Werdingite from the Urungwe District, Zimbabwe

Electron and ion microprobe data on two samples of welshite from the type locality of Langban, Sweden, gave analytical totals of 99.38-99.57 wt.% and BeO contents of 4.82-5.11 wt.%, corresponding to 1.692-1.773 Be/20 O. Mossbauer and optical spectra of o

Exploring the Moon's surface for remnants of the lunar mantle 1. Dunite xenoliths in mare basalts. A crustal or mantle origin?

Remotely sensed observations from recent missions (e.g., GRAIL, Kaguya, Chandrayaan-1) have been interpreted as indicating that the deep crust and upper mantle are close to or at the lunar surface in many large impact basins (e.g., Crisium, Apollo, Moscoviense). If this is correct, the capability of either impact or volcanic processes to transport mantle lithologies to the lunar surface should be enhanced in these regions. Somewhat problematic to these observations and interpretations is that examples of mantle lithologies in the lunar sample collection (Apollo Program, Luna Program, lunar meteorites) are at best ambiguous. Dunite xenoliths in high-Ti mare basalt 74275 are one of these ambiguous examples. In this high-Ti mare basalt, olivine occurs in three generations: olivine associated with dunite xenoliths, olivine megacrysts, and olivine microphenocrysts. The dunite xenoliths are anhedral in shape and are generally greater than 800 μm in diameter. The interior of the xenoliths are fairly homogeneous with regard to many divalent cations. For example, the Mg# (Mg/Mg + Fe × 100) ranges from 82 to 83 in their interiors and decreases from 82 to 68 over the 10–30 μm wide outer rim. Titanium and phosphorus X-ray maps of the xenolith illustrate that these slow diffusing elements preserve primary cumulate zoning textures. These textures indicate that the xenoliths consist of many individual olivine grains approximately 150–200 μm in diameter with low Ti, Al, and P cores. These highly incompatible elements are enriched in the outer Fe-rich rims of the xenoliths and slightly enriched in the rims of the individual olivine grains. Highly compatible elements in olivine such as Ni exhibit a decrease in the rim surrounding the xenolith, an increase in the incompatible element depleted cores of the individual olivine grains, and a slight decrease in the “interior rims” of the individual olivine grains. Inferred melt composition, liquid lines of descent, and zoning profiles enable the reconstruction of the petrogenesis of the dunite xenoliths. Preservation of primary magmatic zoning (Ti, P, Al) and lack of textures similar to high-pressure mineral assemblages exhibited by the Mg-suite (Shearer et al. 2015) indicate that these xenoliths do not represent deep crustal or shallow mantle lithologies. Further, they are chemically and mineralogically distinct from Mg-suite dunites identified from the Apollo 17 site. More likely, they represent olivine cumulates that crystallized from a low-Ti mare basalt at intermediate to shallow crustal levels. The parent basalt to the dunite xenolith lithology was more primitive than low-Ti basalts thus far returned from the Moon. Furthermore, this parental magma and its more evolved daughter magmas are not represented in the basalt sample suite returned from the Taurus-Littrow Valley by the Apollo 17 mission. The dunite xenolith records several episodes of crystallization and re-equilibration. During the last episode of re-equilibration, the dunite cumulate was sampled by the 74275 high-Ti basalt and transported over a period of 30–70 days to the lunar surface

The Cr Redox Record of fO2 Variation in Angrites. Evidence for Redox Conditions of Angrite Petrogenesis and Parent Body

Angrites represent some of the earliest stages of planetesimal differentiation. Not surprisingly, there is no simple petrogenetic model for their origin. Petrogenesis has been linked to both magmatic and impact processes. Studies demonstrated that melting of chondritic material (e.g. CM, CV) at redox conditions where pure iron metal is unstable (e.g., IW+1 to IW+2) produced angrite-like melts. Alternatively, angrites were produced at more reducing conditions (<IW) with their exotic melt compositions resulting from carbonates in the source or from nebular condensation. Clearly, understanding what role fO2 plays in producing angrite magmas is critical for deciphering their petrogenesis and extending our understanding of primordial melting of asteroids. Calculations for the fO2 conditions of angrite crystallization are limited, and only preliminary attempts been made to understand the changes in fO2 that occurred during petrogenesis. Many of the angrites have phase assemblages which provide conflicting signals about redox conditions during crystallization (e.g., Fe metal and a Fe-Ti oxide with potential Fe3+. There have been several estimates of fO2 for angrites. Most notably, experiments examined the variation of DEu/DGd with fO2, between plagioclase and fassaitic pyroxene in equilibrium with an angrite melt composition. They used their observations to estimate the fO2 of crystallization to be approximately IW+0.6 for angrite LEW 86010. This estimate is only a "snapshot" of fO2 conditions during co-crystallization of plagioclase and pyroxene. Preliminary XANES analyses of V redox state in pyroxenes from D'Orbigny reported changes in fO2 from IW-0.7 during early pyroxene crystallization to IW+0.5 during latter episodes of pyroxene crystallization [15]. As this was a preliminary report, it presented limited information concerning the effects of pyroxene orientation and composition on the V valence measurements, and the effect of melt composition on valence and partitioning behavior of V. A closer examination of fO2 as recorded by Cr valence state in olivine will allow us to test models for primordial melting of chondritic material to produce the angrite parent melts. Here, we report the our initial stages of examining the origin and conditions of primordial melting on the angrite parent body and test some of the above models by integrating an experimental study of Cr and V valence partitioning between olivine [OL] and an angrite melt, with micro-scale determinations of Cr and V oxidation state in OL in selected "volcanic" angrites

The Mineralogical Record of Oxygen Fugacity Variation and Alteration in Northwest Africa 8159: Evidence for Interaction Between a Mantle Derived Martian Basalt and a Crustal Component(s)

A prominent geochemical feature of basaltic magmatism on Mars is the large range in initial Sr isotopic ratios (approx. 0.702 - 0.724) and initial epsilon-Nd values (approx. -10 to greater than +50). Within this range, the shergottites fall into three discreet subgroups. These subgroups have distinct bulk rock REE patterns, mineral chemistries (i.e. phosphate REE patterns, Ni, Co, V in olivine), oxygen fugacity of crystallization, and stable isotopes, such as O. In contrast, nakhlites and chassignites have depleted epsilon-Nd values (greater than or equal to +15), have REE patterns that are light REE enriched, and appear to have crystallized near the FMQ buffer. The characteristics of these various martian basalts have been linked to different reservoirs in the martian crust and mantle, and their interactions during the petrogenesis of these magmas. These observations pose interesting interpretive challenges to our understanding of the conditions of the martian mantle (e.g. oxygen fugacity) and the interaction of mantle derived magmas with the martian crust and surface. Martian meteorite NWA 8159 is a unique fine-grained augite basalt derived from a highly depleted mantle source as reflected in its initial epsilon-Nd value, contains a pronounced light REE depleted pattern, and crystallized presumably under very oxidizing conditions. Although considerably older than both shergottites and nahklites, it has been petrogenetically linked to both styles of martian magmatism. These unique characteristics of NWA 8159 may provide an additional perspective for deciphering the petrogenesis of martian basalts and the nature of the crust of Mars

Evidence for a Heterogeneous Distribution of Water in the Martian Interior

The abundance and distribution of H2O within the terrestrial planets, as well as its timing of delivery, is a topic of vital importance for understanding the chemical and physical evolution of planets and their potential for hosting habitable environments. Analysis of planetary materials from Mars, the Moon, and the eucrite parent body (i.e., asteroid 4Vesta) have confirmed the presence of H2O within their interiors. Moreover, H and N isotopic data from these planetary materials suggests H2O was delivered to the inner solar system very early from a common source, similar in composition to the carbonaceous chondrites. Despite the ubiquity of H2O in the inner Solar System, the only destination with any prospects for past or present habitable environments at this time, outside of the Earth, is Mars. Although the presence of H2O within the martian interior has been confirmed, very little is known regarding its abundance and distribution within the martian interior and how the martian water inventory has changed over time. By combining new analyses of martian apatites within a large number of martian meteorite types with previously published volatile data and recently determined mineral-melt partition coefficients for apatite, we report new insights into the abundance and distribution of volatiles in the martian crust and mantle. Using the subset of samples that did not exhibit crustal contamination, we determined that the enriched shergottite mantle source has 36-73 ppm H2O and the depleted shergottite mantle source has 14-23 ppm H2O. This result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the martian mantle. We also estimated the H2O content of the martian crust using the revised mantle H2O abundances and known crust-mantle distributions of incompatible lithophile elements. We determined that the bulk martian crust has approximately 1400 ppm H2O, which is likely distributed toward the martian surface. This crustal water abundance would equate to a global equivalent layer (GEL) of water at a depth of-229 m, which can account for at least some of the surface features on Mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on Mars' surface

Phosphate minerals in LL chondrites: A record of the action of fluids during metamorphism on ordinary chondrite parent bodies

Ordinary chondrites contain two phosphate minerals, merrillite and chlorapatite, both of which are secondary minerals that developed in response to metamorphism on the chondrite parent bodies. We have studied the phosphate mineralogy of four LL chondrites, of petrologic types 3.9–6, in order to determine the petrogenesis of the two minerals and interpret the conditions under which they formed. Characterization of merrillite and apatite includes textural observations, mineral compositions determined by electron probe microanalysis, and ion microprobe analyses of trace element and volatile anion elemental abundances. Initial formation of phosphate minerals during mild metamorphism, to petrologic type 4 conditions, resulted in oxidation of P that was originally incorporated in metal, and growth of merrillite as inclusions within metal grains. Subsequent development of both phosphate minerals occurred in response to diffusional equilibration, possible precipitation from fluids as well as replacement reactions resulting from interactions with fluids. Porosity and vein-filling textures in both merrillite and chlorapatite, as well as textures indicating replacement of merrillite by chlorapatite, support a model in which fluid played a significant role and suggest an interface-coupled dissolution–reprecipitation mechanism during metasomatism. Some associations of phosphate minerals with chromite-plagioclase assemblages suggest that phosphate minerals could also be related to impact processes, either as precipitation from an impact melt or as a result of interactions with a fluid or vapor derived from an impact melt. Fluid compositions may have been water-bearing initially, at low temperatures of metamorphism, but later evolved to become halogen-rich and very dry. Late-stage halogen-rich fluids that dominated during cooling of LL chondrite material may have been derived from vaporization of partial melts in the interior of the parent body. Overall, the LL chondrite parent body underwent a complex chemical evolution, in which metasomatism played a significant role

Magmatic volatiles (H, C, N, F, S, Cl) in the lunar mantle, crust, and regolith: abundances, distributions, processes, and reservoirs

There have been many studies on magmatic volatiles (H, C, N, F, S, Cl) in and on the Moon within the last several years that have cast into question the post-Apollo view of lunar formation, the distribution and sources of volatiles in the Earth-Moon system, and the thermal and magmatic evolution of the Moon. However, these recent observations are not the first data on lunar volatiles. When Apollo samples were first returned, substantial efforts were made to undersand volatile elements and a wealth of data regarding volatile elements exists in this older literature. In this review paper we approach volatiles in and on the Moon using new and old data derived from lunar samples and remote sensing. From combining these data sets, we identified many points of convergence, although numerous questions remain unanswered

Using a pragmatically adapted, low-cost contingency management intervention to promote heroin abstinence in individuals undergoing treatment for heroin use disorder in UK drug services (PRAISE): a cluster randomised trial

Introduction: Most individuals treated for heroin use disorder receive opioid agonist treatment (OAT)(methadone or buprenorphine). However, OAT is associated with high attrition and persistent, occasional heroin use. There is some evidence for the effectiveness of contingency management (CM), a behavioural intervention involving modest financial incentives, in encouraging drug abstinence when applied adjunctively with OAT. UK drug services have a minimal track record of applying CM and limited resources to implement it. We assessed a CM intervention pragmatically adapted for ease of implementation in UK drug services to promote heroin abstinence among individuals receiving OAT. Design: Cluster randomised controlled trial. Setting and participants: 552 adults with heroin use disorder (target 660) enrolled from 34 clusters (drug treatment clinics) in England between November 2012 and October 2015. Interventions: Clusters were randomly allocated 1:1:1 to OAT plus 12× weekly appointments with: (1) CM targeted at opiate abstinence at appointments (CM Abstinence); (2) CM targeted at on-time attendance at appointments (CM Attendance); or (3) no CM (treatment as usual; TAU). Modifications included monitoring behaviour weekly and fixed incentives schedule. Measurements: Primary outcome: heroin abstinence measured by heroin-free urines (weeks 9–12). Secondary outcomes: heroin abstinence 12 weeks after discontinuation of CM (weeks 21–24); attendance; self-reported drug use, physical and mental health. Results: CM Attendance was superior to TAU in encouraging heroin abstinence. Odds of a heroin-negative urine in weeks 9–12 was statistically significantly greater in CM Attendance compared with TAU (OR=2.1; 95% CI 1.1 to 3.9; p=0.030). CM Abstinence was not superior to TAU (OR=1.6; 95% CI 0.9 to 3.0; p=0.146) or CM Attendance (OR=1.3; 95% CI 0.7 to 2.4; p=0.438) (not statistically significant differences). Reductions in heroin use were not sustained at 21–24 weeks. No differences between groups in self-reported heroin use. Conclusions: A pragmatically adapted CM intervention for routine use in UK drug services was moderately effective in encouraging heroin abstinence compared with no CM only when targeted at attendance. CM targeted at abstinence was not effective. Trial registration number: ISRCTN 01591254

Advancing Science of the Moon: Progress Toward Achieving the Goals of the Scientific Context for Exploration of the Moon Report

No abstract availabl

Using a pragmatically adapted, low-cost contingency management intervention to promote heroin abstinence in individuals undergoing treatment for heroin use disorder in UK drug services (PRAISE): a cluster randomised trial

Introduction: Most individuals treated for heroin use disorder receive opioid agonist treatment (OAT)(methadone or buprenorphine). However, OAT is associated with high attrition and persistent, occasional heroin use. There is some evidence for the effectiveness of contingency management (CM), a behavioural intervention involving modest financial incentives, in encouraging drug abstinence when applied adjunctively with OAT. UK drug services have a minimal track record of applying CM and limited resources to implement it. We assessed a CM intervention pragmatically adapted for ease of implementation in UK drug services to promote heroin abstinence among individuals receiving OAT. Design: Cluster randomised controlled trial. Setting and participants: 552 adults with heroin use disorder (target 660) enrolled from 34 clusters (drug treatment clinics) in England between November 2012 and October 2015. Interventions: Clusters were randomly allocated 1:1:1 to OAT plus 12× weekly appointments with: (1) CM targeted at opiate abstinence at appointments (CM Abstinence); (2) CM targeted at on-time attendance at appointments (CM Attendance); or (3) no CM (treatment as usual; TAU). Modifications included monitoring behaviour weekly and fixed incentives schedule. Measurements: Primary outcome: heroin abstinence measured by heroin-free urines (weeks 9–12). Secondary outcomes: heroin abstinence 12 weeks after discontinuation of CM (weeks 21–24); attendance; self-reported drug use, physical and mental health. Results: CM Attendance was superior to TAU in encouraging heroin abstinence. Odds of a heroin-negative urine in weeks 9–12 was statistically significantly greater in CM Attendance compared with TAU (OR=2.1; 95% CI 1.1 to 3.9; p=0.030). CM Abstinence was not superior to TAU (OR=1.6; 95% CI 0.9 to 3.0; p=0.146) or CM Attendance (OR=1.3; 95% CI 0.7 to 2.4; p=0.438) (not statistically significant differences). Reductions in heroin use were not sustained at 21–24 weeks. No differences between groups in self-reported heroin use. Conclusions: A pragmatically adapted CM intervention for routine use in UK drug services was moderately effective in encouraging heroin abstinence compared with no CM only when targeted at attendance. CM targeted at abstinence was not effective. Trial registration number: ISRCTN 01591254