Éditeur(s) : [s.n.]
Résumé : (Funding) Funded in part by the University of Florida, the Florida Heritage Project of the State University Libraries of Florida, the Institute for Museum and Library Services, and the U.S. Department of Education's TICFIA granting program.
Canada
United States of America
Mexico
Colombia
Venezuela
Cuba
Jamaica
Haiti
Greenland
Iceland
United Kingdom
Ireland
Dominican Republic
Puerto Rico
Panama
Honduras
Costa Rica
Nicaragua
El Salvador
Bermuda
Anguilla
Antigua and Barbuda
Aruba
Bahamas
Barbados
British Virgin Islands
Cayman Islands
Dominica
Grenada
Guadeloupe
Martinique
Montserrat
Netherlands Antilles
Saint Kitts and Nevis
Saint Lucia
Saint Vincent and the Grenadines
Trinidad and Tobago
Turks and Caicos Islands
United States Virgin Islands
Belize
Guatemala
French Guiana
Surinam
Guyana

Droits : This item is presumed to be in the public domain. The University of Florida George A. Smathers Libraries respect the intellectual property rights of others and do not claim any copyright interest in this item. Users of this work have responsibility for determining copyright status prior to reusing, publishing or reproducing this item for purposes other than what is allowed by fair use or other copyright exemptions. Any reuse of this item in excess of fair use or other copyright exemptions may require permission of the copyright holder. The Smathers Libraries would like to learn more about this item and invite individuals or organizations to contact Digital Services (UFDC@uflib.ufl.edu) with any additional information they can provide.
002505687
AMM1472
http://ufdc.ufl.edu/UF00073698/00001

Éditeur(s) : Houghton, Mifflin Riverside Press Houghton, Mifflin ( Boston ) Riverside Press ( Cambridge Mass )
Résumé : (Bibliography) Includes bibliographical references and index.
(Citation/Reference) Thacher,
(Statement of Responsibility) by John Fiske.
United States of America -- Louisiana
United States of America -- Mississippi
United States of America -- Florida
Mexico
Peru
Paraguay
Guatemala
Canada -- Quebec
Brazil
Canada -- Newfoundland
Greenland
United States of America -- Alabama
United States of America -- Texas
Panama
Colombia
Venezuela
America
Latin America
Hispanoamâerica
Amâerique
Amâerique latine

05013275
08033630

Éditeur(s) : Gauthier-Villars
Résumé : Over 400,000 km of low level aeromagnetic data were collected by US Navy research organization over the Arctic Basin and Greenland-Norwegian Sea during the years 1972 to 1978. These data provide new constraints on the crustal structure and tectonic evolution of this vast region. Magnetic anomalies over continental fragments (Lomonosov Ridge and Chukchi Borderland) are irregular, with local short-wavelength features indicating relatively shallow basement. Sea-floor spreading between Scandinavia and Greenland commenced about 58 m.y.b.p. during the reversed period preceding anomaly 24. Spreading between the Lomonosov Ridge and Eurasia also began at this time or possibly somewhat earlier. An extinct spreading axis in the Canada Basin is indicated by gravity and magnetic data.
Oceanologica Acta, Special issue (0399-1784) (Gauthier-Villars), 1981

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00245/35663/34171.pdf
http://archimer.ifremer.fr/doc/00245/35663/

Éditeur(s) : HAL CCSD Elsevier
Résumé : LA-ICP-MS and SIMS U–Pb analyses have been performed on detrital zircon grains from four heavy mineral rich metasediments collected at different levels of the Nathorst Land Group (Eleonore Bay Supergroup, Greenland). Zircons from high-grade samples collected in the sillimanite and migmatite zones exhibit modifications to their structure, which are lacking in grains from a low-grade sample (0.3 GPa and 350–400 °C). In the sillimanite zone (0.5 GPa, 650 °C), thin discontinuous rims (<20 μm) plating detrital zircon grains document a metamorphic overgrowth during the Caledonian event dated at 428 ± 25 Ma (2σ). In the migmatite zone (0.4 GPa, 700 °C), zircons underwent severe recrystallisation processes but no new zircon growth. Ilmenite, which constitutes over 50% of the heavy mineral layers, underwent recrystallisation in both high-grade samples and is likely to represent the main source of Zr available for growth of zircon rims in the sillimanite zone. However, in the migmatite zone sample, the metamorphic conditions allowed titanite overgrowth around ilmenite, which acted as a sink for Zr and inhibited new zircon growth. 207Pb/206Pb ages for 152 detrital zircons broadly range between 2800 and 990 Ma. The detrital zircon age signature is characterized by the large predominance of late Paleoproterozoic (1.85–1.60 Ga) grains in all analysed samples and by lesser amounts of Archean (2.7–2.8 Ga) and Mesoproterozoic (1.2–1.0 Ga) zircons. The overall age range indicates that detritus can be sourced from the Labradorian and Makkovikian provinces of northeastern Laurentia. The youngest grain analysed (987 ± 18 Ma) indicates that deposition took place during the Neoproterozoic, in a post-Grenvillian sedimentary environment and was likely coeval with the Mid-Neoproterozoic episode of aborted rifting that affected the eastern margin of Laurentia. The lack of detritus originating from Amazonia or Baltica, placed adjacent to Laurentia during the early stages of Rodinia fragmentation, suggests that these two continental landmasses did not constitute a topographic high during the Neoproterozoic or that the Mid-Neoproterozoic rifting opened toward an open ocean to the north of a combined Laurentia/Baltica, thus resulting in a general south to north direction of transport of the sediments.
ISSN: 0301-9268

hal-00407204
https://hal.archives-ouvertes.fr/hal-00407204
DOI : 10.1016/j.precamres.2007.01.002

Résumé : This expedition was arranged on the initiative of Professor Erik Stensiö of Stockholm to collect fossil specimens for the British Museum (Natural History), the Palaeontologisk Museum, Oslo, and the Hiksmuseum , Stockholm. The chief object was to explore the Old Red Sandstone deposits in the geologically little known Wood Bay area and also in the neighbouring fjords on the north coast. The plans were given in The Polar Record, No. 18, and the final party, which was led by Professor E. A. Steusic with the support of A. Heintz of Oslo, consisted of E. Jarvik (Stockholm), G. Wangsjo (Uppsala), Sven Foyn and K. Aarhus (Oslo), X. Delle (Riga), E. I. White and W. N. Croft (London), J . A. Moy-Thomas (Oxford) and J. Brough (Manchester). C. Andreasen, a sealer from Tromso, brought the collecting party up to twelve. [NOT CONTROLLED OCR]

Droits : Scott Polar Research Institute, Cambridge, UK
http://archimer.ifremer.fr/doc/1940/publication-7341.pdf
http://archimer.ifremer.fr/doc/00000/7341/

Éditeur(s) : Amer Meteorological Soc
Résumé : A method to estimate mass and heat transports across hydrographic sections using hydrography together with altimetry data in a geostrophic box inverse model is presented. Absolute surface velocities computed from AVISO altimetry products made up of a combination of sea surface height measurements and geoid estimate are first compared to Ship Acoustic Doppler Current Profiler (S-ADCP) measurements of the Ovide project along hydrographic sections repeated every 2 years in summer from Portugal to Greenland. The rms difference between S-ADCP and altimetry velocities averaged on distances of about a hundred km accounts to 3.3 cm s−1. Considering that the uncertainty of S-ADCP velocities is found at 1.5 cm s−1, altimetry errors are estimated at 3 cm s−1. Transports across Ovide sections previously obtained using S-ADCP data to constrain the geostrophic inverse box model are used as reference. The new method is found useful to estimate absolute transports across the sections, as well as part of their variability. Despite associated uncertainties about 50% larger than when S-ADCP is used, our results for the North Atlantic Current and heat transports, with uncertainties of 10 to 15%, reproduce the variability already observed. The largest uncertainties are found in the estimates of the East Greenland Irminger Current (EGIC) transport (30%), induced by larger uncertainties associated with altimetry data at the western boundary.
Journal Of Atmospheric And Oceanic Technology (0739-0572) (Amer Meteorological Soc), 2011-10 , Vol. 28 , N. 10 , P. 1324-1337

Droits : 2011 American Meteorological Society
http://archimer.ifremer.fr/doc/00038/14921/13751.pdf
DOI:10.1175/2011JTECHO818.1
http://archimer.ifremer.fr/doc/00038/14921/

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Two types of olivine occur in kimberlites from Greenland, Canada and southern Africa. The first, xenocrystic olivine, displays several different forms. Most distinctive are 'nodules', a term we use to describe the large (1-5 mm), rounded, single crystals or polycrystalline aggregates that are a common constituent of many kimberlites. Olivine compositions are uniform within single nodules but vary widely from nodule to nodule, from Fo81 to 93. Within many nodules, sub- to euhedral asymmetric tablets have grown within larger anhedral olivine grains. Dislocation structures, particularly in the anhedral grains, demonstrate that this olivine was deformed before being incorporated into the kimberlite magma. Olivine grains in the kimberlite matrix between the nodules have morphologies similar to those of the tablets, suggesting that most matrix olivine grains are parts of disaggregated nodules. We propose that a sub- to euhedral form is not sufficient to identify phenocrysts in kimberlites and provide some criteria, based on morphology, internal deformation and composition, that distinguish phenocrysts from xenocrysts. The second type of olivine is restricted to rims surrounding xenocrystic grains. Only this olivine crystallized from the kimberlite magma. Major and trace element data for the rim olivine are used to calculate the composition of the parental kimberlite liquid, which is found to contain between about 20 and 30% MgO. The bulk compositions of many kimberlites contain higher MgO contents as a result of the presence of xenocrystic olivine. The monomineralic, dunitic, character of the nodules, and the wide range from Fo-rich to Fo-poor olivine compositions, provide major constraints on the origin of the nodules. Dunite is a relatively rare rock in the mantle and where present its olivine is persistently Fo-rich. The dunitic source of the nodules in kimberlites lacked minerals such as pyroxene and an aluminous phase, which make up about half of most mantle-derived rocks. It appears that these minerals were removed from the mantle peridotite that was to become the source of the nodules, and the Fo content of the retained olivine was modified during interaction with CO2-rich fluids whose arrival at the base of the lithosphere immediately preceded the passage of the kimberlite magmas. Fragments of the resultant dunite were entrained into the kimberlite, where they were retained both as intact nodules and as disaggregated grains in the matrix.
ISSN: 0022-3530

insu-00543321
https://hal-insu.archives-ouvertes.fr/insu-00543321
BIBCODE : 10.1093/petrology/egp080
DOI : 10.1093/petrology/egp080

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Most kimberlites contain abundant dunitic nodules. These are centimetre-sized, rounded and multi-grained assemblages of xenocrystic olivine with a wide range of compositions (Fo83 to Fo94). The absence of orthopyroxene and other mantle minerals and the range of olivine compositions have been attributed to reaction between mantle peridotite and (proto)kimberlitic fluid or melt, but the timing of the reaction is a subject of debate. In a kimberlite from the Kangamiut region of Greenland, nodule cores are surrounded by fine-grained outer margins with near-constant Fo contents (∼Fo88) but highly variable minor element contents (e.g. 500–2500 ppm Ni). These margins crystallized from the kimberlite melt and we show that their compositions can be explained by crystallization of olivine alone, if a high partition coefficient for Ni between melt and olivine (DNi > 20) is assumed. Orthopyroxene assimilation is not required, removing the constraint that its dissolution occurred during ascent of the kimberlite magma. Within some nodules, in addition to the usual core-to-margin gradients, we observe asymmetric compositional changes (variable Fo but near-constant minor element contents) across mobile grain boundaries. These changes document fluid percolation at the grain scale that occurred during dynamic recrystallization in the deforming lithospheric mantle. We note that chemical gradients associated with mobile grain boundaries are observed in olivines that cover the entire compositional range of the nodules, and propose that fluid-assisted dynamic recrystallization took place in dunite that was already compositionally heterogeneous. Reaction between peridotite and protokimberlitic melt or fluid and dissolution of orthopyroxene thus occurred within the lithospheric mantle, immediately (a few days) prior to the ascent of the kimberlite melt and the entrainment of the dunite nodules. We propose that the grain boundary zones probably mimic, at a fine scale, the fluid–peridotite interaction that caused, at a larger scale, orthopyroxene dissolution and formation of compositionally diverse olivine in kimberlites.
ISSN: 0022-3530

hal-01277963
https://hal.archives-ouvertes.fr/hal-01277963
DOI : 10.1093/petrology/egv054

Éditeur(s) : HAL CCSD National Academy of Sciences
Résumé : International audience
The Isua Supracrustal Belt, Greenland, of Early Archean age (3.81-3.70 Ga) represents the oldest crustal segment on Earth. Its complex lithology comprises an ophiolite-like unit and volcanic rocks reminiscent of boninites, which tie Isua supracrustals to an island arc environment. We here present zinc (Zn) isotope compositions measured on serpentinites and other rocks from the Isua supracrustal sequence and on serpentinites from modern ophiolites, midocean ridges, and the Mariana forearc. In stark contrast to modern midocean ridge and ophiolite serpentinites, Zn in Isua and Mariana serpentinites is markedly depleted in heavy isotopes with respect to the igneous average. Based on recent results of Zn isotope fractionation between coexisting species in solution, the Isua serpentinites were permeated by carbonate- rich, high- pH hydrothermal solutions at medium temperature (100-300 degrees C). Zinc isotopes therefore stand out as a pH meter for fossil hydrothermal solutions. The geochemical features of the Isua fluids resemble the interstitial fluids sampled in the mud volcano serpentinites of the Mariana forearc. The reduced character and the high pH inferred for these fluids make Archean serpentine mud volcanoes a particularly favorable setting for the early stabilization of amino acids.
ISSN: 0027-8424

insu-00674714
https://hal-insu.archives-ouvertes.fr/insu-00674714
DOI : 10.1073/pnas.1108061108

Éditeur(s) : HAL CCSD Mineralogical Society of America
Résumé : International audience
Pressure-temperature divariant melting phase relations of model carbonated peridotite in the system CaO-MgO-Al2O3-SiO2-CO2 from 8 to 12 GPa are reported. From 8 to 12 GPa, melting temperatures on the studied pressure-temperature divariant surface rise quite rapidly. Liquids, in equilibrium with forsterite, orthopyroxene, clinopyroxene, and garnet, on the low-temperature side of the divariant surface are magnesiocarbonatitic in composition. With increasing temperature along an isobar on the pressure-temperature divariant surface, and with the same crystalline phase assemblage, liquids gradually become kimberlitic in their composition. Given the model system data reported here, Group IB kimberlites and perhaps some kimberlites from Greenland, Canada, and South Africa could be generated from direct melting of carbonated peridotite in the pressure range of approximately 6-8 GPa. Some kimberlites from Canada and Russia could have formed by partial melting of carbonated mantle peridotite at pressures of about 10-12 GPa. From 8 to 12 GPa, liquid compositions on the studied divariant surface show a limited compositional range, which implies that the divariant surface is essentially flat. The implied flatness of the divariant surface, and so long as the liquid is in equilibrium with the crystalline assemblage of forsterite + orthopyroxene + clinopyroxene + garnet on the divariant surface, indicate that kimberlites belonging to Group IA and those more magnesian than Group IA cannot have their origin in only being a melting product of carbonated mantle peridotite. The absence of topography of the studied pressure-temperature divariant surface in all likelihood limits the generation of kimberlites in the Earth's upper mantle only.
ISSN: 0003-004X

hal-01053915
https://hal.archives-ouvertes.fr/hal-01053915
DOI : 10.2138/am.2014.4826

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
High 3He/4He ratios in some basalts have generally been interpreted as originating in an incompletely degassed lower-mantle source1, 2, 3, 4, 5, 6, 7, 8, 9. This helium source may have been isolated at the core-mantle boundary region since Earth's accretion4, 5, 6. Alternatively, it may have taken part in whole-mantle convection and crust production over the age of the Earth7, 8, 9; if so, it is now either a primitive refugium at the core-mantle boundary8 or is distributed throughout the lower mantle7, 9. Here we constrain the problem using lavas from Baffin Island, West Greenland, the Ontong Java Plateau, Isla Gorgona and Fernandina (Galapagos). Olivine phenocryst compositions show that these lavas originated from a peridotite source that was about 20 per cent higher in nickel content than in the modern mid-ocean-ridge basalt source. Where data are available, these lavas also have high 3He/4He. We propose that a less-degassed nickel-rich source formed by core-mantle interaction during the crystallization of a melt-rich layer or basal magma ocean5, 6, and that this source continues to be sampled by mantle plumes. The spatial distribution of this source may be constrained by nickel partitioning experiments at the pressures of the core-mantle boundary.
ISSN: 0028-0836

hal-00941025
https://hal.archives-ouvertes.fr/hal-00941025
DOI : 10.1038/nature11771