Morphometric variation among sardine (Sardina pilchardus) populations from the northeastern Atlantic and the western Mediterranean     

Silva  Alexandra 《ICES Journal of Marine Science》2003,60(6):1352-1360

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Natural hazards in Australia: droughts   总被引：3，自引：0，他引：3  

Anthony S. Kiem  Fiona Johnson  Seth Westra  Albert van Dijk  Jason P. Evans  Alison O’Donnell  Alexandra Rouillard  Cameron Barr  Jonathan Tyler  Mark Thyer  Doerte Jakob  Fitsum Woldemeskel  Bellie Sivakumar  Raj Mehrotra 《Climatic change》2016,139(1):37-54

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Natural hazards in Australia: floods     

Fiona Johnson  Christopher J. White  Albert van Dijk  Marie Ekstrom  Jason P. Evans  Dörte Jakob  Anthony S. Kiem  Michael Leonard  Alexandra Rouillard  Seth Westra 《Climatic change》2016,139(1):21-35

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Experiments on melt–rock reaction in the shallow mantle wedge     

Alexandra?L.?MitchellEmail author  Timothy?L.?Grove 《Contributions to Mineralogy and Petrology》2016,171(12):107

This experimental study simulates the interaction of hotter, deeper hydrous mantle melts with shallower, cooler depleted mantle, a process that is expected to occur in the upper part of the mantle wedge. Hydrous reaction experiments (~6 wt% H₂O in the melt) were conducted on three different ratios of a 1.6 GPa mantle melt and an overlying 1.2 GPa harzburgite from 1060 to 1260 °C. Reaction coefficients were calculated for each experiment to determine the effect of temperature and starting bulk composition on final melt compositions and crystallizing assemblages. The experiments used to construct the melt–wall rock model closely approached equilibrium and experienced <5% Fe loss or gain. Experiments that experienced higher extents of Fe loss were used to critically evaluate the practice of “correcting” for Fe loss by adding iron. At low ratios of melt/mantle (20:80 and 5:95), the crystallizing assemblages are dunites, harzburgites, and lherzolites (as a function of temperature). When the ratio of deeper melt to overlying mantle is 70:30, the crystallizing assemblage is a wehrlite. This shows that wehrlites, which are observed in ophiolites and mantle xenoliths, can be formed by large amounts of deeper melt fluxing though the mantle wedge during ascent. In all cases, orthopyroxene dissolves in the melt, and olivine crystallizes along with pyroxenes and spinel. The amount of reaction between deeper melts and overlying mantle, simulated here by the three starting compositions, imposes a strong influence on final melt compositions, particularly in terms of depletion. At the lowest melt/mantle ratios, the resulting melt is an extremely depleted Al-poor, high-Si andesite. As the fraction of melt to mantle increases, final melts resemble primitive basaltic andesites found in arcs globally. An important element ratio in mantle lherzolite composition, the Ca/Al ratio, can be significantly elevated through shallow mantle melt–wall rock reaction. Wall rock temperature is a key variable; over a span of <80 °C, reaction with deeper melt creates the entire range of mantle lithologies from a depleted dunite to a harzburgite to a refertilized lherzolite. Together, the experimental phase equilibria, melt compositions, and reaction coefficients provide a framework for understanding how melt–wall rock reaction occurs in the natural system during melt ascent in the mantle wedge.  相似文献   

Relationship between Na<Subscript>2</Subscript>SO<Subscript>4</Subscript> concentration and thermal response of reconstituted stone in the laboratory and on site     

Céline Thomachot-Schneider  Maxime Gommeaux  Norman Lelarge  Alexandra Conreux  Kamel Mouhoubi  Jean-Luc Bodnar  Patricia Vázquez 《Environmental Earth Sciences》2016,75(9):762

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Influence of different land uses on groundwater quality in southern Portugal     

Alexandra Marchã Penha  António Chambel  Martinho Murteira  Manuela Morais 《Environmental Earth Sciences》2016,75(7):622

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Diamond precipitation from ascending reduced fluids in the Kaapvaal lithosphere: Thermodynamic constraints     

Jan Marten Huizenga  Alexandra Crossingham  Fanus Viljoen 《Comptes Rendus Geoscience》2012,344(2):67-76

Previous research has shown that the Kaapvaal lithospheric mantle is generally reduced and characterised by a decreasing redox state with increasing depth. As a consequence, C-O-H fluids in the Kaapvaal lithospheric mantle are dominated by H₂O, CH₄, and C₂H₆. Thermodynamic calculations demonstrate that diamond precipitation from such a fluid during ascend is possible as it is exposed to a more oxidised environment and both CH₄ and C₂H₆ are oxidised. However, the calculations also demonstrate that the diamond precipitation potential from such a fluid decreases when: (1) the mantle is either more reduced or oxidised compared to the Kaapvaal mantle, or (2) the change in temperature with pressure is smaller compared to that of the Kaapvaal mantle. Therefore, the presence of reduced mantle fluid species and a generally decreasing oxygen fugacity with increasing depth do not necessarily warrant diamond precipitation from a rising reduced fluid.  相似文献   

Paleoproterozoic mafic dyke swarms of the Belomorian Province,eastern Fennoscandian Shield     

Alexandra Stepanova  Vladimir Stepanov 《Precambrian Research》2010

Paleoproterozoic mafic igneous rocks (2450–1970 Ma) are exposed in the form of layered intrusions, dykes, and volcanic rocks in the Karelian, Kola and Murmansk provinces and in the form of dykes and small intrusions in the Belomorian Province, Eastern Fennoscandian Shield. The age and sequence of mafic dyke emplacement during the Paleoproterozoic are very similar in these regions. Further comparisons of geochemical characteristics of mafic dyke swarms in the Belomorian Province and neighboring cratons show considerable similarities.  相似文献   

The Hubble Deep Field North SCUBA Super-map – III. Optical and near-infrared properties of submillimetre galaxies     

Alexandra Pope  Colin Borys  Douglas Scott  Christopher Conselice  Mark Dickinson  Bahram Mobasher 《Monthly notices of the Royal Astronomical Society》2005,358(1):149-167

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Testing variations within the Tagish Lake meteorite—II: Whole‐rock geochemistry of pristine samples     

Alexandra I. Blinova  Christopher D. K. Herd  M. John M. Duke 《Meteoritics & planetary science》2014,49(6):1100-1118

Four pristine specimens of the Tagish Lake C2 chondrite meteorite were previously determined through mineralogy, petrology, and organic chemistry to have been affected by aqueous alteration in the order (from least to most altered) TL5b < TL11h < TL11i, and TL11v as a mixture of the other specimens (Herd et al. 2011 ; Blinova et al. 2014 ). Here, we report the whole‐rock data for a total of 65 elements for the same four Tagish Lake samples as determined by ICP‐MS and ICP‐AES (utilizing the Parr bomb digestion method on small samples, approximately 50 mg), and by INAA. Our data demonstrate that the determined aqueous alteration sequence has a positive correlation with trace elements, such as K and Br that are mobile during aqueous alteration, which appear to be controlled by an increase of phyllosilicates from least to most altered samples. Yet, the homogeneity of other elements suggests that elemental mass transfer occurred on a localized scale and aqueous alteration was isochemical for these elements, similar to other primitive carbonaceous chondrites. By plotting data from three samples (TL5b, TL11h, and TL11i) on a Zn/Mn versus Sc/Mn diagram, we also confirm that the Tagish Lake meteorite is not a simple mixture of CI and CM material.  相似文献