Estimated changes in wind speed and wind power density over the western High Plains, 1971–2000     

J. Scott Greene  Matthew Chatelain  Mark Morrissey  Steve Stadler 《Theoretical and Applied Climatology》2012,109(3-4):507-518

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Partitioning behavior of trace elements between dacitic melt and plagioclase, orthopyroxene, and clinopyroxene based on laser ablation ICPMS analysis of silicate melt inclusions   总被引：2，自引：0，他引：2  

Matthew J. Severs  James S. Beard  John M. Hanchar  Robert J. Bodnar 《Geochimica et cosmochimica acta》2009,73(7):2123-1266

Partitioning behavior of Sc, Ti, V, Mn, Sr, Y, Zr, Nb, Ba, La, Nd, Sm, Eu, Gd, Dy, Ho, Yb, Hf, and Pb between dacitic silicate melt and clinopyroxene, orthopyroxene, and plagioclase has been determined based on laser ablation-inductively coupled plasma mass spectrometric (LA-ICPMS) analysis of melt inclusions and the immediately adjacent host mineral. Samples from the 1988 eruption of White Island, New Zealand were selected because petrographic evidence suggests that all three mineral phases are in equilibrium with each other and with the melt inclusions. All three phenocryst types are found as mineral inclusions within each of the other phases, and mineral inclusions often coexist with melt inclusions in growth-zone assemblages. Compositions of melt inclusions do not vary between the different host minerals, suggesting that boundary layer processes did not affect compositions of melt inclusions and that post-trapping modifications have not occurred.Partition coefficients were calculated from the host and melt inclusion compositions and results were compared to published values. All trace elements examined in this study except Sr are incompatible in plagioclase, and all measured trace elements except for Mn are incompatible in orthopyroxene. In clinopyroxene, Sc, V, and Mn are compatible, and Y, Ti, HREE, and the MREE are only slightly incompatible. Most partition coefficients overlap the wide range of values reported in the literature, but the White Island data are consistently at the lower end of the range in published values. Results from the literature obtained using modern microanalytical techniques such as secondary ion mass spectrometry (SIMS) or proton induced X-ray emission spectroscopy (PIXE) also fall at the lower end of the published values, whereas partition coefficients determined from bulk analysis of glass and crystals separated from volcanic rocks typically extend to higher values. Rapid crystal growth-rates, crystal zonation, or the presence of accessory mineral inclusions in phenocrysts likely accounts for the wide range and generally higher partition coefficients obtained using bulk sampling techniques. The results for 3+ cations from this study are consistent with theoretical predictions based on a lattice strain model for site occupancy. The results also confirm that the melt inclusion-mineral (MIM) technique is a reliable method for determining partition coefficients, as long as the melt inclusions have not experienced post-entrapment reequilibration.  相似文献   

Placemarks and waterlines: Racialized cyberscapes in post-Katrina Google Earth   总被引：2，自引：0，他引：2  

Michael Crutcher  Matthew Zook   《Geoforum》2009,40(4):523-534

Google Earth was released a few months prior to Hurricane Katrina and became an important tool in distributing information about the damage occurring in New Orleans, albeit not to all parts of society. While Google Earth did not create the economic and racial divides present in society, its use in the post-Katrina context reflect this gulf and have arguably reinforced and recreated it online. This paper has three main objectives. The first is to provide a clear empirical case study of how race remains relevant to the way people use (or do not use) the internet and internet based services. The second is highlighting the power of new online and interactive mapping technologies and demonstrating how these technologies are differentially adopted. The third and final objective is illustrating how any divide in accessing digital technology is not simply a one time event but a constantly moving target as new devices, software and cultural practices emerge. Thus, in addition to highlighting the racial inequalities in US society in general, Hurricane Katrina provides an important window on the way in which race remains a key factor in the access and use of emerging digital technologies.  相似文献   

Nature conservation, rural livelihoods, and territorial control in Andean Ecuador     

Matthew Himley 《Geoforum》2009,40(5):832-842

The Ecuadorian sierra, or Andean region, has during recent decades witnessed a marked expansion of nature conservation initiatives. This paper explores the relations and tensions between this proliferation of conservation interventions and the struggles of rural Andean communities to assert territorial authority and to consolidate their livelihoods. Through an analysis of three rounds of conservation initiatives in an indigenous campesino cooperative in the south-central sierra, I argue for a conceptualization of the outcomes and trajectories of conservation as coproduced through histories of interaction between conservation actors and rural resource users. Within this analytical framework, I underscore the importance of taking into account the agency of rural communities, their historical landscape claims, and the dynamism of their livelihood interests.  相似文献   

The importance of unsaturated zone biogeochemical processes in determining groundwater composition, southeastern Australia     

Matthew Edwards  John Webb 《Hydrogeology Journal》2009,17(6):1359-1374

Analysis of soil, soil water and groundwater in the Mount William Creek catchment, southeastern Australia, shows that Mg²⁺ and Ca²⁺ within infiltrating rainfall are rapidly depleted by plant uptake and adsorption on clay minerals. Na⁺ and K⁺ may exhibit minor enrichment at shallow depths but are quickly readsorbed, so that cation/Cl^– ratios typical of groundwater are observed in soil water within the upper 200 cm of the soil profile for all species. The concentrations of K⁺ and Ca²⁺ in soil and groundwater are more depleted than Na⁺ and Mg²⁺ due to preferential uptake by vegetation. Removal of organic matter results in a continuing, long-term export of all major cations from the soil profiles. The processes of biogeochemical fractionation within the unsaturated zone rapidly modify the cation/Cl^– ratios of infiltrating rainfall to values characteristic of seawater. These mechanisms may have reached steady state, because groundwaters with seawater ion/Cl^– ratios are thousands of years old; the exchange sites on the soil clays are probably saturated, so cations supplied in rainfall are exported in organic matter and incorporated into recharge infiltrating into the groundwater. Much of the chemical evolution of groundwater traditionally attributed to processes within the aquifer is complete by the time recharge occurs; this evolutionary model may have broad application.  相似文献   

White mica trace element and boron isotope evidence for distinctive infiltration events during exhumation of deeply subducted continental crust     

Natalie E. Sievers  Carrie A. Menold  Marty Grove  Matthew A. Coble 《International Geology Review》2017,59(5-6):621-638

ABSTRACT

Previous study of subducted continental crust within the Luliang Shan terrane in Northwest China has documented metasomatic formation of thick, hydrated phengite + garnet-rich selvages at the interface between mafic eclogite blocks and quartzofeldspathic host gneiss. Whole rock concentrations of Cs and Ba within the selvage are enriched by two orders of magnitude relative to the eclogite blocks and host gneiss. We performed in situ ion microprobe analyses of Li, Be, B, Rb, Sr, Cs and Ba and δ¹¹B of phengite within the Luliang Shane terrane to better constrain the source(s) of the infiltrating fluid. The phengite within the selvage are enriched in Li, Cs and Ba and yield δ¹¹B values between ?30‰ and ?9‰, values that are lower than mantle values. High Ba/Rb, Cs/Rb coupled with low B/Be, B/Li and highly negative δ¹¹B values indicate that the high-pressure fluid that formed the selvage was derived from highly devolatilized rocks within the subduction channel. In contrast, muscovite, which crystallized in the adjacent host gneiss during a subsequent lower pressure phase of fluid infiltration at approximately 0.9 GPa depths, has much lower Li, Cs and Ba relative to the high-pressure phengite. These retrograde muscovite have very high concentrations of B (up to 5500 ppm) and Be (up to 50 ppm) and high (?2 to +8‰) δ¹¹B values that are consistent with crystallization from a fluid derived from shallower and less devolatilized regions of the subduction zone. Additional host gneiss samples, regionally distributed and kilometres away from the studied area lack the B-rich signature and indicate that the late stage fluids were likely localized to the region near the studied traverse.  相似文献   

Major Element Chemical Heterogeneity in Geo2 Olivine Microbeam Reference Material: A Spatial Approach to Quantifying Heterogeneity in Primary Reference Materials          下载免费PDF全文

Matthew J. Pankhurst  Richard Walshaw  Daniel J. Morgan 《Geostandards and Geoanalytical Research》2017,41(1):85-91

A 270 spot‐analysis study was conducted across a large (ca. 1200 μm × 1200 μm) chip of Geo2 olivine from a commercially available GEO Mk2 block (P and H Developments 2016 , Standards for EPMA), which revealed an 8.7% relative range in FeO abundance. Interleaved and overlapping grids of different resolutions were measured sequentially to prove spatial patterns are not due to drift or other external sources of error. Results were mapped and interpolated using commercially available geographical information system software, such that composition could be predicted according to location with high accuracy. The simple, systematic zonation pattern observed demonstrates that useful‐sized regions of acceptable homogeneity do exist for some elements. This knowledge allows a user to target individual regions of a characterised chip for use as distinct measurement standards. As analysis times decrease and data sets grow, this approach may maximise laboratory efficiency by characterising large chips and extending time between conventional block repolish and coating, particularly in those cases where the avoidance of prior beam damage is a key concern.  相似文献   

http://dx.doi.org/10.1016/j.gsf.2016.06.008   总被引：1，自引：1，他引：0  

Matthew A. Pasek 《地学前缘(英文版)》2017,8(2):329-335

The mineral schreibersite, (Fe,Ni)₃P, provides a reactive source of phosphorus capable of forming phosphorylated molecules. These molecules may have been an important component of prebiotic chemistry, allowing their build-up and eventual commencement of autopoiesis. Discussed here are potential geochemical routes to providing schreibersite, as a potentially important prebiotic mineral, to the Hadean Earth. Two routes are identified: delivery of phosphides by meteoritic material and the reduction of phosphates to phosphides by high-temperature, low-redox conditions. About 1–10% of all crustal phosphorus is estimated to have been in schreibersite during the Hadean, making the long-term reaction of this mineral with organic-laden water plausible for many years. Ultimately, such conditions would have been conducive to the formation of life as we know it today.  相似文献   

Mud‐rich delta‐scale compound clinoforms in the Triassic shelf of northern Pangea (Havert Formation,south‐western Barents Sea)     

Valentina Marzia Rossi  Niall William Paterson  William Helland‐Hansen  Tore Grane Klausen  Christian Haug Eide 《Sedimentology》2019,66(6):2234-2267

In recent years it has become clear that many shallow‐marine heterolithic and mudstone‐dominated successions are deposited as mud belts forming part of subaqueous deltas that are related to major fluvial sources either upstream or along shore. Here the Havert Formation is presented as an ancient example of this kind of system. The Havert Formation in the south‐western Barents Sea represents shelf margin clinoforms consisting predominantly of heterolithic deposits. Sediments were mainly derived from the east (Ural Mountains), but a smaller system prograded northward from Fennoscandia. The Havert Formation holds a lot of interest due to: (i) its stratigraphic position, directly above the Permo–Triassic boundary and contemporaneous to the emplacement of the Siberian Traps; (ii) the fact that it represents the first siliciclastic input in the south‐western Barents Sea and it shows interaction between Uralian‐derived and Fennoscandian‐derived sediments; and (iii) its hydrocarbon potential. This study is focused on a detailed sedimentological analysis of cored intervals of the (Ural‐derived) Havert Formation, in combination with seismic interpretation, well‐log correlations and palynological analysis of the Havert and overlying Klappmyss formations. The cored intervals belong to the shelf environment of the Havert shelf‐margin clinoforms (300 to 500 m thick). This sedimentological analysis distinguishes six facies associations, spanning from tidally‐influenced channels at the shoreline to mud‐rich subaqueous platform and foresets of the subaqueous delta. Seismic lines and well‐log correlations show the larger‐scale evolution of the Ural‐derived Havert Formation, characterized by episodes of low‐accommodation and high‐accommodation. The palynological analyses provide the first detailed study of the Havert Formation in the Nordkapp Basin, revising its depositional age in the region as Induan to early Olenekian (Smithian). Furthermore, they strengthen the environmental interpretation; palynofacies present on the shelf record flora of tidally‐influenced coastal plains, whereas the palynofacies in the deep‐water slope contain only amorphous organic matter.  相似文献   

Mutual impact of wild and cultured Atlantic salmon in Norway   总被引：1，自引：1，他引：0  

Egidius  Emmy; Hansen  Lars P.; Jonsson  Bror; Naevdal  Gunnar 《ICES Journal of Marine Science》1991,47(3):404-410

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