2,272 research outputs found
Isotopes: a very short introduction
No full textAn isotope is a variant form of a chemical element, containing a different number of neutrons in its nucleus. Most elements exist as several isotopes. Many are stable while others are radioactive, and some may only exist fleetingly before decaying into other elements. In this Very Short Introduction, Rob Ellam explains how isotopes have proved enormously important across all the sciences and in archaeology. Radioactive isotopes may be familiar from their use in nuclear weapons, nuclear power, and in medicine, as well as in carbon dating. They have been central to establishing the age of the Earth and the origins of the solar system. Combining previous and new research, Ellam provides an overview of the nature of stable and radioactive isotopes, and considers their wide range of modern applications. ABOUT THE SERIES: The Very Short Introductions series from Oxford University Press contains hundreds of titles in almost every subject area. These pocket-sized books are the perfect way to get ahead in a new subject quickly. Our expert authors combine facts, analysis, perspective, new ideas, and enthusiasm to make interesting and challenging topics highly readable
Picrite-basalt associated to Ethiopian-Yemeni CFB and their relevance to mantle plume processes
No full textThe Oligocene Northern Ethiopian-Yemeni LIP, represented by a CFB plateau extending ca. 700 km in diameter, is characterized by a well-defined zonal arrangement with increasing plume-related physico-chemical features of erupted magmas, such as thermal regime, incompatible element enrichment and specific Sr-Nd-Pb-He isotopic fingerprint, from the periphery to the central plateau area [1]. Two CFB volcanic piles in the Lalibela district (Northern Ethiopia, ca. 2 km thick) and in the Manakhah section (Northern Yemeni plateau, ca. 1 km thick) which erupted close to the Oligocene Afar plume axis, are similarly characterized by very high-Titransitional basalts and picrites (HT2, [1] [2]) that account for ca. 13% (40,000 km3) of the total Ethiopian-Yemeni CFB lavas. These magmas are characterized, in addition to the extremely high TiO2content (3-6 wt%) by a high MgO content (mostly between 8 and 18 wt%), and show striking compositional analogies with those from the Karoo province and the Siberian meimechites [3] [4]. Petrological modelling based on whole rock FeO-MgO and Ol composition [5] indicates that some of picrites (MgO 16-17 wt%) are near-primary magmas with olivine phenoscrysts up to Fo 90.4. Calculation shows that the primary melts have picrite composition MgO 19.8-20.7 wt% and were generated by polybaric melting in the pressure range 3-4 GPa at a potential temperature of 1570°C. Together with high-MgO lavas from Hawaii and Gorgona, these are the highest temperatures of any OIB and LIP lavas. The available data suggest that HT2 magma sources necessarily require the involvement of specific high-Ti (and Fe) deep-seated sublithospheric components which were entrained and remobilized by the rising plume. References: [1] Beccaluva et al. (2009), J. Petrol. 50, 1377-1403. [2] Beccaluva et al. (2011), GSA Sp. Paper 478, 77-104. [3] Ellam & Cox (1991), Earth Planet. Sci. Lett. 105, 330-342. [4] Heinonen et al.(2014), Earth Planet. Sci. Lett.394, 229-241. [5] Herzberg et al. (2007), Geochem. Geophys. Geosyst. 8, doi:10.1029GC001390
Adventures of a currency trader : a fable about trading, courage, and doing the right thing / Rob Booker.
No full textIncludes index.Book fair 2012.xv, 221 pages :Praise for ADVENTURES of a CURRENCY TRADER "A truly easy, unique, and enjoyable read! Rob has done it onceagain to teach us in the funniest way possible...
how not to make themost common trading mistakes. If you are tired of reading how-tobooks, this is perfect for you. I highly recommend this book to alltraders. Everyone will learn something about themselves by readingthis book."—Kathy Lien, author, Day Trading the Currency Market,and Chief Strategist, www.dailyfx.com"Adventures of a Currency Trader is a must read foranyone who has ever traded or is thinking about trading in theForex markets. Rob Booker has a unique way of taking years ofmarket knowledge and transforming it into an educational andentertaining experience. It has quickly become a cult classic in mytrading library!"—H. Jack Bouroudjian, Principal, Brewer Investment Group"Brilliant! Rob's humor and humanity shine through in thisparable about trading and life. Filled with wisdom and wit, it's anexhilarating rollercoaster ride through the peaks and valleys ofthe learning curve, with many valuable lessons learned along theway."—Ed Ponsi, President, FXEducator.com"Rob's fable of everyman 'Harry Banes' is destined to become atrading classic. This is both the missing piece and the foundationthat comes before the strategies and methodologies. The search forthe Holy Grail begins and ends in the heart and mind. The journeyis authentic and real and if you're willing to take it with Rob,you will be rewarded in the end. Seldom has psychology and wisdombeen so entertaining!"—Raghee Horner, trader and author of Forex Trading forMaximum Profit and Days of Forex Trading"In a series of insightful and entertaining vignettes, RobBooker teaches both the novice and the experienced trader some hardwon truths about the currency market. It's a must read book writtenby a guy who survived the trenches and went on to prosper in thebiggest and most competitive financial market in the world."—Boris Schlossberg, Senior Currency Strategist, Forex CapitalMarkets LLC, and author of Technical Analysis of the CurrencyMarke
High-MgO lavas associated to CFB as indicators of plume-related thermochemical effects: the case of ultra-titaniferous picrite-basalt from the Northern Ethiopian-Yemeni plateau
No full textA comprehensive petrological and geochemical dataset is reported in order to define the thermo-compositional characteristics of Ti (Fe)-enriched picrite-basalt lavas (HT2, TiO2 3-7 wt%), erupted close to the axial zone of the inferred Afar mantle plume, at the centre of the originally continuous Ethiopian-Yemeni CFB plateau (ca. 30Ma) which is zonally arranged with progressively lower Ti basalts (HT1, TiO2 2-4 wt%; LT, TiO2 1-3 wt%) toward the periphery. Integrated petrogenetic modelling based on major and trace element analyses of bulk rocks, minerals and melt inclusions in olivines, as well as Sr-Nd-Pb-He-O isotope compositional variations enables us to make several conclusions. 1) The phase equilibria constraints indicate that HT2 primary picrites were generated at ca. 1570°C mantle potential temperatures (Tp) in the pressure range 4-5 GPa whereas the HT1 and LT primary melts formed at shallower level (< 2 to 3 GPa, Tp 1530 °C for HT1 and 1430°C for LT). Thus the Afar plume head was a thermally and compositionally zoned melting region with maximum excess temperatures of 300-350°C with respect to the ambient mantle. 2) The HT2 primary melts upwelled nearly adiabatically to the base of the continental crust (ca. 1 GPa) where fractionation of olivine, followed by clinopyroxene, led to variably differentiated picritic and basaltic magmas. 3) Trace element modelling requires that the primary HT2 melts were generated - either by fractional or batch melting (F 9-10%) - from a mixed garnet peridotite source (85%) with 15% eclogite (derived from transitional MORB protoliths included in Panafrican terranes) that has to be considered a specific Ti-Fe and incompatible element enriched component entrained by the Afar plume. 4) The LT, HT1 and HT2 lavas have 143Nd/144Nd = 0.5131-0.5128, whereas Sr-Pb isotopes are positively correlated with TiO2, varying from 87 Sr/86Sr 0.7032 and 206Pb/204Pb 18.2 in LT basalts to 87Sr/86Sr 0.7044 and 206Pb/204Pb 19.4 in HT2 picrite-basalts. High 3He/4He (15-20 RA) ratios are exclusively observed in HT2 lavas, confirming earlier evidence that these magmas require a component of deep mantle in addition to eclogite, while the LT basalts may more effectively reflect the signature of the pre-existing mantle domains. The comparison between high-MgO (13-22%) lavas from several Phanerozoic CFB provinces (Karoo, Paranà-Etendeka, Emeishan, Siberia, Deccan, North Atlantic Province) shows that they share extremely high mantle potential temperatures (Tp 1550-1700°C) supporting the view that hot mantle plumes are favoured candidates for triggering many LIPs. However, the high incompatible element and isotopic variability of these high-MgO lavas (and associated CFB) suggest that plume thermal anomalies are not necessarily accompanied by significant and specific chemical effects, which depend on the nature of mantle materials recycled during the plume rise, as well as by the extent of related mantle enrichments (if any) on the pre-existing lithospheric section
Fluid pressure cycles, variations in permeability, and weakening mechanisms along low-angle normal faults: the Tellaro detachment, Italy
No full textClassical frictional fault reactivation models indicate that slip along misoriented fault planes is not possible under most conditions. Nevertheless, active or exhumed low-angle normal faults have been described in many settings worldwide. This discrepancy is addressed by contrasting models: (1) those proposing that low-angle normal faults result from postkinematic passive rotation of former high-angle extensional faults; and (2) those proposing that specific conditions can promote slip along misoriented fault planes. This paper describes the Tellaro detachment, a mid–late Miocene low-angle normal fault that was responsible for ∼500 m of tectonic vertical thinning in the carbonate-dominated Triassic to Lower Miocene succession of the Northern Apennines, Italy. By integrating structural, petrographic, isotopic, and fluid inclusion data, we show that: (1) the main kinematic activity of the Tellaro detachment occurred between ∼8 and 4 km depths and peak temperature ∼190 °C; (2) dilational breccias, tens of cubic meters in volume, are frequently associated with major low-angle fault segments; (3) slip along misoriented planes was favored by elevated fluid pressures and low differential stress; and (4) the fault system was characterized by transient permeability pulses and overpressure buildups, associated with multiple fracturing and cementation events that caused the downward migration of master slip surfaces.
Results presented in this study show that: (1) in a fluid-active regime, continental crustal thinning can occur for shallow values of fault dip; (2) low-angle normal faults have a great influence on fluid circulation within the upper crust; and (3) episodic permeability enhancement and destruction in detachment faults can promote overpressure buildups, triggering deformation episodes
Structural architecture and palaeofluid evolution of low-angle extensional fault systems cutting through carbonate rocks within the brittle crust. The case study of the Tellaro Detachment, Northern Apennines (Italy).
No full textExperimental determination of Fe isotope fractionations in the diagenetic iron sulphide system
No full textInitial published work suggested that Fe isotope fractionations recorded in
sediments were a product of biological activity. Experiments and measurements of
natural samples now indicate that Fe isotope fractionation can be the product of both
biological and inorganic processes. Sedimentary iron sulphides provide unique
information about the evolution of early life which developed under anoxic
conditions. It is in these sedimentary Fe-S species and in particular in Archean and
Proterozoic pyrites that the largest Fe isotope variations (up to a range of ~5‰ for
δ56/54Fe) have been measured. Most research has focussed on potential processes
responsible for the formation of a 56Fe depleted Fe(II) pool from which iron
sulphides would precipitate without additional fractionation, recording the light Fe
isotope composition of the pool. Much less attention has been given to the possibility
that the iron sulphide forming mechanisms themselves could produce significant
fractionations.
The Fe-S system constitutes a diverse group of stable and metastable phases, the
ultimate Fe sequestrating phase being pyrite. The aim of this study was to examine
experimentally where Fe isotope fractionations occur during the abiotic formation of
iron sulphides in order to assess whether or not the measured Fe isotope signatures in
natural pyrite could be explained by chemical mechanisms only. Both analytical and
experimental protocols were developed in order to determine the partition of Fe
isotopes for each step towards diagenetic pyrite formation. 56/54Fe and 57/54Fe ratios
were measured on an IsoProbe-P Micromass MC-ICP-MS, and all experiments were
performed under oxygen-free N2 atmosphere.
Supporting previously published data, the results indicate that the precipitation of
the nanoparticulate iron(II) monosulphide mackinawite (FeSm) kinetically
fractionates lighter isotopes with initial fractionations of Δ56FeFe(II)aq-FeS = 1.17 ± 0.16
‰ at 25°C and Δ56FeFe(II)aq-FeS = 0.98 ± 0.16 ‰ at 2°C. The rate of isotopic exchange
between Fe(II)aq and FeSm decreases as FeSm nanoparticles grow. Fe isotope
exchange kinetics are consistent with i) FeSm nanoparticles that have a core–shell
structure, in which case Fe isotope mobility is restricted to exchange between the
surface shell and the solution and ii) a nanoparticle growth via an aggregation–
growth mechanism. Because of the structure of FeSm nanoparticles, the approach to
isotopic equilibrium is kinetically restricted at low temperatures.
The equilibrium Fe isotope fractionation between Fe2+
aq and FeSm was
determined using the three isotope method and is Δ56FeFe(II)-FeS = -0.33 ± 0.12 ‰ at
25°C and Δ56FeFe(II)-FeS = -0.52 ± 0.16 ‰ at 2°C. This suggests that at equilibrium,
FeSm incorporates heavier isotopes with respect to Fe2+
aq, and the isotopic
composition of most naturally occurring FeSm does not represent equilibrium.
During pyrite formation, pyrite incorporates kinetically lighter isotopes with a
fractionation Δ56FeFeS-pyrite ~ 2.2 ‰. Because pyrite is sparingly soluble in
sedimentary environments, isotope exchange is prevented and pyrite does not
equilibrate with its Fe(II) source. Combined fractionation factors between Fe2+
aq,
mackinawite (FeSm) and pyrite permit the generation of pyrite with Fe isotope
signatures that encapsulate the full range of sedimentary δ56Fepyrite recorded in both
Archean and modern sediments. Archean Fe isotope excursions reflect various
degrees of pyritisation, extent of Fe(II)aq utilisation, and variations in source
composition rather than microbial dissimilatory Fe(III) reduction only. Our results
show that sedimentary pyrite is not a passive recorder of the Fe isotope composition
of the reactive Fe(II) reservoir forming pyrite. It is the formation process itself that
influences pyrite Fe isotope signatures with consequent implications for the
interpretation of sedimentary pyrite Fe isotope compositions throughout geological
time
Integrated photogrammetry, lava geochemistry and palynological re-evaluation of the early evolution of the topographically constrained Mull lava field, Scotland
No full textOpen Access via the CUP Agreement The authors thank Andy Kerr, Godfrey Fitton and Rob Ellam for helpful comments and suggestions for the improvement of the original manuscript.Peer reviewe
Rob and Bert in Tokyo
No full textThis essay is steeped in contradiction: it is as much an attempt at mourning, coping, and letting go as it is an exercise in remembrance, rediscovery, and reconnection. One of the many areas of international legal scholarship where Rob Cryer left his mark is his oeuvre on the International Military Tribunal for the Far East (IMTFE). To pay tribute to, and get re-acquainted with, Rob-the-person, I re-read his 2010 article on the ‘dignified dissenter’ in Tokyo, Dutch Judge Bert Röling. In that article, Rob uses the memoranda and the opinion of Bert-the-judge to assess his conceptual and legal contributions to the IMTFE judgment. They also serve him as a vehicle to get a better grasp of the author behind the text and the values and dilemmas that shaped Röling’s positions on the IMTFE bench. What more can we learn and understand about Rob Cryer while ‘reading Rob reading Bert’? What aspects of Röling’s legacy did he choose to foreground, and what qualities did he appreciate most? How did Rob treat his character when shedding light on the more contentious elements of Röling’s work? Even if this essay fails in its therapeutic purpose, it might still add a few mosaic pieces to the collective construction of Rob’s portrait in this volume
Sub-Series 4: Publications : Affirmation and Affirmation News - Documents Found with Newsletters, 1994-1997
No full textA paper discussing the author, Rob Casteel, and his struggle with AIDS
- …
