scholarly journals A mantle plume origin for the Scandinavian Dyke Complex: a “piercing point” for 615 Ma plate reconstruction of Baltica?

2021 ◽  
Author(s):  
Christian Tegner ◽  
Torgeir B. Andersen ◽  
Hans Jørgen Kjøll ◽  
Eric L. Brown ◽  
Graham Hagen-Peter ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Major And Trace Elements ◽  
Dolerite Dyke ◽  
The North ◽  
Iapetus Ocean ◽  
The Pacific ◽  
Igneous Provinces ◽  
Research Problems ◽  
Plate Reconstructions ◽  
Geodynamic Models

<p>The origin of Large Igneous Provinces (LIPs) associated with continental breakup and the reconstruction of continents older than c. 320 million years (pre-Pangea) are contentious research problems. Here we study the petrology of a 615 - 590 Myr dolerite dyke complex that intruded rift-basins of the magma-rich margin of Baltica and now is exposed in the Scandinavian Caledonides. These dykes are part of the Central Iapetus Magmatic Province (CIMP), a LIP emplaced in Baltica and Laurentia during opening of the Iapetus Ocean within the Caledonian Wilson Cycle. The >1000 km long dyke complex displays lateral geochemical zonation from enriched to depleted basaltic compositions from south to north. Geochemical modelling of major and trace elements shows these compositions are best explained by melting hot mantle 75-250°C above ambient mantle. Although the trace element modelling solutions are non-unique, the best explanation involves melting a laterally zoned mantle plume with enriched and depleted peridotite lithologies, similar to present-day Iceland and to the North Atlantic Igneous Province. The origin of CIMP appears to have involved several mantle plumes. This is best explained if rifting and breakup magmatism coincided with plume generation zones at the margins of a Large Low Shear-wave Velocity Province (LLSVP) at the core mantle boundary. If the LLSVPs are quasi-stationary back in time as suggested in recent geodynamic models, the CIMP provides a guide for reconstructing the paleogeography of Baltica and Laurentia 615 million years ago to the LLSVP now positioned under the Pacific Ocean. Our results provide a stimulus for using LIPs as piercing points for plate reconstructions.</p>

scholarly journals A Comparison of Major and Trace Element Compositions of Chromites from the Stillwater, Bushveld and Great Dyke Layered Intrusions with Chromites from Komatiites, Boninites and Large Igneous Provinces.

2020 ◽  
Author(s):  
Sarah-Jane Barnes ◽  
Eduardo Mansur ◽  
Philippe Pagé ◽  
Julien Meric ◽  
Jean-Philippe Arguin
Keyword(s):  
Minor Element ◽  
Major And Trace Elements ◽  
Layered Intrusions ◽  
Flood Basalts ◽  
Continental Flood Basalts ◽  
Great Dyke ◽  
Minor Elements ◽  
The North ◽  
Igneous Provinces ◽  
Icp Ms

<p>The composition of the magmas from which the chromites that form the massive chromite layers of the Stillwater, Great Dyke and Bushveld Complexes are of interest both to understand the economic importance of the resources in the layers (Cr and PGE), but also in understanding how these layers form.  Magmas that have been suggested as parental to the intrusions are boninites or crustally contaminated komatiites.  Another magma that could be considered in recognition of the continental setting of the Bushveld and Great Dyke is picrite associated with continental flood basalts. In order to investigate whether any of these magmas are suitable parental magmas for the chromites we have determined major and trace elements in komatiites of low metamorphic grade, boninites and chromites from low-Ti and high-Ti picrites of the Emeishan Provence.</p><p>In order to test whether the chromites are in equilibrium with volcanic magmas we first modelled the major and minor element composition of the chromites that should have crystallized from the komatiite, boninites and picrite liquids using SpinMelt v2.  The compositions are approximately correct.  In terms of major and minor elements none of the chromites from the layered intrusions match boninite chromites.  The Great Dyke chromites are similar to chromites from komatiites.  The chromites the Bushveld are slightly more evolved with higher Ti contents and lower Cr# and resemble the chromites from the low-Ti picrites of Emeishan.  The Stillwater chromites have similar Ti contents to the Emeishan low-Ti picrites, but have lower Cr#.  Their compositions resemble chromite compositions reported from the North Atlantic Igneous Provence.</p><p>Hafnium, Ta, Cu, Sn, Sc, Ti, Mn, Ni, Co, Mn, Ga, V and Zn were determined by LA-ICP-MS.  To compare the composition of the chromites an estimate of their partition coefficients into chromite was made based on the concentrations of elements in komatiite chromite divided by element in komatiite.  The elements were then arranged in order of compatibility and the chromites normalized to the median komatiite chromite.  Podiform chromites from boninites are depleted in most elements and none of the layered intrusions chromites resemble them.  The chromites from the Great Dyke have essentially flat patterns close to 1 times komatiite, but with negative Cu anomaly and a slight positive Sn anomaly.  The Bushveld and Stillwater chromites are richer in Al, Ga, V and Ti than the komatiite chromite and are depleted in Cu.  The patterns resemble the chromites form the low Ti-picrites form Sn to Zn, but differ from picrites from Hf to Cu.  The picrites are enriched in Hf, Ta and Cu.</p><p>The chromite compositions suggest that boninite magmas are not involved in forming the chromites from layered intrusions.  The Great Dyke chromites appear to have a komatiitic affinity.  The Bushveld and Stillwater chromites appear to have a low-Ti picrite affinity.</p>

WTO SUCCESSOR TO GATT

1997 ◽  
Vol 14 (2) ◽  
pp. 172-187
Author(s):  
Arif Sultan
Keyword(s):  
North Africa ◽  
European Economic Community ◽  
Developed Countries ◽  
Economic Community ◽  
Land Area ◽  
The North ◽  
Muslim Countries ◽  
The Pacific ◽  
The World ◽  
The Developed Countries

Within a short span of time a number of economic blocs have emergedon the world horizon. In this race, all countriedeveloped, developingand underdeveloped-are included. Members of the North America FreeTrade Agreement (NAITA) and the European Economic Community(EEC) are primarily of the developed countries, while the EconomicCooperation Organization (ECO) and the Association of South EastAsian Nations (ASEAN) are of the developing and underdevelopedAsian countries.The developed countries are scrambling to create hegemonies throughthe General Agreement on Tariff and Trade (GATT). In these circumstances,economic cooperation among Muslim countries should be onthe top of their agenda.Muslim countries today constitute about one-third of the membershipof the United Nations. There are around 56 independentMuslim states with a population of around 800 million coveringabout 20 percent of the land area of the world. Stretchingbetween Atlantic and the Pacific Oceans, the Muslim Worldstraddles from North Africa to Indonesia, in two major Islamicblocs, they are concentrated in the heart of Africa to Indonesia,in two major blocs, they are concentrated in the heart of Africaand Asia and a smaller group in South and Southeast Asia.'GATT is a multilateral agreement on tariffs and trade establishing thecode of rules, regulations, and modalities regulating and operating internationaltrade. It also serves as a forum for discussions and negotiations ...

scholarly journals The evolving response of mesopelagic fishes to declining midwater oxygen concentrations in the southern and central California Current

2018 ◽  
Vol 76 (3) ◽  
pp. 626-638 ◽  
Author(s):  
J Anthony Koslow ◽  
Pete Davison ◽  
Erica Ferrer ◽  
S Patricia A Jiménez Rosenberg ◽  
Gerardo Aceves-Medina ◽  
...  
Keyword(s):  
Baja California ◽  
Southern Oscillation ◽  
Global Climate ◽  
California Current ◽  
Deep Ocean ◽  
Near Surface ◽  
Oxygen Minimum Zones ◽  
The North ◽  
The Pacific ◽  
Oxygen Concentrations

Abstract Declining oxygen concentrations in the deep ocean, particularly in areas with pronounced oxygen minimum zones (OMZs), are a growing global concern related to global climate change. Its potential impacts on marine life remain poorly understood. A previous study suggested that the abundance of a diverse suite of mesopelagic fishes off southern California was closely linked to trends in midwater oxygen concentration. This study expands the spatial and temporal scale of that analysis to examine how mesopelagic fishes are responding to declining oxygen levels in the California Current (CC) off central, southern, and Baja California. Several warm-water mesopelagic species, apparently adapted to the shallower, more intense OMZ off Baja California, are shown to be increasing despite declining midwater oxygen concentrations and becoming increasingly dominant, initially off Baja California and subsequently in the CC region to the north. Their increased abundance is associated with warming near-surface ocean temperature, the warm phase of the Pacific Decadal oscillation and Multivariate El Niño-Southern Oscillation Index, and the increased flux of Pacific Equatorial Water into the southern CC.

The Relevance of Old World Archaeology to the First Entry of Man into New Worlds: Colonization Seen from the Antipodes

1977 ◽  
Vol 8 (1) ◽  
pp. 128-148 ◽  
Author(s):  
Sylvia J. Hallam
Keyword(s):  
Demographic Data ◽  
Ecological Zones ◽  
The North ◽  
Technological Potential ◽  
The Pacific ◽  
Peopling Of The Americas ◽  
Rapid Spread ◽  
History Of ◽  
Economic Innovation ◽  
Considerable Complexity

Following several discussions in recent numbers of Quaternary Research on the peopling of the Americas, this paper suggests that movements into the New World should be viewed in the wider context of subsistence, technology, and movement around the western littorals of the Pacific, resulting in the colonization not of one but of two new continents by men out of Asia. Specific points which have been raised by these recent papers are reviewed in the light of Australian, Wallacian, and East Asian data.(1) The earliness of watercraft is evidenced by chronology of the human diaspora through Wallacia and Greater Australia.(2) The simplistic nomenclature of chopper-flake traditions masks considerable complexity and technological potential, revealed in detailed Antipodean studies.(3) These traditions also have great potential for adapting to differing ecological zones, evidenced within Greater Australia; and for technological and economic innovation there, through Southeast Asia, and to Japan and the north Asian littoral.(4) The history of discovery and the nature of the evidence from Australia cannot validly be used to controvert early dates in the Americas.(5) Demographic data from Australia suggest that total commitment to a rapid-spread “bowwave” model for the peopling of new continents may be unwise.

scholarly journals Research Gap Analysis of Remote Sensing Application in Fisheries: Prospects for Achieving the Sustainable Development Goals

2021 ◽  
Vol 13 (5) ◽  
pp. 1013
Author(s):  
Kuo-Wei Yen ◽  
Chia-Hsiang Chen
Keyword(s):  
Sustainable Development ◽  
Indian Ocean ◽  
Atlantic Ocean ◽  
The Sustainable Development ◽  
The North ◽  
The Pacific ◽  
Development Goals ◽  
The Indian Ocean ◽  
The Pacific Ocean ◽  
Research Hotspots

Remote sensing (RS) technology, which can facilitate the sustainable management and development of fisheries, is easily accessible and exhibits high performance. It only requires the collection of sufficient information, establishment of databases and input of human and capital resources for analysis. However, many countries are unable to effectively ensure the sustainable development of marine fisheries due to technological limitations. The main challenge is the gap in the conditions for sustainable development between developed and developing countries. Therefore, this study applied the Web of Science database and geographic information systems to analyze the gaps in fisheries science in various countries over the past 10 years. Most studies have been conducted in the offshore marine areas of the northeastern United States of America. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. This study also found that research hotspots of satellite RS applications in fisheries were mainly conducted in (1) the northeastern sea area in the United States, (2) the high seas area of the North Atlantic Ocean, (3) the surrounding sea areas of France, Spain and Portugal, (4) the surrounding areas of the Indian Ocean and (5) the East China Sea, Yellow Sea and Bohai Bay sea areas to the north of Taiwan. A comparison of publications examining the three major oceans indicated that the Atlantic Ocean was the most extensively studied in terms of RS applications in fisheries, followed by the Indian Ocean, while the Pacific Ocean was less studied than the aforementioned two regions. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. The Atlantic Ocean and the Indian Ocean have been the subjects of many local in-depth studies; in the Pacific Ocean, the coastal areas have been abundantly investigated, while offshore local areas have only been sporadically addressed. Collaboration and partnership constitute an efficient approach for transferring skills and technology across countries. For the achievement of the sustainable development goals (SDGs) by 2030, research networks can be expanded to mitigate the research gaps and improve the sustainability of marine fisheries resources.

War stimulus: The Japanese threat and rebirth of the North America Pacific Coast shipbuilding industry, 1937-1946

2021 ◽  
Vol 33 (2) ◽  
pp. 382-411
Author(s):  
Chris Madsen
Keyword(s):  
United States ◽  
Supply Chain ◽  
Pacific Coast ◽  
The United States ◽  
Pearl Harbor ◽  
Shipbuilding Industry ◽  
The North ◽  
The Pacific ◽  
Before And After ◽  
Strategic Procurement

Henry Eccles, in classic studies on logistics, describes the dynamics of strategic procurement in the supply chain stretching from home countries to military theatres of operations. Naval authorities and industrialists concerned with Japanese aggression before and after Pearl Harbor looked towards developing shipbuilding capacity on North America’s Pacific Coast. The region turned into a volume producer of merchant vessels, warships and auxiliaries destined for service in the Pacific and Indian Oceans. Shipbuilding involved four broad categories of companies in the United States and Canada that enabled the tremendous production effort.

A 2011-2018 Fukushima Perspective on North Pacific Mode Water Pathways

2021 ◽  
Author(s):  
Alison Macdonald ◽  
Sachiko Yoshida ◽  
Irina Rypina
Keyword(s):  
North Pacific ◽  
Half Life ◽  
Nuclear Power ◽  
North Pacific Ocean ◽  
Data Sets ◽  
Mode Water ◽  
Eastern Basin ◽  
Mode Waters ◽  
The North ◽  
The Pacific

<p>This investigation uses the tracer information provided by the 2011 direct ocean release of radio-isotopes, (<sup>137</sup>Cs, ~30-year half-life and <sup>134</sup>Cs, ~2-year half-life) from the Fukushima Dai-ichi nuclear power plant (FDNPP) together with hydrographic profiles to better understand the origins and pathways of mode waters in the North Pacific Ocean. While using information provided by radionuclide observations taken from across the basin, the main focus is on the eastern basin and results from analyses of two data sets 2015 (GO-SHIP) and 2018 (GEOTRACES) along the 152°W meridian. The study looks at how mode waters formed in the spring of 2011 have spread and mixed, and how they have not. Our radiocesium isotope samples tell a story of a surprisingly confined pathway for these waters and suggest that circulation to the north into the subpolar gyre occurs more quickly than circulation to the south into the subtropical gyre. They indicate that in spite of crossing 6000 km in their journey across the Pacific, the densest 2011 mode waters stayed together spreading by only a few hundred kilometers in the north/south direction, remained subsurface (below ~200 m) for most of the trip, and only saw the atmosphere again as they followed shoaling density surfaces into the boundary of the Alaska Gyre. The more recent data are sparse and do not allow direct measurement of the FDNPP specific <sup>134</sup>Cs, however they do provide some information on mode water evolution in the eastern North Pacific seven years after the accident. </p>

Evolution of the East Africa-Arabia plume head

2021 ◽  
Author(s):  
Chiara Civiero ◽  
Sergei Lebedev ◽  
Nicolas L. Celli
Keyword(s):  
East Africa ◽  
Basic Mechanism ◽  
Continental Lithosphere ◽  
Gulf Of Aden ◽  
Low Velocity ◽  
Velocity Anomaly ◽  
Seismic Waveform ◽  
Igneous Provinces ◽  
Lithospheric Plates ◽  
Plate Reconstructions

<p>Hot plumes rising from Earth’s deep mantle are thought to form broad plume heads beneath lithospheric plates. In continents, mantle plumes cause uplift, rifting and volcanism, often dispersed over surprisingly broad areas. Using seismic waveform tomography, we image <span>a star-shaped, low-velocity anomaly centered at Afar and composed of three narrow branches: beneath East Africa, beneath the Gulf of Aden, and beneath the Red Sea and West Arabia, extending north to Levant. We interpret this anomaly as the seismic expression of </span>interconnected corridors of hot, partially molten rock beneath the East Africa-Arabia region. The corridors underlie areas of uplift, rifting and volcanism and accommodate an integral, active plume head. Eruption ages and plate reconstructions indicate that it developed south-to-north, and tomography shows it being fed by three deep upwellings beneath Kenya, Afar and Levant. <span>These results demonstrate the complex feedbacks between the continental-lithosphere heterogeneity and plume-head evolution. </span>Star-shaped plume heads sprawling within thin-lithosphere valleys can account for the enigmatic dispersed volcanism in large igneous provinces and are likely to be a basic mechanism of plume-continent interaction.</p>

Sign in / Sign up

Export Citation Format

Share Document