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11.
Olga Didova Brian Gunter Riccardo Riva Roland Klees Lutz Roese-Koerner 《Journal of Geodesy》2016,90(11):1207-1221
12.
Zircon M127 – A Homogeneous Reference Material for SIMS U–Pb Geochronology Combined with Hafnium,Oxygen and,Potentially, Lithium Isotope Analysis 下载免费PDF全文
Lutz Nasdala Fernando Corfu John W. Valley Michael J. Spicuzza Fu‐Yuan Wu Qiu‐Li Li Yue‐Heng Yang Chris Fisher Carsten Münker Allen K. Kennedy Peter W. Reiners Andreas Kronz Michael Wiedenbeck Richard Wirth Chutimun Chanmuang Manuela Zeug Tamás Váczi Nicholas Norberg Tobias Häger Alfred Kröner Wolfgang Hofmeister 《Geostandards and Geoanalytical Research》2016,40(4):457-475
In this article, we document a detailed analytical characterisation of zircon M127, a homogeneous 12.7 carat gemstone from Ratnapura, Sri Lanka. Zircon M127 has TIMS‐determined mean U–Pb radiogenic isotopic ratios of 0.084743 ± 0.000027 for 206Pb/238U and 0.67676 ± 0.00023 for 207Pb/235U (weighted means, 2s uncertainties). Its 206Pb/238U age of 524.36 ± 0.16 Ma (95% confidence uncertainty) is concordant within the uncertainties of decay constants. The δ18O value (determined by laser fluorination) is 8.26 ± 0.06‰ VSMOW (2s), and the mean 176Hf/177Hf ratio (determined by solution ICP‐MS) is 0.282396 ± 0.000004 (2s). The SIMS‐determined δ7Li value is ?0.6 ± 0.9‰ (2s), with a mean mass fraction of 1.0 ± 0.1 μg g?1 Li (2s). Zircon M127 contains ~ 923 μg g?1 U. The moderate degree of radiation damage corresponds well with the time‐integrated self‐irradiation dose of 1.82 × 1018 alpha events per gram. This observation, and the (U–Th)/He age of 426 ± 7 Ma (2s), which is typical of unheated Sri Lankan zircon, enable us to exclude any thermal treatment. Zircon M127 is proposed as a reference material for the determination of zircon U–Pb ages by means of SIMS in combination with hafnium and stable isotope (oxygen and potentially also lithium) determination. 相似文献
13.
Impact melt‐bearing clastic deposits (suevites) are one of the most important records of the impact cratering process. A deeper understanding of their composition and formation is therefore essential. This study focuses on impact melt particles in suevite at Ries, Germany. Textures and chemical evidence indicate that the suevite contains three melt types that originate from different shock levels in the target. The most abundant melt type (“melt type 1”) represents well‐mixed whole‐rock melting of crystalline basement and includes incompletely mixed mafic melt schlieren (“melt type 1 mafic”). Polymineralic melt type 2 comprises mixes between monomineralic melt types 3 and melt type 1. Melt types 2 and 3 are located within melt type 1 as small patches or schlieren but also isolated within the suevite matrix. The main melt type 1 is heterogeneous with respect to trace elements, varying geographically around the crater: in the western sector, it has lower values in trace elements, e.g., Ba, Zr, Th, and Ce, than in the eastern sector. The west–east zoning likely reflects the heterogeneous nature of crystalline basement target rocks with lower trace element contents, e.g., Ba, Zr, Th, and Ce, in the west compared to the east. The chemical zoning pattern of suevite melt type 1 indicates that mixing during ejection and emplacement occurred only on a local (hundreds of meters) scale. The incomplete larger scale mixing indicated by the preservation of these local chemical signatures, and schlieren corroborate the assumption that mixing, ejection, and quenching were very rapid, short‐lived processes. 相似文献
14.
Tasha L. Dunn Oriana K. Battifarano Juliane Gross Emma J. O'Hara 《Meteoritics & planetary science》2018,53(10):2165-2180
Based on the chemical heterogeneity of chondrule and matrix olivine, Northwest Africa (NWA) 5343 is the least metamorphosed CK chondrite reported so far. To better constrain the lower limit of metamorphism in the CK chondrites, we performed a detailed analysis of matrix material in NWA 5343, including characterization of the texture and bulk composition and analyses of individual silicate minerals. Results suggest that NWA 5343 is petrologic type 3.6 or 3.7. Although silicate minerals in the matrix seem to be equilibrated to roughly the same extent throughout the sample, there are recognizable differences in grain size and shape. These textural differences may be the result of transient heating events during impacts, which would be likely on the CK chondrite parent body. The difference between the extent of chemical equilibration and texture may also suggest that grain size and shape are still sensitive to metamorphism at petrologic subtypes where silicate mineral equilibration is nearly complete (e.g., >3.7). Carbonate material present in NWA 5343 is a product of terrestrial weathering; however, infiltration of a Ca-bearing fluid did not influence the composition of silicate minerals in the matrix. To evaluate the possibility of a continuous metamorphic sequence between the CV and CK chondrites, the bulk matrix composition of NWA 5343 is compared to the CVred chondrite, Vigarano. Although the matrix composition of NWA 5343 could be derived by secondary processing of a Vigarano-like precursor, porosity and texture of matrix olivine in NWA 5343 are hard to reconcile with a continuous metamorphic sequence. 相似文献
15.
Thomas Kenkmann Alex Deutsch Klaus Thoma Matthias Ebert Michael H. Poelchau Elmar Buhl Eva-Regine Carl Andreas N. Danilewsky Georg Dresen Anja Dufresne Nathanaël Durr Lars Ehm Christian Grosse Max Gulde Nicole Güldemeister Christopher Hamann Lutz Hecht Stefan Hiermaier Tobias Hoerth Astrid Kowitz Falko Langenhorst Bernd Lexow Hanns-Peter Liermann Robert Luther Ulrich Mansfeld Dorothee Moser Manuel Raith Wolf Uwe Reimold Martin Sauer Frank Schäfer Ralf Thomas Schmitt Frank Sommer Jakob Wilk Rebecca Winkler Kai Wünnemann 《Meteoritics & planetary science》2018,53(8):1543-1568
This paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two-stage light-gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane-driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high-temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters. 相似文献
16.
Changes in global gravitational energy induced by earthquakes 总被引:1,自引:0,他引:1
Benjamin Fong Chao Richard S. Gross Da-Nan Dong 《Geophysical Journal International》1995,122(3):784-789
17.
Robert S. Webb Jonathan T. Overpeck David M. Anderson Bruce A. Bauer Mildred K. England Wendy S. Gross E. Ann Meyers Michael M. Worobec 《Journal of Paleolimnology》1993,9(1):69-75
Conclusion The World Data Center-A for Paleoclimatology, located in the NOAA/NGDC Paleoclimatology Program, is committed to providing the scientific community with easy access to all paleoenvironmental data. Efforts to make archived data readily available include international coordination of data acquisition, management, and distribution, sponsoring workshops and data cooperatives to facilitate the compilation of important data sets, development of a browse and visualization software package (PaleoVu), and dispersal of archived data on magnetic media or over ANONYMOUS FTP/INTERNET. The program publishes a semi-annual newsletter that highlights latest developments and accomplishments in the area of paleoenvironmental data for global change research. Contributions to the newsletter are welcome from researchers describing their efforts to coordinate the free flow of paleoclimate data throughout the international scientific community.For information on the program or to be added to the mailing list contact Mrs Mildred England (phone: 303-497-6227; Fax: 303 497-6513; e-mail: MKE@mail.ngdc.noaa.gov), NOAA National Geophysical Data Center, Paleoclimatology Program/World Data Center-A for Paleoclimatology, 325 Broadway, E/GC Boulder, CO 80303 USA 相似文献
18.
Lutz Hasse 《Boundary-Layer Meteorology》1990,50(1-4):139-146
This paper provides an historical perspective on micrometeorological field experiments designed to evaluate air-sea interaction processes. Of course, marine meteorology is much older, and air-sea interaction has always been an inevitable part of it. But only in this century have the tools been developed to go from qualitative understanding towards quantitative measurements of interactions. 相似文献
19.
20.
Single-crystal Raman spectra of marcasite-type FeS2, FeSe2, and FeTe2 and loellingite-type FeP2, FeAs2, and FeSb2 are presented and discussed with reference to the energies of the two X-X stretching modes v
x-x (A
g, B
1g) and the four X2 librations Rx2 (A
g, B
1g, B
2g, B
3g). The main results obtained are that (i) the intraionic X-X bonds of FeS2 marcasite and FeS2 pyrite are nearly equal in strengths (mean values of the S-S stretching modes 418 and 420 cm-1, respectively) and (ii) the interactions of the metal ions and the dumbbell-like X2 units increase on going from the chalcogenides to the respective pnictides and from FeS2 marcasite to pyrite (as shown from the frequencies of the X2 librations). 相似文献