American June 11, 1921, p. 465] Today, wireless is used in a wide range of medical applications and at sites from transoceanic air flights to offshore oil platforms to Mt. Everest. 'Wireless LANs' are often used in medical environments. Typically, nurses and physicians in a hospital or clinic use hand-held "wireless thin client" pen computers that exchange patient information and images with the hospital server. Numerous companies, such as Fujitsu (article below) and Cruise Technologies (www.cruisetech.com) manufacture handheld pen-entry computers. One company, LXE, integrates radio-frequency (RF) enhanced hand-held computers specifically designed for production use within a wireless LAN (www.lxe.com). Other companies (Proxim, Symbol, and others) supply the wireless RF LAN infrastructure for the enterprise. Unfortunately, there have been problems with widespread deployment of wireless LANs. Perhaps the biggest impediment has been the lack of standards. Although an international standard (IEEE 802.11) was adopted in 1997, most wireless LAN products still are not compatible with the equipment of competing companies. A problem with the current standard for LAN adapters is that throughput is limited to 3 Mbps--compared to at least 10 Mbps, and often 100 Mbps, in a hard-wired Ethernet LAN. An II Mbps standard is due out in the next year or so, but it will be at least 2 years before standards-compliant products are available. This story profiles some of the ways that wireless is being used to overcome gaps in terrestrial and within-enterprise communication.

  11. Inflation in the Early Universe

    NASA Astrophysics Data System (ADS)

    Carmeli, Moshe

    In this talk it will be assumed that gravitation is negligible. Under this assumption, the receding velocities of galaxies and the distances between them in the Hubble expansion are united into a four-dimensional pseudo-Euclidean manifold, similarly to space and time in ordinary special relativity. The Hubble law is assumed and is written in an invariant way that enables one to derive a four-dimensional transformation which is similar to the Lorentz transformation. The parameter in the new transformation is the ratio between the cosmic time to the Hubble time (in which the cosmic time is measured backward with respect to the present time). Accordingly, the new transformation relates physical quantities at different cosmic times in the limit of weak or negligible gravitation. The transformation is then applied to the problem of the expansion of the Universe at the very early stage when gravity was negligible and thus the transformation is applicable. We calculate the ratio of the volumes of the Universe at two different times T1 and T2 after the Big Bang. Under the assumptions that T2 - T1 ≈ 10-32 sec and T2 ≪ 1 sec, we find that V_{2}/V_{1} = 10^{-16}/√{T_{1}}. For T1 ≈ 10-132 sec we obtain V2/V1 ≈ 1050. This result conforms with the standard inflationary universe theory, but now it is obtained without assuming that the Universe is propelled by antigravity.

  12. Artist's Concept of Early Universe

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is an artist's impression of how the very early universe (less than one billion years old) might have looked when it went through a voracious onset of star formation, converting primordial hydrogen into myriad stars at an unprecedented rate. The deepest views of the cosmos from the Hubble Space Telescope (HST) yield clues that the very first stars may have burst into the universe as brilliantly and spectacularly as a firework finale. Except in this case, the finale came first, long before Earth, the Sun ,and the Milky Way Galaxy formed. Studies of HST's deepest views of the heavens lead to the preliminary conclusion that the universe made a significant portion of its stars in a torrential firestorm of star birth, which abruptly lit up the pitch-dark heavens just a few hundred million years after the 'big bang,' the tremendous explosion that created the cosmos. Within the starburst galaxies, bright knots of hot blue stars come and go like bursting fireworks shells. Regions of new starbirth glow intensely red under torrent of ultraviolet radiation. The most massive stars self-detonate as supernovas, which explode across the sky like a string of firecrackers. A foreground starburst galaxy at lower right is sculpted with hot bubbles from supernova explosions and torrential stellar winds. Unlike today there is very little dust in these galaxies, because the heavier elements have not yet been cooked up through nucleosynthesis in stars. Recent analysis of HST deep sky images supports the theory that the first stars in the universe appeared in an abrupt eruption of star formation, rather than at a gradual pace. Science Credit: NASA and K. Lanzetta (SUNY). Artwork Credit: Adolf Schaller for STScI.

  13. The first 800 million years of earth's history

    NASA Technical Reports Server (NTRS)

    Smith, J. V.

    1981-01-01

    It is pointed out that there is no direct geological information on the first 750 Ma of earth history. Consequently the reported study is based on controversial inferences drawn from the moon, other planets and meteorites, coupled with backward extrapolation from surviving terrestrial rocks, especially those of Archaean age. Aspects of accretion are considered, taking into account cosmochemical and cosmophysical evidence, a new earth model, and convection systems. Attention is given to phase-equilibrium constraints, estimates of heat production, the bombardment history of the moon and implications for the earth, and the nature of the early crust. From a combination of physical, chemical, and petrological arguments, it is concluded that the earth's surface underwent intense volcanism in the pre-Archaean era, and that the rock types were chemically similar to those found in the early Archaean era.

  14. The Early History of Life

    NASA Astrophysics Data System (ADS)

    Nisbet, E. G.; Fowler, C. M. R.

    2003-12-01

    The youth of the Earth is strange to us. Many of the most fundamental constraints on life may have been different, especially the oxidation state of the surface. Should we suddenly land on its Hadean or early Archean surface by some sci-fi accident, we would not recognize our home. Above, the sky may have been green or some other unworldly color, and above that the weak young Sun might have been unrecognizable to someone trying to identify it from its spectrum. Below, seismology would show a hot, comparatively low-viscosity interior, possibly with a magma ocean in the deeper part of the upper mantle (Drake and Righter, 2002; Nisbet and Walker, 1982), and a core that, though present, was perhaps rather smaller than today. The continents may have been small islands in an icy sea, mostly frozen with some leads of open water, ( Sleep et al., 2001). Into these icy oceans, huge protruding Hawaii-like volcanoes would have poured out vast far-spreading floods of komatiite lavas in immense eruptions that may have created sudden local hypercane storms to disrupt the nearby icebergs. And meteorites would rain down.Or perhaps it was not so strange, nor so violent. The child is father to the man; young Earth was mother to Old Earth. Earth had hydrogen, silicate rock below and on the surface abundant carbon, which her ancient self retains today. Moreover, Earth was oxygen-rich, as today. Today, a tiny part of the oxygen is free, as air; then the oxygen would have been in the mantle while the surface oxygen was used to handcuff the hydrogen as dihydrogen monoxide. Oxygen dihydride is dense, unlikely to fly off to space, and at the poles, rock-forming. Of all the geochemical features that make Earth unique, the initial degassing (Genesis 2 : b) and then the sustained presence of liquid water is the defining oddity of this planet. Early Earth probably also kept much of its carbon, nitrogen, and sulfur as oxide or hydride. And, after the most cataclysmic events had passed, ˜4.5 Ga

  15. Early Literacy Instruction for the New Millennium.

    ERIC Educational Resources Information Center

    Hammond, W. Dorsey, Ed.; Raphael, Taffy E., Ed.

    Noting that early reading achievement is increasingly being named as a top priority in venues ranging from national policy arenas to local schools and school districts, this book consolidates and summarizes research on early reading achievement, making it accessible to parents, teachers, administrators, and others concerned with children's reading…

  16. Early Stuttering, Temperament and Anxiety: Two Hypotheses

    ERIC Educational Resources Information Center

    Kefalianos, Elaina; Onslow, Mark; Block, Susan; Menzies, Ross; Reilly, Sheena

    2012-01-01

    Purpose: The topic of temperament and early stuttering and the extent to which it involves anxiety is theoretically and clinically relevant. The topic can contribute to theory development and clinical practices with early stuttering. Method: We present a review of the empirical literature for this area with a view to determining which of two…

  17. International Early Childhood Resources from ERIC.

    ERIC Educational Resources Information Center

    International Journal of Early Years Education, 1999

    1999-01-01

    Presents annotated bibliography of recent ERIC documents/journal articles providing international early-childhood resources. Topics of documents include day care and infant attachment, multicultural child care, drug-use prevention, and early language learning. Journal article topics include very able preschoolers, children's causality beliefs,…

  18. The Intangibles in the Early Childhood Classroom

    ERIC Educational Resources Information Center

    Hillman, Carol B.

    2012-01-01

    The early years are such formative years, when attitudes are being created, when habits are taking shape, when thoughts are being crystallized. This is when the very essence of each child is coming into being. These are the intangibles that educators may look for within early childhood settings. They must look towards the child care centers around…

  19. Pretend Play in the Early Childhood Classroom

    ERIC Educational Resources Information Center

    McEntire, Nancy

    2009-01-01

    This article presents and summarizes recent resources related to pretend play in the early childhood classroom. These include "Contemporary Perspectives on Play in Early Childhood Education" by Olivia N. Sarachoe and Bernard Spodek; "Dramatic Play: Bring It Back" by Tammy Benson; and "The Importance of Being Playful" by Elena Bodrova and Deborah…

  20. Navigating the State Early Childhood Process

    ERIC Educational Resources Information Center

    Lovejoy, Anna; Clothier, Steffanie

    2006-01-01

    There are four main avenues by which state policy decisions are made: legislation, executive order, administrative rules, and agency budgets. Each process offers many access points for early childhood practitioners and researchers to influence important decisions in the state. The authors provide seven tips for early childhood professionals to…