Intrinsic intraday variability in the gravitational lens system B0218+357     

A. D. Biggs  I. W. A. Browne  P. N. Wilkinson 《Monthly notices of the Royal Astronomical Society》2001,323(4):995-998

Radio monitoring of the gravitational lens system B0218+357 reveals it to be a highly variable source with variations on time-scales of a few days correlated in both images. This shows that the variability is intrinsic to the background lensed source and suggests that similar variations in other intraday variable sources can also be intrinsic in origin.  相似文献   

The spectral energy distributions of the revised 200-mJy sample     

S. Antón  I. W. A. Browne  M. J. M. Marchã  M. Bondi  A. Polatidis 《Monthly notices of the Royal Astronomical Society》2004,352(2):673-688

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The recognition of blazars and the blazar spectral sequence     

S. Antón  I. W. A. Browne 《Monthly notices of the Royal Astronomical Society》2005,356(1):225-231

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华北克拉通奥陶纪岩浆活动——来自河南安阳岭头地区白垩纪闪长岩中继承锆石U- Pb年龄的证据     

杨长青  巴燕  王艳慧  何凯  白国典 《地质论评》2023,69(3):1150-1160

通过高精度的LA-ICP-MS锆石U-Pb同位素测年,在太行山南段河南安阳县岭头一带白垩纪闪长质侵入岩中获得一批443.6±6.1 Ma(MSWD=6.3)的年龄数据,相当于晚奥陶世晚期,这是在华北克拉通内部发现的首例反映加里东期岩浆侵入活动的高精度锆石U-Pb定年数据,为揭示华北克拉通早古生代构造岩浆演化提供了依据。结合区域上同期构造岩浆事件的特点,认为443.6±6.1Ma的锆石可能为华北克拉通板内裂解拉张作用的产物,它是奥陶纪晚期(440 Ma前后)古劳亚大陆分裂,华北克拉通漂离加拿大地盾和北美内陆地台,同时形成北太平洋——这一影响全球的构造地质事件在华北克拉通内部的响应。鉴于稳定克拉通地区奥陶纪岩浆侵入活动与金刚石原生矿存在极高的关联度,本次发现也为在鹤壁地区寻找金刚石原生矿提供了重要参考。  相似文献   

西藏厅宫斑岩铜矿床地质、蚀变及矿化特征研究     

杜等虎  杨志明  刘云飞  曲焕春  李秋耘  许博  巴登珠 《岩石矿物学杂志》2015,34(4):447-474

本文对西藏厅宫大型铜矿进行了详细研究,矿床详细的地质岩相学-蚀变以及典型剖面填图表明,矿区存在2个岩浆事件高峰,即始新世的钾长花岗岩(~50 Ma)和中新世的斑状二长花岗岩、英云闪长斑岩及闪长玢岩(约13~17 Ma)。野外和室内研究发现,厅宫矿区存在2期重要的矿化事件,即始新世(~50 Ma)铜矿化及中新世(~15Ma)的铜钼矿化。始新世含矿岩体为钾长花岗岩,其最主要的特点是其成矿岩体结构的特殊性,表现在该矿床的成矿岩体没有典型的斑状结构,而是独特的细晶-似伟晶结构,说明含矿岩浆发生过骤冷,可能是流体突然逃逸,矿物结晶的固相点发生漂移所致。同时,该岩体还发育大量显微文象结构、显微晶洞构造等,均说明岩浆曾经富水,并且曾经流体饱和;中新世含矿岩体为具有埃达克岩特征的斑状二长花岗岩,主要以脉状的铜、钼矿化为主。该矿床蚀变分带类似于冈底斯带其他斑岩矿床。时间上,分别为早期的钾硅酸盐化、转换阶段的青磐岩化、随后的绢英岩化及最晚期的泥化蚀变;空间上,以含矿岩体为中心向外依次为钾硅酸盐化、绢英岩化、青磐岩化,最晚期的泥化呈补丁状或条带状叠加早期各类蚀变。铜矿化主要发生在始新世的黑云母化阶段和中新世的绢英岩化阶段,而钼矿化主要发生在中新世的钾硅酸盐化和绢英岩化的转换阶段。  相似文献   

Diamond Discovered in Dangqiong Ophiolite, Western Yarlung-Zangbu Suture Zone, Tibet     

XIONG Fahui  YANG Jingsui  Robinson T.PAUL  XU Xiangzhen  BA Dengzhu  LI Yuan  LIJinyang  ZHANG Zhongming  RONG He 《《地质学报》英文版》2015,89(Z2):99-100

<正>The first diamonds from ophiolite were found in peridotite of Luobusa ophiolite along Yarlung Zangbu suture zone in Tibet,China(IGCAGS,1981),and then more and more diamonds found in harzgurgite(Bai et al.,1993;Yang et al.,2007a;Robinson et al.,2014;Xu et al.,  相似文献   

Evaluation of the relative roles of global versus local sedimentary controls on Middle to Late Pleistocene formation of continental margin strata,Canterbury Basin,New Zealand          下载免费PDF全文

Tania Villaseñor  John M. Jaeger  Kathleen M. Marsaglia  Greg H. Browne 《Sedimentology》2015,62(4):1118-1148

Determining the relative influence of eustasy versus local sedimentary processes on strata formation is a fundamental challenge in the study of continental margin stratigraphy. In this paper, the relative contribution of these factors on continental margin evolution during the Middle to Late Pleistocene is evaluated using samples from Integrated Ocean Drilling Program Expedition 317. Core‐logging, biostratigraphy and quantitative X‐ray diffraction mineralogy are used to delineate continental shelf sedimentary systems. Major lithological unconformities bound stratigraphic sequences that contain recurring compositional patterns and that resemble other examples of Middle to Upper Pleistocene sequences. However, a preliminary chronology suggests that sequence boundary formation cannot be linked ‘one to one’ with eustatic cycles and therefore these sequences can contain multiple ca 100 ka eustatic cycles. Smaller amplitude, higher frequency transitions in sediment composition are interpreted as stratigraphic sequences driven by more rapid perturbations in the interplay of accommodation and sediment supply; their stratigraphy is variable in time and across the shelf, suggesting a strong influence of local sedimentary forcing in their formation. Changes in sediment composition after the Middle Pleistocene Transition indicate that sediment transfer from onshore sources in the glaciated Southern Alps to the middle‐shelf occurred over a single 100 ka glacio‐eustatic cycle, with an additional 100 ka lag before the mineralogical signal was preserved on the outer‐shelf. This phenomenon is coincident with rapid shelf progradation in this basin, suggesting a causal relation between across‐shelf sediment transport and margin progradation. This is one of very few studies that provide insights at the core scale into the processes driving continental margin evolution during the Middle to Late Pleistocene. This work shows that compositional changes in mud‐dominated successions can lead to a sequence stratigraphic interpretation and the identification of high‐frequency sequences, which may not be possible using a conventional stratigraphic approach.  相似文献   

Vorticity and astrophysical magnetism     

P. F. Browne 《Astrophysics and Space Science》1982,87(1-2):407-423

Viscous resistance to differential rotation causes a current whose magnetic field is proportional to the vorticity of the medium. The magnetic fields of stars and galaxies could arise in this manner, provided that the time scale for development of the field is reasonable. The latter condition (assuming Ohmic rather than synchroton dissipation) requires that the scale length for a galactic field be less than 3×10¹³ cm. It is suggested that there may be continual generation of field within the core of a vortex of this dimension in the galactic nucleus, the field lines then being carried outwards by expanding plasma. The main observational evidence in connection with solar, stellar and galactic magnetic fields is appraised in the context of the above theory.  相似文献   

The ECOMAN project: A novel approach to defining sustainable ecosystem function     

Galloway TS  Brown RJ  Browne MA  Dissanayake A  Lowe D  Depledge MH  Jones MB 《Marine pollution bulletin》2006,53(1-4):186-194

The ECOMAN was initiated in 2001 by the University of Plymouth, UK, Plymouth Marine Laboratory and the Department of the Environment, Fisheries and Rural Affairs (DEFRA) to address the need for more pragmatic assessment techniques linking environmental degradation with its causes. The primary aim of the project was to develop an evidence-based approach in which suites of easy-to-use, cost-effective and environmentally valid biological responses (biomarkers) could be used together to assess the health of coastal systems through the general condition of individuals. A range of sub-lethal endpoints, chosen to reflect successive levels of biological organisation (molecular, cellular, physiological), was evaluated in common coastal organisms showing different feeding types (filter feeding, grazing, predation) and habitat requirements (estuary, rocky shore). Initially, the suite of biomarkers was used in laboratory studies to determine the relative sensitivities of key species within different functional groups to common contaminants. These results were then validated in field studies performed in a range of ecosystems exhibiting different degrees/signatures of contamination. Here, an example is provided of a field study in the Humber Estuary, UK, which illustrates how multivariate statistical analysis can be used to identify patterns of response to discriminate between contaminated and clean sites. The use of a holistic, integrated approach of this kind is advocated as a practical means of assessing the impact of chemical contamination on organismal health and of ranking the status of marine ecosystems.  相似文献   

Radio and optical orientations of galaxies     

R. A. Battye  I. W. A. Browne 《Monthly notices of the Royal Astronomical Society》2009,399(4):1888-1900

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