Origin and evolution of water masses near the Antarctic continental margin: Evidence from H218O/H216O ratios in seawater

Author(s):  
Stanley S. Jacobs ◽  
Richard G. Fairbanks ◽  
Yoshio G. Horibe
2021 ◽  
pp. M55-2018-68 ◽  
Author(s):  
Philip T. Leat ◽  
Teal R. Riley

AbstractThe Antarctic Peninsula contains a record of continental-margin volcanism extending from Jurassic to Recent times. Subduction of the Pacific oceanic lithosphere beneath the continental margin developed after Late Jurassic volcanism in Alexander Island that was related to extension of the continental margin. Mesozoic ocean-floor basalts emplaced within the Alexander Island accretionary complex have compositions derived from Pacific mantle. The Antarctic Peninsula volcanic arc was active from about Early Cretaceous times until the Early Miocene. It was affected by hydrothermal alteration, and by regional and contact metamorphism generally of zeolite to prehnite–pumpellyite facies. Distinct geochemical groups recognized within the volcanic rocks suggest varied magma generation processes related to changes in subduction dynamics. The four groups are: calc-alkaline, high-Mg andesitic, adakitic and high-Zr, the last two being described in this arc for the first time. The dominant calc-alkaline group ranges from primitive mafic magmas to rhyolite, and from low- to high-K in composition, and was generated from a mantle wedge with variable depletion. The high-Mg and adakitic rocks indicate periods of melting of the subducting slab and variable equilibration of the melts with mantle. The high-Zr group is interpreted as peralkaline and may have been related to extension of the arc.


1997 ◽  
pp. 272-275
Author(s):  
R. D. Larter ◽  
P. F. Barker ◽  
C. J. Pudsey ◽  
L. E. Vanneste ◽  
A. P. Cunningham

2020 ◽  
Vol 48 (1) ◽  
pp. 233-258
Author(s):  
Meenakshi Wadhwa ◽  
Timothy J. McCoy ◽  
Devin L. Schrader

At present, meteorites collected in Antarctica dominate the total number of the world's known meteorites. We focus here on the scientific advances in cosmochemistry and planetary science that have been enabled by access to, and investigations of, these Antarctic meteorites. A meteorite recovered during one of the earliest field seasons of systematic searches, Elephant Moraine (EET) A79001, was identified as having originated on Mars based on the composition of gases released from shock melt pockets in this rock. Subsequently, the first lunar meteorite, Allan Hills (ALH) 81005, was also recovered from the Antarctic. Since then, many more meteorites belonging to these two classes of planetary meteorites, as well as other previously rare or unknown classes of meteorites (particularly primitive chondrites and achondrites), have been recovered from Antarctica. Studies of these samples are providing unique insights into the origin and evolution of the Solar System and planetary bodies. ▪  Antarctic meteorites dominate the inventory of the world's known meteorites and provide access to new types of planetary and asteroidal materials. ▪  The first meteorites recognized to be of lunar and martian origin were collected from Antarctica and provided unique constraints on the evolution of the Moon and Mars. ▪  Previously rare or unknown classes of meteorites have been recovered from Antarctica and provide new insights into the origin and evolution of the Solar System.


2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
V. D. Solovyov ◽  
V. G. Bakhmutov ◽  
I. N. Korchagin ◽  
S. P. Levashov ◽  
N. A. Yakymchuk ◽  
...  

The results of investigations in 2006–2010 for hydrocarbon and gas hydrates on the Antarctic Peninsula continental margin are given. In 2004 and 2006, the marine geoelectric researches by methods of forming a short-pulsed electromagnetic field (FSPEF) and vertical electric-resonance sounding (VERS) had been conducted in this region. The “deposit” type anomaly was mapped by FSPEF survey, and anomalous polarized layers of “hydrocarbon deposit” type were chosen by VERS sounding within this anomaly on Antarctic margin in the region of UAS “Academician Vernadsky.” Anomalous zones of “gas hydrate deposit” type were detected on the South Shetland margin due to the special technology of satellite data processing and interpretation using. These results confirm the high gas hydrates potential of the West Antarctica region. Some practical results of the experimental approbation of these original technologies for the “direct” prospecting and exploration of hydrocarbon (HC) and gas hydrates accumulations in different oil-and-gas bearing basins of Russia and Gulf of Mexico are proposed. The integration of satellite data processing and materials of FSPEF-VERS methods enable improving their efficiency for different geological and geophysical problems solving.


2020 ◽  
Vol 50 (2) ◽  
pp. 361-381 ◽  
Author(s):  
Esther Portela ◽  
Nicolas Kolodziejczyk ◽  
Christophe Maes ◽  
Virginie Thierry

AbstractUsing an Argo dataset and the ECCOv4 reanalysis, a volume budget was performed to address the main mechanisms driving the volume change of the interior water masses in the Southern Hemisphere oceans between 2006 and 2015. The subduction rates and the isopycnal and diapycnal water-mass transformation were estimated in a density–spiciness (σ–τ) framework. Spiciness, defined as thermohaline variations along isopycnals, was added to the potential density coordinates to discriminate between water masses spreading on isopycnal layers. The main positive volume trends were found to be associated with the Subantarctic Mode Waters (SAMW) in the South Pacific and South Indian Ocean basins, revealing a lightening of the upper waters in the Southern Hemisphere. The SAMW exhibits a two-layer density structure in which subduction and diapycnal transformation from the lower to the upper layers accounted for most of the upper-layer volume gain and lower-layer volume loss, respectively. The Antarctic Intermediate Waters, defined here between the 27.2 and 27.5 kg m−3 isopycnals, showed the strongest negative volume trends. This volume loss can be explained by their negative isopyncal transformation southward of the Antarctic Circumpolar Current into the fresher and colder Antarctic Winter Waters (AAWW) and northward into spicier tropical/subtropical Intermediate Waters. The AAWW is destroyed by obduction back into the mixed layer so that its net volume change remains nearly zero. The proposed mechanisms to explain the transformation within the Intermediate Waters are discussed in the context of Southern Ocean dynamics. The σ–τ decomposition provided new insight on the spatial and temporal water-mass variability and driving mechanisms over the last decade.


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