scholarly journals The first U-Pb (SHRIMP-II) evidence of the Franklin tectonic event at the western margin of the Siberian craton

2019 ◽  
Vol 486 (5) ◽  
pp. 567-571
Author(s):  
I. I. Likhanov ◽  
V. V. Reverdatto
Keyword(s):  
Siberian Craton ◽  
The Arctic ◽  
Spatial Proximity ◽  
Tectonic Event ◽  
Zircon Age ◽  
Western Margin ◽  
The North ◽  
Intraplate Magmatism ◽  
High Concentrations ◽  
Geochronological Evidence

Geochemical and isotope-geochronological evidence of the manifestation of Late Riphean intraplate magmatism within the Chernorechensky massif at the western margin of the Siberian craton were obtained. These rocks crystallized from high-temperature and anhydrous (water unsaturated) magmas with high concentrations of alkalis, iron, and, mostly incompatible elements, which is typical for anorogenic A-type granites in intraplate extension setting. Their U-Pb zircon age 723 ± 6 Ma can be correlated with the Franklin rift event widely manifested in the north of Laurentia, associated with the breakup of Rodinia. The synchronous successions and similar style of magmatic activity and concomitant rifting, as well as a similar sequence of tectonic-thermal events along the Arctic margin of Rodinia support the spatial proximity of Siberia and the North Atlantic cratons at this time as proposed for the paleogeographic reconstructions.

scholarly journals Elevated sources of cobalt in the Arctic Ocean

2020 ◽  
Author(s):  
Randelle M. Bundy ◽  
Alessandro Tagliabue ◽  
Nicholas J. Hawco ◽  
Peter L. Morton ◽  
Benjamin S. Twining ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
Deep Ocean ◽  
The Arctic ◽  
Biogeochemical Model ◽  
Shelf Area ◽  
The North ◽  
The Arctic Ocean ◽  
High Concentrations

Abstract. Cobalt (Co) is an important bioactive trace metal that can limit or co-limit phytoplankton growth in many regions of the ocean. Total dissolved and labile Co measurements in the Canadian sector of the Arctic Ocean during U.S. GEOTRACES Arctic expedition (GN01) and the Canadian International Polar Year-GEOTRACES expedition (GIPY14) revealed a dynamic biogeochemical cycle for Co in this basin. The major sources of Co in the Arctic were from shelf regions and rivers, with only minimal contributions from other freshwater sources (sea ice, snow) and aeolian deposition. The most striking feature was the extremely high concentrations of dissolved Co in the upper 100 m, with concentrations routinely exceeding 800 pmol L−1 over the shelf regions. This plume of high Co persisted throughout the Arctic basin and extended to the North Pole, where sources of Co shifted from primarily shelf-derived to riverine, as freshwater from Arctic rivers was entrained in the Transpolar Drift. Dissolved Co was also strongly organically-complexed in the Arctic, ranging from 70–100 % complexed in the surface and deep ocean, respectively. Deep water concentrations of dissolved Co were remarkably consistent throughout the basin (~ 55 pmol L−1), with concentrations reflecting those of deep Atlantic water and deep ocean scavenging of dissolved Co. A biogeochemical model of Co cycling was used to support the hypothesis that the majority of the high surface Co in the Arctic was emanating from the shelf. The model showed that the high concentrations of Co observed along the transect were due to the large shelf area of the Arctic, as well as dampened scavenging of Co by manganese (Mn)-oxidizing bacteria due to the lower temperatures. The majority of this scavenging appears to have occurred in the upper 200 m, with minimal additional scavenging below this depth. Preliminary evidence suggests that both dissolved and labile Co are increasing over time on the Arctic shelf, and the elevated surface concentrations of Co likely leads to a net flux of Co out of the Arctic, with implications for downstream biological uptake of Co in the North Atlantic and elevated Co in North Atlantic Deep Water. Understanding the current distributions of Co in the Arctic will be important for constraining changes to Co inputs resulting from regional intensification of freshwater fluxes from ice and permafrost melt in response to ongoing climate change.

scholarly journals Patterns and persistence of hydrologic carbon and nutrient export from collapsing upland permafrost

2015 ◽  
Vol 12 (12) ◽  
pp. 3725-3740 ◽  
Author(s):  
B. W. Abbott ◽  
J. B. Jones ◽  
S. E. Godsey ◽  
J. R. Larouche ◽  
W. B. Bowden
Keyword(s):  
Aquatic Ecosystems ◽  
Inorganic Nitrogen ◽  
The Arctic ◽  
Nutrient Export ◽  
Initial Pulse ◽  
Dissolved Carbon ◽  
Carbon And Nitrogen ◽  
The North ◽  
North Slope Of Alaska ◽  
High Concentrations

Abstract. As high latitudes warm, vast stocks of carbon and nitrogen stored in permafrost will become available for transport to aquatic ecosystems. While there is a growing understanding of the potential effects of permafrost collapse (thermokarst) on aquatic biogeochemical cycles, neither the spatial extent nor temporal duration of these effects is known. To test hypotheses concerning patterns and persistence of elemental export from upland thermokarst, we sampled hydrologic outflow from 83 thermokarst features in various stages of development across the North Slope of Alaska. We hypothesized that an initial pulse of carbon and nutrients would be followed by a period of elemental retention during feature recovery, and that the duration of these stages would depend on feature morphology. Thermokarst caused substantial increases in dissolved organic carbon and other solute concentrations with a particularly large impact on inorganic nitrogen. Magnitude and duration of thermokarst effects on water chemistry differed by feature type and secondarily by landscape age. Most solutes returned to undisturbed concentrations after feature stabilization, but elevated dissolved carbon, inorganic nitrogen, and sulfate concentrations persisted through stabilization for some feature types, suggesting that aquatic disturbance by thermokarst for these solutes is long-lived. Dissolved methane decreased by 90% for most feature types, potentially due to high concentrations of sulfate and inorganic nitrogen. Spatial patterns of carbon and nutrient export from thermokarst suggest that upland thermokarst may be a dominant linkage transferring carbon and nutrients from terrestrial to aquatic ecosystems as the Arctic warms.

scholarly journals Linkages between the Genesis and Resource Potential of Ferromanganese Deposits in the Atlantic, Pacific, and Arctic Oceans

Minerals ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 197 ◽  
Author(s):  
Amaya Menendez ◽  
Rachael James ◽  
Natalia Shulga ◽  
Doug Connelly ◽  
Steve Roberts
Keyword(s):  
The Arctic ◽  
Green Technologies ◽  
Resource Potential ◽  
The North ◽  
Environmental Controls ◽  
The Pacific ◽  
The Pacific Ocean ◽  
High Concentrations ◽  
Ferromanganese Deposits ◽  
New Generation

In addition to iron and manganese, deep sea ferromanganese deposits, including nodules and crusts, contain significant amounts of economically interesting metals, such as cobalt (Co), nickel (Ni), copper (Cu), and rare Earth elements and yttrium (REY). Some of these metals are essential in the development of emerging and new-generation green technologies. However, the resource potential of these deposits is variable, and likely related to environmental conditions that prevail as they form. To better assess the environmental controls on the resource potential of ferromanganese deposits, we have undertaken a detailed study of the chemical composition of ferromanganese nodules and one crust sample from different oceanic regions. Textural and chemical characteristics of nodules from the North Atlantic and a crust from the South Pacific suggest that they acquire metals from a hydrogenous source. These deposits are potentially an economically important source of Co and the REY. On the other hand, nodules from the Pacific Ocean represent a marginal resource of these metals, due to their relatively fast growth rate caused by diagenetic precipitation. By contrast, they have relatively high concentrations of Ni and Cu. A nodule from the Arctic Ocean is characterised by the presence of significant quantities of detrital silicate material, which significantly reduces their metal resource.

Some Physical and Chemical Characteristics of Arctic Fresh Waters In Alaska and Northwestern Canada

1968 ◽  
Vol 25 (12) ◽  
pp. 2575-2587 ◽  
Author(s):  
J. Kalff
Keyword(s):  
Electrical Conductance ◽  
Correlation Coefficients ◽  
Total Alkalinity ◽  
The Arctic ◽  
Chemical Characteristics ◽  
Mean Values ◽  
Manganese Zinc ◽  
The North ◽  
Arctic Alaska ◽  
High Concentrations

Fifty-eight Arctic Alaskan lakes and rivers and two ponds as well as a few northwestern Arctic Canadian waters were analyzed for two or more physical or chemical characteristics. The waters sampled were nearly all of the bicarbonate type and ranged from very soft to hard. The Alaskan and mainland Canadian lakes contain levels of many ions similar to those of some low electrolyte lake waters previously reported for the north temperate zone. The characteristics measured, with the mean values for the Alaskan waters in brackets when 20 or more lakes or rivers were sampled, were: calcium (17.2 mg/liter), magnesium (2.1 mg/liter) total iron, total alkalinity (50.3 mg/liter), sulfate (4.9 mg/liter), chloride (3.8 mg/liter), nitrate, phosphate, electrical conductance (116 μmho), pH (7.7), and water color (24 Pt units). One of the ponds, analyzed for 18 trace metals, indicated relatively high concentrations of iron manganese, zinc, and copper. Correlation coefficients (r at P < 0.5) between various characteristics were: electrical conductance and total alkalinity, 0.98; electrical conductance and calcium, 0.97; electrical conductance and magnesium, 0.42; calcium and magnesium, 0.46; and pH and total alkalinity, 0.91. On the Coastal Plain of Arctic Alaska the total electrolyte content of lakes lying within 25–50 km from the Arctic Ocean was noticeably raised by chloride additions.

scholarly journals Elevated sources of cobalt in the Arctic Ocean

2020 ◽  
Vol 17 (19) ◽  
pp. 4745-4767
Author(s):  
Randelle M. Bundy ◽  
Alessandro Tagliabue ◽  
Nicholas J. Hawco ◽  
Peter L. Morton ◽  
Benjamin S. Twining ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
Deep Ocean ◽  
The Arctic ◽  
Biogeochemical Model ◽  
Shelf Area ◽  
The North ◽  
The Arctic Ocean ◽  
High Concentrations

Abstract. Cobalt (Co) is an important bioactive trace metal that is the metal cofactor in cobalamin (vitamin B12) which can limit or co-limit phytoplankton growth in many regions of the ocean. Total dissolved and labile Co measurements in the Canadian sector of the Arctic Ocean during the U.S. GEOTRACES Arctic expedition (GN01) and the Canadian International Polar Year GEOTRACES expedition (GIPY14) revealed a dynamic biogeochemical cycle for Co in this basin. The major sources of Co in the Arctic were from shelf regions and rivers, with only minimal contributions from other freshwater sources (sea ice, snow) and eolian deposition. The most striking feature was the extremely high concentrations of dissolved Co in the upper 100 m, with concentrations routinely exceeding 800 pmol L−1 over the shelf regions. This plume of high Co persisted throughout the Arctic basin and extended to the North Pole, where sources of Co shifted from primarily shelf-derived to riverine, as freshwater from Arctic rivers was entrained in the Transpolar Drift. Dissolved Co was also strongly organically complexed in the Arctic, ranging from 70 % to 100 % complexed in the surface and deep ocean, respectively. Deep-water concentrations of dissolved Co were remarkably consistent throughout the basin (∼55 pmol L−1), with concentrations reflecting those of deep Atlantic water and deep-ocean scavenging of dissolved Co. A biogeochemical model of Co cycling was used to support the hypothesis that the majority of the high surface Co in the Arctic was emanating from the shelf. The model showed that the high concentrations of Co observed were due to the large shelf area of the Arctic, as well as to dampened scavenging of Co by manganese-oxidizing (Mn-oxidizing) bacteria due to the lower temperatures. The majority of this scavenging appears to have occurred in the upper 200 m, with minimal additional scavenging below this depth. Evidence suggests that both dissolved Co (dCo) and labile Co (LCo) are increasing over time on the Arctic shelf, and these limited temporal results are consistent with other tracers in the Arctic. These elevated surface concentrations of Co likely lead to a net flux of Co out of the Arctic, with implications for downstream biological uptake of Co in the North Atlantic and elevated Co in North Atlantic Deep Water. Understanding the current distributions of Co in the Arctic will be important for constraining changes to Co inputs resulting from regional intensification of freshwater fluxes from ice and permafrost melt in response to ongoing climate change.

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