Fragmented Urban Spaces? Ethnic Residential Areas in New Zealand Cities, 1996     

RON JOHNSTON  MICHAEL POULSEN  JAMES FORREST 《New Zealand geographer》2002,58(2):30-44

Residential segregation of ethnic groups is a major feature of cities in multi‐cultural societies such as New Zealand's. Measuring the degree of segregation has been the focus of much attention over the last half century, but there are difficulties with comparative studies using most of the measures adopted. An alternative procedure which classifies residential areas according to a homogeneity‐heterogeneity continuum is applied here to 1996 census small‐scale data for each of New Zealand's 33 main urban areas, to identify the degree of segregation of various ethnic groups. It reports that most New Zealanders from all ethnic groups (defined by self‐identity) live in mixed rather than exclusive residential areas. The main ethnic enclaves/ghettos are occupied by Maori and Pacific Islanders, and are entirely concentrated in the North Island, especially in urban areas which have substantial Polynesian populations.  相似文献   

Mesoproterozoic deep-water reefs from Borden Peninsula, Arctic Canada     

GUY M. NARBONNE  NOEL P. JAMES 《Sedimentology》1996,43(5):827-848

A superbly exposed stromatolite reef complex occurs in the Victor Bay Formation near Strathcona River on northern Baffin Island. Individual reefs are up to 130 m thick and nearly 1 km in length, and their development was clearly related to their position in the facies spectrum and to sea-level dynamics. In the first sea-level cycle, metre-scale reefs grew amongst mid-ramp calcarenites and outer-ramp shales during slow sea-level rise; a 25-m-thick oblate reef tract, separating mid-ramp and outer-ramp facies, formed during the highstand. The greatest period of reef growth was during the second sea-level cycle. Pinnacle reefs nucleated on the karsted upper surface of the oblate reef tract and aggraded rapidly in response to rising sea-level, producing structures with more than 75 m of depositional relief. A gradual symmetrical succession of stromatolite growth forms, from stratiform to cylindrical columns to conical columns and then back through cylindrical columns to stratiform, is mirrored by evidence in offreef deposits for deepening to a maximum flooding surface and then shallowing. The tops of these high-standing reefs were karsted during the following regression, while dolomite ‘cryptodomes’ grew as sheets on their submerged flanks and as progradational tongues extending basinward of the reefs. Continued sea-level fall resulted in subaerial exposure of the entire reef complex and the extensive formation of surface and subsurface karst. These Proterozoic slope buildups are similar to Phanerozoic deep-water reefs in size, shape, prevalence of synsedimentary lithification, presence of Neptunian dykes and in their well-developed vertical zonation of reefbuilders. However, they differ in being constructed exclusively by stromatolites rather than being mud mounds with small skeletal elements, and in lacking halos of perireefal sand- and gravel-sized calcareous debris. Their responses to changes in sea-level were strikingly similar to those shown by their younger counterparts, and suggest that sequence-stratigraphic concepts derived from studies of Phanerozoic reefs can also be applied to the Proterozoic.  相似文献   

MOROCCAN CERAMICS AND THE GEOGRAPHY OF INVENTED TRADITIONS*     

JAMES E. HOUSEFIELD 《Geographical review》1997,87(3):401-407

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Dehydration-melting of Biotite Gneiss and Quartz Amphibolite from 3 to 15 kbar   总被引：80，自引：20，他引：60  

PATIO DOUCE  ALBERTO E.; BEARD  JAMES S. 《Journal of Petrology》1995,36(3):707-738

We performed vapor-absent melting and crystallization experimentson two bulk compositions that model metamorphic rocks containinga single hydrous phase: a biotite gneiss [37% bio (mg-number55), 34% qtz, 27% plg (An₃₈), 2% ilm] and a quartz amphibolite[54% hbl (mg-number 60), 24% qtz, 20% plg (An₃₈), 2% ilm]. Experimentswere performed at 3 and 5 kbar in internally heated pressurevessels (IHPV), and at 7, 10, 125 and 15 kbar in piston cylinderapparatus (PC), from the vapor-absent solidi to (at least) thetemperature at which the hydrous mineral disappeared. Dehydration-meltingbegins at similar temperatures in both bulk compositions, rangingfrom T850C at P = 3 kbar T930C at P = 15 kbar. The hydrousmineral disappears 50C above the solidus in both systems, exceptin IHPV experiments at f(O₂) above Ni–NiO, in which biotitestability extends up to atleast 80C above the solidus. At theT at which the hydrous minerals disappear the biotite gneissproduces 2–3 times more melt than the quartz amphibolite(50–60 wt% vs 20–30 wt%). In both systems, variationsin melt productivity with P are controlled by three competingfactors: (1) the positive d P/dT slopes of the solidi, (2) decreasingH₂O activity with increasing P at constant H₂O content, and(3) Na₂O activity, which increases with P concomitantly withbreakdown of plagioclase. Melt productivities at T = 920–950Care maximized at intermediate pressures (7 kbar). The biotitegneiss produces strongly peraluminous granitic melts (SiO₂>70wt%) and residual assemblages of quartz norite (P>125 kbar)or garnet pyroxenite (P>125 kbar). The quartz amphiboliteproduces strongly peraluminous granodioritic melts (SiO₂>70wt%) that coexist with clinopyroxene + orthopyroxene + plagioclase+ quartz at P>10 kbar)garnet. The results of coupled meltingand crystallization experiments on the quartz amphibolite suggestthat strongly peraluminous granitoid rocks (e.g. cordierite-bearingand two-mica granites) can be derived from melting of Al-poorprotoliths. KEY WORDS: dehydration-melting; biotite gneiss; amphibolite; felsic magmas ^*Corresponding author  相似文献   

The Petrogenesis of Pliocene Alkaline Volcanic Rocks from the Pannonian Basin, Eastern Central Europe   总被引：12，自引：2，他引：10  

EMBEY-ISZTIN  A.; DOWNES  H.; JAMES  D. E.; UPTON  B. G. J.; DOBOSI  G.; INGRAM  G. A.; HARMON  R. S.; SCHARBERT  H. G. 《Journal of Petrology》1993,34(2):317-343

Late Tertiary post-orogenic alkaline basalts erupted in theextensional Pannonian Basin following Eocene-Miocene subductionand its related calc-alkaline volcanism. The alkaline volcaniccentres, dated between 11•7 and 1•4 Ma, are concentratedin several regions of the Pannonian Basin. Some are near thewestern (Graz Basin, Burgenland), northern (Ngrd), and eastern(Transylvania) margins of the basin, but the majority are concentratednear the Central Range (Balaton area and Little Hungarian Plain).Fresh samples from 31 volcanic centres of the extension-relatedlavas range from slightly hy-normative transitional basaltsthrough alkali basalts and basanites to olivine nephelinites.No highly evolved compositions have been encountered. The presenceof peridotite xenoliths, mantle xenocrysts, and high-pressuremegacrysts, even in the slightly more evolved rocks, indicatesthat differentiation took place within the upper mantle. Rare earth elements (REE) and ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ¹⁸O, D,and Pb isotopic ratios have been determined on a subset of samples,and also on clinopyroxene and amphibole megacrysts. Sr and Ndisotope ratios span the range of Neogene alkali basalts fromwestern and central Europe, and suggest that the magmas of thePannonian Basin were dominantly derived from asthenosphericpartial melting, but Pb isotopes indicate that in most casesthey were modified by melt components from the enriched lithosphericmantle through which they have ascended. ¹⁸O values indicatethat the magmas have not been significantly contaminated withcrustal material during ascent, and isotopic and trace-elementratios therefore reflect mantle source characteristics. Incompatible-elementpatterns show that the basic lavas erupted in the Balaton areaand Little Hungarian Plain are relatively homogeneous and areenriched in K, Rb, Ba, Sr, and Pb with respect to average oceanisland basalt, and resemble alkali basalts of Gough Island.In addition, ²⁰⁷Pb/²⁰⁴Pb is enriched relative to ^2O6Pb/²⁰⁴Pb.In these respects, the lavas of the Balaton area and the LittleHungarian Plain differ from those of other regions of Neogenealkaline magmatism of Europe. This may be due to the introductionof marine sediments into the mantle during the earlier periodof subduction and metasomatism of the lithosphere by slab-derivedfluids rich in K, Rb, Ba, Pb, and Sr. Lavas erupted in the peripheralareas have incompatible-element patterns and isotopic characteristicsdifferent from those of the central areas of the basin, andmore closely resemble Neogene alkaline lavas from areas of westernEurope where recent subduction has not occurred.  相似文献   

Rare Earth Element Inversion for Melt Distribution: Sensitivity and Application   总被引：1，自引：1，他引：0  

BRODIE  JAMES; LATIN  DAVE; WHITE  NICKY 《Journal of Petrology》1994,35(4):1155-1174

Inversion of rare earth element (REE) abundances in MgO-rich(MgO 6 wt.%) igneous rocks, described initially by McKenzie& O'Nions (1991), provides a useful means of constrainingthe distribution of melt fraction with depth, X(z), in the mantle.Here, we investigate the sensitivity of the REE inversion procedureto noise in measured REE abundances and to variation in parameterswhich must be specified a priori. Inverted melt distributionsare insensitive to realistic amounts of random noise but aresensitive to systematic noise. Melt distributions are also sensitiveto input parameters such as depth and range of melting, sourcecomposition, and mantle mineralogy. To determine unique meltdistributions, additional independent constraints on at leasttwo of the following input parameters are therefore required:depth and range of melting (i.e., lithospheric thickness); sourcecomposition; source mineralogy (dependent on mantle temperature).The successful replication of melt compositions where thesethree parameters are well constrained and the agreement betweeninverted melt distributions and melt distributions calculatedindependently assuming isentropic melting during adiabatic upwellingindicate that the scheme is reliable. REE inversion thereforeprovides a means for both routinely constraining X(z) and fordetermining unknown input parameters.  相似文献   

SOIL PROCESSES AND DEVELOPMENT RATES IN THE QUARTERMAIN MOUNTAINS, UPPER TAYLOR GLACIER REGION, ANTARCTICA     

JAMES BOCKHEIM 《Geografiska Annaler: Series A, Physical Geography》2007,89(3):153-165

Soil‐forming processes and soil development rates are compared and contrasted on glacial deposits in two adjacent and coeval valleys of the Quartermain Mountains, which are important because they display Miocene glacial Stratigraphy and some of the oldest landforms in the McMurdo Dry Valleys. More than 100 soil profiles were examined on seven drift sheets ranging from 115 000 to greater than 11.3 million years in age in Beacon Valley and Arena Valley. Although the two valleys contain drifts of similar age, they differ markedly in ice content of the substrate. Whereas Arena Valley generally has ‘dry‐frozen’ permafrost in the upper 1 m and minimal patterned ground, Beacon Valley contains massive ice buried by glacial drift and ice cored rock glaciers and has ice‐cemented perma‐frost in the upper 1 m and considerable associated patterned ground. Arena Valley soils have twice the rate of profile salt accumulation than Beacon Valley soils, because of lower available soil water and minimal cryoturbation. The following soil properties increase with age in both valleys: weathering stage, morphogenetic salt stage, thickness of the salt pan, the quantity of profile salts, electrical conductivity of the horizon of maximum salt enrichment, and depth of staining. Whereas soils less than 200 000 years and older soils derived from sandstone‐rich ground moraine are Typic Anhyorthels and Anhyturbels, soils of early Quaternary and older age, particularly on dolerite‐rich drifts, are Petronitric Anhyorthels. Arena Valley has the highest pedodiversity recorded in the McMurdo Dry Valleys. The soils of the Quartermain Mountains are the only soils in the McMurdo Dry Valleys known to contain abundant nitrates.  相似文献   

Kilauea East Rift Zone Magmatism: an Episode 54 Perspective   总被引：1，自引：0，他引：1  

THORNBER  CARL R.; HELIKER  CHRISTINA; SHERROD  DAVID R.; KAUAHIKAUA  JAMES P.; MIKLIUS  ASTA; OKUBO  PAUL G.; TRUSDELL  FRANK A.; BUDAHN  JAMES R.; RIDLEY  W. IAN; MEEKER  GREGORY P. 《Journal of Petrology》2003,44(9):1525-1559

On January 29–30, 1997, prolonged steady-state effusionof lava from Pu'u'O'o was briefly disrupted by shallow extensionbeneath Napau Crater, 1–4 km uprift of the active Kilaueavent. A 23-h-long eruption (episode 54) ensued from fissuresthat were overlapping or en echelon with eruptive fissures formedduring episode 1 in 1983 and those of earlier rift zone eruptionsin 1963 and 1968. Combined geophysical and petrologic data forthe 1994–1999 eruptive interval, including episode 54,reveal a variety of shallow magmatic conditions that persistin association with prolonged rift zone eruption. Near-ventlava samples document a significant range in composition, temperatureand crystallinity of pre-eruptive magma. As supported by phenocryst–liquidrelations and Kilauea mineral thermometers established herein,the rift zone extension that led to episode 54 resulted in mixtureof near-cotectic magma with discrete magma bodies cooled to  相似文献   

A CRY FOR HELP: KANSASFREELAND.COM     

JAMES R. SHORTRIDGE 《Geographical review》2004,94(4):530-540

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Halford Mackinder and the 'geographical pivot of history': a centennial retrospective     

KLAUS DODDS  JAMES D SIDAWAY† 《The Geographical journal》2004,170(4):292-297

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