THE APPLICATION OF INDUCTIVELY COUPLED PLASMA-QUADRUPOLE MASS SPECTROMETRY TO FOSSIL TEETH FOR U-TH ISOTOPE ANALYSIS     

Shao Qingfeng  E.Douville  N.Frank  M.Fontugne  J.-J.Bahain  C.Falguères 《第四纪研究》2012,32(3)

四极杆电感耦合等离子体质谱仪(Inductively Coupled Plasma-Quadrupole Mass Spectrometry,简称ICP-QMS)可用于U和Th同位素分析.目前,ICP-QMS能实现精度大约为0.3％(U)和1％(Th)的测量分析,可提供误差在1％～10％的230Th/U年代数据.本文用ICP-QMS分析了采自意大利南都Loreto旧石器地点的4颗马牙化石样品,并对已发表的UTEVA树脂提纯U和Th的流程做了进一步改进,使其适用于动物牙化石样品.样品中的U和Th含量的平均测量精度(2σ)分别为0.3％和0.6％;234U/235U和230Th/238U活度比平均精度(2σ)分别为0.3％和0.8％.数据表明同一颗牙化石的不同组织的U含量可有数量级差别,同时它们的U -Th同位素活度比也可显著地离散(＞2σ),从而导致不一致的230Th/U年代结果.如今测定的各牙组织的U-Th同位素数据可用于模拟U的迁移历史;U-系分析与电子自旋共振测年技术相结合或可更好地估计样品的地质年代.  相似文献   

Geochronology of igneous rocks at and near to the Nezhdaninka gold deposit, Yakutia, Russia: U-Pb, Rb-Sr, and Sm-Nd isotopic data     

I. V. Chernyshev  A. G. Bakharev  N. S. Bortnikov  Yu. V. Goltsman  A. B. Kotov  G. N. Gamyanin  A. V. Chugaev  E. B. Sal’nikova  E. D. Bairova 《Geology of Ore Deposits》2012,54(6):411-433

The intrusive rocks associated with the large Nezhdaninka gold deposit (Au > 470 t) hosted in the Permian carbonaceous terrigenous sequence have been dated on zircon and rock-forming minerals with precision U-Pb (ID-TIMS) and Rb-Sr methods. The lamprophyre of the dike complex that occurs in the ore field and spatially is related to gold mineralization has concordant U-Pb zircon age (121 ± 1 Ma) and the same isochron Rb-Sr age (121.0 ± 2.8 Ma). The concordant U-Pb zircon age of granodiorite that dominates in the Kurum pluton is 94 ± 1 Ma, whereas the Rb-Sr isochron age of various intrusive rocks from this pluton is 1–4 Ma younger. This difference is caused by long-term cooling of the Kurum pluton and later closure of Rb-Sr isotopic system of biotite (300–350°C) and other rock-forming minerals as compared with U-Pb isotopic system of zircon (～ 900°C). The Rb-Sr age of quartz diorite from the Gel’dy group of stocks (92.6 ± 0.8 Ma) coincides within uncertainty limits with the age of the Kurum pluton. Thus, the rocks pertaining to two epochs of magmatic activity, which developed in the South Verkhoyansk Foldbelt and divided by a time span of 25–28 Ma, are documented in the Nezhdaninka ore field. Taking into account that the age of gold mineralization is no less than 120 Ma, the data obtained allow us to specify the previously proposed formation model of the Nezhdaninka deposit. These data give grounds to rule out the Late Cretaceous Kurum pluton and the Gel’dy group of stocks from constituents of the ore-magmatic system, and to suggest that an Early Cretaceous deep-seated magma source existed beneath the deposit. Along with host terrigenous rocks, this magma source participated in the supply of matter to the hydrothermal system. The Nd, Sr, and Pb isotopic systematics of igneous rocks and ore mineralization in the Nezhdaninka ore field show that the Early and Late Cretaceous magma sources were formed in the Precambrian crust dated at ～1.8 Ga.  相似文献   

Holocene history of fire,vegetation and land use from the central Pyrenees (France)     

Damien Rius  Boris Vannière  Didier Galop 《Quaternary Research》2012,77(1):54-64

Located on a mountain pass in the west-central Pyrenees, the Col d'Ech peat bog provides a Holocene fire and vegetation record based upon nine ¹⁴C (AMS) dates. We aim to compare climate-driven versus human-driven fire regimes in terms of frequency, fire episodes distribution, and impact on vegetation. Our results show the mid-Holocene (8500–5500 cal yr BP) to be characterized by high fire frequency linked with drier and warmer conditions. However, fire occurrences appear to have been rather stochastic as underlined by a scattered chronological distribution. Wetter and colder conditions at the mid-to-late Holocene transition (4000–3000 cal yr BP) led to a decrease in fire frequency, probably driven by both climate and a subsequent reduction in human land use. On the contrary, from 3000 cal yr BP, fire frequency seems to be driven by agro-pastoral activities with a very regular distribution of events. During this period fire was used as a prominent agent of landscape management.  相似文献   

U-Pb age of granitoids from the Elenovsk Complex (Kokchetav block, Northern Kazakhstan)     

F. A. Letnikov  A. B. Kotov  A. A. Zayachkovskii  N. G. Rizvanova  E. B. Sal’nikova  Yu. V. Plotkina 《Stratigraphy and Geological Correlation》2012,20(5):417-425

The U-Pb geochronological study of zircons from alkali granitoids of the Elenovsk Complex constituting the Zhilanda and Lesnoi massifs (northern Kazakhstan) located several kilometers away from each other revealed their close ages: 433 ± 2, 440 ± 10, and 426 ± 12 Ma.  相似文献   

Predicting Hysteresis of the Water Retention Curve from Basic Properties of Granular Soils   总被引：1，自引：0，他引：1  

Abdelkabir Maqsoud  Bruno Bussière  Michel Aubertin  Mamert Mbonimpa 《Geotechnical and Geological Engineering》2012,30(5):1147-1159

The water retention curve (WRC), which represents the relationship between volumetric water content (θ) and suction (ψ), is required to analyze the hydro-geotechnical response of unsaturated soils. The laboratory (or field) determination of the WRC can however be time consuming and difficult to conduct. A practical alternative, particularly useful at the preliminary stages of a project, is to estimate the WRC using a predictive model based on basic geotechnical properties that are easy to obtain. One common limitation of such predictive models is due to hysteresis effects, which are not taken into account by most of these models. The authors present in this paper an extended version of the Modified Kovács (MK) predictive model that incorporates hysteresis of the WRC along different paths, including the main wetting and drying curves and the wetting and drying scanning curves for granular soils. The model formulation is presented, and predictions are compared to experimental data obtained on different granular soils. The results show a good agreement for the main and scanning curves.  相似文献   

A first estimation of tsunami hazard of the Pacific coast of Costa Rica from local and distant seismogenic sources     

Chacon-Barrantes  Silvia  Arozarena-Llopis  Isabel 《Ocean Dynamics》2021,71(8):793-810

Ocean Dynamics - Costa Rica has been affected by several local and distant tsunamis in the past, but the historical information is scarce and incomplete. Its Pacific coast stretches for over a...  相似文献   

Late Ediacaran Hyperactivity Period: Quantifying the Reversal Frequency     

Levashova  N. M.  Golovanova  I. V.  Rud’ko  D. V.  Danukalov  K. N.  Rud’ko  S. V.  Sal’manova  R. Yu.  Sergeeva  N. D. 《Izvestiya Physics of the Solid Earth》2021,57(2):247-256

Izvestiya, Physics of the Solid Earth - Abstract—The previous paleomagnetic studies of the Upper Vendian Zigan Formation sediments on the western slope of Southern Ural revealed uncommonly...  相似文献   

On-Orbit Degradation of Solar Instruments     

A. BenMoussa  S. Gissot  U. Schühle  G. Del Zanna  F. Auchère  S. Mekaoui  A. R. Jones  D. Walton  C. J. Eyles  G. Thuillier  D. Seaton  I. E. Dammasch  G. Cessateur  M. Meftah  V. Andretta  D. Berghmans  D. Bewsher  D. Bolsée  L. Bradley  D. S. Brown  P. C. Chamberlin  S. Dewitte  L. V. Didkovsky  M. Dominique  F. G. Eparvier  T. Foujols  D. Gillotay  B. Giordanengo  J. P. Halain  R. A. Hock  A. Irbah  C. Jeppesen  D. L. Judge  M. Kretzschmar  D. R. McMullin  B. Nicula  W. Schmutz  G. Ucker  S. Wieman  D. Woodraska  T. N. Woods 《Solar physics》2013,288(1):389-434

We present the lessons learned about the degradation observed in several space solar missions, based on contributions at the Workshop about On-Orbit Degradation of Solar and Space Weather Instruments that took place at the Solar Terrestrial Centre of Excellence (Royal Observatory of Belgium) in Brussels on 3 May 2012. The aim of this workshop was to open discussions related to the degradation observed in Sun-observing instruments exposed to the effects of the space environment. This article summarizes the various lessons learned and offers recommendations to reduce or correct expected degradation with the goal of increasing the useful lifespan of future and ongoing space missions.  相似文献   

B,V, and DDO photometric observations of red variable stars     

T. Storchi Bergmann  Silvia H. B. Livi  Roberto D. D. Costa 《Astrophysics and Space Science》1984,100(1-2):341-349

Light curves of the red variables L₂ Puppis, R Carinae, and S Carinae in the region of the spectrum covered by theB, V, and DDO photometry are presented. The behavior of the DDO color indices and their meaning for this type of star are discussed. S Carinae shows a different behavior from the other two stars that seems to be due to a population effect.  相似文献   

Magnetic Stratigraphy from Deep Clastic Turbidites: An Example from the Eocene Hecho Group (Southern Pyrenees)     

Oms  Oriol  Dinarès-Turell  Jaume  Remacha  Eduard 《Studia Geophysica et Geodaetica》2003,47(2):275-288

A paleomagnetic study of a 2200-meter thick section of clastic turbidites from the Eocene Hecho group (southcentral Pyrenees, Spain) allows defining its magnetostratigraphic record. Natural remanent magnetization is carried by up to three components: a viscous low-temperature component; a second component unblocked between 300°C and 345°C, likely carried by iron-sulphides; and a third component which demagnetizes at temperatures higher than 345°C and is likely carried by magnetite. The second and third components may display opposite polarities at the same site. The magnetite component delineates different polarity zones and has a more consistent behavior along section if compared with the iron-sulphide component, which displays either a normal or a reverse direction without any stratigraphic consistency along section. The bulk of iron sulphides are interpreted to be secondary in origin and to carry diagenetic overprints acquired at different times after deposition and the magnetite component is taken as the characteristic primary magnetization. As supported by biostratigraphy, the section is correlated from chrons C20r to C18n.2n (Lutetian-Bartonian transition), which indicates a mean sediment accumulation rate of about 52 cm/ky for the studied section. The new chronostratigraphy allows constraining the age of the upper Hecho Group (Banastón and Jaca allogroups) to an unprecedented level and is consistent with previous magnetostratigraphic work in younger sediments from the Jaca Basin. Deep clastic sedimentary systems should not be neglected as a target for magnetostratigraphic studies despite diagenetic growth of secondary minerals may mask the primary signal.  相似文献