河北省南部邯郸-邢台地区西石门矽卡岩型铁矿床金云母40Ar-39 Ar定年及意义     

郑建民谢桂青  刘珺陈懋弘  王三民郭少峰高雄  李广栋 《岩石学报》2007,23(10):2513-2518

西石门铁矿是河北省南部邯郸.邢台地区最大的矽卡岩型铁矿。主要矿石矿物为磁铁矿。对矿石中与磁铁矿共生的金云母的~(40)Ar-~(39)Ar同位素测年结果表明,样品的坪年龄为133.1±1.3Ma,相对应的等时线年龄为133.6±2.5Ma,表明西石门铁矿形成于早白垩世。与宁芜玢岩铁矿和山东莱芜、金岭等地矽卡岩铁矿形成时间一致或相近,其形成的构造背景为岩石圈大规模减薄。  相似文献   

Saturn satellite observations and orbits from the 1980 ring plane crossing     

P.K. Seidelmann  R.S. Harrington  D. Pascu  W.A. Baum  D.G. Currie  J.A. Westphal  G.E. Danielson 《Icarus》1981,47(2):282-287

The ground-based observations of the recently discovered Saturnian satellites, obtained during the 1980 apparition, have been collected from the IAU Circulars and identified with and fit to four orbital groups: (1) the inner pair of coorbital librating satellites, (2) the satellite known as “Dione B” near the L₄ point of Dione-Saturn, (3) the satellites associated with the L₄ and L₅ points of Tethys-Saturn or, alternatively, one satellite unconfortably near the orbit of Tethys, and (4) the F-ring satellites observed by Voyager I.  相似文献   

The dynamical decay of unstable 4-body systems     

R. S. Harrington 《Celestial Mechanics and Dynamical Astronomy》1974,9(4):465-470

Unstable 4-body systems with negative energy can ultimately decay to (1) a binary plus two single stars, (2) two separate binaries, or (3) a stable triple plus a single star. One hundred random 2-dimensional and one hundred random 3-dimensional 4-body systems have been numerically integrated to determine the statistics of the end products. Of the final stable triples and binaries, 19% were triples, which agrees well with observational estimates of the ratio of triples to binaries. The results were essentially the same for 2- and 3- dimensional systems.  相似文献   

Effectiveness of Conservation Reserve Programs and Land ‘Slippage’ in Southwestern Kansas     

Nancy Leathers  Lisa M.B. Harrington 《The Professional geographer》2000,52(1):83-93

Historically land reserve programs have been used to reduce soil erosion. Slippage, which occurs when the number of acres enrolled in a reserve program is not met by an equivalent reduction of acreage in production, has limited reserve success, however. This study addresses the effect of slippage on conservation reserves in southwestern Kansas from 1988–1994. Slippage has varied considerably on both spatial and temporal bases. At one extreme the programs were 100% successful in removing land from production, but at the other extreme, slippage rendered reserve programs nearly useless. Overall, slippage in the study area has greatly reduced conservation reserve effectiveness.  相似文献   

Metallophores and Trace Metal Biogeochemistry     

Stephan M. Kraemer  Owen W. Duckworth  James M. Harrington  Walter D. C. Schenkeveld 《Aquatic Geochemistry》2015,21(2-4):159-195

  相似文献   

Planet X — The current status     

P. K. Seidelmann  R. S. Harrington 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):55-68

Neptune and Pluto were discovered because of predictions derived from the differences between the observations and ephemerides of Uranus, but Pluto wasn't the predicted planet and the discrepancies still exist. This continuing existence of systematic differences between the observations and ephemerides of Uranus and Neptune has led to predictions of a Planet X. The demise of the dinosaurs and the existence of comets have been cited as additional evidence for another celestial object.Therefore, possible bodies have been hypothesized in the outer part of the solar system, or out beyond the solar system, including a binary companion, Nemesis. The theory of relativity and the incompleteness of the law of gravity have also been suggested as explanations for the outer planet discrepancies. Predictions of the possible locations of planet X have been made, with rather large uncertainties, and selected searches of some regions have yielded nothing. IRAS and Pioneer observations exist as additional sources of useful observational data.  相似文献   

Multidate image analysis of forest degradation in Equatorial Africa     

Susan M. Berta  John A. Harrington Jr.  Paul W. Mausel  Robin Graham 《国际地球制图》2013,28(4):57-61

Abstract

In this paper we process diachronic SPOT satellite images acquired with different viewing angles in order to assess the aerosol optical thickness (AOT) spatial distribution over Brescia.

This urban area, located in Northern Italy, is subject to frequent visibility‐reducing smog episodes. AOT was calculated by using the Differential Textural Analysis (DTA) code on a satellite data series consisting by one pollution‐free and various pollution‐loaded SPOT images. The resulting maps showed the horizontal distribution of AOT with a resolution of 500 metres. These maps can be readily integrated with the results obtained by mesoscale modelling, ground measurements, and respond to local scale application requirements. Satellite AOT retrieval compared successfully with available AOT ground‐based measurements and with pollution measurements in the ambient air. In this study the use of diachronic multiangle SPOT imagery allowed us to analyse the effect of the viewing angle variation on AOT retrieval accuracy based on the contrast reduction method.  相似文献   

MAJOR SNOWFALL EVENTS IN THE GREAT PLAINS: TEMPORAL ASPECTS AND RELATIVE IMPORTANCE     

Nancy Leathers  John Harrington Jr. 《自然地理学》2013,34(2):134-151

The purpose of this research is to develop a better understanding of the spatial and temporal aspects of central Great Plains snowstorms by: (1) identifying trends in the frequency of snow events, (2) determining the relative importance of significant snowfalls (those producing snowfall amounts of 10 cm or more), and (3) identifying temporal and/or latitudinal variations in the frequency of significant snowstorms. Using NCDC data from cooperative program weather stations along a north-south transect, summary statistics, correlation coefficients, and frequency histograms were generated. The results provided evidence of a highly variable spatial and temporal record. Significant snowstorms are more critical to total snowfall amounts in Nebraska, Kansas, and Texas. Although strong, regionally coherent temporal trends were not detected, a predominance of January through March snow events was observed. The greater frequency of January snowstorms coincides with the mean position of the polar front, while February and March snowfall frequency reflects the increased incidence of Colorado cyclones. Decadally, snowfall variability corresponds with a change in mean temperatures and predominant upper atmospheric flow that occurred around 1950. This change brought less snow to the Southern and Central Plains states, but more snow to the north. [Key words: snowfall, Great Plains, temporal/spatial variability.]  相似文献   

同位素^131I测西台吉乃尔湖矿区含水层地质参数          下载免费PDF全文

杨海镇马海州  高东林 《盐湖研究》2008,16(1):8-11

盐湖区的水文地质参数特性与淡水区迥然不同。同位素示踪法可以利用西台盐湖区已有的长现井,机动灵活的随时监测含水层水文地质参数;由于介质的特殊性以及卤水性质的垂直差异性,造成水文地质参数的时空可变性;测试结果表明,对于完整井以及深的非完整井,该方法切实有效,但对于很浅的非完整井,测试结果具有很大的随机性。最后,根据测试结果以及有关的水文地质资料,把研究区分成7个渗透系数分区。  相似文献   

陕南勉略宁地区铜厂闪长岩岩石地球化学及SHRIMP锆石 U-Pb同位素年代学   总被引：3，自引：2，他引：1  

叶霖  程增涛  陆丽娜  高伟  潘自平 《岩石学报》2009,25(11):2866-2876

本文对位于陕南勉略宁地区铜厂铜矿区与铜成矿作用有关的闪长岩进行了系统的岩石学、锆石U-Pb年代学和地球化学研究,讨论铜厂岩体的岩石成因、成岩物质来源及其地质意义和与铜厂铜矿床的关系.研究结果表明,铜厂闪长岩属于钙碱性-低钾岩系列岩石,以富大离子亲石元素和贫高场强元素为特征,其稀土配分模式为具Eu负异常和Ce异常不明显的轻稀土富集型,与碧口群海相火山岩具有一定相似性和继承性.闪长岩主要来源于壳源或曾受到地壳物质的强烈混染,并没有经历过显著的结晶分异演化,且与铜成矿有密切的关系,为该区主要成矿物质来源之一.岩体形成的大地构造背景属于碰撞隆起-岛弧火山,成矿作用晚于岩体侵入.铜厂闪长岩的锆石SHRIMP U-Pb同位素年龄为842±6.5Ma,早于秦岭造山带的主造山期.该区晋宁期俯冲-挤压造山作用,形成了碧口岩群岛弧火山岩系,铜厂闪长岩可能属于地层.碧口群细碧角斑岩末期火山侵入杂岩,由碧口群火山岩的局部熔融作用形成,其轻稀土的相对富集可能与岩体继承源岩的稀土特征有关.  相似文献