Origin of microspherules in Paleozoic-Mesozoic bedded chert as estimated from its morphology

Summary In a previous study, we gave the PIXE analysis results of magnetic spherules collected from Paleozoic-Mesozoic bedded chert compared with carbonaceous chondrite and supposed the origin of microspherules to be interstellar in origin, similar to carbonaceous chondrite, rather than interplanetary. The previous suggestion was again confirmed from observation of the internal texture of microspherules.     

Cosmic history of some pallasites based on fossil track studies

Investigation of fossil charged-particle tracks in various mineral phases of extraterrestrial samples is a powerful method for research the early stages of the solar system. Examination of fossil charged-particle tracks in the phosphate and olivine crystals of 5 pallasites coupled with U content determination allowed the estimation of the contributions of all possible track sources to the total track density and calculation of a value of model fission-track age.

Phosphate crystals from all studied pallasites were established to contain fossil tracks due to galactic cosmic rays (VH, VVH nuclei); induced fission of U and Th by cosmic rays; spontaneous fission of ²³⁸U; spontaneous fission of extinct short-lived ²⁴⁴Pu nuclei presented in significant quantities in the early solar system. The discovery of a high track density attributed to the extinct ²⁴⁴Pu pointed obviously to the high value of the fission-track age. Model fission-track ages of (4.37±0.02) Gyr for the Marjalahti pallasite; (4.37±0.01) Gyr for the Omolon pallasite; (4.19±0.02) Gyr for the Bragin pallasite; (4.18±0.03) Gyr for the Krasnoyarsk pallasite; (4.21±0.02) Gyr for the Brenham pallasite were calculated. The comparison of represented data with petrographic analyses allowed us to interpret a value of fission-track age as the time of the last intensive shock/thermal event in the cosmic history of a pallasite.     

The Renazzo meteorite

Summary An imaging spectrometer developed for a space mission (Mars 94) is being used to study meteorites with solar illumination. It is shown that for a carbonaceous chondrite like the Renazzo meteorite it is possible to study also the internal composition of large chondrules, by making use of all the information of the image cube obtained. Inside chondrules, 3 typical materials are identified. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

On search and identification of tracks due to short-lived SHE nuclei in extraterrestrial crystals

The unique approach for search and unambiguous identification of short-lived (T_1/2=10³–10⁷ years) superheavy nuclei in cosmic-ray products of the recent nucleosynthesis in our Galaxy are discussed.It is based on: (a) the ability of non-conducting crystals to register and to store for many million years the tracks due to fast nuclei with atomic number Z20 (“fossil” tracks);(b) calibrations of the said crystals with accelerated heavy ions (20Z92) and on revealing the volume etchable track length (VETL) of the fast nuclei coming to rest inside crystals—both of fossil and “fresh” tracks—to determine the charge distribution of cosmic-ray nuclei tracks and(c) the so-called “four-zone” model of tracks in crystals (and also glasses) which provides not only the VETL track length dependence for 20Z92 nuclei but also demonstrates the regular annealing behavior of VETL of 20Z92 nuclei in a broad temperature interval.This approach was first applied in the early 1980s to investigate the “fossil” tracks due to 22Z92 cosmic-ray nuclei in olivine crystals from meteorites-pallasite Marjalahti and Eagle Station.The discovery of Th–U cosmic-ray nuclei tracks in 1980 was unambiguously confirmed by calibrations of the same crystals with ²³⁸U, ¹⁹⁷Au and ²⁰⁸Pb accelerated ions in the late 1980s. More than 1600 tracks due to cosmic-ray actinide nuclei were measured during the last two decades of the 20th century.Also, 11 anomalously long tracks (track length exceeds by a factor (1.6±0.1) the track length due to Th–U nuclei were measured. The detailed analysis shows that at least 5 of these tracks could not be attributed to the Th–U nuclei. It means that now we have a preliminary proof on the existence Z110 nuclei in cosmic-rays. The abundance is Z110/Th–U=(1–3)×10⁻³ in Z110 freshly formed cosmic-rays (time interval 10³–10⁷ years).The method proposed can provide the necessary and sufficient conditions for the discovery of Z110 nuclei in nature.     

CW- and pulsed-EPR of carbonaceous matter in primitive meteorites: solving a lineshape paradox

Insoluble organic matter (IOM) of Orgueil and Tagish Lake meteorites are studied by CW-EPR and pulsed-EPR spectroscopies. The EPR line is due to polycyclic paramagnetic moieties concentrated in defect-rich regions of the IOM, with concentrations of the order of 4x10(19) spin/g. CW-EPR reveals two types of paramagnetic defects: centres with S=1/2, and centres with S=0 ground state and thermally accessible triple state S=1. In spite of the Lorentzian shape of the EPR and its narrowing upon increasing the spin concentration, the EPR line is not in the exchange narrowing regime as previously deduced from multi-frequency CW-EPR [L. Binet, D. Gourier, Appl. Magn. Reson. 30 (2006) 207-231]. It is inhomogeneously broadened as demonstrated by the presence of nuclear modulations in the spin-echo decay. The line narrowing, similar to an exchange narrowing effect, is the result of an increasing contribution of the narrow line of the triplet state centres in addition to the broader line of doublet states. Hyperfine sublevel correlation spectroscopy (HYSCORE) of hydrogen and (13)C nuclei indicates that IOM* centres are small polycyclic moieties that are moderately branched with aliphatic chains, as shown by the presence of aromatic hydrogen atoms. On the contrary the lack of such aromatic hydrogen in triplet states suggests that these radicals are most probably highly branched. Paramagnetic centres are considerably enriched in deuterium, with D/H approximately 1.5+/-0.5x10(-2) of the order of values existing in interstellar medium.     

Study of terrestrial ages of the Antarctic meteorites with thermoluminescence

Summary The terrestrial ages of Antarctic meteorites were estimated from the thermoluminescence (TL) intensity of the fusion crust. It was found that there is a good correlation between the TL intensities and terrestrial ages which were previously measured by cosmogenic-radionuclide abundance. It was also noticed that the LT/HT value gives false terrestrial ages. The basis for establishing the TL dating techniques regarding the terrestrial ages of Antarctic meteorites is presented.     

A search for superheavy nuclei tracks in extraterrestrial olivine crystals

A study is made for the search of superheavy nuclei in Marjalahti, Eagle Station and in other pallasite olivines. The olivine crystals are calibrated for heavy ion track lengths by using heavy ion beams from cyclotrons. The calibration for ultra heavy ions which are presently not available with sufficient energy to produce volume tracks in olivine crystals, is based on Katz and Kobetich model of track formation. The length spectrum of volume tracks, revealed by puncturing them with focussed Nd-glass laser beam, is measured and the abundances of different nuclei groups are calculated. Partial annealing has been used at 430°C for 32 hr which eliminates the interfering tracks due to nuclei of atomic numberS ≤ 50. During the scanning 4 cm³ olivine crystals, about 360 long tracks of uranium group as well as two very long tracks have been found. If these tracks belong to superheavy nuclei, the relative abundance of super heavies is found to be 6 × 10⁻¹¹ in galactic cosmic rays.     

古化石与陨石的元素对比分析

古化石是古代的动植物经过漫长地质时期和地质作用形成的化石,它是地球历史的鉴证,记载着地球生态环境演变的信息;长时间遨游于太阳系中的陨石,经过宇宙间的核反应和大气的磨蚀,形成了独特的纹理与造型,记载着外太空形成演化的原始信息。古化石成分的分析是研究地球生物起源和进化的科学依据;而陨石是大自然馈赠的来自外太空的岩石样品,极为珍贵和稀少,对陨石成分的分析可以为我国外星球探测和天体化学的发展提供更好的基础。对样品的溶解方法进行选择和优化,最终以硝酸、氢氟酸、高氯酸为混合试剂,采用微波消解法溶解古化石样品;以王水、硝酸、氢氟酸、高氯酸为混合试剂,采用微波消解与湿法消解相结合溶解陨石样品,应用电感耦合等离子体原子发射光谱法(ICP-AES)测定了3种古化石样品、3种陨石样品中多种元素的含量,并将古化石与陨石中相同元素的含量进行对比。分析结果表明,古化石和陨石中都含有Pb,Hg,Ge,Fe,Ni,Cu,Co和Mn等重金属元素,以及部分稀土元素。该方法加标回收率在98.2%~106%之间,相对标准偏差均小于2.12%。方法的灵敏度高,准确度和精密度好。