Geochemistry of tin, tungsten and molybdenum in Swedish proterozoic granitoids: Their potential use in regional mineral exploration     

K.-M. Drake 《Journal of Geochemical Exploration》1983,19(1-3)

The primary aim of this broad regional study is to statistically determine the Li-Sn-W-Mo-bearing potential of various granitoids using geochemical criteria. Computer based, univariate and multivariate statistical methods are applied to major- and trace-element data from about 660 granitic rock samples and over 800 major element analyses, selected from the Swedish geological literature. The granitoids are subdivided following earlier geotectonic chronologic and newer geochemical-statistical principles.Most granite types occurring in known Sn-W mineralized areas, except the granites around the W deposit of Baggetorp, were identified as potentially W-Sn-bearing. That is, they show significantly high mean and variance values for W and/or Sn as well as promising values of the probability parameters for these elements, compared to corresponding statistics for a calculated Swedish average granitoid (SAG).Evidence of very high total variability of Li, Sn and W within the individual granite types suggests the need for further tests, to control the variability errors due to sampling and preparation and errors of chemical analysis. These sources of error may obscure natural elemental heterogeneity of the granite type that is of interest in geochemical prospecting.Interpretations of Sn, W and Li frequency distribution patterns, petrochemical trends and multivariate similarity tests suggest that the primary chemistry of the granitoids is overprinted by (a) postmagmatic processes of broad regional nature, which have similarly affected the individual granite types, and (b) a wide variety of secondary alterations of local character. These conclusions imply that potential Sn and W deposits may be sought within all Swedish Proterozoic granitoids and their within all Swedish Proterozoic granitoids and their immediate sorroundings, where susch processes have redistributed and concentrated these where such processes have redistributed and concentrated these elements. However, the granites which are highly differentiated, Sn-W-Li-U-Th-F-enriched, and strongly and strongly magnetic are particularly promising target areas for further, extensive rock-geochemical prospecting and other exploration surveys. rock-geochemical prospecting and other exploration surveys.  相似文献   

Experimental investigations of trace element fractionation in iron meteorites,II: The influence of sulfur     

John H. Jones  Michael J. Drake 《Geochimica et cosmochimica acta》1983,47(7):1199-1209

We have investigated the partitioning of Ir. Ge, Ga, W, Cr, Au, P, and Ni between solid metal and metallic liquid as a function of temperature and S-concentration of the metallic liquid. Partition coefficients for siderophile elements such as Ir, W, Ga and Ge increase by factors of 10–100 as the Sconcentration of the metallic liquid increases from 0–30 wt%. Partition coefficients for other siderophile elements such as Ni, Au and P increase by only factors of 2–3. In contrast, partition coefficients for the more chalcophile element Cr decrease. These experimentally-determined partition coefficients have been used in conjunction with a fractional crystallization model to reproduce the geochemical behavior of Ni, P, Au and Ir during the magmatic evolution of groups IIAB, IIIAB, IVA and IVB iron meteorites. The mean S-concentration for each group increases in the order IVB, IVA, IIIAB, IIAB, in accord with cosmochemical prediction. However, we are unable to reproduce the geochemical behavior of Ge, Ga, W and Cr in an internally consistent way. We conclude that the magmatic histories of these iron meteorite groups are more complex than has been generally assumed.  相似文献   

DNAPL Removal from a Heterogeneous Alluvial Aquifer by Surfactant- Enhanced Aquifer Remediation     

John T. Londergan  Hans W. Meinardus  Paul E. Manner  Richard E. Jackson  Chris L. Brown  Varadarajan Dwarakanath  Gary A. Pope  Jon S. Ginn  Sam Taffinder 《Ground Water Monitoring & Remediation》2001,21(3):71-81

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A SIMPLIFIED APPROACH TO MODELING 3D SEDIMENT-LADEN TURBULENT FLOWS     

Donghuo ZHOU  Sam S.Y.WANG 《国际泥沙研究》1996,(1)

ＡＳＩＭＰＬＩＦＩＥＤＡＰＰＲＯＡＣＨＴＯＭＯＤＥＬＩＮＧ３ＤＳＥＤＩＭＥＮＴ－ＬＡＤＥＮＴＵＲＢＵＬＥＮＴＦＬＯＷＳＤｏｎｇｈｕｏＺＨＯＵａｎｄＳａｍＳ．Ｙ．ＷＡＮＧＡｂｓｔｒａｃｔ：Ａ３－ｄｎｕｍｅｒｉｃａｌｍｏｄｅｌｆｏｒｓｉｍｕｌａｔｉｎｇｓ...  相似文献   

Some exact solutions for the flow of fluid through tubes with uniformly porous walls     

Ronald L. Drake 《Pure and Applied Geophysics》1972,94(1):248-259

Summary This paper considers an incompressible fluid flowing through a straight, circular tube whose walls are uniformly porous. The flow is steady and one dimensional. The loss of fluid through the wall is proportional to the mean static pressure in the tube. Several formulations of the wall shear stress are considered; these formulations were motivated by the results from Hamel's radial flow problem, boundary layer flows/and boundary layer suction profiles. For each of these formulations exact solutions for the mean axial velocity and the mean static pressure of the fluid are obtained. Sample results are plotted on graphs. For the constant wall shear stress problem, the theoretical solutions compare favorably with some experimental results.Notations A, B, D, E constant parameters - a, b constant parameters - Ai(z), Bi(z) Airy functions - Ai, Bi derivatives of Airy functions - k constant of proportionality betweenV andp - L length of pores - p,p mean static pressure - p ₀ static pressure outside the tube - p ₀ value ofp atx=0 - Q constant exponent - R inside radius of the tube - T wall shear stress - T ₀ shear parameter - t wall thickness - U free stream velocity - ,u mean axial velocity - u ₀ value ofu atx=0 - V,V mean seepage velocity through the wall - v ₀ mean seepage velocity - x,x axial distance along the tube - z transformed axial distance - z ₀ value ofz atx=0 - mean outflow angle through the wall - cos - density of the fluid - wall shear stress - dynamic viscosity of the fluid - over-bar dimensional terms - no bar nondimensional terms The National Center for Atmospheric Research is sponsored by the National Science Foundation  相似文献   

A study of time dependence during serial needle ice events     

Dr. Sam I. Outcalt 《Meteorology and Atmospheric Physics》1970,19(3):329-337

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The climatonomy of a needle ice event: An experiment in simulation climatology     

Dr. Sam I. Outcalt 《Theoretical and Applied Climatology》1971,19(3):325-338

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The effects of rock uplift and rock resistance on river morphology in a subduction zone forearc,Oregon, USA     

Sam VanLaningham  Andrew Meigs  Chris Goldfinger 《地球表面变化过程与地形》2006,31(10):1257-1279

Relationships between riverbed morphology, concavity, rock type and rock uplift rate are examined to independently unravel the contribution of along-strike variations in lithology and rates of vertical deformation to the topographic relief of the Oregon coastal mountains. Lithologic control on river profile form is reflected by convexities and knickpoints in a number of longitudinal profiles and by general trends of concavity as a function of lithology. Volcanic and sedimentary rocks are the principal rock types underlying the northern Oregon Coast Ranges (between 46°30′ and 45°N) where mixed bedrock–alluvial channels dominate. Average concavity, θ, is 0·57 in this region. In the alluviated central Oregon Coast Ranges (between 45° and 44°N) values of concavity are, on average, the highest (θ = 0·82). South of 44°N, however, bedrock channels are common and θ = 0·73. Mixed bedrock–alluvial channels characterize rivers in the Klamath Mountains (from 43°N south; θ = 0·64). Rock uplift rates of ≥0·5 mm a⁻¹, mixed bedrock–alluvial channels, and concavities of 0·53–0·70 occur within the northernmost Coast Ranges and Klamath Mountains. For rivers flowing over volcanic rocks θ = 0·53, and θ = 0·72 for reaches crossing sedimentary rocks. Whereas channel type and concavity generally co-vary with lithology along much of the range, rivers between 44·5° and 43°N do not follow these trends. Concavities are generally greater than 0·70, alluvial channels are common, and river profiles lack knickpoints between 44·5° and 44°N, despite the fact that lithology is arguably invariant. Moreover, rock uplift rates in this region vary from low, ≤0·5 mm a⁻¹, to subsidence (<0 mm a⁻¹). These observations are consistent with models of transient river response to a decrease in uplift rate. Conversely, the rivers between 44° and 43°N have similar concavities and flow on the same mapped bedrock unit as the central region, but have bedrock channels and irregular longitudinal profiles, suggesting the river profiles reflect a transient response to an increase in uplift rate. If changes in rock uplift rate explain the differences in river profile form and morphology, it is unlikely that rock uplift and erosion are in steady state in the Oregon coastal mountains. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

The community morphology of skilled migration: the changing role of voluntary and community organisations (VCOs) in the grounding of British migrant identities in Paris (France)     

Sam Scott 《Geoforum》2007,38(4):655-676

Research into skilled migrant communities tends to emphasize the grounding of identities through transnationalism and mobility. Less research has been conducted into how skilled migrants actually ground their identities within the city through everyday social networks. The paper addresses this imbalance by examining the changing significance of British voluntary and community organisations (VCOs) in Paris, France. Combining qualitative and quantitative data, findings show local migrant networks to be important focal points for the British even though migrants’ lives may increasingly be transnational in orientation. The research also shows that in situ social networks are evolving. Specifically, traditional forms of elite expatriate communality are not as omnipotent as they once were, with the popularity of some high-profile British VCOs in Paris declining over recent decades. The paper argues that the link between social dynamism and communal morphology helps explain this shift: as British middle-class lifestyles have fragmented, and as the British migrant population in Paris has grown in scale and scope, so the range of VCOs and associated informal networks has grown. Whilst some skilled migrants still embed within traditional expatriate organisations, Britishness is increasingly grounded elsewhere; both within the city through alternative social networks, and located beyond the city through transnational ties.  相似文献   

Multiple phases of North African humidity recorded in lacustrine sediments from the Fazzan Basin, Libyan Sahara     

S.J. Armitage  N.A. Drake  S. Stokes  A. El-Hawat  M.J. Salem  K. White  P. Turner  S.J. McLaren 《Quaternary Geochronology》2007,2(1-4):181-186

The Fazzan Basin of south-west Libya is at present arid with less than 20 mm of rainfall per annum. However, regionally extensive limestones, lacustrine sands and coquina (fossiliferous carbonate rock) deposits show that the Fazzan Basin previously contained a large palaeolake, indicating that the climate in the past was more humid. Optically stimulated luminescence (OSL) dating techniques have been applied to key lacustrine deposits within the basin in an attempt to provide an internally consistent chronology for this humidity record. Results indicate that palaeolake sediments within the Fazzan Basin record a very long history of palaeohydrological change, ranging from present day arid conditions to humidity capable of sustaining a lake with an approximate area of 76,250 km². The existence of humid periods in mid oxygen isotope stage 5 and the early Holocene is confirmed. An older lacustrine event, tentatively correlated to oxygen isotope stage 11, is also recognized. In addition, evidence is presented for at least two humid phases beyond the age range over which the conventional OSL dating technique is applicable. This study demonstrates that OSL dating of palaeolake sediments within the Fazzan Basin offers the potential to provide a detailed record of North African humidity spanning several glacial–interglacial cycles.  相似文献