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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. PMID:11538384

  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. Early Archaean rocks of Sarmatia

    NASA Astrophysics Data System (ADS)

    Shumlyanskyy, Leonid; Claesson, Stefan; Bibikova, Elena; Billström, Kjell

    2013-04-01

    Sarmatia, one of the three main crustal segments of the Precambrian East-European platform, comprises the Ukrainian shield and the Voronezh crystalline massif which are separated by the Late Palaeozoic Dnieper-Donets Depression. It is composed of a collage of terrains that were formed during over 2 billion years, from c. 3.8 to c. 1.7 Ga; some of these terrains can be traced across the Dnieper-Donets Depression. Geochronological and isotope-geochemical investigations have shown that significant portions of Sarmatia were formed already in the Early Archaean. In the Ukrainian shield Early Archaean rocks are known from the Dniester-Bug and Azov domains. Enderbites of the Dniester-Bug Series, which occur intercalated with mafic and ultramafic rocks, contain zircons as old as 3.75-3.78 Ga (Claesson et al., 2006; 2012) while initial Hf isotope ratios indicate derivation from mildly depleted sources. In the Azov domain the oldest rocks known belong to the Novopavlivka complex, which includes orthogneisses, enderbites, migmatites and related granites with up to 1 m thick enclaves of pyroxenite and peridotite, amphibolites, and schists. Zircons separated from two pyroxenite samples have yielded ages of 3633 ± 16 and 3640 ± 11 Ma, while zircons from enderbite gave 3609 ± 5 Ma (Bibikova and Williams, 1990). Zircons extracted from metasediments of the Soroki and Fedorivka greenstone belts, Azov domain, have yielded ages up to 3785 Ma (Bibikova et al, 2010) and ɛHf values of -1.6 to 1.8 for the oldest zircons. Finally, recent multigrain U-Pb dating of heavily deformed tonalitic gneisses of the Verkhnyotokmakska Stratum, Azov Domain, has given an age of 3560 ± 70 Ma (Scherbak et al., 2011). The oldest rocks of the Voronezh crystalline massif belong to the Oboyan Complex which is composed of mafic igneous rocks and sediments metamorphosed into amphibolites and gneisses. Most probably, this complex includes rocks of different ages and origins. Individual igneous zircons from

  5. Recognising early Archaean mantle: a reappraisal

    NASA Astrophysics Data System (ADS)

    Rollinson, Hugh

    2007-09-01

    This paper examines 3.8 Ga peridotites from Greenland and Labrador to test claims that these samples are unmodified early Archaean mantle. Geochemical criteria were applied in which samples were compared to the mantle array in Mg/Si versus Al/Si (wt%) space, their REE patterns were compared to those of different mantle types and their chromite compositions were compared to mantle chromite compositions as expressed by their cr# and fe#. Geochemical data were used from the previously published works of Friend et al. (2002) and Bennett et al. (2002). Only two samples, from the region south of Isua satisfied all criteria, indicating that the area south of the Isua Greenstone Belt in west Greenland is a suitable place to search for early Archaean mantle. This study also confirms the observation by Friend et al. (2002) that early Archaean mantle from south of Isua is of a different character from Archaean mantle from the subcontinental lithosphere. Calculations presented here show that some mantle fragments from south of Isua experienced a lower degree of melt extraction and were probably more oxidising than early Archaean mantle preserved in the subcontinental lithosphere. Elemental concentrations of Os in early Archaean mantle are lower than the new estimate for the primitive upper mantle of Becker et al. (2006). Peridotites from the Isua greenstone belt are not mantle, but have an affinity with the layered intrusions found south of Isua.

  6. Geochemical evolution of magmatism in Archean granite-greenstone terrains

    NASA Astrophysics Data System (ADS)

    Samsonov, A. V.; Larionova, Yu. O.

    2006-05-01

    Evolution of Archean magmatism is one of the key problems concerning the early formation stages of the Earth crust and biosphere, because that evolution exactly controlled variable concentrations of chemical elements in the World Ocean, which are important for metabolism. Geochemical evolution of magmatism between 3.5 and 2.7 Ga is considered based on database characterizing volcanic and intrusive rock complexes of granite-greenstone terrains (GGT) studied most comprehensively in the Karelian (2.9-2.7 Ga) and Kaapvaal (3.5-2.9 Ga) cratons and in the Pilbara block (3.5-2.9 Ga). Trends of magmatic geochemical evolution in the mentioned GGTs were similar in general. At the early stage of their development, tholeiitic magmas were considerably enriched in chalcophile and siderophile elements Fe2O3, MgO, Cr, Ni, Co, V, Cu, and Zn. At the next stage, calc-alkaline volcanics of greenstone belts and syntectonic TTG granitoids were enriched in lithophile elements Rb, Cs, Ba, Th, U, Pb, Nb, La, Sr, Be and others. Elevated concentrations of both the “crustal” and “mantle-derived” elements represented a distinctive feature of predominantly intrusive rocks of granitoid composition, which were characteristic of the terminal stage of continental crust formation in the GGTs, because older silicic rocks and lithospheric mantle were jointly involved into processes of magma generation. On the other hand, the GGTs different in age reveal specific trends in geochemical evolution of rock associations close in composition and geological position. First, the geochemical cycle of GGT evolution was of a longer duration in the Paleoarchean than in the Meso-and Neoarchean. Second, the Paleoarche an tholeiitic associations had higher concentrations of LREE and HFSE (Zr, Ti, Th, Nb, Ta, Hf) than their Meso-and Neoarchean counterparts. Third, the Y and Yb concentrations in Paleoarchean calc-alkaline rock associations are systematically higher than in Neoarchean rocks of the same type

  7. 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

  8. Qingyuan high-grade granite-greenstone terrain in the Eastern North China Craton: Root of a Neoarchaean arc

    NASA Astrophysics Data System (ADS)

    Peng, Peng; Wang, Chong; Wang, Xinping; Yang, Shuyan

    2015-11-01

    The Qingyuan high-grade granite-greenstone terrain is one of the first recognized granite-greenstone terrains in the Eastern North China Craton. Similar to other Archaean terrains, its tectonic environment is debated: was it an intra-continental rift or a modern analogy of arc? Occurrence and petrogenesis of major igneous series, the ultramafic-mafic and felsic volcanic rocks (> 2510 Ma) and the plutons of the quartz diorite (2570-2510 Ma), TTG (2570-2510 Ma) and quartz monzodiorite (2510-2490 Ma) series in Xinbin area are investigated. The mafic intrusives and volcanic rocks have high MgO content (5.4-7.5 wt.%) and Mg-number (48-61). They show slightly depleted to flat trace element patterns. The ultramafic rocks (serpentinite) could be genetically related to the mafic rocks. The meta-dacite-rhyolite is adakitic with enriched light and middle REEs and LILEs, but significantly depleted HFSEs. The quartz diorite has high Mg-number (60-64), moderately enriched light and middle REEs and LILEs. The TTG shows distinct light but moderate middle REE-enrichment, prominent Nb-Ta-depletion but Zr-Hf-enrichment (Zr/Sm > 100). The quartz monzodiorite has moderate light and middle REE-enrichment, significant Nb-Ta-depletion, and negative Eu-/Sr-anomalies. The TTG has more depleted Sr-Nd isotopes (εNdt = + 2-+ 6; 87Sr/86Srt = ~ 0.700) than all the others (εNdt = 0-+ 2; 87Sr/86Srt = 0.701-703). Their petrogenesis can be explained by an Archaean-style subduction defined as a mantle wedge-absent flat-'hot'-subduction with significant vertical tectonism in the overriding slab: the ultramafic-mafic rocks were originated from primitive mantle; the meta-dacite-rhyolite was originated from the eclogite facies overriding crust; the quartz diorite was a mixture of melts from mantle and the overriding crust; the TTG was from the subducting slab under amphibolite to amphibole-bearing eclogite facies; and the quartz monzodiorite was from the subducting slab after the derivation of the TTG

  9. 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.

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

    PubMed

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

    2003-10-01

    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. PMID:14534583

  11. 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

  12. Mesoarchean sanukitoid rocks of the Rio Maria Granite-Greenstone Terrane, Amazonian craton, Brazil

    NASA Astrophysics Data System (ADS)

    de Oliveira, Marcelo Augusto; Dall'Agnol, Roberto; Althoff, Fernando Jacques; da Silva Leite, Albano Antonio

    2009-02-01

    The Archean sanukitoid Rio Maria Granodiorite yielded zircon ages of ˜2.87 Ga and is exposed in large domains of the Rio Maria Granite-Greenstone Terrane, southeastern Amazonian craton. It is intrusive in the greenstone belts of the Andorinhas Supergroup, in the Arco Verde Tonalite and Caracol Tonalitic Complex (older TTGs). Archean potassic leucogranites, younger TTGs and the Paleoproterozoic granites of Jamon Suite are intrusive in the Rio Maria Granodiorite. The more abundant rocks of the Rio Maria Granodiorite have granodioritic composition and display medium to coarse even-grained textures. These rocks show generally a gray color with greenish shades due to strongly saussuritized plagioclase, and weak WNW-ESE striking foliation. The significant geochemical contrasts between the occurrences of Rio Maria Granodiorite in different areas suggest that this unit corresponds in fact to a granodioritic suite of rocks derived from similar but distinct magmas. Mingling processes involving the Rio Maria Granodiorite and similar mafic to intermediate magmas are able to explain the constant occurrence of mafic enclaves in the granodiorite. The associated intermediate rocks occur mainly near Bannach, where mostly quartz diorite and quartz monzodiorite are exposed. The dominant rocks are mesocratic, dark-green rocks, with fine to coarse even-grained texture. The Rio Maria Granodiorite and associated intermediate rocks show similar textural and mineralogical aspects. They follow the calc-alkaline series trend in some diagrams. However, they have high-Mg#, Cr, and Ni conjugate with high contents of large ion lithophile elements (LILEs), typical of sanukitoids series. The patterns of rare earth elements of different rocks are similar, with pronounced enrichment in light rare earth elements (LREEs) and strong to moderate fractionation of heavy rare earth elements (HREEs). Field aspects and petrographic and geochemical characteristics denote that the granodiorites and

  13. The gold content of some Archaean rocks and their possible relationship to epigenetic gold-quartz vein deposits

    NASA Astrophysics Data System (ADS)

    Meyer, M.; Saager, R.

    1985-10-01

    Gold mineralization in Archaean granite-greenstone environments, especially gold-quartz veins, contributes considerably to the world's gold production. The formation of epigenetic gold mineralization in greenstone belts is generally explained by the metamorphic secretion theory. This theory is based on the assumption that the source of the gold may be komatiitic or tholeiitic lavas, pyritic chemical or clastic sediments and even granitic rocks from which, as a result of regional metamorphic overprinting, gold was extracted and concentrated in suitable structures. It has been shown that in proposed potential source rocks, gold is predominantly associated with sulfide minerals and thus relatively easily accessible to secretion and reconstitution processes. A large number of various rock types originating from granite-greenstone terranes of the Kaapvaal and the Rhodesian cratons were geochemically investigated, and the following ranges for gold determined: volcanic rocks (komatiitic and tholeiitic): 0.1 372 ppb granitic rocks of the basement: 0.3 7.8 ppb iron-rich chemical sediments: 1.0 667 ppb Statistical treatment of the data reveals that volcanic rocks as well as iron-rich chemical sediments are favorable sources for epigenetic gold mineralization formed by metamorphic secretion, while the granitic rocks make less suitable primary gold sources. This finding explains the close spatial relationship which is common between gold-quartz veins and greenstone belts. The conspicuous abundance of epigenetic gold mineralization in the Archaean, however, is attributed to the unique geologic and metamorphic history of the granite-greenstone terranes.

  14. Visible and infrared properties of unaltered to weathered rocks from Precambrian granite-greenstone terrains of the West African Craton

    NASA Astrophysics Data System (ADS)

    Metelka, Václav; Baratoux, Lenka; Jessell, Mark W.; Naba, Séta

    2015-12-01

    In situ and laboratory 0.35 μm-2.5 μm spectra of rocks from a Paleoproterozoic granite-greenstone terrain along with its Neoproterozoic sedimentary cover and derived regolith materials were examined in western Burkina Faso. The reflectance spectra show the influence of typical arid to semi-arid weathering with the formation of desert varnish, iron films, and dust coatings. Fe and Mg-OH absorption features related to chlorite, amphibole, pyroxene, epidote, and biotite are observable in the mafic and intermediate meta-volcanic rocks as well as in the granodiorites and tonalites. Al-OH absorption caused by kaolinite, smectite, illite/muscovite are typical for meta-volcano-sedimentary schists, Tarkwaian-type detrital meta-sediments, sandstones of the Taoudeni basin, all of the weathered surfaces and regolith materials. Ferric and ferrous iron absorptions related to both primary rock-forming minerals and secondary weathering minerals (goethite, hematite) were observed in most of the sampled materials. The results show that although weathering alters the spectral signature of the fresh rock, indicative absorption features located in the short wave infrared region remain detectable. In addition, spectra of soils partially reflect the mineral composition of the weathered rock surfaces. The analysis of the hyperspectral data shows the potential of differentiating between the sampled surfaces. The library presents a primary database for the geological and regolith analysis of remote sensing data in West Africa.

  15. Pb isotopic evidence for early Archaean crust in South Greenland

    NASA Astrophysics Data System (ADS)

    Taylor, P. N.; Kalsbeek, F.

    The results of an isotopic remote sensing study focussed on delineating the extent of Early Archean crust north and south of the Nuuk area and in south Greenland is presented. Contamination of the Late Archean Nuk gneisses and equivalents by unradiogenic Pb uniquely characteristic of Amitsoq gneiss was detected as far south as Sermilik about 70 km south of Nuuk and only as far north as the mouth of Godthabsfjord. This study was extended to the southern part of the Archean craton and the adjoining Early Proterozoic Ketilidian orogenic belt where the Pb isotopes suggest several episodes of reworking of older uranium depleted continental crust. The technique of using the Pb isotope character of younger felsic rocks, in this case Late Archean and Early Proterozoic gneisses and granites to sense the age and isotopic character of older components, is a particularly powerful tool for reconstructing the evolutionary growth and development of continental crust.

  16. Pb isotopic evidence for early Archaean crust in South Greenland

    NASA Technical Reports Server (NTRS)

    Taylor, P. N.; Kalsbeek, F.

    1986-01-01

    The results of an isotopic remote sensing study focussed on delineating the extent of Early Archean crust north and south of the Nuuk area and in south Greenland is presented. Contamination of the Late Archean Nuk gneisses and equivalents by unradiogenic Pb uniquely characteristic of Amitsoq gneiss was detected as far south as Sermilik about 70 km south of Nuuk and only as far north as the mouth of Godthabsfjord. This study was extended to the southern part of the Archean craton and the adjoining Early Proterozoic Ketilidian orogenic belt where the Pb isotopes suggest several episodes of reworking of older uranium depleted continental crust. The technique of using the Pb isotope character of younger felsic rocks, in this case Late Archean and Early Proterozoic gneisses and granites to sense the age and isotopic character of older components, is a particularly powerful tool for reconstructing the evolutionary growth and development of continental crust.

  17. Early Archaean microorganisms preferred elemental sulfur, not sulfate.

    PubMed

    Philippot, Pascal; Van Zuilen, Mark; Lepot, Kevin; Thomazo, Christophe; Farquhar, James; Van Kranendonk, Martin J

    2007-09-14

    Microscopic sulfides with low 34S/32S ratios in marine sulfate deposits from the 3490-million-year old Dresser Formation, Australia, have been interpreted as evidence for the presence of early sulfate-reducing organisms on Earth. We show that these microscopic sulfides have a mass-independently fractionated sulfur isotopic anomaly (Delta33S) that differs from that of their host sulfate (barite). These microscopic sulfides could not have been produced by sulfate-reducing microbes, nor by abiologic processes that involve reduction of sulfate. Instead, we interpret the combined negative delta34S and positive Delta33S signature of these microscopic sulfides as evidence for the early existence of organisms that disproportionate elemental sulfur. PMID:17872441

  18. Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks

    NASA Astrophysics Data System (ADS)

    Ohtomo, Yoko; Kakegawa, Takeshi; Ishida, Akizumi; Nagase, Toshiro; Rosing, Minik T.

    2014-01-01

    Some graphite contained in the 3.7-billion-year-old metasedimentary rocks of the Isua Supracrustal Belt, Western Greenland, is depleted in 13C and has been interpreted as evidence for early life. However, it is unclear whether this graphite is primary, or was precipitated from metamorphic or igneous fluids. Here we analyse the geochemistry and structure of the 13C- depleted graphite in the Isua schists. Raman spectroscopy and geochemical analyses indicate that the schists are formed from clastic marine sediments that contained 13C-depleted carbon at the time of their deposition. Transmission electron microscope observations show that graphite in the schist occurs as nanoscale polygonal and tube-like grains, in contrast to abiotic graphite in carbonate veins that exhibits a flaky morphology. Furthermore, the graphite grains in the schist contain distorted crystal structures and disordered stacking of sheets of graphene. The observed morphologies are consistent with pyrolysation and pressurization of structurally heterogeneous organic compounds during metamorphism. We thus conclude that the graphite contained in the Isua metasediments represents traces of early life that flourished in the oceans at least 3.7billion years ago.

  19. 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).

  20. Early Earth Felsic Crust Formation: Insights from Numerical Modelling of High-MgO Archaean Basalt Partial Melting

    NASA Astrophysics Data System (ADS)

    Riel, N., Jr.

    2015-12-01

    The Tonalite-Trondhjemite-Granodiorite series (TTGs) represent the bulk of the felsic continental crust that formed between 4.4 and 2.5 Ga and is preserved in Archaean craton (3.8-2.5 Ga). It is now recognized that the petrogenesis of TTG series derives from an hydrous mafic system at high pressure. However, the source of the early TTGs (3.5-3.2 Ga) have not been preserved and its characteristics are still debated. In this study we use thermodynamical modelling coupled with two-phase flow to investigate the products of partial melting of high-MgO primary mafic crust. Our model setup is made of a 45-km thick hydrated mafic crust and is heated above the solidus from 50 to 200°C. To explore the effects of melt-rock interactions during melt transfer (via two-phase flow), the melt composition is modelled either in thermodynamic equilibrium with the rock or in thermodynamic disequilibrium. Our modelling results show that partial melting of hydrous high-MgO metabasalt crust can produce significant volumes of felsic melt. The average composition of these melts is SiO2-rich > 62%, Mg# = 40-50, Na2O ~6%, MgO = 0.5-1% which is consistent with the composition of TTGs. The residual rock after melt segregation is composed of olivine + garnet + pyroxene which is in agreement with Archaean eclogites found in mantle xenoliths of Archaean cratons. Moreover, the depleted residual rock is denser than the mantle and is likely to be recycled in the mantle. We show that the early felsic crust with a TTGs signature could have been formed by partial melting of high-MgO hydrated metabasaltic crust, and propose that plume-related activity and/or rapid burial due to high volcanic activity are likely geodynamic conditions to generate an early felsic crust.

  1. 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

  2. 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.

  3. Generation of early Archaean felsic greenstone volcanic rocks through crustal melting in the Kaapvaal, craton, southern Africa

    NASA Astrophysics Data System (ADS)

    Kröner, Alfred; Elis Hoffmann, J.; Xie, Hangqiang; Wu, Fuyuan; Münker, Carsten; Hegner, Ernst; Wong, Jean; Wan, Yusheng; Liu, Dunyi

    2013-11-01

    High-potassium felsic volcanic rocks interlayered with basalt and komatiite in early Archaean greenstone sequences in the Barberton Greenstone Belt of South Africa and Swaziland, previously considered to be derived from melting of mafic precursors, are shown to be the result of melting of significantly older felsic crust. This is documented by a combination of SHRIMP zircon dating with Hf-in-zircon and whole-rock Lu-Hf and Sm-Nd isotopic data. Zircons from felsic rocks of the oldest Barberton unit, the 3.53 Ga Theespruit Formation, yielded predominantly negative ɛ-values, whereas whole-rock ɛ- and ɛ-data are slightly negative to slightly positive. Similar results were obtained for ca. 3.45 Ga felsic rocks in the Hoeggenoog and Noisy Formations higher up in the greenstone stratigraphy. These data rule out derivation of the felsic units from melting of basaltic precursors and favor a crustal source, most likely of TTG composition. The isotopic data are not compatible with an entirely oceanic origin of the Barberton greenstone sequences and favor a pre-greenstone basement beneath the volcanic rocks. Crustal melting of Eo- to Paleoarchaean lower crust probably generated the felsic volcanic rocks and is likely to have been responsible for gradual stabilization of the Kaapvaal craton.

  4. Extraterrestrial Impact Episodes and Archaean to Early Proterozoic (3.8 2.4 Ga) Habitats of Life

    NASA Astrophysics Data System (ADS)

    Glikson, Andrew

    The terrestrial record is punctuated by major clustered asteroid and comet impacts, which affected the appearance, episodic extinction, radiation, and reemergence of biogenic habitats. Here I examine manifest and potential extraterrestrial impact effects on the onset and evolution of Archaean to early Proterozoic (3.8- 2.4-Ga) habitats, with reference to the Pilbara (Western Australia) and Kaapvaal (eastern Transvaal) Cratons. The range of extraterrestrial connections of microbial habitats includes cometary contribution of volatiles and amino acids, sterilization by intense asteroid and comet bombardment, supernova and solar flares, and impacttriggered volcanic and hydrothermal activity, tectonic modifications, and tsunami effects. Whereas cometary dusting of planetary atmosphere may contribute littlemodi fied extraterrestrial organic components, large impact effects result in both incineration of organic molecules and shock synthesis of new components. From projected impact incidence, ~1.3% of craters >100 km and ~3.8% of craters >250 km have to date been identified for post-3.8-Ga events, due to the mm-scale of impact spherules and the difficulty in their identification in the field - only the tip of the iceberg is observed regarding the effects of large impacts on the Precambrian biosphere, to date no direct or genetic relations between impacts and the onset or extinction of early Precambrian habitats can be confirmed. However, potential relations include (1) ~3.5-3.43 Ga - intermittent appearance of stromatolite-like structures of possible biogenic origin on felsic volcanic shoals representing intervals between mafic volcanic episodes in rapidly subsiding basins, a period during which asteroid impacts are recorded; (2) ~3.26-3.225 Ga - impact-triggered crustal transformation from mafic-ultramafic volcanic environments to rifted troughs dominated by felsic volcanics and turbidites, marked by a major magmatic peak, resulting in extensive hydrothermal activity and

  5. 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.

  6. 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.

  7. 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.

  8. Tectonics of the Kola collision suture and adjacent Archaean and Early Proterozoic terrains in the northeastern region of the Baltic Shield

    NASA Astrophysics Data System (ADS)

    Berthelsen, Asger; Marker, Mogens

    1986-06-01

    As preparation for the deep-seismic and other geophysical experiments along the Polar Profile, which transects the Granulite belt and the Kola collision suture, structural field work has been performed in northernmost Finland and Norway, and published geological information including data from the neighbouring Soviet territory of the Kola Peninsula, have been compiled and reinterpreted. Based on these studies and a classification according to crustal and structural ages, the northeastern region of the Baltic Shield is divided into six major tectonic units. These units are separated and outlined by important low-angle, ductile shear or thrust zones of Late Archaean to Early Proterozoic age. The lateral extension of these units into Soviet territory and their involvement in large-scale crustal deformation structures, are described. Using the "view down the plunge" method, a generalised tectonic cross-section that predicts the crustal structures along the Polar Profile is compiled, and the structures around the Kola deep drill-hole are reinterpreted. The Kola suture belt, through parts of which the Kola deep bore-hole has been drilled, is considered to represent a ca. 1900 Ma old arc-continent and continent-continent collision suture. It divides the northeastern Shield region into two major crustal compartments: a Northern compartment (comprising the Murmansk and Sörvaranger units) and a Southern compartment (including the Inari unit, the Granulite belt and the Tanaelv belt, as well as the more southernly situated South Lapland-Karelia "craton" of the Karelian province of the Svecokarelian fold belt). The Kola suture belt is outlined by a 2-40 km wide and ca. 500 km long crustal belt composed of (1) Early Proterozoic (ca. 2400-2000 Ma old) metavolcanic and metasedimentary sequences which originally formed part of the attenuated margin of the Northern Archaean compartment, and (2) the remains of a ca. 2000-1900 Ma old, predominantly andesitic island-arc terrain. This

  9. The U-Pb, Hf and O isotopic record of ancient detrital zircons in Zimbabwean sediments - formation, reworking and nature of early Archaean crust

    NASA Astrophysics Data System (ADS)

    Bolhar, Robert; Hofmann, Axel; Kemp, Anthony I. S.; Whitehouse, Martin J.; Wind, Sandra; Feng, Yuexing

    2014-05-01

    Hafnium and oxygen isotopic compositions measured in-situ on U-Pb dated zircon from different Archaean sedimentary successions belonging to the 2.9-2.8 Ga Belingwean/Bulawayan Groups and undated Sebakwian Group are presented to better define the crustal evolution of the Zimbabwe Craton prior to 3.0 Ga. Textural and compositional criteria were employed to minimize effects arising from Pb loss, metamorphic overprinting and interaction with low temperature fluids. 207Pb/206Pb age spectra (concordance > 90%) reveal prominent peaks at 3.8, 3.6, 3.5, and 3.35 Ga, corresponding to documented geological events both globally and within the Zimbabwe craton. O isotope compositions of ~ 4 - 10 opoint to both derivation from magmas in equilibrium with mantle and the assimilation of supracrustal material or interaction with metamorphic fluids. In ɛHf-time space, 3.8-3.6 Ga grains define an array consistent with derivation from a mafic to intermediate source reservoir (Lu/Hf ~0.015) that separated from chondritic mantle at ~ 3.9 Ga. Crustal domains formed after 3.6 Ga depict a more complex evolution, involving contribution from juvenile mantle sources and reworking of pre-existing crust. Importantly, initial Hf isotopic compositions document a protracted history of remelting, without evidence for significant mantle depletion prior to 3.35 Ga. This suggests that production of earliest crust in the Zimbabwe Craton did not cause complementary enriched and depleted reservoirs, possibly because heterogeneous mantle was effectively remixed by rapid convection due to higher temperatures in the early Archaean or the volume of crust was too small in volume to influence the isotopic mantle evolution. Similar Hf-O-time relationships observed in southern West Greenland were used as a basis to propose a transition in geodynamics 3.2 Ga ago. The absence of detrital zircons with crystallization ages > 3.8 Ga, along with a simple ɛHf-time array consistent with reworking of a mafic protolith

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  12. Silicon isotope and trace element constraints on the origin of ˜3.5 Ga cherts: Implications for Early Archaean marine environments

    NASA Astrophysics Data System (ADS)

    van den Boorn, S. H. J. M.; van Bergen, M. J.; Vroon, P. Z.; de Vries, S. T.; Nijman, W.

    2010-02-01

    Silicon (Si) isotope variability in Precambrian chert deposits is significant, but proposed explanations for the observed heterogeneity are incomplete in terms of silica provenance and fractionation mechanisms involved. To address these issues we investigated Si isotope systematics, in conjunction with geochemical and mineralogical data, in three well-characterised and approximately contemporaneous, ˜3.5 Ga chert units from the Pilbara greenstone terrane (Western Australia). We show that Si isotope variation in these cherts is large (-2.4‰ to +1.3‰) and was induced by near-surface processes that were controlled by ambient conditions. Cherts that formed by chemical precipitation of silica show the largest spread in δ 30Si (-2.4‰ to +0.6‰) and are characterised by positive Eu, La and Y anomalies and overall depletions in lithophile trace elements. Silicon isotope systematics in these orthochemical deposits are explained by (1) mixing between hydrothermal fluids and seawater, and/or (2) fractionation of hydrothermal fluids by subsurface losses of silica due to conductive cooling. Rayleigh-type fractionation of hydrothermal fluids was largely controlled by temperature differences between these fluids and seawater. Lamina-scale Si isotope heterogeneity within individual chemical chert samples up to 2.2‰ is considered to reflect the dynamic nature of hydrothermal activity. Silicified volcanogenic sediments lack diagnostic REE+Y anomalies, are enriched in lithophile elements, and exhibit a much more restricted range of positive δ 30Si (+0.1‰ to +1.1‰), which points to seawater as the dominant source of silica. The proposed model for Si isotope variability in the Early Archaean implies that chemical cherts with the most negative δ 30Si formed from pristine hydrothermal fluids, whereas silicified or chemical sediments with positive δ 30Si are closest to pure seawater deposits. Taking the most positive value found in this study (+1.3‰), and assuming that

  13. Lithostratigraphy and structure of the early Archaean Doolena Gap Greenstone Belt, East Pilbara Terrane (EPT), Western Australia

    NASA Astrophysics Data System (ADS)

    Wiemer, D.; Schrank, C. E.; Murphy, D. T.

    2014-12-01

    We present a detailed lithostratigraphic and structural analysis of the Archean Doolena Gap greenstone belt to shed light on the tectonic evolution of the EPT. The study area is divided into four structural domains: i) marginal orthogneisses of the MGC (Muccan Granitoid Complex), ii) a dominantly mafic mylonitic shear zone (South Muccan Shear Zone, SMSZ) enveloping the MGC, iii) a Central Fold Belt of dominantly mafic greenschists (CFB), and iv) a lower greenschist- to sub-greenschist southern domain. Toward the dome margin, abrupt increases in deformation intensity occur across domain boundaries. Domain boundaries and intra-domain shear zones are marked by significant carbonate +/- quartz alteration and high-strain non-coaxial deformation with dome-up kinematics. The southern domain comprises pillow basalts of the Mount Ada Formation (MAF), conformably overlain by clastic sediments and minor pillow basalts of the Duffer Formation (DF). The MAF and DF are overlain by an up to 1km thick package of quartzite (Strelley Pool Formation) across an angular unconformity. Isoclinal folds (F2) within the CFB to the North deform an early foliation (S1) within dominantly mafic schists and associated carbonate veins. F2 folds are preserved within lozenges that are parallel to the axial planes of F2 folds in a regional E-W trending foliation (S2) and to the SMSZ. Lozenges are often bound by zones of significant carbonate alteration. The lozenges are folded recumbently (F3), with sub-vertical fold axes pointing towards the dome. The F3 axes are parallel to mineral stretching lineations on S2 indicating dome-up movement. The entire belt is cut by late NE-SW-striking faults that exhibit dominantly brittle deformation in the southern domain but ductile drag folding (F4) in the CFB. Therefore, the southern domain must have overlain the CFB during this D4 event. We propose a protracted structural history of the greenstone belt where successive deformation events relate to the episodic

  14. 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

  15. 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. PMID:20516134

  16. 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

  17. 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

  18. 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. PMID:16754603

  19. The Archaean sanukitoid series of the Baltic Shield: geological setting, geochemical characteristics and implications for their origin

    NASA Astrophysics Data System (ADS)

    Lobach-Zhuchenko, S. B.; Rollinson, H. R.; Chekulaev, V. P.; Arestova, N. A.; Kovalenko, A. V.; Ivanikov, V. V.; Guseva, N. S.; Sergeev, S. A.; Matukov, D. I.; Jarvis, K. E.

    2005-01-01

    Archaean high-Mg granitoids (sanukitoids) occur in the Karelian granite-greenstone terrain in the Baltic Shield in two distinct zones. In the west of the Shield sanukitoid intrusions formed between 2700 and 2720 Ma and consist of a single igneous phase that varies in composition from diorite to granite. In the Eastern part of the Shield, sanukitoid intrusions formed between 2730 and 2745 Ma and are strongly differentiated, varying in composition from ultramafic to felsic. All the sanukitoids are enriched in light rare earth elements (LREE: La≤80 ppm, Ce≤150 ppm, La N/Yb N≤30-40), Sr≤2000 ppm, Ba≤2500 ppm, P 2O 5≤1.5%, alkalis (Na 2O+K 2O=5-10%), possess high mg# values (0.50-0.65), and show a negative Nb-Ta anomaly. They are spatially and temporally related to syenite intrusions and lamprophyre dykes. Sanukitoid intrusions in the Western and Eastern zones differ in composition. In the west, they have higher SiO 2 (mainly>60%) and lower alkalis, Sr, Ba, LREE than in the Eastern zone intrusions. The most differentiated intrusion, the Panozero intrusion in the Eastern zone, was formed in two magmatic cycles separated by ductile deformation. In the first cycle, ultramafic to monzonitic rocks formed, whereas, in the second cycle, the magmas were monzodioritic to quartz monzonite. Ultramafic and mafic rocks make up about 10% of the outcrop and occur as enclaves in monzonites and monzodiorites, and, as dykes, implies a number of discrete magmatic events. All rocks of the Panozero intrusion have high K 2O, and the composition of the initial melt, calculated from the weighted average of the first cycle magmas is monzodiorite (SiO 2=52%, mg#=0.55, Na 2O+K 2O˜6%). The presence of magmatic hornblende and biotite, a high carbonate content, widely distributed explosive breccias and evidence of liquid immiscibility are consistent with a high H 2O-CO 2 content in the sanukitoid melt. The geodynamic model which most satisfactorily explains our geological and

  20. 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.

  1. 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. PMID:12529633

  2. Geochemistry and U-Pb zircon ages of plutonic rocks from the Algodões granite-greenstone terrane, Troia Massif, northern Borborema Province, Brazil: Implications for Paleoproterozoic subduction-accretion processes

    NASA Astrophysics Data System (ADS)

    Costa, Felipe Grandjean da; Palheta, Edney Smith de Moraes; Rodrigues, Joseneusa Brilhante; Gomes, Iaponira Paiva; Vasconcelos, Antonio Maurilio

    2015-04-01

    The Algodões metavolcano-sedimentary sequence is located at the northern margin of the Archean/Paleoproterozoic Troia Massif, northern Borborema Province (NE Brazil). It represents a well-preserved Paleoproterozoic greenstone-like sequence affected by two major plutonic events. The early plutonism, represented by the Cipó orthogneisses, mainly comprises biotite-bearing metatonalites, which share similar geochemical signatures with Archean tonalite-trondjhemite-granodiorite (TTG). For these rocks, we report U-Pb (LA-ICPMS) zircon ages of 2189 ± 14 Ma and 2180 ± 15 Ma. A subsequent plutonic magmatism occurred at ˜2150-2130 Ma and is mainly represented by hornblende-bearing dioritic to tonalitic orthogneisses of the Madalena Suite and São José da Macaoca Complex. Geochemical data indicate that these dioritic/tonalitic orthogneisses have adakitic characteristics and strongly suggest mantle-related magmas. A (sensu stricto) granite plutonism (Serra da Palha orthogneisses) also intruded the Algodões sequence and yielded U-Pb (LA-ICPMS) zircon age of 2150 ± 16 Ma. These granitic orthogneisses show high-K content, A-type characteristics and probably derived from partial melting of a crustal (tonalitic) source. We suggest that the early ˜2190-2160 Ma TTG plutons probably developed in intra-oceanic arc setting, whereas the following ˜2150-2130 Ma adakitic plutons and A-type granitic magmatism developed in response to arc-continent collision.

  3. The Archaean tonalite-trondhjemite-granodiorite (TTG) series is not an analogue of Cenozoic adakite

    NASA Astrophysics Data System (ADS)

    Smithies, R. H.

    2000-10-01

    The tonalite-trondhjemite-granodiorite (TTG) series comprises silicic and sodic rocks that form a major component of preserved Archaean crust. TTG are widely considered to have formed during subduction by partial melting of hydrated oceanic crust. This hypothesis relies primarily on compositional similarities with Cenozoic subduction-related felsic rocks called adakites. However, simple geochemical parameters, such as silica content and Mg # [=Mg 2+/(Mg 2++Fe Total)×100, with Fe Total as Fe 2+], show that TTG are distinct from adakite. Most adakite suites comprise, or include, high Mg # and low SiO 2 samples which suggest that these slab melts interacted with the mantle, whereas virtually all samples of pre-3.0 Ga TTG, and more than half of the samples of post-3.0 Ga TTG, show no evidence for such interaction. Convincing evidence for a direct mantle component in TTG is primarily restricted to samples from the late Archaean Superior Province of Canada, where there is also independent evidence for subduction and arc-accretion. Consequently, most early Archaean, and many late Archaean, TTG suites are not analogues of Cenozoic adakite. The composition of these TTG suites does not provide evidence for modern-style subduction processes. Tectonic models that accommodate TTG production through melting of hydrous basaltic material at the base of thickened crust may be more appropriate to the Archaean.

  4. 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.

  5. Archaean tectonic systems: a naive geochemist's view

    NASA Astrophysics Data System (ADS)

    Moyen, Jean-François

    2013-04-01

    On a global scale, the geochemistry of common igneous rocks reflects the dominant processes operating on Earth. Therefore, any change in global tectonic patterns should reflect on global geochemical patterns. This work examines the global distribution of Archaean and modern igneous rock's compositions, without relying on preconceptions about the link between rock compositions and tectonic sites (as in "geotectonic" diagrams). Rather, geochemical patterns are interpreted in terms of source and melting conditions; Archaean and modern patterns are compared. The dataset used is extracted from web databases (georoc and petDB), supplemented with the author's own compilation (for granitoids). The igneous rock record for both Archaean and Phanerozoic systems is bimodal, with mafic/ultramafic rocks on one hand (mantle source) and granitic rocks on the other hand (crustal recycling). Ultramafic rocks are rare in modern systems, but common in the Archaean - this is classically interpreted as reflecting a higher degree of melting in a hotter Archaean mantle. Mafic rocks on the modern Earth show a clear separation between "arc" and "non-arc" rocks, depicting for instance two clearly separated, parallel arrays in a Th/Yb vs. Nb/Yb diagram. This points to the first order difference between "wet" (arc) and "dry" (mid-ocean ridges and hotspots) melting of the mantle. Dry melts are further separated in depleted (MORB, high Zr/Nb) and enriched (OIB, low Zr/Nb) sources. This three-fold pattern is a clear image of the ridge/subduction/plume system that dominates modern tectonics. In contrast, Archaean mafic and ultramafic rocks are clustered in an "intermediate" position, between "arc" and non "arc" and between "enriched" and "depleted" components. The distribution is unimodal; Archaean rocks depict a single, oblique array in Th/Yb vs. Nb/Yb, and cluster between the three main modern types in e.g. Zr/Nb vs. Nb/Th. This suggests that the Archaean mantle had lesser amounts of clearly

  6. 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. PMID:27029278

  7. 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.

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

    PubMed

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

    2006-08-01

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

  9. 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.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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 (Δ33S) 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.

  12. 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. PMID:27172047

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The extraordinary stability of remanent magnetisation held in some naturally-occurring ferromagnetic particles implies that even rocks that are billions of years old may record the ambient magnetic field conditions from the time that they formed. Certain rocks from the Barberton Greenstone Belt have demonstrated such a capacity and therefore represent an invaluable resource for palaeomagnetic studies of the early Earth. Here we review the challenges, successes, motivations, and future potential of palaeomagnetic studies applied to Archaean-age rocks in the context of the drill cores recently collected from the Barberton Greenstone Belt. The aims of such studies are two-fold: to study the geomagnetic field itself, and to use the direction of the field as preserved in the rocks to delineate polar wander. The Earth's magnetic field is generated in the core of the planet but also shields the atmosphere from erosion by the solar wind (which was much stronger in the Archaean). Consequently, the geomagnetic application of palaeomagnetism can inform us about conditions both at the surface and in the deep interior of the planet. Notable recent successes in this area include relatively robust observations that convection within the Earth's core was sustaining a stable field that appeared similar in character to today's 3.5 billion years ago and indeed that it was more stable on average 2.5 billion years ago than in the last few hundreds of millions of years. Observations of polar wander are more ambiguous. In the first instance, it is extremely difficult in such old rocks to distinguish apparent polar wander resulting from tectonic drift from that due to "true polar wander" - the motion of the entire crust and mantle relative to the Earth's rotation axis. Nevertheless, both of these are ultimately a consequence of mantle convection and therefore firm constraints on rates of simply "polar wander", would still be a useful constraint on geodynamic processes. Published

  14. Chemistry of the older supracrustals of Archaean age around Sargur

    NASA Technical Reports Server (NTRS)

    Janardhan, A. S.; Shadaksharaswamy, N.; Capdevila, R.

    1988-01-01

    In the Archaeans of the Karnataka craton two stratigraphically distinct volcano-sedimentary sequences occur, namely the older supracrustals of the Sargur type and the younger Dharwar greenstones. The dividing line between these is the 3 by old component of the Peninsular gneiss. The trace and rare earth element chemistry of the Sargur metasediments show, in general, marked similarity to the Archaean sediments. The significant departures are in the nickel and chromium abundances. The REE data of the Sargur pelites of the Terakanambi region represented by Silli-gt-bio-feldspar schists and paragneisses show LREE enrichment and flat to depleted HREE pattern. Banded iron formations have very low REE abundance. They show slightly enriched LREE and flat to depleted HREE pattern. REE abundance in the Mn-horizons is comparable to that of the Archaean sediments. Mn-horizons show enriched LREE and flat HREE with anamolous Eu. REE patterns of these bands is well evolved and has similarities with PAAS.

  15. 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. PMID:20393560

  16. Late Archaean granulite facies metamorphism in the Vestfold Hills, East Antarctica

    NASA Astrophysics Data System (ADS)

    Zulbati, F.; Harley, S. L.

    2007-01-01

    Granulites of the Vestfold Hills record a pulsed end-Archaean to early Palaeoproterozoic M1-M2 evolution that is distinct from other Archaean areas in East Antarctica and cratonic domains placed adjacent to East Antarctica in Gondwana reconstructions. Pressure and temperature conditions of the end-Archaean to earliest Palaeoproterozoic (2501-2496 Ma) M1 granulite facies metamorphism in the Vestfold Hills have been constrained from mineral assemblages and thermobarometry of Fe-rich paragneisses. Reintegrated compositions of exsolved subcalcic clinopyroxenes and pigeonites in a metaironstone yield temperatures of 895 ± 35 °C, whilst reintegrated compositions of perthitic feldspars in semipelitic paragneisses give minimum estimates of 860 ± 30 °C. These results rule out the extreme ultrahigh temperature (UHT) conditions previously proposed for M1 in the Vestfold Hills. Pressures of metamorphism during M1 are estimated as 8.1 ± 0.9 kb at 850 ± 40 °C from hercynite + sillimanite + almandine + corundum and retrieved Fe-Mg-Al relations in orthopyroxene coexisting with garnet. A second metamorphic event, M2, occurred at 600-660 °C and 6-8 kb based on thermometry of recrystallised pyroxene neoblasts and thermobarometry applied to M2 garnet-quartz symplectites formed on orthopyroxene and garnet. The intervening emplacement of the magmatic Crooked Lake Gneiss Group precursors occurred at similar or shallower pressures prior to D2-M2, an event that caused tectonic interleaving and reactivation of the Vestfold Hills basement at mid-crustal depths in the earliest Palaeoproterozoic, prior to its unroofing to shallower levels (3-5 kb) by 2470 Ma. The lack of correlative Archaean histories in areas that were formerly adjacent in Gondwanan reconstructions is consistent with the Vestfold Hills region either being exotic to the East Antarctic Shield until the final (Neoproterozoic to Cambrian) amalgamation of Gondwana, or being accreted to part of East Antarctica in a

  17. 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.

  18. 207Pb-206Pb zircon ages of eastern and western Dharwar craton, southern India : Evidence for contemporaneous Archaean crust

    NASA Astrophysics Data System (ADS)

    Maibam, B.; Goswami, J. N.; Srinivasan, R.

    2009-04-01

    Dharwar craton is one of the major Archaean crustal blocks in the Indian subcontinent. The craton is comprised of two blocks, western and eastern. The western domain is underlain by orthogneisses and granodiorites (ca. 2.9-3.3 Ga) collectively termed as Peninsular Gneiss [e.g., 1] interspersed with older tracts of metasedimentary and metamorphosed igneous suites (Sargur Group and Dharwar Group; [2]). The eastern part of the craton is dominated by Late Archaean (2.50-2.75 Ga) granitoids and their gneissic equivalents. They are interspersed with schist belts (also of Sargur Group and Dharwar Group), which are lithologically similar to the Dharwar Supergroup in the western block, but are in different metamorphic dress. Here we report 207Pb-206Pb age of zircons separated from the metasedimentary and gneissic samples from the two blocks to constrain the evolution of the Dharwar craton during the early Archaean. Detrital zircons of the metasedimentary rocks from both the blocks show a wide range of overlapping ages between ~2.9 to >3.5 Ga. Zircon ages of the orthogneisses from the two blocks showed that most of the analysed grains of the eastern Dharwar block are found to be of the age as old as the western Dharwar gneisses. Imprints of younger events could be discerned from the presence of overgrowths in zircons from the studied samples throughout the craton. Our data suggest that crust forming cycles in the two blocks of the Dharwar craton occurred contemporaneously during the Archaean. References [1] Beckinsale, R.D., Drury, S.A., Holt, R.W. (1980) Nature 283, 469-470. [2] Swami Nath J., Ramakrishnan M., Viswanatha M.N. (1976) Rec. Geol. Surv. Ind., 107, 149-175.

  19. 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

  20. 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.

  1. 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.

  2. Spatial greenstone-gneiss relationships: Evidence from mafic-ultramafic xenolith distribution patterns

    NASA Technical Reports Server (NTRS)

    Glikson, A. Y.

    1986-01-01

    The distribution patterns of mafic-ultramafic xenoliths within Archaean orthogneiss terrain furnish an essential key for the elucidation of granite-greenstone relations. Most greenstone belts constitute mega-xenoliths rather than primary basin structures. Transition along strike and across strike between stratigraphically low greenstone sequences and xenolith chains demonstrate their contemporaneity. These terrains represent least deformed cratonic islands within an otherwise penetratively foliated deformed gneiss-greenstone crust. Whereas early greenstone sequences are invariably intruded by tonalitic/trondhjemitic/granodioritic gneisses, stratigraphically higher successions may locally overlap older gneiss terrains and their entrained xenoliths unconformably. The contiguity of xenolith patterns suggests their derivation as relics of regional mafic-ultramafic volcanic crustal units and places limits on horizontal movements between individual crustal blocks.

  3. 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

  4. 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

  5. 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. PMID:23128231

  6. Pre-biotic organic molecules in hydrothermal quartz veins from the Archaean Yilgarn province, Australia

    NASA Astrophysics Data System (ADS)

    Mayer, Christian; Schreiber, Ulrich; Dyker, Gerald; Kirnbauer, Thomas; Mulder, Ines; Sattler, Tobias; Schöler, Heinfried; Tubbesing, Christoph

    2013-04-01

    result would be the first indication for pre-biotic organic chemistry. In contrast, almost no organic compounds have been detected inside fluid inclusions from impact-generated quartz veins of the Shoemaker-Crater (its geological age is estimated between 1.6 and 1.0 Ga), even though they partially have formed in stromatolite-bearing sedimentary rocks. Some of them occur in Precambrian gneisses. We interpret the absence of organic compounds as a consequence of the different genesis of the quartzes near the Shoemaker-crater: the impact-induced hydrothermal system had no connection to the Earth's mantle and hence, no contact to rising volcanic fluids. Our analytical results prove the presence of complex organic molecules in fluid inclusions trapped in quartz veins from the Archaean Yilgarn craton in Australia. They allow a more detailed understanding of the synthetic processes which have occurred in rising hydrothermal fluids in the upper crust of the earth and which may have led to the formation of early pre-biotic organic molecules. Based on the findings, laboratory experiments will be designed to reproduce these processes and to yield further understanding on their mechanism. Furthermore, they should yield a collection of possible products which may have formed the basis for the first biomolecules in Earth's history.

  7. Percolation of diagenetic fluids in the Archaean basement of the Franceville basin

    NASA Astrophysics Data System (ADS)

    Mouélé, Idalina Moubiya; Dudoignon, Patrick; Albani, Abderrazak El; Cuney, Michel; Boiron, Marie-Christine; Gauthier-Lafaye, François

    2014-01-01

    The Palaeoproterozoic Franceville basin, Gabon, is mainly known for its high-grade uranium deposits, which are the only ones known to act as natural nuclear fission reactors. Previous work in the Kiéné region investigated the nature of the fluids responsible for these natural nuclear reactors. The present work focuses on the top of the Archaean granitic basement, specifically, to identify and date the successive alteration events that affected this basement just below the unconformity separating it from the Palaeoproterozoic basin. Core from four drill holes crosscutting the basin-basement unconformity have been studied. Dating is based on U-Pb isotopic analyses performed on monazite. The origin of fluids is discussed from the study of fluid inclusion planes (FIP) in quartz from basement granitoids. From the deepest part of the drill holes to the unconformable boundary with the basin, propylitic alteration assemblages are progressively replaced by illite and locally by a phengite + Fe chlorite ± Fe oxide assemblage. Illitic alteration is particularly strong along the sediment-granitoid contact and is associated with quartz dissolution. It was followed by calcite and anhydrite precipitation as fracture fillings. U-Pb isotopic dating outlines three successive events: a 3.0-2.9-Ga primary magmatic event, a 2.6-Ga propylitic alteration and a late 1.9-Ga diagenetic event. Fluid inclusion microthermometry suggests the circulation of three types of fluids: (1) a Na-Ca-rich diagenetic brine, (2) a moderately saline (diagenetic + meteoric) fluid, and (3) a low-salinity fluid of probable meteoric origin. These fluids are similar to those previously identified within the overlying sedimentary rocks of the Franceville basin. Overall, the data collected in this study show that the Proterozoic-Archaean unconformity has operated as a major flow corridor for fluids circulation, around 1.9 Ga. highly saline diagenetic brines; hydrocarbon-rich fluids derived from organic matter

  8. 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.

  9. 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

  10. Free energy generation and transfers from Archaean hydrothermal vents to the first metabolism

    NASA Astrophysics Data System (ADS)

    Simoncini, E.; Kleidon, A.

    2010-12-01

    Dissipative structures are far from equilibrium systems which self - organize, maintaining a certain internal material order and require free energy in order to be conserved. From a geological point of view, thermal gradients were the most abundant sources of free energy on the early Earth. Here we demonstrate how chemical free energy can be produced by a geological process, serpentinization, associated to the electrochemical potential generation in off - axis hydrothermal vents. The basis for chemical free energy generation is the thermal gradient between the crust and the Archean ocean, which is enhanced by the release of latent heat during serpentinization. Power can be extracted from this thermal gradient to generate motion. The convective motion of heated, chemically reduced fluid produces a redox front when in contact with the acidic Archaean ocean, generating electrical energy to be used in chemical reactions. Further, in the presence of porous inorganic, heterogeneous matrices acting as catalysts, self - sustained reaction chains raised. The free energy thus available could be used to allow the possibility for the establishment of first organic auto - catalytic chains. Molecular evolutionary steps from acetyl CoA to RNA-cleavage gave then rise to the first proto-metabolic processes. We use simple models to calculate the maximum rates of power transfer from the thermal gradient to electric energy to estimate the maximum possible rate of chemical free energy generation by this process. The model also takes into account the heterogeneity of the mineral matrix and its capability to catalyze reactions and to adsorb molecules selectively. In conclusion, non equilibrium thermodynamics in combination with maximum power assumptions help us to determine the fundamental limits of how much chemical free energy can be generated from a geothermal heat flux, providing conditions for the emergence of metabolism.

  11. 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

    2012-05-01

    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. PMID:22535245

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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 events. 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.

  13. 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

  14. 4-D model of the Archaean crustal evolution of the Fennoscandian Shield based on geological data

    NASA Astrophysics Data System (ADS)

    Slabunov, A.

    2012-04-01

    The Fennoscandian Shield (FS), together with the Canadian Shield (Percival, 2010), has been thoroughly studied geologically, geochronologically and geophysically and can, therefore, be used as testing grounds for developing 4-D models of the evolution of the Early Precambrian Earth's crust. A 4-D model is the result of the integrated interpretation of geological evidence. In this paper a model of crust formation in Archaean time (3.1-2.6 Ga) is presented. It was developed using: 1) isotopic geochronological data for correlating of geological events in different structures (terrains); 2) data on the compositional characteristics of complexes for assessing geodynamic settings in which they were formed; 3) geophysical (especially seismic) data to understand the deep structure of the Earth's crust and, correspondingly, the relationship of terrains. The eastern FS consists dominantly of Archean bedrock that can be divided into the Karelian, Murmansk, Belomorian, Kola, and Norrbotten provinces, each having a distinct crustal growth and subsequent reworking history (Hölttä et al., 2008). The Karelian Craton and the Kola Province fall into relatively large terrains that differ in the age and composition of their rock constituents. The FS is split up into three fragments of the Palaeoarchean (3.5-3.2 Ga) continental crust that presumably existed as one microcontinent. About 3.1 Ga ago it obviously broke up. Ca.3.05 Ga ago a new growth cycle of the continental crust began. During the 3.05-2.95 Ga period the crust was forming by subduction and subsequent accretion to the largest old Vodlozero block. Mantle-plume magmatism manifests itself in the central part of the block. The bulk of the Archaean continental crust of the FS was formed during the 2.95-2.82 Ga period. Fragments of island-arc volcanics and ophiolite-like eclogites have been encountered, for example, in the Belomorian Province. Felsic adakite- and calc-alkaline-series volcanics of this age are known to occur in

  15. 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.

  16. 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.

  17. Dynamics of the Precambrian Continental Crust

    NASA Astrophysics Data System (ADS)

    Perchuk, L. L.; Gerya, T. V.; van Reenen, D. D.; Smit, C. A.

    2003-04-01

    The Precambrian continental crust is mainly composed of (1) granite greenstone belts (GGB) and (2) granulite facies complexes (GFC). The GFC are often separated from GGB by inward dipping crustal scale shear zones with characteristic sense of movements reflecting thrusting of GFC onto cratonic rocks. The isotope age of the shear zones is identical to GFC, while the latter are always younger than the granite greenstone belts. The dynamics relationships between these two geological units strongly determine tectonic evolution of the Precambrian continental crust. Numerous thermobarometric studies of magmatic and metamorphic rocks show that the Archaean to Early Protorozoic crust as well as the Mantle were hot and therefore relatively soft. Such geothermal regimes may limit separation and movement of micro continents, limiting collisional mechanisms in evolution of the Precambrian crust. The goal of this paper is to show evidence for an alterative model that is based on the mechanism of gravitational redistribution of rocks within the Precambrian continental crust, which might be initiated by a fluid/heat flow related to mantle plumes. The model is tested on the basis of geological, geochemical, geophysical and petrologic data for many paired GFT GGB complexes around the word. Studied granulite complexes are located in between Archaean GGB from which they are separated by inward dipping crustal scale shear zones with reverse sense of movements. The most important evidence for this mechanism is: (i) the near isobaric cooling (IC) and (ii) decompression cooling (DC) shapes of the retrograde P T paths recorded in GFC, while rocks from the juxtaposed GGB in footwalls of the bounding shear zones record P T loops. The Pmax of the loops corresponds to the Pmin, recorded in GFC. Thus the GGB P T loop reflects the burial and ascending of the juxtaposed GGB while the GFC P T path records the exhumation only. The identical isotopic age of GFC and contacting rocks from the shear

  18. Possible limits on the composition of the Archaean Ocean

    NASA Technical Reports Server (NTRS)

    Walker, J. C. G.

    1983-01-01

    The potential impact of high carbon dioxide partial pressure on ocean chemistry is examined in order to investigate what constraints are imposed by the known record of chemical sedimentation through time. The evidence consists of the persistence of calcium carbonate and sulfate precipitation throughout almost the entire sedimentary rock record. A uniformitarian point of view that assumes no very great change in the conditions for the deposition of these chemical sediments. The methods of Holland (1972) are used to set limits on the composition of the water from which precipitation occurred. No inconsistencies between the sedimentary rock record and presumed higher partial pressure of carbon dioxide early in earth history, provided that high partial pressure was accompanied by a generally lower pH for seawater, higher concentrations of calcium and biocarbonate ions, and lower concentrations of carbonate and sulfate ions.

  19. Archaean greenstone belt tectonism and basin development: some insights from the Barberton and Pietersburg greenstone belts, Kaapvaal Craton, South Africa

    NASA Astrophysics Data System (ADS)

    de Wit, Maarten J.

    The sediments in two of South Africa's major Archaean greenstone belts, the Barberton and Pietersburg greenstone belts, span an age range of some 800 million years. Both greenstone belts represent remnants of extensive fold and thrust belts with complex, but different polyphase tectonic histories. The oldest sediments were deposited between circa 3470 and 3490 M.a. on oceanic like crust preserved in the Barberton belt, possibly at the same time as sedimentation on similar oceanic crust preserved in the Pietersburg belt. Thereafter, the geologic evolution of these two belts diverged considerably. In the Barberton belt, there is clear evidence that the oceanic crust and sediments were obducted onto an intra-arc basin environment within 50 million years of its formation. The sequence was later further imbricated by northwest directed thrust stacking between 3300-3200 M.a. Basin development during both periods of thrusting took place in close proximity to active "calc-alkaline" arc systems. Deformation of the sediments within these basins took place while the same sediments were being deposited. Sedimentation took place predominantly in subaqueous environments, ranging from submarine mid-fans below the photic zone to tidal flats and deltaic plains. The sediments represent a polyhistory successor-type basin: early basins developed along a complex subduction related plate boundary; these basins later evolved into foreland depositories along and within collisional environments of an accretionary orogen. Late in the history of the Barberton greenstone belt (circa 3100 M.a.), the rocks were in places thermally reactivated and probably subjected to extensional processes; these processes overlapped in time with the main episodes of economic gold mineralization, and are of "early Witwatersrand-basin" age. The oceanic-like crust (including associated sediments) preserved in the Pietersburg belt was not significantly deformed until at least 500 million years after its formation

  20. 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.

  1. Archaean ultra-depleted komatiites formed by hydrous melting of cratonic mantle.

    PubMed

    Wilson, A H; Shirey, S B; Carlson, R W

    2003-06-19

    Komatiites are ultramafic volcanic rocks containing more than 18 per cent MgO (ref. 1) that erupted mainly in the Archaean era (more than 2.5 gigayears ago). Although such compositions occur in later periods of Earth history (for example, the Cretaceous komatiites of Gorgona Island), the more recent examples tend to have lower MgO content than their Archaean equivalents. Komatiites are also characterized by their low incompatible-element content, which is most consistent with their generation by high degrees of partial melting (30-50 per cent). Current models for komatiite genesis include the melting of rock at great depth in plumes of hot, diapirically rising mantle or the melting of relatively shallow mantle rocks at less extreme, but still high, temperatures caused by fluxing with water. Here we report a suite of ultramafic lava flows from the Commondale greenstone belt, in the southern part of the Kaapvaal Craton, which represents a previously unrecognized type of komatiite with exceptionally high forsterite content of its igneous olivines, low TiO(2)/Al(2)O(3) ratio, high silica content, extreme depletion in rare-earth elements and low Re/Os ratio. We suggest a model for their formation in which a garnet-enriched residue left by earlier cratonic volcanism was melted by hydration from a subducting slab. PMID:12815428

  2. 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.

  3. 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.

  4. Eclogite xenoliths in west African kimberlites as residues from Archaean granitoid crust formation

    NASA Astrophysics Data System (ADS)

    Rollinson, Hugh

    1997-09-01

    Eclogites are a comparatively rare but petrologically important member of kimberlite xenolith suites. Their broadly basaltic chemistry has led many authors to propose that they represent ancient, subducted ocean crust. Recent studies, however, have suggested an alternative origin and propose that kimberlitic eclogites are residues from the process of Archaean granitoid crust formation. Geochemical arguments in support of this new model were previously based on the trace-element chemistry of eclogitic minerals. Here I report that the major-element chemistry of eclogite xenoliths also supports a crustal residue model. I examine eclogite xenoliths from kimberlite pipes at Koidu, Sierra Leone, which sample the lithospheric mantle underlying the Archaean (2.8Gyr) granitoid crust of the West African craton. Geochemical plots of major elements measured in unaltered, whole-rock samples of low-silica eclogite demonstrate that they are complementary to the granitoids of the West African craton and have compositions which indicate that both were derived from a common basaltic parent rock.

  5. 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

  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. 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. PMID:16612379

  8. 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.

  9. Mass dependent isotope fractionation during impacts induced the Archaean mass-independent fractionation of sulphur: Evidence against Great Oxidation Event

    NASA Astrophysics Data System (ADS)

    Huang, H.

    2010-12-01

    A prevailing hypothesis, low-oxygen level of the Archaean atmosphere, relies strongly on the presence of strong mass-independent fractionation (MIF) of the sulfur isotopes in sulfide- and sulfate-bearing minerals older than 2.4 billion years. Actually, there is “a broad overlap between MIF signals observed within Archaean sedimentary sequences and periods of enhanced asteroid impacts represented by impact ejecta/fallout units”(Glikson 2010) (Fig. 1). Moreover, usually MIF- related sulphur occurs in the Archaean sedimentary rocks as pyrite (FeS2) which has been found in the K-T boundary clay beds and in several identified impact craters, which is an independent argument in favor of pyrites could be the product of impact. Impact processes (vaporization and condensation) are sufficient to explain the MIF signals following the principle: the earlier the condensed material, the more enriched in lighter isotopes (Huang 2010). The nature of the MIF of the sulfur isotopes is that the fractionation of isotope is still mass dependent during impacts, which means the measured nonzero Δ33S values of Archean sulfide- and sulfate-bearing minerals indicate that their different condensation sequences. Another important line of evidence that support the impact-generated MIF of the sulfur isotopes comes from the various iron isotope values of the pyrites especially those with iron isotope heterogeneity at grain scale. Thus, it is clear that the signals are the markers of impact rather than O2 poor atmosphere. Furthermore, this can also account for the lack of MIF-S in several Archaean units before 2.4 billion years. Figure 1 Plot of mass-independent fractionation of sulphur and asteroid impact events with age. Modified from Glikson (2010)

  10. Sintered cataclasite of the Archaean Pretorius fault zone, TauTona mine, South Africa

    NASA Astrophysics Data System (ADS)

    Zechmeister, M. S.; Heesakkers, V.; Moore, K.; Campher, C.; Reches, Z.

    2005-12-01

    We have studied the exposures of the Pretorius fault at depth of ~ 3.5 km in the TauTona gold mine, South Africa, as part of the NELSAM project (earthquakes.ou.edu). The Pretorius fault has been inactive since the Archaean and is a 10 km long fault with 30-60 m of throw and suspected horizontal slip of ~ 200 m (Heesakkers et al, this meeting). Its fault-zone is ~25 m wide with tens of cross-cutting segments that display one distinct fault-rock which was previously classified as a mylonite or pseudotachylite. We refer to this enigmatic rock as `sintered cataclasite', and we present here its structural and mineralogical characteristics and discuss possible mechanisms for its formation. The sintered cataclasite is a highly cohesive and massive rock that ranges in color from grey to green, which appears in veins along the fault segments. These veins range in thickness from a few millimeters to tens of centimeters, and are locally continuous for tens of meters. The veins vary significantly in thickness with common pinching out along a given host segment. Some of the cataclasite veins carry secondary injection veins that penetrated the host blocks at high angles to the segment surface. The sintered cataclasite is composed of a cohesive, fine-grain quartzitic matrix, with abundant angular to sub-rounded fractured quartz and opaque minerals clasts that are 0.01-0.5 m in size. Flow features can be identified in the sintered cataclasite by the presence of injection veins and wall-parallel flow banding. We did not find evidence for vein-parallel shear, e.g. rotated clasts, or evidence of large-scale melting, e.g. microlites or partially melted clasts (these rocks cannot be regarded as pseudotachylites). SEM image analysis revealed "hour glass" contacts between quartz grains that suggest sintering of a granular material after granulation. Multiple slip events were recognized in a few fault segments by the presence of cleavage with kinked micas and cross-cutting cataclasite

  11. Receiver function analysis of the crust and upper mantle from the North German Basin to the Archaean Baltic Shield

    NASA Astrophysics Data System (ADS)

    Alinaghi, A.; Bock, G.; Kind, R.; Hanka, W.; Wylegalla, K.

    2003-11-01

    Two passive seismic experiments have been carried out across the Trans European Suture Zone (TESZ) from northern Germany to southern Sweden (TOR) and across the Proterozoic-Archaean suture in Finland (SVEKALAPKO) to improve our understanding of the processes involved in the creation of the European continent. Teleseismic earthquakes recorded by the two networks and stations of the GRSN and GEOFON permanent networks have been used for studies of the crust-mantle, and upper mantle seismic discontinuities with the receiver function method. Along the TOR network the depth to the Moho increases from 30 km at the southern edge of the profile to 40 km at the Elbe Line. Between the Elbe Line and TESZ the Moho branches off and whereas the deeper branch continues at 40 km depth to the TESZ a second branch appears at 30-35 km depth. The upper branch descends north of the TESZ to below 55 km under the northern end of the TOR profile. The crustal thickening north of the TESZ is accompanied by an increase in average Vp/Vs values, appearance of intracrustal conversion zones and north dipping features which we interpret as remnants of the subduction and subsequent collision between Avalonia and Baltica. In southern Finland beneath the SVEKALAPKO network the Moho starts in the south at the depth of 40-45 km, plunges to about 65 km depth south of the Archaean-Proterozoic suture. This deepening of the Moho is coincident with a north dipping intracrustal structure apparently related to the subduction and collision and of the Proterozoic and Archaean provinces in Proterozoic. North of the line of the suture the Moho rises smoothly to 45-50 km depth in the Archaean province. Along the TOR profile, 410 and 660 discontinuities were hard to detect. However, manyfold stacking of receiver functions revealed that the conversions from the two discontinuities arrive more or less according to IASP91 predicted time. Across the SVEKALAPKO network 410 and 660 discontinuities arrive markedly earlier

  12. 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

  13. 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

  14. A Field Trip to the Archaean in Search of Darwin's Warm Little Pond.

    PubMed

    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

  15. 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.

  16. 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.

  17. 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.

  18. Diapirism on Venus and the Early Earth and The thermal effect of fluid flows in AECL's Tunnel Sealing Experiment

    NASA Astrophysics Data System (ADS)

    Robin, Catherine M. I.

    2010-12-01

    Flow instabilities occur at all scales in planetary systems. In this thesis we examine three cases of such instabilities, on three very different length scales. In the first part, we test the idea that Archean granite-greenstone belts (GGBs) form by crustal diapirism, or Rayleigh-Taylor instabilities. GGBs are characterized by large granitic domes (50-100 km in diameter) embedded in narrow keel-shaped greenstones. They are ubiquitous in Archean (> 2.5 Ga) terrains, but rare thereafter. We performed finite element calculations for a visco-elastic, temperature-dependent, non-Newtonian crust under conditions appropriate for the Archean, which show that dense low-viscosity volcanics overlying a felsic basement will overturn diapirically in as little as 10 Ma, displacing as much as 60 % of the volcanics to the lower crust. This surprisingly fast overturn rate suggests that diapiric overturn dominated crustal tectonics in the hot conditions of the Early Earth, becoming less important as the Earth cooled. Moreover, the deposition of large volumes of wet basaltic volcanics to the lower crust may provide the source for the formation of the distinctly Archean granitic rocks which dominate Earth's oldest continents. The second part examines the origin of Venusian coronae, circular volcanic features unique to Venus. Coronae are thought to result from small instabilities (diapirs) from the core-mantle boundary, which are typical of stagnant-lid convection. However, most young coronae are located in a region surrounded by long-lived hotspots, typical of a more active style of mantle convection. Using analogue experiments in corn syrup heated from below, we show that the co-existence of diapirs and long-lived mantle plumes are a direct consequence of the catastrophic overturn of the cold Venusian lithosphere thought to have occurred ˜ 700 Ma ago. In the last part we analyze the thermal effect of fluid flow through a full-scale experiment testing clay and concrete tunnel seals in

  19. Archaean atmospheric evolution: evidence from the Witwatersrand gold fields, South Africa

    NASA Astrophysics Data System (ADS)

    Frimmel, Hartwig E.

    2005-04-01

    The Witwatersrand gold fields in South Africa, the world's largest gold-producing province, play a pivotal role in the reconstruction of the Archaean atmosphere and hydrosphere. Past uncertainties on the genetic model for the gold caused confusion in the debate on Archaean palaeoenvironmental conditions. The majority of Witwatersrand gold occurs together with pyrite, uraninite and locally bitumen, on degradational surfaces of fluvial conglomerates that were laid down between 2.90 and 2.84 Ga in the Central Rand Basin. Although most of the gold appears as a precipitate within, or associated with, post-depositional hydrothermal phases and along microfractures, available microtextural, mineralogical, geochemical and isotopic data all indicate that this hydrothermal gold, analogous to some pyrite and uraninite, was derived from the local mobilisation of detrital particles. Some of the key pieces of evidence are a significant correlation of the gold, pyrite and uraninite with other heavy minerals as well as sedimentary lithofacies, local preservation of in-situ gold micronuggets and abundant rounded forms of pyrite and uraninite, compositional heterogeneity on a microscale of the gold as well as the rounded pyrite and uraninte, and radiometric age data that indicate an age of the gold, pyrite and uraninite that is older than the maximum age of deposition for the host sediment. None of these observations/data is compatible with any of the suggested hydrothermal models, in which auriferous fluids were introduced from an external source into the host rock succession after sediment deposition. In contrast, those arguments, used in favour of hydrothermal models, emphasise the microtextural position of most of the gold, which highlights the undisputed hydrothermal nature of that gold in its present position, but does not explain its ultimate source. Furthermore, the macro-scale setting of the stratiform ore deposits is in stark contrast to any known type of epigenetic

  20. 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

  1. 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

  2. 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. PMID:23619695

  3. Iron isotope fractionation during microbial dissimilatory iron oxide reduction in simulated Archaean seawater.

    PubMed

    Percak-Dennett, E M; Beard, B L; Xu, H; Konishi, H; Johnson, C M; Roden, E E

    2011-05-01

    The largest Fe isotope excursion yet measured in marine sedimentary rocks occurs in shales, carbonates, and banded iron formations of Neoarchaean and Paleoproterozoic age. The results of field and laboratory studies suggest a potential role for microbial dissimilatory iron reduction (DIR) in producing this excursion. However, most experimental studies of Fe isotope fractionation during DIR have been conducted in simple geochemical systems, using pure Fe(III) oxide substrates that are not direct analogues to phases likely to have been present in Precambrian marine environments. In this study, Fe isotope fractionation was investigated during microbial reduction of an amorphous Fe(III) oxide-silica coprecipitate in anoxic, high-silica, low-sulphate artificial Archaean seawater at 30 °C to determine if such conditions alter the extent of reduction or isotopic fractionations relative to those observed in simple systems. The Fe(III)-Si coprecipitate was highly reducible (c. 80% reduction) in the presence of excess acetate. The coprecipitate did not undergo phase conversion (e.g. to green rust, magnetite or siderite) during reduction. Iron isotope fractionations suggest that rapid and near-complete isotope exchange took place among all Fe(II) and Fe(III) components, in contrast to previous work on goethite and hematite, where exchange was limited to the outer few atom layers of the substrate. Large quantities of low-δ(56)Fe Fe(II) (aqueous and solid phase) were produced during reduction of the Fe(III)-Si coprecipitate. These findings shed new light on DIR as a mechanism for producing Fe isotope variations observed in Neoarchaean and Paleoproterozoic marine sedimentary rocks. PMID:21504536

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  5. 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

  6. 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

  7. Geochronology of an archaean tonalitic gneiss dome in Northern Finland and its relation with an unusual overlying volcanic conglomerate and komatiitic greenstone

    NASA Astrophysics Data System (ADS)

    Kröner, A.; Puustinen, K.; Hickman, M.

    1981-04-01

    Archaean gneiss-greenstone relationships are still unresolved in many ancient cratonic terrains although there is growing evidence that most of the late Archaean greenstone assemblages were deposited on older tonalitic crust. We report here well defined basement-cover relationships from a late Archaean greenstone belt in Lapland, north of the Polar Circle. The basal greenstone sequence contains quartzite, schist, komatiitic volcanics and an unusual volcanic conglomerate with well preserved granite pebbles of an older basement. These rocks surround a gneiss dome composed of foliated tonalite which shows a polyphase deformation pattern not seen in the neighbouring greenstones. Zircon fractions of the gneisses plot on two discordia lines and give upper intercept ages with concordia at 3,069±16 Ma and 3,110±17 Ma respectively. One fraction contains metamict zircons with components at least 3,135 Ma old. These are the oldest reliable ages yet reported from the Archaean of the Baltic Shield. Rb-Sr whole-rock dating of the tonalitic gneiss yielded an isochron age of 2,729±122 Ma and an ISr of 0.703±0.001. This is interpreted to reflect a resetting event during which the gneisses may have acquired their present tectonic fabric. Rb-Sr model age calculations yield mantle values for ISr at about 2,950±115 Ma and suggest that the tonalite was intruded into the crust as juvenile material at about 3.1 Ga ago as reflected by the zircon ages. It was subsequently deformed and isotopically reset at about 2.7 Ga ago, prior to greenstone deposition. Comparison with tonalitic gneisses of eastern Karelia displays significant differences and suggests that the Archaean of Finland may contain several generations of pre-greenstone granitoid rocks.

  8. Electromagnetic mini arrays (EMMA project). 3D modeling/inversion for mantle conductivity in the Archaean of the Fennoscandian Shield

    NASA Astrophysics Data System (ADS)

    Smirnov, M. Yu.; Korja, T.; Pedersen, L. B.

    2009-04-01

    Two electromagnetic arrays are used in the EMMA project to study conductivity structure of the Archaean lithosphere in the Fennoscandian Shield. The first array was operated during almost one year, while the second one was running only during the summer time. Twelve 5-components magnetotelluric instruments with fluxgate magnetometers recorded simultaneously time variations of Earth's natural electromagnetic field at the sites separated by c. 30 km. To better control the source field and to obtain galvanic distortion free responses we have applied horizontal spatial gradient (HSG) technique to the data. The study area is highly inhomogeneous, thus classical HSG might give erroneous results. The method was extended to include anomalous field effects by implementing multivariate analysis. The HSG transfer functions were then used to control static shift distortions of apparent resistivities. During the BEAR experiment 1997-2002, the conductance map of entire Fennoscandia was assembled and finally converted into 3D volume resistivity model. We have used the model, refined it to get denser grid around measurement area and calculated MT transfer functions after 3D modeling. We have used trial-and-error method in order to further improve the model. The data set was also inverted using 3D code of Siripunvaraporn (2005). In the first stage we have used homogeneous halfspace as starting model for the inversion. In the next step we have used final 3D forward model as apriori model. The usage of apriori information significantly stabilizes the inverse solution, especially in case of a limited amount of data available. The results show that in the Archaean Domain a conductive layer is found in the upper/middle crust on contrary to previous results from other regions of the Archaean crust in the Fennoscandian Shield. Data also suggest enhanced conductivity at the depth of c. 100 km. Conductivity below the depth of 200-250 km is lower than that of the laboratory based estimates

  9. 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. PMID:20360739

  10. Multiple sulphur and iron isotope composition of detrital pyrite in Archaean sedimentary rocks: A new tool for provenance analysis

    NASA Astrophysics Data System (ADS)

    Hofmann, Axel; Bekker, Andrey; Rouxel, Olivier; Rumble, Doug; Master, Sharad

    2009-09-01

    Multiple S ( δ34S and δ33S) and Fe ( δ56Fe) isotope analyses of rounded pyrite grains from 3.1 to 2.6 Ga conglomerates of southern Africa indicate their detrital origin, which supports anoxic surface conditions in the Archaean. Rounded pyrites from Meso- to Neoarchaean gold and uranium-bearing strata of South Africa are derived from both crustal and sedimentary sources, the latter being characterised by non-mass dependent fractionation of S isotopes ( Δ33S as negative as - 1.35‰) and large range of Fe isotope values ( δ56Fe between - 1.1 and 1.2‰). Most sediment-sourced pyrite grains are likely derived from sulphide nodules in marine organic matter-rich shales, sedimentary exhalites and volcanogenic massive sulphide deposits. Some sedimentary pyrite grains may have been derived from in situ sulphidised Fe-oxides, prior to their incorporation into the conglomerates, as indicated by unusually high positive δ56Fe values. Sedimentary sulphides without significant non-mass dependent fractionation of S isotopes were also present in the source of some conglomerates. The abundance in these rocks of detrital pyrite unstable in the oxygenated atmosphere may suggest factors other than high pO 2 as the cause for the absence of significant non-mass dependent fractionation processes in the 3.2-2.7 Ga atmosphere. Rounded pyrites from the c. 2.6 Ga conglomerates of the Belingwe greenstone belt in Zimbabwe have strongly fractionated δ34S, Δ33S and δ56Fe values, the source of which can be traced back to black shale-hosted massive sulphides in the underlying strata. The study demonstrates the utility of combined multiple S and Fe isotope analyses for provenance reconstruction of Archaean sedimentary successions.

  11. 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.

  12. A small Archaean belt - diverse age ensemble: A U-Pb study of the Tipasjärvi greenstone belt, Karelia Province, central Fennoscandian Shield, Finland

    NASA Astrophysics Data System (ADS)

    Lehtonen, Elina; Käpyaho, Asko

    2016-03-01

    The Archaean Tipasjärvi greenstone belt is a small area (ca. 5 × 25 km) located within the Karelia Province in Central Fennoscandian Shield, Finland. The belt forms the southernmost part of the larger Archaean Suomussalmi-Kuhmo-Tipasjärvi greenstone complex. The present study results for this site are based on zircon grains of 12 metavolcanic and metasedimentary rock samples that were studied with the single-grain secondary ion mass spectrometry (SIMS) U-Pb method. Our data indicate that the volcanism in the belt took place over three separate episodes: ca. 2.84 Ga, 2.82 Ga and 2.80 Ga. The oldest volcanic rocks are older than the oldest dated tonalitic pluton adjacent to the belt. The main geochemical characteristics of the samples reveal that the felsic volcanic rocks of the different age groups resembled each other. However, contrasting trace element geochemical characteristics between the different age groups are also distinguishable. The detrital zircon record agrees with previous observations indicating that the sediments accumulated at least 50 Myr after the formation of the youngest volcanic rocks. During sediment deposition, older crustal material (> 3.0 Ga) was exposed within the source area. The geochronological results in this study enable us to update the chronostratigraphic interpretation of the Tipasjärvi greenstone belt and to compare these results to those from other parts of the Archaean Suomussalmi-Kuhmo-Tipasjärvi greenstone complex and adjacent tonalitic plutons.

  13. Palaeoproterozoic high-pressure granulite overprint of the Archaean continental crust: evidence for homogeneous crustal thickening (Man Rise, Ivory Coast)

    NASA Astrophysics Data System (ADS)

    Pitra, Pavel; Kouamelan, Alain N.; Ballèvre, Michel; Peucat, Jean-Jacques

    2010-05-01

    The character of mountain building processes in the Palaeoproterozoic times is subject to much debate. The local observation of Barrovian-type assemblages and high-pressure granulite relics in the Man Rise (Côte d'Ivoire), led some authors to argue that Eburnean (Palaeoproterozoic) reworking of the Archaean basement was achieved by modern-style thrust-dominated tectonics (e.g., Feybesse & Milési, 1994). However, it has been suggested that crustal thickening and subsequent exhumation of high-pressure crustal rocks can be achieved by virtue of homogeneous, fold-dominated deformation of hot crustal domains even in Phanerozoic orogenic belts (e.g., Schulmann et al., 2002; 2008). We describe a mafic granulite of the Kouibli area (Archaean part of the Man Rise, western Ivory Coast) that displays a primary assemblage (M1) containing garnet, diopsidic clinopyroxene, red-brown pargasitic amphibole, plagioclase (andesine), rutile, ilmenite and quartz. This assemblage is associated with a subvertical regional foliation. Symplectites that develop at the expense of the M1 assemblage contain orthopyroxene, clinopyroxene, plagioclase (bytownite), green pargasitic amphibole, ilmenite and magnetite (M2). Multiequilibrium thermobarometric calculations and P-T pseudosections calculated with THERMOCALC suggest granulite-facies conditions of ca. 13 kbar, 850°C and <7 kbar, 700-800°C for M1 and M2, respectively. In agreement with the qualitative information obtained from reaction textures and chemical zoning of minerals, this suggests an evolution dominated by decompression accompanied by moderate cooling. A Sm-Nd garnet - whole-rock age of 2.03 Ga determined on this sample indicates that this evolution occurred during the Palaeoproterozoic. We argue that from the geodynamic point of view the observed features are best explained by homogeneous thickening of the margin of the Archaean craton, re-heated and softened due to the accretion of hot, juvenile Palaeoproterozoic crust, as

  14. Palaeoseismic events recorded in Archaean gold-quartz vein networks, Val d'Or, Abitibi, Quebec, Canada

    NASA Astrophysics Data System (ADS)

    Boullier, Anne-Marie; Robert, François

    1992-02-01

    Archaean gold-quartz vein deposits are commonly hosted in high-angle reverse shear zones and are interpreted to have formed in a regime of horizontal compression and high fluid pressure environment. This paper presents the results of a combined structural and fluid inclusion study on three gold-quartz vein deposits of the Val d'Or area (Abitibi, Quebec) consisting of subhorizontal extensional veins and E-W steeply dipping shear veins. Crack-seal structures, tourmaline fibres, stretched quartz crystals and open-space filling textures indicate that the subhorizontal veins formed by hydraulic fracturing under supralithostatic fluid pressure. CO 2-rich and H 2O + NaCl fluid inclusions, interpreted as two coexisting immiscible fluids, occur typically in microcracks of different orientations interpreted to have formed in the σ1- σ2 plane. Horizontal CO 2-rich fluid inclusion planes are contemporaneous with the opening of these veins (σ 3 vertical). Vertical H 2O + NaCl fluid inclusion planes, as well as some microstructures, such as deformed minerals, indicate that the same extensional veins have experienced episodic vertical shortening (σ 3 horizontal) alternating with the opening events. Deformation and slip/opening also occurred in shear veins in which preferred orientation of fluid inclusion planes is not clear, except that the H 2O + NaCl fluid inclusion planes tend to be oriented at high angles to the slip direction. The successive opening and collapse events in subhorizontal extensional veins are correlated with deformation and slip/opening events in shear veins, respectively, and are attributed to cyclic fluid pressure fluctuations in the system. They are thus consistent with the fault-valve model: sudden drop in fluid pressure from supralithostatic to lower values induces fluid unmixing and occurs immediately post-failure following seismic rupturing along the shear zone. Sealing of the shear veins allows the fluid pressure to build up again and the

  15. 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.

  16. 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

  17. 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.

  18. Ni-rich spinels and platinum group element nuggets condensed from a Late Archaean impact vapour cloud

    NASA Astrophysics Data System (ADS)

    Goderis, Steven; Simonson, Bruce M.; McDonald, Iain; Hassler, Scott W.; Izmer, Andrei; Belza, Joke; Terryn, Herman; Vanhaecke, Frank; Claeys, Philippe

    2013-08-01

    Deciphering Earth's impact history before ∼2 Ga relies heavily on the lunar record and terrestrial spherule layers, which are distal ejecta from large impacts. This study focuses on the Paraburdoo and Reivilo spherule layers in Western Australia and South Africa respectively, that were probably formed by one impact around 2.57 Ga. Both layers contain an aggregate thickness of ∼2 cm of spherules, known as microkrystites. These spherules are up to ∼0.6 mm in diameter and crystallized during flight, but were diagenetically replaced by K-feldspar and phlogopite with remarkable textural retention. Unlike any other Archaean layer, except for the 3.2 Ga S3 layer in the Barberton greenstone belt, the Paraburdoo and Reivilo spherules contain Ni-rich spinel crystals and high concentrations of meteoritic material (up to 357 ng g-1 Ir for bulk samples of several gram). These exceptional characteristics shed new light on the distribution of the meteoritic component carrier phases (metallic alloys dispersed in the pristine glass) and the processes involved in impact spherule formation and secondary alteration.

  19. 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. PMID:27253436

  20. 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.

  1. 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.

  2. Mafic-ultramafic magmatism of the Early Precambrian (from the Archean to Paleoproterozoic)

    NASA Astrophysics Data System (ADS)

    Sharkov, E. V.; Bogina, M. M.

    2009-04-01

    early Paleoproterozoic (2.5-2.35 Ga), values of that ratio considerably declined in the SHMS rocks and then quickly grew in the Middle Paleoproterozoic volcanics (2.2-1.9 Ga) to attain finally the values typical of the Phanerozoic magmas associated in origin with mantle plumes. The ɛNd(T) parameter was decreasing with time from positive values in the Paleoarchean to negative ones in the SHMS rocks of the Paleoproterozoic most likely in response to grown proportion of ancient crustal material in magmatic melts. Since the mid-Paleoproterozoic, the ɛNd(T) values turn in general into positive again reflecting change in the character of magmatic activity: the SHMS melts gave place at that time to the Fe-Ti picrite-basaltic magmas. The primary crust of the Earth was presumably of sialic composition and originated during solidification from the bottom upward of the global magma ocean a few hundreds kilometers deep, when most fusible components migrated up to the surface to form there the granitic crust. Geological history of the Earth commenced at the appearance time of granite-greenstone terranes and granulite belts separating them, the first large tectonic structures formed under influence of raising mantle superplumes.

  3. Archaean fluid-assisted crustal cannibalism recorded by low δ18O and negative ɛHf(T) isotopic signatures of West Greenland granite zircon

    NASA Astrophysics Data System (ADS)

    Hiess, Joe; Bennett, Vickie C.; Nutman, Allen P.; Williams, Ian S.

    2011-06-01

    The role of fluids during Archaean intra-crustal magmatism has been investigated via integrated SHRIMP U-Pb, δ18O and LA-MC-ICPMS 176Hf isotopic zircon analysis. Six rock samples studied are all from the Nuuk region (southern West Greenland) including two ~3.69 Ga granitic and trondhjemitic gneisses, a 3.64 Ga granitic augen gneiss, a 2.82 Ga granodioritic Ikkattoq gneiss, a migmatite with late Neoarchaean neosome and a homogeneous granite of the 2.56 Ga Qôrqut Granite Complex (QGC). All zircon grains were thoroughly imaged to facilitate analysis of magmatic growth domains. Within the zircon analysed, there is no evidence for metamictization. Initial ɛHf zircon values ( n = 63) are largely sub-chondritic, indicating the granitic host magmas were generated by the remelting of older, un-radiogenic crustal components. Zircon from some granite samples displays more than one 207Pb/206Pb age, and correlated with 176Hf/177Hf compositions can trace multiple phases of remelting or recrystallization during the Archaean. Model ages calculated using Lu/Hf arrays for each sample indicate that the crustal parental rocks to the granites, granodiorites and trondhjemites segregated from a chondrite-like reservoir at an earlier time during the Archaean, corresponding to known formation periods of more primitive tonalite-trondhjemite-granodiorite (TTG) gneisses. Zircon from the ~3.69 Ga granite, the migmatite and QGC granite contains Eoarchaean cores with chondritic 176Hf/177Hf and mantle-like δ18O compositions. The age and geochemical signatures from these inherited components are identical to those of surrounding tonalitic gneisses, further suggesting genesis of these granites by remelting of broadly tonalitic protoliths. Zircon oxygen isotopic compositions ( n = 62) over nine age populations (six igneous and three inherited) have weighted mean or mean δ18O values ranging from 5.8 ± 0.6 to 3.7 ± 0.5‰. The 3.64 Ga granitic augen gneiss sample displays the highest δ18O with

  4. The diversity of early Life on Earth : implications for life on Mars

    NASA Astrophysics Data System (ADS)

    Westall, F.; Southam, G.

    Although the locations where the earliest traces of life can be studied are few and far between (Isua, 3.8 Ga; Pilbara and Barberton, 3.5-3.3 Ga), the life that existed in the Early Archaean life has left a wealth of testimony. Structural and chemical fossils found in Early Arcahean `habitats' demonstrate that the biosphere was already in an advanced evolutionary state, i.e., much of the strata preserved from this period appears to have been colonised by morphologically and biochemically diverse bacteria. The Early-Mid Archaean microorganisms were morphologically similar to modern organisms and behaved in the same way, building colonies, biofilms and mats and interacting directly with their immediate substrate and with each other (in consortia). Their metabolic processes included chemolithotrophy, possibly methanogenesis and possibly anoxygenic photosynthesis. Early life was diverse and included thermophilic, acid-tolerant, halo-tolerant to halophilic, and radiation resistant species. With one exception, the traces of early life are subtle, on the scale of tens to hundreds of µm although, where environmental conditions were stable and quiet enough for their development, microbial mats on sediment surfaces could contribute to the formation of stromatolites of about 10 cm in height. The diversity, relative level of evolution and widespread distribution of life by 3.5 Ga implies that it must have evolved much earlier, possibly even before or during the period of late heavy bombardment). However, no record of its appearance and early evolution remains on Earth. Given the conditions on early Mars were generally similar to those on early Earth, i.e., habitable, the Southern Highlands of Mars could potentially host this missing record. Life on early Mars would probably have been similarly subtle in its expression, although there is a possibility of "stumbling" across small macroscopic stromatolites. If life still exists on the planet today, it's in the subsurface and its

  5. From Archaean oceans to Late Proterozoic cratons: The origin, evolution and preservation of the continental material on earth

    NASA Astrophysics Data System (ADS)

    Celal Şengör, A. M.

    2013-04-01

    The earth's outermost rocky shell consists of two major components: continents and oceans. Oceans are continuously generated along spreading centres and also continuously destroyed by subduction along deep-sea trenches. Because of their ephemeral nature they have an average age of 0.1 Ga. The oceanic crust has an average density of about 2.9 g/cc. It covers nearly 60% of the planet's surface, but makes up only 20% of its crust and a vanishingly small 0.00099% of its total mass. No part of the oceanic crust has any permanence: even its slightly more buoyant parts (oceanic plateaux) are ultimately subducted unless protected within a continental embayment (e.g. the Pre-Caspian Depression). The only exception to this rule may be the Tarim Block, which may be a trapped oceanic plateau of Proterozoic age now functioning as a craton. Whether the Black and the South Caspian oceans will have a similar destiny cannot now be told, although the latter is now being subducted along the Apsheron sill. Continents by contrast seem permanent parts of the crust: Their average density is 2.85g/cc and mean age is 2.0 Ga and in places the oldest rocks are dated to be older than 3.8 Ga. Some individual zircons recovered from continents in a few places are older than 4 Ga; some have yielded evidence for wet mantle melting and reworked continental crust as far back as 4,370 million years ago. In fact, there is now 176Hf/177Hf evidence consistent with the view that a volume of continental crust close to the present one may have formed by 4.4. to 4.5. Ga, but then entirely mixed back into the mantle by the beginning of the Archaean, both by a permobile subduction regime and heavy meteorite bombardment-controlled mixing! The present rock record on continents began to be kept since about 3.8 Ga ago, i.e., since the end of the heavy meteorite bombardment. The preserved Archaean tectonic record shows a great resemblance to the Turkic-type orogens of the Phanerozoic and probably formed in a

  6. 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.

  7. Invisible gold in arsenian pyrite and arsenopyrite from a multistage Archaean gold deposit: Sunrise Dam, Eastern Goldfields Province, Western Australia

    NASA Astrophysics Data System (ADS)

    Sung, Y.-H.; Brugger, J.; Ciobanu, C. L.; Pring, A.; Skinner, W.; Nugus, M.

    2009-10-01

    The Sunrise Dam gold mine (11.1 Moz Au) is the largest deposit in the Archaean Laverton Greenstone Belt (Eastern Goldfields Province, Yilgarn Craton, Western Australia). The deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal-scale structure. The Au content of arsenian pyrite and arsenopyrite from four mineralizing stages (D1, D3, D4a, and D4b) and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry. Pyrite contains up to 3,067 ppm Au ( n = 224), whereas arsenopyrite contains up to 5,767 ppm ( n = 19). Gold in arsenopyrite (D4a stage) was coprecipitated and remained as “invisible gold” (nanoparticles and/or lattice-bound) during subsequent deformation events. In contrast, gold in pyrite is present not only as “invisible gold” but also as micrometer-size inclusions of native gold, electrum, and Au(Ag)-tellurides. Pristine D1 and D3 arsenian pyrite contains relatively low Au concentrations (≤26 ppm). The highest Au concentrations occur in D4a arsenian-rich pyrite that has recrystallized from D3 pyrite. Textures show that this recrystallization proceeded via a coupled dissolution-reprecipitation process, and this process may have contributed to upgrading Au grades during D4a. In contrast, Au in D4b pyrite shows grain-scale redistribution of “invisible” gold resulting in the formation of micrometer-scale inclusions of Au minerals. The speciation of Au at Sunrise Dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple Au-precipitating mechanisms within a single plumbing system.

  8. An efficient lightning energy source on the early Earth.

    PubMed

    Hill, R D

    1992-01-01

    Miller and Urey suggested in 1959 that lightning and corona on the early Earth could have been the most favorable sources of prebiotic synthesis. In 1991 Chyba and Sagan reviewed the presently prevailing data on electrical discharges on Earth and they raised questions as to whether the electrical sources of prebiotic synthesis were as favorable as was claimed. The proposal of the present paper is that localized lightning sources associated with Archaean volcanoes could have possessed considerable advantages for prebiotic synthesis over the previously suggested global sources. PMID:11536519

  9. An efficient lightning energy source on the early earth

    NASA Astrophysics Data System (ADS)

    Hill, R. D.

    1992-09-01

    Miller and Urey suggested in 1959 that lightning and corona on the early Earth could have been the most favorable sources of prebiotic synthesis. In 1991 Chyba and Sagan reviewed the presently prevailing data on electrical discharges on Earth and they raised questions as to whether the electrical sources of prebiotic synthesis were as favorable as was claimed. The proposal of the present paper is that localized lightning sources associated with Archaean volcanoes could have possessed considerable advantages for prebiotic synthesis over the previously suggested global sources.

  10. Growth of early continental crust by water-present eclogite melting in subduction zones

    NASA Astrophysics Data System (ADS)

    Laurie, A.; Stevens, G.

    2011-12-01

    The geochemistry of well preserved Paleo- to Meso-Archaean Tonalite-Trondhjemite-Granodiorite (TTG) suite rocks, such as the ca 3.45 Ga trondhjemites from the Barberton greenstone belt in South Africa, provides insight into the origins of Earth's early felsic continental crust. This is particularly well demonstrated by the high-Al2O3 variety of these magmas, such as the Barberton rocks, where the geochemistry requires that they are formed by high pressure (HP) melting of a garnet-rich metamafic source. This has been interpreted as evidence for the formation of these magmas by anatexis of the upper portions of slabs within Archaean subduction zones. Most of the experimental data relevant to Archaean TTG genesis has been generated by studies of fluid-absent melting of metabasaltic sources. However, water drives arc magmatism within Phanerozoic subduction zones and thus, understanding the behaviour of water in Archaean subduction zones, may have considerable value for understanding the genesis of these TTG magmas. Consequently, this study investigates the role of HP water-present melting of an eclogite-facies starting material, in the production of high-Al2O3 type TTG melts. Water-saturated partial melting experiments were conducted between 1.9 and 3.0GPa; and, 870°C and 900°C. The melting reaction is characterized by the breakdown of sodic Cpx, together with Qtz and H2O, to form melt in conjunction with a less sodic Cpx: Qtz + Cpx1 + Grt1 + H2O = Melt + Cpx2 + Grt2. In many of the experimental run products, melt segregated efficiently from residual crystals, allowing for the measurement of a full range of trace elements via Laser Ablation Inductively Coupled Plasma Mass Spectroscopy. The experimental glasses produced by this study have the compositions of peraluminous trondhjemites; and they are light rare earth element, Zr and Sr enriched; and heavy rare earth element, Y and Nb depleted. The compositions of the experimental glasses are similar to high-Al2O3 type

  11. 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

  12. A 2.5 G.a. reworked sialic crust: Rb-Sr ages and isotopic geochemistry of late archaean volcanic and plutonic rocks from E. Finland

    NASA Astrophysics Data System (ADS)

    Martin, Hervé; Querré, Guirec

    1984-03-01

    In east-central Finland, Archaean terrains present three main lithologic units: a) gneissic basement, emplaced from 2.86 G.a. to 2.62 G.a., b) greenstone belt (2.65 G.a.) and c) calc-alkaline magmatism (2.50 G.a. to 2.40 G.a). Twenty three rocks of the calc-alkaline suite have been chosen for geochronologic and Rb-Sr isotopic studies. These rocks are subdivided into three groups: 1) acid volcanics from Luoma, 2) augen gneiss from Arola, and 3) post kinematik pink leucogranite from Arola. The 2.50±0.10 G.a. age of the Luoma volcanics indicates that they represent the upper part of a greenstone belt composed of a single sequence of volcanic rocks. The ages, initial 87Sr/86Sr (ISr) and major element compositions of the augen gneisses of Arola and Suomussalmi indicate that these rocks are the plutonic equivalents of the Luoma acid volcanics. The Arola pink leucogranite marks the terminal phase of Archaean magmatic activity (from 2.86 G.a. to 2.41 G.a.). This was followed by at least 0.40 G.a. of quiescence. The ISr and major element compositions suggest that the genesis of the calc-alkaline magmatic rocks involved crustal materials, but all their geochemical features cannot be explained without the participation of mafic greenstone belt materials. The first crustal components had low I and low K2O/ Na2O ratios while the younger ones (calc-alkaline magmas) had medium to high ISr and high K2O/Na2O ratios. Thus the petrogenetic processes have changed with time from ensimatic to ensialic, implying major reworking of preexisting crustal materials. This evolution leads to the accretion of the continental crust from the mantle.

  13. U-Pb ages and geochemistry of mafic dyke swarms from the Uauá Block, São Francisco Craton, Brazil: LIPs remnants relevant for Late Archaean break-up of a supercraton

    NASA Astrophysics Data System (ADS)

    Oliveira, E. P.; Silveira, E. M.; Söderlund, U.; Ernst, R. E.

    2013-08-01

    The São Francisco Craton (SFC) is an Archaean craton that hosts a significant number of mafic intrusions. Previous attempts to date the igneous emplacement of these rocks are limited to a few dates of poor precision. Here, two dyke swarms from the Uauá Block in the northeastern portion of the craton were dated using U-Pb on baddeleyite (ID-TIMS) and zircon (SIMS). The older dyke swarm trends mainly N-S to NW-SE (but also NE) and comprises norite dykes, whereas the younger dykes are tholeiite and trend NE-SW. The ages of 2726.2 ± 3.2 and 2623.8 ± 7.0 Ma date dykes of noritic and tholeiitic compositions, respectively. The older age matches the ages of several Archaean-Large Igneous Provinces (tholeiitic-komatiite greenstone belts and continental flood basalts) worldwide and represents part of a feeder system, but the younger age is similar to Andean style continental margin magmatism in the São Francisco and Zimbabwe cratons. The two dyke swarms are tholeiitic in composition but the noritic dykes are more enriched in both compatible and incompatible elements and have higher (La/Yb)N ratios than the tholeiite dykes. The norite dykes are interpreted as low degrees of melting from enriched refractory mantle sources, whereas the tholeiite dykes represent high degrees of partial melting of more depleted mantle sources; the two mafic dyke swarms may be related to each other by progressive extension of the continental lithosphere. It is suggested that the Uauá Block with its dyke swarms is a small piece of Archaean crust dispersed after the break-up of a major Archaean supercraton.

  14. Geochemical diversity of late-Archaean Mg-K-rich mafic magmas (sanukitoids) and its implication for metasomatic processes between silicate melts and mantle peridotite

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The oldest high-Mg and high-K mafic magmas identified on Earth are the so-called sanukitoids that emplaced during the late-Archaean (3.0-2.5 Ga) in almost all cratonic domains worldwide. A compilation of >200 mafic to intermediate sanukitoid samples (mostly monzodiorites, quartz-diorites and quartz-monzonites with SiO2 = 45-62 wt.%), reveals that they clearly define two groups on the basis of their geochemistry: (1) low-Ti sanukitoids display moderate Ti, Fe as well as HFSE and REE contents, but high Mg# (0.55-0.70) and elevated concentrations in transition elements (Ni, Cr); (2) high-Ti sanukitoids, by contrast, are much richer in Ti, Fe, HFSE and LREE, but show significantly lower Mg# (0.45-0.55) as well as Ni and Cr contents. We investigated the origin of both series using geochemical modeling based on Monte-Carlo numerical simulations. As pointed out by previous work on experimental and natural systems [e.g. 1-2], our modeling indicates that both low- and high-Ti sanukitoids derive from the interactions, at mantle levels, between peridotite and a silicate melt. On the other hand, we demonstrated that (1) critical differences between low- and high-Ti sanukitoids (e.g. Ni, Cr, HFSE, REE contents) primarily results from two distinct mechanisms of melt-peridotite interactions; while (2) the nature of the metasomatic agent (either derived from metabasalts or metasediments in the models) only accounts for second-order variations within each group (e.g. K contents, Ba/Sr, La/Yb ratios and Eu anomaly). Specifically, the composition of low-Ti sanukitoids is best explained by a "one-step" hybridation of silicate melt with mantle peridotite, and is in equilibrium with a residual solid made up of garnet, clino- and orthopyroxene. By contrast, high-Ti sanukitoids likely derive from a "two-step" process: firstly, the silicate melt is fully consumed by interactions with peridotite, giving rise to a metasomatic, orthopyroxene-, amphibole- and phlogopite-rich assemblage. In

  15. 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. PMID:12761546

  16. 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

  17. Geochronology of the Archaean Kolmozero-Voron'ya Greenstone Belt: U-Pb dating of zircon, titanite, tourmaline and tantalite (Kola Region, North-Eastern BAltic Shield)

    NASA Astrophysics Data System (ADS)

    Kudryashov, N.; Gavrilenko, B.; Apanasevich, E.

    2003-04-01

    The Archaean Kolmozero-Voron’ya greenstone belt is one of the most ancient geological structures of the Kola Peninsula. It is located between Upper Archaean terrains: Murmansk, Central Kola and Keivy. Within the Kolmozero-Voron'ya greenstone belt there are rare metal (Li, Cs with accessory Nb, Ta, and Be), Cu, Mo, and Au deposits. All rocks were metamorphosed under amphibolite facies conditions and intruded by granodiorites, plagiomicrocline and tourmaline granites and pegmatite veins. Four suites are distinguished within the belt: lower terrigenous formation, komatiite-tholeite, basalt-andesite-dacite and upper terrigenous formation. The U-Pb age of 2925±6 Ma on magmatic zircon was obtained for leucogabbro of differentiated gabbro-anorthosite massif Patchemvarak, situated at the boundary between volcanic-sedimentary units and granitoids of the Murmansk block. This age is the oldest for gabbro-anorthosites of the Kola Peninsula. Sm-Nd age of komatiites is ca. 2.87 Ga (Vrevsky, 1996). U-Pb age of zircon from biotite schist, which belongs to acid volcanites is 2865+/-5 Ma. Quartz porphyries, which are considered to be an intrusive vein analogous of acid volcanites has an age of 2828+/-8 Ma, that marks the final stage of the belt development. Dating of titanite from ovoid plagioamphibolites yielded an U-Pb age of 2595+/-20 Ma that probably is connected with the closure of the U-Pb isotopic titanite system during the regional metamorphism. The Porosozero granodioritic complex with an age of 2733+/-6 Ma is located between granites of the Murmansk domain, migmatites and gneisses of the Central Kola terrain and the Keivy alkaline granites. Tourmaline granites are found all over the Kolmozero-Voron’ya belt occurring among volcanogenic-sedimentary rocks of the belt. Their Pb-Pb age of 2520+/-70 Ma appears to denote the tourmaline crystallization at a post-magmatic stage of the complex formation. U-Pb zircon age from rare metal pegmatites is 1.9-1.8 Ga. Zircons from

  18. 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

  19. Interplay between grain size reduction, chemical reaction, and shear localization in lower crustal rocks: a case study from Archaean Bundelkhand Craton, North-Central India

    NASA Astrophysics Data System (ADS)

    Bhandari, Ankit; Nasipuri, Pritam; Saha, Lopamudra; Pati, Jayanta Kumar; Sarkar, Saheli; Purohit, Rohan

    2016-04-01

    Weakening of the rocks is pronounced during the formation of shear zone. Crustal scale shear zones at the plate boundary develop due to grain size reduction, either by mechanical breakdown of minerals or by the development of new minerals due to change in pressure (P) - temperature (T) conditions. In either of the mechanisms for grain size reduction, the Gibb's free energy of the system should be minimum in value to stabilize the mineral.In this contribution, we have studied the deformation mechanism and P-T conditions from acrustal scale shear zone, in the North Central Part of Archaean Bundelkhand Craton. In the Archaean Buldelkhand craton, tens of kilometre wide E-W trending shear zone developed in the sodic-potassic granite. The undeformed rock (protolith) is characterized by euhedral to subhedral sodic feldspar (XAb =0.80) and subordinate quartz, whereas the deformed rock is characterized by the development of extremely deformed feldspar and quartz associated with chlorite. The onset of the strain localization and shear zone formation in the proto-mylonite has been accompanied by developing brittle fractures in the euhedral feldspar grains. In contrast to the brittle deformation in feldspar, quartz grains are characterized by development of small bulges around the grain boundary. Chlorite develops at the fractures in the feldspar that are indicative of fluid infiltration in the proto-mylonite.In the extremely deformed samples (ultramylonite) grain size reduction occurs by bulging recrystallization in quartz. Flow stress obtained from grain size analysis of quartz indicates that the palaeo-stress varies from ~44-46 MPa in proto-mylonite to ~ 61-63 MPa in Ultra-mylonite. Mineral chemical analysis of undeformed feldspar grains in the protolith and mylonite indicate significant changes in the chemical composition that leads to minimum Gibbs energy. Also the presence of chlorite indicates hydration reaction, which has reduced the chemical energy of the system

  20. Carbonaceous Microstructures of the 3.46 Ga Stratiform `Apex Chert', Pilbra, Western Australia: Presenting a New Suite of Early Archaean Microbially Induced Sedimentary Structures

    NASA Astrophysics Data System (ADS)

    Hickman-Lewis, K.; Garwood, R. J.; Brasier, M. D.; Goral, T.; Jiang, H.; McLoughlin, N.; Wacey, D.

    2016-05-01

    We present morphological and geochemical evidence for a new suite of MISS from the stratiform Apex chert. Four potential biosignatures are identified in this marine unit: laminated clasts, roll-ups, flaky grains and persistent filamentous laminae.

  1. 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.

  2. 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

  3. The role of crustal fluids in the tectonic evolution of the Eastern Goldfields Province of the Archaean Yilgarn Craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Drummond, B. J.; Hobbs, B. E.; Goleby, B. R.

    2004-12-01

    Gold deposits in the Archaean Eastern Goldfields Province in Western Australia were deposited in greenstone supracrustal rocks by fluids migrating up crustal scale fault zones. Regional ENE-WSW D2 shortening of the supracrustal rocks was detached from lower crustal shortening at a regional sub-horizontal detachment surface which transects stratigraphy below the base of the greenstones. Major gold deposits lie close to D3 strike slip faults that extend through the detachment surface and into the middle to lower crust. The detachment originally formed at a depth near the plastic-viscous transition. In orogenic systems the plastic-viscous transition correlates with a low permeability pressure seal separating essentially lithostatic fluid pressures in the upper crust from supralithostatic fluid pressures in the lower crust. This situation arises from collapse in permeability below the plastic-viscous transition because fluid pressures cannot match the mean stress in the rock. If the low permeability pressure seal is subsequently broken by a through-going fault, fluids below the seal would flow into the upper crust. Large, deeply penetrating faults are therefore ideal for focussing fluid flow into the upper crust. Dilatant deformation associated with sliding on faults or the development of shear zones above the seal will lead to tensile failure and fluid-filled extension fractures. In compressional orogens, the extensional fractures would be subhorizontal, have poor vertical connectivity for fluid movement and could behave as fluids reservoirs. Seismic bright spots at 15-25 km depth in Tibet, Japan and the western United States have been described as examples of present day water or magma concentrations within orogens. The likely drop in rock strength associated with overpressured fluid-rich zones would make this region just above the plastic-viscous transition an ideal depth range to nucleate a regional detachment surface in a deforming crust.

  4. 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.

  5. Intra-sill magmatic evolution in the Cummings Complex, Abitibi greenstone belt: Tholeiitic to calc-alkaline magmatism recorded in an Archaean subvolcanic conduit system

    NASA Astrophysics Data System (ADS)

    Bédard, Jean H.; Leclerc, François; Harris, Lyal B.; Goulet, Normand

    2009-07-01

    The stratigraphy of the Abitibi greenstone belt in the Chibougamau area (southern Superior Province, Québec), is dominated by 2 cycles of mafic-felsic metavolcanic and metasedimentary rocks constituting the Roy Group, which is riddled by metagabbroic sills (25%). The Doré Lake Complex (DLC, 2728 Ma) is emplaced into the lower Roy Group. The Cummings Complex sills (2717 Ma) were injected between the Bruneau member and Blondeau Formations of the 2nd Roy Group cycle. The sills of the Cummings Complex (Roberge, Ventures and Bourbeau Sills) contain metaperidotite, metapyroxenite, metagabbro and metagranophyric facies. The trace element contents of melts in equilibrium with these metacumulate rocks were calculated and are compared to Roy Group lavas to clarify the regional magmatic history. Many DLC model melts have fractionated trace element profiles, with LILE-LREE-enrichment, HREE-depletion, and negative Nb-Ta-anomalies suggesting that the DLC formed largely from calc-alkaline melts extracted from garnet-bearing residues. The DLC is coeval with, and shows geochemical resemblances to Waconichi Formation tuffs (the felsic cap of the 1st Roy Group cycle), suggesting it could represent the Waconichi's shallow magma chamber. Meta-anorthosite rafts from the para-autochtonous zone of the Grenville province yield model melts closely resembling those of the DLC and are correlated on this basis. Most Roy Group sills yield model melts with trace element patterns typical of Archaean tholeiites, suggesting they fed the regionally-dominant tholeiitic volcanic plain lavas of the Roy Group. Models for the Cummings Complex imply that it contained two types of magma. Model melts from the Roberge Sill have strongly fractionated calc-alkaline-like trace element patterns, while those of the Ventures and Bourbeau Sills are mostly flat, N-MORB-normalized tholeiitic-like patterns that cannot be derived from the Roberge Sill melts by fractional crystallization. The Roberge Sill must have a

  6. 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. PMID:17008214

  7. 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

  8. Diversity of 1.8 Ga potassic granitoids along the edge of the Archaean craton in northern Scandinavia: a result of melt formation at various depths and from various sources

    NASA Astrophysics Data System (ADS)

    Öhlander, Björn; Skiöld, Torbjörn

    1994-11-01

    The edge of the Archaean craton in northern Scandinavia had been intensively reworked during the Svecofennian orogeny 1.93-1.86 Ga ago and was subsequently intruded by potassic granitoids of 1.79-1.80 Ga age. Despite similar or even identical ages and overlapping areas of occurrence, these rocks belong to two different groups, the Edefors and Lina granitoids, which have contrasting geochemistries and SmNd isotopic characteristics. The Edefors granitoids range from syenites to granites, and are alkali-rich and distinctly metaluminous. They crystallized from dry magmas. This is indicated by the scarcity of pegmatites and aplites. The contacts to older rocks are often distinct, but gradual transitions to Lina-type granitoids are common. The Edefors granitoids have high contents of Zr but not of elements such as Y, REE, Ta and Nb, and have low {Mg}/{Mg+Fe} ratios. They also frequently have positive Eu anomalies, even in the quartz rich varieties. Initial ɛNd values range from -2.1 to +1.4, indicating that the Edefors granitoids were formed by the mixing of mantle-derived magmas and continental crustal materials. The amount of crustal component was probably less than 35% in most cases. The Lina granitoids are accompanied by abundant pegmatites and aplites. Ghost structures and remnants of country rock are common. True granites predominate, but also quartz monzonites occur. The content of HFS elements is low and the {Mg}/{Mg+Fe} ratios are higher than in the Edefors granitoids. Initial ɛNd values range from -9.3 to -3.7, reflecting a significant portion of Archaean Nd in the source materials. The Lina granitoids are largely the result of remobilisation of continental crust with a small input of juvenile material. However, the dominant source for these crustally derived granitoids are c. 1.9 Ga old granitoids. These carry a large proportion of Archaean Nd. The most probable environment of the formation of potassic migmatite granitoids, such as the Lina type, is a

  9. Combined 40Ar/39Ar and Fission-Track study of the Freetown Layered Igneous Complex, Freetown, Sierra Leone, West Africa: Implications for the Initial Break-up of Pangea to form the Central Atlantic Ocean and Insight into the Post-rift Evolution of the Sie

    NASA Astrophysics Data System (ADS)

    Barrie, Ibrahim; Wijbrans, Jan; Andriessen, Paul; Beunk, Frank; Strasser-King, Victor; Fode, Daniel

    2010-05-01

    Sierra Leone lies within the south-western part of the West African Craton and comprises two major Archaean structural divisions: a low-grade granite-greenstone terrane characterised by N-S striking structures and a NW-SE striking highly metamorphosed belt of strained rocks that form the coastal margin of the craton. Intruded into the belt is the Freetown Layered Igneous Complex (FLIC), a tholeiitic magamtic body emplaced prior to or during the break-up of Pangea to form the Central Atlantic Ocean and, forming today the high ground of the coastal outline of Sierra Leone which is one of the most distinctive features on the West African coast. The break-up of Pangaea to form the Central Atlantic and its passive margins began in the Early Jurassic. Geo-tectonically, the break-up was particularly characterised by the formation of the Central Atlantic Magmatic Province (CAMP), covering once-contiguous parts of North America, Europe, Africa and South America. The FLIC forming part of the heart of CAMP is the largest single layered igneous intrusive yet known on either side of the Central Atlantic, measuring on surface, 65 x 14 x 7 km. Geophysical investigations indicate that the intrusion extends offshore to a depth of about 20 km. Geologically the Complex is a rhythmically layered elongated ultramafic-mafic lopolith divisible into 4 major zones each comprising repeated sequences of troctolitic, gabbroic and anorthositic rocks. An idealised unit of layering is from base upwards: dunite, troctolite, olivine-gabbro, leuco-gabbro, gabbro-norite and anorthosite cumulates. 40Ar-39Ar age spectra and 40Ar/36Ar versus 39Ar/36Ar isochron plots obtained by stepwise-heating experiments on plagioclases, biotites and amphiboles from troctolites, olivine-gabbros, gabbro-norites and anorthosites of the four zones yield plateau and isochron ages that seem to depict the cooling history of the Complex after emplacement. The biotites and some of the plagioclases and amphiboles give very

  10. 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.

  11. Development of the earth-moon system with implications for the geology of the early earth

    NASA Technical Reports Server (NTRS)

    Smith, J. V.

    1976-01-01

    Established facts regarding the basic features of the earth and the moon are reviewed, and some important problems involving the moon are discussed (extent of melting, time of crustal differentiation and nature of bombardment, bulk chemical composition, and nature and source of mare basins), with attention given to the various existing theories concerning these problems. Models of the development of the earth-moon system from the solar nebula are examined, with particular attention focused on those that use the concept of capture with disintegration. Impact processes in the early crust of the earth are briefly considered, with attention paid to Green's (1972) suggestion that Archaean greenstone belts may be the terrestrial equivalent of lunar maria.

  12. Geochronological and isotopic evidence for early Proterozoic crust in the eastern Arabian Shield.

    USGS Publications Warehouse

    Stacey, J.S.; Hedge, C.E.

    1984-01-01

    Zircon U/Pb, feldspar common Pb, whole-rock Sm/Nd, and Rb/Sr data indicate that the fine-grained granodiorite (Z103) has yielded conclusive evidence for rocks of early Proterozoic age in the eastern Arabian Shield (21o19' N, 44o50' W). Z103 may have been emplaced approx 1630 m.y. ago and subsequently was severely deformed or perhaps even remobilized at approx 660 m.y. Furthermore, lead isotope data, along with other evidence, show that the 1630 m.y. crustal rocks inherited material from an older, probably Archaean, source at the time of their formation. At that time addition of mantle material considerably modified the Rb-Sr and Sm-Nd systems so that they now yield similar, or only slightly older apparent ages (1600-1800 m.y.).-L.diH.

  13. 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.

  14. The relationship between adakitic, calc-alkaline volcanic rocks and TTGs: implications for the tectonic setting of the Karelian greenstone belts, Baltic Shield

    NASA Astrophysics Data System (ADS)

    Samsonov, A. V.; Bogina, M. M.; Bibikova, E. V.; Petrova, A. Yu.; Shchipansky, A. A.

    2005-01-01

    Two types of coeval acid-intermediate rocks with different petrological, geochemical and isotopic features have been discovered among volcanic rocks and surrounding synkinematic tonalite-trondhjemite-granodiorite (TTG) plutons of Late Archaean greenstone belts in the Karelian granite-greenstone terrane. Type-1 rocks comprise trondhjemites and sub-volcanic, occasionally volcanic dacite-rhyolite rocks. They are characterized by high Sr, low Y and HREE contents, high Sr/Y ratios, and strongly fractionated REE patterns with no significant positive or negative Eu anomaly. Initial ɛNd is positive, indicating a generation from juvenile source with little or no contribution of ancient continental crust. Type 2 is represented by diorite-granodiorites and calc-alkaline basalt-andesite-dacite-rhyolite (BADR) series. As compared to type 1, these rocks differ by their lower Sr, higher Y and HREE contents, lower Sr/Y ratios and less fractionated HREE patterns with negative Eu anomalies. Initial ɛNd varies from negative to positive values, thus indicating a variable contribution of sialic crust. Geochemistry of the two magmatic series suggests their formation in a convergent plate margin setting. The type-1 rocks resemble Phanerozoic adakites, which represent slab-derived melts contaminated by overlying mantle wedge. The type-2 rocks resemble BADR series, which were derived from a mantle wedge metasomatized by slab-derived fluids and melts, with subsequent variable crustal contamination. The spatial distribution of these two types of magmatic series defines the asymmetry of the studied granite-greenstone structures, which presumably reflects the primary lateral zoning of island arc formed under specific thermal conditions in the Archaean mantle. Adakite melts upraised to the surface in the frontal part of the island arc, where mantle wedge was thin, showing no or little interaction with metasomatized mantle, and formed adakite-type plutonic and sub-volcanic rocks. At greater

  15. Petrology of the anorogenic, oxidised Jamon and Musa granites, Amazonian Craton: implications for the genesis of Proterozoic A-type granites

    NASA Astrophysics Data System (ADS)

    Dall'Agnol, Roberto; Rämö, O. Tapani; de Magalhães, Marilia Sacramento; Macambira, Moacir José Buenano

    1999-03-01

    The 1.88 Ga Jamon and Musa granites are magnetite-bearing anorogenic, A-type granites of Paleoproterozoic age. They intrude the Archaean rocks of the Rio Maria Granite-Greenstone Terrain in the eastern part of the Amazonian Craton in northern Brazil. A suite of biotite±amphibole monzogranite to syenogranite, with associated dacite porphyry (DP) and granite porphyry (GP) dykes, dominates in these subalkaline granites that vary from metaluminous to peraluminous and show high FeO/(FeO+MgO) and K 2O/Na 2O. In spite of their broad geochemical similarities, the Jamon and Musa granites show some significant differences in their REE patterns and in the behaviour of Y. The Jamon granites are related by fractional crystallisation of plagioclase, potassium feldspar, quartz, biotite, magnetite±amphibole±apatite±ilmenite. Geochemical modelling and Nd isotopic data indicate that the Archaean granodiorites, trondhjemites and tonalites of the Rio Maria region are not the source of the Jamon Granite and associated dyke magmas. Archaean quartz diorites, differentiated from the mantle at least 1000 m.y. before the emplacement of the granites, have a composition adequate to generate DP and the hornblende-biotite monzogranite magmas by different degrees of partial melting. A larger extent of amphibole fractionation during the evolution of the Musa pluton can explain some of the observed differences between it and the Jamon pluton. The studied granites crystallised at relatively high fO 2 and are anorogenic magnetite-series granites. In this aspect, as well as concerning geochemical characteristics, they display many affinities with the Proterozoic A-type granites of south-western United States. The Jamon and Musa granites differ from the anorthosite-mangerite-charnockite-rapakivi granite suites of north-eastern Canada and from the reduced rapakivi granites of the Fennoscandian Shield in several aspects, probably because of different magmatic sources.

  16. Restoring the supercontinent Columbia and tracing its fragments after its breakup: A new configuration and a Super-Horde hypothesis

    NASA Astrophysics Data System (ADS)

    Yakubchuk, Alexander

    2010-09-01

    Paleoproterozoic collisional (internal) and accretionary (external) orogens, additionally constrained by the matches between the Archaean granulite-gneiss and granite-greenstone terranes, are used to reconstruct the Mesoproterozoic supercontinent Columbia. The Archaean granulite-gneiss terranes occupy an axial position, forming the Archaean Super-Horde, traceable through almost all present cratons. Restored Columbia is a 30,000 km long supercontinent, assembled by ca 1.85 Ga. There is no evidence of its breakup during the Mesoproterozoic, and it subsequently grew via external accretion until ca. 1.25 Ga. After 1.25 Ga, the Atlantica group of cratons was split from Columbia and rotated to collide with the remaining intact part of Columbia to produce the 1.0 Ga Grenville orogen, hence assembling the supercontinent Rodinia. At 1000-720 Ma, penetration of oceanic spreading centres into Rodinia between Siberia and the Australian cratons split the remaining part of Columbia into the Ur and Nena cratonic groups. Nena was then quickly rifted apart into Laurentia, Eastern Europe, and Siberia. Siberia started its drift from the present western edge of Laurentia towards Eastern Europe. This drift might have caused the separation from Nena of parts of the Palaeoproterozoic external orogen to form the Great Steppe superterrane, which later was assimilated into the basement of Neoproterozoic to Palaeozoic magmatic arcs with adjacent backarc oceanic basins, whose fragments are at present found inside the Central Asia supercollage. Simultaneously with Siberia, the remaining intact Ur began moving in the opposite direction around Atlantica. During this translation, Atlantica was fragmented into Congo-Tanzania, West Africa, Amazonia and Rio-de-la-Plata with opening of the internal Brasiliano oceanic basin and its subsequent suturing. This closure might have happened due to the arrival of Ur, whose Kalahari and India portions collided with Congo-Tanzania to produce the Damara and

  17. 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.

  18. Potential Habitats For Life On Mars: Lessons From The Early Archean

    NASA Astrophysics Data System (ADS)

    Westall, F.; Brack, A.

    The Hadean/Early Archaean Earth was characterised by generally submerged protocontinents on a water-covered planet. The supracrustal rocks deposited on top of the protocontinents from the Early Archaean terrains of Barberton (S. Africa) and the Pilbara (Australia) contain evidence of widespread distributions of fossil bacterial biofilms in almost all the habitats available. These include shallow -water, intertidal (saline), and possibly subaerial environments. There is extensive evidence of hydrothermal activity with associated mats in all habitats. We can thus infer that by 3.4-3.5 b.y. ago, terrestrial organisms probably represented chemolithotrophs, heterotrophs and anaerobic photosynthesisers exhibiting thermophilic, acidophilic (possibly alkalophilic?), or halophyilic attributes. The presence of a unifying body of water on Earth could have been an important aid to microbial dispersal between habitats. The geological evolution of Mars, on the other hand, precludes the formation of oceans and (proto)continents, even though there is evidence for significant liquid water at the surface of the planet during the Noachian and early Hesperion, with intermittent appearances during the later Hesperion and Amazonian. How does this important difference in the geological evolution of the two planets affect the possibility of life on Mars? In fact, since the ingredients for life (water, organics and an energy source) were all present on early Mars, and since microorganisms are purely surface-specific, the major geological differences present no inhibition to the appearance of life. Potential habitats include: hot spring, shallow -water, intertidal (saline/alkaline?), subaerial and subsurface environments; potential types of organisms would be chemolithotrophs, heterotrophs and (anaerobic?) photosynthesisers with thermophilic, mesophilic (later on psychrophilic?), acidophilic (alkalophilic?), or halophilic attributes. However, subsequent evolution during the Noachian would

  19. Early years.

    PubMed

    2011-04-01

    Healthcare professionals in Scotland who are involved in early years work now have an additional resource in the shape of NHS Scotland's Maternal and Early Years website, aimed at practitioners at all levels. The site includes evidence updates, news and events, and can be accessed at www.maternal-and-early-years.org.uk. PMID:27368523

  20. [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 Coordination: Families,…

  1. Early Intervention.

    ERIC Educational Resources Information Center

    Abery, Brian, Ed.; McConnell, Scott, Ed.

    1989-01-01

    This "feature issue" focuses on early intervention with handicapped children, with an emphasis on: Project EDGE (Expanding Developmental Growth through Education), an early intervention research project initiated in 1968; strategies for developing family-friendly early intervention services; and progress reports from various states and programs.…

  2. 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.

  3. 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.

  4. 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).

  5. 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

  6. Early Days

    ERIC Educational Resources Information Center

    Mathematical Gazette, 1971

    1971-01-01

    Reprinted are articles related to the early years of The Mathematical Association of Great Britain. Some of the topics include reports from curriculum committees, tributes to persons associated with The Mathematical Association, and the teaching of mathematics. (CT)

  7. New chronology for the southern Kalahari Group sediments with implications for sediment-cycle dynamics and early hominin occupation

    NASA Astrophysics Data System (ADS)

    Matmon, Ari; Hidy, Alan J.; Vainer, Shlomy; Crouvi, Onn; Fink, David; Erel, Yigal; Arnold, M.; Aumaître, G.; Bourlès, D.; Keddadouche, K.; Horwitz, Liora K.; Chazan, Michael

    2015-07-01

    Kalahari Group sediments accumulated in the Kalahari basin, which started forming during the breakup of Gondwana in the early Cretaceous. These sediments cover an extensive part of southern Africa and form a low-relief landscape. Current models assume that the Kalahari Group accumulated throughout the entire Cenozoic. However, chronology has been restricted to early-middle Cenozoic biostratigraphic correlations and to OSL dating of only the past ~ 300 ka. We present a new chronological framework that reveals a dynamic nature of sedimentation in the southern Kalahari. Cosmogenic burial ages obtained from a 55 m section of Kalahari Group sediments from the Mamatwan Mine, southern Kalahari, indicate that the majority of deposition at this location occurred rapidly at 1-1.2 Ma. This Pleistocene sequence overlies the Archaean basement, forming a significant hiatus that permits the possibility of many Phanerozoic cycles of deposition and erosion no longer preserved in the sedimentary record. Our data also establish the existence of a shallow early-middle Pleistocene water body that persisted for > 450 ka prior to this rapid period of deposition. Evidence from neighboring archeological excavations in southern Africa suggests an association of high-density hominin occupation with this water body.

  8. Contrasting petrogenesis of Mg-K and Fe-K granitoids and implications for post-collisional magmatism: case study from the late-Archaean Matok pluton (South Africa)

    NASA Astrophysics Data System (ADS)

    Laurent, Oscar; Rapopo, Mafusi; Stevens, Gary; Moyen, Jean-François; Martin, Hervé; Zeh, Armin; Doucelance, Régis

    2014-05-01

    , and Mg-K suites, such as sanukitoids, the petrogenesis of which only requires metasomatized mantle. We propose that the most adequate geodynamic setting for the involvement of these two mantle sources is a postsubduction, collision-related slab breakoff event. Such a model accounts for (1) the postcollisional nature of both Mg-K (sanukitoids) and Fe-K magmas; (2) their close spatial and temporal relationships in several late-Archaean to Phanerozoic terranes; and (3) their differences in petrography and geochemistry. In addition, such a model also accounts for many other typical features of the late-collisional context, such as high-T metamorphism and large-scale melting of the orogenic crust, in response to thermal stabilization of the lithosphere and intrusion of mafic melts at shallow levels.

  9. Early Math.

    ERIC Educational Resources Information Center

    Van Nuys, Ute Elisabeth

    1986-01-01

    Presents reviews of the following mathematics software designed to teach young children counting, number recognition, visual discrimination, matching, addition, and subtraction skills; Stickybear Numbers, Learning with Leeper, Getting Ready to Read and Add, Counting Parade, Early Games for Young Children, Charlie Brown's 1,2,3's, Let's Go Fishing,…

  10. 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.

  11. 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…

  12. The 3.26-3.24 Ga Barberton asteroid impact cluster: Tests of tectonic and magmatic consequences, Pilbara Craton, Western Australia

    NASA Astrophysics Data System (ADS)

    Glikson, Andrew; Vickers, John

    2006-01-01

    movements in Archaean granite-greenstone terrains associated with large asteroid impacts, culminating in transformation from sima-dominated crust to continental rift environments.

  13. 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.

  14. 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: ...

  15. 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

  16. Dismembered Archaean ophiolite in the southeastern Wind River Mountains, Wyoming: Remains of Archaean oceanic crust

    NASA Technical Reports Server (NTRS)

    Harper, G. D.

    1986-01-01

    Archean mafic and ultramafic rocks occur in the southeastern Wind River Mountains near Atlantic City, Wyoming and are interpreted to represent a dismembered ophiolite suite. The ophiolitic rocks occur in a thin belt intruded by the 2.6 Ga Louis Lake Batholith on the northwest. On the southeast they are in fault contact with the Miners Delight Formation comprised primarily of metagraywackes with minor calc-alkaline volcanics. The ophiolitic and associated metasedimentry rocks (Goldman Meadows Formation) have been multiply deformed and metamorphosed. The most prominant structures are a pronounced steeply plunging stretching lineation and steeply dipping foliation. These structural data indicate that the ophiolitic and associated metasedimentary rocks have been deformed by simple shear. The ophiolitic rocks are interpreted as the remains of Archean oceanic crust, probably formed at either a mid-ocean ridge or back-arc basin. All the units of a complete ophiolite are present except for upper mantle periodotities. The absence of upper mantle rocks may be the result of detactment within the crust, rather than within the upper mantle, during emplacement. This could have been the result of a steeper geothermal gradient in the Archean oceanic lithosphere, or may have resulted from a thicker oceanic crust in the Archean.

  17. 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

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

    PubMed

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

    2011-12-01

    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. PMID:22129728

  19. 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.

  20. 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.

  1. Follow the Carbon: Laboratory Studies of 13C-Labeled Early Earth Haze Analogs

    NASA Astrophysics Data System (ADS)

    Hicks, R. K.; Day, D. A.; Mojzsis, S. J.; Jimenez, J. L.; Tolbert, M. A.

    2013-12-01

    While the Sun was still young and faint before the rise of molecular oxygen 2.4 Ga, early Earth might have been kept warm by an atmosphere containing the greenhouse gases methane and carbon dioxide in abundances greater than what is found on Earth today. It has been suggested that an atmosphere containing approximately 1000 ppmv methane and carbon dioxide could provided the needed greenhouse warming for liquid water to exist at the surface. Laboratory and modeling studies suggest that an atmosphere containing methane and carbon dioxide could lead to the formation of significant amounts of organic haze due to photochemical reactions initiated by Lyman-α (121.6 nm) excitation. Chemical mechanisms proposed to explain the chemistry rely on methane as the source of carbon in these hazes and treat carbon dioxide as a source of oxygen only. In the present work, we use isotopically labelled precursor gases to examine the source of carbon in photochemical haze formed in a CH4/CO2/N2 atmosphere. We generate haze analogs in the laboratory by far-UV irradiation of analog atmospheres containing permutations of 1,000 ppmv unlabeled and 13C-labeled methane and carbon. Products in the particle phase were analyzed by both unit mass resolution and high-resolution (m/Δm=5,000) aerosol mass spectrometry. Results indicate that carbon from carbon dioxide accounts for 20% (×5%) of the total carbon contained in the hazes. These results have implications for the geochemical interpretations of inclusions found in Archaean rocks on Earth, and for the astrobiological potential of other planetary atmospheres.

  2. 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…

  3. 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…

  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. Tooth decay - early childhood

    MedlinePlus

    Bottle mouth; Bottle carries; Baby bottle tooth decay; Early childhood caries (ECC) ... chap 304. Ribeiro NM, Ribeiro MA. Breastfeeding and early childhood caries: a critical review. J Pediatr (Rio J) . ...

  6. 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

  7. 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…

  8. 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" (EYLF) (DEEWR, 2009)…

  9. Early-Onset Alzheimer's

    MedlinePlus

    MENU Return to Web version Early-Onset Alzheimer’s What is early-onset Alzheimer’s disease? Early-onset Alzheimer’s disease is when Alzheimer’s affects a person younger than 65 years of age. People ...

  10. 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…

  11. Early Learning Content Standards

    ERIC Educational Resources Information Center

    Ohio Department of Education, 2004

    2004-01-01

    The early learning content standards describe essential concepts and skills for young children. Based on research, these achievable indicators emerge as the result of quality early learning experiences regardless of the setting (e.g., nursery school, preschool, family care, etc.). In addition, the early learning content indicators are aligned to…

  12. Archaean and Palaeoproterozoic gneisses reworked during a Neoproterozoic (Pan-African) high-grade event in the Mozambique belt of East Africa: Structural relationships and zircon ages from the Kidatu area, central Tanzania

    NASA Astrophysics Data System (ADS)

    Vogt, M.; Kröner, A.; Poller, U.; Sommer, H.; Muhongo, S.; Wingate, M. T. D.

    2006-06-01

    This study presents new zircon ages and Sm-Nd whole-rock isotopic compositions for high-grade gneisses from the Udzungwa Mountain area in the central part of the Mozambique belt, Tanzania. The study area comprises a succession of layered granulite-facies para- and orthogneisses, mostly retrograded to amphibolite-facies. The original intrusive contacts became obscured or severely modified during non-coaxial ductile deformation, and extensive shearing occurred during retrogression. Structures reflecting the early deformational history were mostly obscured when the rocks were transported into the lower crust as documented by severe flattening. Only the fragmented gneisses in the eastern part of the area testify to a brittle regime. Structures in narrow low strain zones that predate the currently observed layering are preserved in rootless isoclinal folds and boudins. Magmatic and detrital zircons from tonalitic to felsic orthogneisses and a metapelite sample were dated using the U-Pb and Pb-Pb evaporation methods and SHRIMP II. Cathodoluminiscence images reveal ubiquitous xenocrystic cores, rimmed by clear, unzoned overgrowth due to high-grade metamorphism. Discordant U-Pb data therefore reflect core-rim relationships, and it was not always possible to obtain precise crystallisation ages. The analyses reveal Neoarchaean, Palaeoproterozoic and Neoproterozoic protolith ages. Nd isotopic systematics yielded strongly negative ɛNd( t) -values and Neoarchaean to Palaeoproterozoic model ages, even for gneisses emplaced in the Neoproterozoic. The trace element distribution suggests upper crustal derivation of the gneisses. Therefore, our study provides evidence that recycling of older crust played a major role during the evolution of the Kidatu area. Neoarchaean rocks are interpreted to represent fragments of the Tanzania craton. Our results, together with those of earlier workers, lead to the conclusion that the central part of the Mozambique belt mainly consists of ancient

  13. Production of nitrogen oxides by lightning in a methane-rich early atmosphere

    NASA Astrophysics Data System (ADS)

    Navarro, Karina; Navarro-Gonzalez, Rafael; McKay, Christopher

    2013-04-01

    production of methylnitrate by lightning in the early atmosphere. Further analyses are underway to accurately determine the production rates of these nitrogen oxides by lightning, and to understand their role for chemical evolution and early Earth's climate. Zahnle, K. J. Photochemistry of methane and the formation of hydrocyanic acid (HCN) in the Earths early atmosphere. J. Geophys. Res. 91, 2819-2834 (1986); [2] Tian, F., Kasting, J.F., and Zahnle, K. Revisiting HCN formation in Earth's early atmosphere. Earth Planet. Sci. Lett. 308, 417-423 (2011); [3] Navarro-González, R., McKay, C.P. and Nna Mvondo, D. A possible nitrogen crisis for archaean life due to reduced nitrogen fixation by lightning, Nature 412, 61-64 (2001); [4] Levine, J.S., Hughes, R.E., Chameides, W.L., and Howell, W.E. N20 and CO Production by Electrical Discharges: Atmospheric Implications, Geophys. Res. Lett.,6, 557-559 (1979); [5] Nna Mvondo, D. Navarro-González, R, McKay, C.P., Coll, P. and Raulin, F. Production of nitrogen oxides by lightning and coronae discharges in simulated early Earth, Venus and Mars environments. Adv Space Res. 27(2), 217-223 (2001).

  14. 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

  15. Early Intervention in Budapest.

    ERIC Educational Resources Information Center

    Gallai, Maria; Katona, Ferenc; Balogh, Erzsebet; Schultheisz, Judit; Deveny, Anna; Borbely, Sjoukje

    2000-01-01

    This article presents five models of early intervention used in Budapest. Diagnostic and treatment methods used by the Pediatric Institute and the Conductive Education System are described, along with the Deveny Special Manual Technique and Gymnastic Method, the Gezenguz method and techniques used in the Early Developmental Center. (CR)

  16. Cone Early Maturity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hop cone early maturity is thought to be caused by diffuse infections of cone, just prior to harvest, by Podosphaera macularis. The disease is best managed by limiting the amount of leaf infection by P. macularis prior to bloom. The yield and quality reductions associated with Hop cone early matur...

  17. 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…

  18. 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. This book…

  19. 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…

  20. US EARLY PRIDE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Agricultural Research Service Department of Agriculture, hereby releases for propagation the US EARLY PRIDIE citrus scion selection, formerly tested as 1-62-122. US EARLY PRIDE resulted from irradiation of Fallglo budwood by C.J. Hearn in 1991 at the U.S. Horticultural Research Laboratory in Or...

  1. 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…

  2. 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…

  3. Latest Precambrian to Early Cambrian U-Pb zircon ages of augen gneisses from Calabria (Italy), with inference to the Alboran microplate in the evolution of the peri-Gondwana terranes

    NASA Astrophysics Data System (ADS)

    Micheletti, Francesca; Barbey, Pierre; Fornelli, Annamaria; Piccarreta, Giuseppe; Deloule, Etienne

    2007-10-01

    In situ U-Pb dating of zircons from five samples of Calabrian augen gneisses shows that their protoliths are Latest Precambrian to Early Cambrian in age (562 ± 15, 547 ± 7, 540 ± 4, 539 ± 16 and 526 ± 10 Ma), and contain Archaean (3.1 Ga), Palaeoproterozoic (1.7-2.4 Ga) and Neoproterozoic (0.6-0.9 Ga) inheritance. Geochemical signature of augen gneisses is typical of high-K calc-alkaline post-collisional magmatism. Their Sr-Nd isotopic compositions [0.7093 < (87Sr/86Sr)i < 0.7139; -3.2 < ɛNd(t) < -5.4; 1.5 < T DM < 1.7 Ga] indicate the involvement of a crustal component in significant proportions. The Calabrian augen gneisses have, therefore, to be distinguished from the orthogneisses of Sardinia and northern Algeria, and from the porphyroids of Sicily, which are Middle Ordovician. By contrast, the Calabrian augen gneisses show a close similarity to the Pan-African post-collisional granitoids of the northern edge of the West African craton (e.g. the Moroccan Anti-Atlas). This suggests a peri-Gondwana origin and corroborates previous palaeogeodynamic reconstructions attributing the Alboran microplate to the northern margin of the West African craton.

  4. [Early rheumatoid arthritis].

    PubMed

    Babić-Naglić, Durdica

    2008-01-01

    Rheumatoid arthritis (RA) is chronic joint disease which if untreated leads to permanent structural damage and disability. Early diagnosis and therapy are the main requests for good clinical practice. Early diagnosis tools include specific clinical assesment, serological, immunogenetic and radiological evaluation. Disease activity score is cornerstone in clinical assesment, rheumatoid factor and anti-cyclic citrullinated peptide antibodies (anti-CCP) are very specific serological parameters. The shared epitope containing HLA-DRB1* alleles represent the most significant genetic risk for RA. Magnetic resonance and ultrasound imaging are very sensitive methods in early phase of disease. PMID:19024271

  5. 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

  6. 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:

  7. 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:

  8. 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)

  9. 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.

  10. Improving Early School Success.

    ERIC Educational Resources Information Center

    Pianta, Robert C.; La Paro, Karen

    2003-01-01

    Several large-scale research efforts imply that improving instructional quality rather than assessing student readiness is a better way to promote student performance in the early grades. (Contains 12 references.) (Author/MLF)

  11. Overview of Early Intervention

    MedlinePlus

    ... process. Back to top The evaluation and assessment process Service coordinator | Once connected with either Child Find ... service coordinator who will explain the early intervention process and help you through the next steps in ...

  12. Early Prediction of Preeclampsia

    PubMed Central

    Poon, Leona C.; Nicolaides, Kypros H.

    2014-01-01

    Effective screening for the development of early onset preeclampsia (PE) can be provided in the first-trimester of pregnancy. Screening by a combination of maternal risk factors, uterine artery Doppler, mean arterial pressure, maternal serum pregnancy-associated plasma protein-A, and placental growth factor can identify about 95% of cases of early onset PE for a false-positive rate of 10%. PMID:25136369

  13. 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.

  14. 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.

  15. Combined 40Ar/39Ar and Fission-Track study of the Freetown Layered Igneous Complex, Freetown, Sierra Leone, West Africa: Implications for the Initial Break-up of Pangea to form the Central Atlantic Ocean and Insight into the Post-rift Evolution of the Sie

    NASA Astrophysics Data System (ADS)

    Barrie, Ibrahim; Wijbrans, Jan; Andriessen, Paul; Beunk, Frank; Strasser-King, Victor; Fode, Daniel

    2010-05-01

    Sierra Leone lies within the south-western part of the West African Craton and comprises two major Archaean structural divisions: a low-grade granite-greenstone terrane characterised by N-S striking structures and a NW-SE striking highly metamorphosed belt of strained rocks that form the coastal margin of the craton. Intruded into the belt is the Freetown Layered Igneous Complex (FLIC), a tholeiitic magamtic body emplaced prior to or during the break-up of Pangea to form the Central Atlantic Ocean and, forming today the high ground of the coastal outline of Sierra Leone which is one of the most distinctive features on the West African coast. The break-up of Pangaea to form the Central Atlantic and its passive margins began in the Early Jurassic. Geo-tectonically, the break-up was particularly characterised by the formation of the Central Atlantic Magmatic Province (CAMP), covering once-contiguous parts of North America, Europe, Africa and South America. The FLIC forming part of the heart of CAMP is the largest single layered igneous intrusive yet known on either side of the Central Atlantic, measuring on surface, 65 x 14 x 7 km. Geophysical investigations indicate that the intrusion extends offshore to a depth of about 20 km. Geologically the Complex is a rhythmically layered elongated ultramafic-mafic lopolith divisible into 4 major zones each comprising repeated sequences of troctolitic, gabbroic and anorthositic rocks. An idealised unit of layering is from base upwards: dunite, troctolite, olivine-gabbro, leuco-gabbro, gabbro-norite and anorthosite cumulates. 40Ar-39Ar age spectra and 40Ar/36Ar versus 39Ar/36Ar isochron plots obtained by stepwise-heating experiments on plagioclases, biotites and amphiboles from troctolites, olivine-gabbros, gabbro-norites and anorthosites of the four zones yield plateau and isochron ages that seem to depict the cooling history of the Complex after emplacement. The biotites and some of the plagioclases and amphiboles give very

  16. Early Dementia Screening.

    PubMed

    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

  17. Early knee osteoarthritis

    PubMed Central

    Favero, Marta; Ramonda, Roberta; Goldring, Mary B; Goldring, Steven R; Punzi, Leonardo

    2015-01-01

    Concepts regarding osteoarthritis, the most common joint disease, have dramatically changed in the past decade thanks to the development of new imaging techniques and the widespread use of arthroscopy that permits direct visualisation of intra-articular tissues and structure. MRI and ultrasound allow the early detection of pre-radiographic structural changes not only in the peri-articular bone but also in the cartilage, menisci, synovial membrane, ligaments and fat pad. The significance of MRI findings such as cartilage defects, bone marrow lesions, synovial inflammation/effusions and meniscal tears in patients without radiographic signs of osteoarthritis is not fully understood. Nevertheless, early joint tissue changes are associated with symptoms and, in some cases, with progression of disease. In this short review, we discuss the emerging concept of early osteoarthritis localised to the knee based on recently updated knowledge. We highlight the need for a new definition of early osteoarthritis that will permit the identification of patients at high risk of osteoarthritis progression and to initiate early treatment interventions. PMID:26557380

  18. 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

  19. 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

  20. 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

  1. Early object rule acquisition.

    PubMed

    Pierce, D E

    1991-05-01

    The purpose of this study was to generate a grounded theory of early object rule acquisition. The grounded theory approach and computer coding were used to analyze videotaped samples of an infant's and a toddler's independent object play, which produced the categories descriptive of three primary types of object rules; rules of object properties, rules of object action, and rules of object affect. This occupational science theory offers potential for understanding the role of objects in human occupations, for development of instruments, and for applications in occupational therapy early intervention. PMID:2048625

  2. Early College Entrance in Australia

    ERIC Educational Resources Information Center

    Jung, Jae Yup; Young, Marie; Gross, Miraca U. M.

    2015-01-01

    Early college entry is an educational intervention that is being increasingly used in Australia. Following a review of the current Australian literature on early college entry, an overview is provided of the characteristics of, and the procedures associated with, one formal Australian early college entry program (the Early Admission for…

  3. Cognitive Development in Early Readers.

    ERIC Educational Resources Information Center

    Briggs, Chari; Elkind, David

    Some studies of early readers are discussed. It is pointed out that study of early readers has relevance for practical and theoretical issues in psychology and education. Of interest in this document are the following questions: (1) Are there any special talents or traits distinguishing early from non-early readers? (2) Do children who read early…

  4. 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.…

  5. 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…

  6. Women in Early Geology.

    ERIC Educational Resources Information Center

    Elder, Eleanor S.

    1982-01-01

    Biographical sketches are given for several women who made early contributions to the science of geology. A short biography of Inge Lehmann is also included as a more recent example of a woman who has made a notable contribution to the geological field. (Author)

  7. 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…

  8. Early Adolescent Helper Program.

    ERIC Educational Resources Information Center

    Harrington, Diane, Ed.

    1986-01-01

    Recognizing the need for more active learning experiences and appropriate after-school activities for 11- to 14-year-olds, the Early Adolescent Helper Program has designed and tested a model program. Seminars and internships prepare students for placement, which is frequently in child-care or senior centers. (JMM)

  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. PMID:26601261

  10. 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…

  11. 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,…

  12. Early Childhood Development.

    ERIC Educational Resources Information Center

    Koh, Edgar, Ed.

    1989-01-01

    Focused on early childhood development, this "UNICEF Intercom" asserts that developmental programs should aim to give children a fair chance at growth beyond survival. First presented are moral, scientific, social equity, economic, population, and programatic arguments for looking beyond the fundamental objective of saving young lives.…

  13. 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,…

  14. Space Station - early concept

    NASA Technical Reports Server (NTRS)

    1966-01-01

    'Langley's Otto Trout suggested as early as 1963 that zero-gravity activities could be simulated by immersing astronauts in a large tank of water. Years later, Marshall Space Flight Center turned Trout's abortive idea into a major component of NASA's astronaut training program.' Published in James R. Hansen, Spaceflight Revolution: NASA Langley Research Center From Sputnik to Apollo, (Washington: NASA, 1995), p. 303.

  15. 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…

  16. 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…

  17. 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)

  18. 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)

  19. Early Childhood Education 193.

    ERIC Educational Resources Information Center

    Polis, Gloria Owens

    This module adapts the content of an on-campus early childhood education program to a competency-based set of self-paced learning activities for use in largely self-directed, supervised instruction of student child caretakers employed at such settings as a day care center or Head Start agency. Addressed in the individual sections of the module are…

  20. 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); "Testimony of AFC, 12/9/94, before…

  1. Early Developments, 2001.

    ERIC Educational Resources Information Center

    Buysee, Virginia, Ed.; Winton, Pam, Ed.

    2001-01-01

    This document consists of the single 2001 issue of a journal reporting new research in early childhood development conducted by the Frank Porter Graham Child Development Center at the University of North Carolina at Chapel Hill. The issue focuses on pre-kindergarten programs, highlighting a recent assessment of the skills of entering…

  2. 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…

  3. Understanding Early Years Policy

    ERIC Educational Resources Information Center

    Baldock, Peter; Fitzgerald, Damien; Kay, Janet

    2005-01-01

    The book is about policy in the area of early years services and that phrase may need some clarification. For the most part, therefore, this book deals with nursery schools and classes and with services provided by full day care nurseries, pre-schools, creches, childminders, after-school clubs and holiday play schemes. This book begins with…

  4. Illinois Early Learning Standards.

    ERIC Educational Resources Information Center

    2002

    The Illinois Early Learning Standards were developed by the Illinois State Board of Education with the assistance of hundreds of educators. The goal of the standards is to provide teachers and caregivers useful information that is directly needed as part of their daily classroom work. Based on comments from educators, parents, and various experts…

  5. 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

  6. 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…

  7. 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

  8. Investigating the early Earth faint young Sun problem with a general circulation model

    NASA Astrophysics Data System (ADS)

    Kunze, M.; Godolt, M.; Langematz, U.; Grenfell, J. L.; Hamann-Reinus, A.; Rauer, H.

    2014-08-01

    The faint young Sun problem, i.e. the contradiction of a reduced solar luminosity by 15-25% during the Archaean and the geological evidence for relatively high surface temperatures that allowed the presence of liquid water, is still mostly open. It is suggested that the cooling induced by a fainter Sun was e.g. offset by higher levels of greenhouse gases (GHGs) during the Archaean, but achieving the amounts of carbon dioxide (CO2) that are necessary to solve the problem can not be supported by proxy data and the estimates of other additional GHGs diverge. In our study we investigate this problem by using the climate model EMAC with a spectrally resolved irradiance dataset valid for the Archaean epoch of the Earth. Our experimental setup contains a series of model runs which allow the investigation of the role of the continents, the ozone and oxygen content of the atmosphere, the solar luminosity, and the CO2 concentration on the climate of the Archaean. Replacing the present day continents with a global ocean lead to a warming at the surface by ~3 K and an intensified hydrological cycle. The generation of planetary waves and their propagation to the middle atmosphere is reduced, which intensifies the polar night jet and decelerates the Brewer-Dobson circulation. Slightly lower global annual mean temperatures can be found for an anoxic atmosphere. The absent ozone heating in the middle atmosphere leads to very low temperatures in the middle atmosphere and a vanishing polar night jet, whereas the subtropical jets and the Hadley circulation are intensified. The reduction of the solar luminosity to 82% of the present value leads to a globally ice-covered planet and very dry conditions. Prescribing 10 times the present atmospheric level of CO2 with the same solar luminosity leads to a broad belt of liquid surface water throughout the year, although the global annual mean temperature is below the freezing point of water. On reducing the solar luminosity to 77% of the

  9. 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.

  10. Improving Early Seizure Detection

    PubMed Central

    Jouny, Christophe C.; Franaszczuk, Piotr J.; Bergey, Gregory K.

    2011-01-01

    Over the last decade, the search for a method able to reliably predict seizures hours in advance has been largely replaced by a more realistic goal of very early detection of seizure onset which would allow therapeutic or warning devices to be triggered prior to the onset of disabling clinical symptoms. We explore in this article the steps along the pathway from data acquisition to closed loop applications that can and should be considered to design the most efficient early seizure detection. Microelectrodes, high-frequency oscillations, high sampling rate, high-density arrays, and modern analysis techniques are all elements of the recording and detection process that in combination with modeling studies can provide new insights into the dynamics of seizure onsets. Each of these step needs to be considered if one wants to implement improved detection devices that will favorably impact the quality of life of patients. PMID:22078518

  11. Early Years Policy

    PubMed Central

    Waldfogel, Jane; Washbrook, Elizabeth

    2011-01-01

    In this paper, we analyze the role that early years policy might play in narrowing educational attainment gaps. We begin by examining gaps in school readiness between low-, middle-, and high-income children, drawing on data from new large and nationally representative birth cohort studies in the US and UK. We find that sizable income-related gaps in school readiness are present in both countries before children enter school and then decompose these gaps to identify the factors that account for the poorer scores of low-income children. We then consider what role early years policy could play in tackling these gaps, drawing on the best available evidence to identify promising programs. PMID:21731827

  12. Early Childhood Caries

    PubMed Central

    Kawashita, Yumiko; Kitamura, Masayasu; Saito, Toshiyuki

    2011-01-01

    Dental caries is one of the most common childhood diseases, and people continue to be susceptible to it throughout their lives. Although dental caries can be arrested and potentially even reversed in its early stages, it is often not self-limiting and progresses without proper care until the tooth is destroyed. Early childhood caries (ECC) is often complicated by inappropriate feeding practices and heavy infection with mutans streptococci. Such children should be targeted with a professional preventive program that includes oral hygiene instructions for mothers or caregivers, along with fluoride and diet counseling. However, these strategies alone are not sufficient to prevent dental caries in high-risk children; prevention of ECC also requires addressing the socioeconomic factors that face many families in which ECC is endemic. The aim of this paper is to systematically review information about ECC and to describe why many children are suffering from dental caries. PMID:22007218

  13. 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

  14. PHOBOS, the Early Years

    NASA Astrophysics Data System (ADS)

    Stephans, George S. F.; Back, B. B.; Baker, M. D.; Barton, D. S.; Betts, R. R.; Ballintijn, M.; Bickley, A. A.; Bindel, R.; Budzanowski, A.; Busza, W.; Carroll, A.; Decowski, M. P.; Garcia, E.; George, N.; Gulbrandsen, K.; Gushue, S.; Halliwell, C.; Hamblen, J.; Heintzelman, G. A.; Henderson, C.; Hofman, D. J.; Hollis, R. S.; Holynski, R.; Holzman, B.; Iordanova, A.; Johnson, E.; Kane, J. L.; Katzy, J.; Khan, N.; Kucewicz, W.; Kulinich, P.; Kuo, C. M.; Lin, W. T.; Manly, S.; McLeod, D.; Michalowski, J.; Mignerey, A. C.; Nouicer, R.; Olszewski, A.; Pak, R.; Park, I. C.; Pernegger, H.; Reed, C.; Remsberg, L. P.; Reuter, M.; Roland, C.; Roland, G.; Rosenberg, L.; Sagerer, J.; Sarin, P.; Sawicki, P.; Skulski, W.; Steadman, S. G.; Steinberg, P.; Stephans, G. S. F.; Stodulski, M.; Sukhanov, A.; Tang, J.-L.; Teng, R.; Trzupek, A.; Vale, C.; van Nieuwenhuizen, G. J.; Verdier, R.; Wadsworth, B.; Wolfs, F. L. H.; Wosiek, B.; Wozniak, K.; Wuosmaa, A. H.; Wyslouch, B.

    2002-06-01

    The PHOBOS detector, one of the two small experiments at RHIC, focuses on measurements of charged particle multiplicity over almost the full phase space and identified particles near mid-rapidity. Results will be presented from the early RHIC gold--gold runs at nucleon--nucleon center of mass energies of 56 and 130 GeV as well as the recently concluded run at the full RHIC energy of 200 GeV.

  15. 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

  16. Infusing Early Childhood Mental Health into Early Intervention Services

    ERIC Educational Resources Information Center

    Grabert, John C.

    2009-01-01

    This article describes the process of enhancing early childhood mental health awareness and skills in non-mental health staff. The author describes a pilot training model, conducted the U.S. Army's Early Intervention Services, that involved: (a) increasing early childhood mental health knowledge through reflective readings, (b) enhancing…

  17. 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.

  18. Early Intervention: A Global Perspective.

    ERIC Educational Resources Information Center

    Blackman, James A.

    2002-01-01

    The recognition of the importance of brain development in the early years of life has led to expanded early intervention programs for very young children with or at risk for developmental disabilities. A biological basis for early intervention is explored, and brain plasticity is discussed. (Contains references.) (Author/CR)

  19. 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…

  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. Resources for Early Childhood Educators.

    ERIC Educational Resources Information Center

    Ianello, Katherine, Comp.

    The items in this extensive compilation of resources for early childhood educators are presented in seven sections: (1) sources of information on early childhood education, (2) a collection of various materials produced by the ERIC Clearinghouse on Elementary and Early Childhood Education, (3) information on associations and organizations, (4)…

  2. The Perils of Early Motherhood.

    ERIC Educational Resources Information Center

    Sawhill, Isabel V.

    2002-01-01

    Suggests that preventing early childbearing among those who are still young and unmarried is likely to yield significant social benefits, including the restoration of marriage, discussing whether marriage is the solution to the problem of early motherhood. Explains the need for strong efforts to prevent early childbearing, examining teen pregnancy…

  3. 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…

  4. Expenditures for Early Intervention Services

    ERIC Educational Resources Information Center

    Hebbeler, Kathleen; Levin, Jesse; Perez, Maria; Lam, Irene; Chambers, Jay G.

    2009-01-01

    What does it cost to provide early intervention services? Data collected as part of the National Early Intervention Longitudinal Study were used to determine expenditures for infants, toddlers, and their families receiving services through Part C programs. The study found that the national average total expenditure for early intervention services…

  5. 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 resources…

  6. Early Reading and Concrete Operations.

    ERIC Educational Resources Information Center

    Polk, Cindy L. Howes; Goldstein, David

    1980-01-01

    Indicated that early readers are more likely to be advanced in cognitive development than are nonearly-reading peers. After one year of formal reading instruction, early readers maintained their advantage in reading achievement. Measures of concrete operations were found to predict reading achievement for early and nonearly readers. (Author/DB)

  7. Early history of ISNA

    NASA Astrophysics Data System (ADS)

    Hamilton, Mark F.; Muir, Thomas G.; Blackstock, David T.

    2012-09-01

    The International Symposia on Nonlinear Acoustics, now referred to as ISNA, have convened regularly since 1968, bringing together scientists and engineers to report and discuss the latest developments in this branch of nonlinear physics. The fact that this series of symposia is still going strong after more than four decades is testimony that nonlinear acoustics has established itself as a distinct, important, and vibrant field of research. In this paper we take a look back at the early years of ISNA to recall how it all began and trace the evolution of the symposia into their current form.

  8. Early Diagnosis and Staging.

    PubMed

    Lilja, H; Lilja, D R H

    1999-01-01

    This report reviews developments in the early diagnosis and staging of prostate cancer and updated on the incidence of postate cancer to discuss the pros and cons of population based screening. Refinements and reliability of various diagnosic procedures are described such as PSA testing, transrectal ultrasound, ratio beteen PSA-level and ultrasound measured prostate volume, rate of change of PSA-level, combination factor equations computed by neural network programs to predict likelihood of prostate cancer, artificial neural network analysis of subvisual transrectal ultrasound information, measurements of different PSA-forms of PSA (in particular percent free PSA), and glandular kallikrein 2. PMID:12496851

  9. 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

  10. 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. PMID:26601167

  11. Early Earth differentiation

    NASA Astrophysics Data System (ADS)

    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

  12. 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.

  13. Early genital naming.

    PubMed

    Fraley, M C; Nelson, E C; Wolf, A W; Lozoff, B

    1991-10-01

    To evaluate the clinical impression that young girls are given little or confusing information about their genitals, a sample of 117 mothers with 1- to 4-year-old children were asked which words for genitals, if any, they used with their children. The ethnically and socioeconomically heterogeneous sample was composed of 63 girls and 54 boys, with the average ages of 26 and 29 months, respectively. Neither boys nor girls were likely to be given a standard anatomical genital term, although many children received colorful colloquial expressions. However, girls were less likely than boys to receive a term for their genitals. Receiving names for genitals was related to certain family circumstances, such as higher parental education, exposure to adult male nudity, having a sibling of the opposite sex, and cosleeping. Pediatric health professionals have the opportunity to contribute to early sex education by conveying accurate information regarding genital terms in the course of routine physical examinations. PMID:1939685

  14. Early hominid biogeography

    PubMed Central

    Strait, David S.; Wood, Bernard A.

    1999-01-01

    We examined the biogeographic patterns implied by early hominid phylogenies and compared them to the known dispersal patterns of Plio-Pleistocene African mammals. All recent published phylogenies require between four and seven hominid dispersal events between southern Africa, eastern Africa, and the Malawi Rift, a greater number of dispersals than has previously been supposed. Most hominid species dispersed at the same time and in the same direction as other African mammals. However, depending on the ages of critical hominid specimens, many phylogenies identify at least one hominid species that dispersed in the direction opposite that of contemporaneous mammals. This suggests that those hominids may have possessed adaptations that allowed them to depart from continental patterns of mammalian dispersal. PMID:10430919

  15. 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

  16. 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

  17. Early Diabetic Nephropathy

    PubMed Central

    Bjornstad, Petter; Snell-Bergeon, Janet K.; Rewers, Marian; Jalal, Diana; Chonchol, Michel B.; Johnson, Richard J.; Maahs, David M.

    2013-01-01

    OBJECTIVE Diabetic nephropathy (DN) is a major cause of mortality in type 1 diabetes. Reduced insulin sensitivity is a well-documented component of type 1 diabetes. We hypothesized that baseline insulin sensitivity would predict development of DN over 6 years. RESEARCH DESIGN AND METHODS We assessed the relationship between insulin sensitivity at baseline and development of early phenotypes of DN—microalbuminuria (albumin-creatinine ratio [ACR] ≥30 mg/g) and rapid renal function decline (glomerular filtration rate [GFR] loss >3 mL/min/1.73 m2 per year)—with three Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations over 6 years. Subjects with diabetes (n = 449) and without diabetes (n = 565) in the Coronary Artery Calcification in Type 1 Diabetes study had an estimated insulin sensitivity index (ISI) at baseline and 6-year follow-up. RESULTS The ISI was lower in subjects with diabetes than in those without diabetes (P < 0.0001). A higher ISI at baseline predicted a lower odds of developing an ACR ≥30 mg/g (odds ratio 0.65 [95% CI 0.49–0.85], P = 0.003) univariately and after adjusting for HbA1c (0.69 [0.51–0.93], P = 0.01). A higher ISI at baseline conferred protection from a rapid decline of GFR as assessed by CKD-EPI cystatin C (0.77 [0.64–0.92], P = 0.004) and remained significant after adjusting for HbA1c and age (0.80 [0.67–0.97], P = 0.02). We found no relation between ISI and rapid GFR decline estimated by CKD-EPI creatinine (P = 0.38) or CKD-EPI combined cystatin C and creatinine (P = 0.50). CONCLUSIONS Over 6 years, a higher ISI independently predicts a lower odds of developing microalbuminuria and rapid GFR decline as estimated with cystatin C, suggesting a relationship between insulin sensitivity and early phenotypes of DN. PMID:24026551

  18. 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

  19. 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…

  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; Jimmy O. Ong; Sarah J. Patel; George Potoczniak; Adela G. Sanchez; Charles H. Schrader; Lalit S. Shah; Phil J. Shires; Rae Song

    2001-02-15

    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 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/or other carbonaceous 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.

  1. 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.

  2. 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.

  3. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Lalit S. Shah; William K. Davis

    2000-05-01

    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 or coal in combination with some 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 Test Plan (RD and T) for implementation in Phase II. The objective of Phase II is to conduct 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.

  4. 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

  5. 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. PMID:23039334

  6. 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.

  7. 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.

  8. Early Entrance Coproduction Plant

    SciTech Connect

    Mushtaq Ahmed; John H. Anderson; Earl R. Berry; Troy Raybold; Lalit S. Shah; Kenneth A. Yackly

    2004-01-26

    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. 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 work performed under Phase II 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.

  9. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Mushtaq Ahmed; John H. Anderson; Earl R. Berry; Troy Raybold; Lalit S. Shah; Kenneth A. Yackly

    2003-12-16

    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. 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 work performed under Phase II 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.

  10. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

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

    2003-09-09

    The overall objective of this project is the three phase development of an Early Entrance Coproduction Plant (EECP) which uses petroleum coke to 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.

  11. 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. PMID:16914874

  12. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Mushtaq Ahmed; John H. Anderson; Earl R. Berry; Fred Brent; Ming He; Jimmy O. Ong; Mike K. Porter; Randy Roberts; Charles H. Schrader; Lalit S. Shah; Kenneth A. Yackly

    2002-11-22

    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 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 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.

  13. 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.

  14. 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.

  15. Early tetrapod relationships revisited.

    PubMed

    Ruta, Marcello; Coates, Michael I; Quicke, Donald L J

    2003-05-01

    In an attempt to investigate differences between the most widely discussed hypotheses of early tetrapod relationships, we assembled a new data matrix including 90 taxa coded for 319 cranial and postcranial characters. We have incorporated, where possible, original observations of numerous taxa spread throughout the major tetrapod clades. A stem-based (total-group) definition of Tetrapoda is preferred over apomorphy- and node-based (crown-group) definitions. This definition is operational, since it is based on a formal character analysis. A PAUP* search using a recently implemented version of the parsimony ratchet method yields 64 shortest trees. Differences between these trees concern: (1) the internal relationships of aïstopods, the three selected species of which form a trichotomy; (2) the internal relationships of embolomeres, with Archeria crassidisca and Pholiderpeton scut collapsed in a trichotomy with a clade formed by Anthracosaurus russelli and Pholiderpeton attheyi; (3) the internal relationships of derived dissorophoids, with four amphibamid species forming an unresolved node with a clade consisting of micromelerpetontids and branchiosaurids and a clade consisting of albanerpetontids plus basal crown-group lissamphibians; (4) the position of albenerpetontids and Eocaecilia micropoda, which form an unresolved node with a trichotomy subtending Karaurus sharovi, Valdotriton gracilis and Triadobatrachus massinoti; (5) the branching pattern of derived diplocaulid nectrideans, with Batrachiderpeton reticulatum and Diceratosaurus brevirostris collapsed in a trichotomy with a clade formed by Diplocaulus magnicornis and Diploceraspis burkei. The results of the original parsimony run--as well as those retrieved from several other treatments of the data set (e.g. exclusion of postcranial and lower jaw data; character reweighting; reverse weighting)--indicate a deep split of early tetrapods between lissamphibian- and amniote-related taxa. Colosteids, Crassigyrinus

  16. Early aftershock statistics

    NASA Astrophysics Data System (ADS)

    Narteau, C.; Shebalin, P.; Holschneider, M.; Schorlemmer, D.

    2009-04-01

    In the Limited Power Law model (LPL) we consider that after a triggering event - the so-called mainshock - rocks subject to sufficiently large differential stress can fail spontaneously by static fatigue. Then, earlier aftershocks occur in zones of highest stress and the c-value, i.e. the delay before the onset of the power-law aftershock decay rate, depends on the amplitude of the stress perturbation in the aftershock zone. If we assume that this stress perturbation is proportional to the absolute level of stress in the area, the model also predicts that shorter delay occur in zones of higher stress. Here, we present two analyses that support such a prediction. In these analyses, we use only aftershocks of 2.5 < M < 4.5 earthquakes to avoid well-known artifacts resulting from overlapping records. First, we analyze the c-value across different types of faulting in southern California to compare with the differential shear stress predicted by a Mohr-Coulomb failure criterion. As expected, we find that the c-value is on average shorter for thrust earthquakes (high stress) than for normal ones (low stress), taking intermediate values for strike-slip earthquakes (intermediate stress). Second, we test the hypothesis that large earthquakes occur in zones where the level of stress is abnormally high. Instead of the c-value we use the < t >-value, the geometric average of early aftershock times. One more time, we observed that M > 5 earthquakes occur where and when the < t >-value is small. This effect is even stronger for M > 6 earthquakes.

  17. 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. PMID:14648816

  18. 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.

  19. Nebraska Early Childhood Policy Study

    ERIC Educational Resources Information Center

    Nebraska Department of Education, 2005

    2005-01-01

    At the request of the State Board of Education, the Nebraska Department of Education (NDE) conducted an early childhood education policy study. The study provided an opportunity to listen to the thoughts, ideas and concerns of Nebraskans to help determine the direction of early childhood policy in the state. The policy study is an outgrowth of…

  20. 75 FR 20830 - Early Learning

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-21

    ...The U.S. Department of Education (ED), in collaboration with the U.S. Department of Health and Human Services (HHS) and through public meetings and written submissions, is seeking input from State agencies responsible for early learning and development, families (including families with children birth through third grade), educators (including early intervention service providers and other......

  1. 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…

  2. 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…

  3. 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…

  4. Epidemiology in Early Childhood Education.

    ERIC Educational Resources Information Center

    Gratz, Rene R.

    1994-01-01

    Describes the importance of early childhood education as a source of information about health and safety of young children. Discusses the significance of early childhood programs adopting an epidemiological approach to document this information. Outlines a five-step plan to conduct an epidemiological study, using examples from epidemiological…

  5. 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…

  6. Phonological Processing and Early Literacy.

    ERIC Educational Resources Information Center

    Passenger, Terri; Stuart, Morag; Terrell, Colin

    2000-01-01

    Investigates the relationship between phonological awareness and phonological memory and their relative contribution to early reading and spelling. Suggests they make significant yet distinctive contributions to early literacy. Notes evidence that a qualitative change in phonological memory takes place during the first year of formal schooling.…

  7. Early Literacy Assessments & Teaching Strategies.

    ERIC Educational Resources Information Center

    Johns, Jerry L.; Lenski, Susan Davis; Elish-Piper, Laurie

    The purpose of this book is to assist teachers as they work with emergent readers and writers--children who are in the early stages of reading and writing development, typically in preschool through grade 2. Section 1 of the book presents an overview of emergent literacy. Section 2 consists of a group of 15 informal early literacy pretests. The…

  8. Unlocking the Future: Early Literacy.

    ERIC Educational Resources Information Center

    Blair, Leslie Asher, Ed.

    1999-01-01

    This newsletter of the Southwest Educational Development Laboratory (SEDL)contains a collection of articles which discuss various aspects of early literacy. Articles in the newsletter are: "Introduction: Reading Instruction, a Key to the Future"; "Ensuring Early Literacy through Coherent Instruction" (Leslie Blair); "Reading across the Region"…

  9. 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.…

  10. Teaching Mathematics in Early Childhood

    ERIC Educational Resources Information Center

    Moomaw, Sally

    2011-01-01

    Children who learn math fundamentals in preschool and kindergarten have the best chance of later achievement in school--but too often, children don't get the effective early math instruction that makes all the difference. Now there's a core early childhood textbook that helps current and future educators teach the most critical math concepts to…

  11. Early Learning Environments That Work.

    ERIC Educational Resources Information Center

    Isbell, Rebecca; Exelby, Betty

    Noting that the early care and education environment is a vital contribution to children's learning, this book examines the early childhood learning environment with the vision of making it a place where young children will be physically, emotionally, esthetically, and intellectually nurtured. The chapters are: (1) "The Power of the Environment…

  12. Nebraska: Early Head Start Initiative

    ERIC Educational Resources Information Center

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

    2012-01-01

    Since 1999, Nebraska's Early Head Start Infant/Toddler Quality Initiative has supported Early Head Start (EHS) and community child care partnerships to improve the quality and professionalism of infant and toddler care. EHS programs apply to receive funding to establish partnerships with center-based or home-based child care.The initiative has…

  13. 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. PMID:27000393

  14. 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

  15. 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.

  16. 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

  17. 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

  18. 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

  19. Early hominin limb proportions.

    PubMed

    Richmond, Brian G; Aiello, Leslie C; Wood, Bernard A

    2002-10-01

    Recent analyses and new fossil discoveries suggest that the evolution of hominin limb length proportions is complex, with evolutionary reversals and a decoupling of proportions within and between limbs. This study takes into account intraspecific variation to test whether or not the limb proportions of four early hominin associated skeletons (AL 288-1, OH 62, BOU-VP-12/1, and KNM-WT 15000) can be considered to be significantly different from one another. Exact randomization methods were used to compare the differences between pairs of fossil skeletons to the differences observed between all possible pairs of individuals within large samples of Gorilla gorilla, Pan troglodytes, Pongo pygmaeus, and Homo sapiens. Although the difference in humerofemoral proportions between OH 62 and AL 288-1 does not exceed variation in the extant samples, it is rare. When humerofemoral midshaft circumferences are compared, the difference between OH 62 and AL 288-1 is fairly common in extant species. This, in combination with error associated with the limb lengths estimates, suggests that it may be premature to consider H. (or Australopithecus) habilis as having more apelike limb proportions than those in A. afarensis. The humerofemoral index of BOU-VP-12/1 differs significantly from both OH 62 and AL 288-1, but not from KNM-WT 15000. Published length estimates, if correct, suggest that the relative forearm length of BOU-VP-12/1 is unique among hominins, exceeding those of the African apes and resembling the proportions in Pongo. Evidence that A. afarensis exhibited a less apelike upper:lower limb design than A. africanus (and possibly H. habilis) suggests that, if A. afarensis is broadly ancestral to A. africanus, the latter did not simply inherit primitive morphology associated with arboreality, but is derived in this regard. The fact that the limb proportions of OH 62 (and possibly KNM-ER 3735) are no more human like than those of AL 288-1 underscores the primitive body design of H

  20. 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…

  1. From Early Intervention to Early Childhood Programs: Timeline for Early Successful Transitions (TEST)

    ERIC Educational Resources Information Center

    Brandes, Joyce A.; Ormsbee, Christine K.; Haring, Kathryn A.

    2007-01-01

    More than one million transitions between early intervention services and early childhood programs are facilitated annually for youngsters with special needs. To be successful, these transitions require planning and ongoing communication between all parties. This article substantiates the need for a timeline/checklist and provides a model of…

  2. Liquid Water on Early Mars

    NASA Technical Reports Server (NTRS)

    Davis, Wanda L.; McKay, Christopher P.

    1994-01-01

    We have used a simple climate model to determine the duration of liquid water habitats on early Mars following up on the previous work of McKay and Davis. We used the weathering model of Pollack et al. to compute the pressure and temperature evolution of the atmosphere. We included the variability of the solar luminosity. Recent results which have considered the influence of CO2 condensation suggest that Mars could not have been kept warm (above 0 C) with only a dense CO2 atmosphere. New stellar evolution theories have suggested a more massive early sun to explain the lithium depletion in the sun and predict a warmer climate for early Mars. We have therefore modified the model of McKay and Davis to include the effects of CO2 condensation and the effect of a more massive early sun. Here we present the results of these additional effects on the duration of liquid water habitats on early Mars. We find that the increased luminosity suggested for the early sun when mass loss is taken into account can provide a climate on early Mars that results in fluvial features existing over 500 million years.

  3. Early recognition of growth abnormalities permitting early intervention

    PubMed Central

    Haymond, Morey; Kappelgaard, Anne-Marie; Czernichow, Paul; Biller, Beverly MK; Takano, Koji; Kiess, Wieland

    2013-01-01

    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. Conclusion This review summarizes currently available information on monitoring for short stature in children and conditions usually associated with short stature and summarizes the authors’ conclusions on the early recognition of growth disorders. PMID:23586744

  4. Early Walking of Geriatric Amputees

    PubMed Central

    Devas, M. B.

    1971-01-01

    After amputation geriatric patients have been enabled to get up and walk with the help of a prosthesis, an “early walking aid.” The physiotherapist measures the patient, fits the early walking aid, and instructs him in walking. The prosthesis is simple to make, easy to apply, and allows early walking with the use of a walking frame or sticks. Thus the geriatric amputee can walk as soon after operation as his general condition allows and the surgeon wishes. ImagesFIG. 1FIG. 2 PMID:5100378

  5. Morphogenesis of early stage melanoma

    NASA Astrophysics Data System (ADS)

    Chatelain, Clément; Amar, Martine Ben

    2015-08-01

    Melanoma early detection is possible by simple skin examination and can insure a high survival probability when successful. However it requires efficient methods for identifying malignant lesions from common moles. This paper provides an overview first of the biological and physical mechanisms controlling melanoma early evolution, and then of the clinical tools available today for detecting melanoma in vivo at an early stage. It highlights the lack of diagnosis methods rationally linking macroscopic observables to the microscopic properties of the tissue, which define the malignancy of the tumor. The possible inputs of multiscale models for improving these methods are shortly discussed.

  6. 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.

  7. Mars and the early Sun

    NASA Astrophysics Data System (ADS)

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

    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.

  8. 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. PMID:23550705

  9. 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

  10. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    John Anderson; Mark Anselmo; Earl Berry; Mark Bohn; Roko Bujas; Ming He; Ken Kwik; Charles H. Schrader; Lalit Shah; Dennis Slater; Donald Todd; Don Wall

    2003-08-21

    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 (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. Each of the EECP subsystems were assessed for technical risks and barriers. A plan was identified to mitigate the identified risks (Phase II RD&T Plan, October 2000). The RD&T Plan identified catalyst/wax separation as a potential technical and economic risk. To mitigate risks to the proposed EECP, Phase II RD&T included tests of an alternative (to Rentech's Dynamic Settler) primary catalyst/wax separation device and

  11. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    John Anderson; Mark Anselmo; Earl Berry; Mark Bohn; Ming He; Charles H. Schrader; Lalit Shah; Donald Todd; Robert Schavey

    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 its detailed design, construction, and operation. The partners in this project are Texaco Energy Systems LLC (TES) (a subsidiary of ChevronTexaco), General Electric (GE), Praxair, and Kellogg Brown & Root (KBR). The work was under cooperative agreements with the U.S. Department of Energy (DOE). TES is providing the gasification technology and the Fischer-Tropsch (F-T) technology developed by Rentech Inc., GE is providing the combustion turbine technology, Praxair is providing the air separation technology, and KBR is providing overall engineering. Each of the EECP's subsystems was assessed for technical risks and barriers in Phase I. A plan was identified to mitigate the identified risks (Phase II RD&T Plan, October 2000). The RD&T Plan identified catalyst/wax separation as a potential technical and economic risk. To mitigate risks to the proposed EECP concept, Phase II RD&T included tests for

  12. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Abdalla H. Ali; Raj Kamarthi; John H. Anderson; Earl R. Berry; Charles H. Schrader; Lalit S. Shah

    2003-04-16

    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 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 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 the integration of the water produced in the F-T synthesis section with the gasification section as an area of potential synergy. By utilizing the F-T water in the petroleum coke slurry for the gasifier, the EECP can eliminate a potential waste stream and reduce capital costs. There is a low technical risk for this synergy, however, the economic risk, particularly in regards to the water, can be high. The economic costs include the costs

  13. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Randy Roberts

    2003-04-25

    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 using petroleum coke and ChevronTexaco's proprietary gasification technology. 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. 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. (a subsidiary of ChevronTexaco), General Electric (GE), Praxair, and Kellogg Brown & Root (KBR) in addition to the U.S. Department of Energy (DOE). ChevronTexaco is providing gasification technology and Fischer-Tropsch 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 were assessed for technical risks and barriers. A plan was identified to mitigate the identified risks (Phase II RD&T Plan, October 2000). The RD&T Plan identified F-T reactor scale-up as a potential technical risk. The objective of Task 2.3 was to confirm engineering models that allow scale-up to commercial slurry phase bubble column (SPBC) reactors operating in the churn-turbulent flow regime. In

  14. 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

  15. Depression at an Early Age.

    ERIC Educational Resources Information Center

    Alper, Joseph

    1986-01-01

    Addresses the crisis associated with adolescent affective disorders and probes potential genetics, environmental, and physiological factors. Reviews case examples of depression, eating disorders, and suicide among youths. States clinical implications and advocates early diagnosis and treatment. (ML)

  16. Can Rhabdomyosarcoma Be Found Early?

    MedlinePlus

    ... prevented? Next Topic Signs and symptoms of rhabdomyosarcoma Can rhabdomyosarcoma be found early? At this time, there ... or other parts of the urinary tract and can cause trouble emptying the bladder or blood in ...

  17. Early Childhood: 3-D Potpourri.

    ERIC Educational Resources Information Center

    Petty, Carolyn A.

    1988-01-01

    Describes some art activities for early childhood that also teach about science. Expresses concern that young children operating in a three-dimensional world are often expected to translate their world onto a flat sheet of paper. (TW)

  18. 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)

  19. Microcomputers in Early Childhood Education?

    ERIC Educational Resources Information Center

    Ziajka, Alan

    1983-01-01

    Introduces the basic terminology and capabilities of computers, describes software for children, provides guidelines for choosing hardware, briefly characterizes computer languages, and discusses the use of computers in early childhood education. (RH)

  20. 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 ...

  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 isotropization of the Glasma

    NASA Astrophysics Data System (ADS)

    Epelbaum, T.

    2014-11-01

    A first principle treatment of the early stages of a heavy ion collision within the Color Glass Condensate framework seems to indicate an early hydrodynamization of the initially out of equilibrium Quark Gluon Plasma. Contrasting with the leading order CGC result, the improved calculation presented here provides evidence for a fast isotropization of the pressure tensor, as well as an anomalously small shear viscosity over entropy ratio.

  3. 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

  4. 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

  5. EARLY ENTRANCE COPRODUCTION PLANT

    SciTech Connect

    Abdalla H. Ali; John H. Anderson; Earl R. Berry; Charles H. Schrader; Lalit S. Shah

    2003-04-16

    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 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 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 were assessed for technical risks and barriers. A plan was identified to mitigate the identified risks (Phase II RD&T Plan, October 2000). The RD&T Plan identified petroleum coke characteristics as a potential technical risk. The composition of petroleum coke varies from one refinery to another. Petroleum coke characteristics are a function of the crude oil slate available at the refinery and the coker operating parameters. The specific

  6. Early childhood survivorship in Vietnam.

    PubMed

    Swenson, I E; Thang, N M; San, P B; Nhan, V Q; Man, V D

    1995-06-01

    The effects on early childhood mortality of birth order, age of the mother at the time of the child's birth, mother's education, as well as infant mortality risk in the province, urban/rural residence, the presence of schools and other facilities and health care services, were examined using data from the 1988 Vietnam Demographic and Health Survey and the 1990 Study of Accessibility of Contraceptives in Vietnam. A total of 4137 urban and rural children born between 1983 and 1988 to the 4172 women interviewed in the Demographic and Health Survey were included in the hazard model analysis of maternal and child characteristics. However, since the Accessibility of Contraceptives Study included only rural respondents, the hazard model analysis of community development characteristics and health services effects on early childhood mortality was based on a subsample of 3314 rural children. Rural children in birth orders five and higher had the greatest risk of early childhood death, birth order one an intermediate risk and orders 2-4 the lowest risk of early childhood death. Rural children residing in communes with fewer than 10,000 inhabitants were at significantly greater risk of early childhood death than children from larger communes. Neither age nor education of the mother nor gender of the child, had a significant impact on early childhood survivorship independent of other variables. Risk of infant mortality in the child's province was of borderline significance. PMID:7783281

  7. 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

  8. 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…

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

    ERIC Educational Resources Information Center

    Southern Regional Education Board (SREB), 2014

    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…

  10. Early Childhood Educators' Knowledge of Early Literacy Development

    ERIC Educational Resources Information Center

    Crim, Courtney; Hawkins, Jacqueline; Thornton, Jenifer; Rosof, Holly Boon; Copley, Juanita; Thomas, Emily

    2008-01-01

    The foundation of all learning is rooted in the development of language and literacy abilities. Literacy development begins well before children enter school and can accelerate in an early childhood classroom setting. Teacher educators often hear about the importance of literacy development. In particular, the significance of phonological…

  11. 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...

  12. Early exit: Estimating and explaining early exit from drug treatment

    PubMed Central

    Stevens, Alex; Radcliffe, Polly; Sanders, Melony; Hunt, Neil

    2008-01-01

    Background Early exit (drop-out) from drug treatment can mean that drug users do not derive the full benefits that treatment potentially offers. Additionally, it may mean that scarce treatment resources are used inefficiently. Understanding the factors that lead to early exit from treatment should enable services to operate more effectively and better reduce drug related harm. To date, few studies have focused on drop-out during the initial, engagement phase of treatment. This paper describes a mixed method study of early exit from English drug treatment services. Methods Quantitative data (n = 2,624) was derived from three English drug action team areas; two metropolitan and one provincial. Hierarchical linear modelling (HLM) was used to investigate predictors of early-exit while controlling for differences between agencies. Qualitative interviews were conducted with 53 ex-clients and 16 members of staff from 10 agencies in these areas to explore their perspectives on early exit, its determinants and, how services could be improved. Results Almost a quarter of the quantitative sample (24.5%) dropped out between assessment and 30 days in treatment. Predictors of early exit were: being younger; being homeless; and not being a current injector. Age and injection status were both consistently associated with exit between assessment and treatment entry. Those who were not in substitution treatment were significantly more likely to leave treatment at this stage. There were substantial variations between agencies, which point to the importance of system factors. Qualitative analysis identified several potential ways to improve services. Perceived problems included: opening hours; the service setting; under-utilisation of motivational enhancement techniques; lack of clarity about expectations; lengthy, repetitive assessment procedures; constrained treatment choices; low initial dosing of opioid substitution treatment; and the routine requirement of supervised consumption

  13. Early Planetary Differentiation: Comparative Planetology

    NASA Technical Reports Server (NTRS)

    Jones, John H.

    2006-01-01

    We currently have extensive data for four different terrestrial bodies of the inner solar system: Earth, the Moon, Mars, and the Eucrite Parent Body [EPB]. All formed early cores; but all(?) have mantles with elevated concentrations of highly sidero-phile elements, suggestive of the addition of a late "veneer". Two appear to have undergone extensive differentiation consistent with a global magma ocean. One appears to be inconsistent with a simple model of "low-pressure" chondritic differentiation. Thus, there seems to be no single, simple paradigm for understand-ing early differentiation.

  14. 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.

  15. 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…

  16. 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…

  17. 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…

  18. 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…

  19. 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…

  20. 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)

  1. 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…

  2. 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…

  3. 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…

  4. 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.

  5. 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…

  6. 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…

  7. Early Decision and College Performance

    ERIC Educational Resources Information Center

    Jensen, Elizabeth J.; Wu, Stephen

    2010-01-01

    This paper examines the relationship between admission status and college performance. In particular, we analyze admissions data from Hamilton College and find that students who applied through the Early Decision Plan II program have significantly lower GPAs and are less likely to receive departmental honors, fellowships, and outside scholarships…

  8. 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…

  9. Kansas: Early Head Start Initiative

    ERIC Educational Resources Information Center

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

    2012-01-01

    Kansas Early Head Start (KEHS) provides comprehensive services following federal Head Start Program Performance Standards for pregnant women and eligible families with children from birth to age 4. KEHS was implemented in 1998 using Child Care and Development Block Grant (CCDBG) quality set-aside dollars augmented by a transfer of federal…

  10. 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…

  11. Warming early Earth and Mars

    SciTech Connect

    Kasting, J.F.

    1997-05-23

    Sagan and Chyba, in their article on page 1217 of this issue, have revived an old debate about how liquid water was maintained on early Earth and Mars despite a solar luminosity 25 to 30% lower than that at present. A theory that has been popular for some time is that greatly elevated concentrations of atmospheric COD produced by the action of the carbonate-silicate cycle, provided enough of a greenhouse effect to warm early Earth. However, Rye et al. have placed geochemical constraints on early atmospheric CO{sub 2} abundances that fall well below the levels needed to warm the surface. These constraints are based on the absence of siderite (FeCO{sub 3}) in ancient soil profiles-a negative and, hence, rather weak form of evidence- and apply to the time period 2.2 to 2.8 billion years ago, when Earth was already middle aged. Nonetheless, the soil data provide some indication that atmospheric CO{sub 2} levels may have been lower than previously thought. An even more serious problem arises if one tries to keep early Mars warm with CO{sub 2}. Model calculations predict that CO{sub 2} clouds would form on Mars in the upper troposphere, reducing the lapse rate and severely limiting the amount of surface warming. A suggestion that CO{sub 2} clouds may have warmed the planet radiatively has yet to be borne out by detailed calculations. 26 refs.

  12. Early Childhood Education. IDRA Focus.

    ERIC Educational Resources Information Center

    IDRA Newsletter, 1996

    1996-01-01

    This newsletter includes five articles on early childhood education and young children, with particular reference to poor and minority children. "Scientific Literacy Is Child's Play" (Hilaria Bauer) discusses the natural development of scientific literacy in young children through their construction of knowledge and play. "Children of America,…

  13. 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…

  14. Assessment in Early Childhood Education.

    ERIC Educational Resources Information Center

    Blenkin, Geva M., Ed.; Kelly, A. V., Ed.

    Contributions to this collection explore the relationship between education and assessment in the context of the British National Curriculum and mandated nationally standardized assessment procedures. The chapters are: (1) "Concepts of Assessment: An Overview" (Vic Kelly); (2) "Progression, Observation and Assessment in Early Education: The…

  15. 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…

  16. 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…

  17. Family Interaction in Early Adolescence.

    ERIC Educational Resources Information Center

    Steinberg, Laurence D.; Hill, John P.

    The verbal interaction of 31 middle class early adolescent boys and their parents was analyzed in order to provide information concerning adolescent autonomy. The boys were independently and reliably classified on the basis of age, physical maturity, and intellectual level. The taped interactions were coded for interruptions, talking times,…

  18. 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…

  19. Maryland Early Head Start Initiative

    ERIC Educational Resources Information Center

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

    2012-01-01

    Since 2000, Maryland has provided state supplemental funds to Head Start and Early Head Start (EHS) programs to improve access. Local EHS programs may use funds, through child care partnerships, to extend the EHS day or year. Maryland's approach to building on EHS includes: (1) Increase the capacity of existing Head Start and EHS programs to…

  20. 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…

  1. Research on Early Science Education.

    ERIC Educational Resources Information Center

    Landry, Christopher E.; Forman, George E.

    The implementation of basic research on children's scientific thinking into science curricula continues to be a slow process. This chapter summarizes research on cognitive development that has helped to establish the goals for much of early science education and examines its implications. The chapter begins by describing scientific thinking and…

  2. 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.…

  3. 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…

  4. 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…

  5. Dance Education in Early Childhood.

    ERIC Educational Resources Information Center

    Stinson, Susan W.

    1990-01-01

    Recommends creative dance, as part of early childhood education, be developmentally appropriate, using exploratory movement and sensory awareness to teach children about themselves. From personal experience, describes dance work, based on Native-American dance and children's alternative realities, and designed to encourage future development of…

  6. Early Reading with Deaf Children.

    ERIC Educational Resources Information Center

    Soderbergh, Ragnhild

    1985-01-01

    Early reading for deaf and hearing-impaired children using the natural reading method inspired by Doman is advocated. The Doman method is described. What educational research on deaf and hearing-impaired children says concerning the process of reading acquisition is discussed. (RM)

  7. 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…

  8. Early Childhood Education in Scandinavia.

    ERIC Educational Resources Information Center

    Austin, Gilbert R.; Dittman, Laura

    This article discusses the move toward greater equality of educational opportunity in Scandinavia with particular emphasis on early childhood education. The increasing demand for preschool education in Denmark, Finland, Norway and Sweden is related to low birth rates together with increased employment of women and the general demand for equality…

  9. 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…

  10. 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.

  11. An Introduction to "Early College"

    ERIC Educational Resources Information Center

    Brewer, Dominic J.; Stern, Stefanie; Ahn, June

    2007-01-01

    Several national and international assessments have demonstrated that there has been little improvement in the performance of American high school students in recent decades. High school students are increasingly underprepared for transition into college-level course-work. One new approach to high school redesign, "early college," seeks to address…

  12. Choctaw Culture Early Education Activities.

    ERIC Educational Resources Information Center

    Brescia, William, Ed.; Reeves, Carolyn, Ed.; Skinner, Linda, Ed.

    An effort to better prepare Choctaw youngsters for kindergarten, the Choctaw Culture Early Education Program developed a resource of 58 activities adapted to meet the needs of Choctaw 3- and 4-year olds. The activities are divided into four sections pertaining to getting started, relating to five project publications (How the Flowers Came to Be,…

  13. The Early Study Abroad Trend

    ERIC Educational Resources Information Center

    Ly, Phuong

    2008-01-01

    A growing number of South Korean students are going to an English-speaking country as teenagers to escape from the grueling, test-oriented Korean schools in hopes of gaining entry into American universities. American colleges and universities are starting to see more of these "early study abroad students," as they are called in South Korea. This…

  14. 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…

  15. Early Childhood Education at Home.

    ERIC Educational Resources Information Center

    Richards, Mary JoAnn

    Outlined is a Title III early childhood at home project which involves a team approach to the education of 40 handicapped and 75 nonhandicapped rural, disadvantaged children, their parents, and/or babysitters in West Virginia. It is noted that four teams consisting of a teacher and paraprofessionals visit homes to instruct baby sitters or parents…

  16. Early Lessons in Restructuring Schools.

    ERIC Educational Resources Information Center

    Lieberman, Ann; And Others

    Restructuring schools has become a rallying cry among educators. It aims to create schools that are more centered on learner's needs for active, experiential, cooperative, and culturally connected learning opportunities supportive of individual talents and learning styles. This report is based on an early evaluation of the process of restructuring…

  17. 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…

  18. [Early career of Michael Sendivogius].

    PubMed

    Prinke, Rafał T

    2012-01-01

    One of the most influential alchemical authors of the early modern period was Michael Sendivogius whose early life is shrouded in mystery. He may be labelled the most famous Polish scientific writer between Copernicus and Marie Skłodowska-Curie, but because of the difficulties involved in researching the biography of any alchemist, there has been relatively little interest in him among Polish historians. The early work of Roman Bugaj (author of the still fundamental monograph) and Włodzimierz Hubicki (who made his research available to the international community) has been continued only by the English-born Zbigniew Szydło and the author of this article. The roots of many legends about Sendivogius were three mid-17th century short biographies, none of which is trustworthy, so it is crucial to verify the received myth and the version constructed in the 1960's and 1970's with primary sources and evidence from the recent "new historiography of alchemy". The present article examines them in the light of newly discovered sources and reinterpretation of the old ones. The genealogy of the Sedzimir family is discussed at length to show that Sendivogius most probably was not its member but only a pretender in order to assume (or prove) the status of a nobleman. Several possible hypotheses about his origins are presented. He is known to have studied at three universities (Leipzig, Vienna and Altdorf) but authors of early panegyrics dedicated to Sendivogius list more universities which he may have attended. The most interesting is that of Cambridge, listed as the first one, because practically no Poles or Czechs went there at the time. Finally, his marriage to Veronica Stiebar, a wealthy widow of a Franconian knightly family, and her interesting family relationships (links to Erasmus, Camerarius, Paracelsus and the original Doctor Faustus) are discussed. The period covered is that before Sendivogius moved to Prague in about 1597, having already been a courtier of Rudolf II

  19. Early lunar geology and geophysics

    NASA Astrophysics Data System (ADS)

    Garrick-Bethell, Ian

    2009-06-01

    Despite a number of human and robotic missions to the Moon, there are still important unanswered questions about its early evolution, and how it came to be the object we observe today. Here we use observational, experimental, and theoretical techniques to examine three important events that took place early in lunar history and have left a lasting signature. The first event is the formation of the largest basin on the Moon, the South Pole-Aitken Basin. We develop a systematic method to define the previously unknown boundaries of this degraded structure and quantify its gross shape. We also combine a number of remote sensing data sets to constrain the origin of heat producing elements in its interior. The second event we examine is the evolution of the lunar orbit, and the coupling between the Moon's early geophysical properties and the growth of orbital eccentricity. We use analytical models for tidal deformations and orbit evolution to show that the shape of the Moon suggests its early orbit was highly eccentric. However, we are also able to explain the presently high eccentricity entirely by traditional, secular tidal growth while the early Moon was hot. The third event we examine is the magnetization of lunar samples. We perform extensive paleomagnetic measurements of an ancient, deep-seated lunar sample, and determine that a long-lived magnetic field like that of a core dynamo is the most plausible explanation for its magnetic remanence. In sum, the earliest portion of lunar history has been largely obscured by later geologic events, but a great deal can still be learned from this formative epoch. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  20. Early Axonal Area Measurement Predicts Early Nerve Regeneration Outcomes.

    PubMed

    Neilson, Michael; Yan, Yuhui; Zhang, Lin-Ling; Wang, Ziyi; Agresti, Michael; Matloub, Hani; Yan, Ji-Gheng

    2016-03-01

    Background Study of peripheral nerve injury and regeneration in laboratory animals can be time consuming and expensive. This study determines if it is possible to reduce time and cost for a peripheral nerve regeneration study. Purpose The purpose of this study was to determine if nerve axonal area (NXA) or nerve fiber counting (NFC) correlates with compound muscle action potential (CMAP) recovery which is known to predict functional muscular recovery in the early stage of nerve regeneration. Methods In this study, six rats had a crush injury of the sciatic nerve without treatment. These rats were evaluated at 4 weeks of recovery with the following assessments: CMAP readings from the extensor digitorum longus, NXA measurement, and NFC. Results NXA correlated with CMAP; NFC did not correlate with CMAP. Conclusion NFC is not a reliable method for predicting muscular recovery in the early stages. NXA is a dependable assessment for muscular recovery in the early stages of nerve regeneration. Using NXA measurement can predict later electrophysiological and functional recovery. Using NXA with CMAP measurement for nerve injury, repair, and treatment in the animal study can save cost and time. PMID:26636887

  1. Abnormal Early Cleavage Events Predict Early Embryo Demise: Sperm Oxidative Stress and Early Abnormal Cleavage

    PubMed Central

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

    2014-01-01

    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. PMID:25307782

  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. 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…

  4. Thrombophilia and early pregnancy loss.

    PubMed

    McNamee, Kelly; Dawood, Feroza; Farquharson, Roy G

    2012-02-01

    Early pregnancy loss is the most common pregnancy complication. About 15% of pregnancies result in pregnancy loss and 1% of women experience recurrent miscarriage (more than three consecutive miscarriages). The influence of thrombophilia in pregnancy is a popular research topic in recurrent miscarriage. Both acquired and inherited thrombophilia are associated with a risk of pregnancy failure. Antiphospholipid syndrome is the only thrombophilia known to have a direct adverse effect on pregnancy. Historically, clinical research studying thrombophilia treatment in recurrent miscarriage has been of limited value owing to small participant numbers, poor study design and heterogeneity. The debate on the efficacy of aspirin and heparin has advanced with recently published randomised-controlled trials. Multi-centre collaboration is required to ascertain the effect of thrombophilia on early pregnancy loss and to establish an evidence-based treatment protocol. PMID:22079389

  5. Early Proterozoic geology of Arizona

    NASA Astrophysics Data System (ADS)

    Conway, Clay M.; Karlstrom, Karl E.

    The Early Proterozoic geology of Arizona and adjoining regions was the topic of a workshop convened by Clay M. Conway (U.S. Geological Survey (USGS), Flagstaff, Ariz.), Karl E. Karlstrom (Northern Arizona University (NAU), Flagstaff), and Leon T. Silver (California Institute of Technology (Caltech), Pasadena) in Flagstaff, October 3-5, 1985. The meeting, sponsored by USGS, NAU, Caltech, and the Arizona Geological Survey, was attended by 73 geologists from industry, academia, and governmental agencies. The workshop brought together for the first time workers in a variety of disciplines who have been studying facets of Early Proterozoic crustal evolution in the southwest. From responses during and following the workshop, we judge that the meeting successfully accomplished its objective of furthering communication, cooperation, and collaboration. The meeting encouraged contributions, including progress reports, from all participants and concentrated on specific problems of stratigraphy, structure, petrology, geochemistry, and ore formation, with a view toward understanding overall orogenic evolution and continental accretion.

  6. The diets of early hominins.

    PubMed

    Ungar, Peter S; Sponheimer, Matt

    2011-10-14

    Diet changes are considered key events in human evolution. Most studies of early hominin diets focused on tooth size, shape, and craniomandibular morphology, as well as stone tools and butchered animal bones. However, in recent years, dental microwear and stable isotope analyses have hinted at unexpected diversity and complexity in early hominin diets. Some traditional ideas have held; others, such as an increasing reliance on hard-object feeding and a dichotomy between Australopithecus and Paranthropus, have been challenged. The first known evidence of C(4) plant (tropical grasses and sedges) and hard-object (e.g., seeds and nuts) consumption dates to millions of years after the appearance of the earliest probable hominins, and there are no consistent trends in diet change among these species through time. PMID:21998380

  7. 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

  8. Health lifestyles in early childhood.

    PubMed

    Mollborn, Stefanie; James-Hawkins, Laurie; Lawrence, Elizabeth; Fomby, Paula

    2014-12-01

    This study integrates two important developments, the concept of health lifestyles (which has focused on adults and adolescents) and the increased attention to early childhood. We introduce the concept of children's health lifestyles, identifying differences from adult health lifestyles and articulating intergenerational transmission and socialization processes shaping children's health lifestyles. Using the nationally representative Early Childhood Longitudinal Study-Birth Cohort (2001-2007; N ≈ 6,150), latent class analyses identify predominant health lifestyles among U.S. preschoolers. Five distinct empirical patterns representing health lifestyles emerge, two capturing low and medium levels of overall risk across domains and three capturing domain-specific risks. Social background predicts children's health lifestyles, but lower household resources often explain these relationships. Across kindergarten measures of cognition, behavior, and health, preschool health lifestyles predict children's development even after controlling for social disadvantage and concurrent household resources. Further research on health lifestyles throughout childhood is warranted. PMID:25413801

  9. Early stages of Ostwald ripening

    NASA Astrophysics Data System (ADS)

    Shneidman, Vitaly A.

    2013-07-01

    The Becker-Döring (BD) nucleation equation is known to predict a narrow double-exponential front (DEF) in the distribution of growing particles over sizes, which is due to early transient effects. When mass conservation is included, nucleation is eventually exhausted while independent growth is replaced by ripening. Despite the enormous difference in the associated time scales, and the resulting demand on numerics, within the generalized BD model the early DEF is shown to be crucial for the selection of the unique self-similar Lifshitz-Slyozov-Wagner asymptotic regime. Being preserved till the latest stages of growth, the DEF provides a universal part of the initial conditions for the ripening problem, regardless of the mass exchange mechanism between the nucleus and the matrix.

  10. 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

  11. Nanotechnology for Early Cancer Detection

    PubMed Central

    Choi, Young-Eun; Kwak, Ju-Won; Park, Joon Won

    2010-01-01

    Vast numbers of studies and developments in the nanotechnology area have been conducted and many nanomaterials have been utilized to detect cancers at early stages. Nanomaterials have unique physical, optical and electrical properties that have proven to be very useful in sensing. Quantum dots, gold nanoparticles, magnetic nanoparticles, carbon nanotubes, gold nanowires and many other materials have been developed over the years, alongside the discovery of a wide range of biomarkers to lower the detection limit of cancer biomarkers. Proteins, antibody fragments, DNA fragments, and RNA fragments are the base of cancer biomarkers and have been used as targets in cancer detection and monitoring. It is highly anticipated that in the near future, we might be able to detect cancer at a very early stage, providing a much higher chance of treatment. PMID:22315549

  12. Early Literacy Instruction and Intervention

    PubMed Central

    Al Otaiba, Stephanie; Foorman, Barbara

    2014-01-01

    The purpose of this paper is to describe the efficacy of early literacy interventions and to discuss possible roles for volunteer tutors in helping prevent reading difficulties within the Response to Intervention process. First, we describe a landmark study that evaluated the impact of primary classroom instruction on reducing the proportion of students at risk for reading failure, and a more recent series of studies exploring the effects of individualizing classroom reading instruction based on students’ initial skills. Second, we review studies of more intensive early intervention to demonstrate how these interventions substantially reduce the proportion of students at risk. Third, we examine effective tutoring models that utilize volunteers. Finally, we discuss the potential role of community tutors in supporting primary classroom instruction and secondary interventions. PMID:25221452

  13. 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

  14. Nanotechnology for early cancer detection.

    PubMed

    Choi, Young-Eun; Kwak, Ju-Won; Park, Joon Won

    2010-01-01

    Vast numbers of studies and developments in the nanotechnology area have been conducted and many nanomaterials have been utilized to detect cancers at early stages. Nanomaterials have unique physical, optical and electrical properties that have proven to be very useful in sensing. Quantum dots, gold nanoparticles, magnetic nanoparticles, carbon nanotubes, gold nanowires and many other materials have been developed over the years, alongside the discovery of a wide range of biomarkers to lower the detection limit of cancer biomarkers. Proteins, antibody fragments, DNA fragments, and RNA fragments are the base of cancer biomarkers and have been used as targets in cancer detection and monitoring. It is highly anticipated that in the near future, we might be able to detect cancer at a very early stage, providing a much higher chance of treatment. PMID:22315549

  15. Early stage of nanocrystal growth

    SciTech Connect

    2012-01-01

    Berkeley Lab researchers at the Molecular Foundry have elucidated important mechanisms behind oriented attachment, the phenomenon that drives biomineralization and the growth of nanocrystals. This electron microscopy movie shows the early stage of nanocrystal growth. Nanoparticles make transient contact at many points and orientations until their lattices are perfectly matched. The particles then make a sudden jump-to-contact to form attached aggregates. (Movie courtesy of Jim DeYoreo)

  16. 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…

  17. Ontogeny of Early Life Immunity

    PubMed Central

    Dowling, David J.; Levy, Ofer

    2014-01-01

    The human immune system is comprised of cellular and molecular components designed to coordinately prevent infection while avoiding potentially harmful inflammation and auto-immunity. Immunity varies with age, reflecting unique age-dependent challenges including fetal gestation, the neonatal phase and infancy. Herein, we review novel mechanistic insights into early life immunity, with emphasis on emerging models of human immune ontogeny, which may inform age-specific translational development of novel anti-infectives, immunomodulators and vaccines. PMID:24880460

  18. [Early Development under Microgravity Conditions].

    PubMed

    Ogneva, I V

    2015-01-01

    The review is devoted to various aspects of early development under the space flight conditions. The different possible cell mechanosensors are considered. Structural and functional changes in the cells, predominantly, in non-muscle ones, were discussed. The results of the different experiments with the embryos of fish, amphibians, birds and mammals under microgravity conditions are shown discussing possible reasons for the development of morphological changes. PMID:26591615

  19. 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. PMID:18849281

  20. 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.

  1. Early diagnosis of Parkinson's disease.

    PubMed

    Becker, Georg; Müller, Antje; Braune, Stefan; Büttner, Thomas; Benecke, Reiner; Greulich, Wolfgang; Klein, Wolfgang; Mark, Günter; Rieke, Jürgen; Thümler, Reiner

    2002-10-01

    In idiopathic Parkinson's disease (IPD) approximately 60 % of the nigrostriatal neurons of the substantia nigra (SN) are degenerated before neurologists can establish the diagnosis according to the widely accepted clinical diagnostic criteria. It is conceivable that neuroprotective therapy starting at such an 'advanced stage' of the disease will fail to stop the degenerative process. Therefore, the identification of patients at risk and at earlier stages of the disease appears to be essential for any successful neuroprotection. The discovery of several genetic mutations associated with IPD raises the possibility that these, or other biomarkers, of the disease may help to identify persons at risk of IPD. Transcranial ultrasound have shown susceptibility factors for IPD related to an increased iron load of the substantia nigra. In the early clinical phase, a number of motor and particularly non-motor signs emerge, which can be identified by the patients and physicians years before the diagnosis is made, notably olfactory dysfunction, depression, or 'soft' motor signs such as changes in handwriting, speech or reduced ambulatory arm motion. These signs of the early, prediagnostic phase of IPD can be detected by inexpensive and easy-to-administer tests. As one single instrument will not be sensitive enough, a battery of tests has to be composed measuring independent parameters of the incipient disease. Subjects with abnormal findings in this test battery should than be submitted to nuclear medicine examinations to quantify the extent of dopaminergic injury and to reach the goal of a reliable, early diagnosis. PMID:12522572

  2. 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. PMID:9007229

  3. 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.

  4. 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

  5. Prevention of early childhood caries.

    PubMed

    Ismail, A I

    1998-01-01

    This paper reviews the methods used for the prevention of early childhood caries (ECC). The education of mothers or caregivers to promote healthy dietary habits in infants has been the main strategy used for the prevention of ECC. This review found that education has a modest impact on the development of ECC. While education should be promoted especially in high risk communities and population groups (low-income families and native populations), it should not be the only preventive strategy of ECC. Early screening for signs of caries development, starting from the first year of life, could identify infants and toddlers who are at risk of developing ECC and assist in providing information to parents about how to promote oral health and prevent the development of tooth decay. High risk children include those with early signs of ECC, poor oral hygiene, limited exposure to fluorides, and frequent exposure to sugary snacks and drinks. These children should be targeted with a professional preventive program that includes fluoride varnish application, fluoridated dentifrices, fluoride supplements, sealants, diet counseling, and chlorhexidine. Prevention of ECC also requires addressing the social and economic factors that face many families where ECC is endemic. PMID:9671200

  6. 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.

  7. [Autochthonous recollection in early schizophrenia].

    PubMed

    Seki, Yukako

    2003-01-01

    Autochthonous recollection in early schizophrenia is a subordinate symptom of autochthonous experiences, one of the four major symptoms specific to early schizophrenia as described by Nakayasu. Autochthonous recollection is detected most frequently in early schizophrenia. I am under the impression that the contents of autochthonous recollection tend to be unpleasant according to the patients' complaints. At the medical reformatory where I worked I experienced a case in which the autochthonous recollection of unpleasant contents seemed to form new symptoms in the patient, which elevated impulsivity and caused misconduct. Since then, I have performed symptomatic examinations of autochthonous recollection through cross-sectional and longitudinal methods upon 87 cases of early schizophrenia. In the cross-sectional aspect, past experiences of recollection consisted of 5 categories: , , , and . The number of categories of autochthonous recollection per patient was one category in 61 cases (70.1%), two in 20 cases (23.0%), three in 4 cases (4.6%), four in 1 case (1.2%), and five in 1 case (1.2%). The prevalence of recollections ranked by categories showed in 58 cases (66.7%), in 11 cases (12.6%), in 5 cases (5.7%), in 6 cases (6.9%), and in 42 cases (48.3%). Examination of the longitudinal aspect of symptomformation with autochthonous recollection revealed that in 19 cases new symptoms were formed and most were based on recollection of unpleasant experiences. They are: 1. elevated aggression towards him/herself and others, neurotic manifestation 2. silly smile, monologue 3. autochthonous fantasy images 4. rarefaction of sense of personal possession 5. ideas of reference 6. delusion of persecution, delusional memory The mechanisms of these symptomformations were

  8. Early gastric stump cancer following distal gastrectomy

    PubMed Central

    Kaneko, K; Kondo, H; Saito, D; Shirao, K; Yamaguchi, H; Yokota, T; Yamao, G; Sano, T; Sasako, M; Yoshida, S

    1998-01-01

    Background—Gastric stump cancer (GSC) is usually diagnosed at an advanced stage, and consequently the prognosis is poor. 
Aims—To investigate the clinicopathological characteristics of GSC at an early stage to assist in its identification, and thereby improve its prognosis. 
Methods—Forty three patients with resected early GSC were compared with 156 patients with resected primary early cancer in the upper third of the stomach. 
Results—Sixty five per cent (28/43) of the early GSC patients showed the elevated type endoscopically, although the frequency of the depressed type in GSC has tended to increase in the past five years. This occurred in less than 26% (40/156) of the primary early cancers. Half of the early GSCs were located on the lesser curvature (47%), and revealed differentiated adenocarcinoma (81%) histologically. The male:female ratio of early GSC cases was about 6:1, which was much higher than that in patients with primary early cancer. The five year survival rates of patients with early GSCs and early primary cancers were 84% and 95%, respectively. GSC had a favourable prognosis, if it was detected at an early stage. 
Conclusion—To detect early GSC, our results suggest that special attention should be given to elevated as well as depressed lesions on the lesser curvature of the stomach, particularly in men, during endoscopic examinations. 

 Keywords: gastric stump cancer; early gastric cancer; prognosis; endoscopy PMID:9863478

  9. Planck early results. VII. The Early Release Compact Source Catalogue

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bucher, M.; Burigana, C.; Butler, R. C.; Cabella, P.; Cantalupo, C. M.; Cappellini, B.; Cardoso, J.-F.; Carvalho, P.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, L.-Y.; Chiang, C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Fosalba, P.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Haissinski, J.; Hansen, F. K.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Huynh, M.; Jaffe, A. H.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leach, S.; Leahy, J. P.; Leonardi, R.; León-Tavares, J.; Leroy, C.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mann, R.; Maris, M.; Marleau, F.; Marshall, D. J.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Melin, J.-B.; Mendes, L.; Mennella, A.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; O'Dwyer, I. J.; Osborne, S.; Pajot, F.; Paladini, R.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Piffaretti, R.; Plaszczynski, S.; Platania, P.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sajina, A.; Sandri, M.; Santos, D.; Savini, G.; Schaefer, B. M.; Scott, D.; Seiffert, M. D.; Shellard, P.; Smoot, G. F.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Sudiwala, R.; Sunyaev, R.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; White, S. D. M.; Wilkinson, A.; Yvon, D.; Zacchei, A.; Zonca, A.

    2011-12-01

    A brief description of the methodology of construction, contents and usage of the Planck Early Release Compact Source Catalogue (ERCSC), including the Early Cold Cores (ECC) and the Early Sunyaev-Zeldovich (ESZ) cluster catalogue is provided. The catalogue is based on data that consist of mapping the entire sky once and 60% of the sky a second time by Planck, thereby comprising the first high sensitivity radio/submillimetre observations of the entire sky. Four source detection algorithms were run as part of the ERCSC pipeline. A Monte-Carlo algorithm based on the injection and extraction of artificial sources into the Planck maps was implemented to select reliable sources among all extracted candidates such that the cumulative reliability of the catalogue is ≥90%. There is no requirement on completeness for the ERCSC. As a result of the Monte-Carlo assessment of reliability of sources from the different techniques, an implementation of the PowellSnakes source extraction technique was used at the five frequencies between 30 and 143GHz while the SExtractor technique was used between 217 and 857GHz. The 10σ photometric flux density limit of the catalogue at |b| > 30° is 0.49, 1.0, 0.67, 0.5, 0.33, 0.28, 0.25, 0.47 and 0.82 Jy at each of the nine frequencies between 30 and 857GHz. Sources which are up to a factor of ~2 fainter than this limit, and which are present in "clean" regions of the Galaxy where the sky background due to emission from the interstellar medium is low, are included in the ERCSC if they meet the high reliability criterion. The Planck ERCSC sources have known associations to stars with dust shells, stellar cores, radio galaxies, blazars, infrared luminous galaxies and Galactic interstellar medium features. A significant fraction of unclassified sources are also present in the catalogs. In addition, two early release catalogs that contain 915 cold molecular cloud core candidates and 189 SZ cluster candidates that have been generated using

  10. Geochemistry and petrogenesis of the late Archaean high-K granites in the southern Musoma-Mara Greenstone Belt: Their influence in evolution of Archaean Tanzania Craton

    NASA Astrophysics Data System (ADS)

    Mshiu, Elisante Elisaimon; Maboko, Makenya A. H.

    2012-05-01

    Musoma-Mara Greenstone Belt (MMGB) is abundantly occupied by the post-orogenic high-K granites which also they mark the end of magmatism in the area. The granites are characterized by high SiO2 and Al2O3 contents that average 74.42% and 13.08% by weight respectively. They have low Na2O content (mean = 3.36 wt.%) and high K2O contents (mean = 4.95 wt.%) which resulted to relatively high K2O/Na2O ratios (mean = 1.50). They also characterized by low Mg# (mean = 33) as well as low contents of transition elements such as Cr and Ni which are below detection limit (<20 ppm). Negative anomalies in Eu (Eu/Eu*, mean = 0.56), Nd, Ta and Ti elements as shown in the chondrite and primitive mantle normalized diagrams indicate MMGB high-K granites originated from a subduction related environments. These high-K granites also characterized by relative enrichment of the LREE compared to HREE as revealed by their high (La/Yb)CN ratio ranging from 8.71 to 50.93 (mean = 26.32). They have relatively flat HREE pattern with (Tb/Yb)CN ratio varying between 0.81 and 2.12 (mean = 1.55). Their linear trend in the variation diagrams of both major and trace elements indicate magmatic differentiation was also an important process during their formation. Conclusively, the geochemical characteristics as well as experimental evidences suggests MMGB high-K granites were formed from partial melting of pre-existing TTG rocks, under low pressure at 15 km depth or less and temperature around 950 °C in which plagioclase minerals were the stable phases in the melt.

  11. 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…

  12. Can Nasopharyngeal Cancer Be Found Early?

    MedlinePlus

    ... Next Topic Signs and symptoms of nasopharyngeal cancer Can nasopharyngeal cancer be found early? In the United ... simple, non-invasive exams or blood tests that can reliably find this cancer early. But in some ...

  13. Early Alzheimer's Linked to Brain 'Leakage'

    MedlinePlus

    ... https://medlineplus.gov/news/fullstory_159116.html Early Alzheimer's Linked to Brain 'Leakage' Normally, blood-brain barrier ... HealthDay News) -- People in the early stages of Alzheimer's disease may have more "leaks" in the barrier ...

  14. Can Ovarian Cancer Be Found Early?

    MedlinePlus

    ... Topic Signs and symptoms of ovarian cancer 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 ...

  15. Deep Brain Stimulation Tested for Early Alzheimer's

    MedlinePlus

    ... https://medlineplus.gov/news/fullstory_160137.html Deep Brain Stimulation Tested for Early Alzheimer's Although treatment seems ... 2016 THURSDAY, July 28, 2016 (HealthDay News) -- Deep brain stimulation appears safe for people with early Alzheimer's ...

  16. Early Detection | Division of Cancer Prevention

    Cancer.gov

    This group supports research that seeks to determine the effectiveness, operating characteristics and clinical impact (harms as well as benefits) of cancer early detection technolog | Research on the effectiveness and clinical impact of early detection technologies and practices.

  17. Early Repolarisation Syndrome – New Concepts

    PubMed Central

    Katritsis, Demosthenes G; Gersh, Bernard J; Camm, A John

    2015-01-01

    New concepts regarding early repolarisation syndrome are presented. Genetics and epidemiology data, as well as new evidence on the potential clinical significance of early repolarisation patterns, are discussed. PMID:26835120

  18. Can Multiple Myeloma Be Found Early?

    MedlinePlus

    ... Topic Signs and symptoms of multiple myeloma Can multiple myeloma be found early? It’s difficult to diagnose multiple myeloma early. Often, multiple myeloma causes no symptoms until it reaches an ...

  19. 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)

  20. Early childhood caries screening tools

    PubMed Central

    Yoon, Richard K.; Smaldone, Arlene M.; Edelstein, Burton L.

    2013-01-01

    Background Early childhood caries (ECC) is prevalent and consequential. Risk assessment tools have been proposed that can be used to identify children who require intensive interventions. In this study, the authors compare four approaches for identifying children needing early and intensive intervention to prevent or minimize caries experience for their accuracy and clinical usefulness. Methods The authors screened 229 predominantly low-income Hispanic children younger than 3 years with ECC and 242 without ECC by using the American Academy of Pediatric Dentistry’s Caries-risk Assessment Tool (CAT) and the optional screening measure of culturing Streptococcus mutans. The authors compared four approaches (CAT, CAT minus socioeconomic status, CAT minus socioeconomic status plus mutans streptococci [MS] and MS alone) for accuracy and clinical usefulness. Results The results of the CAT demonstrated high sensitivity (100.0 percent) and negative predictive value (NPV) (100.0 percent) but low specificity (2.9 percent) and positive predictive value (PPV) (49.4 percent). The MS culture alone had the highest combination of accuracy and clinical usefulness (sensitivity, 86.5 percent; specificity, 93.4 percent; PPV, 92.5 percent; NPV, 87.9 percent). When we removed the socioeconomic status element, the CAT’s performance improved. Conclusions Salivary culture of MS alone in a population of young, low-income Hispanic children outperformed the CAT and variations on the CAT for test accuracy (sensitivity and specificity) and clinical usefulness (predictive values). Clinical Implications Screening for ECC by using salivary MS cultures and variations on the CAT are promising approaches for identifying children who need early and intensive intervention to prevent or minimize caries experience. PMID:22751977

  1. 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…

  2. Early Interventions: Keys to Successful Readers.

    ERIC Educational Resources Information Center

    Jeffreys, JoAnn; Spang, Joan

    This action research outlines an early reading intervention project for improving students' reading skills and promoting the implementation of early reading intervention programs. The targeted population includes first and second grade students in one school located in the suburbs of a major city in Illinois. The problem of early reading…

  3. 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 with the…

  4. Supporting Mathematical Development in the Early Years

    ERIC Educational Resources Information Center

    Pound, Linda

    2006-01-01

    This book provides practical guidance for parents, teachers, and other early years workers who want to give children a good start in mathematical development. Showing how competent children are as mathematicians from an early age, the book offers an overview of young children's mathematical behaviour at home and in early years settings. This book…

  5. 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)…

  6. 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…

  7. Depressive Symptomatology among Very Early Maturing Girls.

    ERIC Educational Resources Information Center

    Rierdan, Jill; Koff, Elissa

    1991-01-01

    The relationship between very early menarche and depression was studied in a sample of 488 girls (336 sixth graders and 152 seventh graders), less than 10 percent of whom were very early maturers. Very early menarche was associated with higher levels of depression than was more normative development. (SLD)

  8. Language, Literacy and Early Childhood Education

    ERIC Educational Resources Information Center

    Fellowes, Janet; Oakley, Grace

    2011-01-01

    "Language, Literacy and Early Childhood Education" is a comprehensive textbook for all students studying literacy and language subjects in early childhood education and primary degrees. Covering an age range from 0 to 8 years the book encompasses the four main early childhood contexts of: the family and community; childcare; the pre-school years,…

  9. Taiwanese Early Childhood Educators' Professional Development

    ERIC Educational Resources Information Center

    Hsu, Ching-Yun

    2008-01-01

    This study was designed based on a qualitative paradigm to explore the professional development of Taiwanese early childhood educators. The method of phenomenology was employed. The main research question addressed was "How do early childhood educators construe their professional development experience?" Seven Taiwanese early childhood educators…

  10. 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…

  11. Management of Early Carcinoma of the Ovary

    PubMed Central

    Chapman, George W.

    1988-01-01

    Ovarian cancer represents a formidable challenge to physicians. Early symptoms are nonspecific, and are usually attributed to disorders of the upper gastrointestinal tract. Especially important is suspicion of this neoplasm in its early stage. This article discusses the epidemiology, clinical features, evaluation, and treatment of early carcinomas of the ovary. PMID:3071612

  12. 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…

  13. Early Care and Education (ECE) Facts

    ERIC Educational Resources Information Center

    Chase, Richard

    2008-01-01

    This paper presents several facts about the early care and education in Minnesota. These facts are organized according to the following topics: (1) Children age 5 and younger in Minnesota; (2) Number of early care and education programs and providers; (3) Children ages 0-2 and 3-5 enrolled in quality early childhood programs; (4) Number of…

  14. Developmental Psychology and Early Childhood Education.

    ERIC Educational Resources Information Center

    Lickona, Thomas

    This report discusses the relationship between the fields of early childhood education and developmental psychology. A historical overview focuses on the early influence of Freud's psychoanalytical principles on early childhood education. Developmental psychologists became involved with ECE on a large scale in the 1960's, encouraged largely by the…

  15. 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…

  16. Early Childhood Education 295. Special Topics.

    ERIC Educational Resources Information Center

    Polis, Gloria Owens

    This module, part of a series of early childhood education instructional materials, is intended to assist teachers in adapting an on-campus early childhood education program for use by students desiring self-paced instruction in early childhood education. The course consists of individualized study of a topic chosen by the student or approved work…

  17. Early Childhood Care and Education in Kenya

    ERIC Educational Resources Information Center

    Mbugua, Tata J.

    2004-01-01

    Recent years have seen a global endeavor to prioritize early childhood care and education as a foundation for later learning and development, as evidenced by the Global Guidelines for Early Childhood Education and Care in the 21st Century (Association for Childhood Education International/World Organization for Early Childhood, 1999). Such efforts…

  18. 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…

  19. Early Childhood Education: A Workbook for Administrators.

    ERIC Educational Resources Information Center

    Hewes, Dorothy; Hartman, Barbara

    Business management theory and principles as applied to the administration of early childhood programs are presented in this workbook. Following a brief survey of the historical background of early childhood education and current early childhood programs, information and guidance to help plan, operate, and evaluate program facilities are provided.…

  20. Early Childhood Teacher Certification: A National Survey.

    ERIC Educational Resources Information Center

    Lamme, Linda Leonard; And Others

    1983-01-01

    A survey of early childhood teacher certification processes in the 50 states found great differences in the interpretation of what age and grade levels constitute early childhood education and in the certification requirements for teachers. Educational trends in this area are discussed, as is the need for training early childhood education…

  1. Project ELI: Improving Early Literacy Outcomes

    ERIC Educational Resources Information Center

    Young, Robin Miller; Chandler, Lynette K.; Shields, LuAnn; Laubenstein, Pam; Butts, Jill; Black, Kristine

    2008-01-01

    Early childhood and elementary-level educators are engaging in conversations about how to coordinate their efforts to develop fluent readers. There is evidence that key early literacy skills that are predictive of subsequent literacy achievement in kindergarten and first grade can be taught to preschool-age children. Moreover, early childhood…

  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. 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…

  4. Strategies for Supporting Early Literacy Development

    ERIC Educational Resources Information Center

    Dennis, Lindsay R.; Horn, Eva

    2011-01-01

    The development of early literacy skills is critical to children's later success in reading and reading-related activities; therefore, understanding how teachers can support early literacy development is equally important. In this article, the authors provide information on how early childhood teachers can use specific strategies and techniques as…

  5. 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 provision. It also looks…

  6. 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…

  7. 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

  8. Selectivity in early prosocial behavior

    PubMed Central

    Kuhlmeier, Valerie A.; Dunfield, Kristen A.; O’Neill, Amy C.

    2014-01-01

    Prosocial behavior requires expenditure of personal resources for the benefit of others, a fact that creates a “problem” when considering the evolution of prosociality. Models that address this problem have been developed, with emphasis typically placed on reciprocity. One model considers the advantages of being selective in terms of one’s allocation of prosocial behavior so as to improve the chance that one will be benefitted in return. In this review paper, we first summarize this “partner choice” model and then focus on prosocial development in the preschool years, where we make the case for selective partner choice in early instances of human prosocial behavior. PMID:25120526

  9. The Environment of Early Mars

    NASA Astrophysics Data System (ADS)

    Matsubara, Yo

    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

  10. An unmagnetized early planetary body

    NASA Astrophysics Data System (ADS)

    Weiss, B. P.; Wang, H.; Downey, B. G.; Shuster, D. L.; Gattacceca, J.; Sharp, T. G.; Fu, R. R.; Kuan, A. T.; Suavet, C. R.; Irving, A. J.

    2014-12-01

    Modern paleomagnetic studies of achondrites have found that at least several planetesimals generated dynamos with inferred surface magnetic fields ranging from tens to hundreds of μT. In fact, an achondrite without evidence for paleomagnetic fields has not been previously identified, hinting that the dynamo process may have been extremely common among early planetary bodies. To further expand our understanding of the diversity of planetesimal dynamos, we have been studying the paleomagnetism the ungrouped achondrite NWA 7325. This ancient meteorite (Pb/Pb and Al/Mg ages of ~4563 Ma) is highly depleted in siderophile elements, indicating that it formed on a differentiated body that underwent large-scale metal-silicate fractionation. We present new paleomagnetic, rock magnetic transmission and scanning electron microscopy, and Ar/Ar analyses of this rock that constrain the field intensity in which it cooled. In particular, we employ a new controlled oxygen fugacity system that enables us to conduct thermal demagnetization while greatly mitigating oxidation-reduction reactions. This system is critical because of the extremely reduced conditions (at least 3 log units below the iron-wüstite buffer) in which this meteorite formed. The extremely fine grain size (<200 nm) of many FeNi metal grains in NWA 7325 (pseudo single domain-superparamagnetic size) means that it has extremely high fidelity magnetic recording properties. We find no stable remanent magnetization and no evidence for any magnetic fields greater than ~2 μT at the time of last cooling below the Curie point. Our Ar/Ar thermochronometry suggests that the last major thermal event experienced by NWA 7325 was at 500 Ma. Because this age is well after the expected lifetime of early planetesimal dynamos, our data indicate that any crustal fields on the parent body are extremely weak. This stands in stark contrast to Vesta, for which our analyses of the eucrite ALHA 81001 suggest has substantial (~10

  11. [Early bioprosthetic mitral valve thrombosis].

    PubMed

    Tkaczyszyn, Michał; Olbrycht, Tomasz; Kustrzycka Kratochwil, Dorota; Sokolski, Mateusz; Sukiennik Kujawa, Małgorzata; Skiba, Jacek; Gemel, Marek; Banasiak, Waldemar; Jankowska, Ewa A; Ponikowski, Piotr

    2012-01-01

    We present a case of a 70 year-old woman operated due to severe mitral regurgitation. Early after surgery transthoracic echocardiography revealed the decreased effective orifice area of the implanted bioprosthetic valve and the stenotic features of transvalvular flow. Transesophageal echocardiography (TEE) disclosed a thrombotic cause of heterograft dysfunction. Due to the clinical deterioration and the unclear cause of prosthesis stenosis, the patient was reoperated. Intra-operatively bioprosthetic mitral valve thrombosis was confirmed. Precipitating factors of this rare complication including cardiac device related infective endocarditis (CDRIE) and the diagnostic applicability of TEE in this clinical scenario are discussed. PMID:22427084

  12. 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.

  13. Early Events of DNA Photodamage

    NASA Astrophysics Data System (ADS)

    Schreier, Wolfgang J.; Gilch, Peter; Zinth, Wolfgang

    2015-04-01

    Ultraviolet (UV) radiation is a leading external hazard to the integrity of DNA. Exposure to UV radiation triggers a cascade of chemical reactions, and many molecular products (photolesions) have been isolated that are potentially dangerous for the cellular system. The early steps that take place after UV absorption by DNA have been studied by ultrafast spectroscopy. The review focuses on the evolution of excited electronic states, the formation of photolesions, and processes suppressing their formation. Emphasis is placed on lesions involving two thymine bases, such as the cyclobutane pyrimidine dimer, the (6-4) lesion, and its Dewar valence isomer.

  14. The evolution of early neurogenesis.

    PubMed

    Hartenstein, Volker; Stollewerk, Angelika

    2015-02-23

    The foundation of the diverse metazoan nervous systems is laid by embryonic patterning mechanisms, involving the generation and movement of neural progenitors and their progeny. Here we divide early neurogenesis into discrete elements, including origin, pattern, proliferation, and movement of neuronal progenitors, which are controlled by conserved gene cassettes. We review these neurogenetic mechanisms in representatives of the different metazoan clades, with the goal to build a conceptual framework in which one can ask specific questions, such as which of these mechanisms potentially formed part of the developmental "toolkit" of the bilaterian ancestor and which evolved later. PMID:25710527

  15. Early and late neonatal septicaemia.

    PubMed Central

    Placzek, M M; Whitelaw, A

    1983-01-01

    Between 1979 and 1982 we reviewed 1000 consecutive admissions to the neonatal intensive care unit of this hospital. Sixty five infants had positive blood cultures. Mortality was 70% among 17 infants who had septicaemia in the first 48 hours of life and for whom appropriate treatment may have been too late because of difficulties of early diagnosis. In the remaining 48 infants mortality was 12%, septicaemia occurred later, and was associated with Staphylococcus epidermidis (56%) and with the presence of an intravascular catheter (50%). PMID:6625634

  16. Sleep and Early Cortical Development

    PubMed Central

    Olini, Nadja; Huber, Reto; LeBourgeois, Monique

    2016-01-01

    Sleep is increasingly recognized as a key process in neurodevelopment. Animal data show that sleep is essential for the maturation of fundamental brain functions, and growing epidemiological findings indicate that children with early sleep disturbance suffer from later cognitive, attentional, and psychosocial problems. Still, major gaps exist in understanding processes underlying links between sleep and neurodevelopment. One challenge is to translate findings from animal research to humans. In this review, we describe parallels and differences in sleep and development of the cortex in humans and animals and discuss emerging questions. PMID:26807347

  17. 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

  18. 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. PMID:26133287

  19. [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. PMID:26580942

  20. Dr. Sadik decries early parenthood.

    PubMed

    1991-01-01

    At the Tenth Anniversary Conference of the Center for Population Options, which was held in Washington on September 24, 1990, Dr. Nafis Sadik, Executive Director of the United Nations Population Fund (UNFPA), spoke concerning the problems created by early parenthood. Childbirth is the greatest health risk young women, after reaching puberty, face in developing countries; their children are less likely to survive than those born to those over 20. Early childbearing means larger families; this, when combined with shorter time spans between generations, leads to rapid population growth and endangers sustainable development in societies with limited natural resources. As a social and economic issue, adolescent fertility limits educational achievement, status, and full participation in the community for women and girls. In many societies, women are second class citizens; they are more likely to die in infancy than boys, they are less likely to attend school, and they leave school earlier. They derive their status from motherhood and spend practically all of their fertile years pregnant and caring for children. They have no other option because their futures are determined by others. PMID:12346165

  1. 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.

  2. Early diagnosis of lung cancer.

    PubMed

    Yasufuku, Kazuhiro

    2010-03-01

    Early detection and surgical resection is essential for the treatment of lung cancer. Although the introduction of low-dose spiral computed tomography (CT) is considered to be one of the most promising clinical research developments, CT screening is used for detecting small peripheral lesions. Tumors arising in the central airways require other techniques for early detection. Centrally arising squamous cell carcinoma of the airway, especially in heavy smokers, is thought to develop through multiple stages from squamous metaplasia to dysplasia, followed by carcinoma in situ (CIS), progressing to invasive cancer. It would be ideal to be able to detect and treat preinvasive bronchial lesions defined as dysplasia and CIS before progressing to invasive cancer. Great efforts have been made to develop new mucosal imaging techniques. Bronchoscopic imaging techniques capable of detecting preinvasive lesions and currently available in clinical practice include autofluorescence bronchoscopy (AFB), high magnification ronchovideoscope, and narrow band imaging (NBI). For a more precise evaluation of newly detected preinvasive lesions, endobronchial ultrasound (EBUS) and optical coherence tomography (OCT) can be used. PMID:20172431

  3. Early detection of pancreatic cancer

    PubMed Central

    Ahuja, Nita

    2015-01-01

    Pancreatic adenocarcinoma is a low-incident but highly mortal disease. It accounts for only 3% of estimated new cancer cases each year but is currently the fourth common cause of cancer mortality. By 2030, it is expected to be the 2nd leading cause of cancer death. There is a clear need to diagnose and classify pancreatic cancer at earlier stages in order to give patients the best chance at a definitive cure through surgery. Three precursor lesions that distinctly lead to pancreatic adenocarcinoma have been identified, and we have increasing understanding the non-genetic and genetic risk factors for the disease. With increased understanding about the risk factors, the familial patters, and associated accumulation of genetic mutations involved in pancreatic cancer, we know that there are mutations that occur early in the development of pancreatic cancer and that improved genetic risk-based strategies in screening for pancreatic cancer may be possible and successful at saving or prolonging lives. The remaining challenge is that current standards for diagnosing pancreatic cancer remain too invasive and too costly for widespread screening for pancreatic cancer. Furthermore, the promises of noninvasive methods of detection such as blood, saliva, and stool remain underdeveloped or lack robust testing. However, significant progress has been made, and we are drawing closer to a strategy for the screening and early detection of pancreatic cancer. PMID:26361402

  4. 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.

  5. Early Contributions To Silicate Magnetism

    NASA Astrophysics Data System (ADS)

    Evans, Ted

    I have been asked to describe the early work concerning the palaeomagnetic signifi- cance of silicates. In his classic papers published half a century ago, Louis Néel put forward an elegant single-domain (SD) theory to explain the strength and enormous stability of remanent magnetization in rocks. The difficulty was that the predicted size for SD behaviour in magnetite was less than the wavelength of light. This led to the application of electron microscopy to this problem, the first images being obtained in 1969. As it happened, these involved tiny inclusions of magnetite in the pyroxene crystals of a Precambrian gabbro. The technique used in these early investigations was a metallurgical one wherein a carbon film replica of the polished and etched surface of the rock sample is prepared. This provides high spatial resolution but not much com- positional information. Furthermore, the experimental procedures involved are suffi- ciently labour-intensive that this type of work never achieved much popularity. Never- theless, Ssilicate inclusionS remanence has been identified in a variety of oceanic and ´ continental igneous rocks involving ShostS crystals of olivine, pyroxene and feldspar. ´ As far as this session is concerned, the so-called Scloudy feldsparsS found in basic ´ dykes are particularly relevant.

  6. 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

  7. 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

  8. 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.

  9. [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. PMID:24077546

  10. 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

  11. EARLY EVOLUTION OF PRESTELLAR CORES

    SciTech Connect

    Horedt, G. P.

    2013-08-20

    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 {gamma} between 0 and 6/5, implying radial power-law density profiles between r {sup -1} and r {sup -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 {approx}> 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 10{sup 5} 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.

  12. Early detection of lung cancer.

    PubMed

    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

  13. 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.

  14. 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

  15. 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. PMID:24696510

  16. Early recognition of chemical dependence.

    PubMed

    Maly, R C

    1993-03-01

    Chemical dependence is a leading cause of morbidity and death in the United States. At least 20% of patients seen by primary care physicians in both the outpatient and inpatient setting are chemically dependent. Up to 90% of these patients go undiagnosed by their primary physicians. Chemical dependence is defined as a chronic, progressive illness characterized by the repeated and persistent use of alcohol or drugs despite negative health, family, work, financial, or legal consequences. Primary care physicians are in an ideal position to detect chemical dependence at its earliest stages, when irreversible medical consequences and death are most likely preventable. Alcohol is the most common drug of abuse. Improving the rate of recognition of chemical dependence depends on being familiar with the constellation of physical, mental, and social indicators. Early medical manifestations of alcoholism common in the primary care setting include: gastric complaints, elevated blood pressure, palpitations, traumatic injuries, headaches, impotence, and gout. Early psychosocial manifestations common in both alcohol and drug dependence include anxiety, depression, insomnia, persistent relationship conflicts, work or school problems, and financial or legal problems. Particularly useful laboratory indicators of alcoholism include elevated levels of GGT and MCV, both displaying high specificity, with the GGT level being the most sensitive. Similarly specific laboratory tests for drug dependence are not available. Any patient presenting with any of the above medical, psychosocial, or laboratory manifestations should be screened for chemical dependence. The CAGE questionnaire for alcoholism, a four-question test, is particularly well suited to the primary care setting, where it can be administered in fewer than 60 seconds. The CAGE has demonstrated high sensitivity (in the 80% range) and specificity (approximately 85%) for alcoholism. Comparably convenient instruments do not yet exist

  17. 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. PMID:24315051

  18. Early literacy and early numeracy: the value of including early literacy skills in the prediction of numeracy development.

    PubMed

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

    2011-12-01

    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 year later on the PENS test and on the Applied Problems and Calculation subtests of the Woodcock-Johnson III Tests of Achievement. Three mixed effect regressions were conducted using Time 2 PENS, Applied Problems, and Calculation as the dependent variables. Print Knowledge and Vocabulary accounted for unique variance in the prediction of Time 2 numeracy scores. Phonological Awareness did not uniquely predict any of the mathematics domains. The findings of this study identify an important link between early literacy and early numeracy development. PMID:21831396

  19. 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. PMID:16469903

  20. Developmental origins of early antisocial behavior.

    PubMed

    Calkins, Susan D; Keane, Susan P

    2009-01-01

    Early antisocial behavior has its origins in childhood behavior problems, particularly those characterized by aggressive and destructive behavior. Deficits in self-regulation across multiple domains of functioning, from the physiological to the cognitive, are associated with early behavior problems, and may place children at greater risk for the development of later antisocial behavior. Data are presented from a longitudinal study of early self-regulation and behavior problems, the RIGHT Track Research Project, demonstrating that children at greatest risk for early and persistent problem behavior display patterns of physiological and emotional regulation deficits early in life. Parenting behavior and functioning have also been examined as predictors of trajectories of early problem behavior, and some data support the interaction of parenting and self-regulation as significant predictors of patterns of problematic behavior and ongoing problems with the regulation of affect. Peer relationships also affect and are affected by early self-regulation skills, and both may play a role in academic performance and subsequent school success. These data provide evidence that the social contexts of early family and peer relationships are important moderators of the more proximal mechanism of self-regulation, and both types of processes, social and biobehavioral, are likely implicated in early antisocial tendencies. Implications of these findings on self-regulation and early behavior problems are discussed in terms of future research and treatment approaches. PMID:19825259