Withrow — a New Iron Meteorite from the State of Washington     

WILLIAM F. READ  ELLEN D. GRIZZLE  WALTER M. GRIZZLE 《Meteoritics & planetary science》1967,3(4):219-229

Abstract. About 1950 an iron meteorite weighing 19 1/4 pounds was found a mile west of Withrow in Douglas County, Washington. The discovery site happens to be a little less than 5 miles SSE from that of the Waterville meteorite. However, the two irons are definitely not from a single fall. Withrow is a medium octahedrite showing secondary recrystallization of the type ascribed to cosmic heating. It was apparently picked up not more than a few years after it fell. Weathering is minimal, and effects of passage through the atmosphere are well preserved.  相似文献   

Two-stage corona growth during Precambrian granulite facies metamorphism of Smitbson Bjerge, north-west Greenland     

ADAM A. GARDE  WILLIAM E. GLASSLEY  ALLEN P. NUTMAN 《Journal of Metamorphic Geology》1984,2(3):237-247

Abstract Late Archaean orthogneisses and aluminous and iron-rich metasedimentary rocks intruded by anorthosite and a ferrodiorite-granite suite were completely recrystallized during Proterozoic granulite facies metamorphism. Geobarometry and geothermometry indicate P-T conditions of around 7.5kbar. 700°C, with a CO₂-rich fluid phase and logfO₂ at or below -16. A two-stage high-grade history of near isochemical corona growth is preserved in metasediments with the reaction cycle opx + plag + H₂O → hbl+gar+SiO₂→ opx+plag+H₂O. End product compositions resemble those of the initial phases, and the only mobile components were SiO₂ and/or H₂O. The coronas reflect shortlived fluctuations in chemical activity at essentially constant P and T, contrary to simple progressive change in equilibrium parameters recorded by most corona-bearing textures.  相似文献   

Troilite Push-Out Pit on the Surface of a Freshly-Fallen Iron Meteorite     

WILLIAM F. READ  ELLEN D. GRIZZLE  WALTER M. GRIZZLE 《Meteoritics & planetary science》1967,3(4):231-234

Abstract. The surface of the Withrow meteorite shows an unusual pit about two inches in diameter. This is explained as the result of pushing out of a plug of metal by expansion of an underlying troilite nodule.  相似文献   

BOX-COX TRANSFORMATIONS IN THE ANALYSIS OF COMPOSITIONAL DATA     

WILLIAM S.RAYENS CIDAMBI SRINIVASAN Department of Statistics  University of Kentucky  Lexington  KY  U.S.A. 《地理学报(英文版)》1991,(3)

The statistical analysis of compositional data is of fundamental importance to practitioners in generaland to chemists in particular.The existing methodology is principally due to Aitchison,who effectivelyuses two transformations,a ratio followed by the logarithmic,to create a useful,coherent theory thatin principle allows the plethora of normal-based multivariate techniques to be used on the transformeddata.This paper suggests that the well-known class of Box-Cox transformations can be employed inplace of the logarithmic to significantly improve the existing methodology.This is supported in part byshowing that one of the most basic problems that Aitchison managed to overcome,namely thespecification of an interpretable covariance structure for compositional data,can be resolved,or nearlyresolved,once the ratio transformation has been applied.Hence the resolution is not directly dependenton the logarithmic transformation.It is then verified that access to the general Box-Cox family will allowa more accurate use of the normal-based multivariate techniques,simply because better fits to normalitycan be achieved.Finally,maximum likelihood estimation and some associated asymptotics are employedto construct confidence intervals for ratios of the true,unknown compositional constituents.Heretoforethis had not been done even in the context of the logarithmic transformation.Applications to real dataare presented.  相似文献   

Quantitative evaluation of the depth of the western Mediterranean before, during and after the Late Miocene salinity crisis     

WILLIAM B.F. RYAN 《Sedimentology》1976,23(6):791-813

Quantitative geophysical calculations which take into consideration the isostatic loading of sediment overburden, the overlying water cover, and the thermal cooling history of the continental edge, and its adjacent oceanic lithosphere, demonstrate the foundering of the margins of the western Mediterranean had already commenced in the Aquitanian stage of the early Miocene. The calculations are based on magnitudes and rates of sediment accumulation observed along a profile of three commercial boreholes into the subsurface of the continental shelf of southern France. By the time of the late Miocene (Messinian) salinity crisis, the depth of the seafloor within the Balearic basin exceeded 2.5 km. Sea-level fluctuations induced by evaporitic draw-down permitted the exposure of large tracts of the former submerged continental margins to subaerial processes. The measured magnitude of sediment removal by erosion and channel incision near the outer shelf of the modern Gulf of Lion surpasses 1 km. The subsidence history of this shelf platform south of France provides new evidence that the continental lithosphere behaves as if it is rigidly coupled to its oceanic counterpart commencing with the initial phase of the pull-apart. No major vertical fault displacements have subsequently offset their overlying crustal layers. The sedimentary shaping and construction of the margin seaward of the Rhône delta resulted in a pronounced shelf edge migration and slope progradation during the pre-salinity crisis Miocene. It has taken 5 million years of predominant upbuilding to establish a new equilibrium profile similar in cross-section to the precrisis depositional surfaces created by outbuilding.  相似文献   

A geographical perspective on poverty–environment interactions     

LESLIE C GRAY  WILLIAM G MOSELEY† 《The Geographical journal》2005,171(1):9-23

This paper examines prevailing wisdoms on the topic of poverty–environmental interactions, problematizes some standard assumptions and interrogates the geographical literature on the subject. Dominant development discourse has tended to blame the poor for environmental degradation, ignoring the role of other processes and actors at various scales in causing environmental degradation. We examine how definitions of poverty, institutional arrangements, conventional economic models and assumed feedback loops may influence our understanding of poverty–environment interactions. The article gives particular attention to the political ecology approach as a lens through which this dynamic may be understood. Recent work in political ecology has broadened views of poverty–environment interactions by focusing on issues of power, scale and discourse in influencing outcomes and policies.  相似文献   

Annual time-series of total filterable atmospheric mercury concentrations in the Arctic   总被引：1，自引：0，他引：1  

JULIA Y. LU  WILLIAM H. SCHROEDER 《Tellus. Series B, Chemical and physical meteorology》2004,56(3):213-222

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The Arctic: a sink for mercury   总被引：5，自引：0，他引：5  

PARISA A. ARIYA  ASHU P. DASTOOR  MARC AMYOT  WILLIAM H. SCHROEDER  LEONARD BARRIE  KURT ANLAUF  FARHAD RAOFIE  REW RYZHKOV  DIDIER DAVIGNON  JANICK LALONDE  ALEXANDRA STEFFEN 《Tellus. Series B, Chemical and physical meteorology》2004,56(5):397-403

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Chemical Diversity of the Ueno Basalts, Central Japan: Identification of Mantle and Crustal Contributions to Arc Basalts   总被引：2，自引：0，他引：2  

KIMURA  JUN-ICHI; MANTON  WILLIAM I.; SUN  CHIH-HSIEN; IIZUMI  SHIGERU; YOSHIDA  TAKEYOSHI; STERN  ROBERT J. 《Journal of Petrology》2002,43(10):1923-1946

The Ueno Basalts of central Japan comprise a monogenetic volcaniccone complex that was active between 2·76 and 1·34Ma. Basalts were erupted at more than 14 centers scattered overa region 40 km in diameter. Alkali basalt was erupted first,followed by sub-alkaline basalt. Quasi-concentric expansionof eruption centers coinciding with uplift and with decreasingalkalinity of the lavas suggests that Ueno magmatism originatedfrom a mantle diapir as it mushroomed at the base of the lithosphere.Depleted asthenospheric mantle (alkali basalt), enriched lithosphericmantle (sub-alkaline basalt), and crustal components are identifiedas chemical end-members in the petrogenesis of the Ueno Basalts.Incompatible trace element abundances indicate that the Uenoalkali basalts are typical within-plate basalts, whereas thesub-alkaline basalts show strong affinities with normal arclavas. Sr–Nd–Pb isotopic compositions indicate thatthe mantle source of the alkali basalts was more depleted thanthat of the sub-alkaline basalts. About 7% melting of asthenosphericmantle in the garnet-lherzolite stability field produced theprimitive alkali basalts and 12% melting of spinel lherzolitewithin the subcontinental lithosphere produced the primitivesub-alkaline basalts. Isotopic compositions and fluid mobile/immobileelement ratios broadly covary with SiO₂ contents in the sub-alkalinesuite, and increasing silica content is associated with strongerEMII (Enriched Mantle II) isotope affinities and fluid mobileelement abundances. A progressive AFC (assimilation–fractionalcrystallization) model assuming assimilation of a low-K silicicmelt reproduces the chemical variations observed in the sub-alkalinesuite. Melting of a flattening mantle diapir at the base ofthe lithosphere is the dominant cause of Ueno magmatism, accompaniedby the assimilation of older arc crust. KEY WORDS: arc basalt; crustal assimilation; mantle heterogeneity; Ueno Basalts  相似文献   

Authigenic pyrite and gypsum in South West African continental slope sediments   总被引：1，自引：0，他引：1  

WILLIAM G. SIESSER  JOHN ROGERS 《Sedimentology》1976,23(4):567-577

An unusual association of authigenic pyrite and authigenic gypsum has been found in silty clays recovered from the South West African continental slope. Nannofossil content suggests that the sediments are Upper Miocene-Lower Pliocene in age. Pyrite occurs as (1) granular masses, (2) ‘worm’tubes, (3) foraminiferal infillings, and (4) framboids. Gypsum occurs as euhedral single or twinned crystals of selenite. ‘Worm’tubes and foraminiferal infillings of pyrite are partially or completely enclosed in some gypsum crystals. Electron microprobe analyses show a relatively high concentration of manganese in both the granular masses and tubes. Present-day waters off this coast are dominated by the upwelling of cold, nutrient-enriched waters (the Benguela Current). These rich waters support an enormous population of plankton. Death and decomposition of these plankton consume oxygen, thereby creating a belt of anaerobic sediments close to shore. An Upper Miocene-Lower Pliocene regression (Dingle & Scrutton, 1974) lowered sea level and shifted an older analogue of this upwelling zone seaward, eventually establishing an anaerobic environment in places on the present continental slope. Anaerobic bacteria thrived in these conditions. They reduced SO₄ dissolved in sea water, initiating the formation of H₂S. The H₂S reacted with iron minerals present in the sediment to form FeS. Addition of elemental sulphur produced pyrite. This strongly reducing, low pH, environment became saturated with calcium obtained by the dissolution of planktonic calcareous organisms. Gypsum was precipitated once the product of the concentrations of dissolved calcium and SO₄ exceeded the gypsum solubility product.  相似文献