云南朱布镁铁-超镁铁岩体地球化学特征及成因机理探讨

云南朱布镁铁-超镁铁岩体赋存中型铜镍铂族元素矿床,侵位于元谋群片岩和花岗片麻岩中,岩体垂直分异明显,自下而上为橄榄岩、橄辉岩、辉石岩、辉长岩等相带.矿体以底部“边缘矿”为主,上部有呈透镜状产出的少量“上悬矿”.本文报道了朱布岩体主元素、微量元素、铂族元素(PGE)和 Sr-Nd 同位素组成新的测试结果.分析表明朱布岩体具有拉斑玄武质岩浆分异演化趋势,富集 LREE 的分布模式,弱的Nb 异常和较明显的 Sr 负异常,并与峨眉山大火成岩省(ELIP)苦橄岩相类似,暗示两者可能存在成因上的联系.朱布岩体的铂族元素相对分布模式为“Pt-Pd”富集型,原始地幔标准化曲线向左陡倾.较高的(87Sr/86Sr)i (0.7096~0.7107)和较低的εNd(t)(-3.1~-2.3),表明朱布岩浆受到了地壳物质不同程度的混染.通过岩浆演化过程反演,得出其母岩浆性质为苦橄质,并估算地壳混染程度在3%~20%之间,发现在 R (岩浆与熔离硫化物的比例)值为1000~5000时比较吻合朱布样品中硫化物的实际测定值,证实了朱布岩体可能为开放系统的岩浆房,经过多级富集过程,先熔出的硫化物从后续多期次岩浆中吸收了大量 PGE,岩浆房中同时存在堆晶和岩浆演化,分别形成了底层橄榄岩和上部的辉长岩,中间过渡为橄辉岩和辉石岩     

21世纪中国大型工程与工程地质问题

近些年来,我国的国民经济一直是以每年10%以上的速度增长,由此可以预测:随着我国经济欣欣向荣的高速发展,到21世纪将有许多大型工程逐步上马、走向世界大工程的行列。为此,我国的工程地质工作者应先行研究:大型工程前期的工程地质可行性论证。工程开拓期间可能遇到的工程地质难题和新题；工程竣工后的环境工程地质预测及防治等问题,为未来的大型工程设计与施工提供可靠的工程地质依据。     

Frontiers in large igneous province research

Earth history is punctuated by events during which large volumes of mafic magmas were generated and emplaced by processes distinct from “normal” seafloor spreading and subduction-related magmatism. Large Igneous Provinces (LIPs) of Mesozoic and Cenozoic age are the best preserved, and comprise continental flood basalts, volcanic rifted margins, oceanic plateaus, ocean basin flood basalts, submarine ridges, ocean islands and seamount chains. Paleozoic and Proterozoic LIPs are typically more deeply eroded and are recognized by their exposed plumbing system of giant dyke swarms, sill provinces and layered intrusions. The most promising Archean LIP candidates (apart from the Fortescue and Ventersdorp platformal flood basalts) are those greenstone belts containing tholeiites with minor komatiites. Some LIPs have a substantial component of felsic rocks. Many LIPs can be linked to regional-scale uplift, continental rifting and breakup, climatic shifts that may result in extinction events, and Ni–Cu–PGE (platinum group element) ore deposits.

Some current frontiers in LIP research include:

(1) Testing various mantle plume and alternative hypotheses for the origin for LIPs.

(2) Characterizing individual LIPs in terms of (a) original volume and areal extent of their combined extrusive and intrusive components, (b) melt production rates, (c) plumbing system geometry, (d) nature of the mantle source region, and (e) links with ore deposits.

(3) Determining the distribution of LIPs in time (from Archean to Present) and in space (after continental reconstruction). This will allow assessment of proposed links between LIPs and supercontinent breakup, juvenile crust production, climatic excursions, and mass extinctions. It will also allow an evaluation of periodicity in the LIP record, the identification of clusters of LIPs, and postulated links with the reversal frequency of the Earth's magnetic field.

(4) Comparing the characteristics, origin and distribution of LIPs on Earth with planets lacking plate tectonics, such as Venus and Mars. Interplanetary comparison may also provide a better understanding of convective processes in the mantles of the inner planets.

In order to achieve rapid progress in these frontier areas, a global campaign is proposed, which would focus on high-precision geochronology, integrated with paleomagnetism and geochemistry. Most fundamentally, such a campaign could help hasten the determination of continental configurations in the Precambrian back to 2.5 Ga or greater. Such reconstructions are vital for the proper assessment of the LIP record, as well as providing first-order information related to all geodynamic processes.     

北祁连早古生代洋盆是裂陷槽还是大洋盆——与葛肖虹讨论

北祁连早古生代洋盆是裂陷槽还是大洋盆,是一个有争论的问题。文中讨论了蛇绿岩中保存的代表大洋盆存在的印记。认为被夹持于华北地块和柴达木地块之间的北祁连早古生代造山带属于板块增生杂岩带,是由海洋岩石圈残片、消减杂岩、岛弧增生楔等组成的(或许还包括一部分残留陆块).指出北祁连蛇绿岩属于科迪勒拉型,暗示北祁连在早古生代时可能曾经是一个规模较大的洋盆,而非裂陷槽。华北地块和柴达木地块的规模很小,只不过是浩瀚海洋中散布的微小陆块而已。     

基于闪烁仪观测低丘山地人工混交林通量印痕与源区分布

参考Meijninger提出的适用于大孔径闪烁仪(LAS)法的印痕模型,利用位于河南省济源市的华北低丘山地30年生栓皮栎-侧柏-刺槐人工林生态系统的主要生长季2009年5～9月通量等观测数据,计算、分析了该森林生态系统的通量印痕及源区分布.结果表明:①以90%通量贡献区面积为测算对象,不同风向条件下,在大气不稳定时,东南风向时源区面积最小,为1.1547 km2,西南风下最大,为1.5237 km2;在大气层结稳定时,西北风向时源区最小,为1.7271 km2,西南风向时最大,为3.5289 km2.并且在大气不稳定时的源区面积均小于稳定条件下的面积.其中,大气层结稳定时面积最小的西北风向时的源区面积比不稳定时面积最大的西南风向时的源区面积还要大11.8%.②以90%通量贡献区面积为测算对象,晴天条件下,由于湍流交换的逐渐加强,上午源区面积由8:00的1.1483 km2减小到11:00的0.4518 km2.中午之后,湍流交换逐渐减弱,大气趋向稳定层结,源区面积由14:00的0.4779 km2增加到17:00的0.7137 km2.通量源区面积的日变化趋势与大气稳定状况和湍流交换变化趋势大致一致.③以80%通量贡献区面积为测算对象,受大气状况、风向及下垫面性状的影响,各月通量源区各不相同.2009年5～9月期间,各月源区面积分别为1.834、1.680、2.043、1.671、1.380 km2.     

深部碳循环的环境气候效应SCIEI北大核心CSCD

地球表层温度主要由接收的太阳辐射能量及大气温室气体的保温能力共同控制。CO_(2)等温室气体通过对大气温度的调节影响着全球环境气候变化,工业革命以来全球CO_(2)排放量的增加被认为是全球变暖的重要原因,地质历史时期大气CO_(2)浓度的波动与温室和冰室气候的交替出现相对应。地球超过90%的碳赋存于深部,因此地球深部过程的些许波动便会影响到地表碳含量,进而深刻影响着地球的环境气候变化。以往的研究注重地表碳循环对环境气候的影响,对深部碳的贡献考虑不足。最近十余年全球开展了详细的深部碳循环研究,基于已经取得的重要成果,本文从大火成岩省、裂谷和俯冲带的视角对深部碳循环驱动的环境气候效应进行了系统回顾。认为未来的研究需要对地球深部碳循环通量和碳同位素组成进行更精确的定量,这是我们认识深部碳循环对地表环境气候影响的基础;除了碳元素本身我们还需要关注其他挥发性元素和有害金属元素的综合效应;俯冲带作为全球壳-幔相互作用和物质交换循环最重要的场所,应该是进行深部碳循环观察和环境气候效应研究的重点。     

塔里木盆地西北缘二叠纪壳源型碳酸岩的发现及其地质意义

碳酸岩是自然界较为特殊的一类火成岩,由于其在上侵过程中不易受到地壳物质的混染,可以很好地保留源区原始特征,因而在揭示岩浆源区属性和地球深部碳循环等方面具有重要的研究价值。塔里木盆地西北缘阿克苏-乌什南部地区发育多条侵位到新元古界南华系中的火成碳酸岩岩墙或岩脉。这些岩脉的锆石U-Pb测年结果显示出多个年龄峰值,其中最年轻一组(3颗)岩浆锆石的谐和加权年龄为272±4Ma,另外还有400Ma、450Ma、790Ma、850Ma等年龄峰,而这些锆石可能均为碳酸岩岩浆捕获成因。结合区域上发育大量早二叠世辉绿岩岩床及岩墙等侵入事件,推测这些碳酸岩很可能形成于早二叠世(～270Ma)。碳酸岩主要由方解石(90%以上)构成,并含少量的白云石、重晶石、天青石、赤铁矿等其它矿物,可见方解石与白云石之间明显的出溶结构以及野外宏观上碳酸岩包裹围岩等现象。元素地球化学分析显示,碳酸岩CaO含量高(44.40%～50.40%),SiO_2含量低(1.83%～7.97%);稀土元素总量很低(∑REE=21.67 ×10~(-6)～91.32 × 10~(-6)),轻重稀土分异明显(LREE/HREE=3.90～8.40),具有中等负铕异常(δEu=0.61～0.68)和中等至弱负铈异常(δCe=0.59～0.98);大离子亲石元素Sr、Rb、Ba等相对富集,Nb、Ta、Ti等高场强元素相对亏损;稳定同位素δ~(13) C_(V-PDB)值高(-2.69‰～-2.93‰)、δ~(18)O_(V-SMOW)值高(17.33‰～17.86‰)。这些特征与壳源碳酸岩特征相似,而与幔源碳酸岩差别较大。Sr-Nd同位素结果显示高的(~(87)Sr/~(86)Sr)_i值(0.710106～0.710558),低的ε_(Nd)(t)值(-8.46～-12.80),也进一步证实碳酸岩为地壳来源。综合分析认为这些碳酸岩很可能是塔里木二叠纪大火成岩省晚期岩浆事件的组成部分,系由塔里木西北缘地幔柱减压熔融后形成高温的基性岩浆向上侵位运移时,导致下地壳的碳酸盐储库部分熔融形成碳酸岩岩浆,并沿着断裂快速向上侵位形成。本文研究不仅丰富了塔里木大火成岩省的岩石组成认识,而且有助于增进对二叠纪深部复杂壳幔作用过程的理解。     

大尺度地表水热通量的观测、分析与应用

大尺度地表水热通量的观测对实现地面台站观测通量的空间尺度扩展,验证水文模型、数值天气与气候预报模式以及检验遥感监测产品等意义重大.以闪烁仪为例,从测量仪器与观测试验、观测数据的处理与分析、观测数据的应用等方面论述了大尺度地表水热通量的国内外研究进展,并对其发展前景进行了展望.     

Integrated spectral properties of four previously unstudied small angular size galactic open clusters

We have derived fundamental parameters for the previously unstudied concentrated Galactic open clusters Berkeley 77, NGC2587, BH58 and ESO324‐SC15 by means of integrated spectroscopy in the range 3800–6800 Å. The cluster integrated spectra are compared with those of solar metallicity template spectra of Galactic open clusters with known parameters. The spectra were obtained at CASLEO (San Juan, Argentina) with a resolution of 14 Å.We estimated simultaneously age and foreground interstellar reddening by comparing the continuum distribution and line strengths of the cluster spectra with those of template spectra. Berkeley 77 was found to be an old cluster of 3–4 Gyr, while the remaining three clusters are between 400 and 1000 Myr old. The derived foreground reddening values range from E (B – V) = 0.0 in NGC2587 and ESO324‐SC15 to approximately 0.30 in Berkeley 77. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)