Weathering, shock metamorphism and type distribution patterns of 98 ordinary chondrites from the Grove Mountains, Antarctica

Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains (GRV), Antarctica, were presented and their.weathering effect, shock metamorphism and type distribution patterns were discussed in this study. Among them, six are unequilibrated ordinary chondrites, including 3 H3 and 3 L3; and 92 meteorites are equilibrated ordinary chondrites, including 24 H-group (13 H4, 10 H5, 1 H6), 64 L-group (2 L4, 44 L5, 18 L6) and 4 LL-group (3 LL4, 1 LL5). Most GRV chondrites (>90%) displayed minor weathering effect (W1 and W2). About half of the meteorites experienced severe shock metamorphism. They commonly contain shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals. In addition, the Grove Mountains collection seems to have more abundant unequilibrated and L group ordinary chondrites compared to the US Antarctic meteorite collection which were mainly found along the Transantarctic Mountains.     

Shock metamorphism of ordinary chondrites from Grove Mountains, Antarctica

Shock effects of 93 Grove Mountains (GRV) ordinary chondrites were studied in this work, including fracture, various types of extinction, and recrystallization of silicates observed under optical microscopy. Shock-induced veins and pockets show various microtextures, decomposition and phase transformation of minerals. The confirmed high-pressure polymorphs of silicates are ringwoodite, majorite, pyroxene glass and maskelynite. Based on the shock effects and assemblages of high-pressure minerals, shock stages of all of 93 GRV chondrites were classified. In comparison with literature, the Grove Mountains meteorites have a higher fraction (23 out of 93) of heavily shocked samples (S4-S5). Most of the heavily shocked meteorites are L group (22 out of 23), except for one H chondrite. The distinct shock metamorphism between H and L groups may indicate different surface properties of their parent bodies. In addition, there is relationship between petrologic types and shock stages, with most heavily shocked samples observed in equilibrated ordinary chondrites (especially Type 5 and 6).     

Exposure ages and radiogenic ages of ureilite(GRV 024516) and ordinary chondrite(GRV 024517) from Antarctica

The GRV 024516 and GRV 024517 meteorite samples collected from Grove Montains,Antactica are ureilite and H5 ordinary chondrite,respectively.Based on the study of mineralogy-petrology,the cosmic-ray exposure ages and gas retention ages of these two meteorites were determinated and calculated.Their cosmic-ray exposure ages are 33.3 Ma,51.7 Ma,and gas retention ages are 1936.8 Ma and 3720 Ma,respectively.The ureilite contains diamond,graphite and amorphous C,which are mainly carrier of noble gases indicating obviously shock metamorphism effects,which induced 40Ar partial loss.The H5 chondrite indicates thermal metamorphism of parent body,its gas retention age fall the range between 3220 Ma and 4510 Ma of the least shocked H5 chondrites     

Petrology of ureilites from Grove Mountains, Antarctica：Constraints on the origins

Ureilites are a common group of achondrites with a high abundance of carbon. They probably have a genetic relationship with chondrites, hence provide an insight into origin and evolution of terrestrial planets. A new meteorite-rich region, Grove Mountains (GRV), was found by the Chinese Antarctic Research Expedition, with discovery of 9834 meteorites. Of 2433 meteorites classified, 9 ureilites have been identified. In this paper, we report petrography of 6 of these ureilites. Four ureilites contain graphite and exhibit triangle conjunction and common reduced margins of olivine. GRV 052382 probably experienced heavy shock metamorphism followed by fast cooling, as indicated by mosaic texture or fine-grained granular texture of olivine. GRV 022931 was highly reduced of these ureilites, with olivine as isolated grains in abundant carbonaceous matrix. All 9 ureilites are monomict, and are classified into subtype II (with medium FeO content, Fa15-18) and subtype I (with high FeO content, Fa>18) based on compositions of the cores of olivine. The diverse mineral compositions and petrography of these ureilites suggest that they are not paired and reveal a multi-event history of the parent body. Partial melting of the parent body produced carbon-rich magma, followed by crystallization of graphite and silicates. Later, graphite was partially inverted to diamond by shock events. Reburial of the shocked debris experienced various degree of thermal metamorphism. Finally, these rocks were excavated from the parent asteroid and ejected into Earth-cross orbit by another impact event.     

Meteorites from Grove Mountains, Antarctica:An overview

Thirty-two meteorites were collected in Grove Mountains area, Antarctica, by the 15th and 16th Chinese Antarctic Research Expeditions (CHINARE). Petrography and mineral chemistry of these meteorites are reviewed, among which there are one Martian lherzolite, one eucrite, one ungrouped iron meteorite, and six unequili-brated and twenty-three equilibrated ordinary chondrites. An equilibrated ordinary chondrite GRV 98004 ( H5 ) has an unusually low cosmic-ray exposure age. Meteorite concentrating processes in Grove Mountains area are discussed. In addition, future studies on Grove Mountains (GRV) meteorites are proposed.     

Petrography and Mineral Chemistry of 4 Carbonaceous Chondrites from the Grove Mountains, Antarctica

Petrography and mineral chemistry of four carbonaceous chondrites (GRV 020017, GRV 020025, GRV 021579, GRV 022459) collected from the Grove Mountains (GRV), Antarctica, were reported here. All four chondrites are unequilibrated, as indicated by well shaped chondrules and the chemical variations of olivine and low-Ca pyroxene. The modal abundance ratio of matrix/chondrule are 2(GRV 020017), 2.8(GRV 020025), 1.2(GRV 021579), 1(GRV 022459). GRV 022459 has the largest chondrules(0.6-2.0mm). A total of 30 Ca-Al-rich inclusions were found in the four meteorites. Most inclusions were highly altered, with abundant phyllosilicates in the inclusions of GRV 020017 and GRV 020025. On the base of petrography and mineral chemistry, these chondrites are classified as CM2 (GRV 020017 and 020025), CO3 (GRV 021579) and CV3 (GRV 022459).     

Archaeal diversity and abundance within different layers of summer sea-ice and seawater from Prydz Bay,Antarctica

Fluorescence in-situ hybridization （FISH） and 16S rRNA gene clone library analyses were used to determine the abundance and diversity of archaea in Prydz Bay, Antarctica. Correlation analysis was also performed to assess links between physicochemical parameters and archaeal abundance and diversity within the sea-ice. Samples of sea-ice and seawater were collected during the 26th Chinese National Antarctic Research Expedition. The results of FISH showed that archaea were relatively abundant within the top layer of the sea-ice, and correlation analysis suggested that the concentration of 4NH＋ might be one of the main factors underlying this distribution pattern. However, using 16S rRNA gene libraries, archaea were not detected in the top and middle layers of the sea-ice. All archaeal clones obtained from the bottom layer of the sea-ice were grouped into the Marine Group I Crenarchaeota while the archaeal clones from seawater were assigned to Marine Group I Crenarchaeota, Marine Group II Euryarchaeota, and Marine Group III Euryarchaeota. Overall, the ifndings of this study showed that the diversity of archaea in the sea-ice in Prydz Bay was low.     

SR-XRF analysis of Polytrichum in the Fildes Peninsula,Antarctica

In order to study the element contents and distribution of various mosses collected in the Antarctica, we analyzed the heavy elements of 3 species of Polytri-chum in the Fildes Peninsula, P. alpinum, P. juniperinum and P. alpestre, by synchrotron radiation X-ray fluorescence ( SR-XRF). The result shows that the elements, such as K, Ca, Mn, Fe, Cu, Zn and Sr, are nearly the same in Potytrichum. The peak intensity of K is higher than that of Ca, and the peak intensity of Ca is higher than that of Fe in P. alpinum. In P. juniperinum, the peak intensity of K is higher than that of Ca, and the peak intensity of Ca is close to that of Fe. The peak intensity of K is nearly equal to those of Ca and Fe in P. alpestre. Therefore, the habitats of 3 species of Polytrichum are similar in the Fildes Peninsula. By XRF analyzing of different parts of P. alpestre, we found that the peak intensities of relative concentration of elements are obviously different. The peak intensity of K in apical-bud is the highest in orga     

Ecological differences of south polar skua populations from Fildes Peninsula of King George Island and eastern Larsemann Hills, Antarctica

A study has been done on the comparison of nesting and feeding behavior, population variances as well as breeding success between two populations of south polar skua (Catharacta maccormicki) from near Great Wall station on Fildes Peninsula and near Zhongshan station in Eastern Larsemann Hills, Antarctica. There are evident differences in their population ecology. The foraging habit is much related to regional ecosystem and food resources near their territorial area. Dependence on human food waste influences skua‘s diet,which considerably affects their behavior even population variation in both areas. The skuas in Zhongshan Station,could shorten and/or regulate the timing for their egg laying and hatching, and take precedence of one chick brooding, for keeping their breeding success, and subsequent species continuation.     

Summer weather characteristics on the Grove Mountain of East Antarctica

The summer weather characteristics of the Grove Mountain, East Antarctica, are presented based on the data obtained by Chinese National Antarctic Expedition (CHINARE) in January 1999. The result shows that the pattern of daily variation of temperature and the prevailing wind direction in Grove is similar to that of Zhongshan Station. However, the daily range of temperature and strong wind frequency are much higher than those of Zhongshan Station. The change of wind direction is close to the weather system that impacted the Grove Mountain. The warm and wet air from northern parts often causes the precipitation. The clear weather appears when controlled by eastern winds in January.     

Occurrence and diversity of marine yeasts in Antarctica environments

A total of 28 yeast strains were obtained from the sea sediment of Antarctica.According to the results of routine identi-fication and molecular characterization,the strains belonged to species of Yarrowia lipolytica,Debaryomyces hansenii,Rhodotorula slooffiae,Rhodotorula mucilaginosa,Sporidiobolus salmonicolor,Aureobasidium pullulans,Mrakia frigida and Guehomyces pullu-lans,respectively.The Antarctica yeasts have wide potential applications in biotechnology,for some of them can produce b-galactosidase and killer toxins.     

The establishment of GPS network in Grove Mountains, East Antarctica

1 Introduction The Grove Mountains is located at Princess Elizabeth land in East Antarctica, about 400 km from Zhongshan station and 160 km east of the Mawson Escarpment, consists of a scattered group of mountains and nunataks. The range extends73°-76°E…     

Holocene environmental change according to lake core in Fildes Peninsula of King George Island,Antarctica

Lake core sampled from Xihu in Fildes Peninsula of King Gorge Island, Antarctica could reveal the environmental change of the district. The lake core( GA7) , 9.28 meters long , was sectioned at an interval of 2 cm. Through measuring the organic carbon, magnetic susceptibility, granularity and organic carbon isotope of GA7, by use of 14C age it was estimated that there were four periods of high temperature in Fildes Peninsula; 4800-4400 aB. P. , 3600-3350 aB. P. ,2100 - 1800 aB. P. and 900 aB. P. - present. Meanwhile, results showed that there was a strikingly positive correlation between the content of organic carbon and that of organic carbon isotope (δC01213 ) which could be the substitute indicators of environmental temperature.     

The first geodetic investigation at the summit of Dome A,Antarctica

Dome A is the highest ice feature in the Antarctica,up to now,little is known about surface topography at Dome A.The first Chinese ITASE expedition was carried out from Zhongshan station to Dome A during the 1996/1997 austral summer. During the 2004/2005 austral summer,the traverse was extended to the summit of Dome A which is 1228 km from Zhongshan Station by 21st Chinese National Antarctic Research Expedition (CHINARE).The real-time kinematic (RTK) GPS survey was carried out in the summit of Dome A dur...     

Experimental culture of non-indigenous Juncus bufonius from King George Island,South Shetland Island,Antarctica

Juncus bufonius L. (Juncaceae) is recognized by the US Department of Agriculture as a weed or invasive plant. Recently, we reported on J. bufonius L. var. bufonius associated with the native vascular p...     

Long-term study of at-sea distribution of seabirds and marine mammals in the Scotia Sea,Antarctica

The Scotia Sea is one of the most biologically rich regions of Antarctica, and it hosts a large community of upper trophic-level predators. Long-term at-sea monitoring provides valuable information on ...     

Determination of element composition of three lichens and their distribution in King George Island, Antarctica

Cross-section slices of Usnea antarctica Du Rietz, Usnea aurantiaco-atra (Jacq.) Bory. and Cladonia sp. at upper, middle and basal positions were prepared, respectively. The element composition and relative content were determined by SEM and EDS at the surface, intermediate and inner layers in each slice, respectively. The result indicated that the composition of element is mostly same in these lichens. The relative content of Al, Si, K and Ca elements is high, and P is close at each position. The result is of benefit to study the structure and physiological characteristics of lichens, and to analyze geological environment in Antarctica.     

The 137Cs activity and its geographical significance in terrestrial ecosystem of Great Wall Station, Antarctica

The radioactive isotope——137 Cs is one of the important tracers for studying the physical processes and the human impacts on the environment. Based on the investigation results of the terrestrial ecosystem of Great Wall Station, Antarctica, it was shown that there are some artificial radioactive elements——137Cs in Antarctic terrestrial ecosystem. The sequence of 137Cs specific activities is as follows: crustaceous lichen>fruticose lichen>surface-moss>surface soil, and the crustaceous lichen is one of the most sensitive ways in monitoring the impact of the long-term diffusion of 137Cs on the environment.