Petrological and Geochemical Evidence for Granitoid Formation: The Waldoboro Pluton Complex, Maine     

BARTON  MICHAEL; SIDLE  WILLIAM C. 《Journal of Petrology》1994,35(5):1241-1274

The Acadian-age Waldoboro Pluton Complex (WPC), mid-coastalMaine, consists of seven granitoid units surrounded by migmatitic,peraluminous gneisses and schists (predominantly Bucksport orSebascodegan Formation). The complex (area >340 km²) cross-cutsthe westward-vergent St. George thrust fault, which may markthe boundary between the Avalon and Gander composite terranes.Field and petrologic data indicate in situ formation of theperaluminous, syntectonic granitoids: contacts with Bucksportparagneisses are transitional and concordant; abundant country-rockenclaves show evidence for melting; restitic garnet, biotite,and plagioclase in the granitoids are identical in compositionto garnet, biotite, and plagioclase in the country rock. Chemicalvariations among the main granitoid phases (gneissic granite,granite, and leucogranite) reflect varying degrees of melt-restiteunmixing. Major and trace elements define mixing trends betweenrefractory Bucksport lithologies and leucogranites which approximatemelt compositions. Petrographic and whole-rock chemical dataare consistent with restitic plagioclase, garnet, biotite, tourmaline,zircon, apatite, sphene, and an accessory phase such as monazite.Quantitative major-oxide mass-balance models indicate that gneissicgranite represents a mixture of 55% melt–45% restite whereasgranite represents a mixture of 76% melt–24% restite.Melt-restite proportions calculated from trace element dataagree with those calculated from major oxide data for the gneissicgranite, but are different (85% melt–15% restite) fromthose calculated from major oxide data for the granite. Thisis attributed to inhomogeneous distribution of minor phasesand the effects of metasomatism. High K₂O, Rb, Ba, Cs, Li, B,K/Rb, K/Ba, Rb/Sr, and Th/U along the eastern mylonitic marginand elsewhere within the WPC reflect post-solidification metasomaticprocesses. Intrusion of mafic magmas during uplift after crustal thickeningappears to have caused high-temperature metamorphism and anatexisof Bucksport country rocks at relatively low pressure (0.4 GPa).Dehydration melting of muscovite to produce magmas saturatedor nearly saturated with H₂O explains the formation of migmatitesin the vicinity of the WPC. Formation of granites by 50–60%fluid-absent melting of Bucksport source rocks containing 20%biotite requires that fusion occurred at T860C and consumedall of the biotite in the source rock. Phase equilibrium dataand estimated temperatures of formation provide evidence thatthe granitoids formed at T<860C, whereas petrographic dataindicate that not all biotite in the source rock was consumedduring anatexis. Therefore, the WPC granitoids could have formedby fluid-absent melting if the source rocks contained >20%biotite (the maximum amount observed). However, it is also possiblethat influx of aqueous fluid before or during anatexis allowedproduction of relatively large volumes of melt at T<860C.Available data do not allow these possibilities to be rigorouslytested. The WPC granitoids have many characteristics of S-type granitesand preserve a chemical and mineralogical record of their sourcerocks, indicating that granites can image their sources evenin tectonically complex regions.  相似文献   

Unravelling the conundrum of river response to rising sea‐level from laboratory to field. Part I: Laboratory experiments     

GARY PARKER  TETSUJI MUTO  YOSHIHISA AKAMATSU  WILLIAM E. DIETRICH  J. WESLEY LAUER 《Sedimentology》2008,55(6):1643-1655

The most recent deglaciation resulted in a global sea‐level rise of some 120 m over approximately 12 000 years. In this Part I of two parts, a moving boundary numerical model is developed to predict the response of rivers to this rise. The model was motivated by experiments at small scale, which have identified two modes describing the transgression of a river mouth: autoretreat without abandonment of the river delta (no sediment starvation at the topset–foreset break) and sediment‐starved autoretreat with abandonment of the delta. In the latter case, transgression is far more rapid and its effects are felt much further upstream of the river mouth. The moving boundary numerical model is checked against experiments. The generally favourable results of the check motivate adaptation of the model to describe the response of the much larger Fly‐Strickland River system, Papua New Guinea to Holocene sea‐level rise; this is done in the companion paper, Part II.  相似文献   

Source,timing, frequency and flux of ice‐rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis     

ANNA I. HAAPANIEMI  JAMES D. SCOURSE  VICTORIA L. PECK  HILARY KENNEDY  PAUL KENNEDY  SIDNEY R. HEMMING  MARK F. A. FURZE  ANNA J. PIEŃKOWSKI  WILLIAM E. N. AUSTIN  JOHN WALDEN  EMILIE WADSWORTH  IAN R. HALL 《Boreas: An International Journal of Quaternary Research》2010,39(3):576-591

Haapaniemi, A.I., Scourse, J.D., Peck, V.L., Kennedy, H., Kennedy, P., Hemming, S.R., Furze, M.F.A., Pieńkowski, A.J., Austin, W.E.N., Walden, J., Wadsworth, E. & Hall, I.R. 2010: Source, timing, frequency and flux of ice‐rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis. Boreas, Vol. 39, pp. 576–591. 10.1111/j.1502‐3885.2010.00141.x. ISSN 0300‐9483. Increased fluxes of ice‐rafted detritus (IRD) from European ice sheets have been documented some 1000–1500 years before the arrival of Laurentide Ice Sheet (LIS)‐sourced IRD during Heinrich (H) events. These early fluxes have become known as ‘precursor events’, and it has been suggested that they have mechanistic significance in the propagation of H events. Here we present a re‐analysis of one of the main cores used to generate the precursor concept, OMEX‐2K from the Goban Spur covering the last 30 ka, in order to identify whether the British–Irish Ice Sheet (BIIS) IRD fluxes occur only as precursors before H layers. IRD characterization and planktonic foraminiferal δ¹⁸O measurements constrained by a new age model have enabled the generation of a continuous record of IRD sources, timing, frequency and flux, and of local contemporary hydrographic conditions. The evidence indicates that BIIS IRD precursors are not uniquely, or mechanistically, linked to H events, but are part of the pervasive millennial‐scale cyclicity. Our results support an LIS source for the IRD comprising H layers, but the ambient glacial sections are dominated by assemblages typical of the Irish Sea Ice Stream. Light isotope excursions associated with H events are interpreted as resulting from the melting of the BIIS, with ice‐sheet destabilization attributed to eustatic jumps generated by LIS discharge during H events. This positive‐feedback mechanism probably caused similar responses in all circum‐Atlantic ice‐sheet margins, and the resulting gross freshwater flux contributed to the perturbation of the Atlantic Meridional Overturning Circulation during H events.  相似文献   

On determining initial conditions and parameters in a simple coupled atmosphere-ocean model by adjoint data assimilation     

JINGXI LU  WILLIAM W. HSIEH 《地球，A辑:动力气象学与海洋学》1998,50(4):534-544

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Facies and stacking patterns of shelf-deltas within the Palaeogene Battfjellet Formation, Nordenskiöld Land, Svalbard: implications for subsurface reservoir prediction     

WILLIAM HELLAND-HANSEN  Associate Editor: Mariano Marzo 《Sedimentology》2010,57(1):190-208

Textural and mineralogical properties of the sediment, facies characteristics (both derived from well data), stacking patterns (derived from well and seismic data) and plan‐view shapes (derived from seismic data) are all essential components when reconstructing reservoir geometries from subsurface data sets. Without the availability of all these sources of information, reservoir predictions can potentially deviate significantly from the true geometries. In particular, inferences about internal sandbody geometry from plan‐view considerations (isopach maps and seismic attribute maps) may lead to erroneous conclusions without knowledge of facies and textural properties of the sediment. Analysis of well‐exposed sedimentary systems has the potential to establish links between internal facies characteristics and large‐scale geometry and to improve models coupling information at these variable scales. The Palaeogene Battfjellet Formation, Svalbard, has been studied with the aim to unravel internal characteristics and external form by investigating sediment properties, facies and stacking patterns. The formation shows a combination of texturally and mineralogically very immature sediments, a predominance of wave‐generated or wave‐induced sedimentary structures and a stacking pattern of highly variable numbers of parasequences at localities few kilometres apart that best can be explained in terms of small shifting deltaic lobes that produced a complex pattern of overlapping sandbodies. The strong evidence of wave action in the receiving basin could in itself indicate strike‐extensive sandstone bodies; however, the complex sandbody arrangement and the immaturity of the sediments preclude such an interpretation. Traditional facies models coupling plan‐view geometries with internal facies characteristics (such as the coupling of strike extensive barrier systems with wave‐dominated sedimentary structures or the coupling of elongated fluvial‐dominated deltas with offshore‐directed current‐generated structures) are much too simple and may lead to erroneous interpretations if the complexity revealed by all sources of data is not appreciated.  相似文献   

Carbon taxes,cap-and-trade administration,and US legislation     

WILLIAM WHITESELL 《Climate Policy》2013,13(5):457-462

An upstream cap-and-trade system that rations allowances for the carbon content of fuel inputs could achieve wider coverage than existing CO₂ emission programmes or most of those proposed in draft US legislation, but would risk shortages and price spikes. Allowance price volatility could be avoided with a CO₂-price corridor established through auctions, similar in some respects to how central banks manage short-term interest rates with open market operations. Building on the central bank analogy, a Greenhouse Gas Board could be established with the ‘instrument independence’ to set annual CO₂-price corridors in line with broadly-framed, long-term climate goals laid out in legislation. National and regional Boards of this nature might also help facilitate the international coordination of climate policies.  相似文献   

THE “PRISTINE MYTH” REVISITED     

WILLIAM M. DENEVAN 《Geographical review》2011,101(4):576-591

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Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology     

DAVID S. SCHIMEL  TIMOTHY G. F. KITTEL  WILLIAM J. PARTON 《地球，A辑:动力气象学与海洋学》1991,43(4):188-203

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JOHANNES HUMLUM ATLAS OF ECONOMIC GEOGRAPHY     

WILLIAM SMITH 《New Zealand geographer》1977,33(1):43-43

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Influence of epicentral distance on local seismic response in Kolkata City,India     

WILLIAM?K?MOHANTYEmail author  AKHILESH?K?VERMA  FRANCO?VACCARI  GIULIANO?F?PANZA 《Journal of Earth System Science》2013,122(2):321-338

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