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1.
The Lilloise Intrusion, East Greenland: Fractionation of a Hydrous Alkali Picritic Magma 总被引：2，自引：1，他引：1
The Lilloise is an 8 km4 km layered mafic intrusion which cutsthe plateau basalts of the East Greenland Tertiary province.Lilloise was intruded at 50 Ma, 4–5 Ma after cessationof the voluminous tholeiitic magmatism which accompanied riftingof the East Greenland continental margin. Lilloise is unusualamong layered intrusions in the province because it had a hydrousalkali picrite parent magma and generated a late-stage effluxof magmatic water from the intrusion into the aureole rocks.The three major subdivisions of the layered rocks are: olivine-clinopyroxene,olivine-clinopyroxene-plagioclase and plagioclase-amphibolecumulates. Massive subsidence of the intrusion before completesolidification resulted in deformation of the internal layeringand downturn of the bedding in the surrounding basalts. A strikingfeature of the intrusion is the injection of the layered rocksby a plexus of magmatic sheets which formed at the time of subsidence.The composition of these sheets is representative of the fractionationtrend of the intrusion and ranges from hawaiite to mildly saturatedquartz trachyte. The fractionation trend is successfully explainedby extraction of cumulus minerals of the layered rocks froma parent magma represented by alkali picrite dykes of a contemporaneousregional dyke swarm. Saturated to mildly over-saturated syenitesare a major component of the East Greenland province and theLilloise intrusion is illustrative of an important magmatictrend towards such compositions at this stage in the openingof the North Atlantic. KEY WORDS: Lilloise intrusion; East Greenland; alkali picrite magma; layered intrusion; magmatic differentiation
*Corraponding author 相似文献
2.
By ALASTAIR G. WILLIAMS SCOTT CHAMBERS WLODEK ZAHOROWSKI JAGODA CRAWFORD KIYOSHI MATSUMOTO MITSUO UEMATSU 《Tellus. Series B, Chemical and physical meteorology》2009,61(5):732-746
Terrestrial radon-222 flux density for the Asian continent, integrated over distances of 4500 km, is estimated in two 20° latitudinal bands centred on 48.8°N and 63.2°N. The evaluation is based on three years of wintertime radon measurements at Sado Island, Japan, together with meteorological and trajectory information. A selection of 18% of observations are suitable for evaluation of an analytical expression for the continental surface flux. Various meteorological assumptions are discussed; it is found that there is a substantial effect of increased complexity of the formulation on the flux estimates obtained. The distribution of spatially integrated radon flux over the Asian landmass is reported for the first time. Expressed as geometric means and 1σ-ranges, estimated fluxes are 14.1 mBq m−2 s−1 (1σ-range: 18 mBq m−2 s−1 ) and 8.4 mBq m−2 s−1 (1σ-range: 10 mBq m−2 s−1 ) for the lower and higher latitude bands. These results constitute an annual minimum in flux densities for these regions, and are higher than previously reported. The existence of a latitudinal gradient in the continental radon source function is confirmed; the present estimate for Asia (−0.39 mBq m−2 s−1 per degree of latitude) is in agreement with the northern hemisphere terrestrial radon flux gradient proposed previously. 相似文献
3.
Abstract— The main asteroid belt has lost >99.9% of its solid mass since the time at which the planets were forming, according to models for the protoplanetary nebula. Here we show that the primordial asteroid belt could have been cleared efficiently if much of the original mass accreted to form planetsized bodies, which were capable of perturbing one another into unstable orbits. We provide results from 25 N‐body integrations of up to 200 planets in the asteroid belt, with individual masses in the range 0.017–0.33 Earth masses. In the simulations, these bodies undergo repeated close encounters which scatter one another into unstable resonances with the giant planets, leading to collision with the Sun or ejection from the solar system. In response, the giant planets' orbits migrate radially and become more circular. This reduces the size of the main‐belt resonances and the clearing rate, although clearing continues. If ～3 Earth masses of material was removed from the belt this way, Jupiter and Saturn would initially have had orbital eccentricities almost twice their current values. Such orbits would have made Jupiter and Saturn 10–100x more effective at clearing material from the belt than they are on their current orbits. The time required to remove 90% of the initial mass from the belt depends sensitively on the giant planets' orbits, and weakly on the masses of the asteroidal planets. 18 of the 25 simulations end with no planets left in the belt, and the clearing takes up to several hundred million years. Typically, the last one or two asteroidal planets are removed by interactions with planets in the terrestrial region 相似文献
4.
Abstract: Landslide research at the British Geological Survey (BGS) is carried out through a number of activities, including surveying, database development and real-time monitoring of landslides. Landslide mapping across the UK has been carried out since BGS started geological mapping in 1835. Today, BGS geologists use a combination of remote sensing and ground-based investigations to survey landslides. The development of waterproof tablet computers (BGS·SIGMAmobile), with inbuilt GPS and GIS for field data capture provides an accurate and rapid mapping methodology for field surveys. Regional and national mapping of landslides is carried out in conjunction with site-specific monitoring, using terrestrial LiDAR and differential GPS technologies, which BGS has successfully developed for this application. In addition to surface monitoring, BGS is currently developing geophysical ground-imaging systems for landslide monitoring, which provide real-time information on subsurface changes prior to failure events. BGS’s mapping and monitoring activities directly feed into the BGS National Landslide Database, the most extensive source of information on landslides in Great Britain. It currently holds over 14?000 records of landslide events. By combining BGS’s corporate datasets with expert knowledge, BGS has developed a landslide hazard assessment tool, GeoSure, which provides information on the relative landslide hazard susceptibility at national scale. 相似文献
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6.
Radon-222 in boundary layer and free tropospheric continental outflow events at three ACE-Asia sites
7.
Abstract— We describe results of 32 N‐body planetary accretion simulations that investigate the dependence of terrestrial‐planet formation on nebula surface density profile σ and evolution of the eccentricities of Jupiter and Saturn ej,s. Two surface density profiles are examined: a decaying profile with σ ∝ 1/a, where a is orbital semi‐major axis, and a peaked profile in which σ increases for a < 2 AU and decreases for a > 2 AU. The peaked profiles are generated by models of coagulation in an initially hot nebula. Models with initial ej,s = 0.05 (the current value) and 0.1 are considered. Simulations using the decaying profile with ej,s = 0.1 produce systems most like the observed planets in terms of mass‐weighted mean a and the absence of a planet in the asteroid belt. Simulations with doubled σ produce planets roughly twice as massive as the nominal case. Most initial embryos are removed in each simulation via ejection from the solar system or collision with the Sun. The asteroid belt is almost entirely cleared on a timescale of 10–100 Ma that depends sensitively on ej,s. Most initial mass with a < 2 AU survives, with the degree of mass loss increasing with a. Mass loss from the terrestrial region occurs on a timescale that is long compared to the mass loss time for the asteroid belt. Substantial radial mixing of material occurs in all simulations, but is greater in simulations with initital ej,s = 0.05. The degree of mixing is equivalent to a feeding zone of half width 1.5 and 0.9 AU for an Earth mass planet at 1 AU for the cases ej,s = 0.05 and 0.1, respectively. In simulations with ej,s = 0.05, roughly one‐third and 5–10% of the mass contained in final terrestrial planets originated in the region a > 2.5 AU for the decaying and peaked profiles, respectively. In the case ej,s = 0.1, the median mass accreted from a > 2.5 AU is zero for both profiles. 相似文献
8.
KEITH E. BARBER FRANK M. CHAMBERS DARREL MADDY 《Boreas: An International Journal of Quaternary Research》2004,33(2):132-144
Plant macrofossil remains have been analysed from two raised peat bogs in northern Germany and Denmark. The quantified vegetation reconstructions of each profile were subjected to multivariate analyses to extract records of changing bog surface wetness (BSW), which are interpreted in these rain-fed bogs as being proxy climate signals. Age/depth models were constructed using radiocarbon dates and a number of drier and wetter phases were defined. The records both register cooler/wetter conditions around 2700, 1800 and 1400 cal. yr BP, and at the beginning of the Little Ice Age around AD 1250–1350. These rising bog water tables must have been reflected in poorer conditions for agriculture, and in particular near Dosenmoor where the profile records a catastrophic change to such conditions culminating at 2750–2600 cal. yr BP. 相似文献
9.
By Z. KLIMONT J. COFALA J. XING W. WEI C. ZHANG S. WANG J. KEJUN P. BHANDARI R. MATHUR P. PUROHIT P. RAFAJ A. CHAMBERS M. AMANN J. HAO 《Tellus. Series B, Chemical and physical meteorology》2009,61(4):602-617
Estimates of Asian emissions of air pollutants and carbonaceous aerosols and their mid-term projections have been changing significantly in the last years. The remote sensing community has shown that increase in NO x in Central East Asia is much stronger than any of the emission inventories or projections indicated so far. A number of studies reviewing older estimates appeared. Here, we review the key contributions and compare them to the most recent results of the GAINS model application for Asia and to the SRES projections used in the IPPC work. The recent projections indicate that the growth of emissions of SO2 in Asia should slow down significantly towards 2010 or even stabilize at the current level. For NO x , however, further growth is projected although it will be most likely slower that in the last decade, owing to introduction of measures in transport. Emissions of carbonaceous aerosols (black carbon and organic carbon) are expected to decline after 2010, largely due to reduced use of biofuels in residential sector and efficiency improvements. The estimates of these emissions are burdened with significantly larger uncertainties than SO2 and NO x ; even for the year 2000 the differences in estimates between studies are up to a factor of 2. 相似文献
10.
A persistent benthic nepheloid layer with high total suspended matter (TSM) and high total particulate surface area was observed in south-eastern Lake Michigan. The layer thickens from a few metres near the shelf-slope boundary to greater than 10 m at the base of the slope. When compared to the hypolimnion, TSM increases by a factor of 2-20 at 1 m above the bottom, the greatest increase detected at the slope-basin boundary. Sediment trap profiles within the nepheloid layer show that the particulate flux increases exponentially from about 10 m above the bottom to 1 m above the bottom, suggesting that a large fraction of the collected material came from resuspension. A nepheloid layer is created during the formation of the thermal bar and maintained during the stratified period, apparently through the action of weak but persistent currents. This layer is supplemented by lakeward transport of fine particles resuspended near the shelf-slope boundary due to impingement of the thermocline on the bottom, or during higher energy events. 相似文献