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One of the prevailing hypotheses for the origin of the Younger Dryas (YD) cooling event is that it resulted from a bolide impact or airburst. Purported impact markers peak at or near the YD basal boundary layer at Northern Hemisphere locations. In this study, the 187Os/188Os ratios and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances in a well-dated sediment section through the Younger Dryas at the Debra L. Friedkin site, Texas are reported. Unradiogenic 187Os/188Os peaks, which could be mantle-derived or extraterrestrial, have been found above, within, and below the YD basal boundary layer. Mass balance mixing models using chondrites or iron meteorites with upper continental crust fail to duplicate the chondrite-normalized HSE patterns of the sediment samples. These HSE signatures in the Friedkin site section replicate those found in Hall’s Cave, Texas. The new results here thus independently confirm that the HSE abundances in the unradiogenic Os layers are likely a fingerprint of volcanic gas aerosols derived from large Plinian eruptions and not extra-terrestrial materials. To better constrain the lithological origins of YD sediments from the Friedkin and Hall’s Cave sites, Texas, trace elements are presented here. The rare earth elements (REE) patterns and Ir, Ni, Ti and Zr abundances are also characterized with terrestrial signatures as opposed to impact melt rocks. An age profile correlation between the two study sites, further shows that three unradiogenic Os peaks overlap in time. The results are inconsistent with the extraterrestrial hypothesis and support instead an episodic and volcanic origin for the observed geochemical anomalies at the Debra L. Friedkin and Hall’s Cave sites, Texas.

Ocean anoxic events (OAE) are characterized by increased organic content of marine sediment on a global scale with accompanying positive excursions in sedimentary organic and inorganic δ 13C values. To sustain the increased C exports and burial required to explain the C isotope excursion, increased supplies of nutrients to the oceans are often invoked during ocean anoxic events. The potential source of nutrients in these events is investigated in this study for Oceanic Anoxic Event 2, which spans the Cenomanian-Turonian boundary. Massive eruptions of one or more Large Igneous Provinces (LIPs) are the proposed trigger for OAE 2. The global warming associated with volcanogenic loading of carbon dioxide to the atmosphere has been associated with increased continental weathering rates during OAE 2, and by extension, enhanced nutrient supplies to the oceans. Seawater interactions with hot basalts at LIP eruption sites can further deliver ferrous iron and other reduced metals to seawater that can stimulate increased productivity in surface waters and increased oxygen demand in deep waters. The relative importance of continental and submarine weathering drivers of expanding ocean anoxia during OAE 2 are difficult to disentangle. In this paper, a box model of the marine Sr cycle is used to constrain the timing and relative magnitudes of changes in the continental weathering and hydrothermal Sr fluxes to the oceans during OAE 2 using a new high-resolution record of seawater 87Sr/86Sr ratios preserved in a marl-limestone succession from the Iona-1 core collected from the Eagle Ford Formation in Texas. The results show that seawater 87Sr/86Sr ratios change synchronously with Os isotope evidence for the onset of massive LIP volcanism 60 kyr before the positive C isotope excursion that traditionally marks the onset of OAE 2. The higher temporal resolution of the seawater Sr isotope record presented in this study warrants a detailed quantitative analysis of the changes in continental weathering and hydrothermal Sr inputs to the oceans during OAE 2. Using an ocean Sr box model, it is found that increasing the continental weathering Sr flux by ∼1.8-times captures the change in seawater 87Sr/86Sr recorded in the Iona-1 core. The increase in the continental weathering flux is smaller than the threefold increase estimated by studies of seawater Ca isotope changes during OAE 2, suggesting that hydrothermal forcing may have played a larger role in the development of ocean anoxic events than previously considered

Whether hydrogen incorporated in nominally anhydrous mantle minerals plays a role in the strength and longevity of the thick cratonic lithosphere is a matter of debate. In particular, the percolation of hydrogen-bearing melts and fluids could potentially add hydrogen to the mantle lithosphere, weaken its olivines (the dominant mineral in mantle peridotite), and cause delamination of the lithosphere's base. The influence of metasomatism on hydrogen contents of cratonic mantle minerals can be tested in mantle xenoliths from the Slave Craton (Canada) because they show extensive evidence for metasomatism of a layered cratonic mantle. Minerals from mantle xenoliths from the Diavik mine in the Lac de Gras kimberlite area located at the center of the Archean Slave craton were analyzed by FTIR for hydrogen contents. The 18 peridotites, two pyroxenites, one websterite and one wehrlite span an equilibration pressure range from 3.1 to 6.6 GPa and include samples from the shallow (≤145 km), oxidized ultra-depleted layer; the deeper (∼145–180 km), reduced less depleted layer; and an ultra-deep (≥180 km) layer near the base of the lithosphere. Olivine, orthopyroxene, clinopyroxene and garnet from peridotites contain 30–145, 110–225, 105–285, 2–105 ppm H2O, respectively. Within each deep and ultra-deep layer, correlations of hydrogen contents in minerals and tracers of metasomatism (for example light over heavy rare-earth-element ratio (LREE/HREE), high-field-strength-element (HFSE) content with equilibration pressure) can be explained by a chromatographic process occurring during the percolation of kimberlite-like melts through garnet peridotite. The hydrogen content of peridotite minerals is controlled by the compositions of the evolving melt and of the minerals and by mineral/melt partition coefficients. At the beginning of the process, clinopyroxene scavenges most of the hydrogen and garnet most of the HFSE. As the melt evolves and becomes enriched in hydrogen and LREE, olivine and garnet start to incorporate hydrogen and pyroxenes become enriched in LREE. The hydrogen content of peridotite increases with decreasing depth, overall (e.g., from 75 to 138 ppm H2O in the deep peridotites). Effective viscosity calculated using olivine hydrogen content for the deepest xenoliths near the lithosphere-asthenosphere boundary overlaps with estimates of asthenospheric viscosities. These xenoliths cannot be representative of the overall cratonic root because the lack of viscosity contrast would have caused basal erosion of lithosphere. Instead, metasomatism must be confined in narrow zones channeling kimberlite melts through the lithosphere and from where xenoliths are preferentially sampled. Such localized metasomatism by hydrogen-bearing melts therefore does not necessarily result in delamination of the cratonic root.

Oceanic Anoxic Event 2 (OAE-2) occurred at the Cenomanian-Turonian boundary (∼94.1 Ma) and was a time of profound global changes in ocean chemistry and the carbon cycle. This event was characterized by a positive carbon isotope excursion (CIE) caused by massive organic carbon burial, global greenhouse temperatures, ocean deoxygenation, and changes in ocean life driven by large igneous province (LIP) activity. LIPs throughout the Phanerozoic have had dynamic magma flux, with episodes of major eruptions interspersed with periods of relatively less intense eruptions. A possible trigger for LIP activity throughout the Phanerozoic has been attributed to extraterrestrial impacts because there are multiple contemporaneous occurrences of large craters, LIP activity, and mass extinctions in the geologic record. At the Cenomanian-Turonian boundary, there is a 25 km diameter (rim-to-rim) complex crater in NW Alberta, Canada known as the Steen River impact structure dated at 91 ± 7 Ma (Carrigy and Short, 1968). An alternative explanation for those craters found contemporaneous with LIP activity and mass extinctions is that they were created by large explosive events related to LIP activity. Explosive events associated with mantle plume incubation beneath cratonic lithosphere have been suggested to create geologic features commonly attributed to impacts (e.g., shocked quartz, microspherules, etc.). Currently, the trigger for LIP activity during OAE-2, as well as the duration of LIP activity and the temporal variation and magnitude of eruption rates are not well constrained. To address the issue of LIP eruption rates and the trigger for LIP activity, we examined osmium (Os) abundances and isotopes as well as highly siderophile element (HSE; for this study: Re, Ru, Pd, Os, Ir, Pt) abundance data from a continuous sedimentary section spanning OAE-2. The section is from the Eagle Ford Group in the Iona-1 core, deposited in the Cretaceous Western Interior Seaway (KWIS). We found three high Os concentration intervals with mantle-like initial Osi isotope (initial 187Os/188Os) values of ∼0.16. These intervals are interpreted to reflect high-flux LIP magmatic pulses. Between the pulses, lower Os abundances with more radiogenic Osi values of ∼0.20 are observed, which we interpret as low-flux LIP activity between the high-flux periods. This trend of high-and-low flux Os concentration pulses with mantle-like Osi values during the high flux periods is found in another KWIS core (USGS Portland #1) deposited to the north of Iona-1, and in core Deep Sea Drilling Project (DSDP) Site 530 Hole A (hereafter DSDP 530A; drilled off-shore Namibia in the Angola Basin) deposited in the Southern Hemisphere. Before and throughout the Iona-1 core OAE-2 interval, HSE abundance patterns indicate a mantle source for the unradiogenic Os, and are not consistent with an extraterrestrial impact trigger or contribution to LIP activity during OAE-2. This evidence for multiple high-flux pulses of LIP activity driving ocean deoxygenation has implications for the modern ocean, which is currently experiencing deoxygenation. These results provide new constraints on subsequent high-flux periods that extended the event. The first high-flux period started ∼60 Kyr after our selection of the onset of the CIE. The second and third high-flux periods started ∼270 and ∼400 Kyr after the onset of the CIE, respectively. After the third high-flux period, δ13Corg and Os isotope ratios shifted back to pre-excursion values over ∼585 kyr. In the Iona-1 core, OAE-2 lasted for 1.04 ± 0.12 Myr based on our selection of the CIE.

Knowing the distribution and origin of water in terrestrial planets is crucial to understand their formation, evolution and the source of their atmospheres and surface water. The nakhlites represent a suite of minimally shocked meteorites that likely originated from lava flows from a single volcano or from a shallow intrusion or sill complex on Mars. Measuring the water contents and D/H ratios of their igneous minerals allows identification of phases that have preserved their magmatic hydrogen, and therefrom permits estimation of the water content of their mantle source. Pyroxene, olivine, melt inclusions and mesostasis of five nakhlites (NWA 998, Nakhla, Y 000593, MIL 03346 and NWA 6148) were analyzed in situ for water contents and H isotopes, and major and trace element contents. No water was detected in olivine grains except in Y 000593. The water content of pyroxenes is highly heterogeneous within individual grains and between grains within a single meteorite. Water concentrations in pyroxene ( After ruling out significant influence from spallation, exchange with the martian atmosphere, shock, surface alteration, and hydrothermal processes, the H data of the pyroxenes can be explained by degassing and crystallization processes. Degassing is consistent with a decrease of water content from pyroxene interior to edge. Fractionation of H isotopes during degassing results in increases of δD during H loss from pyroxene but in decreases in δD during H2O-OH loss from a melt. Consequently, the low-water content, high-δD of most pyroxenes is best explained by degassing after the pyroxenes had crystallized. All melt and plagioclase inclusions analyzed are located in degassed pyroxenes and are also degassed. The lower δD of the mesostasis (24 ± 131‰) compared to that of the least-degassed pyroxenes (430 ± 172‰) is likely the result of melt degassing and interaction with hydrothermal fluids. Magmatic H, however, has been preserved in each nakhlite in some pyroxenes that are characterized by >15 ppm H2O and δD

The distribution of water in the upper mantle plays a crucial role in the Earth's deep water cycle, magmatism, and plate tectonics. To better constrain how these large-scale geochemical systems operate, peridotite and pyroxenite mantle xenoliths from Kilbourne Hole (KH) and Rio Puerco (RP) along the Rio Grande Rift (NM, USA) were analyzed for water, and major and trace element contents. These xenoliths sample a lithosphere whose composition was influenced by subduction and rifting, and can be used to examine the effects of melting, metasomatism, and sub-solidus equilibration on the behavior of water. The first result is that in KH xenoliths, olivines underwent negligible H loss during xenolith ascent, i.e. preserved their mantle water contents. These olivine water contents are used to calculate mantle viscosities of 0.5–184 · 1021 Pa·s. These viscosity values are more than 40 times higher than those of the asthenosphere and show that KH peridotites represent samples from the lithosphere. The preservation of olivine water contents is exceptional for off-cratonic xenoliths, and the KH peridotites provide the first estimate of the average concentration of water in Phanerozoic continental mantle lithosphere at 81 ± 30 ppm H2O. The mantle lithosphere beneath the Rio Grande rift is nevertheless heterogeneous with water contents ranging from

Obesity is a chronic and debilitating disease that has become a global epidemic. Especially severe in the Unites States, obesity currently affects almost 40% of the population. Obesity has a strong causal relationship with numerous serious comorbidities that impair quality of life, shorten life expectancy, and carry a major economic burden. Obesity has particular relevance to cardiologists because it contributes directly to several major cardiovascular diseases and, consequently, increases overall cardiovascular mortality. Multiple treatment options are available, but metabolic and bariatric surgery offers the most effective and durable treatment for obesity. Moreover, metabolic and bariatric operations alleviate and often completely eliminate numerous comorbidities, particularly type 2 diabetes and other cardiovascular risk factors, such as hypertension and dyslipidemia. With their low risk of complications and morbidity, metabolic and bariatric operations significantly improve quality of life and overall survival, particularly reducing death due to cardiovascular disease.

Ocean island basalts (OIB) exhibit significant variations in their 87Sr/86Sr, 143Nd/144Nd, 176Hf/177Hf, 186,187Os/188Os, and 206,207,208Pb/204Pb compositions that indicate contributions from multiple mantle sources. To further constrain the relationships between diverse long-lived isotopic systems in OIB, new double-spike Pb and Hf isotope data, as well as isotope dilution highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundances are reported for nineteen Icelandic picrites and basalts for which 3He/4He, 87Sr/86Sr, 143Nd/144Nd, and 186,187Os/188Os data have been reported previously (Brandon et al., 2007. GCA). Hafnium-Nd-He isotope systematics for the sample set reveal the presence of an ancient refractory source with low-3He/4He, while He-Pb isotope correlations indicate that recycled oceanic crustal components with high-3He/4He added from a less degassed mantle source are present in the Iceland plume. The highly depleted, low-3He/4He signature is sampled in the Northern and Western Volcanic Zones, likely due to higher degrees of partial melting at those localities enabling sampling of this refractory endmember. The 187Os/188Os ratios show correlations with Pb, Hf, and Nd isotope ratios indicating binary mixing between depleted and enriched sources, with no evidence for decoupling due to sulfide metasomatism. The spread of 187Os/188Os- 206,207,208Pb/204Pb data can be explained by addition of 1–11% young recycled oceanic crust to a depleted mantle source distinct from the source of Atlantic MORB. Abundances of the HSE in Northern and Western Volcanic Zone lavas overlap with those from other OIB with similar MgO contents, showing fractionated patterns that are enriched in the more incompatible Re, Pd, and Pt over the compatible Ru, Ir, and Os. Calculated parental melt HSE abundances of those lavas also overlap with those of other OIB. Eastern Volcanic Zone lavas are highly depleted in Pt and Pd relative to other Icelandic lavas. Abundances of Pt and Pd correlate with isotopic parameters, such as 206Pb/204Pb, in Icelandic lavas, indicating that the isotopically enriched endmember sampled in the Eastern Volcanic Zone is depleted in the HSE, consistent with it being mafic in nature. The abundances of MgO in the lavas also roughly correlate with isotopic parameters, supporting the identity of the depleted endmember as ultramafic and the enriched endmember as mafic. New and previously published double-spike Pb isotope data show chiefly binary mixing with an additional component present in the vicinity of the volcano Oraefajokull. Icelandic 207Pb/204Pb and 208Pb/204Pb data plot below and above the majority of Mid-Atlantic Ridge basalt data, respectively, indicating that both depleted and enriched end-members in the plume have a lower U depletion age and a higher Th/U than ambient mantle. This is consistent with the enriched and depleted end-members within the Iceland plume being

Variable proportions of isotopically diverse presolar components are known to account for nucleosynthetic isotopic anomalies for a variety of elements (e.g., Ca, Ti, Cr, Ni, Sr, Zr, Mo, Ru, Pd, Ba, Nd, and Sm) in both bulk chondrites and achondrites. However, although large Os isotopic anomalies have been measured in acid leachates and residues of unequilibrated chondrites, bulk chondrites of various groups, iron meteorites, and pallasites exhibit Os isotopic compositions that are indistinguishable from terrestrial or bulk solar isotopic abundances. Since the magnitude of nucleosynthetic anomalies is typically largest in the carbonaceous chondrites, this study reports high-precision Os isotopic compositions and highly siderophile element (HSE) concentrations for ten CK chondrites. The isotope dilution concentration data for HSE and high-precision Os isotope ratios were determined on the same digestion aliquots, to precisely correct for radiogenic contributions to 186Os and 187Os. While acid leached bulk unequilibrated carbonaceous chondrites show deficits of s-process Os components to the same extent as revealed by unequilibrated enstatite, ordinary, and Rumuruti chondrites, equilibrated bulk CK chondrites exhibit no resolvable Os isotopic anomalies. These observations support the idea that acid-resistant, carbon-rich presolar grains, such as silicon carbide (SiC) or graphite, are major carriers for nucleosynthetic isotopic anomalies of Os. The destruction of these presolar grains, which are omnipresent in unequilibrated meteorites, must have occurred during aqueous alteration and thermal metamorphism, early in the CK chondrite parent body history. The dispersal of CK chondrites along the IIIAB iron meteorite isochron on a 187Os/188Os versus 187Re/188Os diagram, with Re/Os ratios from 0.032 to 0.083, in combination with the observed redistribution of other HSE (e.g., Pt, Pd), highlights the influence of parent body processes, overprinted by effects of recent terrestrial alteration. Under the oxidizing conditions prevalent on the CK parent body, evident from high abundances of magnetite and limited Fe-Ni metal in CK chondrites, these parent body processes made all isotopically anomalous Os, originally hosted in reduced presolar grains, accessible. The absence of Os isotopic anomalies in ordinary, enstatite, and now also carbonaceous chondrites, implies that the carriers of s- and r-process Os must have been effectively homogenized across the region of chondrite formation, and possibly even the entire solar protoplanetary nebula, as suggested by the Os isotopic compositions of iron meteorites and non-anomalous ureilites. Except for a limited number of ureilites, the relative proportions of presolar s- and r-process carriers of Os (and other elements such as W) in chondrites, and most other planetary bodies, must have remained constant during all subsequent nebular and planetary processes, which appears not to have been the case for other siderophile elements, including Mo, Ru, and Pd. The existence of Mo, Ru, Pd and other siderophile element isotopic anomalies thus appears to be in part controlled by the chemical properties of these elements (e.g., volatility), their host phase(s) (e.g., SiC, graphite, metal, sulfides), and the nature of the nebular or planetary processes experienced in the early solar system.

Background Prosthetic materials wrapped around a portion of the stomach have been used to provide gastric restriction in bariatric surgery for many years. Intraluminal erosion of adjustable and nonadjustable gastric bands typically occurs many years after placement and results in various symptoms. Endoscopic management of gastric band erosion has been described and allows for optimal patient outcomes. Objectives We will describe our methods and experience with endoscopic management of intraluminal gastric band erosions after bariatric procedures. Setting University hospital in the United States. Methods A retrospective review of our bariatric surgery database identified patients undergoing removal of gastric bands. A chart review was then undertaken to confirm erosion of prosthetic material into the gastrointestinal tract. Baseline characteristics, operative reports, and follow-up data were analyzed. Results Sixteen patients were identified with an eroded gastric band: 11 after banded gastric bypass, 3 after laparoscopic adjustable gastric band (LAGB), and 2 after vertical banded gastroplasty. All patients were successfully treated with endoscopic removal of the prosthetic materials using either endoscopic scissors or ligation of the banding material with off-label use of a mechanical lithotripter device. Complications included a postoperative gastrointestinal bleed requiring repeat endoscopy, 1 patient with asymptomatic pneumoperitoneum requiring observation, and 1 with seroma at the site of LAGB port removal. Conclusions Endoscopic management of intraluminal prosthetic erosion after gastric banded bariatric procedures can be safe and effective and should be considered when treating this complication. Erosion of the prosthetic materials inside the gastric lumen allows for potential endoscopic removal without free intraabdominal perforation. Endoscopic devices designed for dividing eroded LAGBs may help standardize and increase utilization of this approach.

Lunar granulitic meteorites provide new constraints on the composition and evolution of the lunar crust as they are potentially derived from outside the Apollo and Luna landing sites. Northwest Africa (NWA) 3163, the focus of this study, and its paired stones NWA 4881 and NWA 4483, are shocked granulitic noritic anorthosites. They are petrographically and compositionally distinct from the Apollo granulites and noritic anorthosites. Northwest Africa 3163 is REE-depleted by an order of magnitude compared to Apollo granulites and is one of the most trace element depleted lunar samples studied to date. New in-situ mineral compositional data and Rb–Sr, Ar–Ar isotopic systematics are used to evaluate the petrogenetic history of NWA 3163 (and its paired stones) within the context of early lunar evolution and the bulk composition of the lunar highlands crust. The NWA 3163 protolith was the likely product of reworked lunar crust with a previous history of heavy REE depletion. The bulk feldspathic and pyroxene-rich fragments have 87Sr/86Sr that are indistinguishable and average 0.699282 ± 0.000007 (2σ). A calculated source model Sr TRD age of 4.340 ± 0.057 Ga is consistent with (1) the recently determined young FAS (Ferroan Anorthosite) age of 4.360 ± 0.003 Ga for FAS 60025, (2) 142Nd model ages for the closure of the Sm–Nd system for the mantle source reservoirs of the Apollo mare basalts (4.355–4.314 Ga) and (3) a prominent age peak in the Apollo lunar zircon record (c. 4.345 Ga). These ages are ∼100 Myr younger than predicted timescales for complete LMO crystallization (∼10 Myrs after Moon formation, Elkins-Tanton et al., 2011). This supports a later, major event during lunar evolution associated with crustal reworking due to magma ocean cumulate overturn, serial magmatism, or a large impact event leading to localized or global crustal melting and/or exhumation. The Ar–Ar isotopic systematics on aliquots of paired stone NWA 4881 are consistent with an impact event at ⩾ 3.5 Ga. This is inferred to record the event that induced granularization of NWA 3163 (and paired rocks). A later event is also recorded at ∼2 Ga by Ar–Ar isotopes is consistent with an increase in the number of impacts on the lunar surface at this time (Fernandes et al., 2013). Northwest Africa 3163 and its paired stones therefore record a c. 2.4 Gyr record of lunar crustal production, metamorphism, brecciation, impacts and eventual ejection from the lunar surface.

A major issue in the assembly of continents is the role of subduction in building and reworking the continental mantle lithosphere. Spinel lherzolite xenoliths from Dish Hill, CA represent Mojavian sub-continental lithospheric mantle (SCLM) that existed along an off-craton continental edge during late Cretaceous Farallon plate subduction. The Dish Hill locale is well situated for recording any Farallon plate influence, be it as oceanic lithosphere accretion or for its role in providing metasomatic agents to the Mojavian SCLM. The 176Hf/177Hf and 143Nd/144Nd isotopic compositions of clinopyroxenes from these xenoliths are radiogenic with eHf from +12.9 to +134.4 and eNd from +2.2 to +26.1, indicative of ancient Proterozoic melt depletion. Four out of the sixteen samples lie on a 2.1 Ga reference line for melt extraction from primitive mantle for both 176Hf/177Hf and 143Nd/144Nd, confirming their position on the 2.1 Ga 187Os/188Os aluminachron from previous work on these peridotites (Armytage et al., 2014). A second Re-depletion age obtained from an 187Os/188Os aluminachron of 1.3 Ga is also observed in the 176Lu–176Hf and 147Sm–143Nd systematics. The 176Hf/177Hf–143Nd/144Nd data from Dish Hill do not provide strong evidence for the existence of a duplex of oceanic lithosphere and SCLM, or for these peridotites being sourced from modern asthenospheric mantle upwelling after lithospheric removal. However, subchondritic 176Lu/177Hf and 147Sm/144Nd ratios and trace element compositions in some of the peridotites point to the influence of metasomatic processes. In seven of the peridotites 176Hf/177Hf ratios are not complemented by similarly radiogenic 143Nd/144Nd ratios. Such decoupling, relative to the mantle array, indicates that the 176Hf/177Hf record in these peridotites is more robust to resetting by these local metasomatic processes than 143Nd/144Nd. The 87Sr/86Sr ratios measured in these samples fall into two distinct groups based on (Ce/Yb)PM, with the less depleted 87Sr/86Sr ratios occurring in samples with (Ce/Yb)PM > 0.8, consistent with post melt extraction LREE-enrichment. Geochemical modeling of melt addition to variably depleted peridotite rules out silicate melt compositions such as MORB (mid-ocean ridge basalt) or arc basalt as primary metasomatic agents. Instead the trace element profile of the modeled melt is closest to a carbonatite melt. In particular, the melt composition is most consistent with carbonatites found in subduction zone settings rather than those associated with stable intra-plate continental lithosphere. The timing of this metasomatic event is constrained at

The 187Os/188Os compositions in peridotite samples from the sub-continental lithospheric mantle (SCLM) can be used to constrain the timing of melt extraction and potentially test the link between large-scale mantle melting and juvenile crust production. The SCLM has often experienced a complex history such that some lithophile elements such as REEs (rare earth elements) in these rocks typically record overprinting during metasomatism. New 187Os/188Os, major and trace element compositional data were obtained on sixteen Dish Hill peridotite xenoliths (California, USA) and are used to examine these issues. The samples show strong correlations between 187Os/188Os and indicators of melt depletion such as Lu abundance in clinopyroxene, modal abundance of clinopyroxene, bulk rock Al2O3 and the Cr# (Cr/(Cr + Al)) in spinel. These relationships indicate that metasomatism did not compromise the 187Os/188Os systematics. The data appear to form two melt depletion trends consistent with Re depletion model ages (TRD) obtained from the two Al2O3 versus 187Os/188Os trends are 2.1 ± 0.5 Ga and 1.3 ± 0.3 Ga (±95% conf.). It has been suggested that the SCLM under Dish Hill may be fragments of oceanic lithosphere emplaced as the result of Farallon plate subduction during the Late Cretaceous ( Luffi et al., 2009 ). However, the strong melt depletion trends, major element compositions and Re-depletion ages are not consistent with the interpretation of this suite of xenoliths having an oceanic lithospheric origin. Rather, the 2.1 Ga age coincides with Nd model ages of 2–2.3 Ga ( Bennett and DePaolo, 1987 , Ramo and Calzia, 1998 ) for the overlying Mojavia crustal province. The 1.3 Ga age is consistent with large-scale A-type magmatism in the nearby region at this time that is purported to be the result of mantle plume melting processes. Therefore, data from this study point to the SCLM under Dish Hill being formed by two ancient mantle-melting events, which could be the result of interleaving SCLM at depth. These interpretations indicate that the primary mechanism of SCLM formation under Dish Hill was through stabilization following partial melting in the convecting mantle that also results in contemporaneous juvenile crust production.

The Moon likely formed as a result of a giant impact between proto-Earth and another large body. The timing of this event and the subsequent lunar differentiation timescales are actively debated. New high-precision Nd isotope data of Apollo mare basalts are used to evaluate the Low-Ti, High-Ti and KREEP mantle source reservoirs within the context of lunar formation and evolution. The resulting models are assessed using both reported 146Sm half-lives (68 and 103 Myr). The linear relationship defined by 142Nd–143Nd systematics does not represent multi-component mixing and is interpreted as an isochron recording a mantle closure age for the Sm–Nd system in the Moon. Using a chondritic source model with present day μ142Nd of −7.3, the mare basalt mantle source reservoirs closed at 4.45−09+10 Ga (t1/2Sm146=68 Myr) or 4.39−14+16 Ga (t1/2Sm146=103 Myr). In a superchondritic, 2-stage evolution model with present day μNd142 of 0, mantle source closure ages are constrained to 4.41−08+10 (t1/2Sm146=68 Myr) or 4.34−14+15 Ga (t1/2Sm146=103 Myr). The lunar mantle source reservoir closure ages

A major change in Earth's geodynamics occurred ~3 billion years (Ga) ago, likely related to the onset of modern and continuous plate tectonics. However, the question of how Earth functioned prior to this time is poorly constrained. Here, we find a resolvable positive 142Nd anomaly in a 2.7 Ga old tholeiitic lava flow from the Abitibi Greenstone Belt indicating that early-formed mantle heterogeneities persisted at least 1.8 Ga after Earth's formation. This result contradicts the expected rapid early (~0.1 Ga), as well as the slower present-day (~1 Ga) mixing rates in the convecting mantle. Using a numerical modeling approach, we show that convective mixing is inefficient in absence of mobile-lid plate tectonics. The preservation of a 142Nd anomaly until 2.7 Ga ago can be explained if throughout the Hadean and Archean, Earth was characterized by a stagnant-lid regime, possibly with sporadic and short subduction episodes. The major change in geodynamics observed around ~3 Ga ago can then reflect the transition from stagnant-lid plate tectonics to modern mobile-lid plate tectonics. Solving the paradox of a convective but poorly-mixed mantle has implications not only for Archean Earth, but also for other planets in the solar system such as Mars.

Siderophile element concentrations were measured by LA-ICP-MS in metals and sulfides from five aubrite meteorites. Siderophile element patterns in aubrites are either similar to those in metal from enstatite chondrites, or can be derived by crystallization from metallic liquids derived by partial melting of E chondrites. Some metal grains in Mt. Egerton, Cumberland Falls, and Aubres show moderate to severe depletion in compatible highly siderophile elements (Re, Os, Ir, Ru) which are consistent with solid metal/liquid metal differentiation of enstatite chondrite-like metal. Metals from chondrite inclusions in Cumberland Falls show more extremely fractionated patterns than those from the aubritic matrix, potentially hinting at fractionation and partial melting processes affecting not only the aubrite parent body, but the chondrite body from which the inclusions were derived as well. Models using experimental partition coefficients show that aubrite metal chemically corresponds to solid metal segregated during differentiation of primary metallic liquids of EH/EL composition that contained both substantial S- and C-contents. This result is consistent with a genetic link between enstatite chondrites and aubrites, but as to whether aubrites were derived from the same body(ies) as enstatite chondrites, or have their origin in multiple, and potentially separated bodies, cannot be answered unequivocally with chemical or isotopic data alone.

Purpose The purpose of this study is to evaluate a percent change model of postoperative parathyroid hormone level in thyroidectomy patients as a predictor of hypocalcemia. Materials and methods Chart review was completed on patients who had undergone total or completion thyroidectomy over a 22-month period in our department. Only those patients with a preoperative ionized calcium and parathyroid hormone (PTH) level and at least 1 postoperative result were included. Ionized calcium levels served as an internal control. The Student t test was used to compare PTH level between the normocalcemic and hypocalcemic groups at each time point. Logistic regression analysis was used to predict hypocalcemia based on the diagnostic criteria. Receiver operator curves were used to maximize sensitivity. Results Fifty-two patients met the inclusion criteria during the study period. A total of 22 patients (42%) experienced hypocalcemia. We were unable to maximize both sensitivity and specificity at the same time point. When comparing preoperative to 6-hour postoperative PTH percent change, patients with a greater than 44% decrease are likely to have hypocalcemia, with a sensitivity of 100%. Likewise, in those patients without a greater than 44% decrease at 6 hours, early discharge can be considered safe, given the negative predictive value of 100%. Conclusion In our series, patients with a greater than 44% PTH decrease from preoperative to 6-hour postoperative are very likely to develop hypocalcemia. We would propose that these patients need further inpatient monitoring to progress to safe discharge. Likewise, patients with a less than 44% decrease at the 6-hour time point are unlikely to develop hypocalcemia and may be considered safe for discharge.

Shergottite meteorites are a suite of mafic to ultramafic igneous rocks whose parental magmas probably derived from the martian mantle. In this study, a suite of 23 shergottites, spanning their known range in bulk compositions, Rb–Sr, Sm–Nd, and Lu–Hf isotopes, were measured for 187Re–187Os isotopic systematics and highly siderophile element abundances (HSE: including Os, Ir, Ru, Pt, Pd, Re). The chief objective was to gain new insight on the chemical evolution of the martian mantle by unraveling the long-term HSE budget of its derivative melts. Possible effects upon HSEs related to crustal contamination, as well as terrestrial and/or martian surface alteration are also examined. Some of the shergottites are hot arid-desert finds. Their respective acetic acid leachates and residues show that both Re and Os display open-system behavior during sample residence at or near the martian and/or terrestrial surfaces. In some meteorites, the alteration effects can be circumvented by analysis of the leached residues. For those shergottites believed to record robust Re–Os isotopic systematics, calculated initial 187Os/188Os are well correlated with the initial 143Nd/144Nd. Shergottites from mantle sources with long-term melt-depleted characteristics (initial e143Nd of +36 to +40) have chondritic initial γ187Os ranging from −0.5 to +2.5. Shergottites with intermediate initial e143Nd of +8 to +17 have a range in initial γ187Os of −0.6 to +2.3, which overlaps the range for depleted shergottites. Shergottites from long-term enriched sources, with initial e143Nd of ∼−7, are characterized by suprachondritic γ187Os values of +5 to +15. The initial γ187Os variations for the shergottites do not show a correlation with indices of magmatic differentiation, such as MgO, or any systematic differences between hot arid-desert finds, Antarctic finds, or observed falls. The strong correlation between the initial e143Nd and γ187Os in shergottites from approximately +40 and 0 to −7 and +15, respectively, is assessed in models for mixing depleted mantle-derived melts with ancient crust (modeled to be similar to evolved shergottite in composition), and with assimilation-fractional crystallization. These models show that the correlation is unlikely to result from participation of martian crust. More likely, this correlation relates to contributions from depleted and enriched reservoirs formed in a martian magma ocean at ca. 4.5 Ga. These models indicate that the shergottite endmember sources were generated by mixing between residual melts and cumulates that formed at variable stages during solidification of a magma ocean. The expanded database for the HSE abundances in shergottites suggests that their martian mantle sources have similar HSE abundances to the terrestrial mantle, consistent with prior studies. The relatively high HSE abundances in both planetary mantles likely cannot be accounted for by high pressure–temperature metal–silicate partitioning at the bases of magma oceans, as has been suggested for Earth. If the HSE were instead supplied by late accretion, this event must have occurred prior to the crystallization of the last martian magma ocean.

Isotopic heterogeneity within the solar nebula has been a long-standing issue. Studies on primitive chondrites and chondrite components for Ba, Sm, Nd, Mo, Ru, Hf, Ti, and Os yielded conflicting results, with some studies suggesting large-scale heterogeneity. Low-grade enstatite and Rumuruti chondrites represent the most extreme ends of the chondrite meteorites in terms of oxidation state, and might thus also present extremes if there is significant isotopic heterogeneity across the region of chondrite formation. Osmium is an ideal tracer because of its multiple isotopes generated by a combination of p-, r-, and s-process and, as a refractory element; it records the earliest stages of condensation. Some grade 3–4 enstatite and Rumuruti chondrites show similar deficits of s-process components as revealed by high-precision Os isotope studies in some low-grade carbonaceous and ordinary chondrites. Enstatite chondrites of grades 5–6 have Os isotopic composition identical within error to terrestrial and solar composition. This supports the view of digestion-resistant presolar grains, most likely SiC, as the major carrier of these anomalies. Destruction of presolar grains during parent body processing, which all high-grade enstatite chondrites, but also some low-grade chondrites seemingly underwent, makes the isotopically anomalous Os accessible for analysis. The magnitude of the anomalies is consistent with the presence of a few ppm of presolar SiC with a highly unusual isotopic composition, produced in a different stellar environment like asymptotic giant branch stars (AGB) and injected into the solar nebula. The presence of similar Os isotopic anomalies throughout all major chondrite groups implies that carriers of Os isotopic anomalies were homogeneously distributed in the solar nebula, at least across the formation region of chondrites.

Objective Proton pump inhibitors (PPIs) are the mainstay of current medical management for laryngopharyngeal reflux, and treatment often involves long-term use of this class of medications. The long-term adverse effects of PPI use have not been studied extensively, but several analyses have demonstrated epidemiological links between PPI use and adverse outcomes. These include altered mineral and vitamin absorption, orthopedic injury, acute coronary syndromes (ACS), and infectious risks. Study design A PubMed search was performed for subject headings, including PPIs and adverse outcomes. Relevant studies were included in this review. Studies were compiled, reviewed, and compared in a narrative form. Results Several epidemiological links between PPI use and metabolic, infectious, cardiac, and orthopedic adverse outcomes were found. No definite causal effects were identified. Conclusion Given these epidemiological patterns, we recommend that the clinician be aware of these possible unintended consequences. In addition, we recommend consideration of dual-energy X-ray absorptiometry (DEXA) bone density scans in at-risk patients who have not been previously tested. We recommend consideration of vitamin B₁₂ and iron levels in selected patients who are at high risk. We also recommend close communication with our cardiology colleagues, as we attempt to ascertain the relationship between clopidogrel and PPI use. We recommend caution in the use of omeprazole in patients undergoing active treatment for ACS. Finally, we recommend consideration of Helicobacter pylori or serum gastrin level testing in patients with known risk factors for gastric carcinoma.

Combined 147Sm–143Nd and 176Lu–176Hf chronology of the martian meteorite Larkman Nunatak (LAR) 06319 indicates an igneous crystallization age of 193 ± 20 Ma (2σ weighted mean). The individual 147Sm–143Nd and 176Lu–176Hf internal isochron ages are 183 ± 12 Ma and 197 ± 29 Ma, respectively, and are concordant with two previously determined 147Sm–143Nd and 87Rb–87Sr internal isochron ages of 190 ± 26 Ma and 207 ± 14 Ma, respectively ( Shih et al., 2009 ). With respect to the 147Sm–143Nd isotope systematics, maskelynite lies above the isochron defined by primary igneous phases and is therefore not in isotopic equilibrium with the other phases in the rock. Non-isochronous maskelynite is interpreted to result from shock-induced reaction between plagioclase and partial melts of pyroxene and phosphate during transformation to maskelynite, which resulted in it having unsupported 143Nd relative to its measured 147Sm/144Nd ratio. The rare earth element (REE) and high field strength element (HFSE) compositions of major constituent minerals can be modeled as the result of progressive crystallization of a single magma with no addition of secondary components. The concordant ages, combined with igneous textures, mineralogy, and trace element systematics indicate that the weighted average of the radiometric ages records the true crystallization age of this rock. The young igneous age for LAR 06319 and other shergottites are in conflict with models that advocate for circa 4.1 Ga crystallization ages of shergottites from Pb isotope compositions, however, they are consistent with updated crater counting statistics indicating that young volcanic activity on Mars is more widespread than previously realized ( Neukum et al., 2010 ).

Background: Diminished dopaminergic neurotransmission contributes to decreased reward and negative eating behaviors in obesity. Bariatric surgery is the most effective therapy for obesity and rapidly reduces hunger and improves satiety through unknown mechanisms. We hypothesized that dopaminergic neurotransmission would be enhanced after Roux-en-Y-Gastric Bypass (RYGB) and Vertical Sleeve Gastrectomy (VSG) surgery and that these changes would influence eating behaviors and contribute to the positive outcomes from bariatric surgery. Methods: Five females with obesity were studied preoperatively and at ∼ 7 weeks after RYGB or VSG surgery. Subjects underwent positron emission tomography (PET) imaging with a dopamine type 2 (DA D2) receptor radioligand whose binding is sensitive to competition with endogenous dopamine. Regions of interest (ROI) relevant to eating behaviors were delineated. Fasting enteroendocrine hormones were quantified at each time point. Results: Body weight decreased as expected after surgery. DA D2 receptor availability decreased after surgery. Regional decreases (mean ± SEM) were caudate 10 ± 3%, putamen 9 ± 4%, ventral striatum 8 ± 4%, hypothalamus 9 ± 3%, substantia nigra 10±2%, medial thalamus 8±2%, and amygdala 9 ± 3%. These were accompanied by significant decreases in plasma insulin (62%) and leptin (41%). Conclusion: The decreases in DA D2 receptor availability after RYGB and VSG most likely reflect increases in extracellular dopamine levels. Enhanced dopaminergic neurotransmission may contribute to improved eating behavior (e.g. reduced hunger and improved satiety) following these bariatric procedures.

The Larkman Nunatak (LAR) 06319 olivine-phyric shergottite is composed of zoned megacrysts of olivine (Fo 76–55 from core to rim), pyroxene (from core to rim En 70 Fs 25 Wo 5 , En 50 Fs 25 Wo 25 , and En 45 Fs 45 Wo 10 ), and Cr-rich spinel in a matrix of maskelynite (An 52 Ab 45 ), pyroxene (En 30–40 Fs 40–55 Wo 10–25 ,), olivine (Fo 50 ), Fe–Ti oxides, sulfides, phosphates, Si-rich glass, and baddeleyite. LAR 06319 experienced equilibration shock pressures of 30–35 GPa based on the presence of localized shock melts, mechanical deformation of olivine and pyroxene, and complete transformation of plagioclase to maskelynite with no relict birefringence. The various phases and textures of this picritic basalt can be explained by closed system differentiation of a shergottitic melt. Recalculated parent melt compositions obtained from melt inclusions located in the core of the olivine megacrysts (Fo >72 ) resemble those of other shergottite parent melts and whole-rock compositions, albeit with a lower Ca content. These compositions were used in the MELTS software to reproduce the crystallization sequence. Four types of spinel and two types of ilmenite reflect changes in oxygen fugacity during igneous differentiation. Detailed oxybarometry using olivine-pyroxene-spinel and ilmenite-titanomagnetite assemblages indicates initial crystallization of the megacrysts at 2 log units below the Fayalite-Magnetite-Quartz buffer (FMQ – 2), followed by crystallization of the groundmass over a range of FMQ – 1 to FMQ + 0.3. Variation is nearly continuous throughout the differentiation sequence. LAR 06319 is the first member of the enriched shergottite subgroup whose bulk composition, and that of melt inclusions in its most primitive olivines, approximates that of the parental melt. The study of this picritic basalt indicates that oxidation of more than two log units of FMQ can occur during magmatic fractional crystallization and ascent. Some part of the wide range of oxygen fugacities recorded in shergottites may consequently be due to this process. The relatively reduced conditions at the beginning of the crystallization sequence of LAR 06319 may imply that the enriched shergottite mantle reservoir is slightly more reduced than previously thought. As a result, the total range of Martian mantle oxygen fugacities is probably limited to FMQ − 4 to − 2. This narrow range could have been generated during the slow crystallization of a magma ocean, a process favored to explain the origin of shergottite mantle reservoirs.

Here we search for evidence of the existence of a sub-chondritic 142Nd/144Nd reservoir that balances the Nd isotope chemistry of the Earth relative to chondrites. If present, it may reside in the source region of deeply sourced mantle plume material. We suggest that lavas from Hawai’i with coupled elevations in 186Os/188Os and 187Os/188Os, from Iceland that represent mixing of upper mantle and lower mantle components, and from Gough with sub-chondritic 143Nd/144Nd and high 207Pb/206Pb, are favorable samples that could reflect mantle sources that have interacted with an Early-Enriched Reservoir (EER) with sub-chondritic 142Nd/144Nd. High-precision Nd isotope analyses of basalts from Hawai’i, Iceland and Gough demonstrate no discernable 142Nd/144Nd deviation from terrestrial standards. These data are consistent with previous high-precision Nd isotope analysis of recent mantle-derived samples and demonstrate that no mantle-derived material to date provides evidence for the existence of an EER in the mantle. We then evaluate mass balance in the Earth with respect to both 142Nd/144Nd and 143Nd/144Nd. The Nd isotope systematics of EERs are modeled for different sizes and timing of formation relative to e143Nd estimates of the reservoirs in the μ142Nd = 0 Earth, where μ142Nd is ((measured 142Nd/144Nd/terrestrial standard 142Nd/144Nd)−1 * 10−6) and the μ142Nd = 0 Earth is the proportion of the silicate Earth with 142Nd/144Nd indistinguishable from the terrestrial standard. The models indicate that it is not possible to balance the Earth with respect to both 142Nd/144Nd and 143Nd/144Nd unless the μ142Nd = 0 Earth has a e143Nd within error of the present-day Depleted Mid-ocean ridge basalt Mantle source (DMM). The 4567 Myr age 142Nd–143Nd isochron for the Earth intersects μ142Nd = 0 at e143Nd of +8 ± 2 providing a minimum e143Nd for the μ142Nd = 0 Earth. The high e143Nd of the μ142Nd = 0 Earth is confirmed by the Nd isotope systematics of Archean mantle-derived rocks that consistently have positive e143Nd. If the EER formed early after solar system formation (0–70 Ma) continental crust and DMM can be complementary reservoirs with respect to Nd isotopes, with no requirement for significant additional reservoirs. If the EER formed after 70 Ma then the μ142Nd = 0 Earth must have a bulk e143Nd more radiogenic than DMM and additional high e143Nd material is required to balance the Nd isotope systematics of the Earth.

High-precision Pt–Re–Os and Sm–Nd isotope and highly siderophile element (HSE) and rare earth element (REE) abundance data are reported for two 2.7 b.y. old komatiite lava flows, Tony’s flow (TN) from the Belingwe greenstone belt, Zimbabwe, and the PH-II flow (PH) from Munro Township in the Abitibi greenstone belt, Canada. The emplaced lavas are calculated to have contained 25% (TN) and 28% (PH) MgO. These lavas were derived from mantle sources characterized by strong depletions in highly incompatible lithophile trace elements, such as light REE (Ce/ SmN = 0.64 ± 0.02 (TN) and 0.52 ± 0.01 (PH), e 143 Nd(T) = +2.9 ± 0.2 in both sources). 190 Pt– 186 Os and 187 Re– 187 Os isochrons generated for each flow yield ages consistent with respective emplacement ages obtained using other chronometers. The calculated precise initial 186 Os/ 188 Os = 0.1198318 ± 3 (TN) and 0.1198316 ± 5 (PH) and 187 Os/ 188 Os = 0.10875 ± 17 (TN) and 0.10873 ± 15 (PH) require time-integrated 190 Pt/ 188 Os and 187 Re/ 188 Os of 0.00178 ± 11 and 0.407 ± 8 (TN) and 0.00174 ± 18 and 0.415 ± 5 (PH). These parameters, which by far represent the most precise and accurate estimates of time-integrated Pt/Os and Re/Os of the Archean mantle, are best matched by those of enstatite chondrites. The data also provide evidence for a remarkable similarity in the composition of the sources of these komatiites with respect to both REE and HSE. The calculated absolute HSE abundances in the TN and PH komatiite sources are within or slightly below the range of estimates for the terrestrial Primitive Upper Mantle (PUM). Assuming a chondritic composition of the bulk silicate Earth, the strong depletions in LREE, yet chondritic Re/Os in the komatiite sources are apparently problematic because early Earth processes capable of fractionating the LREE might also be expected to fractionate Re/Os. This apparent discrepancy could be reconciled via a two-stage model, whereby the moderate LREE depletion in the sources of the komatiites initially occurred within the first 100 Ma of Earth’s history as a result of either global magma ocean differentiation or extraction and subsequent long-term isolation of early crust, whereas HSE were largely added subsequently via late accretion. The komatiite formation, preceded by derivation of basaltic magmas, was a result of second-stage, largedegree dynamic melting in mantle plumes. 2009 Elsevier Ltd. All rights reserved.

The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Mars-sized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the Earth. Two recent studies to obtain high-precision 142Nd/144Nd ratios of lunar mare basalts yielded contrasting results. In one study, after correction of neutron fluence effects imparted to the Nd isotope compositions of the samples, the coupled 142Nd–143Nd systematics were interpreted to be consistent with a bulk Moon having a chondritic Sm/Nd ratio [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science 312, 1369–1372]. The other study found that their data on the same and similar lunar mare basalts were consistent with a bulk Moon having a superchondritic Sm/Nd ratio [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett. 262, 505–516]. Delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the Moon and for constraining the types of materials available for accretion into large terrestrial planets such as Earth. To further examine this issue, the same six lunar mare basalt samples measured in Rankenburg et al. [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science 312, 1369–1372] were re-measured for high-precision Nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than ±3 ppm (2σ) for 142Nd/144Nd ratios. The measurements were repeated in a distinct second analytical campaign to further test their reproducibility. Evaluation of accuracy and neutron fluence corrections indicates that the multidynamic Nd isotope measurements in this study and the 3 in Boyet and Carlson [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett. 262, 505–516] are reproducible, while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk Moon with either chondritic or superchondritic Sm/Nd ratios. The multidynamic data are best explained by a bulk Moon with a superchondritic Sm/Nd ratio that is similar to the present-day average for depleted MORB. Hafnium isotope data were collected on the same aliquots measured for their 142Nd/144Nd isotope ratios in order to assess if the correlation line for 142Nd–143Nd systematics reflect mixing processes or times at which lunar mantle sources formed. Based on the combined 142Nd–143Nd–176Hf obtained we conclude that the 142Nd–143Nd correlation line measured in this study is best interpreted as an isochron with an age of 229+24−20Ma after the onset of nebular condensation. The uncertainties in the data permit the sources of these samples to have formed over a 44 Ma time interval. These new results for lunar mare basalts are thus consistent with a later Sm–Nd isotope closure time of their source regions than some recent studies have postulated, and a superchondritic bulk Sm/Nd ratio of the Moon and Earth. The superchondritic Sm/Nd signature was inherited from the materials that accreted to make up the Earth–Moon system. Although collisional erosion of crust from planetesimals is favored here to remove subchondritic Sm/Nd portions and drive the bulk of these bodies to superchondritic in composition, removal of explosive basalt material via gravitational escape from such bodies, or chondrule sorting in the inner solar system, may also explain the compositional features that deviate from average chondrites that make up the Earth–Moon system. This inferred superchondritic nature for the Earth similar to the modern convecting mantle means that there is no reason to invoke a missing, subchondritic reservoir to mass balance the Earth back to chondritic for Sm/Nd ratios. However, to account for the subchondritic Sm/Nd ratios of continental crust, a second superchondritic Sm/Nd mantle reservoir is required.

New measurements of Os, He, Sr and Nd isotopes, along with major and trace elements, are presented for basalts from the three volcanic flank zones in Iceland and from Jan Mayen Island. The 187Os/188Os ratios in lavas with 30 ppt Os (n = 17) range between 0.12117 and 0.13324. These values are surprisingly low for oceanic island basalts and include some samples that are less than putative present-day primitive upper mantle (PUM with 187Os/188Os of 0.1296). These low 187Os/188Os preclude significant shallow-level contamination from oceanic crust. The 187Os/188Os ratios for Jan Mayen lavas are less than PUM, severely limiting the presence of any continental crust in their mantle source. A positive correlation between 143Nd/144Nd and 187Os/188Os ratios in Iceland and Jan Mayen lavas likely reflects the presence in their source of ancient subcontinental lithosphere that has undergone incompatible trace element enrichment that did not affect the Re–Os system. In addition, the Jan Mayen lava isotopic signature cannot be explained solely by the presence of subcontinental lithospheric mantle, and the influence of another geochemical component, such as a mantle plume appears required. Combined 87Sr/86Sr, 143Nd/144Nd, 3He/4He and 187Os/188Os data indicate a genetic relationship between Jan Mayen Island and the Iceland mantle plume. Material from the Iceland mantle plume likely migrates at depth until it reaches the tensional setting of the Jan Mayen Fracture Zone, where it undergoes low-degree partial melting. At a first-order, isotopic co-variations can be interpreted as broadly binary mixing curves between two primary end-members. One end-member, characterized in particular by its unradiogenic 187Os/188Os and 143Nd/144Nd, low 3He/4He and high 87Sr/86Sr, is represented by subcontinental lithospheric mantle stranded and disseminated in the upper mantle during the opening of the Atlantic Ocean. The second end-member corresponds to a hybrid mixture between the depleted-MORB mantle and the enriched Iceland mantle plume, itself resulting from mixing between recycled oceanic crust and depleted lower mantle. This hybrid accounts for the high 3He/4He (∼28 Ra), high 143Nd/144Nd (∼0.5132), high 187Os/188Os (∼0.14) and low 87Sr/86Sr (∼0.7026) composition observed in Iceland. Two different models may account for these observed mixing relationships between the end-members. In this first model, the Iceland mantle entrains pristine depleted material when rising in the upper mantle and allows refractory sub-lithospheric fragments to melt because of excess heat derived from the deep plume material. A second model that may better account for the Pb isotopic variations observed, uses the same components but where the depleted-MORB mantle is already polluted by subcontinental lithospheric mantle material before mixing with the Iceland mantle plume. Both cases likely occur. Though only three principal components are required to explain the isotopic variations of the Iceland–Jan Mayen system, the different possible mixing relationships may be accounted for by potentially a greater number of end-members.

The abundances of the highly siderophile elements (HSE) Ru, Pd, Re, Os, Ir, and Pt were determined by isotope dilution mass spectrometry for 22 ureilite bulk rock samples, including monomict, augite-bearing, and polymict lithologies. This report adds significantly to the quantity of available Pt and Pd abundances in ureilites, as these elements were rarely determined in previous neutron activation studies. The CI-normalized HSE abundance patterns of all ureilites analyzed here except ALHA 81101 show marked depletions in the more volatile Pd, with CI chondrite-normalized Pd/Os ratios (excluding ALHA 81101) averaging 0.19 ± 0.23 (2 σ ). This value is too low to be directly derived from any known chondrite group. Instead, the HSE bulk rock abundances and HSE interelement ratios in ureilites can be understood as physical mixtures of two end member compositions. One component, best represented by sample ALHA 78019, is characterized by superchondritic abundances of refractory HSE (RHSE—Ru, Re, Os, Ir, and Pt), but subchondritic Pd/RHSE, and is consistent with residual metal after extraction of a S-bearing metallic partial melt from carbonaceous chondrite-like precursor materials. The other component, best represented by sample ALHA 81101, is RHSE-poor and has HSE abundances in chondritic proportions. The genesis of the second component is unclear. It could represent regions within the ureilite parent body (UPB), in which metallic phases were completely molten and partially drained, or it might represent chondritic contamination that was added during disruption and brecciation of the UPB. Removal of carbon-rich melts does not seem to play an important role in ureilite petrogenesis. Removal of such melts would quickly deplete the ureilite precursors in Re/Os and As/Au, which is inconsistent with measured osmium isotope abundances, and also with literature As/Au data for the ureilites. Removal of 26 Al during silicate melting may have acted as a switch that turned off further metal extraction from ureilite source regions.

This research examines the relationship between disabilities in families and returns to welfare. Past studies of welfare recidivism have long theorized that disabilities played a central role in returns to welfare among former recipients, but lacked data to test the hypothesis. Hypothesis tests support the theory that both child and maternal disabilities, which act as barriers to self-sufficiency, increase rates of TANF re-entry and SSI entry. We show that because past studies did not account for disabilities on the odds of returning to welfare, effects of work, number of children, and past receipt of TANF are somewhat overstated. Our findings add to the literature on welfare recidivism and have implications for welfare reforms that emphasize work and lifetime limits on benefits.

Chemical heterogeneities in the Martian mantle are believed to result from the crystallization of a magma ocean in the first 100 million years of its history. Shergottite meteorites from Mars are thought to retain a compositional record of such early differentiation and the resulting mineralogy at different depths. The coupled 176 Lu– 176 Hf and 147 Sm– 143 Nd isotope systematics in 9 shergottites are used here to investigate these issues. Three compositional groups in the shergottites display distinct isotope systematics. One group, commonly termed as depleted, is characterized by positive ɛ 176 Hf i from + 46.2 to + 50.4 and ɛ 143 Nd i from + 36.2 to + 39.1. Another, termed as enriched, has negative ɛ 176 Hf i = − 16.5 to − 13.2 and ɛ 143 Nd i = − 7.0 to − 6.5. The third group is intermediate between the depleted and enriched groups with positive ɛ 176 Hf i = + 30.0 to + 33.4 and ɛ 143 Nd i = + 16.9. Together, they describe mixing curves between 176 Hf/ 177 Hf, 143 Nd/ 144 Nd, Lu/Hf, and Sm/Nd, implying that they sample two distinct sources in the Martian mantle. All shergottites are characterized by (Sm/Nd) source sample , but (Lu/Hf) source > (Lu/Hf) sample . This decoupling can be explained by two successive partial melting episodes in the depleted shergottite source and localized in the Martian upper mantle. The genesis of shergottites can be modeled using non-modal equilibrium partial melting in a source initially composed of 60% olivine, 21% clinopyroxene, 9% orthopyroxene, and 10% garnet, with degrees of partial melting of 8.8% and 3.9%, respectively, for the two successive events. The enriched end-member of the shergottite mixing curve is best modeled by late-stage quenched residual melt resulting from the crystallization of a magma ocean. The depleted shergottite source may be modeled as a mixture of cumulates and residual melt, as convection in the Martian magma ocean is expected to reduce the incompatible trace element heterogeneity in the final solidified layers. Consequently, equilibrium crystallization is preferred to model the crystallization of the Martian magma ocean. The models that best explain the shergottite data are those where the magma ocean is at a depth of at least 1350 km in Mars.

Mantle plumes are commonly perceived to have both a chemical and dynamic link with the subduction of ocean crust into the mantle. In principle, this should lead to the observation of chemical and isotopic signatures that are characteristic of ocean crust and marine sediments in ocean island basalts. This study investigates the thallium (Tl) isotope systematics of lavas from Iceland and the Azores archipelago, in order to determine if their compositions were affected by admixing of ferromanganese sediments or upper ocean crust altered at low temperature. Such materials are known to display strongly fractionated Tl isotope signatures relative to the ambient upper mantle. Two samples from the island of Terceira in the Azores archipelago have Tl isotope compositions significantly different from normal mantle, and this suggests the presence of Fe–Mn sediments. Combined Pb and Tl isotope modelling indicates that the Tl anomalies are not a feature of the Azores plume but produced by assimilation of modern Fe–Mn sediments during magma ascent through the ocean crust. Excluding these two anomalous lavas from Terceira, the Iceland and Azores samples have identical Tl isotope compositions, with an overall mean of ɛ205Tl = − 1.5 ± 1.4 (2SD, n = 30) that is indistinguishable from the previously estimated upper mantle average (ɛ205Tl = − 2.0 ± 0.5). The near-constant Tl isotope compositions of the Iceland and Azores lavas may indicate that the respective mantle plume sources contain virtually no Fe–Mn sediments or altered upper ocean crust. Alternatively, it is possible that the lack of Tl isotope variation reflects quantitative removal of fractionated Tl from the slab during subduction and dehydration. A less straightforward explanation is that past marine environments produced sediments and altered marine basalts with nearly unfractionated Tl isotope compositions. All three scenarios have important implications and future Tl isotope studies will be able to identify the most feasible interpretation.

Picrites from the neovolcanic zones in Iceland display a range in 187Os/188Os from 0.1297 to 0.1381 (γOs = + 2.1 to +8.7) and uniform 186Os/188Os of 0.1198375 ± 32 (2σ). The value for 186Os/188Os is within uncertainty of the present-day value for the primitive upper mantle of 0.1198398 ± 16. These Os isotope systematics are best explained by ancient recycled crust or melt enrichment in the mantle source region. If so, then the coupled enrichments displayed in 186Os/188Os and 187Os/188Os from lavas of other plume systems must result from an independent process, the most viable candidate at present remains core–mantle interaction. While some plumes with high 3He/4He, such as Hawaii, appear to have been subjected to detectable addition of Os (and possibly He) from the outer core, others such as Iceland do not. A positive correlation between 187Os/188Os and 3He/4He from 9.6 to 19 Ra in Iceland picrites is best modeled as mixtures of 1 Ga or older ancient recycled crust mixed with primitive mantle or incompletely degassed depleted mantle isolated since 1–1.5 Ga, which preserves the high 3He/4He of the depleted mantle at the time. These mixtures create a hybrid source region that subsequently mixes with the present-day convecting MORB mantle during ascent and melting. This multistage mixing scenario requires convective isolation in the deep mantle for hundreds of million years or more to maintain these compositionally distinct hybrid sources. The 3He/4He of lavas derived from the Iceland plume changed over time, from a maximum of 50 Ra at 60 Ma, to approximately 25–27 Ra at present. The changes are coupled with distinct compositional gaps between the different aged lavas when 3He/4He is plotted versus various geochemical parameters such as 143Nd/144Nd and La/Sm. These relationships can be interpreted as an increase in the proportion of ancient recycled crust in the upwelling plume over this time period. The positive correlation between 187Os/188Os and 3He/4He demonstrates that the Iceland lava He isotopic compositions do not result from simple melt depletion histories and consequent removal of U and Th in their mantle sources. Instead their He isotopic compositions reflect mixtures of heterogeneous materials formed at different times with different U and Th concentrations. This hybridization is likely prevalent in all ocean island lavas derived from deep mantle sources.

Using the Australian Time Use survey (TUS), this study examined time allocation among working parents raising children with disabilities. Findings showed that raising children with disabilities reduced the time working mothers had for leisure activities, but increased the time for socializing activities. Consistent with the literature, the latter effect probably reflects the special need of working mothers raising children with disabilities for strong social networks offering regular support. While a mother's time for personal care was reduced by a child with a disability, a father's time for personal care was unaffected. Thus, mothers were relatively more disadvantaged than fathers in terms of total time for themselves. This study offers new knowledge on the impact of childhood disability on working parents' time for personal care and leisure, activities that can improve their psychological and physical well-being.

Separation of a metal-rich core strongly depleted the silicate portion of the Earth in highly siderophile elements (HSE), including Pt, Re, and Os. To address the issues of how early differentiation, partial melting, and enrichment processes may have affected the relative abundances of the HSE in the upper mantle, 187 Os/ 188 Os and 186 Os/ 188 Os data for chondrites are compared with data for Os-rich alloys from upper mantle peridotites. Given that 187 Os and 186 Os are decay products of 187 Re and 190 Pt, respectively, these ratios can be used to constrain the long-term Re/Os and Pt/Os of mantle reservoirs in comparison to chondrites. Because of isotopic homogeneity, H-group ordinary and other equilibrated chondrites may be most suitable for defining the initial 186 Os/ 188 Os of the solar system. The 186 Os/ 188 Os ratios for five H-group ordinary chondrites range only from 0.1198384 to 0.1198408, with an average of 0.1198398 ± 0.0000016 (2 σ ). Using the measured Pt/Os and 186 Os/ 188 Os for each chondrite, the calculated initial 186 Os/ 188 Os at 4.567 Ga is 0.1198269 ± 0.0000014 (2 σ ). This is the current best estimate for the initial 186 Os/ 188 Os of the bulk solar system. The mantle evolution of 186 Os/ 188 Os can be defined via examination of mantle-derived materials with well-constrained ages and low Pt/Os. Two types of mantle-derived materials that can be used for this task are komatiites and Os-rich alloys. The alloys are particularly valuable in that they have little or no Re or Pt, thus, when formed, evolution of both 187 Os/ 188 Os and 186 Os/ 188 Os ceases. Previously published results for an Archean komatiite and new results for Os-rich alloys indicate that the terrestrial mantle evolved with Pt–Os isotopic systematics that were indistinguishable from the H-group ordinary and some enstatite chondrites. This corresponds to a Pt/Os of 2.0 ± 0.2 for the primitive upper mantle evolution curve. This similarity is consistent with previous arguments, based on the 187 Os/ 188 Os systematics and HSE abundances in the mantle, for a late veneer of materials with chondritic bulk compositions controlling the HSE budget of the upper mantle. It is very unlikely that high pressure metal–silicate segregation leading to core formation can account for the elemental and isotopic compositions of HSE in the upper mantle.

Komatiite samples from the 2.8-Ga Kostomuksha greenstone belt in the Baltic Shield define Pt–Os and Re–Os isochrons with ages of 2816 ± 190 and 2880 ± 83 Ma, respectively. The mean initial 186Os / 188Os and 187Os / 188Os ratios calculated at T = 2821 Ma are 0.1198341 ± 7 and 0.11042 ± 69 (γ187Os = + 2.5 ± 0.6), respectively. This Os isotopic composition characterizes that of the source of the Kostomuksha komatiite and is 53 ± 6 ppm and 2.5 ± 0.6% more radiogenic in 186Os/188Os and 187Os/188Os, respectively, than the putative contemporary convecting mantle. The coupled 186Os–187Os enrichment cannot be the result of incorporation of the material of aged recycled oceanic crust into the source of the plume, as five to six times more crustal component is required to create the 186Os-enrichment than the 187Os-enrichment observed. Moreover, the radiogenic 186Os / 188Os ratio combined with the subchondritic Pt/Os in this source calculated from the HSE abundance data is inconsistent with any model of Os isotopic evolution that involves crustal recycling, as these models require substantially suprachondritic Pt/Os in the hybrid sources. The coupled 186Os–187Os enrichment in the source of the Kostomuksha komatiite is best explained via derivation of most of the Os from the outer core. This is most consistent with the Kostomuksha komatiites originating from a mantle plume that arose from the core–mantle boundary (CMB). If this interpretation is correct, the data provide minimum constraints on the 186Os / 188Os and 187Os / 188Os ratios of the outer core at 2.8 Ga. The existing models of core crystallization based on experimentally determined solid metal–liquid metal partition coefficients for Pt, Re, and Os can adequately explain the Os isotopic composition of the Kostomuksha mantle source, although require the onset of inner core crystallization several hundred million years prior to formation of the Kostomuksha plume. Based on thermodynamic models, such an early onset of inner core crystallization would require a relatively low heat flux across the CMB of ∼3 TW and the presence of > 100 ppm K in the core. The results of this study combined with the HSE abundance data for the source of komatiites at Kostomuksha indicate that core–mantle interaction, at least in this instance, could occur in the form of isotopic exchange without significant mass transfer from the core to the mantle.

Some hotspot volcanism is likely the surface manifestation of hot upwelling mantle plumes that rise from the core–mantle boundary (CMB) or from compositional boundaries within the mantle. Plumes that rise from the CMB may generate magmas that carry compositional information about the diversity of materials present in the lowermost mantle. Some plume-derived materials have coupled enrichments in 186Os/188Os and 187Os/188Os relative to upper mantle materials. The coupled enrichments are consistent with Os isotopic compositions predicted for the liquid outer core that might result from elevated Pt/Os and Re/Os generated via progressive crystallization of a solid inner core over Earth history. If these enrichments are a reflection of core–mantle interaction, then the mechanisms of material transport between the core and the mantle, rates of whole mantle convection at present and over time, and cooling histories for the core and the mantle can potentially be constrained. However, fractionation may also occur between Pt/Re/Os via mantle and crustal processes and in particular, Pt and Pt/Re may be elevated in some portions of ancient recycled slabs thought to be present in certain plume sources. This possibility brings into question whether the coupled Os isotope enrichments are a product of core–mantle exchange. Hence, a lively debate over the causes of Os isotopic heterogeneities in plume-derived materials has ensued. Resolution of this debate has been hampered by limited constraints on the behavior of these elements in the Earth's core, mantle and crust. A variety of analytical and experimental tasks will have to be pursued to test different aspects of both the core–mantle interaction and crustal recycling models, and to further constrain the behaviors of these elements. These future endeavors may help to unravel the compositional complexities of plume-derived materials and their mantle sources, and ultimately provide important insights to processes operating at the CMB.

The Tagish Lake meteorite is a primitive C2 chondrite that has undergone aqueous alteration shortly after formation of its parent body. Previous work indicates that if this type of material was part of a late veneer during terrestrial planetary accretion, it could provide a link between atmophile elements such as H, C, N and noble gases, and highly siderophile element replenishment in the bulk silicate portions of terrestrial planets following core formation. The systematic Re-Os isotope and highly siderophile element measurements performed here on five separate fractions indicate that while Tagish Lake has amongst the highest Ru/Ir (1.63 0.08), Pd/Ir (1.19 0.06) and 187 Os/ 188 Os (0.12564 - 0.12802) of all carbonaceous chondrites, these characteristics still fall short of those necessary to explain the observed siderophile element systematics of the primitive upper mantles of Earth and Mars. Hence, a direct link between atmophile and highly siderophile elements remains elusive, and other sources for replenishment are required, unless an as yet poorly constrained process fractionated Re/Os, Ru/Ir, and Pd/Ir following late accretion on both the Earth and Mars mantles. The unique elevated Ru/Ir combined with elevated 187 Os/ 188 Os of Tagish Lake may be attributed to Ru and Re mobility during aqueous alteration very early in its parent body history. The Os, Ir, Pt, and Pd abundances of Tagish Lake are similar to CI chondrites. The elevated Ru/Ir and the higher Re/Os and consequent 187 Os/ 188 Os in Tagish Lake, are balanced by a lower Ru/Ir and lower Re/Os and 187 Os/ 188 Os in CM- chondrites, relative to CI chondrites. A model that links Tagish Lake with CI and CM chondrites in the same parent body may explain the observed systematics. In this scenario, CM chondrite material comprises the exterior, grading downward to Tagish Lake material, which grades to CI material in the interior of the parent body. Aqueous alteration intensifies towards the interior with increasing temperature. Ruthenium and Re are mobilized from the CM layer into the Tagish Lake layer. This model may thus provide a potential direct parent body relationship between three separate groups of carbonaceous chondrites. Copyright © 2005 Elsevier Ltd

More than 100 Os–Ir–Ru alloy grains from southwestern Oregon, presumably originating in the Mesozoic Josephine ophiolite, were examined for major and minor element compositions and 187Os/188Os isotopic compositions. Sixteen grains spanning the range of 187Os/188Os ratios present in the larger suite were analyzed for high-precision 186Os/188Os ratios. The ranges of major and minor element abundances of individual grains were, in general, similar to compositions previously reported for such grains worldwide. Within-suite compositional variations were quite large. Most grains were likely disaggregated from larger intergrown clusters, and were subdivided based on texture into matrix and lamellae. Composition variations within individual matrix grains were limited, whereas variations within individual lamellae grains were considerably larger. The 187Os/188Os ratios of individual grains were isotopically homogeneous at the ±0.1% level of resolution. The 187Os/188Os ratios of the entire suite of grains ranged from 0.1173 to 0.1468. The average ratio for all grains combined was 0.1241, similar to the composition of three chromitites sampled from the Josephine Creek, and consistent with formation in the Mesozoic upper mantle. The average 186Os/188Os ratio of the subset of 16 grains was 0.119838. All grains but one had isotopic ratios within ±20 ppm of that ratio. Results indicate that 187Os/188Os variations on a scale of mm3 may be quite large within the upper mantle, mimicking heterogeneities observed in both hand-and outcrop-scale samples of upper mantle materials. Highly depleted compositions relative to ambient upper mantle with chondritic 187Os/188Os require that some of the heterogeneities must be >1 Ga. The homogeneity of the 186Os/188Os ratios lend no support to the contention that isotopic heterogeneities within the upper mantle may explain coupled 186Os–187Os enrichments that have been observed in putative plume derived lavas.

Precise Pt–Re–Os isotopic and highly siderophile element (HSE) data are reported for 10 drill core samples collected across a 2.7 m thick, differentiated komatiite lava flow at Pyke Hill in Ontario, Canada. The Pt–Re–Os isotopic data for five cumulate samples yield Re–Os and Pt–Os isochrons with ages of 2725F33 and 2956F760 Ma and initial 187 Os/ 188 Os=0.10902F16 and 186 Os/ 188 Os=0.1198318F18, respectively. These ages are consistent with the time of lava emplacement determined by other geochronometers. The initial 187 Os/ 188 Os isotopic composition of the Pyke Hill source is similar to the 187 Os/ 188 Os isotopic compositions of enstatite and ordinary chondrites and to that of PUM at 2725 Ma. Using the Pt–Os isotopic data for the Pyke Hill source, the present-day 186 Os/ 188 Os isotopic composition of PUM was calculated to be 0.1198387F18. The regression of global 187 Os/ 188 Os isotopic data for terrestrial materials shown to represent Os isotopic composition of the contemporary mantle indicates that the LILE-depleted mantle evolved from the solar system starting composition and, over Earth’s history, was on average f8% depleted in Re vs. Os relative to PUM. From the HSE composition of the emplaced Pyke Hill komatiite lava, the mantle source was inferred to contain Re (0.30 ppb), Os (3.9 ppb), Ir (3.6 ppb), Ru (5.4 ppb), Pt (6.4 ppb), and Pd (6.3 ppb) in relative proportions similar to those in average enstatite chondrites, except for Pd, which was enriched over Pt by f30% in the Pyke Hill source compared to enstatite chondrites. From these data, the 190 Pt/ 188 Os of PUM was calculated to be 0.00157. If the HSE abundances in the terrestrial mantle were inherited from chondritic material of a late veneer, the latter should have had the HSE composition of ordinary or enstatite chondrites. Alternatively, if the reenrichment of the mantle with HSE was the result of an open-system transport of material across the core–mantle boundary, it was likely a global event that should have occurred shortly after core formation. D 2004 Elsevier B.V. All rights reserved.