莺歌海盆地泥底辟成因、展布特征及其与天然气运聚成藏关系

泥底辟是南海北部边缘西区莺歌海盆地颇具特色的地震地质异常体，具有欠压实异常、高温高压特点及低密低速的地球物理特征，其展布则具有明显分带性且沿盆地北西走向呈近南北向雁行式排列。泥底辟成因及分布，主要受控于盆地快速沉降及高速沉积充填压实与排出流体不均衡所产生的巨大异常高温高压潜能．和区域控盆断裂晚期右旋走滑伸展活动。而晚期泥底辟热流体上侵活动及其他成藏条件的有效配置，则有效地控制了天然气及CO2运聚成藏规律。     

Cross-scale: multi-scale coupling in space plasmas

Most of the visible universe is in the highly ionised plasma state, and most of that plasma is collision-free. Three physical phenomena are responsible for nearly all of the processes that accelerate particles, transport material and energy, and mediate flows in systems as diverse as radio galaxy jets and supernovae explosions through to solar flares and planetary magnetospheres. These processes in turn result from the coupling amongst phenomena at macroscopic fluid scales, smaller ion scales, and down to electron scales. Cross-Scale, in concert with its sister mission SCOPE (to be provided by the Japan Aerospace Exploration Agency—JAXA), is dedicated to quantifying that nonlinear, time-varying coupling via the simultaneous in-situ observations of space plasmas performed by a fleet of 12 spacecraft in near-Earth orbit. Cross-Scale has been selected for the Assessment Phase of Cosmic Vision by the European Space Agency.      

南海北部白云凹陷渗漏型天然气水合物地球物理证据

根据水合物的聚集方式,海底水合物可以分为以似海底反射（BSR）为标志的扩散型水合物和无BSR的渗漏型水合物。渗漏型水合物与海底断裂、裂缝相伴。2008年,中国科学院广州水合物研究中心以渗漏型水合物成藏理论为指导,在中国科学院创新课题和国家自然科学基金广东联合基金的支持下,在南海北部白云凹陷进行了海上调查,采集了高分辨率浅层地震剖面数据,通过数据分析,发现了渗漏型水合物存在的地球物理证据。     

电离层影响下均匀半空间水平谐变电偶极子的电磁响应计算

空气介质和电离层是电导率不同的分层媒质,当研究由空气层中电流或磁矩激发的电磁场时,地面接收到的电磁波不仅受到空气介质、地下介质的影响,而且还受到电离层的影响。首先,推导出了电磁场一般边值问题,然后,将电离层、空气及地壳视为均匀、线性、各向同性的三层媒质,考虑地壳、空气、电离层的相互耦合,利用分离变量法推导求得了位于地壳表面水平谐变电偶极子的电磁响应表达式,通过这些表达式能够方便地求出电离层影响下均匀半空间空气层中的电磁场场值,同时,为后续的数值计算奠定了理论基础。     

南沙板内新生代沉积基底构造特征及其控盆机制

通过综合分析南沙海域地质地球物理资料,依照板块理论的层块思想,对南沙板内新生代沉积基底构造特征进行了剖析。在南沙板内划分出了南薇-安渡和礼乐-半月两套倾滑-层滑-走滑基底断裂系统及其所围限的相应的基底层块。从多元动力成因观出发,分析了南沙板内盆地的成因机制,提出中壳塑流作用是南沙板内盆地的主要成因动力。根据动力作用方式的不同,划分了南薇-安渡、费信-南华、礼乐-北巴拉望3个主要的板内盆地群。分别就南薇-安渡、礼乐-北巴拉望板内盆地群的成盆机制提出了“基底层块对向倾滑-拆离”和“基底层块单向倾滑-拆离”模式。本研究对全球构造分析和南沙海域油气资源勘查具有重要意义。     

华北克拉通南缘崤山地区后河岩体锆石U-Pb年代学、地球化学特征及对区域成矿潜力的启示

后河岩体位于华北克拉通南缘崤山北部,岩体侵位于太古宙太华超群地层中,主要岩性是黑云母石英二长岩和黑云母二长花岗岩。黑云母石英二长岩和黑云母二长花岗岩的锆石U-Pb年龄分别为(131.0±1.8) Ma和(127.3±1.0) Ma。地球化学特征表明二者均具有富钾(K2O/Na2O =1.00~1.51)、过铝(A/CNK =1.12~1.17)、贫镁(Mg#=26~34)的特征,属高钾钙碱性系列的过铝质花岗岩。轻重稀土元素分馏程度较高,富集轻稀土,亏损重稀土,总体富集大离子亲石元素(LILE)而亏损高场强元素(HFSE),Eu异常不明显(δEu=0.84~0.97),(La/Yb)N比值高。Hf同位素特征显示,εHf(t)具有明显的负值(-17.8~-9.5),TDM2主要集中在2.3~1.7 Ga。综上所述,早白垩世后河岩体是华北克拉通南缘加厚下地壳部分熔融的产物,形成于地壳由挤压加厚向伸展减薄转换的阶段。     

Damage identification of structures with uncertain frequency and mode shape data

A statistical method with combined uncertain frequency and mode shape data for structural damage identification is proposed. By comparing the measured vibration data before damage or analytical finite element model of the intact structure with those measured after damage, the finite element model is updated so that its vibration characteristic changes are equal to the changes in the measured data as closely as possible. The effects of uncertainties in both the measured vibration data and finite element model are considered as random variables in model updating. The statistical variations of the updated finite element model are derived with perturbation method and Monte Carlo technique. The probabilities of damage existence in the structural members are then defined. The proposed method is applied to a laboratory tested steel cantilever beam and frame structure. The results show that all the damages are identified correctly with high probabilities of damage existence. Discussions are also made on the applicability of the method when no measurement data of intact structure are available. Copyright © 2002 John Wiley & Sons, Ltd.     

A mantle-derived bimodal suite in the Hercynian Belt: Nd isotope and trace element evidence for a subduction-related rift origin of the Late Devonian Brévenne metavolcanics, Massif Central (France)

In the Brévenne Series (NE Massif Central), a low-grade bimodal association of metabasalts and metarhyolites is exposed, together with intrusive trondhjemite bodies. Zircon U-Pb dating constrains their magmatic emplacement at 366 ± 5 Ma and 358 ± 1 Ma, respectively. The metabasalts are characterized by a distinct enrichment in incompatible elements (e.g. Th and LREE) and positive ɛNd_i (from +5 to +8). Combined isotope and trace element systematics rule out crustal contamination of mafic melts as a suitable cause of the LILE (large ion lithophile element)-enrichment. Rather, a mixing process between a component similar to mid ocean ridge basalts and an enriched end-member with ɛNd_i > +5 is suggested. An enriched-mantle source of ocean island basalt affinity is precluded by the relative depletion of high field strength elements, especially Nb which shows negative anomalies in chondrite-normalized patterns. On the contrary, a subduction-related origin for the LILE enrichment would be more consistent. It may be inferred that arc-like melts [enriched in Th and LREE (light rare earth elements) and depleted in Nb, with ɛNd_i > +5] were produced through partial melting of a depleted-mantle source, to which a small amount of crustally derived component had been added. The metarhyolites are enriched in LILE, and have a close genetic relationship with the metabasalts, as evidenced by their high ɛNd_i (from +4.7 to +6.8). Although the chemical evidence remains ambiguous, it is suggested that fractional crystallization, accompanied by subordinate assimilation, is the petrogenetic process most consistent with the data. The trondhjemites are isotopically distinct from the metarhyolites. Their ɛNd_i values (from −1.0 to +2.2) reflect an important contribution of continental crust to their genesis, and disprove their inferred cogenetism with the felsic volcanics. A review of modern environments in which such bimodal suites are exposed, shows that settings involving incipient rifting of a volcanic arc fringing a continental margin, or built upon young, thin continental crust might provide suitable analogues. Geodynamic reconstructions are complicated by subsequent tectonic events which disrupted the initial patterns, and by Mesozoic-Cenozoic sedimentary cover. However, this subduction-related magmatism enlarges the growing body of evidence for southward subduction processes until the Late Devonian during the evolution of the northern flank of the European Variscides. As a general implication, it is suggested that the combined use of the Sm-Nd system with incompatible elements relatively resistant during alteration and low-grade metamorphism (REE, Th, Zr, Nb) may provide diagnostic criteria for recognizing the tectonic setting of bimodal metaigneous suites in ancient orogenic belts. Received: 21 April 1997 / Accepted: 30 June 1997     

长牡蛎两种engrailed同源基因的鉴定及其与贝壳发育相关性的研究

engrailed基因属于同源异形基因家族成员,在许多动物的分节、附肢发育、神经系统发育和贝壳形成过程中发挥作用。本研究克隆了长牡蛎两个engrailed同源基因,命名为cgi-eng1和cgi-eng2。序列分析表明,两个基因均具备典型engrailed基因保守的5个EH结构域。利用整装原位杂交技术检测了cgi-eng1和cgi-eng2在贝壳形成的关键时期早期D形幼虫时期的表达情况。结果显示,cgi-eng1和cgi-eng2 m RNA高表达于贝壳外缘,可能与早期贝壳形成过程有关。此外,两个基因的在贝壳外缘的表达模式亦有区别,提示两个基因的功能可能存在一定程度的分化。本研究首次系统鉴定了长牡蛎engrailed基因的成员,并发现它们可能均参与幼虫贝壳形成,研究结果有助于加深对贝类早期发育及贝壳形成的理解。     

东沙群岛海域的折射地震探测

综合近十多年以来在东沙群岛海域进行的反射地震资料，声纳浮标资料，双船扩长排列剖面地震测量资料及海底地震仪的折射地震资料，绘制了东沙群岛海域关于沉积层基底与地壳结构的地震地质剖面，揭示了陆架，陆坡至中央海盆之间的地壳从陆壳向洋壳的变化中，过渡睦壳具有断块构造及被拉薄的特点。