Dating human skeletal remains using 90Sr and 210Pb: case studies. [Dating human skeletal remains using Sr-90 and Pb-210: Case studies]

In legal medicine, the post mortem interval (PMI) of interest covers the last 50 years. When only human skeletal remains are found, determining the PMI currently relies mostly on the experience of the forensic anthropologist, with few techniques available to help. Recently, several radiometric methods have been proposed to reveal PMI. For instance, (14)C and (90)Sr bomb pulse dating covers the last 60 years and give reliable PMI when teeth or bones are available. (232)Th series dating has also been proposed but requires a large amount of bones. In addition, (210)Pb dating is promising but is submitted to diagenesis and individual habits like smoking that must be handled carefully. Here we determine PMI on 29 cases of forensic interest using (90)Sr bomb pulse. In 12 cases, (210)Pb dating was added to narrow the PMI interval. In addition, anthropological investigations were carried out on 15 cases to confront anthropological expertise to the radiometric method. Results show that 10 of the 29 cases can be discarded as having no forensic interest (PMI>50 years) based only on the (90)Sr bomb pulse dating. For 10 other cases, the additional (210)Pb dating restricts the PMI uncertainty to a few years. In 15 cases, anthropological investigations corroborate the radiometric PMI. This study also shows that diagenesis and inter-individual difference in radionuclide uptake represent the main sources of uncertainty in the PMI determination using radiometric methods.

Cleusonite, (Pb,Sr)(U4+,U6+)(Fe2+ Zn)2(Ti,Fe2+ Fe3+)18(O,OH)38, a new mineral species of the crichtonite group from the western Swiss Alps

Cleusonite, (Pb,Sr)(U4+,U6+) (Fe2+,Zn)(2) (Ti,Fe2+,Fe3+)(18) (O,OH)(38), is a new member of the crichtonite group. It was found at two occurrences in greenschist facies metamorphosed gneissic series of the Mont Fort and Siviez-Mischabel Nappes in Valais, Switzerland (Cleuson and Bella Tolla summit), and named after the type locality. It occurs as black opaque cm-sized tabular crystals with a bright sub-metallic lustre. The crystals consist of multiple rhombohedra and hexagonal prisms that are generally twinned. Measured density is 4.74(4) g/cm(3) and can be corrected to 4.93(12) g/cm(3) for macroscopic swelling due to radiation damage; the calculated density varies from 5.02(6) (untreated) to 5.27(5) (heat-treated crystals); the difference is related to the cell swelling due to the metamictisation. The empirical formula for cleusonite from Cleuson is (Pb0.89Sr0.12)(Sigma=1.01) (U0.79+4U0.30+6)(Sigma=1.09) (Fe1.91+2Zn0.09)(Sigma=2.00) (Ti11.80Fe3.44+2Fe2.33+3V0.19+5Mn0.08Al0.07)(Sigma=17.90) [O-35.37(OH)(2.63)](Sigma=38). Cations were measured by electron microprobe, the presence of structural (OH) was confirmed by infrared spectroscopy and the U6+/U4+ and Fe2+/Fe3+ ratios were determined by X-ray photoelectron spectroscopy. Cleusonite is partly metamict, and untreated crystals only show three major X-ray diffraction peaks. Because of this radiation-damaged state, the mineral appears optically isotropic and shows a light-grey to white colour in reflected polarized light. Cleusonite is trigonal, space group R $(3) over bar $, and unit-cell parameters are varying from a = 10.576(3), c = 21.325(5) angstrom (untreated crystal) to a = 10.4188(6), c = 20.942(1) angstrom (800 degrees C treatment) and to a = 10.385(2), c = 20.900(7) angstrom (1000 degrees C treatment). The three cells give a common axial ratio 2.01 (1), which is identical to the measured morphological one 2.04(6). ne name cleusonite also applies to the previously described ``uranium-rich senaite'' from Alinci (Macedonia) and the ``plumbodavidite'' from Huanglongpu (China).

U-Pb ages of magmatic rocks of the western Austroalpine Dent-Blanche-Sesia unit

Conventional U-Pb ages on zircon and monazite demonstrate that granites and gabbros intruded during a short time span of 5 Ma between 293 and 288 Ma in several polycyclic basement units of the Western Austroalpine domain. This bimodal activity reflects increasing underplating of an upwelling mantle at the base of a thinning post-Variscan continental crust.

U-Pb and Ar-Ar geochronological data from the Pelagonian basement in Evia (Greece): geodynamic implications for the evolution of Paleotethys

High precision U-Pb zircon and Ar-40/Ar-39 mica geochronological data on metagranodiorites, metagranites and mica schists from north and central Evia island (Greece) are presented in this study. U-Pb zircon ages range from 308 to 1912 Ma, and indicate a prolonged magmatic activity in Late Carboniferous. Proterozoic ages represent inherited cores within younger crystals. Muscovite Ar-40/Ar-39 plateau ages of 288 to 297 Ma are interpreted as cooling ages of the magmatic bodies and metamorphic host rocks in upper greenschist to epidote-amphibolite metamorphic conditions. The multistage magmatism had a duration between 308 and 319 hla but some older intrusions, as well as metamorphic events, cannot be excluded. Geochemical analyses and zircon typology indicate calc-alkaline affinities for the granites of central Evia and alkaline to calc-alkaline characteristics for the metagranodiorites from the northern part of the island. The new data point towards the SE continuation, in Evia and the Cyclades, of a Variscan continental crust already recognised in northern Greece (Pelagonian basement). The Late Carboniferous magmatism is viewed as a result of northward subduction of the Paleotethys under the Eurasian margin.

Vaporization behaviour and some thermodynamic properties of the Pd-In, Pd-Pb, Pd-Sn systems

In this study, the vaporization behaviour of solid Pd-rich phases in the Pd-Pb, Pd-In and Pd-Sn systems was investigated by Knudsen-effusion-cell coupled with mass-spectrometry. The Pb, Pd, In vapor pressures [no Sn(g) has been detected in the vapor of Pd-Sn system] were evaluated in the temperatures range 1190-1563 K from the ion intensities measured over two-phases regions. Thermodynamic quantities were derived from vapor pressure data. In particular, for the Pd-Sn binary, the intermediate phase Pd7Sn2, the existence of which has been recently proposed, has been studied here for the first time. Furthermore, preliminary thermochemical data are presented for the diatomic intermetallic molecules PdSn and PdPb, which have been for the first time identified in the vapors in equilibrium over liquid solutions of appropriate composition at higher temperatures (1935-2025 K). (C) 2000 Elsevier Science Ltd. All rights reserved.

Magma generation at the easternmost section of the Hellenic arc: Hf, Nd, Pb and Sr isotope geochemistry of Nisyros and Yali volcanoes (Greece)

Geochemical and petrographical studies of lavas and ignimbrites from the Quaternary Nisyros-Yali volcanic system in the easternmost part of the Hellenic arc (Greece) reveal insight into magma generating processes. A compositional gap between 61 and 68 wt.% SiO2 is recognized that coincides with the stratigraphic distinction between pre-caldera and postcaldera volcanic units. Trace element systematics support the subdivision of Nisyros and Yali volcanic units into two distinct suites of rocks. The variation of Nd and Hf present day isotope data and the fact that they are distinct from the isotope compositions of MORB rule out an origin by pure differentiation and require assimilation of a crustal component. Lead isotope ratios of Nisyros and Yali volcanic rocks support mixing of mantle material with a lower crust equivalent. However, Sr-87/Sr-86 ratios of 0.7036-0.7048 are incompatible with a simple binary mixing scenario and give low depleted mantle extraction ages (< 0.1 Ga), in contrast with Pb model ages of 0.3 Ga and Hf and Nd model ages of ca. 0.8 Ga. The budget of fluid-mobile elements Sr and Pb is likely to be dominated by abundant hydrous fluids characterised by mantle-like Sr isotope ratios. Late stage fluids probably were enriched in CO2, needed to explain the high Th concentrations. The occurrence of hydrated minerals (e.g., amphibole) in the first post-caldera unit with the lowermost Sr-87/Sr-86 ratio of 0.7036 +/- 2 can be interpreted as the result of the increased water activity in the source. The presence of two different plagioclase phenocryst generations in the first lava subsequent to the caldera-causing event is indicative for a longer storage time of this magma at a shallower level. A model capable of explaining these observations involves three evolutionary stages. First stage, assimilation of lower crustal material by a primitive magma of mantle origin (as modelled by Nd-Hf isotope systematics). This stage ended by an interruption in replenishment that led to an increase of crystallization and, hence, an increase in viscosity, suppressing eruption. During this time gap, differentiation by fractional crystallization led to enrichment of incompatible species, especially aqueous fluids, to silica depolymerisation and to a decrease in viscosity, finally enabling eruption again in the third stage. (c) 2005 Elsevier B.V. All rights reserved.

Heat capacity measurements by differential scanning calorimetry in the Pd-Pb, Pd-Sn and Pd-ln systems

Molar heat capacities at constant pressure of six solid solutions and 11 intermediate phases in the Pd-Pb, Pd-Sn and Pd-In systems were determined each 10 K by differential scanning calorimetry from 310 to 1000 K, The experimental values have been fitted by polynomials C-p = a + bT + cT(2) + d/T-2. Results are given, discussed and compared with available literature data. (C) 2001 Elsevier Science B.V, AII rights reserved.

U-Pb isotopic dating of fluid infiltration and metasomatism during Dalradian regional metamorphism in Connemara, western Ireland

A metasomatic diopside rock occurs at the top of the dolomitic Connemara Marble Formation of western Ireland and contains titanite and K-feldspar in addition to around 90% diopside (X(Mg) = 0.90-0.97). U-Pb isotopic measurements on this mineral assemblage show that the titanite is both unusually uranium-rich and isotopically concordant, with the result that a precise U-Pb age of 478 +/- 2.5 Ma can be determined. The age is identical within error to a less precise Rb-Sr age of diopside-K-feldspar of 483 +/- 6 Ma. Petrological evidence indicates that the assemblage crystallized at c. 620-degrees-C close to or below the closure temperature of titanite. The age thus provides a precise estimate of the time of metamorphism; this age is 11 +/- 3 Ma younger than the 490 Ma age for nearby gabbroic plutons which has previously been used to constrain the peak metamorphic age. This difference accords well with geological evidence that the gabbros were emplaced prior to the metamorphic peak. Analysis of minerals with high closure temperature from assemblages whose crystallization is unambiguously associated with a specific episode of fluid infiltration at the peak of metamorphism provides the basis for a new approach to dating metamorphism. The success of this approach is demonstrated by the results from Connemara.

New Early to Middle Triassic U-Pb ages from South China: Calibration with ammonoid biochronozones and implications for the timing of the Triassic biotic recovery

New zircon U-Pb ages are proposed for late Early and Middle Triassic volcanic ash layers from the Luolou and Baifeng formations (northwestern Guangxi, South China). These ages are based on analyses of single, thermally annealed and chemically abraded zircons. Calibration with ammonoid ages indicate a 250.6 +/- 0.5 Ma age for the early Spathian Tirolites/Columbites beds, a 248.1 +/- 0.4 Ma age for the late Spathian Neopopanoceras haugi Zone, a 246.9 +/- 0.4 Ma age for the early middle Anisian Acrochordiceras hyatti Zone, and a 244.6 +/- 0.5 Ma age for the late middle Anisian Balatonites shoshonensis Zone. The new dates and previously published U-Pb ages indicate a duration of ca. 3 my for the Spathian, and minimal durations of 4.5 +/- 0.6 my for the Early Triassic and of 6.6+0.7/-0.9 my for the Anisian. The new Spathian dates are in a better agreement with a 252.6 +/- 0.2 Ma age than with a 251.4 +/- 0.3 Ma age for the Permian-Triassic boundary. These dates also highlight the extremely uneven duration of the four Early Triassic substages (Griesbachian, Dienerian, Smithian, and Spathian), of which the Spathian exceeds half of the duration of the entire Early Triassic. The simplistic assumption of equal duration of the four Early Triassic subdivisions is no longer tenable for the reconstruction of recovery patterns following the end Permian mass extinction. (c) 2006 Elsevier B.V. All rights reserved.

Characterization of lead-recycling facility emissions at various workplaces : major insights for sanitary risks assessment

Most available studies on lead smelter emissions deal with the environmental impact of outdoor particles, but only a few focus on air quality at workplaces. The objective of this study is to physically and chemically characterize the Pb-rich particles emitted at different workplaces in a lead recycling plant. A multi-scale characterization was conducted from bulk analysis to the level of individual particles, to assess the particles properties in relation with Pb speciation and availability. Process PM from various origins were sampled and then compared; namely Furnace and Refining PM respectively present in the smelter and at refinery workplaces, Emissions PM present in channeled emissions.These particles first differed by their morphology and size distribution, with finer particles found in emissions. Differences observed in chemical composition could be explained by the industrial processes. All PM contained the same major phases (Pb, PbS, PbO, PbSO4 and PbO·PbSO4) but differed on the nature and amount of minor phases. Due to high content in PM, Pb concentrations in the CaCl2 extractant reached relatively high values (40 mg.L-1). However, the ratios (soluble/total) of CaCl2 exchangeable Pb were relatively low (< 0.02%) in comparison with Cd (up to 18%). These results highlight the interest to assess the soluble fractions of all metals (minor and major) and discuss both total metal concentrations and ratios for risk evaluations. In most cases metal extractability increased with decreasing size of particles, in particular, lead exchangeability was highest for channeled emissions. Such type of study could help in the choice of targeted sanitary protection procedures and for further toxicological investigations. In the present context, particular attention is given to Emissions and Furnace PM. Moreover, exposure to other metals than Pb should be considered. [Authors]

Late Labradorian metamorphism and anorthosite-granitoid intrusion, Cape-Caribou River allochthon, Grenville Province, Labrador - Evidence from U-Pb geochronology

In the Cape Caribou River allochthon (CCRA), metaigneous and gneissic units occur as a shallowly plunging synform in the hanging wall of the Grand Lake thrust system (GLTS), a Grenvillian structure that forms the boundary between the Mealy Mountains and Groswater Bay terranes. The layered rocks of the CCRA are cut by a stockwork of monzonite dykes related to the Dome Mountain suite and by metadiabase-amphibolite dykes that probably form part of the ca. 1380 Ma Mealy swarm. The mafic dykes appear to postdate much of the development of subhorizontal metamorphic layering within the lower parts of the CCRA. The uppermost (least metamorphosed) units of the CCRA, the North West River anorthosite-metagabbro and the Dome Mountain monzonite suite, have been dated at 1625 +/- 6 and 1626 +/- 2 Ma, respectively. An amphibolite unit that concordantly underlies the anorthosite-metagabbro and is intruded discordantly by monzonite dykes has given metamorphic ages of 1660 +/- 3 and 1631 +/- 2 Ma. Granitoid gneisses that form the lowest level of the CCRA have given a migmatization age of 1622 +/- 6 Ma. The effects of Grenvillian metamorphism become apparent in the lower levels of the allochthon where gneisses, amphibolite, and mafic dykes have given new generation zircon ages of 1008 +/- 2, 1012 +/- 3, and 1011 +/- 3 Ma, respectively. A posttectonic pegmatite has also given zircon and monazite ages of 1016(-3)(+7) and 1013 +/- 3 Ma, respectively. Although these results indicate new growth of Grenvillian zircon, this process was generally not accompanied by penetrative deformation or melting. Thus, the formation of gneissic fabrics and the overall layered nature of the lower CCRA are a result primarily of Labradorian (1660-1620 Ma) tectonism and intrusion, and probably reflect early movement on an ancestral GLTS. Grenvillian heating and metamorphism (up to granulite facies) was strongly concentrated towards the base of the CCRA and probably occurred during northwestward thrusting of the allochthon over the Groswater Bay terrane.

U-Pb zircon dating in the middle Penninic basement of the Western Alps (Valais, Switzerland)

New ages (U-Pb isotopic data) on zircon and monazite in the pre-Alpine basement of the Penninic realm (Valais, Switzerland) are presented. They are related to a Variscan metamorphic high-grade event (ca. 330 Ma) and to post-Variscan magmatic activities (ca. 270 Ma).

U-Pb zircon dating of granitoids from the Dora-Maira massif (western Italian Alps)

Among the large number of granitic intrusions within the Dora-Maira massif, several main types can be distinguished. In this study we report field, petrographic and geochemical investigations as well as zircon typology and conventional U-Pb zircon dating of plutons representing these types. The main results are as follows: the Punta Muret augengneiss is a polymetamorphosed peraluminous granite of anatectic origin. It is 457 +/- 2 Ma old and represents one of the numerous Caledonian orthogneisses of the Alpine basement. All other dated granites are of Late Variscan age. The Cavour leucogranite is an evolved granite of probably calc-alkaline affiliation, dated at 304 +/- 2 Ma. The dioritic and granodioritic facies of the Malanaggio diorite (auct.) are typical calc-alkaline rocks, whose respective age of 290 +/- 2 and 288 +/- 2 Ma overlap within errors. The Sangone and Freidour granite types have very similar alkali-calcic characteristics; their ages are poorly constrained between 267-279 and 268-283 Ma, respectively. The new data for the Dora-Maira granites are in keeping with models of the overall evolution of the Late- to Post-Variscan magmatism in the Alpine area in terms of age distribution and progressive geochemical evolution towards alkaline melts. In a first approximation, granitic rocks across the Variscan belt seem to be increasingly younger towards the internal (southern) parts of the orogen. A Carboniferous, distensive Basin and Range situation is thought to be responsible for the magmatic activity. This tectonic context is comparable to the back-are opening of an active continental margin. The observed southward migration of the magmatism could be linked to the roll-back of the subducting Paleotethyan oceanic plate along the Variscan cordillera.