Rare elements and Nd and Sr isotopic composition in micronodules from the Brazil Basin, Atlantic Ocean

2017 ◽  
Vol 52 (2) ◽  
pp. 81-101 ◽  
Author(s):  
A. V. Dubinin ◽  
T. Yu. Uspenskaya ◽  
M. N. Rimskaya-Korsakova ◽  
T. P. Demidova
Keyword(s):  
Atlantic Ocean ◽  
Isotopic Composition ◽  
Brazil Basin ◽  
Rare Elements

scholarly journals ANOMALIES OF RARE ELEMENTS IN MANGANESE MICRONODULES FROM ETHMODISCUS OOZES IN THE BRAZIL BASIN OF THE ATLANTIC OCEAN

2020 ◽  
Vol 4(48) ◽  
pp. 64-84
Author(s):  
A.V. Dubinin ◽  
◽  
M.N. Rimskaya-Korsakova ◽  
T.P. Demidova ◽  
◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Biological Productivity ◽  
High Accumulation ◽  
Brazil Basin ◽  
Ce Anomaly ◽  
Rare Elements ◽  
Reducing Conditions ◽  
Oxidation Stage ◽  
Cerium Anomaly ◽  
Light Lanthanides

The composition of manganese micronodules from miopelagic clays and Ethmodiscus oozes of the central part of the Brazil Basin (station 1537, R/V Akademik Sergei Vavilov) is considered. Micronodules were recovered from >50 μm fraction of sediments from the depth intervals of 300 to 305, 405 to 410 and 442 to 452 cm below seafloor. The composition of micronodules was determined in separate size fractions of 50–100, 100–250 and 250–500 μm after dissolution in 0.5N NH2OH × HCl + 25% CH3COOH. The contents of Co, Ni, Cu, Ce, Pb, W, Th, and Bi in micronodules of miopеlagic clays were found to be higher than in micronodules from Ethmodiscus oozes. In the latter, the positive anomalies of Li, As, Mo, Cd, Tl, and U were revealed. The REE composition of micronodules in miopelagic clays is similar to the composition of hydrogenous crusts with a maximum in middle REE and a positive cerium anomaly. Micronodules of Ethmodiscus oozes have a positive Ce anomaly 2.8–3.8 and a deficiency of light lanthanides, similar to the composition of dissolved REEs in pore and bottom ocean waters. High accumulation of redox-sensitive elements in micronodules (As, Mo, V, and Cd) indicates an anaerobic stage in the post-sedimentary period in Ethmodiscus ooze caused by high biological productivity of waters. The formation of micronodules began during the period when the reducing conditions changed to oxidizing ones. Elements with low mobility (As, Mo, V, and Cd) accumulated in sediments and pore water during the anaerobic stage were then sorbed on Mn oxyhydroxides during the oxidation stage.

scholarly journals Importance of boundary layer mixing for the isotopic composition of surface vapor over the subtropical North Atlantic Ocean

2015 ◽  
Vol 120 (6) ◽  
pp. 2190-2209 ◽  
Author(s):  
Marion Benetti ◽  
Giovanni Aloisi ◽  
Gilles Reverdin ◽  
Camille Risi ◽  
Geneviève Sèze
Keyword(s):  
Boundary Layer ◽  
Atlantic Ocean ◽  
Isotopic Composition ◽  
North Atlantic ◽  
North Atlantic Ocean

scholarly journals Disentangling the effect of ocean temperatures and isotopic content on the oxygen – isotope signals in the North Atlantic Ocean during Heinrich Event 1 using a global climate model

2016 ◽  
Author(s):  
Marianne Bügelmayer-Blaschek ◽  
Didier M. Roche ◽  
Hans Renssen ◽  
Claire Waelbroeck
Keyword(s):  
Atlantic Ocean ◽  
Surface Temperature ◽  
Isotopic Composition ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Sea Surface ◽  
The North ◽  
Heinrich Event ◽  
The North Atlantic

Abstract. Heinrich events are intriguing episodes of enhanced iceberg discharge occurring during the last glacial period and are characterized by a steep increase in ice rafted debris (IRD) found in North Atlantic cores. Yet, their signal is not directly recognizable in the carbonate oxygen isotopic composition recorded in planktonic foraminifera, which depends on both the prevailing temperature and isotopic composition of seawater. Using the global isotope-enabled climate – iceberg model iLOVECLIM we performed three experiments to shed light on first, the impact of the duration of a Heinrich event-like iceberg forcing on the North Atlantic Ocean and second, the mechanisms behind the simulated δ18Ocalcite pattern. We applied an iceberg forcing of 0.2 Sv for 300, 600 and 900 years, respectively, and find a strong and non-linear response of the Atlantic Meridional Overturning Circulation (AMOC) to the duration of the Heinrich event in iLOVECLIM. Moreover, our results show that the timing of the first response to the iceberg forcing coincides between all the experiments in the various regions and happens within 300 years. Furthermore, the experiments display two main patterns in the δ18Ocalcite signal. On the one hand, the central and northeast North Atlantic regions display almost no response in δ18Ocalcite to the applied iceberg forcing since the changes in sea surface temperature and δ18Oseawater compensate each other or, if the forcing is applied long enough, a delayed response is seen. On the other hand, we show that in Baffin Bay, the Nordic Seas and the subtropical North Atlantic the change in δ18Oseawater exceeds the sea surface temperature signal and there the δ18Ocalcite pattern closely follows the δ18Oseawater signal and displays a continuous decrease over the length of the Heinrich event with the minimum value at the end of the iceberg release. The comparison of the model experiments with four marine sediment cores indicates that the experiment with an iceberg forcing of 0.2 Sv for 300 years yields the most reasonable results.

The uranium-isotopic composition of Saharan dust collected over the central Atlantic Ocean

2015 ◽  
Vol 17 ◽  
pp. 61-66 ◽  
Author(s):  
Sarah M. Aciego ◽  
Sarah M. Aarons ◽  
Kenneth W.W. Sims
Keyword(s):  
Atlantic Ocean ◽  
Isotopic Composition ◽  
Saharan Dust ◽  
Central Atlantic

scholarly journals Uranium-Lead Geochronology on Monacite of Granites of the Lypnyazka Massif and its Framing (Ingul Megablock of the Ukrainian Shield)

2021 ◽  
pp. 71-79
Author(s):  
L.M. Stepanyuk ◽  
◽  
S.I. Kurylo ◽  
V.O. Syomka ◽  
T.I. Dovbush ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Ukrainian Shield ◽  
Upper Crust ◽  
Isotopic Dating ◽  
Granite Massif ◽  
Rare Elements ◽  
The Village

The Lipnyazka massif is located in the Dobrovelychkivsky district of the Kirovohrad region, v. Lipnyazka and further south. Structurally, it is located within the Bratskyy Synclinorium of the Ingul megablock and coincides with the Mikhailovsky anticline. The main petrotype of the massif rocks are porphyry-like granites, often with a gneiss-like texture, aplito-pegmatoid, pegmatoid granites and pegmatites. The latter most often form secant vein bodies. Uranium-lead isotopic dating of granitoids of the Lipnyazka granite massif has been performed, with which a number of deposits and ore occurrences of rare elements, primarily lithium, are spatially and probably genetically connected. The age of porphyry-like granites (2032 ± 6 million years), which is the main petrotype of rocks distributed in the area of the village of Limestone and pegmatoid granites (2027 ± 1 million years), which cut porphyry-like in the form of vein bodies. Aplithoid framed granites (2046 ± 8 million years old), common in the area of the mouth of the Sukhyi Tashlyk River (Dobryanka village), are somewhat older. Based on the results of determining the isotopic composition of strontium in the accessory apatite of granites, a conclusion was made about the upper crust source of granites of the Lipnyazka massif (87Sr/86Sr – 0.730-0.785).

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