赣南地区石雷石英闪长岩的成因:岩石化学、副矿物微量元素、锆石U-Pb年代学与Sr-Nd-Hf同位素制约

石雷石英闪长岩是赣南崇-余-犹地区比较特殊的闪长质侵入体。锆石的原位U-Pb定年表明,该岩体侵位于433.5±3.4Ma。全岩主量元素特征上显示出中偏酸性(SiO2=56.92%～64.70%),富Al(Al2O3=14.10%～14.83%),富碱(Alk=6.41%～7.40%)特别是富钾(K2O=3.86%～4.85%),镁、铁含量较高,MgO:3.47%～5.95%,FeOT:5.23%～8.14%以及低磷(P2O5=0.27%～0.4%)的特点;微量元素上主要富集K、Rb、Cs等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ti、P等高场强元素。磷灰石微量元素特征上显示高度富集稀土元素特别是轻稀土元素的特征;具有Eu的负异常(δEu=0.37～0.45)。ISr位于0.7073～0.7132之间,εNd(t)变化于-8.41～-4.97之间,两阶段钕模式年龄介于1.58～1.86Ga之间,Hf同位素组成相对均一,εHf(t)主要集中变化于-8～-2之间,两阶段Hf模式年龄加权平均为1.77±0.09Ga,这些特征都暗示了该石英闪长质岩体的形成是强烈壳幔相互作用的产物,区内加里东晚期可能发生了局部的岩石圈的减薄。     

Search for H2 Emission from Disks around T Tauri and Herbig AE Stars

Preliminary results are presented of observations of the pure rotational lines of H2 toward T Tauri and Herbig Ae stars using the Short Wavelength Spectrometer (SWS) on the Infrared Space Observatory (ISO). The sources are selected to be isolated low- and intermediate-mass young stellar objects, for which the presence of a circumstellar disk has been established by millimeter interferometry. The lowest H2 S(0) and S(1) lines are detected in 3 out of 5 objects. The measured intensities indicate ∼ 0.01 M⊙ of warm (T ≈ 150 K) gas in the ISO beam. It is argued that for at least one case (HD 163296), the emission is probably dominated by the warm gas in the circumstellar disk rather than by shocked- or photon-heated gas in the surrounding envelope. Such observations can provide important constraints on the radial and vertical temperature profiles in circumstellar disks. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determining the Oxygen Isotope Composition of Evapotranspiration Using Eddy Covariance

Impacts of different terrain configurations on the general behaviour of idealised katabatic flows are investigated in a numerical model study. Various simplified terrain models are applied to unveil modifications of the dynamics of nocturnal cold drainage of air as a result of predefined topographical structures. The generated idealised terrain models encompass all major topographical elements of an area in the tropical eastern Andes of southern Ecuador and northern Peru, and the adjacent Amazon. The idealised simulations corroborate that (i) katabatic flows develop over topographical elements (slopes and valleys), that (ii) confluence of katabatic flows in a lowland basin with a concave terrainline occur, and (iii) a complex drainage flow system regime directed into such a basin can sustain the confluence despite varying slope angles and slope distances.     

Dust Around Solar Mass Stars

The DEBRIS project is a search for infrared excess around Sun-like main sequence stars, and other types of stellar targets, using the Infrared Space Observatory. Some results, calibration issues, and changes to our original program are presented. Future platforms for advancing this project after the conclusion of the ISO mission are indicated. This revised version was published online in August 2006 with corrections to the Cover Date.     

The detection and study of pre-planetary disks

A variety of evidence suggests that at least 50% of low-mass stars are surrounded by disks of the gas and dust similar to the nebula that surrounded the Sun before the formation of the planets. The properties of these disks may bear strongly on the way in which planetary systems form and evolve. As a result of major instrumental developments over the last decade, it is now possible to detect and study the circumstellar environments of very young, solar-type stars in some detail, and to compare the results with theoretical models of the early solar system. For example, millimeter-wave aperture synthesis imaging provides a direct means of studying in detail the morphology, temperature and density distributions, velocity field and chemical constituents in the outer disks, while high resolution, near infrared spectroscopy probes the inner, warmer parts; the emergence of gaps in the disks, possibly reflecting the formation of planets, may be reflected in the variation of their dust continuum emission with wavelength. We review progress to date and discuss likely directions for future research.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.     

敦煌造山带南部红柳峡混杂带基质的沉积学、地球化学和年代学特征及其大地构造意义

敦煌造山带南部红柳峡混杂带基质的研究,为认识敦煌造山带的形成和演化提供了新的依据。本文从沉积学、地球化学和年代学等方面系统讨论了该混杂带基质的特征和形成环境。结果显示,基质的岩石类型主要包括变泥质岩(云母石英片岩)和变质砂岩,普遍发生强烈变形。局部弱变形变质的基质仍保留有原生沉积构造(如T_(ab)、T_(de)、T_(bde)组合的鲍马序列),反映原岩是一套浊积岩复理石。显微岩相学特征显示,基质碎屑组分以长石、石英和岩屑为主,长石和岩屑含量较高,分别为47%和27%,反映大量火成岩物质的加入,且碎屑颗粒的分选性和磨圆度较差,说明搬运距离较近。地球化学方面,低的化学蚀变指数(CIA=49~67),反映复理石基质物源区母岩经历的风化程度较低。高的成分变化指数(ICV0.8)以及Zr/Sc-Th/Sc投图结果显示,沉积物再循环程度低,为近物源区的初次沉积。基质Sc、Cr、Co、Ni含量低,Eu/Eu*、La/Sc、Th/Sc、La/Co、Th/Co和Cr/Th等元素比值类似于来自长英质源区的沉积物,暗示其物源区母岩以中-酸性岩石为主。La/Sc-Ti/Zr和Th-ScZr/10投图结果显示,复理石基质形成于陆缘弧或活动大陆边缘构造背景。弱变形浅变质砂岩的碎屑模式表明,基质的物源来自"切割型弧-过渡型弧"源区。综上,红柳峡混杂带基质在碎屑组成方面,以再循环程度低、近物源堆积的"切割型弧-过渡型弧"源区长英质碎屑组分为主,在沉积构造方面,发育鲍马序列和深水块体搬运沉积(MTD)构造,表明基质形成于陆缘弧或活动大陆边缘的俯冲带海沟环境。碎屑锆石年代学显示三组年龄:2300Ma、1850Ma和423Ma,结合区域地质背景分析,初步认为物源碎屑可能来自混杂带北侧的三危山弧和东巴兔-蘑菇台弧的古生代花岗岩类以及俯冲折返的变质基性岩岩块。复理石基质的变质砂岩中获得的最年轻的岩浆碎屑锆石年龄为389Ma,说明该砂岩形成于中泥盆世之后,暗示敦煌造山带南部红柳峡地区洋盆尚未俯冲完毕,碰撞作用尚未开始。     

Radiocarbon analysis of halophilic microbial lipids from an Australian salt lake

Assigning accurate dates to hypersaline sediments opens important terrestrial records of local and regional paleoecologies and paleoclimatology. However, as of yet no conventional method of dating hypersaline systems has been widely adopted. Biomarker, mineralogical, and radiocarbon analyses of sediments and organic extracts from a shallow (13 cm) core from a hypersaline playa, Lake Tyrrell, southeastern Australia, produce a coherent age-depth curve beginning with modern microbial mats and extending to ~ 7500 cal yr BP. These analyses are furthermore used to identify and constrain the timing of the most recent change in hydrological regime at Lake Tyrrell, a shift from a clay deposit to the precipitation of evaporitic sands occurring at some time between ~ 4500 and 7000 yr. These analyses show the potential for widespread dating of hypersaline systems integrating the biomarker approach, reinforce the value of the radiocarbon content of biomarkers in understanding the flow of carbon in modern ecologies, and validate the temporal dimension of data provided by biomarkers when dating late Quaternary sediments.     

REE and Sr isotope characteristics of carbonate within the Cu–Co mineralized sedimentary sequence of the Nchanga Mine,Zambian Copperbelt

Carbonate, largely in the form of dolomite, is found throughout the host rocks and ores of the Nchanga mine of the Zambian Copperbelt. Dolomite samples from the hanging wall of the mineralization show low concentrations of rare-earth elements (REE) and roof-shaped, upward convex, shale-normalized REE patterns, with positive Eu*_SN anomalies (1.54 and 1.39) and marginally negative Ce anomalies (Ce*_SN 0.98,0.93). In contrast, dolomite samples associated with copper and cobalt mineralization show a significant rotation of the REE profile, with HREE enrichment, and La/Lu_SN ratios <1 (0.06–0.42). These samples also tend to show variable but predominantly negative Eu*_SN and positive cerium anomalies and an upwardly concave MREE distribution (Gd-Er). Malachite samples from the Lower Orebody show roof-tile-normalized REE patterns with negative europium anomalies (Eu*_SN 0.65–0.80) and negative cerium anomalies (Ce*_SN 0.86–0.9). The carbonate ⁸⁷Sr/⁸⁶Sr signature correlates with the associated REE values. The uppermost dolomite samples show Neoproterozoic seawater-like ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7111 to 0.7116, whereas carbonate from Cu–Co mineralized samples show relatively low concentrations of strontium and more radiogenic ⁸⁷Sr/⁸⁶Sr, ranging between 0.7136–0.7469. The malachite samples show low concentrations of strontium, but give a highly radiogenic ⁸⁷Sr/⁸⁶Sr of 0.7735, the most radiogenic ⁸⁷Sr/⁸⁶Sr ratio. These new data suggest that the origin and timing of carbonate precipitation at Nchanga is reflected in the REE and Sr isotope chemistry. The upper dolomite samples show a modified, but essentially seawater-like signature, whereas the rotation of the REE profile, the MREE enrichment, the development of a negative Eu*_SN anomaly and more radiogenic ⁸⁷Sr/⁸⁶Sr suggests the dolomite in the Cu–Co mineralized samples precipitated from basinal brines which had undergone significant fluid–rock interaction. Petrographic, REE, and ⁸⁷Sr/⁸⁶Sr data for malachite are consistent with the original sulfide Lower Orebody being subject to a later oxidizing event.     

Explosive impulse on plates

This paper describes a series of very small scale model tests that were conducted in support of a full scale test program conducted by the Army Research Laboratory at Aberdeen, Maryland for the US Navy to investigate the impulse delivered to a military vehicle by a buried land mine. The full scale tests were conducted in July of 2004 and investigated the effect of various parameters on the impulse delivered. The vehicle was represented by a steel plate and depth of burial, standoff distance, and explosive size (up to 10 pounds of TNT) were changed in the seven tests conducted for the Navy. The full scale tests were conducted in saturated sand. The tests described in this paper used a maximum charge size of 3.3 gm of RDX and PETN. Each of the tests conducted for the Navy were simulated by the small scale tests and a prediction of the impulse that would be measured for each of the tests was made. The small scale tests (as well as the full scale tests results) were also used by the developers of various numerical codes that were also used to predict the impuse that would be measured in the full scale test series.This paper is accompanied by a paper by Taylor et al. (Taylor, L. C., Skaggs, R. R. and Gault, W., 2005, Vertical impulse measurement of mines buried in saturated sand, Fragblast, International Journal for Blasting and Fragmentation, 9, 19-28) in this issue of FRAGBLAST. In the next issue of FRAGBLAST several additional papers will be published. These will be the results of the numerical codes that were used to predict the impulse.