Daode Wang

Grove Mountains (GRV) 99027: A new Martian meteorite

We report the petrography, mineral chemistry and oxygen isotopic composition of GRV 99027, a new Martian meteorite recently collected during the 16th Chinese Antarctic Research Expedition. This meteorite consists of two textural regions. The interstitial region is characterized by the presence of plagioclase and phosphate, and higher FeO contents of olivine and orthopyroxene, in comparison with the poikilitic region. All of the observations are similar to the three known Martian lherzolites. We classify GRV 99027 as the fourth sample of Martian lherzolite.

Parentage determination of an isolated Yangtze finless porpoise population Neophocaena phocaenoides asiaeorientalis in the Yangtze Tian-e-Zhou Baiji National Natural Reserve based on molecular data

Reproductive behaviors are poorly known for the Yangtze finless porpoise Neophocaena phocaenoides asiaeorientalis. In this study, the parentage of an isolated Yangtze finless porpoise population inhabiting the Yangtze Tian-e-Zhou Baiji National Natural Reserve is determined by analysis of microsatellite loci and mitochondrial DNA (mtDNA) control region sequences, and the porpoises reproductive behaviors are studied. Overall 4 full parentage assignments and additional 3 single parentage assignments were determined for the population of 23 individuals. The analysis shows that their estimated reproductive cycle is shorter than that reported previously and there probably exists an overlapping between gestation and lactation period. The Study also shows that the female does not show fidelity to a particular male for breeding and vice versa, the oldest males did not monopolize mating and the dominance rank could not be so strict for the porpoise society. Moreover, the porpoises mating pattern and relatedness among candidate parents are discussed here. These results provide important information for making guidelines of management and conservation for this protected population.

Noble gas and cosmic-ray exposure age of Juancheng chondrite

The analytical results of noble gase in recently fallen Juancheng chondrite indicate that cosmic-ray ages of cosmogenic nuclei of3He,21Ne and38Ar are 5.1, 5.0 and 5.8 Ma, respectively, averaging 5.3 Ma. The gas retention ages radiogenic nuclei of4He and40Ar are 3 200 and 4 200 Ma, respectively. The average cosmic-ray age shows that it has occurred at breakup of the meteoroid from its parent body by impact before 5.3 Ma.

Ca, Al-rich inclusions in Yamato 791717 (CO3) carbonaceous chondrite: Formation and alteration

In three polished thin sections of Yamato 791717 (CO3). fifty-five Ca, Al-rich inclusions were found, which include two hibonite-bearing, eight melilite-rich and forty-five spinel-pyroxene inclusions. Based on the petrography and mineral chemistry of the inclusions, it is proposed that the melilite-rich inclusions and spinel-pyroxene inclusions condensed in the solar nebula, and the hibonite-bearing inclusions crystallized from melts. The heavy alteration of the inclusions in Yamato 791717, which probably took place under a very oxidizing condition in the solar nebular, is also confirmed.

Neutron capture effects and pre-atmospheric sizes of meteoroids

Excesses of80Kr and82Kr, produced by secondary neutron capture effects of79Br and81Br, were observed in meteorites. Epithermal neutron flux,Jn (30–300 eV), and fast neutron flux,Jn(> 5 MeV), were determined according to reactions of79Br(n, γβ)80Kr,81Br(n, γβ)82Kr, and24Mg(n, α)21Ne, respectively. Cosmogenic noble gases of several ordinary chondrites fell in China indicate a positive relationship betweenJn(30–300 eV)/Jn(> 5 MeV) ratio andJn(30–300 eV). This suggests large pre-atmospheric sizes of the meteorites, and a considerable fraction of the secondary neutrons were slowed down to epithermal energy. According to its relationship withJn(30–300 eV)/Jn (> 5 MeV) ratio, the pre-atmospheric minimum radii and masses of several Chinese chondrites were estimated as below: Zhaodong: 60 cm, 3200 kg; Laochengzhen: 23 cm, 490 kg; Suizhou: 31 cm, 450 kg; Xi Ujimgin: 22 cm, 160 kg; Dongtai: 21 cm, 140 kg.

Cosmic-ray exposure and gas retention ages of the Guangmingshan (H5) chondrite

Isotopic compositions of noble gases from the Guangmingshan chondrite were analyzed. Based on the analyses of cosmogenic nuclei, cosmic-ray exposure age of the meteorite is (65±10.0) Ma (3He), (80±12) Ma (21Ne) and (65±10.0) Ma (38Ar), with an average of 70 Ma. This is the highest exposure age of H-group ordinary chondrites. Gas retention ages of K-Ar and U, Th-4He are (4230±100) Ma and (3300±60) Ma, respectively. The smaller ages of3He than21Ne and4He than40Ar suggest that both3He and4He lost together. This is probably related to a solar heating effect of a meteorite with a small perihelion during the last exposure period.

THE JUANCHENG CHONDRITE : A NEW METEORITE FALLING RECENTLY IN CHINA

The Juancheng chondrite, a new meteorite falling recently in Juancheng County, Shandong Province, China, is classified as an H5 (S2) chondrite based on the compositions of olivine (Fa = 19.2%, σFa= 0. 46) and low-Ca pyroxene (Fs = 16. 9%, σFa = 0. 4). The plagioclase in the Juancheng chondrite is rich in CaO, indicating a relatively high metamorphic temperature the parent body underwent.

Cosmic-ray exposure histories of two Antarctic meteorites from Chinese collections and the Guangmingshan and Zhuanghe chondrites

Concentrations of noble gases of two Antarctic meteorites (GRV 98002, 98004) from Chinese collections, and the Guangmingshan and Zhuanghe chondrites were measured. Based on the petrography and mineralogy of these meteorites, and production rates of the cosmogenic nuclides, we calculated cosmic-ray exposure and gas retention ages of the four chondrites. Exposure ages of the four chondrites are 0.052 Ma ± 0.008 Ma (GRV 98004, H5), 17.0 Ma ± 2.5 Ma (GRV98002, L5), 3.8 Ma ± 0.6 Ma (Zhuanghe, H5), and 68.9 Ma ± 10 Ma (Guangmingshan, H5), respectively. The exposure age of GRV 98004 is the lowest value of Antarctic meteorites reported up to date; while that of Guangmingshan is higher than other Chinese meteorites of H-group. Both GRV 98002 and Zhuanghe have low4He concentrations, probably due to shock effects or solar heating at orbits with small perihelion distances during cosmic-ray exposure. On the other hand, losses of cosmogenic3He and4He are correlated with both GRV 98002 and Guangmingshan.

Metallic phases of Dong Ujimqin mesosiderite: A field emission scanning electron microscope study

The microstructure of Fe-Ni metallic phases in Dong Ujimqin mesosiderite was studied using the field emission SEM. Taenite is characterized by a zoned structure, consisting of outer clear taenite and inner cloudy zone (CZ). CZ has a typical “island-honeycomb” microstructure. The average size of the island phase is about 358 nm, suggesting a cooling rate of ∼ 0.5°C/Ma at low temperature (< 400°C). The Ni concentration profiles across kamacite and zoned taenite were also measured by electron probe microscope analysis (EPMA). Formation of the Fe-Ni metallic phases, microstructure in Dong Ujimqin mesosiderite was discussed based on the new low-temperature Fe-Ni phase diagram.