Evidence for high‐temperature fractionation of lithium isotopes during differentiation of the Moon          下载免费PDF全文

James M. D. Day  Lin Qiu  Richard D. Ash  William F. McDonough  Fang‐Zhen Teng  Roberta L. Rudnick  Lawrence A. Taylor 《Meteoritics & planetary science》2016,51(6):1046-1062

Lithium isotope and abundance data are reported for Apollo 15 and 17 mare basalts and the LaPaz low‐Ti mare basalt meteorites, along with lithium isotope data for carbonaceous, ordinary, and enstatite chondrites, and chondrules from the Allende CV3 meteorite. Apollo 15 low‐Ti mare basalts have lower Li contents and lower δ⁷Li (3.8 ± 1.2‰; all uncertainties are 2 standard deviations) than Apollo 17 high‐Ti mare basalts (δ⁷Li = 5.2 ± 1.2‰), with evolved LaPaz mare basalts having high Li contents, but similar low δ⁷Li (3.7 ± 0.5‰) to Apollo 15 mare basalts. In low‐Ti mare basalt 15555, the highest concentrations of Li occur in late‐stage tridymite (>20 ppm) and plagioclase (11 ± 3 ppm), with olivine (6.1 ± 3.8 ppm), pyroxene (4.2 ± 1.6 ppm), and ilmenite (0.8 ± 0.7 ppm) having lower Li concentrations. Values of δ⁷Li in low‐ and high‐Ti mare basalt sources broadly correlate negatively with ¹⁸O/¹⁶O and positively with ⁵⁶Fe/⁵⁴Fe (low‐Ti: δ⁷Li ≤4‰; δ⁵⁶Fe ≤0.04‰; δ¹⁸O ≥5.7‰; high‐Ti: δ⁷Li >6‰; δ⁵⁶Fe >0.18‰; δ¹⁸O <5.4‰). Lithium does not appear to have acted as a volatile element during planetary formation, with subequal Li contents in mare basalts compared with terrestrial, martian, or vestan basaltic rocks. Observed Li isotopic fractionations in mare basalts can potentially be explained through large‐degree, high‐temperature igneous differentiation of their source regions. Progressive magma ocean crystallization led to enrichment in Li and δ⁷Li in late‐stage liquids, probably as a consequence of preferential retention of ⁷Li and Li in the melt relative to crystallizing solids. Lithium isotopic fractionation has not been observed during extensive differentiation in terrestrial magmatic systems and may only be recognizable during extensive planetary magmatic differentiation under volatile‐poor conditions, as expected for the lunar magma ocean. Our new analyses of chondrites show that they have δ⁷Li ranging between ?2.5‰ and 4‰. The higher δ⁷Li in planetary basalts than in the compilation of chondrites (2.1 ± 1.3‰) demonstrates that differentiated planetary basalts are, on average, isotopically heavier than most chondrites.  相似文献   

Comparison of spectral characteristics of precipitation from radar estimates and COSMO-model predicted fields     

Matteo Willeit  Roberta Amorati  Andrea Montani  Valentina Pavan  Maria Stefania Tesini 《Meteorology and Atmospheric Physics》2015,127(2):191-203

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Determination of Ga,Ge, Mo,Ag, Cd,In, Sn,Sb, W,Tl and Bi in USGS Whole‐Rock Reference Materials by Standard Addition ICP‐MS          下载免费PDF全文

Richard M. Gaschnig  Roberta L. Rudnick  William F. McDonough 《Geostandards and Geoanalytical Research》2015,39(3):371-379

A procedure for determining a wide range of chalcophile and siderophile elements in typical crustal rocks using standard addition and ICP‐SFMS (inductively coupled plasma sector field mass spectrometry) is presented. New results for Ga, Ge, Mo, Ag, Cd, In, Sn, Sb, W, Tl and Bi abundances in USGS whole‐rock reference materials AGV‐2, BHVO‐1, BIR‐1, G‐2, GSP‐1 and W‐2 are reported using this analytical procedure. Intermediate precision of means based on multiple dissolved aliquots of each USGS reference material was 10% RSD or better for Ga, Ge, In and Sn in all, and similarly good for Ag, Cd, Sb, Tl and Bi in most reference materials. Poorer intermediate precision of Mo and W measurements in several reference materials is probably due to higher analytical blanks on these elements and powder heterogeneity due to a sulfide‐related nugget effect in the specific case of Mo in GSP‐1. Results for all elements fell within the range of available published data with the exception of Ag, which yielded systematically higher concentrations than found in the literature for five of the six reference materials, likely reflecting interference from unresolved polyatomic species.  相似文献   

Shock effects in plagioclase feldspar from the Mistastin Lake impact structure,Canada          下载免费PDF全文

Annemarie E. Pickersgill  Gordon R. Osinski  Roberta L. Flemming 《Meteoritics & planetary science》2015,50(9):1546-1561

Shock metamorphism, caused by hypervelocity impact, is a poorly understood process in feldspar due to the complexity of the crystal structure, the relative ease of weathering, and chemical variations, making optical studies of shocked feldspars challenging. Understanding shock metamorphism in feldspars, and plagioclase in particular, is vital for understanding the history of Earth's moon, Mars, and many other planetary bodies. We present here a comprehensive study of shock effects in andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada. Samples from a range of different settings were studied, from in situ central uplift materials to clasts from various breccias and impact melt rocks. Evidence of shock metamorphism includes undulose extinction, offset twins, kinked twins, alternate twin deformation, and partial to complete transformation to diaplectic plagioclase glass. In some cases, isotropization of alternating twin lamellae was observed. Planar deformation features (PDFs) are notably absent in the plagioclase, even when present in neighboring quartz grains. It is notable that various microlites, twin planes, and compositionally different lamellae could easily be mistaken for PDFs and so care must be taken. A pseudomorphous zeolite phase (levyne‐Ca) was identified as a replacement mineral of diaplectic feldspar glass in some samples, which could, in some instances, also be potentially mistaken for PDFs. We suggest that the lack of PDFs in plagioclase could be due to a combination of structural controls relating to the crystal structure of different feldspars and/or the presence of existing planes of weakness in the form of twin and cleavage planes.  相似文献   

The thin layer of Warm Ionized Gas: towards a 3-D reconstruction of the spatial distribution of HII regions     

Roberta Paladini  Rod Davies  Gianfranco DeZotti 《Astrophysics and Space Science》2004,289(3-4):363-366

HII regions are known to contribute to the so-called thin layer of the diffuse Warm Ionized Gas. In order to constrain thiscontribution, we reconstruct the 3-D distribution of the sources.A detailed spatial analysis of the largest up-to-date sample of HIIregions is presented.  相似文献   

The crystal chemistry of lithium and Fe3+ in synthetic orthopyroxene     

Fernando Cámara  Gianluca Iezzi  Massimo Tiepolo  Roberta Oberti 《Physics and Chemistry of Minerals》2006,33(7):475-483

Lithian ferrian enstatite with Li₂O = 1.39 wt% and Fe₂O₃ 7.54 wt% was synthesised in the (MgO–Li₂O–FeO–SiO₂–H₂O) system at P = 0.3 GPa, T = 1,000°C, fO₂ = +2 Pbca, and a = 18.2113(7), b = 8.8172(3), c = 5.2050(2) Å, V = 835.79(9) Å³. The composition of the orthopyroxene was determined combining EMP, LA-ICP-MS and single-crystal XRD analysis, yielding the unit formula ^M2(Mg_0.59Fe _0.21 ²⁺ Li_0.20) ^M1(Mg_0.74Fe _0.20 ³⁺ Fe _0.06 ²⁺ ) Si₂O₆. Structure refinements done on crystals obtained from synthesis runs with variable Mg-content show that the orthopyroxene is virtually constant in composition and hence in structure, whereas coexisting clinopyroxenes occurring both as individual grains or thin rims around the orthopyroxene crystals have variable amounts of Li, Fe³⁺ and Mg contents. Structure refinement shows that Li is ordered at the M2 site and Fe³⁺ is ordered at the M1 site of the orthopyroxene, whereas Mg (and Fe²⁺) distributes over both octahedral sites. The main geometrical variations observed for Li-rich samples are actually due to the presence of Fe³⁺, which affects significantly the geometry of the M1 site; changes in the geometry of the M2 site due to the lower coordination of Li are likely to affect both the degree and the kinetics of the non-convergent Fe²⁺-Mg ordering process in octahedral sites.  相似文献   

An ensemble approach for the analysis of extreme rainfall under climate change in Naples (Italy)     

Roberta Padulano  Alfredo Reder  Guido Rianna 《水文研究》2019,33(14):2020-2036

In the present paper, an ensemble approach is proposed to estimate possible modifications caused by climate changes in the extreme precipitation regime, with the rain gauge Napoli Servizio Idrografico (Naples, Italy) chosen as test case. The proposed research, focused on the analysis of extremes on the basis of climate model simulations and rainfall observations, is structured in several consecutive steps. In the first step, all the dynamically downscaled EURO‐CORDEX simulations at about 12 km horizontal resolution are collected for the current period 1971–2000 and the future period 2071–2100, for the RCP4.5 and the RCP8.5 concentration scenarios. In the second step, the significance of climate change effects on extreme precipitation is statistically tested by comparing current and future simulated data and bias‐correction is performed by means of a novel approach based on a combination of simple delta change and quantile delta mapping, in compliance with the storm index method. In the third step, two different ensemble models are proposed, accounting for the variabilities given by the use of different climate models and for their hindcast performances. Finally, the ensemble models are used to build novel intensity–duration–frequency curves, and their effects on the early warning system thresholds for the area of interest are evaluated.  相似文献   

From ERS-1/2 to Sentinel-1: two decades of subsidence monitored through A-DInSAR techniques in the Ravenna area (Italy)     

Simone Fiaschi  Serena Tessitore  Roberta Bonì  Diego Di Martire  Vladimiro Achilli  Sven Borgstrom 《地理信息系统科学与遥感》2017,54(3):305-328

Land subsidence due to underground resources exploitation is a well-known problem that affects many cities in the world, especially the ones located along the coastal areas where the combined effect of subsidence and sea level rise increases the flooding risk. In this study, 25 years of land subsidence affecting the Municipality of Ravenna (Italy) are monitored using Advanced Differential Interferometric Synthetic Aperture Radar (A-DInSAR) techniques. In particular, the exploitation of the new Sentinel-1A SAR data allowed us to extend the monitoring period till 2016, giving a better understanding of the temporal evolution of the phenomenon in the area. Two statistical approaches are applied to fully exploit the informative potential of the A-DInSAR results in a fast and systematic way. Thanks to the applied analyses, we described the behavior of the subsidence during the monitored period along with the relationship between the occurrence of the displacement and its main driving factors.  相似文献   

Advances and Practices on the Research,Prevention and Control of Land Subsidence in Coastal Cities     

YAN Xuexin  YANG Tianliang  XU Yan  Luigi TOSI  Esther STOUTHAMER  Heri ANDREAS  Philip MINDERHOUD  Anirut LADAWADEE  Ramon HANSSEN  Gilles ERKENS  Pietro TEATINI  LIN Jinxin  Roberta BONì  Jarinya CHIMPALEE  HUANG Xinlei  Cristina Da LIO  Claudia MEISINA  Francesco ZUCCA 《《地质学报》英文版》2020,94(1):162-175

Land subsidence severely threatens most of the coastal plains around the world where high productive industrial and agricultural activities and urban centers are concentrated. Coastal subsidence damages infrastructures and exacerbates the effect of the sea-level rise at regional scale. Although it is a well-known process, there is still much more to be improved on the monitoring, mapping and modeling of ground movements, as well as the understanding of controlling mechanisms. The International Geoscience Programme recently approved an international project (IGCP 663) aiming to bring together worldwide researchers to share expertise on subsidence processes typically occurring in coastal areas and cities, including basic research, monitoring and observation, modelling and management. In this paper, we provide the research communities and potential stakeholders with the basic information to join the participating teams in developing this project. Specifically, major advances on coastal subsidence studies and information on well-known and new case studies of land subsidence in China, Italy, The Netherlands, Indonesia, Vietnam and Thailand are highlighted and summarized. Meanwhile, the networking, dissemination, annual meeting and field trip are briefly introduced.  相似文献   

Dynamics of continental collision: influence of the plate contact     

Roberta De Franco  Rob Govers  Rinus Wortel 《Geophysical Journal International》2008,174(3):1101-1120

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