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30 March 1995, Volume 7 Issue 1 Previous Issue    Next Issue
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PETROGRAPHY AND MINERALOGY OF THE MESOZOIC CENOZOIC VOLCANIC ROCKS FROM THE CENTRAL PART OF LIVINGSTON ISLAND,WEST ANTARCTICA 1995, 7 (1):  4-19.  Abstract ( 1750 )   PDF (455KB) ( 1216 )   The Middle Late Cretaceous volcanoclastic rocks outcropped on the central part of Livingston Island include heteromict lapilli tuffs,lapillistone and agglomeratic breccias predominantly andesitic in composition.Olivine basalts with holocrystalline porphyritic texture are mainly found in the Shirreff Point.Most basaltic andesite and andesite outcropped in Central Livingston and Hannah Point are finely crystalline with mino microporphyritic texture.The holocrystalline porphyritic olivine basalts and pyroclastic rocks are the components of Pleistocene to recent volcanic activities.On the whole,the mineral association,Plagioclase+pyroxene(+olivine)+iro opaque,is much similar in distinctive lavas,however,the content of minerals is different.The plagioclase phenocrysts are usually with normal zoning,the Or and Ab components increase and An decreases with increasing SiO 2 content of rocks and the composition of the phenocryst margin is almost the same as that of plagioclases in matrix.The predominant phenocrysts of basaltic adnesite and andesite are andesine labradorite,that of basalt is labradorite,whereas the core of plagioclase phenocryst of the olivine basalt from Shirreff Point or the dolerite from Siddons Point is bytownite.The plagioclase in the Pleistocene to recent olivine basalt,either as phenocryst or in matrix,is richer in CaO.The clinopyroxene phenocryst associates with plagioclase forming a porphyritic texture or glomerocryst texture.Augite is mainly found in basaltic andesite and diorite in olivine basalt and basalt,both pyroxene are depleted in Ti.The olivine composition of dolerite is similar to the matrix olivine in the olivine basalt from Sirreff Point,where chrysolite is the major phenocryst.There are two types of olivine phenocrysts in the olivine basalt with Pleistocene to recent age,one was crystallized under a general crystallizing condition and the other was the xenocryst with high Fo content.Above mentioned characteristics of the mineral associations suggested that the volcanic rocks were probably formed by an equilibrium crystallization.The olivine basalt from Shirreff Point has a genetic relationship with the dolerite in Siddons Point as showed by the olivine composition and the high An content of plagioclase,however,differs from the rocks of Central Livingston and Hannah Point.The olivine xenocryst found in the youngest olivine basalt indicates the magma was a primary basaltic magma which was directly derived from a deep magma chamber. Related Articles | Metrics

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INSPIRATION FROM STUDY OF ANTARCTIC METEORITES Ⅴ:THE CHEMICAL COMPOSITIONS OF ANTARCTIC METEORITES AND THEIR CLASSIFICATION 1995, 7 (1):  20-27.  Abstract ( 1616 )   PDF (235KB) ( 1146 )   We report concentrations of 13 elements in the metal of 52 Antarctic iron meteorites and their classification based on the structures and their Ga,Ge,Ni,Ir and other trace elemental contents.The 52 iron meteorites assigned to chemical group consist of 16 of IAB,12 of IIAB,1 of IIE,3 of IIIAB,1 of IIICD,1 of IVA and 18 of ungrouped irons.The IAB,IIICD and IIE iron meteorite groups are considered to be of nonmagmatic origin.Nonmagmatic IAB,IIICD and IIE irons formed as individural pools of a chondritic body.The other groups,IIAB,IIIAB and IVA show evidence of having originated by fractional crystallization of a metallic magma.The slopes on element Ni trends are generally higher in magmatic than in the nonmagmatic groups.Most interestings are that there are high abundance of ungrouped and IAB (47.2% and 27.8%,respectively) and low abundance of IIIAB (5.8%) iron meteorites from Antarctica relative to non Antarctic iron meteorites,which contain information about previously unsampled parent planets,mass,shock and collision,as well as nebula regions. Related Articles | Metrics

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THE CHARACTERISTICS OF GEOPHYSICAL FIELD AND TECTONICAL EVOLUTION IN THE BRANSFIELD STRAIT 1995, 7 (1):  28-38.  Abstract ( 1388 )   PDF (633KB) ( 1314 )   There we analysised the data were collected using our survey ship-Ocean Ⅳin the Bransfield Strait in 1991. We recognized that the geomorphology、gravity and magnetic anomalies trend NE direction as bandings. The sediments in the Bransfield Strait are subdivided into two sequences:first rifting sequence and second rifting sequence. The basement was faulted into a half graben faulting in northwest side of the Bransfield trough. Considered the crustal structure crossing the South Shetland Islands、Bransfield Strait and Antarctic Peninsula,we proposal a two phase rifting tectonical evolution model and layered shear model for the lithospheric deformation under extensional stress field. Related Articles | Metrics

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THE BASIC CHARACTERISTICS OF ATMOSPHERIC ELECTRIC FIELD AT ZHONGSHAN STATION, ANTARCTICA 1995, 7 (1):  39-50.  Abstract ( 1246 )   PDF (189KB) ( 1143 )   This is the first report about the analysis of atmospheric electric fields observed at Zhongshan Station,Antarctica. This paper mainly focuses on the basic observation situation and the average characteristics of the surface electric field. The average characteristics includes spectra in several time scales, seasonal variation, and typical feature in different weathers. These fundamental features can be considered as "background" and will be applied to the analysis of the controlling factor in the formation of this average characteristics of electric field. Furthermore, on the basis of this "background" we will explore the response of atmospheric electric field to all kinds of disturbances. Related Articles | Metrics

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LIDAR OBSERVATIONS OF POLAR STRATOSPHERIC CLOUDS IN ANTARCTICA 1995, 7 (1):  47-52.  Abstract ( 1596 )   PDF (278KB) ( 1351 )   A Lidar system (694nm) was used to measure the stratospheric aerosol at Zhongshan Station(69°22′S, 76°22′E) in 1993. The Lidar data presented in this paper were obtained between March 27 and November 5,1993. A total of 53 times of Lidar observations was made over the 9 month period.In this paper we present Lidar observations of the vertical profiles of the stratospheric aerosol backscattering ratio and the integrated backscatter coefficients over the 12-30km altitude range. The observations show that the stratospheric aerosol particulate matter noticeably enhanced in 1993 than that in 1990 due to Mt. Pinatubo eruption in Philippines in June 1991. We presented the seasonal variation of the integrated backscatter coefficient(IBC). The mean value for each observation period is plotted in Fig.2. The noticeable maximum of IBC is easily found in winter season from curve in Fig 2. Maximum value of IBC is 3.4×10 -3 (sr -1 ). Polar Stratospheric Clouds(PSCs) are observed from late May until September.The vertical profiles of the stratospheric aerosol backscattering ratio in Antarctica show a clear double layer structure, one layer is at a altitude of about 12km, another is at a altitude of about 25km. In this paper we analyze the vertical structure of backscattering ratio. Related Articles | Metrics

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THE HIGH LATITUDE PHENOMENA SHOWN BY IONOGRAM OBSERVED AT ZHONGSHAN STATION IN ANTARCTICA 1995, 7 (1):  53-61.  Abstract ( 1448 )   PDF (196KB) ( 1068 )   The ionograns observed at Antarctic Zhongshan Station in the polar cusp region have shown that there are a number of high latitude phenomena.This paper presents these phenomena.They are auroral oval phenomena,FLIZ phenomena,slant Es phenomena and lacuna,F region magnetic noon phenomena,and particle precipitation effects in the E region. Related Articles | Metrics

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TEMPERATURE DISTRIBUTION IN COLLINS ICE CAP, KINGGEORGE ISLAND, ANTARCTICA 1995, 7 (1):  62-69.  Abstract ( 1420 )   PDF (209KB) ( 1292 )   The temperature measurement in boreholes shows that the Collins Ice Cap has characteristics of temperate glacier in most parts of the accumulation area, but it is characterized by cold glacier in ablation area. The ice temperature of the active layer is noticeably affected by seasonal variations of air temperature. The water infiltrating and warming is very strong. The snow cover also casts some influence on temperature distribution. The observed data have revealed that the ice temperature in deep layers is at the freezing points,but the temperature varies greatly in the vicinity(10-20m) of the Little Dome.Water seeping is very significant at the depth of 30m in someboreholes while drilling in the vicinity of the Little Dome. This can be explained by internal runoff, different ice movement, etc. Related Articles | Metrics

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STUDIES ON NANO AND MICROALGAE IN THE ADJACENT WATERS OF ANTARCTICA Ⅴ.DISTRIBUTION OF FRESHWATER ALGAE IN DIFFERENT HABITATS AROUND GREAT WALL STATION 1995, 7 (1):  70-77.  Abstract ( 1368 )   PDF (443KB) ( 1447 )   This paper reports the species composition,distribution,ecotypes and similarity of freshwater algae from five different habitats,i. e. in water,snow, mud sand of West Lake and red colored snow in penguin guano and snow in moss cushions around Great Wall Station. The difference is obvious in composition and abundance of algae among the habitats. Algae abundance revealed in the range of 11.04×10 3 ～ 2337.12×10 3 individuals or cells per dm 3 of the water and snow melted water or per gram of mud sand. According to habitats or the different mode of life, 50 taxa of 3 phyla in total are distinguished into two ecotypes:water algae and terrestrial (snow) algae; or freshwater planktonic algae and freshwater benthic (epiphytic) algae. Related Articles | Metrics