Laser depth profiling studies of helium diffusion in Durango fluorapatite   总被引：1，自引：0，他引：1  

Matthijs C. van Soest  Brian D. Monteleone  Jeremy W. Boyce 《Geochimica et cosmochimica acta》2011,75(9):2409-161

Ultraviolet lasers coupled with sensitive mass spectrometers provide a useful way to measure laboratory-induced noble gas diffusion profiles in minerals, thus enabling the calculation of diffusion parameters. We illustrate this laser ablation depth profiling (LADP) technique for a previously well-studied mineral-isotopic system: ⁴He in Durango fluorapatite. LADP studies were conducted on oriented, polished slabs from a single crystal that were heated under vacuum to a variety of temperatures between 300 and 450 °C for variable times. The resolved ⁴He profiles exhibited error-function loss as predicted by previous bulk ⁴He diffusion studies. All of the slabs, regardless of crystallographic orientation, yielded modeled diffusivities that are statistically co-linear on an Arrhenius diagram, suggesting no diffusional anisotropy of ⁴He in this material. The data indicate an activation energy of 142.2 ± 5.0 (2σ) kJ/mol and diffusivity at infinite temperature - reported as ln(D₀) - of −4.71 ± 0.94 (2σ) m²/s. These values imply a bulk closure temperature for ⁴He in Durango fluorapatite of 74 °C for a 50 μm radius grain, infinite cylinder geometry, and a cooling rate of 10 °C/Myr.  相似文献   

Pressure effects on the joint elastic‐electrical properties of reservoir sandstones     

Angus I. Best  Jeremy Sothcott  Lucy M. MacGregor 《Geophysical Prospecting》2011,59(3):506-517

We conducted a laboratory study of the joint elastic‐electrical properties of sixty‐three brine‐saturated sandstone samples to assess the likely impact of differential pressure (confining minus pore fluid pressures) in the range 8–60 MPa on the joint interpretation of marine seismic and controlled‐source electromagnetic survey data. The samples showed a wide range of petrophysical properties representative of most sandstone reservoirs. We found that a regression equation comprising both a constant and an exponential part gave a good fit to the pressure dependence of all five measured geophysical parameters (ultrasonic P‐ and S‐wave velocity, attenuation and electrical resistivity). Electrical resistivity was more pressure‐sensitive in clay‐rich sandstones with higher concentrations of low aspect ratio pores and micropores than in clean sandstones. Attenuation was more pressure‐sensitive in clean sandstones with large open pores (macropores) than in clay‐rich sandstones. Pore shape did not show any influence on the pressure sensitivity of elastic velocity. As differential pressure increases, the effect of the low aspect ratio pores and micropores on electrical resistivity becomes stronger than the effect of the macropores on attenuation. Further analysis of correlations among the five parameters as a function of pressure revealed potentially diagnostic relationships for geopressure prediction in reservoir sandstones.  相似文献   

Joint elastic‐electrical properties of reservoir sandstones and their relationships with petrophysical parameters     

Angus I. Best  Jeremy Sothcott  Lucy M. MacGregor 《Geophysical Prospecting》2011,59(3):518-535

We measured in the laboratory ultrasonic compressional and shear‐wave velocity and attenuation (0.7–1.0 MHz) and low‐frequency (2 Hz) electrical resistivity on 63 sandstone samples with a wide range of petrophysical properties to study the influence of reservoir porosity, permeability and clay content on the joint elastic‐electrical properties of reservoir sandstones. P‐ and S‐wave velocities were found to be linearly correlated with apparent electrical formation factor on a semi‐logarithmic scale for both clean and clay‐rich sandstones; P‐ and S‐wave attenuations showed a bell‐shaped correlation (partial for S‐waves) with apparent electrical formation factor. The joint elastic‐electrical properties provide a way to discriminate between sandstones with similar porosities but with different clay contents. The laboratory results can be used to estimate sandstone reservoir permeability from seismic velocity and apparent formation factor obtained from co‐located seismic and controlled source electromagnetic surveys.  相似文献   

Temperature Inverted Haloclines Provide Winter Warm-Water Refugia for Manatees in Southwest Florida     

Bradley M. Stith  James P. Reid  Catherine A. Langtimm  Eric D. Swain  Terry J. Doyle  Daniel H. Slone  Jeremy D. Decker  Lars E. Soderqvist 《Estuaries and Coasts》2011,34(1):106-119

Florida manatees (Trichechus manatus latirostris) overwintering in the Ten Thousand Islands and western Everglades have no access to power plants or major artesian springs that provide warm-water refugia in other parts of Florida. Instead, hundreds of manatees aggregate at artificial canals, basins, and natural deep water sites that act as passive thermal refugia (PTR). Monitoring at two canal sites revealed temperature inverted haloclines, which provided warm salty bottom layers that generally remained above temperatures considered adverse for manatees. At the largest PTR, the warmer bottom layer disappeared unless significant salt stratification was maintained by upstream freshwater inflow over a persistent tidal wedge. A detailed three-dimensional hydrology model showed that salinity stratification inhibited vertical convection induced by atmospheric cooling. Management or creation of temperature inverted haloclines may be a feasible and desirable option for resource managers to provide passive thermal refugia for manatees and other temperature sensitive aquatic species.  相似文献   

Towards climate adaptation and coastal governance in Ireland: Integrated architecture for effective management?     

Maria Falaleeva  Cathal O'Mahony  Stefan Gray  Margaret Desmond  Jeremy Gault  Valerie Cummins 《Marine Policy》2011

Coastal environments are susceptible to a range of impacts arising from medium and long-term climate change. However, as Ireland's population and industrial centres are concentrated in coastal locations, Ireland's coastal communities will be particularly vulnerable to the impacts of climate change. Therefore, making the best use of existing knowledge to inform the establishment of governance structures capable of facilitating the measures and actions which may soon be required is a national imperative. Coastal communities worldwide have turned to integrated coastal zone management (ICZM) as a process to deliver sustainable development. This paper explores how experience gained from ICZM implementation can be harnessed to inform the development and implementation of climate adaptation policies, with a particular focus on the coastal zone. Using the principles and conceptual basis of Earth System Governance – an emerging approach to analyse complexity of governance under global environmental change – the paper maps the architecture of ICZM and climate governance in Ireland. The research identifies the main barriers to, and opportunities for, integrated application of the two policy domains. Barriers include the fragmentation of governance structures and responsibilities of key stakeholders, a lack of coordinated support for ICZM implementation at the national level, and a relatively weak awareness of the specifics of adaptation at the local level. Opportunities include the availability of expertise gathered from phases of ICZM implementation in Ireland, which encompasses mechanisms for science-policy integration, and invaluable experience of stakeholder participation and interaction. Current political and scientific support at national and EU levels give an additional impetus to climate research and actions which may bring additional opportunities and resources to coastal governance in Ireland.  相似文献   

RegCM3对东亚环流和中国气候模拟能力的检验   总被引：31，自引：1，他引：31  

张冬峰  欧阳里程  高学杰  赵宗慈  PALJeremy S  GIORGI Filippo 《热带气象学报》2007,23(5):444-452

使用RegCM3区域气候模式,嵌套ERA40再分析资料,对东亚地区进行了15年（1987～2001年）时间长度的数值积分试验,分析了模式对东亚平均环流及中国地区气温和降水的模拟。结果表明,模式对东亚平均环流的特征和中国地区降水、地面气温的年、季地理分布和季节变化特征均具有一定的模拟能力,对气温和降水年际变率的模拟也较好。此外模式模拟在测站稀少地区,可以提供局地如降水分布更可靠的信息。模式对气温的模拟存在1-3℃的系统性冷偏差;对中国地区降水地理分布的模拟也存在一定偏差,如对年平均降水的模拟中,降水最大值位置与观测有一定差距,特别是对冬季降水中心的模拟存在较大偏差。模式模拟的夏季降水,在中国北方地区总体偏大100-200 mm,南方总体偏小100-200 mm。模式对地面气温的模拟效果好于降水。  相似文献   

Increased Magmatic Water Content—the Key to Porphyry Cu-Mo ± Au Formation in the Gangdese Belt, Tibet     

WANG Rui  RICHARDS Jeremy  HOU Zengqian  YANG Zhiming 《《地质学报》英文版》2013,87(Z1):796-797

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Review of tufa deposition and palaeohydrological conditions in the White Peak,Derbyshire, UK: implications for Quaternary landscape evolution     

Vanessa J. Banks  Peter F. Jones  David J. Lowe  Jonathan R. Lee  Jeremy Rushton  Michael A. Ellis 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(1):117-129

This review considers the geological and geomorphological context of tufa barrages that occupy buried valley settings in the Wye catchment, Derbyshire. It describes the potential relationship of the tufa with locations of hypothesised river captures and inception horizon-guided groundwater flow paths. Tufa barrage development is associated with steps in the bedrock, which may be related to knick-point recession during river capture. Broad estimates of valley incision have been calculated from previously dated deposits. These support current interpretations of particularly significant effective base-level lowering during the Anglian and Devensian stages of the Quaternary and have the potential to add to the knowledge of regional uplift histories.  相似文献   

The deglaciation of eastern Scotland: cosmogenic 10Be evidence for a Lateglacial stillstand     

Jeremy Everest  Peter Kubik 《第四纪科学杂志》2006,21(1):95-104

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The birthrate of magnetars     

Ramandeep Gill  Jeremy Heyl † 《Monthly notices of the Royal Astronomical Society》2007,381(1):52-58

Magnetars, neutron stars with ultrastrong magnetic fields  ( B ∼ 10¹⁴−10¹⁵G)  , manifest their exotic nature in the form of soft gamma-ray repeaters and anomalous X-ray pulsars. This study estimates the birthrate of magnetars to be ∼0.22 per century with a Galactic population comprising ∼17 objects. A population synthesis was carried out based on the five anomalous X-ray pulsars detected in the ROSAT All Sky Survey by comparing their number to that of massive OB stars in a well-defined volume. Additionally, the group of seven X-ray dim isolated neutron stars detected in the same survey were found to have a birthrate of ∼2 per century with a Galactic population of ∼22 000 objects.  相似文献