Chemical Procedures for Rhenium Extraction from Geological Samples: Optimising the Anion Resin Bead Clean‐up Step     

Gang Yang  Aaron Zimmerman  Nicole C. Hurtig  Svetoslav V. Georgiev  Vineet Goswami  Judith L. Hannah  Holly J. Stein 《Geostandards and Geoanalytical Research》2020,44(2):231-242

Rhenium–osmium geochronometry for samples with low Re and complex matrices requires improved Re extraction methods. Here, we investigate plausible controls on efficiency and efficacy of Re extraction during our anion resin bead purification. Four different protocols are compared, each isolating a single variable to test. Rhenium concentrations for solutions at each step of each protocol document differences in chemical recovery/yield. The negative‐thermal ionisation mass spectrometry (N‐TIMS) signal intensity serves as a proxy for Re yield and purity. These data document correlations between the N‐TIMS signal intensity and (a) the duration of anion resin bead conditioning prior to loading with Re‐bearing solution, and (b) both duration and strength of nitric acid used during rinsing of the Re‐loaded anion resin bead. The optimal protocol improved Re signal intensity around fourteen times compared with our current Re extraction protocol, an aggregate of 2.4 times improvement in chemical recovery (yield) and 5.8 times improvement in emission efficiency (purity). Repeated N‐TIMS isotopic measurements on our in‐house Re standard solution (1407) verify that our optimal protocol‐3 does not fractionate Re isotopes. The improved anion resin bead method considerably lowers the Re detection limit and allows Re‐Os isotopic analysis of picogram‐level Re hosted in geological samples with complex matrices.  相似文献   

Crustal Structure of Israel: Constraints From Teleseismic and Gravity Data   总被引：1，自引：0，他引：1  

Abraham Hofstetter  Lea Feldman  Yair Rotstein 《Geophysical Journal International》1991,104(2):371-379

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Ti-in-zircon thermometry: applications and limitations   总被引：16，自引：5，他引：11  

Bin Fu  F. Zeb Page  Aaron J. Cavosie  John Fournelle  Noriko T. Kita  Jade Star Lackey  Simon A. Wilde  John W. Valley 《Contributions to Mineralogy and Petrology》2008,156(2):197-215

The titanium concentrations of 484 zircons with U-Pb ages of ∼1 Ma to 4.4 Ga were measured by ion microprobe. Samples come from 45 different igneous rocks (365 zircons), as well as zircon megacrysts (84) from kimberlite, Early Archean detrital zircons (32), and zircon reference materials (3). Samples were chosen to represent a large range of igneous rock compositions. Most of the zircons contain less than 20 ppm Ti. Apparent temperatures for zircon crystallization were calculated using the Ti-in-zircon thermometer (Watson et al. 2006, Contrib Mineral Petrol 151:413–433) without making corrections for reduced oxide activities (e.g., TiO₂ or SiO₂), or variable pressure. Average apparent Ti-in-zircon temperatures range from 500° to 850°C, and are lower than either zircon saturation temperatures (for granitic rocks) or predicted crystallization temperatures of evolved melts (∼15% melt residue for mafic rocks). Temperatures average: 653 ± 124°C (2 standard deviations, 60 zircons) for felsic to intermediate igneous rocks, 758 ± 111°C (261 zircons) for mafic rocks, and 758 ± 98°C (84 zircons) for mantle megacrysts from kimberlite. Individually, the effects of reduced or , variable pressure, deviations from Henry’s Law, and subsolidus Ti exchange are insufficient to explain the seemingly low temperatures for zircon crystallization in igneous rocks. MELTs calculations show that mafic magmas can evolve to hydrous melts with significantly lower crystallization temperature for the last 10–15% melt residue than that of the main rock. While some magmatic zircons surely form in such late hydrous melts, low apparent temperatures are found in zircons that are included within phenocrysts or glass showing that those zircons are not from evolved residue melts. Intracrystalline variability in Ti concentration, in excess of analytical precision, is observed for nearly all zircons that were analyzed more than once. However, there is no systematic change in Ti content from core to rim, or correlation with zoning, age, U content, Th/U ratio, or concordance in U-Pb age. Thus, it is likely that other variables, in addition to temperature and , are important in controlling the Ti content of zircon. The Ti contents of igneous zircons from different rock types worldwide overlap significantly. However, on a more restricted regional scale, apparent Ti-in-zircon temperatures correlate with whole-rock SiO₂ and HfO₂ for plutonic rocks of the Sierra Nevada batholith, averaging 750°C at 50 wt.% SiO₂ and 600°C at 75 wt.%. Among felsic plutons in the Sierra, peraluminous granites average 610 ± 88°C, while metaluminous rocks average 694 ± 94°C. Detrital zircons from the Jack Hills, Western Australia with ages from 4.4 to 4.0 Ga have apparent temperatures of 717 ± 108°C, which are intermediate between values for felsic rocks and those for mafic rocks. Although some mafic zircons have higher Ti content, values for Early Archean detrital zircons from a proposed granitic provenance are similar to zircons from many mafic rocks, including anorthosites from the Adirondack Mts (709 ± 76°C). Furthermore, the Jack Hills zircon apparent Ti-temperatures are significantly higher than measured values for peraluminous granites (610 ± 88°C). Thus the Ti concentration in detrital zircons and apparent Ti-in-zircon temperatures are not sufficient to independently identify parent melt composition. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Impact of early prehistoric farming on chironomid communities in northwest Ireland     

Karen J. Taylor  Aaron P. Potito  David W. Beilman  Beatrice Ghilardi  Michael O’Connell 《Journal of Paleolimnology》2017,57(3):227-244

This study explored the utility and performance of chironomid (Diptera: Chironomidae) autecology in the investigation of prehistoric farming impacts on freshwater lake systems. Chironomid subfossils, lake sediment geochemistry (δ¹³C, δ¹⁵N and C:N), pollen and macroscopic charcoal analyses were used in a comparative limnological assessment of three archaeologically rich study sites in northwest Ireland. At all three study sites, pastoral farming and its associated nutrient inputs, as represented by non-arboreal pollen indicative of grassland/pasture (NAPp) and lake sediment geochemistry, are concomitant with increases in eutrophic chironomid taxa. Redundancy analysis (RDA) and partial RDAs established that δ¹⁵N and NAPp were controlling factors of chironomid community compositional change during the Neolithic (4000–2500 BC) and Bronze Age (2500–600 BC). Bronze Age farming had a considerably greater impact on the lake systems than Neolithic farming, as indicated by a higher proportion of eutrophic taxa and increases in δ¹⁵N, C:N and δ¹³C values, consistent with increased erosion and agricultural inputs. Findings emphasise the importance of identifying the natural, pre-impacted state of a lake system to determine the extent of agricultural impact accurately. The timing and magnitude of change show that Neolithic and Bronze Age farming exhibited a strong control over chironomid communities at all three sites.  相似文献   

Runoff generation in a sandy area—the nizzana sands,Western Negev,Israel     

A. Yair 《地球表面变化过程与地形》1990,15(7):597-609

This paper presents the results of sprinkling experiments conducted over the lower part of vegetated and crusted linear dunes as well as over flat playa surfaces that appear in the interdune corridors. Data obtained show that these two surface units respond quickly to rainstorms. Runoff generation can be expected for any storm exceeding 2-3 mm and runoff coefficients are high. When the topsoil algal crust, 1 to 2 mm thick, is removed from the surface of the dune, infiltration increases drastically and eliminates any possibility of runoff generation under present-day rainfall conditions. This data may be of great help in the understanding of the geomorphology and sedimentary sequence of the corridors separting linear dunes.  相似文献   

Water policy,trust and governance in the Murray-Darling Basin     

Margaret Alston  Kerri Whittenbury  Deb Western  Aaron Gosling 《The Australian geographer》2016,47(1):49-64

Concerns for river health in the Murray-Darling Basin (MDB) area and shifting priorities for water use have led to a significant process of water reform over the last decade. The MDB area, also known as the food bowl of Australia, produces much of the country's food and is home to a significant portion of the population. A long-term drought, historical over-allocation of water for irrigation and climate variability have led to mounting concerns about the long-term viability of the rivers. While the reform process has resulted in the Commonwealth government taking control of the rivers from the States, it has also been influenced by changes in governments and consequent shifts in water allocation priorities from a privileging of agriculture to a broader approach encompassing economic, environmental and social concerns. This had led to uncertainty for the people and communities in the Basin and some confusion between the various layers of governance structures. This paper presents the results of exploratory research conducted with key, high-level stakeholders involved in water reform to examine their perceptions of the evolving water policy process. Despite agreement amongst stakeholders that returning water to the environment to ensure river health is critical, our research reveals significant tensions between stakeholders concerning the evolving process, particularly centred on the potential social outcomes and fairness and equity. This suggests the need for more integrated and transparent governance structures, attention to levels of trust between partners and a common vision that incorporates environmental, economic and social goals.  相似文献   

Can severe rain events over the Mediterranean region be detected through simple numerical indices?   总被引：1，自引：0，他引：1  

B. Ziv  N. Harats  E. Morin  Y. Yair  U. Dayan 《Natural Hazards》2016,83(2):1197-1212

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Influence of snow and soil moisture initialization on sub-seasonal predictability and forecast skill in boreal spring   总被引：1，自引：0，他引：1  

Jaison Ambadan Thomas  Aaron A. Berg  William J. Merryfield 《Climate Dynamics》2016,47(1-2):49-65

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Cloud cover climatologies in the Mediterranean obtained from satellites,surface observations,reanalyses, and CMIP5 simulations: validation and future scenarios     

Aaron Enriquez-Alonso  Arturo Sanchez-Lorenzo  Josep Calbó  Josep-Abel González  Joel R. Norris 《Climate Dynamics》2016,47(1-2):249-269

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The CM carbonaceous chondrite regolith Diepenveen     

Marco Langbroek  Peter Jenniskens  Leo M. Kriegsman  Henk Nieuwenhuis  Niek De Kort  Jacob Kuiper  Wim Van Westrenen  Michael E. Zolensky  Karen Ziegler  Qing‐Zhu Yin  Matthew E. Sanborn  Josh Wimpenny  Akane Yamakawa  Sebastiaan J. De Vet  Matthias M. M. Meier  Kees C. Welten  Kunihiko Nishiizumi  Marc W. Caffee  Aaron S. Burton  Jason P. Dworkin  Daniel P. Glavin  Qinghao Wu  Richard N. Zare  Alexander Ruf  Mourad Harir  Philippe Schmitt‐Kopplin   《Meteoritics & planetary science》2019,54(7):1431-1461

A carbonaceous chondrite was recovered immediately after the fall near the village of Diepenveen in the Netherlands on October 27, 1873, but came to light only in 2012. Analysis of sodium and poly‐aromatic hydrocarbon content suggests little contamination from handling. Diepenveen is a regolith breccia with an overall petrology consistent with a CM classification. Unlike most other CM chondrites, the bulk oxygen isotopes are extremely ¹⁶O rich, apparently dominated by the signature of anhydrous minerals, distributed on a steep slope pointing to the domain of intrinsic CM water. A small subset plots closer to the normal CM regime, on a parallel line 2 ‰ lower in δ¹⁷O. Different lithologies in Diepenveen experienced varying levels of aqueous alteration processing, being less aqueously altered at places rather than more heated. The presence of an agglutinate grain and the properties of methanol‐soluble organic compounds point to active impact processing of some of the clasts. Diepenveen belongs to a CM clan with ~5 Ma CRE age, longer than most other CM chondrites, and has a relatively young K‐Ar resetting age of ~1.5 Ga. As a CM chondrite, Diepenveen may be representative of samples soon to be returned from the surface of asteroid (162173) Ryugu by the Hayabusa2 spacecraft.  相似文献