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1.
吉林色洛河地区发育高镁安山岩类,SHRIMP锆石U-Pb定年结果表明它们形成于晚二叠世（252±5Ma）.色洛河高镁安山岩类（SiO259.08%～65.67%）具有富MgO（3.68%～5.30%）,高Mg#值（0.62～0.68,平均0.66）,高Cr（203.17×10^-6～379.70×10^-6,平均258.79×10^-6）、Ni（98.13×10^-6～249.35×10^-6,平均137.00×10^-6）含量;富集大离子亲石元素（如Cs、K、Pb、Rb和Ba）,亏损高场强元素（如Ta、Ti、Nb、P）;富集LREE（Ce39.14×10^-6～48.74×10^-6）,强烈亏损HREE（Yb 0.95×10^-6～1.27×10^-6,Y 10.80×10^-6～13.13×10^-6,（La/Yb）N13.27～16.66）;但它们含有较低的Sr（158.62×10^-6～369.77×10^-6,平均258.52×10^-6）.它们属于中钾、钙碱性系列,具有明显的结晶分异和同化混染特征.上述地球化学特征表明它可能与消减沉积物流体交代形成富集地幔的部分熔融有关,其后又经历了分异和混染作用.这揭示它们形成于活动陆缘的构造背景,表明晚古生代末期古亚洲洋板块仍在消减,华北地块和佳木斯-兴凯地块（中亚造山带）最终的拼合时间可能在二叠纪之后. 相似文献
2.
皖东的滁州、上腰铺岩体位于扬子地块东缘、毗邻郯庐断裂带东侧,与之伴生有一些铜（金或铁）矿化.它们的黑云母的40Ar-39Ar定年结果分别为127.17±0.40Ma,129.90±0.23 Ma.滁州、上腰铺侵入岩在地球化学特征上与埃达克岩基本一致：如SiO2＞56%,高Al2O3（14.84%～16.38%）、Sr（369×10^-6～1335×10^-6）、Sr/Y（43～185）与La/Yb（22～44）,但低Y（5.51×10^-6～11.0×10^-6）,Yb（0.51×10^-6～1.09×10^-6）,无明显Eu异常-正的Eu异常（δEu=-0.75～1.28）.另外,岩体中部分样品具有较高的MgO（2.23%～5.25%）、Mg#（53～68）和Cr（89.6×10^-6～206×10^-6）、Ni（43.0×10^-6～72.0×10^-6）,类似于高镁安山岩.这两个岩体的Nd-Sr同位素特征为：（^87 Sr/^86 Sr）I=0.7060～0.7067,εNd（t）=-11.53～-14.07,说明其由俯冲洋壳熔融形成的可能性较小.我们认为,滁州、上腰铺埃达克质侵入岩可能由拆沉下地壳熔融形成,熔融产生的岩浆在穿过上覆地幔的过程中,与地幔橄榄岩发生强烈相互作用,一方面,由于地幔橄榄岩的混染而使得埃达克质岩浆的MgO、Cr和Ni含量显著增高;另一方面,岩浆中的Fe2O3可能加入到地幔中,导致地幔的氧逸度（fo2）,）增高,地幔中金属硫化物被氧化,地幔中亲铜元素则以硫酸盐的形式进入熔体中.富含Cu、Au等成矿物质的熔体在快速上升到地壳浅处时,可能由于温度、压力或氧逸度（fo2）的降低,释放出Cu、Au等成矿物质,导致矿化. 相似文献
3.
我国西南天山地区那拉提北缘断裂北侧出露寒武纪（516.3±7.4Ma）橄榄拉斑玄武岩，其Al2O3（120.71％-14.14％）、P2O5（0.09％-0．21％）含量较低，TiO2（1.39％-2．35％）、MgO（5.35％-8.14％）含量中等，全Fe2O3（11.74％-16．03％）含量较高，球粒陨石标准化稀土分布型式平坦，（La／Sm）.和（Y／Nb）.比值接近1，为过渡型洋脊玄武岩（T-MORB）；并且Th／Ta比值（0．8—1.5）低，高场强元素（Nb，Ta，Zr，Hf，P）没有明显亏损，缺乏陆壳混染或俯冲带流体活动的印迹.部分T-MORB的Fe、Ti含量较高（FeO^T〉12％，TiO2〉2％，FeO^T／MgO〉1．75），Mg^#值（0．40—0.49）和Cr（53×10^-6-110×10^-6）含量较低，属于Fe-Ti玄武岩（ferrobasalt），应为岩浆依Fenner趋势发生较高程度结晶分离演化的产物，很可能形成于洋中脊的扩展型裂谷环境.我们认为，那拉提北缘寒武纪T-MORB和Fe-n玄武岩可能与境外吉尔吉斯斯坦境内北天山南缘的旱古生代Terskey蛇绿岩带相连，为Terskey蛇绿岩的残片；寒武纪我国境内发育Terskey洋.那拉提北缘断裂可能与尼古拉耶夫线相连，代表西南天山地区Terskey洋闭合形成的一条早古生代缝合带. 相似文献
4.
克拉玛依西山的枕状玄武岩与浊积岩-凝灰岩共生，厚度大于400米的枕状玄武岩层被火山角砾岩-安山岩-硅质岩．凝灰岩覆盖。岩枕之间充填着硅质泥岩。锆石SHRIMP定年结果表明，枕状玄武岩可能在早寒武世形成（〉517Ma，这套地层曾经一直被认为属于石炭系）。枕状玄武岩的稀土元素含量（117．4×10^-6～153．6×10^-6）和配分模式与洋岛玄武岩（OIB）基本一致。枕状玄武岩中大离子亲石元素（Cs、Rb、Ba、K、Pb和Sr）的含量变化较大（明显偏离OIB），高场强元素（Nb、Ta、Zr、Hf、Ti和P）相对OIB和原始地幔没有表现出明显异常[e．g．，（Nb／Ta）PM=0．92-O．98，（Zr／Hf）PM=1．08-1．18]。西准噶尔地区存在这套OIB型海相火山．沉积建造说明古亚洲洋在西准噶尔地区于寒武纪就已经存在。这套海相玄武岩岩枕中存在大量古元古代一新太古代（1883—2536Ma）岩浆锆石的事实说明，早古生代洋岛玄武岩岩浆源区存在古老大陆地壳物质。 相似文献
5.
中国东部燕山造山带发育着大量的中-晚侏罗世髫髻山期（蓝旗期）中酸性钙碱性火山岩,它们具有类似于埃达克岩的地球化学特征,如SiO2（≥55.48%）、Al2O3（≥14.25%）和Na2O（≥3.11%）含量高,而MgO（＜3.0%,Mg#≤0.49）含量低;微量元素Sr（≥554×10^-6）、Ba（≥819×10^-6）含量及Sr/Y比值（29～101）较高,而Yb（＜1.70×10^-6）、Y（＜21×10^-6）含量及Rb/Sr比值（0.01～0.19）较低;轻重稀土分馏十分明显（（La/Yb）N＞14.5）,Eu负-正异常弱（0.79～1.01）,高场强元素（如Nb、Ta）相对亏损.火山岩的Nd、Sr、Pb同位素比值变化小,具有富集地幔特征.作者认为其岩浆起源于增厚下地壳玄武质岩石的部分熔融.中-晚侏罗世髫髻山期（蓝旗期）火山岩是燕山运动的产物,其火山喷发标志着燕山地区从古亚洲洋构造体系转入到古太平洋构造体系,这对探讨燕山造山带中生代岩浆演化和区域构造演化具有重要意义. 相似文献
6.
乌拉特中旗克布岩体位于内蒙古中西部,属于华北克拉通北缘中段.克布岩体具有埃达克岩的特征：SiO2=57.66～66.94%（＞56%）,Al2O3=16.81～18.47%（＞15%）,MgO=1.33～3.28%（＜3%）;Y=7.25～13.46×10^-6（≤18×10^-6）,Yb=0.72～1.42×10^-6（≤1.9×10^-6）,Sr=540.4～655×10-6（＞400×10^-6）;高场强元素（HFSEs,如Nb、Ta、Ti、Zr）含量低,LRRE富集（La/Yb=12.11～28.56）,Eu为弱负异常至正异常（δEu＊=0.95～1.09）.高Sr/Y（48.66～74.57）、La/Yb以及中等Mg#（38.72～46.16）、K2O（1.11～2.17）近似于壳源埃达克岩.克布岩体具有低εNd（t）（=-15.1）,高（^87Sr/^86Sr）i（=0.7073）,也表明了它们的源岩来自大陆下地壳,明显不同于板片熔融来源的埃达克岩同位素特征,而与中国东部的埃达克质岩近似.与华北克拉通晚侏罗世下地壳拆沉作用形成的埃达克岩相比,克布岩体具有低的过渡金属元素含量.克布岩体可能为玄武质液体底侵,导致变厚的下地壳基底部分熔融而形成.克布岩体中锆石的SHRIMP U-Pb锆石年龄为291±4 Ma,表明早二叠世初期华北克拉通下的底侵作用已经存在. 相似文献
7.
在青藏高原北部阿尼玛卿蛇绿岩带布青山段首次发现了埃达克岩,它们多呈不规则岩脉状侵入于布青山地区北部早古生代蛇绿混杂岩中.其岩性为花岗-英云闪长岩,主矿物有斜长石、石英、黑云母、角闪石、少量钾长石和辉石;副矿物有榍石、磷灰石、锆石和磁铁矿等.属钙碱系列,具典型（Ⅰ类、O型、HSA）埃达克岩的地球化学特征,表现为：高SiO：（63.65%～71.59%）,高Al2O3（14.81%～16.11%）,高Na2O（4.68%～5.33%）和Na2O/K2O（1.48～3.08,平均2.39）,高Sr（444.08×10^-6～560.41×10^-6）和Sr/Y（50.8～105.3）,HREE强烈亏损,低Yb（0.38×10^-6～0.74×10^-6）,高La/Yb（44.93～90.97）,弱负Eu异常（δEu=0.74～0.90）,富集大离子亲石元素（LILE）,亏损高场强元素（HFSE）,Ba、Pb正异常而Nb、P负异常.获得布青山埃达克岩的锆石TIMS U-Pb年龄为402±24Ma.布青山埃达克岩熔体来自俯冲的昆祁秦洋壳（含海洋沉积物）在石榴石角闪岩相条件下部分熔融,主要残留相为石榴石（±角闪石）.布青山埃达克岩的发现指示早古生代末期洋壳（昆祁秦多岛洋的一部分）俯冲作用的存在,俯冲方向朝北（现在方位）,此前,俯冲带发生长时间的向洋迁移,早古生代末期俯冲带已后退到阿尼玛卿蛇绿混杂岩带以南;暗示典型埃达克岩也可以形成于洋壳俯冲晚期;提示阿尼玛卿蛇绿岩带可能有与典型埃达克岩有关的Au、Ag、Cu、Mo等热液和斑岩矿床. 相似文献
8.
本文对产于冈底斯南缘一个变形花岗岩进行了主量元素、微量元素、原位锆石LA-ICP-MS U-Pb定年和锆石Hf同位素组成研究.结果表明,变形花岗岩为高硅（SiO2=73.38%～76.06%）钙碱性岩系,K2O/N%0=0.69.1.17.铝指数（A/CNK）=1.03～1.07,为弱过铝质岩石.变形花岗岩微量元素组成显示贫大离子亲石元素（e.g.Rb=47×10^-6～71×10^-6）和高场强元素（e.g.Nb=1.31×10^-6～-3.09×10^-6,Ta=0.23×10^-6 ～0.54×10^-6）,具有岛弧型花岗岩的地球化学属性.变形花岗岩锆石U-Pb年龄为178±1Ma,该年龄代表岩浆结晶年龄.锆石Hf同位素组成显示εHf（178Ma）值变化于＋14.1～＋17.7,表明变形花岗岩岩浆来自初生地壳物质的部分熔融.变形花岗岩的岩石成因与新特提斯洋向欧亚板块南缘的俯冲消减作用存在联系,其岩浆结晶年龄反映了新特提斯洋发生俯冲消减的开始时代不晚于早侏罗纪,说明了新特提斯洋经历了较长时间的演化. 相似文献
9.
SHRIMP锆石U-Pb定年表明大别山北淮阳带古碑花岗闪长岩形成于125±3Ma,而不是以前所认为的属晚侏罗世岩体.古碑花岗闪长岩的SiO2为61%～63%,K2O为3%～3.7t%,Al2O3＞15%,Mg#[100×Mg^2＋/（Mg^2＋ ＋FeT）]为45～49,具有准铝质（A/CNK=0.84～0.88）和高钾钙碱性特征.岩石富集大离子亲石元素（Sr 500×10^-6～650×10^-6,Ba 1640×10^-6～2053×10^-6）和轻稀土元素[（La/Yb）N比值为13～20],亏损高场强元素（Nb、Ta、Ti）,具有富集且均一的锶和钕同位素组成[（87Sr/86Sr）i=0.709240～0.709315,εNd（t）=-17.96～-18.05].这些地球化学特征及同位素组成与早白垩世毛坦厂组幔源火山岩及镁铁-超镁铁侵入岩很相似,表明古碑花岗闪长岩起源于富集地幔的部分熔融.该岩体的侵位可能代表了大别山强烈伸展活动的开始.大别山地区晚中生代的岩浆活动可能是古太平洋板块俯冲引起的中国东部早白垩世岩浆活动的一部分,而与三叠纪造山旋回无关. 相似文献
10.
新疆大石头-色皮口地区位于博格达造山带东段北部。该区大石头群流纹岩Rb-Sr同位素等时线年龄为306．7±2．3Ma，是博格达裂谷闭合后区域隆升阶段的产物。这些流纹岩的εNd（t）为＋5．30～＋6．40，（^87Sr／^86Sr）；为0．703289～0．703496，（^206Pb／^204Pb），为18．037～18．425、（^207Pb／^204Pb），为15．524～15．567、（^208Pb／^204Pb）；为37．198～37．810，因此其Nd-Sr—Pb同位素特征与博格达陆内裂谷伸展和沉降阶段形成的早石炭世七角井组玄武岩和流纹岩相近。七角井组与大量玄武岩伴生的少量流纹岩是由玄武岩浆分离结晶作用的产物，而大石头群中的大量流纹岩群仅与少量玄武岩伴生故是由玄武岩浆分离结晶的产物可排除大的可能性。该区流纹岩很可能是碰撞后的底侵玄武岩在地幔热量影响下发生重熔的产物。大石头群流纹岩正εNd（t）值、负εSr（t）值（低Sr初始值）和低Pb同位素比值表明博格达裂谷碰撞后的底侵幔源岩浆重熔的基性产物与碰撞前的七角井组玄武岩一样也来自亏损地幔。 相似文献
11.
Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
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. 相似文献
12.
A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US 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 the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
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. 相似文献
13.
《中国科学院院刊(英文版)》2008,22(1):2-3
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. 相似文献
14.
Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
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. 相似文献
15.
《中国科学院院刊(英文版)》2008,22(1)
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." 相似文献
16.
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. 相似文献
17.
Puay Tang 《The Information Society》1998,14(1):19-31
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. 相似文献
18.
Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
19.
Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
20.
Leah A. Lievrouw 《The Information Society》1998,14(2):83-96
The main premise of this article is that in information societies generally, and in virtual social contexts particularly, a distinctive style of interaction to facilitate the communication of difference, heterotopic communication , has emerged. It rests on two cultural foundations: an ideological belief in the positive, socially integrating power of communication, and a prevailing ethic of instrumental rationality, subjective individualism, and strategically practiced self-interest. The former is demonstrated by the use of simulation and spectacle as sources of information; exhibitionism/voyeurism as a communicative style; and the awareness of surveillance. The latter is seen in the competitive use of knowledge as a commodity; a surface globalism masking deep parochialism; lateral as well as vertical information inequity; and the use of public versus private as strategies for engagement rather than as spaces. Those who engage in heterotopic communication resort to their 'own devices' both in the sense of personal agendas, strategies, interests, and interpretations, and in the form of the telecommunication tools that help realize them. These personal and technological devices allow individuals with the right educational and technical resources to avoid exposure to disagreement, difference, or other information that does not serve their direct purposes or reflect their particular views of the world; yet they also help convey the appearance of openness, availability, and cooperation. This style of interaction is used strategically in combination with information and communication technologies to gain social or economic advantages, but it may encourage social separatism and parochialism, inhibit the negotiation of disputes, and emphasize competing interests. 相似文献