十块中国球粒陨石元素丰度特征研究

利用仪器中子活化分析方法,对宁强、随州、枣阳、南通、肇东、广南、东台、清镇、武安、导河等陨石进行了多元素分析测定.给出了近40种元素含量结果.并对各类球粒陨石微量元素丰度特征、REE丰度特征以及宁强陨石元素丰度特征进行了讨论.     

宁强碳质球粒陨石基质及暗色边化学成份研究

采用仪器中子活化方法分析了宁强碳质球粒陨石基质及暗色边化学成份。结果表明,宁强陨石的基质比全岩富集轻稀土和亲硫元素,并大致具有与Allende陨石基质相似的稀土特征。暗色边与陨石基质的差别在于:前者富FeO而贫难熔元素。推测陨石基质与暗色边物质来源于太阳星云不同区域。与形成暗色边有关的突发性事件可能曾多次在太阳星云的不同区域中发生。     

植物杀害恐龙获实证

中国科学家最近根据对部分恐龙化石的化学分析，发现了植物杀害这种史前动物的证据。他们选取了五十多个埋藏在四川盆地中部、北部和南部的侏罗纪不同时代的恐龙化石样本，并对照同时代的鱼类、龟类及植物化石进行了中子活化分析，发现恐龙骨骼化石中存在微量元素异常。主持这项工作的成都理工学院博物馆馆长李奎说：“这些恐龙骨骼化石中砷、铬等元素的含量明显偏高，有可能是恐龙生前过多食高砷、铬植物，新成代谢使砷、铬沉淀在骨骼中的结果。”对恐龙化石埋藏地的植物化石研究表明，植物化石中含砷量也非常高。砷即是砒霜，过量摄入会导…     

铁陨石中若干元素的仪器中子活化分析及其化学分类

本文采用堆中子和超硼中子活化方法对Mundrabilla、浙江宁波、湖北黄陵、河北商都、广西南丹、贵州董岭、四川乐山、广西邕宁、新疆准噶尔等九个铁陨石和吉林陨石的金属颗粒作了分析,测定了Ge,Ga,Ir,Ni,Au,As,Cu和Co等八个元素的含量。并对九个铁陨石作了化学群的分类,它们分别属于ⅠAB,ⅢAB,ⅢCD和IVA群。南丹和董岭铁陨石的化学组成极为相似,它们可能是“成对”的铁陨石。      

月面克里普岩成分特征及REE等资源开发利用前景

克里普岩(KREEP)最早发现于Apollo-12样品，后来在所有返月样品中都发现3克里普岩碎片，尤其以Apolio-12和Apolio-14着陆点样品中最多，因其富含元素K1REE和P而被称之为KREEP．克里普岩在月面上的分布极为重要，不但因其对月壳形成期间及形成以后的月球的演化具有重要的意义，而且由于克里普岩中富含REE等重要资源性元素，被认为可能是除钛铁矿外最重要的月球矿产资源储存库．本文在综合已有探测资料和研究成果的基础上，通过克里普岩的化学成分与矿物组成特征，Th在风暴洋区丰度的异常特征，以及克里普岩中Th与REE相关关系的分析，探讨了KREEP岩石在月面上的分布区域，进而对月球REE资源的开发利用前景进行了初步评估．     

铀矿石浓缩物中非金属杂质成分分析标准物质研制

研制两个水平的铀矿石浓缩物中非金属杂质成分分析标准物质,用于铀矿石浓缩物产品中S,P,F,Cl和Si等杂项的量值传递和测定过程的监控,确保铀矿石浓缩物产品的质量和后续纯化过程的稳定运行,同时也可用于二氧化铀（粉末和芯块）、四氟化铀等产品中相关元素的量值传递和质量控制。标准物质的均匀性采用F检验法评价,稳定性采用t检验法评价,各元素的定值采用多家实验室比对^[1~5]。标准物质研制的所有过程均符合“一级标准物质技术规范”。     

亳县陨石中球粒的主量和微量元素的丰度特征及其启示

用仪器中子活化法分析了毫县(LL3-4)陨石中14个球粒的Al,Mg,Mn,Na,V,La,Sm,Au,Sc,Cr,Fe,Co,Ni,Eu,Ir等元素的含量。该陨石的球粒平均成分对Mg和Cl球粒陨石标准化值与其它不平衡普通球粒陨石一致。通过模糊聚类分析和因子分析讨论了元素间的相关关系。这些球粒的原始物质组分至少包括亲铁元素,难熔和中等难熔亲石元素以及中等挥发性元素等,这也与其它不平衡普通球粒陨石大体一致。因此,普通球粒陨石各化学群的差别主要是由基质造成的。      

我国九个球粒陨石化学组成的研究

在球粒陨石化学组成的研究中,经过试验我们建立了测定各化学元素的分析流程,测定了九个球粒陨石样品中各元素的含量,根据测定结果论证了它们各自所属的化学群、氧化还原趋势以及某些共同特征。     

我国某些普通球粒陨石金属相的元素分布

本文用仪器中子活化分析法测定了我国不同化学群的吉林(H₅),信阳(H₅)、肇东(L₅)、广饶(L_6-5)和东台(LL₆)等普通球粒陨石金属相的Fe、Ni、Co、Cu、Cr、Mn、Ga、Ge、Ir、Au和As含量.每个陨石的金属相按粒径分为>20目.20—40目.<40目等.根据这些结果,讨论了元素的分布规律和分馏趋势以及决定金属相组成的作用过程.      

球粒陨石中单球粒硅含量测定及其意义

本工作采用14MeV中子活化分析方法,测定了20个单球粒及全岩的硅含量.结果表明:E、H、L、LL群石陨石中单球的硅含量均高于全岩的硅含量;全岩硅含量,按E、H、L、LL的次序,有逐步增高的趋势;非磁性单球硅含量,在普通球粒陨石中,按H、L、LL次序逐步增高.单球中硅含量高于全岩,间接证明凝聚形成球粒稍早于基质.      

Meteorites in Antarctica — Statistics on falls, concentration, recovery and alteration on ice-sheet

The Antarctic meteorites are distributed on the blue-ice area surfaces in the ablation zone of the Antarctic ice-sheet, to where meteorites have been transported by the ice-flow within the ice-sheet from the wider accumulation zone. Among the Antarctic meteorite collection H- and L-chondrites are most abundant; this is also true in the non-Antarctic meteorite collection. Meteorite showers also are involved in the collection. Several new types of stony meteorites have been discovered from the Antarctic meteorite collection. The mass and shape of Antarctic meteorites are in agreement with those of resultant fragments of high-speed impact basaltic rocks. In Antarctica, small fragments of meteorite smaller than 1 kg in weight can easily be found and collected. The solidification and the gas retention ages of Antarctic meteorites also are concentrated around 4.5×10⁹ years, but some of them are considerably younger. Their cosmic-ray exposure ages are extended up to 9×10⁶ years and their terrestrial ages are 9×10⁴-7×10⁵ years.     

Early solar system magnetic fields as recorded in meteorites

A number of meteorites have now been analyzed on a particle by particle basis to assess whether the magnetizations are random or are uniform in direction. The most detailed studies have been on the Allende meteorite and on the Abee meteorite. The chondrules (clasts) have randomly oriented magnetizations which strongly suggest that they record fields that predate the accretion of the meteorites. These fields are large in intensity and range from 1–20 oersteds. Although we do not know the origin of these fields we infer that they infer pre-meteorite fields in the solar system. Several other meteorites have been studied in a similar way and in some cases they show similar results, while in others there is clear evidence of accretion or post-accretion fields.     

Century scale solar variability imprinted in the 44Ti activity in meteorites.

The measurements of gamma-activity of the 44Ti (T1/2 = 66.6 years) produced by spallation reaction of galactic cosmic rays (GCR) in Alfianello, Olivenza, Rio Negro, Dhajala and Torino meteorites, which fell in the time interval 1883 AD (Alfianello)-1988 AD (Torino), show a century scale modulation, connected to long-term solar-wind flux variations in the interplanetary space. The variation of the 44Ti activity with the time of fall of meteorites is qualitatively consistent with the Gleissberg solar cycle, but the amplitude is three-four times higher than expected (about 5%) for GCR flux modulated by solar activity, as determined solely by the sunspot number. The cosmogenic 44Ti is a suitable radioisotope for this investigation, but its activity in meteorites is very low. We performed these measurements in the underground low level counting station of Monte dei Cappuccini in Torino, by means of a big hyperpure Ge crystal (approximately 2 kg) in selective coincidence with a heavy NaI (T1) scintillation detector (approximately 28 kg). This system allows a reliable and non destructive measurement of 44Ti (44Sc) in meteorites of 200-1200 g in weight. The background is about 1 count per day in the gamma-peak at 1157 keV of 44Sc in equilibrium with its parent 44Ti. The high stability of the performance allows long-lasting runs (approximately 10(7) s) in order to attain results with a standard deviation up to about 10%.     

Mid 19th century minimum of galactic cosmic ray flux inferred from Ti in Allegan meteorite

Measurements of ⁴⁴Ti activity in meteorites show that the galactic cosmic ray (GCR) intensity has been declining in the interplanetary space during the past three centuries and has a component of cyclic variation, with periodicity of about 87 years [Taricco, C., Bhandari, N., Cane, D., et al. Galactic cosmic ray flux decline and periodicities in the interplanetary space during the last 3 centuries revealed by ⁴⁴Ti in meteorites. J. Geophys. Res. 111, A08102, 2006.]. In order to verify these results, we have measured ⁴⁴Ti activity in Allegan meteorite which fell in 1899 and in some other meteorites with better precision. The measurements confirm low cosmic ray flux and consequently high solar activity near the middle of 19th century.     

吉林陨石（H5）的冲击压缩线及其意义

在二级轻气炮动高压装置上运用电探针技术测量了具有H群球粒陨石典型代表性的吉林陨石冲击压缩线。当冲击压力>～70GPa时,吉林陨石发生相变,其高压相零压密度为4.425g/cm~3,硅酸盐部分高压相零压密度为4.068g/cm~3。吉林陨石冲击压缩性质的研究结果与地球形成的星子堆积模型(IAB铁陨石+H群球粒陨石)一致。此外,根据陨石或其类似物的冲击压缩线,用阻抗匹配原理计算了主要类型陨石中重要冲击特征形成的最小碰撞速度,揭示了陨石冲击效应形成的动力学条件与空间环境。     

Detection of martian amino acids by chemical derivatization coupled to gas chromatography: in situ and laboratory analysis.

If there is, or ever was, life in our solar system beyond the Earth, Mars is the most likely place to search for. Future space missions will have then to take into account the detection of prebiotic molecules or molecules of biological significance such as amino acids. Techniques of analysis used for returned samples have to be very sensitive and avoid any chemical or biological contamination whereas in situ techniques have to be automated, fast and low energy consuming. Several possible methods could be used for in situ amino acid analyses on Mars, but gas chromatography would likely be the most suitable. Returned samples could be analyzed by any method in routine laboratory use such as gas chromatography, already successfully performed for analyses of organic matter including amino acids from martian meteorites. The derivatization step, which volatilizes amino acids to perform both in situ and laboratory analysis by gas chromatography, is discussed here.     

Biogeochemical evidence of microbial activity on Mars.

We suggest a new interpretation of the data on so-called SNC meteorites and delta 13C values of the calcium carbonate minerals and organic matter discovered in them. The delta 13C value of calcite (up to 15 ppt) is accounted for by the microbial reaction CO2 + H2 ---> CH4 + H2O. Methane-forming bacteria also synthesize organic carbon (in the form of biomass) from CO2, and this process is accompanied by 12C fractionation. Therefore, the organic carbon of SNC meteorites is enriched with 12C (delta 13C as low as -35 ppt). The environmental conditions under which the calcite of SNC meteorites was formed were favorable for the activity of methanogens.     

Ocean circulation studies in the vicinity of Southern Africa: Preliminary results using FGGE drifters and remote sensing

The three highly variable ocean circulation systems which meet south of South Africa have been studied by combining the use of satellite thermal infra-red imagery, hydrographic measurements and drifting buoys. We present a few preliminary examples where this method has been successful. These include the sources of the Agulhas Current, the influence of the Agulhas Current on the Cape upwelling region as well as the interaction of the Agulhas Current with the Subtropical Convergence. An example is also given of how a biological hypothesis concerning the recruitment of a rock lobster species at Vema Seamount has been supported by the analysis of the drifts of FGGE buoys in the South Atlantic Ocean.     

微波和THz频段用于遥感标准的研发

美国国家标准和技术研究院(NIST)电磁部噪声规划提出了遥感应用例如卫星气象观测中的微波亮温度标准的研发。这个标准以现有波导系统电磁噪声基准为基础,与亮温度即辐射有关,借助一个特性很好的天线实现。热校准目标作为基准的补充,采用冗余测量的方式,用于检验或者减小不确定度。做过的26 GHz的初步测量表明所提出标准的可行性,同样太赫兹(THz)频率的研究也在进行中。对于THz噪声,用一个加热的目标作为噪声标准,虽然我们没有这么高频率的噪声基准。这个标准将与THz辐射计一起使用。辐射计基于一个接收机,该接收机采用了一个热电子测辐射热混频器,并被准光学适配器耦合到辐射中去。希望年底能够用这套系统进行THz噪声测量。