We present the Strong Lensing Legacy Survey-ARCS (SARCS) sample compiled from the final T0006 data release of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) covering a total ...non-overlapping area of 159 deg super(2). We adopt a semi-automatic method to find gravitational arcs in the survey that makes use of an arc-finding algorithm. The candidate list is pruned by visual inspection and ranking to form the final SARCS sample. This list also includes some serendipitously discovered lens candidates which the automated algorithm did not detect. The SARCS sample consists of 127 lens candidates which span arc radii ~2"-18" within the unmasked area of ~150 deg super(2). Within the sample, 54 systems are promising lenses among which, we find 12 giant arcs (length-to-width ratio > or =, slanted8). We also find two radial arc candidates in SL2SJ141447+544704. From our sample, we detect a systematic alignment of the giant arcs with the major axis of the baryonic component of the putative lens in concordance with previous studies. This alignment is also observed for all arcs in the sample and does not vary significantly with increasing arc radius. The mean values of the photometric redshift distributions of lenses corresponding to the giant arcs and all arcs sample are at z ~ 0.6. Owing to the large area and depth of the CFHTLS, we find the largest sample of lenses probing mass scales that are intermediate to cluster and galaxy lenses for the first time. We compare the observed image separation distribution (ISD) of our arcs with theoretical models. A two-component density profile for the lenses which accounts for both the central galaxy and the dark matter component is required by the data to explain the observed ISD. Unfortunately, current levels of uncertainties and degeneracies accommodate models both with and without adiabatic contraction. We also show the effects of changing parameters of the model that predict the ISD and that a larger lens sample might constrain relations such as the concentration-mass relation, mass-luminosity relation, and the faint-end slope of the luminosity function.
Despite a relatively 'uniform' fertile composition (Al2O3 = 2·19-4·47 wt %; Fo% = 89·2 ± 0·3%; Cr#Spl = 8·9 ± 1·5%), the Montferrier peridotite xenoliths show a wide range of S contents (22-590 ppm). ...Most sulphides are interstitial and show peculiar pyrrhotite-pentlandite intergrowths and low abundances of Cu-rich phases. Sulphide-rich samples are characterized by strong enrichment in the light rare earth elements and large ion lithophile elements without concomitant enrichment of the high field strength elements. Such trace-element fractionation is commonly ascribed to metasomatism by volatile-rich melts and/or carbonatitic melts. S and Se (11-67 ppb), as well as S/Se (up to 12 000), are correlated with La/Sm. Cu, however, remains broadly constant (30 ± 5 ppm). These features strongly suggest that the percolation-reaction of such volatile-rich fluids has led to sulphide enrichment with an atypical signature marked by strong fractionation of the chalcophile elements (i.e. S vs Se and Cu). S-rich xenoliths are also characterized by high (Pd/Ir)N (1·2-1·9; where subscript N indicates normalized to chondrite), (Pd/Pt)N between 1·5 and 2·2, and (Os/Ir)N up to 1·85. Despite the relative uniform fertile composition of the xenoliths, Re/Os ranges between 0·02 and 0·18. 187Os/188Os is extremely variable even within a single sample and can be as high as 0·1756 for the most S-rich samples. Sulphides show highly fractionated and variable abundances of the highly siderophile elements (HSE) 0·03 (Pd/Ir)N < 1283 and Re-Os isotopic composition (0·115 < 187Os/188Os < 0·172). Such variation can be observed at the thin-section scale. Whole-rock and in situ sulphide data demonstrate that chalcophile and HSE systematics and the Os isotopic composition of the upper mantle could be significantly modified through metasomatism, even with volatile-rich fluids. These features highlight the complex behaviour of the HSE in fluid-rock percolation-reaction models and suggest a complex interplay between sulphide addition (crystallization or sulphidation) and partial equilibration of pre-existing sulphide. The specific fractionations observed in chemical proxies such as S and Se, Os and Ir, and Pd and Pt, as well as the low abundance of Cu-rich sulphides, suggest that sulphide addition may not have occurred via sulphide melts. Rather, we infer that S was present as a dissolved species in a (supercritical) oxidizing, volatile-rich fluid (C-O-H-S ± Cl) along with other chalcophile and siderophile elements such as Os, Pd, Re and Au. The highly radiogenic Os composition of this fluid ( 187Os/ 188Os > 0·17) would imply that such fluids are derived from an uncommon type of mantle source possibly related to carbonatite melts.
Aims. We present data from the CFHTLS Strong Lensing Legacy Survey (SL2S). Due to the unsurpassed combined depth, area and image quality of the Canada-France-Hawaii Legacy Survey it is becoming ...possible to uncover a large, statistically well-defined sample of strong gravitational lenses which spans the dark halo mass spectrum predicted by the concordance model from galaxy to cluster haloes. Methods. We describe the development of several automated procedures to find strong lenses of various mass regimes in CFHTLS images. Results. The preliminary sample of about 40 strong lensing candidates discovered in the CFHTLS T0002 release, covering an effective field of view of 28 deg super(2) is presented. These strong lensing systems were discovered using an automated search and consist mainly of gravitational arc systems with splitting angles between 2 and 15 arcsec. This sample shows for the first time that it is possible to uncover a large population of strong lenses from galaxy groups with typical halo masses of about 10 6h 6M_\odot. We discuss the future evolution of the SL2S project and its main scientific aims for the next 3 years, in particular our observational strategy to extract the hundreds of gravitational rings also present in these fields.
Platinum‐group element (PGE) abundances in mantle rocks are generally considered to result from a late meteorite addition to the early Earth, post‐dating the core separation event. As such, PGEs are ...key tracers for the Earth accretion history. For decades, the PGEs systematics of undepleted mantle peridotites has been used to constrain the composition of meteorite impactors involved in the late veneer material. Despite multiple evidence of considerable modifications by partial melting, harzburgites from the Sumail ophiolite (Oman) display a mean PGE composition very akin to recently refined estimates for the Primitive Upper Mantle (PUM) of the Earth. These rocks document a resetting of the PUM signature by percolating basaltic melts, which precipitated Pd‐enriched Cu–Ni sulphides within a strongly Pd‐depleted residual harzburgitic protolith. Such a resetting casts doubt on both the reliability of any PUM estimates and relevance of the PUM concept itself, at least for PGEs.
The abundances of highly siderophile (iron-loving) elements (HSEs) in the
Earth's mantle provide important constraints on models of the Earth's early
evolution. It has long been assumed that the ...relative abundances of HSEs should
reflect the composition of chondritic meteorites-which are thought to
represent the primordial material from which the Earth was formed. But the
non-chondritic abundance ratios recently found in several types of rock derived
from the Earth's mantle have been difficult to reconcile
with standard models of the Earth's accretion,
and have been interpreted as having arisen from the addition to the primitive
mantle of either non-chondritic extraterrestrial material or differentiated
material from the Earth's core. Here we report in situ laser-ablation
analyses of sulphides in mantle-derived rocks which show that these sulphides
do not have chondritic HSE patterns, but that different generations of sulphide
within single samples show extreme variability in the relative abundances
of HSEs. Sulphides enclosed in silicate phases have high osmium and iridium
abundances but low Pd/Ir ratios, whereas pentlandite-dominated interstitial
sulphides show low osmium and iridium abundances and high Pd/Ir ratios. We
interpret the silicate-enclosed sulphides as the residues of melting processes
and interstitial sulphides as the crystallization products of sulphide-bearing
(metasomatic) fluids. We suggest that non-chondritic HSE patterns directly
reflect processes occurring in the upper mantle-that is, melting and
sulphide addition via metasomatism-and are not evidence for the addition
of core material or of 'exotic' meteoritic components.
We present a complete systematics (excitation functions and system-size dependences) of global stopping and side flow for heavy ion reactions in the energy range between 0.09A and 1.93A GeV. For the ...heaviest system, Au+Au, we observe a plateau of maximal stopping extending from about 0.2A to 0.8A GeV with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of side flow.
The highly siderophile element (HSE) contents of base-metal sulphides have been determined by laser-ablation microprobe (LAM)-ICPMS in abyssal peridotites from the Mid-Atlantic and South West Indian ...ridges. (Pd/Ir)N (0.007–505, N: CI-chondrite-normalised), (Pt/Ir)N (0.001–0.77) and (Rh/Ir)N (0.159–273) vary significantly between both grains and samples, irrespective of indicators of melt removal, but in line with bulk-rock platinum-group element (PGE) ratios and sulphide modal abundances. Positive deviations of PGE abundance ratios in whole-rock analyses are due to late-precipitated Cu–Ni-rich magmatic sulphides from incompletely extracted partial melts. These results contradict explanations of the HSE systematics of the oceanic mantle as reflecting global scale processes such as core–mantle exchange.
The Os isotopic compositions of mantle rocks generally are considered to be established during melt-depletion events and to be robust to subsequent disturbances (e.g. metasomatism). Consequently, Os ...isotopes are used to date the main melting event that a mantle section has undergone, i.e. transformation of fertile asthenospheric material into a depleted, buoyant lithosphere. However, Os resides almost entirely in Fe–Ni–Cu sulphides, which can be very mobile under mantle conditions. In situ laser ablation multi-collector ICP-MS measurement of Re/Os isotopic ratios in sulphides from spinel peridotite xenoliths demonstrates that whole-rock Os-isotope signatures record the mixing of multiple sulphide populations. Sulphides residual after melting events have unradiogenic Os isotopic compositions reflecting ancient melt depletion; those introduced by later metasomatism events contain more radiogenic Os. Therefore, the whole-rock Os isotopic signature can be strongly altered by metasomatic processes, and studies of mantle-derived xenoliths show that such disturbance is quite common in the lithospheric mantle. Because melt-depletion ages estimated from individual sulphide inclusions are systematically older than those obtained from whole-rock analysis, caution is essential in the interpretation of the Os model ages derived from whole-rock analysis, and their use and abuse in geodynamic models. This work suggests that sulphide could become a key phase in unravelling the formation and evolution of the lithosphere.
Fe–Ni–Cu sulfide mineralogy has been investigated along with bulk-rock and in-situ PGE analyses by ICP MS and LA-ICP-MS in eight lherzolites from the Internal (IL) and External Liguride (EL) ...ophiolites (Italy). The two EL lherzolites are fertile (2–4% partial melting) and slightly serpentinized while the six IL cpx-poor lherzolites have experienced 5–10% of partial melting, impregnation by instantaneous melt fractions Geochim. Cosmochim. Acta 61 (1997) 4557 and have been highly serpentinized.
The EL lherzolites show broadly chondritic PGE relative abundances with a slight to pronounced enhancement of the light PGE (Ru, Rh and Pd) relative to the heavy PGE (Os, Ir and Pt) (Ru
N/Ir
N=1.13; Rh
N/Ir
N=1.08–1.10; Pd
N/Ir
N=1.24–1.62; N=CI-chondrite normalized). Their magmatic sulfide modal abundances and S contents, similar to the orogenic peridotites values, are consistent with their very low degree of partial melting. The occurrence of Cu–Rh–Pd-rich pentlandite, however, demonstrates that, even for low degree of partial melting, a Cu–Ni-rich sulfide liquid can segregate, leaving the residual monosulfide solid solution (Mss) (now transformed into Cu-poor pentlandite) depleted in Rh and Pd (Rh
N/Ir
N and Pd
N/Ir
N<1).
The IL cpx-poor lherzolites display a broadly flat PGE patterns from Os to Pt with a slight enhancement of Ru and Rh (Ru
N/Ir
N=1.05–1.38; Rh
N/Ir
N=1.01–1.31). Pd
N/Ir
N ratios range from chondritic to superchondritic (1.02–2.99) and cannot be interpreted in terms of partial melting models. Rh–Pd–Cu–Ni-rich pentlandite grains are associated with large corroded cpx crystals ascribed to exotic melt percolation by Rampone et al. Geochim. Cosmochim. Acta 61 (1997) 4557. It is concluded that precipitation of Cu–Ni–Rh–Pd-rich sulfides has significantly enhanced the Pd concentrations as well as the magmatic sulfide modal abundances. Such processes, previously documented in abyssal peridotites from slow-spreading mid-oceanic ridges, characterize residues from low to moderate melting degrees (5–10%) of the oceanic mantle as a whole, either from mature ocean or from short-lived oceanic basins.
Selenium has been analyzed in addition to S in 58 spinel peridotite xenoliths collected in Cenozoic alkali basalts from the Massif Central (France). The S concentration range now available for this ...suite, calculated from 123 samples, is the largest ever reported for alkali basalt-hosted xenoliths (<3–592 ppm). Likewise, the Se concentrations range between 0.2 and 67 ppb. No partial melting signature can be identified from the S and Se systematic. Half of the analyzed xenoliths have lost S during supergene weathering. By contrast, neither surficial alteration, nor loss of chalcophile elements during eruption can explain the regional-scale variations of S and Se concentrations. A first group of lherzolite xenoliths sampled in Southern Massif Central, from volcanic centers older and spatially unrelated to the Massif Central plume that triggered the Cenozoic volcanism, contains between 20 and 250 ppm S (with occasional S concentrations up to 592 ppm) and 12–67 ppb Se. It is clear that the highest S values, originally interpreted as representing S abundances in the primitive mantle, were in fact enriched by metasomatism. Highly variable S and Se contents (<5–360 ppm; 9–52 ppb) have also been observed in peridotite xenoliths collected in the Northern Massif Central, from volcanic centers mostly older than the plume. Like Group I xenoliths, these Group II xenoliths were strongly metasomatized by volatile-rich carbonated/silicated melts which precipitated Cu-rich sulfides. A third group of xenoliths from Plio-Quaternary basalts spatially related to the Massif Central Plume are uniformly poor in S (10–60 ppm) and Se (9–29 ppb). In this Group III, poikiloblastic textured xenoliths have lost most of their S and Se budget by peridotite-melt interactions at high melt/rock ratios. Taken as a whole, the Massif Central xenolith suite provides further evidence for strong heterogeneities in the S and Se budget of the sub-continental lithospheric mantle. However, the few LREE-depleted fertile lherzolites that escaped strong metasomatic alterations suggest a S- and Se-depleted primitive mantle reservoir compared to currently accepted primitive mantle estimates.
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