南天山川乌鲁碱性杂岩体的岩石学和地球化学特征及其岩石成因   总被引：2，自引：1，他引：1  

黄河  张东阳  张招崇  张舒  李宏波  薛春纪 《岩石学报》2010,26(3):947-962

位于中国南天山西侧阔克萨彦岭一带的川乌鲁碱性杂岩体,与该区川乌鲁铜金多金属矿床有着直接的成因联系,该杂岩体由早期的辉长岩—闪长岩岩、主期的二长岩—正长岩和晚期的正长花岗斑岩脉组成,各期岩石在矿物组成和化学成分上有明显的变化。从早到晚,SiO2含量增加,变化范围是50.52%～70.64%;全碱含量先增后减,在SiO2含量小于61.69%时,随SiO2含量增加而增加,而当SiO2含量大于61.69%时,与SiO2含量负相关。在AR-SiO2图解上,大多样品落入碱性区间,在A/CNK-A/NK图解上表现出由准铝质向过碱性演化的趋势。微量元素表现为大离子亲石元素相对高场强元素富集,Rb、Ba、Th、Sr等元素的相对富集和Nb、Ta、P、Ti等元素的负异常。稀土元素表现为轻稀土相对富集的特征,其(La/Yb)N为14.13～25.09,具有Eu的正异常或极微弱的Eu负异常。一些元素比值的线性关系暗示了该杂岩体为岩浆混合成因,基性岩浆的源区为富水的岩石圈地幔,而酸性岩浆是中下地壳中性火成岩在含饱和水条件下部分熔融的产物。这些性质指示川乌鲁杂岩体是在后碰撞拉张环境中由岩石圈地幔熔融的基性岩浆的底侵作用导致地壳的熔融以及后期的岩浆混合作用有关。  相似文献   

塔里木柯坪地区库普库兹曼组玄武岩锆石LA-ICPMS年代学、Hf同位素特征及其意义   总被引：2，自引：1，他引：1  

张达玉  周涛发  袁峰  范裕  刘帅  杜红星 《岩石学报》2010,26(3):963-974

塔里木盆地广泛发育有二叠纪玄武岩,产于库普库兹曼组和开派兹雷克组中。本文对库普库兹曼组玄武岩进行锆石LA-ICPMSU-Pb精确定年,并首次进行该区玄武岩锆石的铪(Hf)同位素分析。库普库兹曼组底部玄武岩的锆石LA-ICPMSU-Pb加权平均年龄为291.9±2.2Ma(MSWD=0.30,n=17),说明玄武岩为早二叠世岩浆活动产物,该年龄值指示了塔里木大火成岩省二叠纪基性岩浆活动的下限年龄;库普库兹曼组顶部玄武岩获得了293.9±4.6Ma的锆石年龄,与底部锆石年龄在误差范围内基本一致,指示了库普库兹曼组玄武质岩浆活动的时间较为短暂,291.9±2.2Ma可以代表塔里木盆地二叠纪普库兹曼组玄武岩的成岩时代。库普库兹曼组玄武岩中存在大量继承性或捕获的老年龄锆石,指示玄武岩浆在上升过程中与地壳物质发生了混染作用。锆石原位微量、稀土元素分析显示,库普库兹曼组玄武岩锆石具有典型岩浆结晶的基性岩锆石特征,且没有发生明显的后期改造作用。库普库兹曼组玄武岩锆石εHf(t)同位素值在-4.84～-0.65之间,具富集岩石圈地幔源区特征,指示了塔里木大火成岩省二叠纪基性岩浆岩源于富集岩石圈地幔,其地幔源区性质明显不同于新疆北部准噶尔地区同时代A型花岗岩的地幔源区。  相似文献   

鲁西新太古代济宁群含铁岩系形成时代——SHRIMP U-Pb锆石定年   总被引：12，自引：7，他引：5  

王伟  王世进  刘敦一  李培远  董春艳  颉颃强  马铭株  万渝生 《岩石学报》2010,26(4):1175-1181

济宁群以隐伏的地质体分布于华北克拉通鲁西地区,以往被划归古元古代。近年来在济宁群的钻探和地球物理研究中,发现存在较大规模条带状硅铁建造,其形成时代引起地学界极大关注。本文对济宁群变质碎屑沉积岩和长英质火山岩进行了锆石SHRIMP年龄测定。含砾绿泥绢云千枚岩的碎屑锆石年龄主要集中在～2.7Ga,可靠的最年轻碎屑锆石年龄为2.61±0.01Ga。变质长英质火山岩岩浆锆石年龄为2.56±0.02Ga。研究表明,济宁群形成于新太古代晚期,而不是以往认为的古元古代。华北克拉通条带状铁建造主要形成于新太古代晚期。济宁群在岩石组合、变质作用方面与鞍山、冀东以及五台地区同时代含硅铁建造的表壳岩系有差别,但是与本溪南芬铁矿的岩石组合有相似之处。这些可能为我国的隐伏太古宙BIF铁矿的研究与勘探提供了重要依据。  相似文献   

满洲里南部白音高老组流纹岩锆石U-Pb定年及岩石成因   总被引：12，自引：3，他引：9  

苟军  孙德有  赵忠华  任云生  张学元  付长亮  王晰  魏红艳 《岩石学报》2010,26(1):333-344

满洲里南部白音高老组火山岩主要由流纹岩组成,含少量珍珠岩和流纹质凝灰岩。LA-ICPMS锆石U-Pb定年结果显示,流纹岩形成于141~139Ma的早白垩世早期。岩石地球化学研究表明,火山岩具有高硅富碱、贫钙镁和高FeO^T/MgO比值的特征; 稀土丰度总量较高(∑REE介于103×10^-6~488×10^-6),轻重稀土分馏明显［(La/ Yb)_N=4.12~30.94)］,Eu负异常显著(δEu=0.12~0.46); 微量元素以富集Rb、Th、U、K,强烈亏损Ba、Sr、P、Ti,中等亏损Nb、Ta和高Ga/Al值为特征,与A-型花岗岩特征相似。锆石¹⁷⁶Hf/¹⁷⁷Hf比值介于0.282785~0.282970之间,ε_Hf(t)值均为正值,介于3.78~9.98之间。流纹岩岩浆来源于斜长石稳定区玄武质下地壳物质的部分熔融,形成于非造山板内伸展构造环境。  相似文献   

Horizontal variability and boundary-layer modeling     

Sumner Barr  Carl W. Kreitzberg 《Boundary-Layer Meteorology》1975,8(2):163-172

Micrometeorologists have traditionally set aside consideration of horizontal variability and have studied boundary-layer structure with horizontal homogeneity. The numerical forecasting of boundary-layer structures, over normally varying terrain and including normal disturbances such as fronts, requires selection of an appropriate horizontal scale.A simple analysis of steady-state balance between horizontal advection and vertical diffusion provides estimates of the vertical scale (or depth) of surface-induced features. The scale height is a function of the horizontal scale of the variations. Models neglecting important terrain scales of length below ~ 1000 km can predict down to levels of ~ 0.5 to 1 km while those that neglect important terrain scales below ~ 100 km can predict down to ~ 0.2 to 0.6 km. Below these levels, any predicted features will be dominated by the vertical diffusion so that they are solutions of a one-dimensional boundary-value problem.The boundary-induced advection effects dominate free atmosphere advection effects in the lowest few hundred meters as well. This means that if mesoscale advections are resolved and terrain influences are strong, the predictions in the layer ~ 0.2 to 0.8 km can provide mesoscale detail without mesoscale initial conditions above the surface, because the surface forcing will dominate the solution.  相似文献   

Geomorphic and Climatic Implications of Relict Openwork Block Accumulations Near Thabana-Ntlenyana, Lesotho     

P.D. Sumner 《Geografiska Annaler: Series A, Physical Geography》2004,86(3):289-302

Conflicting reports appear in the literature from geomorphic studies describing the colder Late Pleistocene environmental conditions of the Lesotho Highlands in southern Africa. Evidence is given for limited glaciation and/or periglacial conditions, with or without permafrost. An investigation of the distribution, morphometric attributes and surface weathering characteristics of relict openwork block accumulations in the area around Thabana‐Ntlenyana, the highest summit in the range, supports the contention for a relatively arid periglacial environment during the Last Glacial period. A phase of enhanced block production is evident from the concentration of blocks in the upper layer of colluvium. Slope mobility on south‐facing slopes is shown in the blockfield fabrics and the increase in downslope relative age of block surfaces. Block production and slope creep are attributed to depressed temperature conditions and seasonal freeze. Colluvium, within which blocks have been incorporated and superimposed, indicates that slope mantles predate the onset of the colder period and evidence militates against either deep snow cover or localised glaciation of south‐facing slopes.  相似文献   

Near- and mid-infrared colours of star-forming galaxies in European Large Area ISO Survey fields     

P. Väisänen  T. Morel  M. Rowan-Robinson  S. Serjeant  S. Oliver  T. Sumner  H. Crockett  C. Gruppioni  E. V. Tollestrup 《Monthly notices of the Royal Astronomical Society》2002,337(3):1043-1058

  相似文献   

Study and suppression of anomalous fast events in inorganic scintillators for dark matter searches     

V. A. Kudryavtsev  N. J. C. Spooner  P. K. Lightfoot  J. W. Roberts  M. J. Lehner  T. Gamble  M. J. Carson  T. B. Lawson  R. Lüscher  J. E. McMillan  B. Morgan  S. M. Paling  M. Robinson  D. R. Tovey  N. J. T. Smith  P. F. Smith  G. J. Alner  S. P. Hart  J. D. Lewin  R. M. Preece  T. J. Sumner  W. G. Jones  J. J. Quenby  B. Ahmed  A. Bewick  D. Davidge  J. V. Dawson  A. S. Howard  I. Ivaniouchenkov  M. K. Joshi  V. Lebedenko  I. Liubarsky  J. C. Barton  G. Gerbier  J. Mallet  L. Mosca  C. Tao 《Astroparticle Physics》2002,17(4):79-408

The status of dark matter searches with inorganic scintillator detectors at Boulby mine is reviewed and the results of tests with a CsI(Tl) crystal are presented. The objectives of the latter experiment were to study anomalous fast events previously observed and to identify ways to remove this background. Clear indications were found that these events were due to surface contamination of crystals by alphas, probably from radon decay. A new array of unencapsulated NaI(Tl) crystals immersed either in liquid paraffin or pure nitrogen atmosphere is under construction at Boulby. Such an approach allows complete control of the surface of the crystals and the ability to remove any surface contamination. First data from the unencapsulated NaI(Tl) do not show the presence of anomalous fast events.  相似文献   

Late Miocene to Pliocene stratigraphy of the Kura Basin,a subbasin of the South Caspian Basin: implications for the diachroneity of stage boundaries          下载免费PDF全文

Adam M. Forte  Dawn Y. Sumner  Eric Cowgill  Marius Stoica  Ibrahim Murtuzayev  Talat Kangarli  Mikheil Elashvili  Tea Godoladze  Zurab Javakhishvili 《Basin Research》2015,27(3):247-271

Relative ages of late Cenozoic stratigraphy throughout the Caspian region are referenced to regional stages that are defined by changes in microfauna and associated extreme (>1000 m) variations in Caspian base level. However, the absolute ages of these stage boundaries may be significantly diachronous because many are based on the first occurrence of either transgressive or regressive facies, the temporal occurrence of which should depend on position within a basin. Here, we estimate the degree of diachroneity along the Akchagyl regional stage boundary within the Caspian basin system by presenting two late Miocene‐Pliocene aged measured sections, Sarica and Vashlovani, separated by 50 km and exposed within the Kura fold‐thrust belt in the interior of the Kura Basin. The Kura Basin is a western subbasin of the South Caspian Basin and the sections presented here are located >250 km from the modern Caspian coast. New U‐Pb detrital zircon ages from the Sarica section constrain the maximum depositional age for Productive Series strata, a lithostratigraphic package considered correlative with the 2–3 Myr‐long regional Eoakchagylian or Kimmerian stage that corresponds to a period of extremely low (>500 m below the modern level) Caspian base level. This new maximum depositional age from the Productive Series at Sarica of 2.5 ± 0.2 Ma indicates that the regionally extensive Akchagyl transgression, which ended the deposition of the Productive Series near the Caspian coast at 3.2 Ma, may have appeared a minimum of 0.5 Myr later in the northern interior of the Kura Basin than at the modern Caspian Sea coast. The results of this work have important implications for the tectonic and stratigraphic history of the region, suggesting that the initiation of the Plio‐Pleistocene Kura fold‐thrust belt may have not been as diachronous along strike as previously hypothesized. More generally, these results also provide a measure of the magnitude of diachroneity possible along sequence boundaries, particularly in isolated basins. Comparison of accumulation rates between units in the interior of the Kura subbasin and the South Caspian main basin suggest that extremely large variations in these rates within low‐stand deposits may be important in identifying the presence of subbasins in older stratigraphic packages.  相似文献   

Radioactivity backgrounds in ZEPLIN-III     

H.M. Araújo  D.Yu. AkimovE.J. Barnes  V.A. BelovA. Bewick  A.A. BurenkovV. Chepel  A. CurrieL. DeViveiros  B. EdwardsC. Ghag  A. HollingsworthM. Horn  G.E. KalmusA.S. Kobyakin  A.G. KovalenkoV.N. Lebedenko  A. Lindote  M.I. LopesR. Lüscher  P. MajewskiA. St. J. Murphy  F. Neves  S.M. PalingJ. Pinto da Cunha  R. PreeceJ.J. Quenby  L. ReichhartP.R. Scovell  C. SilvaV.N. Solovov  N.J.T. SmithP.F. Smith  V.N. StekhanovT.J. Sumner  C. ThorneR.J. Walker 《Astroparticle Physics》2012,35(8):495-502

We examine electron and nuclear recoil backgrounds from radioactivity in the ZEPLIN-III dark matter experiment at Boulby. The rate of low-energy electron recoils in the liquid xenon WIMP target is 0.75 ± 0.05 events/kg/day/keV, which represents a 20-fold improvement over the rate observed during the first science run. Energy and spatial distributions agree with those predicted by component-level Monte Carlo simulations propagating the effects of the radiological contamination measured for materials employed in the experiment. Neutron elastic scattering is predicted to yield 3.05 ± 0.5 nuclear recoils with energy 5-50 keV per year, which translates to an expectation of 0.4 events in a 1 yr dataset in anti-coincidence with the veto detector for realistic signal acceptance. Less obvious background sources are discussed, especially in the context of future experiments. These include contamination of scintillation pulses with Cherenkov light from Compton electrons and from β activity internal to photomultipliers, which can increase the size and lower the apparent time constant of the scintillation response. Another challenge is posed by multiple-scatter γ-rays with one or more vertices in regions that yield no ionisation. If the discrimination power achieved in the first run can be replicated, ZEPLIN-III should reach a sensitivity of ∼1 × 10⁻⁸pb · yr to the scalar WIMP-nucleon elastic cross-section, as originally conceived.  相似文献