Glaciation in the Andes during the Lateglacial and Holocene     

Donald T. Rodbell  Jacqueline A. Smith  Bryan G. Mark   《Quaternary Science Reviews》2009,28(21-22):2165-2212

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Sheath fold formation around slip surfaces     

Jacqueline E. Reber  Marcin Dabrowski  Daniel W. Schmid 《地学学报》2012,24(5):417-421

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Characterising modal metasomatic processes in young continental lithospheric mantle: a microsampling isotopic and trace element study on xenoliths from the Middle Atlas Mountains,Morocco     

Jacqueline Malarkey  Nadine Wittig  D. Graham Pearson  Jon P. Davidson 《Contributions to Mineralogy and Petrology》2011,162(2):289-302

Clinopyroxene is a major host for lithophile elements in the mantle lithosphere, and therefore it is critical whether we are to understand the constraints that this mineral puts on mantle evolution and melt generation. This study presents a detailed in situ trace element and Sr isotope study of clinopyroxene, amphibole and melt from two spinel lherzolites from the Middle Atlas Mountains, Morocco. The results show that there is limited, but discernable, Sr isotopic variation between clinopyroxene crystals within these xenoliths [⁸⁷Sr/⁸⁶Sr ranging from 0.703416 (±11 2SE) to 0.703681 (±12 2SE)]. Trace element patterns show similar interelement fractionation with LREE enrichment, but there is a considerable range in terms of elemental concentration (e.g. over 100 ppm in Sr concentrations). Observed modal clinopyroxene is far more abundant than that predicted from estimates of melt depletion. This along with isotope and trace element variability found in these xenoliths supports a multistage metasomatic process in which clinopyroxene and amphibole are recent secondary additions to the lithospheric mantle. Elemental systematics indicate that the metasomatic mineral assemblage has most recently equilibrated with a carbonatitic melt prior to inclusion in the host basalt. The clinopyroxene from this study is typical of global off-craton clinopyroxene in terms of Sr isotope composition, suggesting that the majority of clinopyroxene in off-craton settings may have a recent metasomatic origin. These findings indicate that caution is required when using peridotite xenoliths to estimate the degree of elemental enrichment in the subcontinental lithosphere.  相似文献   

Three criteria reliability analyses for groundwater recharge estimations     

Nara Somaratne  Keith Smettem  Jacqueline Frizenschaf 《Environmental Earth Sciences》2014,72(6):2141-2151

There is a broad variety of methods to estimate groundwater recharge, but tools to assess the reliability of particular methods are not available. This paper introduces three distinct criteria to assess the reliability of recharge: applicability of the method used, availability of reliable data, and spatial coverage. Weightings of each criterion are assigned using key attributes present to total attributes required under each criterion. A reliability assessment was applied to two point-recharge and two diffuse-recharge dominated groundwater basins in South Australia. We show that the use of groundwater age based on chlorofluorocarbon and the conventional chloride mass balance method gives unreliable estimates of recharge in karstic aquifers, primarily due to inappropriate assumptions concerning the nature of recharge in these systems. Among the methods evaluated, watertable fluctuation, numerical groundwater modelling, Darcy flow calculation and the water budget method are applied to both point and diffuse recharge dominant groundwater basins. The reliability of these methods depends primarily on the quality of data and spatial coverage of the basin. Once the reliability level is known, water resources planners and managers assess the level of risk to aquifers, the environment, and the socio-economic development required for sustainable management of groundwater.  相似文献   

The Planetary Nebula A 79 Revisited: Discovery of a Large Emission Nebula     

Hua Chon-Trung  Jacqueline Martinis 《Astrophysics and Space Science》2002,281(4):777-784

New observations of the planetary nebula A 79 using selective interference filters (Δ λ ≤ 10 Å) are reported. Thanks to the large field of view (< 11″5) offered by the Observatoire de Haute Provence 120-cm telescope we were able to discover a new extended feature close to A 79.  相似文献   

Australia Telescope Compact Array 1.2-cm observations of the massive star-forming region G305.2+0.2     

Andrew J. Walsh  Jacqueline F. Chapman  Michael G. Burton  Mark Wardle  T. J. Millar 《Monthly notices of the Royal Astronomical Society》2007,380(4):1703-1714

We report on Australia Telescope Compact Array observations of the massive star-forming region G305.2+0.2 at 1.2 cm. We detected emission in five molecules towards G305A, confirming its hot core nature. We determined a rotational temperature of 26 K for methanol. A non-local thermodynamic equilibrium excitation calculation suggests a kinematic temperature of the order of 200 K. A time-dependent chemical model is also used to model the gas-phase chemistry of the hot core associated with G305A. A comparison with the observations suggest an age of between  2 × 10⁴  and  1.5 × 10⁵ yr  . We also report on a feature to the south-east of G305A which may show weak Class I methanol maser emission in the line at 24.933 GHz. The more evolved source G305B does not show emission in any of the line tracers, but strong Class I methanol maser emission at 24.933 GHz is found 3 arcsec to the east. Radio continuum emission at 18.496 GHz is detected towards two H  ii regions. The implications of the non-detection of radio continuum emission towards G305A and G305B are also discussed.  相似文献   

The north-eastern Polish anorthosite massifs: petrological, geochemical and isotopic evidence for a crustal derivation     

Janina Wiszniewska  Stefan Claesson  Holly Stein  Jacqueline Vander Auwera  Jean-Clair Duchesne 《地学学报》2002,14(6):451-460

ABSTRACT Deeply buried 1.5 Ga Polish anorthosites, accessible only by bore holes, reveal diagnostic features of some massif-type anorthosites (polybarism, jotunitic parent magma), diapirically emplaced in the mid crust together with the rapakivi granites of the EW-trending Mazury complex, intruded along a major crustal discontinuity. Geochemical modelling and isotope data corroborate recent experimental work on the basaltic system in dry conditions: the source rock of the parental magma is a gabbronorite, necessarily lying in the lower crust. Since no Archaean crust is known in the region, high initial ¹⁸⁸Os/¹⁸⁷Os ratios for sulphide-oxide isochrons and negative ε_Nd values are best accounted for by melting a ∼ 2.0 Ga mafic crust.  相似文献   

Magmatic processes under Quizapu volcano,Chile, identified from geochemical and textural studies     

Michael?D.?HigginsEmail author  Stéphanie?Voos  Jacqueline?Vander Auwera 《Contributions to Mineralogy and Petrology》2015,170(5-6):51

Quizapu is part of a linear system of active volcanos in central Chile. The volcanic petrology and geology have been used to infer the plumbing system beneath the volcano. The 1846–1847 eruption (~5 km³) started with small flows of dacite, then changed to a range of andesite–dacite compositions and finally terminated with large flows of dacite. Andesitic enclaves (<10 %) occur in some of these flows. Activity restarted explosively in 1932 (~4 km³ DRE) with an initial andesite–dacite ash, followed by uniform dacite ash and then a terminal andesite ash. All samples, including the enclaves, have chemical compositions that lie on an almost perfect mixing line, with a few exceptions. The abundant plagioclase macrocrysts in the matrix were divided into five petrographic classes on the basis of colour in cold-cathode cathodoluminescence images and zonation in visible light. All populations of macrocrysts have CSDs characteristic of coarsening, although they differ in detail. Two classes can be ascribed to growth in andesite and dacite magmas, but the three other classes are associated with particular magma batches. A model is developed which started with ponding of andesite magma in the crust. This differentiated to produce a dacite magma, most of which probably solidified to make a granodiorite batholith. Activation of a N–S fault enabled volcanism: andesite magma traversed the dacite-filled chamber, heating and raising it up into storage areas hosted by the fault, where it mixed to form a homogeneous magma. A short time before the 1846–1847 eruption, more andesite magma was injected into the shallow part of the system where it mingled with existing mixed magmas. The first magma to be erupted from Quizapu was a dacite, but soon other storage areas along the fault started to feed the system—first mixed magmas, then back to dacites. The eruption then terminated until 1932 when renewed injection of andesite into the system created a conduit that tapped an undegassed dacite chamber and resulted in a strong explosive eruption. The whole story is one of continual andesite magmatism, modulated by storage, degassing and mixing.  相似文献   

The missing metals problem – III. How many metals are expelled from galaxies?     

Nicolas Bouché  Matthew D. Lehnert  Anthony Aguirre  Céline Péroux  Jacqueline Bergeron 《Monthly notices of the Royal Astronomical Society》2007,378(2):525-540

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Magnetic fabrics of the Douglas Till of the Superior lobe: exploring bed-deformation kinematics     

Jacqueline R. Shumway  Neal R. Iverson 《Quaternary Science Reviews》2009,28(1-2):107-119

The Superior lobe of the Laurentide ice sheet, during its last advance into northwestern Wisconsin, may have moved and transported sediment primarily through deep, widespread shear of its bed to high strains (>100). To study the kinematics of this deformation, we measured the anisotropy of magnetic susceptibility of 3750 intact samples of its basal till—the Douglas member of the Miller Creek formation—collected from eight profiles at 0.2 m depth increments. A benchmark for interpretations was provided by results of ring-shear experiments conducted on the Douglas Till, which provided fabric characteristics for the case of horizontal simple shear. Orientations of maximum susceptibility (k₁) were controlled by preferred orientations of silt-sized magnetite grains and were similar to sand-grain orientations measured in thin sections. Strengths of fabrics formed by orientations of k₁ indicate that most of the till sampled was deformed but to variable strains. Deformation averaged over the 20 km spanned by the study approximated horizontal simple shear. However, large differences in k₁ fabric azimuths (>45°) over lateral distances of meters to tens of meters indicate highly heterogeneous bed deformation, perhaps focused in anastomosing zones with associated divergent and convergent till shear. This interpretation is supported by orientations of principal susceptibilities that imply, in many cases, either that shear planes were steeply dipping, particularly transverse to the shearing direction, or that there were major components of pure shear. Variations in k₁ fabric azimuth with depth indicate that most of the till thickness did not shear simultaneously; rather, till accumulated at the bed as shear direction changed in response to temporally shifting zones of shallow deformation (<1 m). This heterogeneous, temporally variable deformation of the bed differs from many applications of the bed-deformation model but is consistent with subglacial measurements at modern glaciers.  相似文献