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1.
ABSTRACT The Bouvet Triple Junction (BTJ) region in the South Atlantic, where the African, South American and Antarctica plates meet, is affected by several topographic/melting anomalies. Causes of these anomalies were investigated through a study of mantle-derived serpentinized peridotites sampled from three sites in the BTJ region: (1) the Inner Corner High at the intersection of the America Antarctic Ridge (AAR) with the Conrad transform; (2) the south wall of the Bouvet transform (South West Indian Ridge, SWIR); and (3) the eastern Bouvet SWIR Transform Intersection. The degree of melting undergone by these rocks was estimated from relic mineral major- and trace-element composition. Geochemical profiles from residual peridotites and associated basalts show a > 1000-km-wide melting anomaly centred on the Bouvet and Spiess topographic anomalies. 相似文献
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New petrological and geochemical data were obtained for basalts recovered during cruise 24 of the R/V “Akademik Nikolay Strakhov” in 2006. These results significantly contributed to the understanding of the formation of tholeiitic magmatism at the northern
end of the Knipovich Ridge of the Polar Atlantic. Dredging was performed for the first time both in the rift valley and on
the flanks of the ridge. It showed that the conditions of magmatism have not changed since at least 10 Ma. The basalts correspond
to slightly enriched tholeiites, whose primary melts were derived at the shallowest levels and were enriched in Na and depleted
in Fe (Na-TOR type). The most enriched basalts are typical of the earlier stages of the opening and were found on the flanks
of the ridge in its northernmost part. Variations in the ratios of Sr, Nd, and Pb isotopes and lithophile elements allowed
us to conclude that the primary melts generated beneath the spreading zone of the Knipovich Ridge were modified by the addition
of the enriched component that was present both in the Neogene and Quaternary basalts of Spitsbergen Island. Compared with
the primitive mantle, the extruding magmas were characterized by positive Nb and Zr anomalies and a negative Th anomaly. The
formation of primary melts involved melting of the metasomatized depleted mantle reservoir that appeared during the early
stages of opening of the Norwegian-Greenland Basin and transformation of the paleo-Spitsbergen Fault into the Knipovich spreading
ridge, which was accompanied by magmatism in western Spitsbergen during its separation from the northern part of Greenland. 相似文献
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In 2008, during cruise 24 of the R/V Akademik Vavilov, much of our research work was focused on the central segment (Jaseur and Davis seamounts, Dogaressa Bank) of the Vitoria-Trindade
seamount chain (west of the Brazil basin) extending along 20.5° S. Work was conducted to survey the upper part of the sedimentary
cover and to perform subbottom profiling. The samples dredged on the seamount slopes are represented by volcanites and Fe-Mn
crusts. 相似文献
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Skolotnev S. G. Peyve A. A. Sanfilippo A. Ivanenko A. N. Ligi M. Veklich I. A. Petracchini L. Basch V. Kuleshov D. A. Ferrando C. Dobrolyubov V. N. Sani C. Shkittin N. A. Bickert M. Dokashenko S. A. Muccini F. Yakovenko E. S. Palmiotto C. Cuffaro M. 《Doklady Earth Sciences》2022,504(1):233-239
Doklady Earth Sciences - Geological and geophysical data collected during the 53rd cruise of the R/V Akademik Sergey Vavilov are presented. It is shown that the lateral distribution of the... 相似文献
9.
G. N. Savel’eva N. S. Bortnikov A. A. Peyve S. G. Skolotnev 《Geochemistry International》2006,44(11):1105-1120
The paper presents materials on the composition and texture of weakly serpentinized ultrabasic rocks from the western and
eastern walls of the Markov Deep (5°30.6′–5°32.4′N) in the rift valley of the Mid-Atlantic Ridge (MAR). The predominant harzburgites
with protogranular and porphyroclastic textures contain two major generations of minerals: the first generation composes the
bulk of the rocks and consists of Ol
89.8–90.4 + En
90.2–90.8 + Di
91.8 + Chr (Cr#32.3–36.6, Mg#67.2–70.0), while the second generation composes very thin branching veinlets and consists of PlAn
32–47 + Ol
74.3–77.1 + Opx
55.7–71.9 + Cpx
67.5 + Amph
53.7–74.2 + Ilm. The syndeformational olivine neoblasts in recrystallization zones are highly magnesian. The concentrations and covariations
of major elements in the harzburgites indicate that these rocks are depleted mantle residues (the high Mg# of minerals and
whole-rock samples and the low CaO, Al2O3, and TiO2 concentrations) that are significantly enriched in trace HFSE and REE (Zr, Hf, Y, LREE, and all REE). The mineralogy and
geochemistry of the harzburgites were formed by the interaction of mantle residues with hydrous, strongly fractionated melts
that impregnated them. The mineralogical composition of veinlets in the harzburgites and the mineralogical-geochemical characteristics
of the related plagiogranites and gabbronorites suggest that these plagiogranites were produced by melts residual after the
crystallization of gabbronorites. The modern characteristics of the harzburgites were shaped by the following processes: (i)
the partial melting of mantle material simultaneously with its subsolidus deformations, (ii) brittle-plastic deformations
associated with cataclastic flow and recrystallization, and (iii) melt percolation along zones of the maximum stress relief
and the interaction of this melt with the magnesian mantle residue.
Original Russian Text ? G.N. Savel’eva, N.S. Bortnikov, A.A. Peyve, S.G. Skolotnev, 2006, published in Geokhimiya, 2006, No.
11, pp. 1192–1208. 相似文献
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Skolotnev S. G. Sanfilippo A. Peyve A. A. Muccini F. Sokolov S. Yu. Sani C. Dobroliubova K. O. Ferrando C. Chamov N. P. Pertsev A. N. Gryaznova A. S. Sholukhov K. N. Bich A. S. 《Doklady Earth Sciences》2020,491(1):131-134
Doklady Earth Sciences - The geological and geophysical data acquired during cruise 45 of R/V Akademik Nikolaj Strakhov regarding the structure of the Doldrums megatransform system in the Central... 相似文献