Phonolitic Diatremes within the Dunedin Volcano, South Island, New Zealand   总被引：2，自引：2，他引：2  

PRICE  RICHARD C.; COOPER  ALAN F.; WOODHEAD  JON D.; CARTWRIGHT  IAN 《Journal of Petrology》2003,44(11):2053-2080

The Port Chalmers Breccia is a vent-filling, clastic volcanicunit exposed within the Miocene Dunedin Volcano of South Island,New Zealand. Clasts (up to in excess of 1 m but generally <20cm) are supported in ash and fine lapilli of phonolitic (ne-benmoreiteor tephro-phonolite) composition and the dominant clast type(55 to almost 100%) is also phonolitic. Less abundant lithologiesinclude ne-normative basalt (basanite), hawaiite, mugeariteand trachyandesite, syenites and microsyenites, coarse-grainedmafic (gabbros) and ultramafic rocks (pyroxenites, hornblendites),schists and sediments. The breccias were emplaced as diatremesassociated with localized, but highly explosive, eruptive eventsin which mantle-derived CO₂ was an important component. Thesyenitic and ultramafic clasts could represent intrusive suitesproduced by crystal fractionation acting on parental ne-benmoreitemagmas that may themselves have been derived by crystal fractionationfrom basanitic precursors. An alternative variation on thismodel is that the parental ne-benmoreites were generated throughpartial melting of an alkalic igneous underplate. Sr, Nd andPb isotopic compositions are strikingly similar to those ofintraplate igneous rocks, ranging in age from 100 to less than10 Ma, from elsewhere in the South Island, and New Zealand'ssub-Antarctic islands, the south Tasman Sea and the Ross Searegion. This regional, HIMU-influenced, isotopic signature isbelieved to be derived from within the lithospheric mantle. KEY WORDS: phonolite; diatreme; nepheline syenite; Dunedin Volcano; alkalic rocks; fractional crystallization  相似文献   

Spatial distribution of carbon sources and sinks in Canada's forests   总被引：7，自引：0，他引：7  

JING M. CHEN  WEIMIN JU  JOSEF CIHLAR  DAVID PRICE  JANE LIU  WENJUN CHEN  JIANJUN PAN  Y BLACK  ALAN BARR 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):622-641

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What status for the Quaternary?   总被引：3，自引：0，他引：3  

PHILIP L. GIBBARD  ALAN G. SMITH  JAN A. ZALASIEWICZ  TIFFANY L. BARRY  DAVID CANTRILL  ANGELA L. COE  JOHN C. W. COPE  REW S. GALE  F. JOHN GREGORY  JOHN H. POWELL  PETER F. RAWSON  PHILIP STONE  COLIN N. WATERS 《Boreas: An International Journal of Quaternary Research》2005,34(1):1-6

The status of the Quaternary, long regarded as a geological period effectively coincident with the main climatic deterioration of the current Ice Age, has recently been questioned as a formal stratigraphic unit. We argue here that it should be retained as a formal period of geological time. Furthermore, we consider that its beginning should be placed at the Gauss-Matuyama magnetic chron boundary at about 2.6 Ma, rather than at its current position at about 1.8 Ma. The Quaternary would be formally subdivided into the Pleistocene and Holocene epochs. The global chronostratigraphical correlation table proposed is enclosed at the back of this issue.  相似文献   

Noble Metal Concentrations in Shoshonitic Lamprophyres: Analysis of the Weekend Dykes, Eastern Shore, Nova Scotia, Canada   总被引：2，自引：0，他引：2  

GREENOUGH  JOHN D.; OWEN  J. VICTOR; RUFFMAN  ALAN 《Journal of Petrology》1993,34(6):1247-1269

Devonian, spessartite dykes, known as the Weekend dykes, onthe Eastern Shore of Nova Scotia contain panidiomorphic texturesand mineral (amphibole, clinopyroxene, and biotite) compositionstypical of shoshonitic lamprophyres. The major element and traceelement geochemistry of the Weekend dykes is also representativeof shoshonitic lamprophyres with high large ion lithophile elementconcentrations (LILE, e.g., Rb, K, and Ba) relative to the lightrare earth elements (LREE, e.g., La) and very low Nb and Ti.Only Ta concentrations are uncharacteristically high relativeto Nb and Ti. The dykes are variably evolved but many samplesshow primitive compositions with high mgnumber [>0.70, wheremg-number=Mg/(Mg+09total Fe) atomic] high MgO and Ni concentrations(>10 wt.% and 150 ppm, respectively), and low heavy REE concentrations.All noble metal concentrations (Au, Pd, Pt, Rh, Ru, and Ir)tend to be lower in evolved samples than in primitive rocks,suggesting that evolved magmas were efficiently scavenged byimmiscible sulphide globules and that shoshonitic lamprophyreplutons may hold economic promise for the platinum-group elements(PGE). Noble metal abundances in even the most primitive rocksare low compared with many basaltic rocks excepting mid-oceanridge basalt (MORB). This makes doubtful the idea that Megumagroup mesothermal gold deposits, which are spatially and temporallyassociated with the dykes, derived their gold from the lamprophyres.Models that explain PGE concentrations and Pd/Ir ratios in awide variety of mafic rocks suggest that the low noble metalabundances probably reflect metal retention in mantle sulphides,olivine, and PGE alloys at low percentages of melting. However,noble metal abundances are higher than expected if the oceanicslab was involved in the melting process or if the source regionresembled that for most MORB, which appears to have low PGE.Mantle metasomatism represents an unlikely explanation for thePGE abundances, which are equivalent to those expected in alkalinehot-spot magmas. The high PGE abundances of hot-spot magmas(compared with MORB) may be related to the incorporation ofcore materials in deep mantle plumes. Presumably the hot-spotlikemantle became part of the subcontinental lithospheric mantlebefore the subduction and transpressional event that producedthe shoshonitic magmas.  相似文献   

Hydrological effects on carbon cycles of Canada's forests and wetlands   总被引：1，自引：0，他引：1  

WEIMIN JU  JING M. CHEN  T. ANDREW BLACK  ALAN G. BARR  HARRY MCCAUGHEY  NIGEL T. ROULET 《Tellus. Series B, Chemical and physical meteorology》2006,58(1):16-30

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GEOMORPHOLOGICAL CHARACTERISTICS AND SIGNIFICANCE OF LATE QUATERNARY PARAGLACIAL ROCK-SLOPE FAILURES ON SKIDDAW GROUP TERRAIN, LAKE DISTRICT, NORTHWEST ENGLAND     

PETER WILSON  ALAN SMITH 《Geografiska Annaler: Series A, Physical Geography》2006,88(3):237-252

ABSTRACT. Eight relict rock-slope failures (RSFs) on Skiddaw Group terrain in the Lake District, northwest England, are described. Five of the failures are rockslides, one is a product of slope deformation, and two are compound features with evidence for sliding and deformation in different sectors. As none appears to have been overrun and modified by glacier ice it is concluded that they all post-date the Last Glacial Maximum (LGM ; c. 21 ± 3 cal. ka bp ). Slope stress readjustments resulting from glacial and deglacial influences are considered to have weakened the slopes, and application of the term paraglacial is appropriate. Permafrost aggradation and degradation, seismic activity and fluvial erosion are among processes that may have contributed to failure at certain sites. The failures are significant as potential debris sources during future ice advances, contributing to valley widening and cirque enlargement and, possibly, for acting as sites of cirque initiation. Previously, Skiddaw Group rocks have been regarded as homogeneous and of limited resistance to the weathering and erosion associated with Quaternary glacial, periglacial and fluvial processes. These characteristics and processes have been used to explain the steep smooth slopes and rounded hills that dominate Skiddaw Group terrain. Rock-slope failure has also helped shape this terrain and should be incorporated in future interpretations of landscape development.  相似文献   

Botryoidal aragonite and its diagenesis     

ALAN C. KENDALL 《Sedimentology》1986,33(3):441-443

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Stomatal and non-stomatal fluxes of ozone to a northern mixed hardwood forest   总被引：2，自引：0，他引：2  

ALAN HOGG  JOHAN UDDLING  DAVID ELLSWORTH  MARY ANNE CARROLL  SHELLEY PRESSLEY  BRIAN LAMB  CHRISTOPH VOGEL 《Tellus. Series B, Chemical and physical meteorology》2007,59(3):514-525

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Book Review: TRIBOLITE SYSTEMATICS,BIOSTRATIGRAPHY AND PALAEOECOLOGY OF THE LOWER ORDOVICIAN KOMSTAD LIMESTONE AND HUK FORMATIONS,SOUTHERN SCANDINAVIA by Anne Thorshøj Nielsen. Fossils and Strata No. 38, Scandinavian University Press, 1994. 374 pp. $74.00. ISBN 82 00 37658 3     

ALAN W. OWEN 《Geological Journal》1997,32(2):195-195

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Constructing knowledge from multivariate spatiotemporal data: integrating geographical visualization with knowledge discovery in database methods     

ALAN M. MACEACHREN  MONICA WACHOWICZ  ROBERT EDSALL  DANIEL HAUG  RAYMON MASTERS 《International journal of geographical information science》2013,27(4):311-334

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