BARGEN continuous GPS data across the eastern Basin and Range province, and implications for fault system dynamics   总被引：1，自引：0，他引：1  

Nathan A. Niemi  Brian P. Wernicke  Anke M. Friedrich  Mark Simons  Richard A. Bennett  James L. Davis 《Geophysical Journal International》2004,159(3):842-862

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Aquifer prioritization for ambient ground water monitoring   总被引：1，自引：0，他引：1  

Marjorie E. Bedessem  Brenda Casey  Kevin Frederick  Nathan Nibbelink 《Ground Water Monitoring & Remediation》2005,25(1):150-158

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Simple Spectrophotometric Determination of Ferrous Iron in Twelve French Geochemical Reference Standards     

Nathan W. BOWER 《Geostandards and Geoanalytical Research》1984,8(1):61-62

Iron (II) oxide in silicate rocks can readily be measured after digestion with HF and HCl by reaction with KI and KIO₃. The iodine produced during the digestion is trapped in CCl₄ and measured at 512 nm spectrophotometrically. Results for ten accepted and two new geochemical reference standards are presented.  相似文献   

Dauphiné twinning and texture memory in polycrystalline quartz. Part 1: Experimental deformation of novaculite     

Hans-Rudolf Wenk  Erik Rybacki  Georg Dresen  Ivan Lonardelli  Nathan Barton  Hermann Franz  Gabriela Gonzalez 《Physics and Chemistry of Minerals》2006,33(10):667-676

Mechanical Dauphiné twinning in quartz has been of long-standing interest, both in single crystals and polycrystalline aggregates. This study investigates texture development in fine-grained quartz rock novaculite with no initial texture using compression experiments conducted in the Paterson gas apparatus to explore the influence of stress and temperature. Texture patterns are measured with time-of-flight neutron diffraction and hard synchrotron X-rays, analyzing diffraction data with the Rietveld method. Similar texture patterns are observed as described previously but the new results establish a profound influence of temperature and document that twinning initiates at stresses less than 50 MPa. Possibilities of using Dauphiné twinning as a paleopiezometer in quartz-bearing rocks are discussed.  相似文献   

Seismic reflection and tomographic velocity model constraints on the evolution of the Tofino forearc basin, British Columbia     

Nathan Hayward  Andrew J. Calvert 《Geophysical Journal International》2007,168(2):634-646

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Metal-silicate partitioning of cesium: Implications for core formation     

Nathan M. Mills  David S. Draper 《Geochimica et cosmochimica acta》2007,71(16):4066-4081

Here we present the first set of metal-silicate partitioning data for Cs, which we use to examine whether the primitive mantle depletion of Cs can be attributed to core segregation. Our experiments independently varied pressure from 5 to 15 GPa, temperature from 1900 to 2400 °C, metallic sulfur content from pure Fe to pure FeS, silicate melt polymerization, expressed as a ratio of non-bridging oxygens to tetrahedrally coordinated cations (nbo/t) from 1.26 to 3.1, and fO₂ from two to four log units below the iron-wüstite buffer. The most important controls on the partitioning behavior of alkalis were the metallic sulfur content, expressed as X_S, and the nbo/t of the silicate liquid. Normalization of X_S to 0.5 yielded the following expressions for D-values as a function of nbo/t: log D_Na = −2.0 + 0.44 × (nbo/t), log D_K = −2.4 + 0.67 × ( nbo/t), and log D_Cs = −3.2 + 1.17 × (nbo/t). Normalization of nbo/t to 2.7 resulted in the following equations for D-values as a function of S content: log D_Na = −4.1 + 6.4 × X_S, log D_K = −7.7 + 13.9 × X_S, and log D_Cs = −12.1 + 23.3 × X_S.There appears to be a negative pressure effect up to 15 GPa, but it should be noted that this trend was not present before normalization, and is based on only two measurements. There is a positive trend in cesium’s metal-silicate partition coefficient with increasing temperature. D_Cs exhibits the largest change and increased by a factor of three over 500 °C. The effect of oxygen fugacity has not been precisely determined but in general, lowering fO₂ by two log units resulted in a rise in all D-values of approximately an order of magnitude. In general, the sensitivity of partition coefficients to changing parameters increased with atomic number.The highest D-value for Cs observed in this study is 0.345, which was obtained at nbo/t of 2.7 and a metal phase of pure FeS. This metallic composition has far more S than has been suggested for any credible core-forming metal. We therefore conclude that the depletion of Cs in Earth’s mantle is either caused by radically different behavior of Cs at pressures higher than 15 GPa or is not related to core formation. Even so, we have shown that a planet with a sufficient S inventory may incorporate significant amounts of alkali elements into its core.  相似文献   

Single-Well Injection-Drift Test to Estimate Groundwater Velocity     

Charles Paradis  Nathan Van Ee  Kendyl Hoss  Cullen Meurer  Aaron Tigar  Paul Reimus  Raymond Johnson 《Ground water》2022,60(4):565-570

A simple algebraic equation is presented here to estimate the magnitude of groundwater velocity based on data from a single-well injection-drift test thereby eliminating the time-consuming and costly extraction phase. A volume of tracer-amended water was injected by forced-gradient into a single well followed by monitoring of the conservative solute tracers under natural-gradient conditions as their upgradient portions drifted back through the well. The breakthrough curve data from the single well during the drift phase was analyzed to determine the mean travel times of the tracers. The estimated mean upgradient travel distance back through the single well and the mean travel times of the tracers were used in a simple algebraic equation to estimate groundwater velocity. The groundwater velocity based on the single-well injection-drift test was estimated to be approximately 0.64 ft per day. Two transects of observation wells were used to monitor the natural-gradient tracer transport downgradient of the injection well. The one-dimensional, or dual-well, transport of the tracer from the injection well to the nearest downgradient observation well indicated that the groundwater velocity was 0.55 ft per day. The two-dimensional, or multi-well, transport of the center of mass of the tracers indicated that the groundwater velocity was 0.60 ft per day; the dual- and multi-well results were in excellent agreement with those from the single-well and validated the simple algebraic equation. The new single-well method presented here is relatively simple, rapid, and does not require an extraction phase.  相似文献   

Late‐Summer Peak in Sediment Accumulation in Two Lakes with Contrasting Watersheds,Alaska          下载免费PDF全文

David Fortin  Darrell S. Kaufman  Megan Arnold  Erik Schiefer  Nathan Hawley 《Geografiska Annaler: Series A, Physical Geography》2015,97(4):709-719

The timing of clastic sedimentation in two glacial‐fed lakes with contrasting watersheds was monitored using sequencing sediment traps for two consecutive years at Allison Lake (Chugach Range, Alaska) and four months at Shainin Lake (Brooks Range, Alaska). Shainin Lake is a weakly stratified lake fed by distant glaciers, whereas Allison Lake is more strongly stratified and fed predominantly by proximal glaciers. At Shainin Lake, sediment accumulation started in late June and reached its maximum in mid‐August, just before lake mixing and during a period of low river discharge. The grain size of the sediment reaching the sediment trap in Shainin Lake was homogenous throughout the summer. At Allison Lake, pulsed sedimentation of coarse particles during late summer and early fall storms were superimposed on the fine‐grained sedimentation pattern similar to that observed at Shainin Lake. These storms triggered underflows that were observed in the thermal structure of the lake and deposited abundant sediment. The sequencing sediment traps reveal a lag between fluvial discharge and sediment deposition at both lakes, implying limitations to interpreting intra‐annual sedimentary features in terms of inflow discharge.  相似文献   

Use of the discharge-weighted average velocity in studies of the frictional energy loss of streamflow     

Nathan K. Lewis 《地球表面变化过程与地形》1997,22(4):329-336

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Evaluating social vulnerability indicators: criteria and their application to the Social Vulnerability Index     

Spielman  Seth E.  Tuccillo  Joseph  Folch  David C.  Schweikert  Amy  Davies  Rebecca  Wood  Nathan  Tate  Eric 《Natural Hazards》2020,100(1):417-436

Natural Hazards - As a concept, social vulnerability describes combinations of social, cultural, economic, political, and institutional processes that shape socioeconomic differentials in the...  相似文献