A Periglacial Palaeoenvionment in the Upper Carboniferous–Lower Permian Tobra Formation of the Salt Range, Pakistan

The Upper Carboniferous—Lower Permian(Upper Pennsylvanian-Asselian) Tobra Formation is exposed in the Salt and Trans Indus ranges of Pakistan.The formation exhibits an alluvial plain(alluvial fan-piedmont alluvial plain) facies association in the Salt Range and Khisor Range.In addition,a stream flow facies association is restricted to the eastern Salt Range.The alluvial plain facies association is comprised of clast-supported massive conglomerate(Gmc),diamictite(Dm)facies,and massive sandstone(Sm) Hthofacies whereas the stream flow-dominated alluvial plain facies association includes fine-grained sandstone and siltstone(Fss),fining upwards pebbly sandstone(Sf),and massive mudstone(Fm) Hthofacies.The lack of glacial signatures(particularly glacial grooves and striatums) in the deposits in the Tobra Formation,which are,in contrast,present in their timeequivalent and palaeogeographically nearby strata of the Arabian peninsula,e.g.the AI Khlata Formation of Oman and Unayzah B member of the Saudi Arabia,suggests a pro-to periglacial,i.e.glaciofluvial depositional setting for the Tobra Formation.The sedimentology of the Tobra Formation attests that the Salt Range,Pakistan,occupied a palaeogeographic position just beyond the maximum glacial extent during Upper Pennsylvanian-Asselian time.     

喀喇昆仑山厦呈、吕莫慕士塔格山段现代冰川分布及变化特征

在全球气候普遍变暖、冰川大面积退缩的大背景下,为揭示山岳冰川十分发育的喀喇昆仑山脉现代冰川分布及变化特征,以中等空间分辨率(ETM和Landsat 8)卫星数据为主要数据源,采用人机交互式解译方法完成了厦呈慕士塔格山、吕莫慕士塔格山段冰川变化遥感调查,基本查明了区内冰川面积、分布特征和变化状况,共调查1 373处冰川,其中中国境内有554处,境外克什米尔印控区有819处; 同时对区内典型冰川变化进行了2期对比分析,得出冰舌退缩、前进或稳定现象同时存在的结论,为喀喇昆仑山脉冰川变化研究提供了参考依据,为我国西部边海防地区水资源的开发利用和冰雪灾害的防治等提供了科学依据。     

大兴安岭北段偃尾山铜银矿床流体包裹体与矿床成因类型研究

偃尾山铜银矿床是大兴安岭北段呼中-塔源成矿带内新发现的中小型矿床。矿床围岩蚀变呈面状分布,主要蚀变类型为硅化、碳酸盐化、黄铁矿化、伊利石化、高岭石化和绢云母化。热液成矿期可分为三个阶段:成矿早期石英-黄铁矿阶段(含少量黄铜矿)、主成矿期石英-斑铜矿-黄铜矿-辉铜矿(含铜硫化物)阶段和成矿晚期石英-碳酸盐-萤石阶段(含少量方铅矿和闪锌矿)。该矿床流体包裹体主要为富液相包裹体,也有少量纯气相包裹体,未见含子矿物包裹体。主成矿阶段流体包裹体均一温度为155℃~342℃,峰值集中在160℃~230℃,冰点温度在﹣3.3℃~﹣0.3℃,盐度为0.53%NaC_(leqv)~5.41%Na Cleqv;流体成分以K~+、Na~+、SO_4~(2-)为主,含少量Ca~(2+)和Cl~-,气相成分以H_2O为主,含少量的CO_2;流体δ~(18)O在-11.8‰~-13.72‰之间,δD变化范围在-105‰~-137‰之间。总体上,成矿流体为低温低盐度流体,流体来源主要是大气降水,成矿流体和矿床蚀变-矿化特征显示本矿床可能为高硫型浅成低温热液矿床。流体压力的突然降低可能是成矿物质沉淀的主要机制。偃尾山矿床可能代表了区域上同时代一种新的矿床类型,后续深入研究将有助于认识该区域成矿规律和找矿方向。     

Provenance,tectonic setting and source of Archean metasedimentary rocks of the Browns Range Metamorphics,Tanami Region,Western Australia

This study combines U–Pb age and Lu–Hf isotope data for magmatic and detrital zircons, with whole-rock geochemistry of the Browns Range Metamorphics (BRM), Western Australia. The BRM are medium- to coarse-grained metasandstones that consist of angular to sub-rounded detrital quartz and feldspars with minor granitic lithic fragments. The sequence has undergone partial to extensive quartz–muscovite alteration and rare-earth-element mineralisation and has been intruded by mafic/ultramafic, syenitic and pegmatitic intrusive rock units. Uranium–Pb and Lu–Hf isotopic data on detrital zircons from the metasandstones and intruding granitic rocks yield a well-defined age of ca 3.2 to ca 3.0 Ga for all samples, with relatively radiogenic ?_Hf values (?_Hf = –1.7 to 5.1) indicating derivation from Mesoarchean granite basement of juvenile origin. This is consistent with geochemical and petrological data that support deposition from a granitic source in a continental rift basin setting. The timing of sediment deposition is constrained between the ca 3.0 Ga age of the source rocks and ca 2.5 Ga age of the granitic intrusive bodies that cross-cut the metasedimentary rocks. The ca 2.5 Ga zircons from the intrusive rocks have ?_Hf model ages of ca 3.4 to ca 3.1 Ga, which is consistent with formation via partial melting of the BRM, or the Mesoarchean granite basement. Zircons of the Gardiner Sandstone that unconformably overlies the BRM return detrital ages of ca 2.6 to ca 1.8 Ga with no trace of ca 3.1 Ga zircons, which discounts a significant contribution from the underlying BRM. The Mesoarchean age and isotopic signatures of the BRM zircons are shared by some zircon records from the Pine Creek Orogen, and the Pilbara, Yilgarn and Gawler cratons. Collectively, these records indicate that juvenile Mesoarchean crust is a more significant component of Australian cratons than is currently recognised. This work also further demonstrates that detrital minerals in Paleoproterozoic/Archean sedimentary rocks are archives to study the early crustal record of Earth.     

大兴安岭西坡甲乌拉铜银铅锌矿床富碱花岗斑岩的成因及其地质意义:锆石U-Pb定年和地球化学特征

甲乌拉铜银铅锌矿床是大兴安岭西坡得尔布干铜(钼)-银铅锌成矿带内大型铅锌银矿床之一,长期以来被认为是与火山、次火山热液作用有关的浅成热液矿床;然而近期的研究显示,其成矿可能与深部细脉浸染型铜矿化有着密切的成因联系。为此,我们在野外调研的基础上,开展了与细脉浸染型铜矿化有关的富碱花岗斑岩的年代学和地球化学研究工作。实验结果揭示:花岗斑岩的w(SiO_2)为71.59%~72.36%,w(TiO_2)为0.46%~0.58%,w(Al2O3)为15.45%~15.92%,w(Fe_2O_3)为0.74%~0.90%,w(FeO)为1.67%~1.96%,w(MgO)为0.55%~0.89%,w(Na_2O+K_2O)为9.01%~9.91%,K2O/Na2O值为1.37~2.15,里特曼指数(σ)为2.77~3.43,碱度指数(AR)为3.13~3.96,指示该类岩石为钾玄岩系列、高钾质、过铝质的A型富碱花岗斑岩;稀土元素总量(∑REE)为(350.11~408.80)×10-6,轻重稀土比值(∑LREE/∑HREE)为11.25~11.44,δEu主要集中在0.38~0.44,具有较强的轻重稀土分馏和明显负铕异常、强烈亏损相容元素(Ni、Co、Cr、V、Yb、Eu等)、富集不相容元素(Cs、Rb、Pb、U、Th、Zr、Hf等)、相对亏损Li、Sr等不相容元素以及持有较高的Rb/Sr(0.93~1.31)、Zr/Hf(29.38~35.61)值等特征,揭示原始岩浆来源于以CO_2为主的流体交代下地壳部分重熔或以H2O为主的流体交代下地壳部分重熔,岩浆作用过程受到了强烈的碳酸盐混染,并具有提供铜银铅锌成矿流体的属性。鉴于所获该类岩石具有岩浆和热液锆石共伴生的特点,且岩浆锆石的206Pb/238 U年龄加权平均值为(146.4±1.6)Ma(MSWD=1.30,n=12)、热液锆石206Pb/238 U年龄加权平均值为(143.1±3.9)Ma(MSWD=0.56,n=5),结合前人的研究成果,得出甲乌拉矿床成矿发生在早白垩世初期,与成矿密切的岩浆作用发生在晚侏罗世末,并认证甲乌拉矿床为斑岩型铜-浅成热液铜银铅锌成矿系统;成岩成矿地球动力学背景适值古太平洋板块向欧亚板块俯冲的大陆内部挤压向伸展转换的构造环境,或蒙古—鄂霍茨克洋闭合后造山带碰撞伸展的环境。     

从秦岭蕨类植物区系地理成分论秦岭山地生态分界线的划分

依据2007~2008年野外实地调查以及相关文献资料,运用植物区系地理学和数量生态学方法,分析了秦岭蕨类植物区系的物种组成和地理分布特征,划分了秦岭蕨类植物的垂直带谱,并以此为基础探讨了秦岭山地生态分界线的划分,得出以下主要结论:(1)秦岭共有蕨类植物36科85属311种,优势科为鳞毛蕨科、蹄盖蕨科和水龙骨科,优势属为鳞毛蕨属和耳蕨属;在科属水平上,以热带成分占优势;而种的水平则以温带成分占绝对优势。(2)根据秦岭蕨类植物南北坡垂直带谱的对比分析,南坡海拔1000m左右应该是一条重要的生态分界线。(3)南坡1000m以下蕨类植物区系组成更接近亚热带区系,而其他地带则与温带蕨类植物区系更为接近,DCA排序很好地证明了此结果。综合来看,将南坡海拔1000m作为秦岭山地亚热带与暖温带的生态分界线较为科学。     

基于R/S分析黄河及黄土高原主要河流水资源的变化

河流水资源观测资料反映河流随时间变化,它表现为一时间系列。作为非线性分析的工具,R/S可以有效地分析这些资料的时间系列。将R/S 这一时间序列分析方法引入到水资源观测资料的处理和分析中,并应用该方法对黄河及黄土高原地区主要河流在1956—2004年间水资源观测数据进行处理,预测了今后黄土高原地区水资源的变化情况。分析结果表明,黄河及黄土高原地区主要河流径流量赫斯特指数在0.2771～0.3305之间,均小于0.5,背离了正常的长程相关趋势性增强的变化规律,预测了径流量逐步增大的趋势。     

Cambrian trace fossils and worm like impressions from the Tal Group, Gopi-Chand-Ka Mahal section, Mussoorie syncline, Lesser Himalaya

Cambrian trace fossils and worm like impressions are described herein from the three stratigraphic units of Tal Group of rocks exposed along the track from Maldeota to Dhaulagiri in Gopi-Chand-Ka Mahal sec-tion, Mussoorie syncline. The upper 10 m thick sand-stone succession (Arenaceous Member) of Deo-Ka- Tibba Formation (lower Tal Group) contains high den-sity and low diversity Skolithos pipe rock. The Sko-lithos pipe rock in sandstone succession of Arenaceous Member (Deo-Ka-Tibba Formation) indicates shallow marine condition under sand shifting environment of deposition. Higher in the succession, in calcareous Member (Deo-Ka-Tibba Formation), Cruziana ichno-facies occurs in association with Monomorphichnus, Planolites and Paleophycus.     

精密测距测速系统的研究与应用

精密测距测速系统（ＰＲＡＲＥ）是由德国发展的双频双程微波卫星跟踪系统,其空间部分搭载在欧洲航天局（ＥＳＡ）的第二颗资源遥感卫星ＥＲＳ－２上并正常运行至今,该系统具有全天候,全自动,台站便于流动,数据多等特点,其高精度的跟踪信息可用于ＥＲＳ－２的定轨以主某些大地测量与地球物理参数的确定,其双频特性可用于电离层方面的研究,另外,ＰＲＡＲＥ还可用于精确的时钟同步,详细介绍了ＰＲＡＲＥ的发展,构成,测量原     

非静力模式中几种垂直网格计算特性的对比研究

从非静力滞弹性方程组出发，将惯性重力波的水平波长分几百公里、几十公里和几公里三种情况，从频率、群速和各速的垂直尺度范围等方面对现有的几种垂直网格进行比较讨论。结果表明：在非静力模式中，CP网格和LZ网格适合于各种不同水平尺度惯性重力波的模拟；L网格和LY网格适合于水平尺度为几十公里以上的惯性重力波的模拟；LTS网格和CPTS网格比较适合于水平尺度的几十公里以下的惯性重力波的模拟。