Search

79th Annual Meeting of the Meteoritical-Society, Berlin, GERMANY, AUG 07-12, 2016; International audience

The objective of this study is to explore the personal and environmental causes of suicides in jails of an Italian region, by evaluating the extent of the phenomenon, in order to devise strategies for prevention. The examined documentation deals with all cases of suicide among detainees in the 14 prisons of the region Lazio between 01/01/2008 and 31/12/2014. The factors considered for evaluation concerns the are socio-demographics (age, gender, nationality) as well as legal aspects, prison characteristics (type of crime, judicial state) and method used for the suicide. The results show that the method to commit suicide in prisoners of Lazio is hanged. Suicides occur especially in Italian prisoners. Most prison inmates commit suicide less than one year before the end of the detention period. Since the majority of risk factors for suicide are present before the subject enters prison, it is not easy to observe and check the prisoners once they are in jail. The evaluation of the prisoners should be done during the phase when they first enter the jail and not after the intervening variables associated with the detention have had their effects. This suggests that further studies are necessary to better understand the phenomenon and evaluate the possibility to introduce effective preventive measures.

We determined the fission track age of Transantarctic Mountain microtektites. The plateau method yielded a formation age of 0.85 ± 0.17 Ma. This age overlaps within error with that of the catastrophic impact that produced the Australasian tektite-microtektite strewn field ca. 0.8 Ma ago. This provides further evidence that Transantarctic Mountain microtektites belong to the Australasian tektite-microtektite strewn field, as previously suggested on the basis of geochemical evidence, Sr-Nd isotope systematics and poorly resolved radiometric data.

Introduction: The Kamil crater in southern Egypt was first identified during a Google Earth survey. A closer inspection during a geophysical expedition in February 2010 not only revealed details of its structure but also identified several thousand iron meteorite specimens with a total weight of ~1.7 tons [1, 2]. The meteorite is classified as an ungrouped Ni-rich ataxite [3]. He, Ne and Ar measurements have been performed on samples from the only regmaglypted 83 kg individual as well as from a piece of the shrapnel produced during the impact [1, 2]. Experimental:We measured two samples each from the individual and the shrapnel, separated by a distance of ~1 cm in each case. Material from in between is being used for accelerator mass spectrometry of long-lived cosmogenic radionuclides. Because of instabilities in the gain of the electron multiplier, the noble gas abundances were not determined by the (standard) peak height method, but rather by isotope dilution. For that, about 1/3 of the sample gas was “spiked” with a gas mixture (3He/4He/22Ne/36Ar ~ 1.2x10-8/1.1x10-6/1.0x10-10/3.8x10-9 cc, Ne and Ar isotopic compositions atmospheric). Results: As normal for iron meteorites, noble gases are purely spallogenic. Relevant results are listed in Table 1 (concentrations in 10-8 cc/g units; uncertainties in the last digits in parentheses; I = individual, S = shrapnel). Sample 3He 4He 21Ne 38Ar I-C 147 (10) 622 (18) 1.59 (4) 9.47 (29) I-g 138 (9) 604 (20) 1.58 (4) 8.20 (34) S-C 44 (5) 214 (16) 0.42 (1) 2.39 (10) S-f 41 (5) 193 (18) 0.35 (1) 2.31 (11) Discussion: Using the model calculations of [4], we can derive bounds on the pre-atmospheric size of the object and can define a possible range of cosmic ray exposure ages. Most useful is the 4He/38Ar ratio (cf. Fig. 13 in [4]). Based on the maximum ratio of ~90 (S-C), a minimum radius for the meteoroid is ~85 cm. This implies a preatmospheric mass of >20,000 kg, in excellent agreement with the estimate of [1]. Furthermore, the shrapnel samples must originate from further inside the meteoroid than the individual (35-45 cm vs. 15-25 cm). To reach agreement between 4He/38Ar and 4He/21Ne, a sulfur / phosphorus content in the range 0.4-0.8 wt % contributing to 21Ne production is required ([4, 5; cf. Fig. 11 in [4]). Conflicting cosmic ray exposure ages, however, follow from the relation between 4He/38Ar ratio and 38Ar production rate according to [4]. While for the individual an age on the order of 400 to 500 Ma is indicated, estimates for the shrapnel samples are lower in the 200 to 300 Ma range. The discrepancy may be solved by the radionuclide measurements, which are in progress. References: [1] Folco L. et al. 2010. Science 329:804. [2] Folco L. et al. 2011. Geology 39:179-182. [3] Weisberg M. K. et al. 2010. Meteoritics & Planetary Science 45:1530-1551. [4] Ammon K. et al. 2009. Meteoritics & Planetary Science 44:485-503; in detail at: http://noblegas.unibe.ch/index.php?content=noblegas/data. [5] Ammon K. et al. 2008. Meteoritics & Planetary Science 43:685-699.

DaG 896 is an olivine-rich microporphyritic rock of komatiitic composition. Both the olivine composition (Fa17.5±2.1, [Mn/Mg] = 0.0061) and the bulk oxygen isotopic composition (delta17O = +2.55, delta180 = +3.50) indicate that DaG 896 is a sample of the H-chondrite parent body. The bulk chemistry shows an H-chondritic distribution of lithophile elements, whereas chalcophile and siderophile elements are strongly depleted, indicating formation through whole-rock melting (or nearly so) of H-chondrite material, nearly complete loss of the metal plus sulfide component, and crystallization without significant igneous fractionation. Superheated, severely shocked chondritic relics (~10 vol%), typically in the form of corroded lithic fragments 1 m h -1 during the first few hours of crystallization on asteroidal bodies of >25 km radius. The ~3.7 Ga age of DaG 896 nearly overlaps with the slightly older resetting ages of H-chondrites (all impact melts) available from the literature, indicating that the H-chondrite parent asteroid underwent extensive impact melting at the enduring of the cataclysmic bombardment of the early solar system. Such an age overlap may also indicate early disruption of the initial H-chondrite parent asteroid. The close similarity between the bulk composition and degassing age of DaG 896 and silicate inclusions in IIE iron meteorites is further evidence in support of a common origin by impact melting and metal-silicate segregation on the H-chondrite parent asteroid. Our new high-precision oxygen isotopic measurements of H-chondrites (DELTA17O = 0.77 ± 0.04) should be extended to IIEs to verify this possible petrogenetic link.

We examined 16 white opaque inclusions exposed on two polished slices of a Muong Nong-type Australasian tektite from Muong Phin, Laos. The inclusions usually consist of a core, surrounded by a froth layer, and a quartz neoblast layer. The cores are composed primarily of a mixture of silica glass, coesite, and quartz in varying proportions. A thin (up to ~4 μm) layer of SiO2-poor glass enriched in FeO, MgO, CaO, Al2O3, and TiO2 is observed as a bright halo in backscattered electron images around the quartz neoblasts and in places contains μm-sized crystals, which may be Fe,Mg-rich spinel. The distribution and textural relationships between the coesite-bearing inclusions and the tektite matrix point to an in situ formation of the coesite due to an impact, rather than to infall, from a nearby impact, into tektite melt produced by the aerial burst of a bolide. The quartz neoblasts probably formed by crystallization of silica melt squeezed out of the inclusion core during the development of the froth layer. The bright halo may be the result of silica diffusing from the adjacent tektite melt into the growing quartz neoblasts. We propose that the survival of coesite was possible due to the froth layer that acted as a heat sink during bubble expansion and then as a thermal insulator.

Kamil is a 45 m diameter impact crater identified in 2008 in southern Egypt. It was generated by the hypervelocity impact of the Gebel Kamil iron meteorite on a sedimentary target, namely layered sandstones with subhorizontal bedding. We have carried out a petrographic study of samples from the crater wall and ejecta deposits collected during our first geophysical campaign (February 2010) in order to investigate shock effects recorded in these rocks. Ejecta samples reveal a wide range of shock features common in quartz-rich target rocks. They have been divided into two categories, as a function of their abundance at thin section scale: (1) pervasive shock features (the most abundant), including fracturing, planar deformation features, and impact melt lapilli and bombs, and (2) localized shock features (the least abundant) including high-pressure phases and localized impact melting in the form of intergranular melt, melt veins, and melt films in shatter cones. In particular, Kamil crater is the smallest impact crater where shatter cones, coesite, stishovite, diamond, and melt veins have been reported. Based on experimental calibrations reported in the literature, pervasive shock features suggest that the maximum shock pressure was between 30 and 60 GPa. Using the planar impact approximation, we calculate a vertical component of the impact velocity of at least 3.5 km s � 1 . The wide range of shock features and their freshness make Kamil a natural laboratory for studying impact cratering and shock deformation processes in small impact structures.

We report the occurrence of microscopic inclusions of shocked quartz plus a Zr phase and trace of Fe oxide crystallites in Australasian microtektites recovered from deep-sea sediment cores within 2000 km of Indochina. The shocked quartz and the Zr phase are interpreted as relicts of the target rock. Furthermore, the internal homogeneity of Australasian microtektites in terms of abundance of relict mineral inclusions, vesicles, and schlieren increases with distance from Indochina. This finding strengthens the current hypothesis that the source crater of the largest and youngest tektite strewn field on Earth is located in the Indochina region, as internal heterogeneity characterizes normal impact glass found in or near the source crater. This finding also indicates that the Australasian microtektites with the longest trajectories underwent the highest temperatures or were heated longer. The definition of microtektites should include the possible occurrence of microscopic relict inclusions as an indication of proximity to the source crater.

The Frontier Mountain blue ice field is an important Antarctic meteorite trap which has yielded 472 meteorite specimens since its discovery in 1984. Remote sensing analyses and field campaigns from 1993 to 1999 have furnished new glaciological data on ice flow, ice thickness, bedrock topography, ice ablation and surface mass transport by wind, along with detailed descriptions of the field situation at the trap. This solid set of data combined with an updated meteorite distribution map and terrestrial ages available from literature allows us to better describe the nature of the concentration mechanism. In particular, we observe that the meteorite trap forms in a blue ice field (1) located upstream of an absolute and a shallow sub-ice barriers; (2) characterized by compressive ice flow with horizontal velocities decreasing from 100 to