3,538 research outputs found
Non-traditional stable isotopes Reviews in mineralogy and geochemistry./ editors, Fang-Zhen Teng, James Watkins, Nicolas Dauphas.
No full textIn English.Includes bibliographical references.The development of multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) makes it possible to precisely measure non-traditional stable isotopes. This volume reviews the current status of non-traditional isotope geochemistry from analytical, theoretical, and experimental approaches to analysis of natural samples. In particular, important applications to cosmochemistry, high-temperature geochemistry, low-temperature geochemistry, and geobiology are discussed. This volume provides the most comprehensive review on non-traditional isotope geochemistry for students and researchers who are interested in both the theory and applications of non-traditional stable isotope geochemistry.Table of Contents ; 1. Non-Traditional Stable Isotopes: Retrospective and Prospective ; 2. Equilibrium Fractionation of Non-traditional Isotopes: a Molecular Modeling Perspective ; 3. Equilibrium Fractionation of Non-traditional Stable Isotopes: an Experimental Perspective.4. Kinetic Fractionation of Non-Traditional Stable Isotopes by Diffusion and Crystal Growth Reactions 5. In Situ Analysis of Non-Traditional Isotopes by SIMS and LA-MC-ICP-MS: Key Aspects and the Example of Mg Isotopes in Olivines and Silicate Glasses ; 6. Lithium Isotope Geochemistry.7. Magnesium Isotope Geochemistry 8. Silicon Isotope Geochemistry ; 9. Chlorine Isotope Geochemistry ; 10. Chromium Isotope Geochemistry ; 11. Iron Isotope Systematics ; 12. The Isotope Geochemistry of Ni ; 13. The Isotope Geochemistry of Zinc and Copper.14. Germanium Isotope Geochemistry 15. Selenium Isotopes as a Biogeochemical Proxy in Deep Time ; 16. Good Golly, Why Moly? The Stable Isotope Geochemistry of Molybdenum ; 17. Recent Developments in Mercury Stable Isotope Analysis.18. Investigation and Application of Thallium Isotope Fractionation 19. Uranium Isotope Fractionation ; 20. Medical Applications of Isotope Metallomics.1 online resource (902 pages
The chemistry of fine-grained terrigenous sediments reveals a chemically evolved Paleoarchean emerged crust
No full textThe nature of the rocks exposed to weathering and erosion on continents exerts an important control on weathering feedbacks and the supply of nutrients to the oceans. It also reflects the prevailing tectonic regime responsible for the formation of continents. How the chemical and lithological compositions of the continents evolved through time is, however, still a matter of debate. We use an extensive compilation of terrigenous sediment compositions to better constrain the nature of rocks at the surface of continents at 3.25 Gyr and 250 Myr ago. Specifically, we use geochemical ratios that are sensitive indicators of komatiite, mafic, and felsic rocks in the provenance of the sediments. Our results show that the average Al2O3/TiO2 ratio of fine-grained terrigenous sediments decreased slightly over time from 26.2 ± 1.3 in the Archean to 22.1 ± 1.1 (2SE) in the Phanerozoic. In contrast, in the same time interval, the average Zr/TiO2 ratio stayed nearly constant at ∼245. Considering the distinct behaviors of Al, Ti and Zr during sedimentary processes, we find that hydrodynamic mineral sorting had a minor effect on the chemical composition of Archean fine-grained sediments, but could have been more effective during periods of supercontinents. We show that the compositions of Phanerozoic sediments (Al2O3/TiO2, Zr/TiO2, La/Sc, Th/Sc, Ni/Co, Cr/Sc) are best explained with igneous rocks at the surface of continents consisting of 76 ± 8 wt% felsic, 14 ± 6 wt% Arc-basalts and 10 ± 2 wt% within-plate basalts, most likely in the form of continental flood basalts. Applying the same mass-balance calculations to the Paleoarchean suggests continental landmasses with 65 ± 7 wt% felsic, 25 ± 6 wt% mafic and 11 ± 3 wt% ultramafic rocks (all 2SE), likely in the form of komatiites. The presence of volumetrically abundant felsic rocks at the surface of continents (as evident from the sediment record) as well as at mid-crustal levels (as evident from presently exposed igneous rock record) in Paleoarchean cratons is currently best explained with the onset of subduction magmatism before 3.25 Gyr
Lunar soil record of atmosphere loss over eons
No full textThe Moon has a tenuous atmosphere produced by space weathering. The short-lived nature of the atoms surrounding the Moon necessitates continuous replenishment from lunar regolith through mechanisms such as micrometeorite impacts, ion sputtering, and photon-stimulated desorption. Despite advances, previous remote sensing and space mission data have not conclusively disentangled the contributions of these processes. Using high-precision potassium (K) and rubidium (Rb) isotopic analyses of lunar soils from the Apollo missions, our study sheds light on the lunar surface-atmosphere evolution over billions of years. The observed correlation between K and Rb isotopic ratios (δ 87Rb = 0.17 δ 41K) indicates that, over long timescales, micrometeorite impact vaporization is the primary source of atoms in the lunar atmosphere
The North is another country. by Nicolas Rothwell
No full texttag=1 data=The North is another country. by Nicolas Rothwell
tag=2 data=Rothwell, Nicolas
tag=3 data=Australian Magazine,
tag=6 data=16/17 November 1996
tag=7 data=20-33.
tag=8 data=NT%TOURISM
tag=10 data=Worse, better, stranger, wilder, but above all different from the rest of the country. Continuing his journey of discovery across Australia's Top half the author stops over in Darwin to hear all the truths and whispers about the North.
tag=11 data=1996/2/8
tag=12 data=96/0316
tag=13 data=CABWorse, better, stranger, wilder, but above all different from the rest of the country. Continuing his journey of discovery across Australia's Top half the author stops over in Darwin to hear all the truths and whispers about the North
Chemical evolution of the continental crust from a data-driven inversion of terrigenous sediment compositions
No full textThe nature of emerged continents through time is highly debated. Several studies relying on trace element data concluded that the Archaean crust was predominantly mafic, while Ti isotope systematics point to an Archaean crust that was predominantly felsic. Here, we resolve the inconsistency between these two approaches by applying a novel statistical method to a compilation of published elemental concentrations in terrigenous sediments (the OrTeS database). We use a filter based on the Local Outlier Factor to reject sediment samples that have been affected by alteration processes or mineral fractionation during transport. The nature of the emerged continents is calculated using an inverse mixing model based on a Markov Chain Monte Carlo algorithm. A procedure is presented to automatically select elemental ratios that are best suited for constraining the sediment provenance. We find that for all systems that accurately reconstruct the modern-day composition of the continents, a continuous >50% felsic contribution is required to explain the composition of fine-grained terrigenous sediments starting from 3.5 billion years ago. This finding is consistent with an early onset of plate tectonics. We estimate the geothermal gradient in the Archaean upper continental crust by tracking the reconstructed concentrations of the radiogenic heat-producing elements K, U, and Th through time. Radioactive heat production in the bulk continental crust was 50% higher in the Archaean compared to the present, resulting in a continental geothermal gradient that was about 40% higher
Titanium isotopic compositions of bulk rocks and mineral separates from the Kos magmatic suite: Insights into fractional crystallization and magma mixing processes
No full textTerrestrial and extraterrestrial rocks exhibit significant variations in their mass-dependent Ti isotopic compositions, with basalts being isotopically lighter than evolved lithologies. The observed trend from light to heavy Ti isotopic compositions from more primitive to more differentiated rocks agrees with theoretical predictions that light Ti isotopes are sequestered in Fe–Ti oxides. However, there are lingering questions about the exact extent of this fractionation and whether it is influenced by the nature of oxides and silicate melt. To improve on this matter, we measured the Ti isotopic compositions of mineral separates and bulk rocks from the calc-alkaline Kos volcano-plutonic system, Aegean arc, Greece. Bulk rock Ti isotopic compositions (δ49Ti) increase with differentiation of the magmatic system, from δ49Ti of +0.042 ± 0.033‰ in basalt to +0.654 ± 0.034‰ in rhyolite. We document two different Ti isotope trends produced by (i) fractional crystallization, and (ii) mixing between a basaltic melt and an evolved (rhyolitic) magma. Trend (i) can be explained by a melt-cumulate Ti isotopic fraction factor α of 0.9998 (i.e., the bulk cumulate is on average 0.20‰ lighter than the melt). The mineral separates reveal variable δ49Ti values, with magnetite having the lightest 49Ti/47Ti isotopic composition, biotite being intermediate and neso- and tectosilicates (i.e., olivine, plagioclase and quartz) heaviest. Comparing the TiO2 concentrations of the low-Ti minerals olivine, plagioclase and quartz determined with LA-ICP-MS and isotope dilution shows that the δ49Ti values measured in these minerals reflect their isotopic compositions, and contamination by inclusions is minimal. The difference in δ49Ti between different minerals is smallest in a basalt (Δ49Tiolivine-magnetite = +0.426) and largest in two rhyolites (Δ49Tiquartz-magnetite = +1.083; both ± 0.046‰). Our data agree with theoretical predictions that Fe–Ti oxides have a light δ49Ti signature, and neso/tectosilicate minerals are heavy. Furthermore, the measured difference in δ49Ti between magnetite-olivine, magnetite-plagioclase and magnetite-quartz agree to first order with theoretically predicted inter-mineral Ti isotopic fractionation factors, thus suggesting that the measured inter-mineral Ti isotopic variations are equilibrium in nature
Grace S. Fong, Herself an Author : Gender, Agency, and Writing in Late Imperial China, 2008
No full textZufferey Nicolas. Grace S. Fong, Herself an Author : Gender, Agency, and Writing in Late Imperial China, 2008. In: Études chinoises, n°28, 2009. Numéro spécial sur le droit chinois. pp. 243-247
New Necklaces: 400 Designs in Contemporary Jewellery
No full textAfter the successful New Rings and New Earrings, New Necklaces is the third book curated by jeweller and author Nicolas Estrada, from classic forms and materials to the most daring, experimental and surprising ideas, each of the 500 necklaces included in this book has something that makes it unique and relates strongly to today's social, cultural and artistic reality. With prefaces by German jeweller Julia Wild and Leo Caballero, owner of the Barcelona gallery Klimt 02, specialised in contemporary jewellers
How Did I Get to Princess Margaret? (And How Did I Get Her to the World Wide Web?)
No full textThe paper explores the growing use of
tools from the arts and humanities for investigation
and dissemination of social science research.
Emerging spaces for knowledge transfer, such as
the World Wide Web, are explored as outlets for
"performative social science". Questions of ethnics
and questions of evaluation which emerge from
performative social science and the use of new
technologies are discussed. Contemporary thinking
in aesthetics is explored to answer questions
of evaluation. The use of the Internet for productions
is proposed as supporting the collective
elaboration of meaning supported by Relational
Aesthetics.
One solution to the ethical problem of performing
the narrations of others is the use of the writer's
own story as autoethnography. The author queries
autoethnography's tendency to tell "sad" stories and
proposes an amusing story, exemplified by "The
One about Princess Margaret" (see Appendix).
The conclusion is reached that the free and open
environment of the Internet sidelines the usual
tediousness of academic publishing and begins to
explore new answers to questions posed about
the evaluation and ethics of performative social
science
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