地球现代板块运动的天文和人卫多普勒测定     

李正心 《地球物理学报》1989,32(6):660-666

本文根据作者首次得到的全球113架光学天文仪器观测纲要的数千个星组未知数G,计算研究了1962-1982年间地球板块运动的某些方面.同时还根据1973-1983年间人卫多普勒的测量结果进行了相应的研究.这两种独立的技术其测量结果符合较好,且与地球物理和VLBI的测量结果相吻合.  相似文献   

海洋表层流模式和月尺度海气耦合试验     

钱永甫  王谦谦 《气象科学》1995,15(4):103-117

本文第一部分设计了一个海洋表层流模式，较成功地模拟出冬夏季海表层中的大尺度洋流和海面高度第二部分是月时间尺度的海气耦合试验，将海表层洋流模式和球带范围的大气模式相耦合，用数值试验讨论了洋流和海气耦合方式对模拟结果的影响。  相似文献   

Extension-related origin of magmas from a garnet-bearing source in the Los Tuxtlas volcanic field, Mexico     

Surendra P. Verma 《International Journal of Earth Sciences》2006,95(5):871-901

The Los Tuxtlas volcanic field (LTVF) of late Miocene to Recent age is a key area to understand the consequences of the current subduction of the Cocos plate beneath the North American plate, as well as the competing effects of the ongoing extension along the Gulf of Mexico coast. Geochemical and radiogenic (Sr, Nd, and Pb) isotope data are used to constrain the origin of these 7 Ma to Recent magmas in this area. The basanitic and alkaline basaltic rocks show highly steep light rare-earth element-enriched patterns implying residual garnet in their mantle source, whereas the evolved alkaline and sub-alkaline rocks have less steep rare-earth element patterns consistent with a contribution from the continental crust. Geochemical and isotope data from the LTVF are compared with those from continental rifts, extension-related areas, continental break-up regions, and island and continental arcs, including the Central American volcanic arc related to the subduction of the same oceanic plate (Cocos plate), as well as with those from the two nearby Mexican provinces [the Eastern Alkaline Province (EAP) and the eastern part of the Mexican Volcanic Belt (E-MVB)]. These data for the LTVF primitive rocks are similar to rifts, extension-related areas and continental break-up regions, including the two Mexican provinces, but different from island and continental arcs, including the northern part of the Central American Volcanic Arc (CAVA). The LTVF rocks show an unusual Th and U enrichment with respect to Ba and Rb, which also renders a distinct negative Nb anomaly (with respect to Th and K) in them. These rocks also show a negative Nb anomaly (with respect to Ba and La) that is similar to numerous rift, extension-related areas, and continental break-up regions, but distinct from all arcs around the world, indicating that the magma genesis processes in the LTVF are similar to those in rifts. The “Sr-shift”, shown to be a typical feature of most, if not all, island and continental arcs including the CAVA, is not present in the LTVF rocks. Numerous discrimination diagrams, including the new discriminant function diagrams, suggest a rift setting for the LTVF. An essentially extension-related origin of the LTVF is, therefore, inferred in this study. Furthermore, in the light of major and trace element data for LTVF primitive rocks and their modelling an incompatible element-enriched garnet-bearing source seems plausible. The LTVF source is likely to reside in the lithosphere rather than the asthenosphere although the asthenospheric contribution cannot be completely ruled out. The evolved alkaline and sub-alkaline rocks might have a lower crustal component. Finally, it appears that the LTVF shows more affinity to the EAP rather than to the Mexican Volcanic Belt (MVB), implying that the LTVF should probably be considered as a part of the EAP.  相似文献   

Microseismic activity in the Hellenic Volcanic Arc, Greece, with emphasis on the seismotectonic setting of the Santorini–Amorgos zone     

Marco Bohnhoff  Martina Rische  Thomas Meier  Dirk Becker  George Stavrakakis  Hans-Peter Harjes 《Tectonophysics》2006,423(1-4):17

The volcanic arc of the Hellenic subduction zone with its four volcanic centers is of major relevance when evaluating the seismovolcanic hazard for the Aegean region. We present results from a 22-station temporary seismic network (CYCNET) in the central Hellenic Volcanic Arc (HVA). CYCNET recordings allow to analyze the level and spatio-temporal evolution of microseismic activity in this region for the first time. A total of 2175 events recorded between September 2002 and July 2004 are analyzed using statistical methods, cluster analysis and relative relocation techniques. We identify distinct regions with significantly varying spatio-temporal behavior of microseismicity. A large portion of the seismic activity within the upper crust is associated with the presence of islands representing horst structures that were generated during the major Oligocene extensional phase. In contrast, the central part of the Cyclades metamorphic core complex remains aseismic considering our magnitude threshold of 1.8 except one spot where events occur swarm-like and with highly similar waveforms.The highest activity in the study area was identified along the SW–NE striking Santorini–Amorgos zone. Within this zone the submarine Columbo volcano exhibits strong temporal variations of seismic activity on a high background level. This activity is interpreted to be directly linked to the magma reservoir and therein the migration of magma and fluids towards the surface. NE of Columbo where no volcanic activity has yet been reported we observe a similar seismicity pattern with small-scaled activity spots that might represent local pathways of upward migrating fluids or even developing volcanic activity within this zone of crustal weakness. In contrast, the Santorini and Milos volcanic complexes do not show significant temporal variations and low to moderate background activity, respectively. Relating our results to the distribution of historical earthquakes and the GPS-derived horizontal velocity field we conclude that the Santorini–Amorgos zone is presently in the state of right-lateral transtension reflecting a major structural boundary of the volcanic arc subdividing it into a seismically and volcanically quiet western and an active eastern part.  相似文献   

Provenance of Paleozoic–Mesozoic sedimentary rocks in the Inner Zone of Southwest Japan: An evaluation based on Nd model ages     

H. Kagami  Y. Kawano  M. Akiyama  T. Ikawa  T. Imaoka  J. Ishioka  T. Toyoshima  T. Hamamoto  Y. Hayasaka  Y. Ikeda  M. Yuhara  Y. Tainosho 《Gondwana Research》2006,9(1-2):142

Nd model ages using depleted mantle (TDM) values for the sedimentary rocks in the Inner Zone of the SW Japan and western area of Tanakura Tectonic Line in the NE Japan allow classification into five categories: 2.6–2.45, 2.3–2.05, 1.9–1.55, 1.45–1.25, and 1.2–0.85 Ga. The provenance of each terrane/belt/district is interpreted on the basis of the TDMs, ¹⁴⁷Sm / ¹⁴⁴Nd vs. ¹⁴³Nd / ¹⁴⁴Nd relation, Nd isotopic evolution of the source rocks in East China and U–Pb zircon ages. The provenance of 2.6–1.8 Ga rocks, which are reported from Hida–Oki and Renge belts and Kamiaso conglomerates, is inferred to be the Sino–Korean Craton (SKC). The 2.3–1.55 Ga rocks, mostly from Ryoke, Mino and Ashio belts, are originally related with the SKC and/or Yangtze Craton (YC). The provenances of the sedimentary rocks with 1.45–0.85 Ga, from the Suo belt, Higo and some districts in the Mino and Ashio belts, are different from the SKC and YC. Especially, the Higo with 1.2–0.85 Ga is considered as a fragment of collision zone in East China. Akiyoshi belt probably belongs to the youngest age category of 1.2–0.85 Ga.Some metasedimentary rocks from the Ryoke belt have extremely high ¹⁴⁷Sm / ¹⁴⁴Nd and ¹⁴³Nd / ¹⁴⁴Nd ratios, whose main components are probably derived from mafic igneous rocks within the Ryoke belt itself and from the adjacent Tamba belt.  相似文献   

柴达木盆地北缘滩间山群火山岩及形成环境   总被引：5，自引：0，他引：5  

庄儒新  李峰 《云南地质》2006,25(2):209-217

上奥陶统滩间山群以浅变质的中基性火山岩为主，均历经不同程度蚀变，选用相对稳定的高场强元素、稀土元素及Th、Y等研究火山岩原岩组成。岩石化学和微量元素判别标志指示火山岩形成于岛弧环境。  相似文献   

Church repair swarms and earthquakes in Rhodes Island, Greece   总被引：1，自引：0，他引：1  

S. Stiros  S. Papageorgiou  V. Kontogianni  P. Psimoulis 《Journal of Seismology》2006,10(4):527-537

  相似文献   

The effectiveness of spectral similarity measures for the analysis of hyperspectral imagery     

Freek van der Meer 《International Journal of Applied Earth Observation and Geoinformation》2006

In geological imaging spectrometry (i.e., hyperspectral remote sensing), surface compositional information (e.g., mineralogy and subsequently chemistry) is obtained by statistical comparison (by means of spectral matching algorithms) of known field- or library spectra to unknown image spectra. Though these algorithms are readily used, little emphasis has been given to comparison of the performance of the various spectral matching algorithms. Four spectral measures are presented: three that calculate the angle (spectral angle measure, SAM), the vector distance (Euclidean distance measure, ED) or the vector cross-correlation (spectral correlation measure, SCM), between a known reference and unknown target spectrum and a fourth measure that measures the discrepancy of probability distributions between two pixel vectors (the spectral information divergence, SID). The performance of these spectral similarity measures is compared using synthetic hyperspectral and real (i.e., Airborne Visible Infrared Imaging Spectrometer, AVIRIS) hyperspectral data of a (artificial or real) hydrothermal alteration system characterised by the minerals alunite, kaolinite, montmorillonite and quartz. Two statistics are used to assess the performance of the spectral similarity measures: the probability of spectral discrimination (PSD) and the power of spectral discrimination (PWSD). The first relates to the ability of the selected set of spectral endmembers to map a target spectrum, whereas the second expresses the capability of a spectral measure to separate two classes relative to a reference class. Analysis of the synthetic data set (i.e., simulated alteration zones with crisp boundaries at 1–2 nm spectral resolution) shows that (1) the SID outperforms the classical empirical spectral matching techniques (SAM, SCM and ED), (2) that SCM (SID, SAM and ED do not) exploits the overall shape of the reflectance curve and hence its outcomes are (positively and negatively) affected by the spectral range selected, (3) SAM and ED give nearly similar results and (4) for the same reason as in (2), the SCM is also more sensitive (again in positive and negative sense) to the spectral noise added. Results from the study of AVIRIS data show that SAM yields more spectral confusion (i.e., class overlap) than SID and SCM. In turn, SID is more effective in mapping the four target minerals than SCM as it clearly outperforms SCM when the target mineral coincides with the mineral phase on the ground.  相似文献   

Indicator kriging applied to absorption band analysis in hyperspectral imagery: A case study from the Rodalquilar epithermal gold mining area,SE Spain     

Freek van der Meer 《International Journal of Applied Earth Observation and Geoinformation》2006

A new approach to the analysis of hyperspectral data for the purpose of surface compositional mapping is presented in this paper. We use an interpolated value of the absorption band position and the absorption band depth for the diagnostic of mineral absorption features. Using thresholds for this depth and position, the data is transformed to indicator [0,1] values. By kriging these values, we obtain the probability of exceeding certain absorption depth and the probability of a pixel exhibiting absorption features within a specified wavelength region. Using Bayesian statistics, the indicator kriging derived probabilities are used to produce a hard classification result. By adapting the prior probabilities to the dominant mineralogy in the various alteration facies mapped, data stratification is achieved. The classification results are compared to results derived using the spectral angle mapper and maximum likelihood classification. In addition, the results are statistically compared to field spectral data classified into dominant mineralogy. The indicator approach and the spectral angle mapper produce favourable results relative to field data and in comparison to the maximum likelihood classifier. A data set from the Rodalquilar high-sulfidation epithermal gold system in SE Spain, consisting of HyMAP airborne imaging spectrometer data and ASD field spectra focusing on the key minerals alunite, kaolinite, illite and chlorite, is used to illustrate the methodology.  相似文献   

中甸格咱岛弧带中酸性斑岩岩石学研究     

方学芝 《云南地质》2007,26(4):472-479

中甸格咱岛弧带是三江成矿带的重要组成部份,也是我国近年来寻找斑岩铜矿取得重大突破的矿集区之一。文中对中酸性斑岩的时空分布、岩石组合分类、岩石矿物学、岩石地球化学及岩浆演化作了研究,对含矿与非含矿斑岩作了简单对比。对该区基础研究和斑岩铜矿的寻找具有探讨意义。  相似文献