Metal deposits in relation to plate tectonics: F.J. Sawkins. Springer Publisher, 325 pp., DM 98, US$ 38.10, ISBN 3-540-12752-6.     

C.J. Allegre 《Physics of the Earth and Planetary Interiors》1985,37(4):288-289

  相似文献   

Evidence for contamination of recent Hawaiian lavas from²³⁰Th-²³⁸U data     

M. Condomines  M. Bernat  C.J. Allegre 《Earth and Planetary Science Letters》1976,33(1):122-125

²³⁰Th-²³⁸U radioactive disequilibrium was studied in the historical lava flows of the Mauna Loa and Kilauea, Hawaii. Large variations of the (²³⁰Th/²³²Th) ratio among lavas of the same volcano that were erupted at a few years' interval are interpreted as due to contamination. The contamination probably occurs by assimilation of zeolitic minerals formed by seawater interaction while the magma resides in a superficial chamber.  相似文献   

Fine chronology of volcanic processes using ²³⁸U-²³⁰Th systematics     

Claude J. Allegre  Michel Condomines 《Earth and Planetary Science Letters》1976,28(3):395-406

The²³⁰Th-²³⁸U radioactive disequilibrium method was applied to the study of recent volcanic rocks from Costa Rica. Most samples are from the Irazu volcano. Some samples were dated by internal isochrons using the (²³⁰Th/²³²Th)-(²³⁸U/²³²Th) diagram, others were studied only by whole rock analyses. The evolution of the parent magma may be followed by the initial (²³⁰Th/²³²Th)₀ ratios of the rocks. A model involving a differentiating magma chamber that existed for 140,000 years under the Irazu volcano correlates well with the observations. Other volcanoes seem to be in earlier stages of their evolution. Continuing study may help to solve the tholeiitic to andesitic volcanism relationship.  相似文献   

“Ages”Rb-Sr du sol et des fragments rocheux ramenes des montagnes lunaires par la sonde automatique Luna 20, (region du cratere Apollonius)     

Jean-Louis BirckClaude J. Allegre 《Earth and Planetary Science Letters》1972

⁸⁷Rb-⁸⁷Sr results are reported for soil and fragments from Luna 20 mission. The results show a low radiogenic character but demonstrate clearly the presence of the high K components. A model is presented for lunar evolution.  相似文献   

Etude systématique des isotopes de l'oxygène,du carbone et du strontium dans les carbonatites     

Françoise Pineau  Marc Javoy  Claude J Allegre 《Geochimica et cosmochimica acta》1973,37(11):2363-2377

${}^{18}\text{O}{}^{16}\text{O}$, ${}^{13}\text{C}{}^{12}\text{C}$ and ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios have been measured on the same samples for carbonatite complexes. The results show that besides the ‘carbonatite box’ of Tayloret al. (1967) there exist higher δ¹⁸O and δ¹³C values than can be explained by late magmatic or deuteric processes. These processes correspond to high concentrations of CO₂ and lead to big enrichments in ¹⁸O and ¹³C as well as in some ‘volatile’ elements. Strontium results are consistent with a model of selective contamination of deep-seated material by highly radiogenic strontium. The whole study leads to the opinion that parent magmas of carbonatites differentiated in a crustal environment with or without significant contamination.  相似文献   

Behavior of the rare earth elements in the Oklo natural reactor     

Michel Loubet  C.J Allegre 《Geochimica et cosmochimica acta》1977,41(11):1539-1548

A systematic analysis of the abundance and isotopic composition of ten REE (and Ba) in a sample from the reactor zone at the Oklo (Gabon) ore deposit is presented. From this analysis some constraints on the behavior of the REE group during and after the reaction time are determined. Taking into account the complex state of this sample, the main characteristics of the reactor are deduced.From the abundances of isotopes with large neutron capture cross sections the amount of REE (supposed to be natural) added after the reaction time is calculated first. The comparison of the fluence values obtained respectively from the analysis of the Nd and Dy isotopic spectrum indicates a rather good stability of the REE group during the reaction time. The total number (²³⁵U)_f of ²³⁵U nuclei that fissioned during the reaction calculated from different elements of the REE group provides an indication on the relative migration of these elements since the reaction time. Results of these computations suggest a migration of the heavy REE relative to the light REE to outside the reaction zone. As a consequence of these deductions on the behavior of the REE in the Oklo ore, the light REE appear the most appropriate to study the characteristics of the reactor. The reactor characteristics we deduced from this sample (fluence, epithermal index, proportion of nuclides that fissioned, duration of the reactor) are within the range of the ones determined in other studies dealing with REE analysis.  相似文献   

⁸⁷Rb–⁸⁷Sr history of the Norton County enstatite achondrite     

J.F. Minster  C.J. Allegre 《Earth and Planetary Science Letters》1976,32(2):191-198

⁸⁷Rb⁸⁷Sr analysis of the Norton County achondrite has been achieved with special attention to the rubidium analysis. Enstatite crystals and polycrystalline material give an “age” of 4.48 ± 0.04 × 10⁹ years and an initial ratio ⁸⁷Sr/⁸⁶Sr_I= 0.7005 ± 0.0004 (λ = 1.39 × 10^?11yr^?1, maximum errors). The feldspar component of the meteorite contains about 70% of the strontium and 30% of the rubidium of the whole sample, and does not lie on the isochron. Its model age relative to the strontium initial ratio of Allende is 4.6 × 10⁹ years. The data are consistent with a complex history dealing with an incomplete isotopic reequilibration of the meteorite, 120 m.y. after its formation at 4.6 × 10⁹ years, with an initial ratio similar to that of Allende.  相似文献   

Origin of carbonatitic magma in the light of the Pb-U-Th isotope system     

Joel R. Lancelot  Claude J. Allegre 《Earth and Planetary Science Letters》1974,22(3):233-238

  相似文献   

When plenty is not enough: an assessment of the white stumpnose (Rhabdosargus globiceps) fishery of Saldanha Bay,South Africa     

D Parker  SE Kerwath  TF Næsje  CJ Arendse  FJ Keulder-Stenevik  K Hutchings 《African Journal of Marine Science》2017,39(2):153-166

White stumpnose Rhabdosargus globiceps is the main target of the linefishery in Saldanha Bay. Increased fishing pressure over the last three decades, particularly by the recreational sector, has led to concerns regarding sustainability of the local white stumpnose stock. The fishery was exceptionally productive between 2006 and 2008, with an estimated annual catch of 141.2 tonnes (t). Only 3% of boat outings surveyed were commercial boats targeting white stumpnose, yet this sector accounted for 39.3 t (31%) of the average annual catch. The recreational boat sector accounted for most of the catch (70.0 t), and the recreational shore sector the least (31.9 t). Commercial boat catch per unit effort (CPUE; 3.7 fish angler^–1 h^–1) was more than 10 times that of recreational boats (0.3 fish angler^–1 h^–1). White stumpnose catch length-frequency differed significantly (p < 0.01) between the fishing sectors, with the commercial sector retaining larger fish (34.7 cm [SD 5.9]) than the recreational boat (33.9 cm [SD 5.9]) and shore (30.4 cm [SD 5.8]) sectors. A decline in commercial CPUE (2000–2015) of approximately 40% and a concomitant severe decline (>95%) in survey data for juvenile white stumpnose CPUE (2007–2016) indicate that the current rate of exploitation is not sustainable. Recovery of the white stumpnose stock will require a decrease in fishing mortality. Possible management regulations include sector-specific effort limitations, extending the ‘no take’ marine protected area, reducing the recreational-sector bag limit to 5 fish person^–1 day^–1, implementing a commercial-sector bag limit, and increasing the minimum size limit to 30 cm TL.  相似文献   

徐家围子断陷构造地质特征研究新进展   总被引：14，自引：1，他引：13  

张元高  陈树民  张尔华  姜传金 《岩石学报》2010,26(1):142-148

在徐家围子断陷深层连片三维地震精细解释的基础上,结合前人的研究成果,系统的刻画了深大断裂的性质、产状和时空分布规律。从区域构造应力场着手,详细剖析了徐家围子断陷的构造地质特征,重新构建了深大断裂体系。依据剖面特征和断陷的地质结构,首次在徐家围子断陷内解释出两条深大走滑断裂带,发现深大走滑断裂控制了营城组火山岩的形成和分布。明确了徐家围子断陷"两凹夹一隆、东西分带、南北分块"构造格局的动态演化过程及其控制因素。详细剖析了断陷期地层的沉积发育过程、后期改造过程以及现今赋存特征。为庆深气田火山岩储层分布规律预测奠定了基础。  相似文献