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The source rock from which the sillimanite gneisses derive mainly was the biotite plagioclase gneiss in the Larsemann Hills. It is the deformation metamorphism process under special pressure and temperature condition, not the original rock compositions, that controls the presence of sillimanite. To a great degree, the sillimanite gneiss was the mixture of the detaining materials of the migrating felsic melt from the bt-plagioclase gneiss that underwent partial melting and the relics when the melt was removed. In sillimanite zation the original rock had been changed substantially in chemical composition. The related metamorphism process severely deviated from the isochemical series, the process was of, therefore, an open system. In addition, the Al2O3 contents of the original rock was an important, but not critical factor for the formation of sillimanite, i. e., the sillmanite-bearing rock need not be of aluminum rich in composition, and vise contrarily, the aluminum rock may not produce sillimanite. The authors of the present paper postulate that the source rock from which the aluminum rich rock derives need not be of aluminum rich, but sillimanite zation is generally the A12O3 increasing process. The aluminum rich sediments such as clay or shale need not correspond directly to sillinanite-rich gneisses. No argillaceous rock present equals to sillimanite-rich gneiss in chemical composition. The protoliths to the sillimanite gneisses from the Larsemann Hills, east Antarctica, and their adjacent area may be pelite, shale greywacke, sub-greywacke, quartz sandstone and quartz-tourmalinite. If correct, the conclusion will be of significant implication for the determination of the sillimanite gneiss formation process and the reconstruction of the protolith setting
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The first study of erratic boulder exposure ages in the Grove Mountains, interior Antarctica, indicates the two erratic boulders (060131 - 1 and 060131 - 2, col - lected from a typical nunataks, Zakharoff Ridge in the Grove Mountains) have 10Be minimum exposure ages of 1.24 ± 0.11 Ma, 1.37 ± 0.12 Ma, and 26 Al ages of 0.90 ± 0.12 Ma, 0.44 ± 0.04 Ma, respectively. Meanwhile, another erratic boulder sample 060131 - 4, coming from vicinal ice surface, has 10 Be and 26 Al minimum expo-sure ages of 0.47 ± 0.3 Ma and 0.44 ± 0.04 Ma, respectively. The exposure ages of the three erratic boulders are nearly similar to the bedrocks with the similar elevation. Thus, using the technique of
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During the 22nd Chinese Antarctic Research Expedition (CHINARE - 22, 2005/06), the atmospheric gas samples near the surface were taken on the Millor Peninsula and adjacent areas, east Antarctica, using Tedlar gas bags. The methane (CH4) concentration and δ13 C-CH4 in those samples were analyzed in the laboratory. The average value of atmospheric CH4 concentration on this peninsula was (1.87 ± 0.12) × 10-6, slightly higher than the global average CH4 concentration. The summer time variation of CH4 concentrations showed a large fluctuation, corresponding to the variation of air temperatures. The average δ13 C-CH4 was (- 38.26 ± 0.52)‰. CH4 concentrations and δ13 C-CH4 at different sites varied from 1.74 × 10-6 to 2.56 × 10-6 and from - 39.31‰ to - 31.25‰, respectively. The factors affecting CH4 concentrations and δ13 C-CH4 values have also been discussed in this study.
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The molecular biomarker compositions of the ornithogenic sediments (YN), from Svalbard, Arctic were investigated. The results showed that nalkanes had a bimodal pattern and their odd-even preference was not obvious. The alkanes contained unresolved complex mixtures (UCM) and relatively high levels of pristine and retene, indicating pollution from the nearby coal mines. The
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The concentration and profile characters of nutrients in sediment pore water of the South Ocean, sampled during the cruise of CHINARE-18 of the austral summer 2001/02 were determined. The results show that the content of SiO3-Si and NH4-N were much higher than other nutrients. The profile of SiO3-Si was characterized with sharp gradients near the sediment-water interface, profile distribution of silicate show that during the diagenetic reaction of silicate, dissolution was the main part. The organic matter decomposition was occurred under the anaerobic condition. Benthic fluxes of SiO3-Si, NH4-N were from pore water to overlying water, and regeneration of silicate and ammonium were the main part of the nutrient regeneration from the pore water of the study area.
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Sediment, moss and animal-dropping samples were collected from Ny-Ålesund of the Arctic to investigate the distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the Arctic area. OCPs and PCBs were analyzed using the capillary gas chromatography (GC-ECD). Recoveries of three surrogates were at a range of 69.5～92.2% (mean: 78.8%), 75.1～112.1% (98.5%) and 67.7～95.1% (79.5%), and the relative standard deviations were 6.7%, 8.0% and 11.3%, respectively. The major monomers of OCPs were hexachlorocyclohexanes (HCHs) and DDTs. Their concentrations were at a range of 0.86～4.50 ng/g (mean: 2.24 ng/g) and 0.22～1.09 ng/g (mean: 0.55 ng/g). The concentrations of PCBs were 0.20～3.25 ng/g (mean: 0.84 ng/g) and the major congeners were tetra-, penta-, and hexa-PCBs, which were up to 23.8%、26.7% and 32.3% of total PCBs, respectively. Based on the results of the ratio analysis and the principal component analysis, the atmospheric transport is believed be one of the major input ways of OCPs and PCBs in the Ny-Ålesund of the Arctic.
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During the Second Chinese National Arctic Expedition (CHINARE) from July to September 2003, depth profiles of dissolved and particulate 234Th in upper water columns were collected at two stations of BR03 and BR24 in the Bering Sea. 234Th was sampled by using a traditional Fe(OH)3 co-precipitation technique, which is a reliable approach to 234Th measurement. We observed 234Th excess at station BR03 below the euphotic zone, which was possibly due to the intensive rem ineralization of particulate matter. Particulate organic carbon (POC) export fluxes were estimated from a one-dimensional irreversible steady state model of 234Th fluxes together with measurements of the POC/234Th ratio on the suspended particles. The POC export fluxes from the euphotic zone were 11.66 and 11.69 mmol Cm-2 d-1 at BR03 and BR24 stations, respectively. The ratios of POC fluxes to primary production at the two stations were about 0.5 and 0.59, respectively, probably due to the presence of large phytoplankton (in particular diatoms).
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Based on MODIS snow products, this article studied the changes of snow cover area during 2003—2006 along the coastline of the Antarctic, and 18 typical regions were chosen for further analysis. The result showed that the change of snow cover area was in a fluctuant downward trend as a whole, and more fluctuated obviously in warm season than in cold season. In temporal scale: for the season cycle, the snow cover extent increased rapidly in cold season (Apr-Oct), while the performance in warm season (Nov-Mar) was not exactly the same during the four years, the snow cover extent decreased in the first and then increased in 2004 and 2006, however, increased firstly and then decreased but reduced as a whole in 2005, for the inter-annual cycle, snow cover extent was the largest in 2003, but reached to the lowest level in 2004, and then increased gradually in 2005 and 2006, whereas, it declined with fluctuant as a whole. In spatial scale, changes mainly centralized along the coastline, moreover, it was more remarkable in the West Antarctic than in the East Antarctic, especially in the Antarctic Peninsula region.
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The in situ sea-ice temperature, salinity and density observed from Chinese Antarctic Zhongshan Station have been applied to calculate the vertical profile of sea ice porosity. Based on numerical method, a number of schemes on sea-ice thermal diffusivity versus porosity have been accessed and one optimized scheme is identified by an optimal control model with an advanced distributing parameter system. For simplicity, the internal heating source item was neglected in the heat conduction equation during the identification procedure. In order to illustrate the applicability of this identified scheme, the vertical ice temperature profiles have been simulated and compared with measurements, respectively by using identified scheme and by classical thermodynamic formulae. The comparisons indicated that the scheme describing sea-ice thermal diffusivity and porosity is reasonable.In spite of a minor improvement of accuracy of results against in situ data, the identified scheme has a more physical meaning and could be used potentially in various applications.
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