Torngat ultramafic lamprophyres and their relation to the North Atlantic Alkaline Province   总被引：3，自引：0，他引：3  

Sebastian Tappe  George A. Jenner  Stephen F. Foley  Larry Heaman  Dean Besserer  Bruce A. Kjarsgaard  Bruce Ryan 《Lithos》2004,76(1-4):491-518

Geological mapping and diamond exploration in northern Quebec and Labrador has revealed an undeformed ultramafic dyke swarm in the northern Torngat Mountains. The dyke rocks are dominated by an olivine-phlogopite mineralogy and contain varying amounts of primary carbonate. Their mineralogy, mineral compositional trends and the presence of typomorphic minerals (e.g. kimzeyitic garnet), indicate that these dykes comprise an ultramafic lamprophyre suite grading into carbonatite. Recognized rock varieties are aillikite, mela-aillikite and subordinate carbonatite. Carbonatite and aillikite have in common high carbonate content and a lack of clinopyroxene. In contrast, mela-aillikites are richer in mafic silicate minerals, in particular clinopyroxene and amphibole, and contain only small amounts of primary carbonate. The modal mineralogy and textures of the dyke varieties are gradational, indicating that they represent end-members in a compositional continuum.

The Torngat ultramafic lamprophyres are characterized by high but variable MgO (10–25 wt.%), CaO (5–20 wt.%), TiO₂ (3–10 wt.%) and K₂O (1–4 wt.%), but low SiO₂ (22–37 wt.%) and Al₂O₃ (2–6 wt.%). Higher SiO₂, Al₂O₃, Na₂O and lower CO₂ content distinguish the mela-aillikites from the aillikites. Whereas the bulk rock major and trace element concentrations of the aillikites and mela-aillikites overlap, there is no fractional crystallization relation between them. The major and trace element characteristics imply related parental magmas, with minor olivine and Cr-spinel fractionation accounting for intra-group variation.

The Torngat ultramafic lamprophyres have a Neoproterozoic age and are spatially and compositionally closely related with the Neoproterozoic ultramafic lamprophyres from central West Greenland. Ultramafic potassic-to-carbonatitic magmatism occurred in both eastern Laurentia and western Baltica during the Late Neoproterozoic. It can be inferred from the emplacement ages of the alkaline complexes and timing of Late Proterozoic processes in the North Atlantic region that this volatile-rich, deep-seated igneous activity was a distal effect of the breakup of Rodinia. This occurred during and/or after the rift-to-drift transition that led to the opening of the Iapetus Ocean.  相似文献   

A new approach to estimate canopy evaporation and canopy interception capacity from evapotranspiration and sap flow measurements during and following wetting          下载免费PDF全文

J. Uddin  J. P. Foley  R. J. Smith  N. H. Hancock 《水文研究》2016,30(11):1757-1767

Canopy interception and its evaporation into the atmosphere during irrigation or a rainfall event are important in irrigation scheduling, but are challenging to estimate using conventional methods. This study introduces a new approach to estimate the canopy interception from measurements of actual total evapotranspiration (ET) using eddy covariance and estimation of the transpiration from measurements of sap flow. The measurements were conducted over a small‐scale sprinkler‐irrigated cotton field before, during and after sprinkler irrigation. Evaporation and sap flow dynamics during irrigation show that the total ET during irrigation increased significantly because of the evaporation of free intercepted water while transpiration was suppressed almost completely. The difference between actual ET and transpiration (sap flow) during and immediately following irrigation (post irrigation) represents the total canopy evaporation while the canopy interception capacity was calculated as the difference between actual ET and transpiration (sap flow) during drying (post irrigation) following cessation of the irrigation. The canopy evaporation of cotton canopy was calculated as 0.8 mm, and the interception capacity was estimated to be 0.31 mm of water. The measurement uncertainty in both the non‐dimensional ET and non‐dimensional sap flow was shown to be very low. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Insights into the petrogenesis of the West Kimberley lamproites from trace elements in olivine     

Jaques  A. Lynton  Foley  Stephen F. 《Mineralogy and Petrology》2018,112(2):519-537

The Miocene lamproites of the West Kimberley region, Western Australia include olivine-leucite lamproites (≤10 wt% MgO) containing olivine and leucite microphenocrysts, and diamondiferous olivine lamproites (20–30 wt% MgO) containing olivine phenocrysts and larger (1–10 mm) olivine as mantle xenocrysts and dunite micro-xenoliths. Olivine phenocrysts and thin (<100 μm) magmatic rims define trends of decreasing Cr and Ni, and increasing Ca and Mn, with decreasing olivine Mg#, consistent with fractional crystallisation of olivine (and minor chromite). Many phenocrysts are zoned, and those with cores of similar Mg# and trace element abundances to the mantle xenocrysts may be xenocrysts overgrown by later olivine crystallised from the lamproite magma. Magmatic olivines Mg#_91–92 are estimated to have been in equilibrium with olivine lamproite magma(s) containing ~22–24 wt% MgO. The xenocrystic mantle olivines Mg_90–92.5 in the olivine lamproites are inferred from trace element abundances to be mostly derived from garnet peridotite with equilibration temperatures estimated from the Al-in-olivine thermometer (Bussweiler et al. 2017) to be ~1000–1270 °C at depths of 115–190 km. Olivines from the deeper lithosphere are less depleted (lower Mg#, higher Na, Al, P, Ti, Zr etc) than those at shallower depths, a feature suggested to reflect the combined effects of metasomatic re-enrichment of the craton roots (Ti, Fe, Zr etc) and increasing temperature with depth of origin (Na, Al, Ca). The West Kimberley lamproite olivines are not enriched in Li, as might be expected if their source regions contained continental sedimentary material as has been previously inferred from lamproite large-ion-lithophile trace elements, and Sr and Pb isotopes.

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Marine protected areas—substantiating their worth     

H. Glenn  P. Wattage  S. Mardle  T. Van Rensburg  A. Grehan  N. Foley 《Marine Policy》2010

With the UK Marine Bill promoting the creation of a network of marine protected areas and similar commitments in other countries there is a need for tools to assist in their design and management. Although physical science often drives designation, the implementation of marine protected areas also encompasses political and socio-economic issues. This paper focuses on one tool in the armoury of decision-makers: choice experiments. It illustrates its application to the quantification of aspects of socio-economic value not readily incorporated into the evaluation of the costs and benefits of marine protected areas utilising cold-water deep coral reefs off the Republic of Ireland.  相似文献   

Planktonic dimethylsulfide and cloud albedo: An estimate of the feedback response     

Jonathan A. Foley  Karl E. Taylor  Steven J. Ghan 《Climatic change》1991,18(1):1-15

Partial control of climate by the biosphere may be possible through a chain of processes that ultimately links marine plankton production of dimethylsulfide (DMS) with changes in cloud albedo (Charlson et al., 1987). Changes in cloud optical properties can have profound impacts on atmospheric radiation transfer and, hence, the surface environment. In this study, we have developed a simple model that incorporates empirically based parameterizations to account for the biological control of cloud droplet concentration in a first attempt to estimate the strength of the DMS-cloud albedo feedback mechanism. We find that the feedback reduces the global climatic response to imposed perturbations in solar insolation by less than 7%. Likewise, it modifies the strength of other feedbacks affecting surface insolation over oceans by roughly the same amount. This suggests that the DMS-cloud albedo mechanism will be unable to substantially reduce climate sensitivity, although these results should be confirmed with less idealized models when more is known about the net production of DMS by the marine biosphere and its relation to aerosol/cloud microphysics and climate.  相似文献   

Use of high spectral resolution remote sensing to determine leaf palatability of eucalypt trees for folivorous marsupials     

Steve Dury  Brian Turner  Bill Foley  Ian Wallis 《International Journal of Applied Earth Observation and Geoinformation》2001,3(4):328

In this study we assess the feasibility of remotely measuring canopy biochemistry, and thus the potential for conducting large-scale mapping of habitat quality. A number of studies have found nutrient composition of eucalypt foliage to be a major determinant of the distribution of folivorous marsupials. More recently it has been demonstrated that a specific group of secondary plant chemicals, the diformylphloroglucinols (DFPs), are the most important feeding deterrents, and are thus vital determinants of habitat quality. We report on the use of laboratory spectroscopy to attempt to identify one such DFP, sideroxylonal-A, in the foliage of Eucalyptus melliodora, one of the few eucalypt species browsed by folivorous marsupials. Reflectance spectra were obtained for freeze-dried, ground leaves using near infrared spectroscopy (NIRS) and for both oven-dried and fresh whole leaves using a laboratory-based (FieldSpec) spectroradiometer. Modified partial least squares (MPLS) regression was used to develop calibration equations for sideroxylonal-A concentration based on the reflectance spectra transformed as both the first and second difference of absorbance (Log 1/R). The predictive ability of the calibration equations was assessed using the standard error of calibration statistic (SECV). Coefficients of determination (r²) were highest for the ground leaf spectra (0.98), followed by the fresh leaf and dry leaf spectra (0.94 and 0.87, respectively). When applied to independent validation sub-sets, sideroxylonal-A was most accurately predicted from the ground leaf spectra (r² = 0.94), followed by the dry leaf and fresh leaf spectra (0.72 and 0.53, respectively). Two spectral regions, centred on 674 nm and 1394 nm, were found to be highly correlated with sideroxylonal-A concentration for each of the three spectral data sets studied. Results from this study suggest that calibration equations derived from modified partial least squares regression may be used to predict sideroxylonal-A concentration, and hence leaf palatability, of Eucalyptus melliodora trees, thereby indicating that the remote estimation of habitat quality of eucalypt forests for marsupial folivores is feasible.  相似文献   

Global-Scale Relationships between Climate and the Dengue Fever Vector, Aedes Aegypti     

Marianne J. Hopp  Jonathan A. Foley 《Climatic change》2001,48(2-3):441-463

Considerable interest exists inthe potential role climate may play in human healthissues, especially regarding the effect of climatechange on vector-borne disease. The Aedesaegypti mosquito, the principal vector for dengue,considered the most important vector-borne viraldisease in the world, is particularly susceptible toclimate variability and climatic change. Here wepresent a modeling analysis focusing on global-scaleassociations between climate and the development,potential distribution, and population dynamics ofAe. aegypti. We evaluate the model by comparingand contrasting model data with observed mosquitodensities. There is good agreement between theobserved and modeled global distribution of themosquito; however, the model results suggest thepotential for increased latitudinal distributionsduring warmer months. Seasonal fluctuations inmosquito abundance also compare well to observed data. Discrepancies possibly reflect the relatively lowresolution of the climate data and model output andthe inability of the model to account for localmicroclimate effects, especially in coastal areas.Future modeling efforts will involve study ofinterannual variability in mosquito dynamics.  相似文献   

A meta-analysis of global crop water productivity of three leading world crops (wheat,corn, and rice) in the irrigated areas over three decades     

Daniel J. Foley  Itiya P. Aneece  Pardhasaradhi G. Teluguntla  Adam J. Oliphant 《International Journal of Digital Earth》2020,13(8):939-975

ABSTRACT

The overarching goal of this study was to perform a comprehensive meta-analysis of irrigated agricultural Crop Water Productivity (CWP) of the world’s three leading crops: wheat, corn, and rice based on three decades of remote sensing and non-remote sensing-based studies. Overall, CWP data from 148 crop growing study sites (60 wheat, 43 corn, and 45 rice) spread across the world were gathered from published articles spanning 31 different countries. There was overwhelming evidence of a significant increase in CWP with an increase in latitude for predominately northern hemisphere datasets. For example, corn grown in latitude 40–50° had much higher mean CWP (2.45?kg/m³) compared to mean CWP of corn grown in other latitudes such as 30–40° (1.67?kg/m³) or 20–30° (0.94?kg/m³). The same trend existed for wheat and rice as well. For soils, none of the CWP values, for any of the three crops, were statistically different. However, mean CWP in higher latitudes for the same soil was significantly higher than the mean CWP for the same soil in lower latitudes. This applied for all three crops studied. For wheat, the global CWP categories were low (≤0.75?kg/m³), medium (>0.75 to <1.10?kg/m³), and high CWP (≥1.10?kg/m³). For corn the global CWP categories were low (≤1.25?kg/m³), medium (>1.25 to ≤1.75?kg/m³), and high (>1.75?kg/m³). For rice the global CWP categories were low (≤0.70?kg/m³), medium (>0.70 to ≤1.25?kg/m³), and high (>1.25?kg/m³). USA and China are the only two countries that have consistently high CWP for wheat, corn, and rice. Australia and India have medium CWP for wheat and rice. India’s corn, however, has low CWP. Egypt, Turkey, Netherlands, Mexico, and Israel have high CWP for wheat. Romania, Argentina, and Hungary have high CWP for corn, and Philippines has high CWP for rice. All other countries have either low or medium CWP for all three crops. Based on data in this study, the highest consumers of water for crop production also have the most potential for water savings. These countries are USA, India, and China for wheat; USA, China, and Brazil for corn; India, China, and Pakistan for rice. For example, even just a 10% increase in CWP of wheat grown in India can save 6974 billion liters of water. This is equivalent to creating 6974 lakes each of 100?m³ in volume that leads to many benefits such as acting as ‘water banks’ for lean season, recreation, and numerous ecological services. This study establishes the volume of water that can be saved for each crop in each country when there is an increase in CWP by 10%, 20%, and 30%.  相似文献   

Sm-Nd and Rb-Sr isotopic systematics of the East Antarctic Manning Massif alkaline trachybasalts and the development of the mantle beneath the Lambert-Amery rift     

A. V. Andronikov  S. F. Foley  B. V. Beliatsky 《Mineralogy and Petrology》1998,63(3-4):243-261

Summary Rb-Sr and Sm-Nd isotopic investigations have been carried out on samples forming a sequence from the bottom to the top of a suite of K-rich olivine trachybasalts from the Manning Massif in the northern Prince Charles Mountains, East Antarctica. Several separate flows, each 3.5-6.5 m thick, occur as individual small outcrops and are related to the Lambert-Amery rift. Nd-Sr isotopic features of the volcanics are similar to those for lherzolite xenoliths from the Mesozoic alkaline ultramafic rocks of the adjacent Jetty Peninsula area, but the trace element abundances and patterns are consistent with the occurrence of minor phases such as apatite, amphibole, ilmenite and perovskite in the source region. According to Nd-Sr isotopic characteristics (¹⁴³Nd/¹⁴⁴Nd = 0.512026-0.512269;⁸⁷Sr/⁸⁶Sr = 0.707765-0.708046), the trachybasalts were generated from an enriched mantle source. These features are suggested here to result from isotopic mixing between peridotite wall-rocks similar to the Jetty Peninsula xenolith samples and melts derived from ultramafic veins in the lithosphere. A synthesis from isochron and model ages on volcanics and xenoliths indicates formation of the lithosphere at about 1.2 Ga, followed by two episodes of subsequent enrichment at 0.91.0 Ga and ca. 0.6 Ga. The¹⁴³Nd/¹⁴⁴Nd values for the volcanics show a wide range, but are more enriched for the bottom part of the suite, becoming more depleted towards the top. This may be explained by a steadily decreasing vein/wall-rock ratio from 35% to 10% due to progressive heating of the source region. This variation in ENd is not accompanied by a corresponding increase in⁸⁷Sr/⁸⁶Sr, which constrains both vein and wall-rock characteristics quite closely: the wall-rock was an enriched peridotite, whereas the vein assemblage comprised dominantly clinopyroxene and amphibole with a lesser, but essential, amount of phlogopite. REE-rich accessory phases such as apatite and perovskite were present in the vein, but were rare, so that the vein as a whole had high Sr/Nd. Rb-Sr age determination on Manning Massif bulk rocks gives an apparent isochron age of 40±1.2 Ma (I_Sr = 0.70762), although the age is probably falsified by the mixing processes during melting.

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Sm-Nd und Rb-Sr Isotopenuntersuchungen an alkalischen Trachybasalten des ostantarktischen Manning Massivs: Entwicklung des Mantels unter dem Lambert-Amery Rift

Zusammenfassung Sm-Nd- und Rb-Sr-Isotope wurden in einer Abfolge von K-reichen OlivinTrachybasalten im Manning Massiv in den nördlichen Prince Charles Mountains, Ost-Antarktis, untersucht. Proben wurden systematisch von mehreren sich überlagernden Lavaströmen genommen, die Mächtigkeiten von 3,5 bis 6,5 m erreichen und dem Lambert-Amery Rift zugeordnet werden. Nd-Sr Isotopenzusammensetzung der Vulkanite sind ähnlich wie in Iherzolithischen Mantelxenolithen aus alkalischen Ultramafiten der Jetty Halbinsel. Allerdings deuten die Spurenelementgehalte sowie die Spurenelementverteilungen auf die Anwesenheit von Apatit, Amphibol, Ilmenit und Perowskit in der Quellenregionhin. Nd-Sr Isotope der Trachybasalte (¹⁴³Nd/¹⁴⁴Nd= 0.512026–0.512269;⁸⁷Sr/⁸⁶Sr = 0.707765–0.708046) weisen auf eine angereicherte Mantelzusammensetzung hin. Für die hier gefundenen Werte wird ein Mischungsmodell zwischen einem Peridotit-Nebengestein ähnlich wie in den Jetty Halbinsel Xenolithen und einer Schmelze vorgeschlagen, die aus ultramafischen Gängen innerhalb der Lithosphäre stammte. Die Kombination aus Isochronenalter und Modellalter der Vulkanite und der Xenolithe zeigt, daß nach der Bildung vor 1.2 Ga die Lithosphäre zwei Anreicherungsereignisse vor 0.9-1.0 Ga und 0.6 Ga erfahren hatte. Trotz der hohen Variation der¹⁴³Nd/¹⁴⁴Nd Verhältnisse ergeben sich für die unteren Lavaströme höhere Werte, während die oberen Bereiche an¹⁴³Nd verarmt sind. Dies kann auf eine stetige Abnahme des Gang/Peridotit Verhältnisses von 35% auf 10% zurückgeführt werden, das auf eine fortschreitende Aufheizung der Quellenregion hinweist. Die Variation im¹⁴³Nd/¹⁴⁴Nd System wird aber nicht von einem Anstieg des⁸⁷Sr/⁸⁶Sr Verhältnisses begleitet, was mit ähnlichen Werten sowohl für die Gänge als auch für den angrenzenden Peridotit erklärt werden kann: das Nebengestein bestand aus einem angereicherten Peridotit, während die Gänge hauptsächlich aus Klinopyroxen und Amphibol zusammengesetzt waren. SEE-reiche Phasen wie Apatit und Perowskit kamen in so geringen Mengen vor, daß die Gesamtzusammensetzung der Gänge hohe Sr/Nd-Verhältnisse hatte. Rb-Sr Altersbestimmungen an Gesamtgesteinen der Manning Massiv-Vulkanite ergeben eine scheinbare Isochrone von 40±1.2 Ma (I_Sr = 0.70762), obwohl diese Altersinformation vermutlich durch die Mischungsprozesse während des partiellen Schmelzens verfälscht ist.

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Guiding ecological principles for marine spatial planning     

Melissa M. Foley  Benjamin S. Halpern  Fiorenza Micheli  Matthew H. Armsby  Margaret R. Caldwell  Caitlin M. Crain  Erin Prahler  Nicole Rohr  Deborah Sivas  Michael W. Beck  Mark H. Carr  Larry B. Crowder  J. Emmett Duffy  Sally D. Hacker  Karen L. McLeod  Stephen R. Palumbi  Charles H. Peterson  Helen M. Regan  Mary H. Ruckelshaus  Paul A. Sandifer  Robert S. Steneck 《Marine Policy》2010

The declining health of marine ecosystems around the world is evidence that current piecemeal governance is inadequate to successfully support healthy coastal and ocean ecosystems and sustain human uses of the ocean. One proposed solution to this problem is ecosystem-based marine spatial planning (MSP), which is a process that informs the spatial distribution of activities in the ocean so that existing and emerging uses can be maintained, use conflicts reduced, and ecosystem health and services protected and sustained for future generations. Because a key goal of ecosystem-based MSP is to maintain the delivery of ecosystem services that humans want and need, it must be based on ecological principles that articulate the scientifically recognized attributes of healthy, functioning ecosystems. These principles should be incorporated into a decision-making framework with clearly defined targets for these ecological attributes. This paper identifies ecological principles for MSP based on a synthesis of previously suggested and/or operationalized principles, along with recommendations generated by a group of twenty ecologists and marine scientists with diverse backgrounds and perspectives on MSP. The proposed four main ecological principles to guide MSP—maintaining or restoring: native species diversity, habitat diversity and heterogeneity, key species, and connectivity—and two additional guidelines, the need to account for context and uncertainty, must be explicitly taken into account in the planning process. When applied in concert with social, economic, and governance principles, these ecological principles can inform the designation and siting of ocean uses and the management of activities in the ocean to maintain or restore healthy ecosystems, allow delivery of marine ecosystem services, and ensure sustainable economic and social benefits.  相似文献