An Alternative Protocol for Single Zircon Dissolution with Application to (U‐Th‐Sm)/He Thermochronometry          下载免费PDF全文

Bouchaïb Tibari  Arnaud Vacherat  Martin Stab  Raphaël Pik  Delphine Yeghicheyan  Pascal Hild 《Geostandards and Geoanalytical Research》2016,40(3):365-375

Zircon (U‐Th‐Sm)/He (ZHe) thermochronometry is a powerful tool that has been widely used in geology to constrain the exhumation histories of orogens. In this study, we present an alternative protocol for dissolving zircon grains for determination of parent nuclides. This new alkali fusion procedure developed at the SARM (Service d'Analyse des Roches et des Minéraux) in Nancy, France, is fast (requiring only 2 d, including cleaning steps) and offers several advantages over conventional methods by avoiding: (i) use of HF pressure dissolution and (ii) complete removing of grains from the metal microvials. After dissolution, U, Th and Sm were measured using an ICP‐MS. We tested the new procedure on two different ZHe reference materials, the Fish Canyon Tuff and Buluk Tuff; these provided precision values for ZHe‐age estimations of 9 and 6% (1s), respectively. In addition, using this method, zircons from the Buluk Tuff are shown to be chemically more homogenous and more suitable for assessing the uncertainty of the entire integrated procedure.  相似文献   

Routine Analyses of Trace Elements in Geological Samples using Flow Injection and Low Pressure On-Line Liquid Chromatography Coupled to ICP-MS: A Study of Geochemical Reference Materials BR, DR-N, UB-N, AN-G and GH   总被引：6，自引：0，他引：6  

Jean Carignan  Pascal Hild  Guy Mevelle  Jacques Morel  Delphine Yeghicheyan 《Geostandards and Geoanalytical Research》2001,25(2-3):187-198

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Geodynamic implications of deep mantle upwelling in the source of Tertiary volcanics from the Veneto region (South-Eastern Alps)     

Patrizia Macera  Daniela Gasperini  Claudia Piromallo  Janne Blichert-Toft  Delphine Bosch  Aldo Del Moro  Silvana Martin 《Journal of Geodynamics》2003,36(5):563

Major and trace element and Sr–Nd–Hf–Pb isotopic data for the most primitive Tertiary lavas from the Veneto region (South-Eastern Alps, Italy) show the typical features of HIMU hotspot volcanism, variably diluted by a depleted asthenospheric mantle component (⁸⁷Sr/⁸⁶Sr_i=0.70306–0.70378; _Ndi=+3.9 to +6.8; _Hfi=+6.4 to +8.1, ²⁰⁶Pb/²⁰⁴Pb_i=18.786–19.574). P-wave seismic tomography of the mantle below the Veneto region shows the presence of low-velocity anomalies at depth, which is consistent with possible upwellings of plume material. Between the depths of 100–250 km the velocity anomalies are approximately 2–2.5% slower than average, implying a temperature excess of about 220–280 K, in agreement with estimates for other mantle plumes in the world. In this context, the Veneto volcanics may represent the shallow expression of a mantle upflow. The presence of a HIMU-DM component in a collision environment has significant geodynamic implications. Slab detachment and ensuing rise of deep mantle material into the lithospheric gap is proposed to be a viable mechanism of hotspot magmatism in a subduction zone setting.  相似文献   

Review komatiites: from Earth’s geological settings to planetary and astrobiological contexts     

Delphine Nna-Mvondo  Jesus Martinez-Frias 《Earth, Moon, and Planets》2007,100(3-4):157-179

Komatiites are fascinating volcanic rocks. They are among the most ancient lavas of the Earth following the 3.8 Ga pillow basalts at Isua and they represent some of the oldest ultramafic magmatic rocks preserved in the Earth’s crust at 3.5 Ga. This fact, linked to their particular features (high magnesium content, high melting temperatures, low dynamic viscosities, etc.), has attracted the community of geoscientists since their discovery in the early sixties, who have tried to determine their origin and understand their meaning in the context of terrestrial mantle evolution. In addition, it has been proposed that komatiites are not restricted to our planet, but they could be found in other extraterrestrial settings in our Solar System (particularly on Mars and Io). It is important to note that komatiites may be extremely significant in the study of the origins and evolution of Life on Earth. They not only preserve essential geochemical clues of the interaction between the pristine Earth rocks and atmosphere, but also may have been potential suitable sites for biological processes to develop. Thus, besides reviewing the main geodynamic, petrological and geochemical characteristics of komatiites, this paper also aims to widen their investigation beyond the classical geological prospect, calling attention to them as attractive rocks for research in Planetology and Astrobiology.  相似文献   

On the origin of the dichotomy of early-type galaxies: the role of dry mergers and active galactic nucleus feedback     

X. Kang  Frank C. van den Bosch  A. Pasquali 《Monthly notices of the Royal Astronomical Society》2007,381(1):389-400

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Sedimentological and stratigraphic evolution of northern Lebanon since the Late Cretaceous: implications for the Levant margin and basin     

Nicolas Hawie  Remy Deschamps  Fadi H. Nader  Christian Gorini  Carla Müller  Delphine Desmares  Ahmed Hoteit  Didier Granjeon  Lucien Montadert  François Baudin 《Arabian Journal of Geosciences》2014,7(4):1323-1349

This paper presents an updated review of the Upper Mesozoic and Cenozoic sedimentological and stratigraphic evolution of the Levant margin with a focus on the northern Lebanon. Facies and microfacies analysis of outcrop sections and onshore well cores (i.e., Kousba and Chekka) supported by nannofossil and planktonic foraminifers biostratigraphy, allowed to constrain the depositional environments prevailing in the Turonian to Late Miocene. The “Senonian” (a historical term used to define the Coniacian to Maastrichtian) source rock interval was subdivided into four sub-units with related outer-shelfal facies: (1) Upper Santonian, (2) Lower, (3) Upper Campanian, and (4) Lower Maastrichtian. This Upper Cretaceous rock unit marks the major drowning of the former Turonian rudist platform. This paper confirms the Late Lutetian to Late Burdigalian hiatus, which appears to be a direct consequence of major geodynamic events affecting the Levant region (i.e., the continued collision of Afro-Arabia with Eurasia), potentially enhanced by regressional cycles (e.g., Rupelian lowstand). The distribution of Late Burdigalian–Serravallian rhodalgal banks identified in northern Lebanon was controlled by pre-existing structures inherited from the pulsating onshore deformation. Reef barriers facies occur around the Qalhat anticline, separating an eastern, restricted back-reef setting from a western, coastal to open marine one. The acme of Mount Lebanon’s uplift and exposure is dated back to the Middle–Late Miocene; it led to important erosion of carbonates that were subsequently deposited in paleo-topographic lows. The Late Cretaceous to Cenozoic facies variations and hiatuses show that the northern Lebanon was in a higher structural position compared to the south since at least the Late Cretaceous.  相似文献   

Origin and significance of poikilitic and mosaic peridotite xenoliths in the western Pannonian Basin: geochemical and petrological evidences     

Antal?Embey-IsztinEmail author  Gábor?Dobosi  Jean-Louis?Bodinier  Delphine?Bosch  G.?A.?Jenner  Simone?Pourtales  Olivier?Bruguier 《Contributions to Mineralogy and Petrology》2014,168(3):1054

Peridotite xenoliths erupted by alkali basaltic volcanoes in the western Pannonian Basin can be divided into two fundamentally contrasting groups. Geochemical characteristics of the abundant protogranular, porphyroclastic and equigranular nodules suggest that these samples originate from an old consolidated and moderately depleted lithospheric mantle domain. In contrast, the geochemical features of the worldwide rare, but in the Pannonian Basin relatively abundant, poikilitic xenoliths attest to a more complex evolution. It has been argued that the origin of the peculiar texture and chemistry may be intimately linked to melt/rock reactions at successively decreasing liquid volumes in a porous melt flow system. The most likely site where such reactions can take place is the asthenosphere–lithosphere boundary. In this context, poikilitic xenoliths may provide petrological and geochemical evidence for reactions between magmatic liquids issued from the uprising asthenosphere and the solid mantle rocks of the lithosphere. These reactions are important agents of the thermal erosion of the lithosphere; thus, they could have considerably contributed to the thinning of the lithosphere in the Pannonian region. We suggest that in the Pannonian Basin, there could be a strong relation between the unusual abundance of poikilitic mantle xenoliths and the strongly eroded lithosphere.  相似文献   

Geochemical evidence (C,N and Pb isotopes) of recent anthropogenic impact in south‐central Chile from two environmentally distinct lake sediment records     

Nathalie Fagel  Sebastien Bertrand  Nadine Mattielli  Delphine Gilson  Luis Chirinos  Gilles Lepoint  Roberto Urrutia 《第四纪科学杂志》2010,25(7):1100-1112

In this paper, we compare the elemental and isotopic (C, N, Pb) geochemistry of lake sediments from two contrasted environments in south‐central Chile. The first lake, Laguna Chica de San Pedro (LCSP), is situated in the urbanised area of the Biobio Region (36°S). The second lake, Lago Puyehue (40° S), is located 400 km to the southeast of LCSP and within an Andean national park. Our aim is to identify environmental impacts associated with increasing industrial activities and land degradation during the last 150 a. In LCSP, shifts in C/N atomic ratios, δ¹³C and δ¹⁵N from 1915–1937 to the late 1980s are attributed to successive land degradation episodes in the lake watershed. Based on a Pb isotopic mixing model, we estimate that up to 20% of lead in LCSP sediments is supplied from urban atmospheric pollution. By contrast, human impact in the watershed of Lago Puyehue is very limited. We observe no change in organic geochemistry during the last 150 a and lead contamination remains lower than 5%, even during the last decades. Although contamination levels are much higher in LCSP than in Lago Puyehue, a peak in anthropogenic Pb is recorded during the same period (1974–1976) at both sites. This maximum contamination level is consistent with increased industrial activity in the vicinity of Concepción. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Narrow-band CCD photometry of giant H ii regions     

Guillermo Bosch †  Elena Terlevich ‡  Roberto Terlevich § 《Monthly notices of the Royal Astronomical Society》2002,329(3):481-496

We have obtained accurate CCD narrow-band Hβ and Hα photometry of giant H  ii regions (GEHRs) in M33, NGC 6822 and M101. Comparison with previous determinations of emission-line fluxes shows large discrepancies; their probable origins are discussed. Combining our new photometric data with global velocity dispersion ( σ ) derived from emission linewidths, we review the     relation. A re-analysis of the properties of the GEHRs included in our sample shows that age spread and the superposition of components in multiple regions introduce a considerable spread in the regression. Combining the information available in the literature regarding ages of the associated clusters, evolutionary footprints on the interstellar medium, and kinematical properties of the knots that build up the multiple GEHRs, we find that a subsample – which we refer to as young and single GEHRs – do follow a tight relation in the     plane.  相似文献   

Water temperature and conductivity variability as indicators of groundwater behaviour in complex aquifer systems in the south‐east of Spain     

L. Molina  A. Vallejos  A. Pulido‐Bosch  F. Snchez‐Martos 《水文研究》2002,16(17):3365-3378

Groundwater temperature and electrical conductivity logs were applied in this study to gain an understanding of the hydrogeological behaviour of a complex system. This system, compartmentalized by a large number of fractures, which may even cause geothermal anomalies, is that of the Campo de Dalías in the south‐east of the Iberian Peninsula. In addition to this complexity one must consider the different levels with aquifer properties and their varying lithologies, which in some cases are in direct contact with the sea. Vertical sections based upon the various logs allow lateral correlation to be made between the anomalies detected, and provide information on the existence of both ascending and descending vertical flows, and the inflow of sea water into the system. Analysis of environmental isotopes (¹⁸O and D) indicate the areas of recharge with the greatest flow velocity. No seasonal variation in the isotopes was observed, which suggests that the residence time of the groundwater in the aquifer is several years. Radiocarbon dating gave estimates of generally long residence times, although in some sectors it is possible to detect the current recharge based on its tritium content, from rainwater infiltration or seawater intrusion. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献