山东中侏罗世-早白垩世侵入岩的锆石Hf同位素组成及其意义

对山东中侏罗世-早白垩世侵入岩中锆石的原位Hf同位素分析显示,形成于晚太古代（上交点年龄～2.5 Ga）的继承锆石具有正的εHf（t）值（＋8～＋1）,Hf同位素模式年龄集中在2.6～2.8 Ga,与辽宁古生代金伯利岩中基性下地壳捕虏体中锆石Hf组成和Hf模式年龄十分一致,Hf模式年龄也与研究区变质岩和花岗岩的全岩Nd模式年龄相同,因此,这些继承锆石来自于晚太古代由岩浆底侵形成的基性下地壳.新生锆石出现在继承锆石周围或者以独立颗粒出现,其U-Pb年龄为177 Ma和132～126 Ma,εHf（t）值均为负值（-23～-1）.山东中生代侵入岩的形成与富集岩石圈地幔,亏损地幔和地壳三个端员之间的相互作用有关.其中根据来源于晚太古代下地壳的侏罗纪铜石二长花岗岩限定的研究区下地壳εHf（t）平均值为-20,根据来源于富集岩石圈地幔的早白垩纪沂南辉长岩限定的富集地幔端员的εHf（t）为-16.部分样品锆石εHf（t）变化非常大（-20～-1）,示踪了岩浆作用过程中亏损地幔物质的参与程度的逐渐增强.这种变化是华北晚中生代岩石圈大规模减薄作用的结果.     

大兴安岭南段林西地区花岗岩类的源岩：地壳生长的时代和方式

本文选择大兴安岭南段林西地区的5个典型花岗岩体,在岩相学、全岩主微量元素和Nd-Sr同位素组成研究的基础上,对5个岩体的继承锆石/前锆石和岩浆锆石进行了系统的SHRIMP U-Pb年龄测定和LA-MC-ICPMS Hf同位素组成测定,试图阐明林西花岗岩源岩的组成和性质.锆石SHRIMP U-Pb定年表明：大部分林西花岗岩侵位于早白垩世（135～125 Ma）,它们的源岩的年龄为～146 Ma.一部分花岗岩类是在早三叠世（241 Ma）和晚侏罗世末（146 Ma）侵位的,它们的源岩的年龄分别是263 Ma和165 Ma.测定了100个锆石206Pb/238U年龄,都年轻于300 Ma,反映在下地壳源区不存在前寒武纪岩石.做了175个锆石Hf同位素组成测定,均给出高正值εHf（t）,说明源岩具有初生地壳的性质.在相同的εNd（t）值下,林西花岗岩的锆石εHf（t）值显著高于地球阵列和夏威夷洋岛玄武岩,这种εHf～εNd脱耦性指示源岩中含有远洋沉积物即古生代俯冲增生杂岩的组分.206pb/238U年龄t=263～165Ma的锆石的εHf（t）值构成近乎平行于亏损地幔Hf同位素演化线的趋势列,说明源岩基本为俯冲洋壳镁铁-超镁铁岩.t=146～125 Ma的锆石的εHf（t）值大幅度降低;同时,从晚侏罗世末到早白垩世,发生了强烈的花岗质岩浆活动.地幔上隆和岩浆底侵以及俯冲洋壳的折返,是造成下地壳源岩组成急剧变化和热梯度上升的原因.以底侵镁铁质岩石为主、以古生代俯冲增生杂岩为次的源岩的熔融,产生了马鞍子、夜来改和龙头山2花岗岩（岩套2）.林西镇南西的小城子岩体的源岩则以古生代俯冲增生杂岩为主,并含一定量的底侵镁铁质岩石.5个岩体的岩浆锆石的176Hf/177Hf值系统低于继承锆石/前锆石者,t=146～125 Ma的锆石从中心到边缘176H/177Hf值呈现降低的趋势或者系统的变化.上述特征反映从源岩的初始熔融直到最终产生花岗岩浆的全过程中,下地壳的熔融区间逐渐扩张、卷入熔融的组分不断增多的过程.岩套1花岗岩类是镁质或Ⅰ型花岗岩,岩套2则表现出A型花岗岩以及从典型到不典型的铁质花岗岩的特征.岩套1和岩套2花岗岩类的岩相学和地球化学特征取决于源岩的性质.岩套1的源岩是相对氧化和含水的洋壳镁铁-超镁铁岩或俯冲增生杂岩;岩套2的源岩则由相对还原和贫水的底侵拉斑玄武岩以及不同分数的俯冲增生杂岩构成.     

蚌埠隆起区中生代花岗岩的岩石成因：锆石Hf同位素的证据

对蚌埠隆起区中生代不同时期的花岗岩中6个岩体的锆石LA-MC-ICP MS原位Hf同位素的研究,据此限定它们的岩浆源区和重建华北克拉通东南部的构造格架.结果表明,中生代不同时期的花岗岩中岩浆锆石的初始Hf同位素组成（εHf（t））可以分成两组：第一组的女山（130 Ma）和西庐山花岗岩（130 Ma）的εHf（t）值分别为-18.4和-16.1;第二组的曹山（110 Ma）、锥山二长花岗岩（110 Ma）和蚂蚁山花岗岩（110 Ma）以及淮光花岗闪长岩（130 Ma）的εHf（t）值分别为-22.3、-23.1和-21.1以及-28.1,这些岩浆锆石低的εHf（t）值表明它们可能来源于古老的大陆下地壳.女山和西庐山岩体中早古生代-新元古代继承锆石具有低的εHf（t）值（-2.3～-7.7）和1.52 Ga～1.79 Ga的Hf同位素两阶段模式年龄,表明它们的岩浆源区主要以扬子克拉通下地壳物质为主.曹山、锥山和蚂蚁山以及淮光岩体中岩浆锆石的Hf同位素两阶段模式年龄为1.89 Ga～2.58 Ga,结合淮光岩体中古元古代继承锆石和3400 Ma捕获锆石中低的εHf（t）值（-5.7～-6.8,-0.6、-0.9）和古老的Hf同位素两阶段模式年龄（2.44 Ga～2.80 Ga,3.7 Ga）,表明它们主要来源于华北克拉通下地壳物质的部分熔融.淮光和女山岩体中古元古代-新太古宙继承锆石中正的εHf（t）值（0.3～6.7）以及高的εHf（t）值（16.9～21.7）的存在,暗示形成这些古老继承锆石的初始物质中有幔源物质的涉入.蚌埠隆起区深部地壳中扬子克拉通基底物质的存在暗示扬子克拉通可能沿着郯庐断裂带向西或北西方向俯冲于华北克拉通之下.     

冀北小张家口超基性岩体的锆石U-Pb年龄和Hf同位素组成

采用离子探针（SHRIMP Ⅱ）测得小张家口基性-超基性岩体中的锆石主要有220±5Ma和491±7Ma两组年龄,以及一个很老的继承锆石年龄2453Ma.年龄为220±5Ma的一组锆石（A组）具有典型的岩浆型振荡环带,这组年龄应代表该岩体的侵位年龄.A组锆石的^176Hf/^177Hf比值从0.282557到0.282690,εHf（220Ma）=-2.9～＋1.66.年龄为491±7Ma的一组锆石（B组）具有变质成因的蝴蝶结构（Butterfly structure）和熔蚀边,属于继承锆石.B组锆石的^176Hf/^177Hf比值从0.282239到0.282483,εHf（491Ma）=-8.6～0.06.207Pb/206Pb年龄为2453Ma的锆石应该是岩浆侵位时从华北克拉通古元古代基底中捕获的锆石.A组锆石的Hf同位素数据表明,220Ma左右由于华北北缘岩石圈伸展,导致软流圈地幔上涌,亏损的软流圈地幔流/熔体与富集的岩石圈地幔相互作用并混合,这种混合地幔源区发生部分熔融而形成小张家口基性-超基性岩体.B组锆石可能是小张家口岩体在岩浆侵位过程中捕获的来源于富集地幔或大陆下地壳的锆石.     

苏鲁造山带荣成超高压地体片麻岩锆石年龄和铪同位素组成特征

本文对苏鲁造山带内荣成超高压地体片麻岩样品进行了锆石U-Pb年龄、Hf同位素和全岩Nd同位素分析,旨于探讨片麻岩的原岩性质及成因.3个片麻岩样品的锆石SHRIMP U-Pb年龄（770 Ma和710 Ma之间）表明原岩形成于晚元古代,与Rodinia超大陆裂解过程的岩浆活动时间相吻合.14个片麻岩的单阶段钕模式年龄变化在1.70 Ga至2.30 Ga（平均～1.93 Ga）,表明荣成超高压地体片麻岩平均地壳存留时间为古元古代,与扬子陆块的平均地壳形成年龄相一致,暗示具有扬子陆块属性.其锆石εHf（t）值（t=750 Ma）和模式年龄值变化范围大.2个片麻岩的锆石具有非常负的εHf（t）,平均值为-16.4,铪模式年龄为2.70 Ga.6个片麻岩的锆石εHf（t）平均值为-7.7,铪模式年龄为2.15 Ga.这些结果表明荣成超高压地体部分原岩主要由太古代-古元古代地壳物质在晚元古代时重熔形成的,进一步说明荣成地区可能有扬子陆块的太古代地壳残留.另有6个片麻岩的锆石εHf（t）变化范围为-0.56至6,6之间,其中部分锆石的两阶段Hf模式年龄为0.81 Ga至0.94 Ga,表明片麻岩原岩晚元古代形成时,有幔源岩浆活动和新生地壳形成,可能同时存在强烈壳-幔相互作用,上侵的幔源岩浆底侵导致上覆扬子陆块太古代-古元古代地壳物质重熔,形成花岗质岩浆.     

辽东矿洞沟正长岩成因及其构造意义：锆石原位微区U-Pb年龄和Hf同位素制约

矿洞沟岩体位于华北克拉通东部,由粗粒正长岩、细粒正长岩和闪长岩组成,其中细粒正长岩和闪长岩具有明显的岩浆混合特征,它们侵入到粗粒正长岩中.锆石的LA-ICPMS U-Pb年代学研究表明,粗粒正长岩形成于1879±17 Ma,而细粒正长岩和闪长岩分别侵位于1874±18 Ma和1870±18 Ma,三者在误差内基本相同,因此,矿洞沟岩体的侵位时代为古元古代.矿洞沟正长岩和闪长岩富集轻稀土元素和大离子亲石元素,亏损高场强元素,具有相对均一的全岩Nd同位素.但粗粒正长岩、中粒正长岩和闪长岩中锆石Hf同位素组成却不均一,分别为εHf（t）=-2.5～＋3.0,-1.5～＋3.4和-3.5～＋2.7,明显高于辽东地区太古代片麻岩演化到古元古代时的Hf同位素组成,表明它们来源于太古代新生地壳的部分熔融并有大量地幔物质的加入.野外地质观察、主量元素组成及岩石中锆石具有相同U-Pb年龄却具有不同的Hf同位素等特征表明,矿洞沟正长岩和闪长岩是壳源岩浆和幔源岩浆混合作用的结果.矿洞沟正长岩体的侵位标志着辽东地区在古元古代时期处于南北地块碰撞后的伸展环境,与华北克拉通东部陆块的形成和演化以及全球古元古代末期Columbia超大陆的形成和裂解有关.     

莫河花岗岩的锆石U-Pb和Lu-Hf同位素研究：柴北欧龙布鲁克微陆块始古元古代岩浆作用年龄和地壳演化约束

欧龙布鲁克微陆块具典型的基底与盖层二元结构,基底自下而上由德令哈杂岩、达肯大坂岩群和万洞沟群三个岩石-构造单元组成.应用LA-ICP-MS测定了德令哈杂岩中的莫河花岗岩体的27个颗锆石的U-Pb同位素成分,其中26颗锆石发生不同程度的放射成因铅同位素丢失,其不一致线上交点年龄为2470＋19/-18 Ma.应用LA-MC-ICP-MS测定了25颗锆石的Hf同位素成分,其中岩浆结晶成因的23颗锆石的Hf（2470 Ma）=0.28129～0.28140,平均值0.28134±0.00003;εHf值的变化范围2.94～6.95,加权平均值4.58＋0.54/-0.76,长英质地壳存留年龄TCDM=2.54～2.75Ga,加权平均值2.66＋0.04/-0.02 Ga.以上数据将该花岗岩的形成年龄约束在2470 Ma,其岩浆来源于地幔物质的部分熔融,指示欧龙布鲁克微陆块在～2.5 Ga的地壳增生事件.     

大别山超高压榴辉岩和花岗片麻岩中锆石Lu-Hf同位素研究

对大别山超高压榴辉岩和花岗片麻岩进行了锆石Lu-Hf同位素分析,结果为原岩来源提供了制约,表明扬子陆块在Rodinia超大陆裂解时的裂谷岩浆活动中发生了显著的陆壳生长.对这些锆石的不同区域进行的U-Pb和Lu-Hf同位素分析和比较表明,不同成因的锆石在^206Pb/^238U年龄、初始Hf同位素组成、Th/U及Lu/Hf比值等方面具有明显的差异.与年龄较老的岩浆核部和幔部相比,年轻的变质增生边具有低的Th/U和Lu/Hf比值但高的εHf（t）值.不同成因锆石的Th/U和Lu/Hf比值存在着正相关性,表明变质作用对锆石的U-Th-Pb和Lu-Hf同位素体系有着相似的影响.高级变质作用有时能够引起岩浆锆石增生边^176Hf/^177Hf比值的显著升高,导致变质新生颗粒或增生边类似于新生地壳的高εHf（t）值假象.对榴辉岩和片麻岩锆石核部的分析发现,镁铁质和长英质原岩在大约750 Ma左右形成一个双峰式火山岩套,另外包含少量的年龄约为2.15 Ga的陆壳.初始Hf同位素组成可分成两组：第一组具有正的εHf（t）值,为5.9±0.9～12.9±0.7;第二组εHf（t）值在零左右,为-4.3±0.5～2.3±0.3.正的εHf（t）值与较年轻的模式年龄相对应,负的εHf（t）值与古元古代模式年龄相对应.前者表明,在扬子陆块北缘裂谷岩浆作用将亏损地幔物质加入到大陆地壳中,同时在新元古代中期的裂谷构造带中存在同时期的壳-幔相互作用.因此,在扬子陆块北缘新元古代中期裂谷岩浆活动中,既有新生地壳生长和即时再造,也有古老地壳再造.     

柴北缘花岗片麻岩的岩浆作用计时和前寒武纪地壳增长的锆石U-Pb年龄和Hf同位素证据

本文应用LAM-ICPMS技术测定了柴达木盆地北缘花岗片麻岩带中的锡铁山东全吉河花岗岩和都兰县北部沙柳河花岗岩的锆石U-Pb年龄,利用LAM-MC-ICPMS技术选择测定了沙柳河花岗岩锆石Hf同位素成分.全吉河花岗岩岩浆结晶锆石的谐和年龄为910＋15/-17 Ma;捕虏晶锆石的207Pb/206Pb年龄为1351 Ma;～520 Ma的变质锆石（232Th/238U=0.04）206pb/238U年龄可能是前高压超高压构造事件的产物.沙柳河花岗岩的岩浆锆石普遍含有继承碎屑锆石核.21个颗粒测得21个数据中,代表岩浆结晶锆石的10个点的Robust（Median）平均206Pb/238U年龄为920＋31/-17 Ma,碎屑锆石核207Pb/206pb年龄大于1250 Ma.在沙柳河花岗岩30颗锆石的30个Hf同位素分析点中,27个代表纯粹岩浆结晶锆石的176Hf/177Hf=0.282081～0.282222,平均0.282178＋0.000009/-0.000015,以920 Ma计算的HfI=0.28206～0.28220,平均值0.28215＋/-0.00003;εHf值的变化范围＋0.21～-4.70,Robust（Median）加权平均值为-1.53＋0.41/-0.52;锆石Hf的地壳模式年龄（TCDM）范围是1.59～1.75 Ma,Robust（Median）加权平均值为1.68＋0.03/-0.02 Ma.其余2个锆石为继承性锆石,其176Hf/177Hf比值分别为0.281892和0.281792,HfI和εHf值分别为0.28186～0.28178,和-11.83～-14.82,TCDM=2.18～2.33 Ga.结合前人的研究结果,柴北缘花岗片麻岩的岩浆作用持续时间为～950 Ma～～910 Ma.峰值年龄为～920 Ma,以沙柳河花岗岩为代表的柴北缘过铝S-型花岗片麻岩的岩浆来自现今剥露于地表的沙柳河岩群之下具高度再循环上地壳物质的基底表壳岩系;该物质的形成年龄可约束在1.4～1.7 Ga,保存了蚀源区～1.7 Ga和～2.3 Ga的地壳增生事件的年代学记录.     

大别造山带碧溪岭橄榄岩中锆石U-Pb年龄和Hf同位素研究

在详细形态和内部结构研究基础上,对碧溪岭橄榄岩锆石进行了配套的U-Pb年龄和Hf同位素分析.碧溪岭橄榄岩锆石主体是变质成因的,但有少量岩浆锆石残留.这些锆石主体给出了220～210 Ma的变质生长/重结晶作用年龄;一颗具较高Th/U比值的锆石给出646 Ma的近协和年龄,限定了早期岩浆结晶作用的最小年龄.真正的侵位年龄可以由745 Ma的上交点年龄来限定;210～222 Ma则记录着深俯冲陆壳折返过程中的锆石生长.除少数颗粒的εHf为负值外（-2.9）,大部分锆石的εHf是正的（高速＋8.1）并具新元古代的亏损地幔模式年龄（0.6～1.0 Ga,平均0.8 Ga）.这些结果说明碧溪岭橄榄岩的初始物质是扬子大陆岩石圈内新元古代岩浆堆积作用产物.这样的岩浆堆积物来源于亏损的软流圈地幔,侵入于扬子的深部地壳之中（如底侵）并部分混染了古老地壳组分.它们随扬子向华北之下深俯冲碰撞和造山带折返过程中经历着复杂的变质改造作用.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

To serve and promote science development via innovation

CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

Tracing the origin and early radiation of birds——Paleornithologist ZHOU Zhonghe

With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants."     

The Information Environment and Universal Service

This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.