The age and origin of the garnet amphibolite underlying the Thetford Mines ophiolite, Quebec

1981 ◽  
Vol 18 (3) ◽  
pp. 469-486 ◽  
Author(s):  
David Clague ◽  
Jason Rubin ◽  
Russell Brackett
Keyword(s):  
Atlantic Ocean ◽  
Initial Phase ◽  
Tholeiitic Basalt ◽  
Garnet Amphibolite ◽  
Low Concentrations ◽  
Mineral Compositions ◽  
Midocean Ridge ◽  
North And South ◽  
Low K ◽  
Metamorphic Unit

The Thetford Mines ophiolite in southern Quebec is partially underlain by an 800 m thick amphibolite aureole. Rocks in the metamorphic unit grade inward towards the base of the ophiolite from chlorite–muscovite schist, epidote amphibolite, and garnet amphibolite to clinopyroxene-bearing garnet amphibolite closest to the fault contact with the basal tectonized peridotite unit of the ophiolite. The polydeformed metamorphic unit pinches out north and south of Belmina Ridge and is discordant with the overlying tectonized peridotite. Analyses of nine samples show a range of compositions, but the low K2O, P2O5, Rb, Zr, and Sr suggest that the amphibolite protolith was tholeiitic basalt, probably midocean ridge tholeiite.Microprobe mineral compositions determined for coexisting clinopyroxene–garnet–amphibole and garnet–amphibole suggest that amphibolites near the peridotite contact equilibrated at about 850 °C and that the temperatures decreased to about 380 °C 700 m from the contact. Geobarometers based on coexisting clinopyroxene and garnet, and Al and Na partitioning in amphibole yield variable results, but suggest that the pressure during formation of the amphibolite was probably greater than 5 kbar (5 × 105 kPa).Eight conventional K–Ar ages average 488 ± 11 Ma but show some scatter due to inaccuracy of K2O determinations at very low concentrations and, in some samples, possible inherited argon. A single 40Ar/39Ar incremental heating experiment gives concordant plateau and isochron ages of 491 ± 4 and 494 ± 4 Ma, respectively. The best weighted age of 491 ± 3 Ma probably dates the decoupling of the Thetford Mines ophiolite during the initial phase of closing of the Proto-Atlantic Ocean.

The geochemical nature of the igneous rocks of the Sharbot Lake domain, Central Metasedimentary Belt, Ontario

2001 ◽  
Vol 38 (7) ◽  
pp. 1037-1057 ◽  
Author(s):  
T E Smith ◽  
M J Harris ◽  
C H Huang ◽  
P E Holm
Keyword(s):  
Trace Element ◽  
Volcanic Rocks ◽  
Tholeiitic Basalt ◽  
Igneous Rocks ◽  
Igneous Complex ◽  
Low Concentrations ◽  
Granitoid Rocks ◽  
High Concentrations ◽  
Back Arc ◽  
Low K

Two bimodal mafic-silicic suites of igneous rocks, the Sharbot Lake volcanic rocks and the Lavant Igneous Complex, are identified geochemically in the Sharbot Lake domain of the Central Metasedimentary Belt in Ontario, and their genesis and thermotectonic environment are evaluated. The Sharbot Lake volcanic rocks comprise a series of basalts characterized by light rare-earth element (LREE) depletion and relatively high concentrations of Σ Fe2O3, TiO2, MnO, V, and Y, together with rhyolites and silicic pyroclastic rocks. They are intruded by rocks of the Lavant Igneous Complex, which comprises tholeiitic gabbros characterized by LREE enrichment and low concentrations of Σ Fe2O3, TiO2, MnO, V, and Y, and granitoid rocks. The trace element signatures of the mafic rocks of the Sharbot Lake volcanic sequences are most like those of back-arc tholeiitic basalts, and those of the Lavant Igneous Complex are comparable to those of low-K tholeiitic basalt suites. The trace element signatures of the silicic rocks associated with both suites are typical of those formed by crustal melting. Volcanic sequences with trace-element signatures very similar to those of the Sharbot Lake suites have been previously described in the Belmont and Grimsthorpe domains of the Central Metasedimentary Belt, suggesting that the three domains all belong to the Bancroft – Elzevir – Mazinaw – Sharbot Lake superterrane. The lithological, structural, and igneous characteristics of this superterrane suggest that it represents part of a complex back-arc basin underlain by areas of rifted and attenuated continental crust and oceanic crust.

Transatlantic Radicalism

2021 ◽  
Keyword(s):  
South America ◽  
Atlantic Ocean ◽  
Case Studies ◽  
Individual Case ◽  
History Of ◽  
Late Nineteenth ◽  
Organizational Ties ◽  
North And South America ◽  
North And South ◽  
Political Radicalism

The Atlantic Ocean not only connected North and South America with Europe through trade but also provided the means for an exchange of knowledge and ideas, including political radicalism. Socialists and anarchists would use this “radical ocean” to escape state prosecution in their home countries and establish radical milieus abroad. However, this was often a rather unorganized development and therefore the connections that existed were quite diverse. The movement of individuals led to the establishment of organizational ties and the import and exchange of political publications between Europe and the Americas. The main aim of this book is to show how the transatlantic networks of political radicalism evolved with regard to socialist and anarchist milieus and in particular to look at the actors within the relevant processes—topics that have so far been neglected in the major histories of transnational political radicalism of the late nineteenth and early twentieth centuries. Individual case studies are examined within a wider context to show how networks were actually created, how they functioned and their impact on the broader history of the radical Atlantic.

Microplastics pollution in North and South Atlantic Ocean surface waters 

2021 ◽  
Author(s):  
Svetlana Pakhomova ◽  
Evgeny Yakushev
Keyword(s):  
Atlantic Ocean ◽  
Barents Sea ◽  
Environmental Concern ◽  
World Ocean ◽  
Basic Research ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
Metal Mesh ◽  
North And South ◽  
Polymer Type

<p>Contamination of the World Ocean by synthetic non-biodegradable material has become a high profile environmental concern. Standardized sampling methods and methods of plastic identification should be developed so that results can be fed into international monitoring strategies to map plastic distribution worldwide. Here we present results of studies carried out on a transect between Tromsø and Svalbard and from Montevideo to Antarctica performed with the same sampling procedure onboard Norwegian and Russian ships in 08.2019 and 01.2020 respectively. Microplastic sampling<strong> </strong>was carried out using a filtering system. Water passed through the system and SPM was collected on a metal mesh screens. All potential plastic particles and fibers were checked for polymeric identification using a PerkinElmer Spotlight ATR-FTIR. The level of confirmed microplastics ranged from 0 to 1.9 items/m<sup>3 </sup>(0.7 items/m<sup>3 </sup>in average) on a transect Tromsø-Svalbard and from 0 to 2.5 items/m<sup>3 </sup>(0.4 items/m<sup>3 </sup>in average) on Montevideo-Antarctica transect. Both data sets were represented by 40% of fragments and 60% of fibers. Polyester was found as the main polymer type for both transects, 46% of microplastics. Other found polymer types were different in the North and South Atlantic Ocean waters. Nylon (polyamide) was the next most common polymer type in South Atlantic which was not found in Northern part. Difference was also observed in higher number of stations without any microplastics in South Atlantic.</p><p>This work was partly funded by the Norwegian Ministry of Climate and Environment project RUS-19/0001 “Establish regional capacity to measure and model the distribution and input of microplastics to the Barents Sea from rivers and currents (ESCIMO)” and the Russian Foundation for Basic Research, research projects 19-55-80004.</p>

scholarly journals Distribution of haploniscids (Isopoda, Asellota, Haploniscidae) in Icelandic waters, with description of Haploniscus astraphes n. sp. from the Iceland basin and the Southeast Atlantic Ocean

Zootaxa ◽  
2017 ◽  
Vol 4231 (3) ◽  
pp. 301 ◽  
Author(s):  
WIEBKE BRÖKELAND ◽  
JÖRUNDUR SVAVARSSON
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Strongly Convex ◽  
The North ◽  
Iceland Basin ◽  
Denmark Strait ◽  
Depth Ranges ◽  
North And South ◽  
Icelandic Waters

Ten species of Haploniscidae Hansen, 1916 were sampled in Icelandic waters during expeditions in the framework of the BIOICE project. Nine of these were known from the North Atlantic Ocean, i.e. Haploniscus aduncus Lincoln, 1985, H. ampliatus Lincoln, 1985, Haploniscus angustus Lincoln, 1985, H. bicuspis (Sars, 1877), H. foresti Chardy, 1974, H. hamatus Lincoln, 1985, H. spinifer Hansen, 1916, Antennuloniscus simplex Lincoln, 1985 and Chauliodoniscus armadilloides (Hansen, 1916). All but H. bicuspis and H. angustus were restricted to the Atlantic Ocean south of the Greenland-Iceland-Faeroe Ridge (GIF Ridge), while H. bicuspis occurred at considerable depth ranges both north and south of the GIF Ridge. A new species, Haploniscus astraphes n. sp., is described based on material from the Denmark Strait, North Atlantic and the Guinea Basin, South Atlantic. H. astraphes n. sp. belongs to a group of Haploniscus species closely related to the genus Antennuloniscus and shares several characters with species from that genus, especially the spine row on pleopod 1, the stout sensory seta on the carpus of pereopod 7 and characters of the antennae. H. astraphes n. sp. is characterized by a rectangular body shape, the straight frontal margin of the head and the strongly convex posterior margin of the pleotelson. 

Multiple Sources for Sea-Rafted Loisels Pumice, New Zealand

1998 ◽  
Vol 49 (3) ◽  
pp. 271-279 ◽  
Author(s):  
Phil Shane ◽  
Paul Froggatt ◽  
Ian Smith ◽  
Murray Gregory
Keyword(s):  
New Zealand ◽  
Late Holocene ◽  
Ocean Currents ◽  
Multiple Sources ◽  
Tasman Sea ◽  
First Arrival ◽  
Mineral Compositions ◽  
Coastal Deposits ◽  
Low K ◽  
Westward Drift

Sea-rafted Loisels Pumice is one of the few stratigraphic markers used to correlate late Holocene coastal deposits in New Zealand. Along with underlying sea-rafted products of the local Taupo eruption of ca. 1800 yr B.P., these events have been used to bracket the first arrival of humans at New Zealand. Loisels Pumice is dacitic to rhyolitic (SiO2 63–78 wt%) in composition, but individual clasts are homogeneous (SiO2 range ± 1 wt%). Characteristics include very low K2O (0.5–1.75 wt%) and Rb (<25 ppm) and a mineralogy dominated by calcic and mafic xenocrysts. Similar features are shared by pumices of the Tonga–Kermadec arc, suggesting a common tholeiitic oceanic source. Interclast diversity of Loisels Pumice suggests that it is the product of several eruptive events from different volcanoes. The differences in glass and mineral compositions found at various sites can be explained if the deposits are from different events. A multisource origin can also partially explain the discrepancy in reported 14C ages (ca. 1500–600 yr B.P.) from different localities. Therefore, the value of Loisels Pumice as a stratigraphic marker is questionable, and it does not constrain the arrival of humans. The predominant westward drift of historic Tonga–Kermadec arc pumices and prevailing ocean currents suggest a long anticlockwise semicircular transport route into the Tasman Sea before sea-rafted pumice arrival in New Zealand. The diversity of the pumices indicates that silicic eruptions frequently occur from the predominantly basic oceanic volcanoes.

Levels of polychlorinated biphenyls in the lower troposphere of the North- and South-Atlantic Ocean

1994 ◽  
Vol 348 (3) ◽  
pp. 226-239 ◽  
Author(s):  
J�rn Schreitm�ller ◽  
Karlheinz Ballschmiter
Keyword(s):  
Atlantic Ocean ◽  
Polychlorinated Biphenyls ◽  
Lower Troposphere ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The North ◽  
North And South

scholarly journals Ontogenetic foraging activity and feeding selectivity of the Brazilian endemic parrotfish Scarus zelindae

2016 ◽  
Author(s):  
Pedro H Pereira ◽  
Marcus Santos ◽  
Daniel L Lippi ◽  
Pedro Silva
Keyword(s):  
Atlantic Ocean ◽  
Initial Phase ◽  
Negative Relationship ◽  
Terminal Phase ◽  
Ecological Knowledge ◽  
Foraging Activity ◽  
Feeding Rates ◽  
Feeding Selectivity ◽  
Western Atlantic ◽  
Southwestern Atlantic Ocean

Parrotfish are fundamental species in controlling algae phase-shifts and ensuring the resilience of coral reefs. Nevertheless, little is known on their ecological role in the South-western Atlantic Ocean. The present study analysed the ontogenetic foraging activity and feeding selectivity of the Brazilian endemic parrotfish Scarus zelindae using behavioural observation and benthic composition analyses. We found a significant negative relationship between fish size and feeding rates for S. zelindae individuals. Thus, terminal phase individuals forage with lower feeding rates compared to juveniles and initial phase individuals. The highest relative foraging frequency of S. zelindae was on epilithic algae matrix (EAM) with similar values for juveniles (86.6%), initial phase (88.1%) and terminal phase (88.6%) individuals. The second preferred benthos for juveniles was sponge (11.6%) compared with initial (4.5%) and terminal life phases (1.3%). Different life phases of S. zelindae foraged on different benthos according to their availability. Based on Ivlev's electivity index, juveniles selected EAM and sponge, while initial phase and terminal phase individuals only selected EAM. Our findings demonstrate that the foraging frequency of the endemic parrotfish S. zelindae is reduced according to body size and that there is a slight ontogenetic change in feeding selectivity. Therefore, ecological knowledge of ontogenetic variations on resource use is critical for the remaining parrotfish populations which have been dramatically reduced in the Southwestern Atlantic Ocean.

scholarly journals Interpretation and Reconstruction of Depositional Environment and Petroleum Source Rock Using Outcrop Gamma-ray Log Spectrometry From the Huai Hin Lat Formation, Thailand

2021 ◽  
Vol 9 ◽  
Author(s):  
Chawisa Phujareanchaiwon ◽  
Piyaphong Chenrai ◽  
Kasira Laitrakull
Keyword(s):  
Depositional Environment ◽  
Gamma Ray ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Turbidity Currents ◽  
Stratigraphic Framework ◽  
Facies Associations ◽  
Mineral Compositions ◽  
Gamma Ray Log ◽  
Low K

Gamma ray logs are most useful in identifying subsurface lithology and interpreting depositional environments. This study highlights the use of outcrop gamma-ray logs along with outcrop observations and total organic carbon (TOC) analysis to provide the stratigraphic framework of the organic-rich rocks of Huai Hin Lat Formation in central Thailand. The study reveals five sedimentary facies including (1) structureless sandstone, (2) structured sandstone, (3) interbedded sandstone and siltstone, (4) interbedded mudstone and siltstone and (5) calcareous mudstone. These facies can be grouped into two facies associations; mudstone-dominated and sandstone-dominated facies associations. The depositional environment was interpreted as lacustrine basin-fill subdivided into deep lacustrine environment and sublacustrine fan associated with the turbidity currents. The total gamma-log characteristics are closely related to the lithologies controlled primarily by clay mineral compositions. Whist, the use of spectral gamma-ray can reveal more details on depositional environments and conditions. In this study, U concentrations is proven to be useful in highlighting organic-rich rocks in low K and Th concentration successions due to its ability to be fixed in clay minerals and organic materials under an anoxic condition. Thus, the U spectral gamma ray is suggested to combine with conventional gamma ray log for depositional environment and recognition of organic-rich rocks.

Temperature-induced functional deocclusion of thiols inhibitory for sheep erythrocyte K-Cl cotransport

1995 ◽  
Vol 269 (5) ◽  
pp. C1167-C1175 ◽  
Author(s):  
P. K. Lauf ◽  
N. C. Adragna
Keyword(s):  
Kinase Inhibitor ◽  
Sheep Erythrocyte ◽  
Inhibitory Effect ◽  
Temperature Treatment ◽  
Cell Swelling ◽  
Thiol Groups ◽  
Subsequent Removal ◽  
Low Concentrations ◽  
High Concentrations ◽  
Low K

In low-K sheep erythrocytes, K-Cl cotransport is activated by treatment with low concentrations of thiol reagents and by other interventions such as lowering of cellular free cytosolic Mg, hyposmotic cell swelling, the kinase inhibitor staurosporine, and hydroxylamine. High concentrations of N-ethylmaleimide or methylmethane thiolsulfonate reverse the activation through thiol groups and, as shown here, also the stimulation by non-thiol manipulations. The overriding inhibitory sites functionally associated with and different from those of the activating thiols (SHa) were further distinguished by temperature. Treatment with N-ethylmaleimide and its subsequent removal by dithiothreitol, both at 0 degrees C, prevented the inhibitory effect at 37 degrees C and thus the chemical modification of inhibitory thiols (SHi). Whereas stimulation through SHa closely followed the loss of glutathione, inhibition through SHi occurred only in glutathione-depleted cells. The reversal of K-Cl cotransport stimulation by all hitherto known interventions, which is strongest in metabolically depleted cells, suggests that the low temperature-protected SHi constitute crucial sites that, close to the transporter itself or at the cytoskeletal level, become functionally deoccluded upon temperature elevation.

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