Evolution of the trace element contents (Sr and Mn) of hemipelagic carbonates from the Zumaia Paleocene section (Gipuzkoa, Spain): implications for the knowledge of seawater chemistry during the Selandian

2014 ◽  
Vol 185 (6) ◽  
pp. 413-435 ◽  
Author(s):  
Laurence Le Callonnec ◽  
Maurice Renard ◽  
Marc De Rafélis ◽  
Fabrice Minoletti ◽  
Catherine Beltran ◽  
...  
Keyword(s):  
Trace Element ◽  
North Atlantic ◽  
Absorption Spectrometry ◽  
Minor Role ◽  
Burial Diagenesis ◽  
The North ◽  
Trace Element Contents ◽  
Mn Content ◽  
The North Atlantic ◽  
Element Contents

AbstractWell exposed and stratigraphically well constrained by numerous studies, the Zumaia section is one of the best places to conduct studies on the Palaeocene in basin facies. Thus, this section has been chosen [Schmitz et al., 2011] as a stratotype of Selandian basal and terminal limits (GSSP: Global boundary Stratotype Section and Point). The sediments consist of carbonate hemipelagites interbedded with fine carbonate (Maastrichtian to Selandian) and siliciclastic (Thanetian to Eocene) turbidites.The purpose of this work is to geochemically characterize the Selandian by trace element contents (strontium and manganese) and to try to assess the chemical composition of seawater during the Paleocene. Analysis of various separated granulometric fine fractions show that hemipelagic sediments from the Zumaia section present a high preservation quality of the original records of trace-element contents. Late burial diagenesis plays only a minor role and geochemical breaks are not reducible to a change in the nature of carbonate producers.The strontium contents of Paleocene sediments require that the Sr/Ca ratio of seawater was lower than that in the present ocean. The Selandian is characterized by a positive excursion of the strontium curve. This accident is also recognized in several worldwide sections and is related to the platform/basin carbonate sedimentation budget and the intensity of oceanic hydrothermalism.The Mn content of hemipelagites is very high and can reach 2500–3000 ppm in the Paleocene. A comparison of analyses by atomic absorption spectrometry (AAS) and electron paramagnetic resonance (EPR) shows that both Mn2+ (in the calcite lattice) and Mn4+ (as oxide micro nodules) coexist. The Mn content fluctuations are related to the opening phases of the North Atlantic during the Paleocene by submarine volcanism and hydrothermalism in the North Atlantic Igneous Province (NAIP).

Age and Geochemical Studies of the Snyder Breccia, Coastal Labrador

1975 ◽  
Vol 12 (3) ◽  
pp. 361-370 ◽  
Author(s):  
Jackson M. Barton Jr. ◽  
Erika S. Barton
Keyword(s):  
Trace Element ◽  
North Atlantic ◽  
Layered Intrusion ◽  
Basement Complex ◽  
Fine Grained ◽  
The North ◽  
Isotopic Analyses ◽  
The Matrix ◽  
The North Atlantic ◽  
Geochemical Studies

The Snyder breccia is composed of angular to subrounded xenoliths of migmatites and amphibolites in a very fine grained matrix. It is apparently intrusive into the metasediments of the Snyder Group exposed at Snyder Bay, Labrador. The Snyder Group unconformably overlies a migmatitic and amphibolitic basement complex and is intruded by the Kiglapait layered intrusion. K–Ar ages indicate that the basement complex is Archean in age (> 2600 m.y. old) and that the Kiglapait layered intrusion was emplaced prior to 1280 m.y. ago. Major and trace element analyses of the matrix of the Snyder breccia indicate that while it was originally of tonalitic composition, later it locally underwent alteration characterized by loss of sodium and strontium and gain of potassium, rubidium and barium. Rb–Sr isotopic analyses show that this alteration occurred about 1842 m.y. ago, most probably contemporaneously with emplacement of the breccia. The Snyder Group thus was deposited sometime between 2600 and 1842 m.y. ago and may be correlative with other Aphebian successions preserved on the North Atlantic Archean craton.

Halogens in the mantle beneath the North Atlantic

1980 ◽  
Vol 297 (1431) ◽  
pp. 147-178 ◽  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Partial Melting ◽  
North Atlantic ◽  
Low Pressure ◽  
The North ◽  
Mid Atlantic Ridge ◽  
Ionic Size ◽  
The North Atlantic ◽  
Incompatible Trace Elements

F, Cl and Br contents of tholeiitic volcanic glasses dredged along the Mid-Atlantic Ridge from 53° to 28° N, including the transect over the Azores Plateau, are reported. The halogen variations parallel those of 87 Sr/ 86 Sr, La/Sm or other incompatible elements of varying volatility. The latitudinal halogen variation pattern is not obliterated if only Mg-rich lavas are considered. Variations in extent of low-pressure fractional crystallization or partial melting conditions do not appear to be the primary cause of the halogen variations. Instead, mantle-derived heterogeneities in halogens, with major enrichments in the mantle beneath the Azores, are suggested. The Azores platform is not only a ‘hotspot’ but also a ‘wetspot’, which may explain the unusually intense Azores volcanic activity. The magnitude of the halogen and incompatible element enrichments beneath the Azores appear strongly dependent on the size of these anions and cations, but independent of relative volatility at low pressure. The large anions Cl and Br behave similarly to large cations Rb, Cs and Ba, and the smaller anion F similarly to Sr and P. Processes involving crystal and liquid (fluid and/or melt), CO 2 rather than H 2 O dominated, seem to have produced these largescale mantle heterogeneities. Geochemical ‘anomalies’ beneath the Azores are no longer apparent for coherent element pair ratios of similar ionic size. Values of such ‘unfractionated’ coherent trace element ratios provide an indication of the mantle composition and its nature before fractionation event (s) which produced the inferred isotopic and trace element heterogeneities apparently present beneath the North Atlantic. The relative trace element composition of this precursor mantle does not resemble that of carbonaceous chondrites except for refractory trace element pairs of similar ionic size. It is strongly depleted in halogens, and to a lesser extent in large alkali ions Rb and Cs relative to refractory Ba. These relative depletions are comparable within a factor of 5 to Ganapathy & Anders’s estimates for the bulk Earth, with the exception of Cs. There is also evidence for removal of phosphorus into the iron core during its formation. With the exception of San Miguel, alkali basalts from the Azores Islands appear to have been derived from the same mantle source as tholeiitic basalts from the ridge transect over the Azores Platform but by half as much degree of partial melting. The Azores subaerial basalts seem to have been partly degassed in Cl, Br and F, in decreasing order of intensity. A working model involving metasomatism from release of fluids at phase transformation during convective mantle overturns is proposed to explain the formation of mantle plumes or diapirs enriched in larger relative to smaller halogen and other incompatible trace elements. The model is ad hoc and needs testing. However, any other dynamical model accounting for the 400 -1000 km long gradients in incompatible trace elements, halogens and radiogenic isotopes along the Mid-Atlantic Ridge should, at some stage, require either (1) some variable extent of mixing or (2) differential migration of liquid relative to crystals followed by re-equilibration (or both), as a diffusion controlled mechanism over such large distances is clearly ruled out, given the age of the Earth.

scholarly journals Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

2020 ◽  
Vol 4 (11) ◽  
pp. 2185-2204
Author(s):  
Nolwenn Lemaitre ◽  
Hélène Planquette ◽  
Frank Dehairs ◽  
Frédéric Planchon ◽  
Géraldine Sarthou ◽  
...  
Keyword(s):  
Trace Element ◽  
North Atlantic ◽  
The North ◽  
The North Atlantic

scholarly journals Hard cash, easy credit, fictitious capital: Critical reflections on money as a fetishised social relation

2015 ◽  
Vol 1 (1) ◽  
pp. 20-37 ◽  
Author(s):  
Bob Jessop
Keyword(s):  
Financial Crisis ◽  
North Atlantic ◽  
Social Relation ◽  
Minor Role ◽  
The North ◽  
Fictitious Capital ◽  
Key Concepts ◽  
The North Atlantic ◽  
A Minor

This article explores some aspects of money as a social relation. Starting from Polanyi, it explores the nature of money as a non-commodity, real commodity, quasi-commodity, and fictitious commodity. The development of credit-debt relations is important in the last respect, especially in market economies where money in the form of coins and banknotes plays a minor role. This argument is developed through some key concepts from Marx concerning money as a fetishised and contradictory social relation, especially his crucial distinction, absent from Polanyi, between money as money and money as capital, each with its own form of fetishism. Attention then turns to Minsky’s work on Ponzi finance and what one might describe as cycles of the expansion of easy credit and the scramble for hard cash. This analysis is re-contextualised in terms of financialisation and finance-dominated accumulation, which promote securitisation and the autonomisation of credit money, interest-bearing capital. The article ends with brief reflections on the role of easy credit and hard cash in the surprising survival of neo-liberal economic and political regimes since the North Atlantic Financial Crisis became evident.

scholarly journals Great Basin hydrology, paleoclimate, and connections with the North Atlantic: A speleothem stable isotope and trace element record from Lehman Caves, NV

2015 ◽  
Vol 127 ◽  
pp. 186-198 ◽  
Author(s):  
Mellissa Cross ◽  
David McGee ◽  
Wallace S. Broecker ◽  
Jay Quade ◽  
Jeremy D. Shakun ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Trace Element ◽  
Great Basin ◽  
North Atlantic ◽  
The North ◽  
Basin Hydrology ◽  
The North Atlantic

scholarly journals Evolution of Subduction Dynamics beneath West Avalonia in Middle to Late Ordovician Times

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-22
Author(s):  
Pierre Jutras ◽  
J. Brendan Murphy ◽  
Dennis Quick ◽  
Jaroslav Dostal
Keyword(s):  
Trace Element ◽  
Partial Melting ◽  
Volcanic Rocks ◽  
Upper Ordovician ◽  
The North ◽  
Trace Element Contents ◽  
Element Contents ◽  
Arc Setting ◽  
Back Arc ◽  
High Degree

Abstract Middle to Upper Ordovician volcanic rocks in the Arisaig area of Nova Scotia, Canada, constitute the only known record of volcanism in West Avalonia during that interval. Hence, they have been extensively studied to test paleocontinental reconstructions that consistently show Avalonia as a drifting microcontinent during that period. Identification of volcanic rocks with an intermediate composition (the new Seaspray Cove Formation) between upper Darriwilian bimodal volcanic rocks of the Dunn Point Formation and Sandbian felsic pyroclastic rocks of the McGillivray Brook Formation has led to a reevaluation of magmatic relationships in the Ordovician volcanic suite at Arisaig. Although part of the same volcanic construction, the three formations are separated by significant time-gaps and are shown to belong to three distinct magmatic subsystems. The tectonostratigraphic context and trace element contents of the Dunn Point Formation basalts suggest that they were produced by the high-degree partial melting of an E-MORB type source in a back-arc extensional setting, whereas trace element contents in intermediate rocks of the Seaspray Cove Formation suggest that they were produced by the low-degree partial melting of a subduction-enriched source in an arc setting. The two formations are separated by a long interval of volcanic quiescence and deep weathering, during which time the back-arc region evolved from extension to shortening and was eventually onlapped by arc volcanic rocks. Based on limited field constraints, paleomagnetic and paleontological data, this progradation of arc onto back-arc volcanic rocks occurred from the north, where an increasingly young Iapetan oceanic plate was being subducted at an increasingly shallow angle. Partial subduction of the Iapetan oceanic ridge is thought to have subsequently generated slab window magmatism, thus marking the last pulse of subduction-related volcanism in both East and West Avalonia.

scholarly journals Trace-element abundances in the shallow lithospheric mantle of the North Atlantic Craton margin: Implications for melting and metasomatism beneath Northern Scotland

2015 ◽  
Vol 79 (4) ◽  
pp. 877-907 ◽  
Author(s):  
Hannah S. R. Hughes ◽  
Iain McDonald ◽  
John W. Faithfull ◽  
Brian G. J. Upton ◽  
Hilary Downes
Keyword(s):  
Trace Element ◽  
North Atlantic ◽  
Lithospheric Mantle ◽  
Geographical Location ◽  
Mantle Xenoliths ◽  
Dyke Swarm ◽  
Element Abundances ◽  
The North ◽  
The North Atlantic ◽  
North Atlantic Craton

AbstractBulk rock geochemistry and major- and trace-element compositions of clinopyroxene have been determined for three suites of peridotitic mantle xenoliths from the North Atlantic Craton (NAC) in northern Scotland, to establish the magmatic and metasomatic history of subcontinental lithospheric mantle (SCLM) below this region. Spinel lherzolites from the southernmost locality (Streap Com'laidh) have non-NAC mantle compositions, while the two northern xenolith suites (Loch Roag and Rinibar) are derived from the thinned NAC marginal keel. Clinopyroxene compositions have characteristic trace-element signatures which show both 'primary' and 'metasomatic' origins. We use Zr and Hf abundances to identify ancient cryptic refertilization in 'primary' clinopyroxenes. We suggest that Loch Roag and Rinibar peridotite xenoliths represent an ancient Archaean-Palaeoproterozoic SCLM with original depleted cratonic signatures which were overprinted by metasomatism around the time of intrusion of the Scourie Dyke Swarm (∼2.4 Ga). This SCLM keel was preserved during Caledonian orogenesis, although some addition of material and/or metasomatism probably also occurred, as recorded by Rinibar xenoliths. Rinibar and Streap xenoliths were entrained in Permo-Carboniferous magmas and thus were isolated from the SCLM ∼200 Ma before Loch Roag xenoliths (in an Eocene dyke). Crucially, despite their geographical location, lithospheric mantle peridotite samples from Loch Roag show no evidence of recent melting or refertilization during the Palaeogene opening of the Atlantic.

scholarly journals Objective quantification of perturbations produced with a piecewise PV inversion technique

2007 ◽  
Vol 25 (11) ◽  
pp. 2335-2349 ◽  
Author(s):  
L. Fita ◽  
R. Romero ◽  
C. Ramis
Keyword(s):  
North Atlantic ◽  
Initial Conditions ◽  
Thermal Anomaly ◽  
Western Mediterranean ◽  
Point Of View ◽  
Minor Role ◽  
The North ◽  
Western Mediterranean Basin ◽  
The North Atlantic ◽  
Upper Level

Abstract. PV inversion techniques have been widely used in numerical studies of severe weather cases. These techniques can be applied as a way to study the sensitivity of the responsible meteorological system to changes in the initial conditions of the simulations. Dynamical effects of a collection of atmospheric features involved in the evolution of the system can be isolated. However, aspects, such as the definition of the atmospheric features or the amount of change in the initial conditions, are largely case-dependent and/or subjectively defined. An objective way to calculate the modification of the initial fields is proposed to alleviate this problem. The perturbations are quantified as the mean absolute variations of the total energy between the original and modified fields, and an unique energy variation value is fixed for all the perturbations derived from different PV anomalies. Thus, PV features of different dimensions and characteristics introduce the same net modification of the initial conditions from an energetic point of view. The devised quantification method is applied to study the high impact weather case of 9–11 November 2001 in the Western Mediterranean basin, when a deep and strong cyclone was formed. On the Balearic Islands 4 people died, and sustained winds of 30 ms−1 and precipitation higher than 200 mm/24 h were recorded. Moreover, 700 people died in Algiers during the first phase of the event. The sensitivities to perturbations in the initial conditions of a deep upper level trough, the anticyclonic system related to the North Atlantic high and the surface thermal anomaly related to the baroclinicity of the environment are determined. Results reveal a high influence of the upper level trough and the surface thermal anomaly and a minor role of the North Atlantic high during the genesis of the cyclone.

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