极地研究

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INSPIRATION FROM STUDY OF ANTARCTIC METEORITES I: PETROGRAPHIC AND COMPOSITIONAL EVIDENCES FOR EARLY CONTINUOUS CHEMICAL FRACTIONATION OF THE SOLAR NEBULA

Wang Daode, Lin Yangting

1992, 3 (1-English): 1-16.

摘要 ( 982 )

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Bulk concentrations of Ir, Os, Co and other siderophile elements of metal phase in chondrites increase significantly with degree of oxidation, which together with Co-content of kamacite and Fa-content of olivine, reveal a continuous variation of redox in chondrites. Intermediate groups of E/H, H/L, L/LL, and LL/C, lying between E and H, H and L, L and LL, LL and C, respectively, were proposed based on Co content in kamacite, Fa value of olivine, Fs value of low-Ca pyroxene, bulk concentrations of Ir, Os and Co of metal phase and other taxonomic parameters. The discovery of intermediate groups increases the number of chemical groups of chondrites from 9 to 13. Both variation of redox in chondrites and presence of the intermediate groups of chondrites suggest a continuous chemical fractionation in the primordial solar nebula.

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A NONMARINE LATE CRETACEOUS DEPOSITIONAL UNIT ON KING GEORGE ISLAND, WEST ANTARCTICA

Shen Yanbin

1992, 3 (1-English): 17-24.

摘要 ( 1106 )

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A new lithostratigraphic unit - Half Three Point Formation is determined on an inlet (62°13'40"S, 58°59'01"W) near Half Three Point of Fildes Peninsula of King George Island, South Shetland Islands. This formation consists of volcanic breccia, sediment- tuff, tuffaceous siltstones and mudstones about 5. 5m thick. The Palynomorph assemblage is of Late Cretaceous age (Campanian - Maastrichtian). Isotopic age of the tuffites by Rb -Sr whole rock method is 71.30±0. 3 Ma. The calcite of sand -sized tuffites formed by calcitization during early diagenesis has very light δ18C value of - 26. 24%,PDB, and δ13C value of -5. 130 to 5. 631%, PDB. It suggests that the calcitization is related to thermal freshwater originally. The tuffaceous mudstone contains lower B content of 48. 4 ppm, corresponding to that of lacustrine mudstones. Low87 Sr/86 Sr ratio (0. 703189 - 0. 703320) indicates the tuffites of continental origin. Therefore, the formation may represent a lacustrine deposit under low energy and reducing environment. This is only known to define the late Late Cretaceous lacustrine sediments in Antarctica.

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SIMULATION OF KATABATIC WINDS AT MIZUHO STATION, ANTARCTICA

Ma Yimin

1992, 3 (1-English): 25-30.

摘要 ( 903 )

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A new simulation method for solving dynamic equations for stationary katabatic wind is suggested by the assumption that the turbulent exchange coefficient is a function of height and the effect of the cold sloping surface is a multinomial function of height. Calculated wind profiles agree with observational data at Mizuho Station, Antarctica.

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NATURAL PRODUCTIVITY OF ACRYLIC ACID AND DIMETHYL SULPHIDE DURING A SUMMER BLOOM OF PHAEOCYSTIS POUCHETII IN ANTARCTIC COASTAL WATER

Yang Hefu, Andrew R Mctaggart, Andrew Davidson, Harry Burton

1992, 3 (1-English): 31-39.

摘要 ( 1209 )

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Water samples were collected over P. ponchetii bloom period beginning in November 1988, in 15m water column, from 10km offshore of Davis Station, Vestfold Hill, Antarctica. The concentrations of acrylic acid and dimethyl sulphide (DMS), which are toxic compounds in the water samples, were determined by HPLC and GC. The result shows that the concentration of acrylic acid varies in 0. 001 - 0. 510μmol?L-1 and the concentration of DMS in 0. 003-0. 588 μmol?L-1 during P. pouchetii bloom. Both the increased since late December 1988 and reached the highest concentration in early January 1989, then they decreased rapidly and returned to lower level from middle January to February in agreement with variation in cell number of the unicell alga P. pouchetii. The correlation coefficients between acrylic acid and P. pouchetii and between DMS and P. pouchetii are all 0. 998. It is undoubted that P. pouchetii produced acrylic acid and DMS. The highest productivity of acrylic acid and DMS were 9. 76X10-8 μmol?cell-1 and 13. 09 ×10-8 μmol?cell-1, respectively, during P. pouchelii bloom. A cellular product, dimethylsulphonium propionate (DMSP), is decomposed into acrylic acid and DMS, and the formation of DMSP is probably from methionine which could be utilized by P. pouchelii.

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PALEOMAGNETISM OF THE LATE CRETACEOUS AND EARLY TERTIARY ROCKS FROM FILDES PENINSULA,WEST ANTARCTICA, AND ITS GEOTECTONIC SIGNIFICANCE

Liu Chun, Zhu Rixiang, Zheng Xiangshen, Liu Xiaohan, Jin Zengxin, Feng Yu

1992, 3 (1-English): 40-49.

摘要 ( 1306 )

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The paleomagnetis m of 109 oriented samples collected from drill cores through 5 rock units of Late Cretaceous and Early Tertiary on Fildes Peninsula were systematically studied. According to the study, the paleomagnetic pole position of this area is different from the position of Australia during the 55-45 Ma period. This means that when the break-up of the Gondwanaland at 55-45 Ma ago, Australia was separated from the Gondwanaland, drifting southward 20°-30°Lat. and rotating 70°-80°westward and then gradually arriving at recent position. The paleolatitudinal data indicate that it is not impossible that the area studied was covered with land glacier at that time. The apparent polar wander path of Antarctica through the geological time are also roughly worked out.

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REMOBILIZATION AND ACCUMULATION OF IODINE IN MARINE SEDIMENTS, WESTERN ANTARCTIC OCEAN

Cheng Xiaohao, Xia Weiping, Zhang Haisheng

1992, 3 (1-English): 50-59.

摘要 ( 1125 )

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Remobilization and accumulation mechanisms of iodine in marine sediments, which are divided into several geochemical environment, are studied. The result shows that iodine is characteristically rich in organic fractions of the sediments on the bottom of bay and pelagic sediments. However, it may be associated with oxyhydroxide and adsorptive phase in a highter percentage at the continental shelf and hemipelagic sediments. The environmental characteristics of remobilization of iodine in surficial sediments are similar to that of iron , that is, it is remobilized on anoxic conditions and converted into solid phases when it is in oxic environments, though the iodine does not act as the electron acceptor. The processes of adsorption and oxidation are responsible for the value of It/Corg in excess of that of planktonic materials other than the organic fraction in surficial sediments. It is a comprehensive effect of organism decomposition, oxyhydroxide reduction, paniculate adsorption and pore water diffusion on decrease of ratio of iodine to organic carbon with increasing depth in sedimentary column. The diffusive and depositional fluxes of iodine are of the same magnitude, which could be the cause for the poor iodine contents in sedimentary rocks. Based on the calculation and discussion, a new model for the remobilization and accumulation of iodine in marine sediments is set up.

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ISOTOPIC AGE AND STRATIGRAPHYCAL CORRELATION OF VOLCANIC ROCKS IN FINDES PENINSULA, KING GEORGE ISLAND

Zhu Ming, E Molan, Liu Xiaohan, Zheng Xiangshen

1992, 3 (1-English): 60-70.

摘要 ( 1167 )

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The ages of volcanic rocks from the Fildes Peninsula of King George Island, West Antarctica, have been determined with K-Ar, ~(39)Ar-~(40)Ar, Rb-Sr methods by the authors, The results show that: a. The volcanism on the Fildes Peninsula has been from later Paleocene to early Middle Miocene; b. The formation time of the volcanic rocks of Jasper Hill Member belongs to later Paleocene becarse of the isotope age being 54Ma and 55Ma determined with Rb-Sr and ~(39)Ar-~(40)Ar methods, respectively, c. The volcanic rocks of Agate Beach Member are the products of the volcanic activities during Early Eocene according to K-Ar isochron (45-50Ma); d. The geological age of fossil Hill member is about Middle Eocene to Early Oligocene; e. the formation time of Block Hill member is probably early Middle Miocene. These data combining with the geological adn palaeontological evidences strongly support to best understand the stratigraphical correlation adn reveal the volcanism in studied area.

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