Petrology and geochemistry of orthoamphibolites from the Variscan metamorphic sequences of the South Tisia in Croatia – an overview with geodynamic implications     

Jakob Pamić  Dražen Balen  Darko Tibljaš 《International Journal of Earth Sciences》2002,91(5):787-798

In the southern Pannonian Basin, the Variscan Barrovian- and overprinted Abukuma-type progressive metamorphic sequences of the South Tisia in Slavonian Mts. (SM) and Mt. Moslava)ka Gora (MG) are interlayered with orthoamphibolites. These sequences represent part of a disrupted Variscan belt that extends southeastwards of the Bohemian Massif through the Carpathians to the Caucasus. Orthoamphibolites contain hornblende (Mg-hornblende, tschermakite, pargasite, and edenite), plagioclase An_48-98 (MG) and An_26-35 (SM), biotite, grossular (MG) and almandine (SM) enriched garnet, diopside (MG), with accessory ilmenite, titanite, and clinozoisite. Based on major and trace element analyses and CIPW norms, these orthoamphibolites, which originally were olivine tholeiites to slightly alkalic basalts, can be correlated with tholeiites of consuming plate margins. '¹⁸O of orthoamphibolites varies from 5.8 to 7.1‰, the measured ⁸⁷Sr/⁸⁶Sr ratio from 0.70435 to 0.70665, which indicates slight continental crust contamination, and the calculated ratio from 0.70262 to 0.70535, indicating an upper mantle origin of the original basaltic melts. For associated penecontemporaneous I-type granitoids, the calculated initial ⁸⁷Sr/⁸⁶Sr ratio also have upper mantle values ranging between 0.70293 and 0.70368. Geochemical data for orthoamphibolites and the associated penecontemporaneous I-type granites, and the occurrence of alpine-type ultramafic bodies within the Barrovian sequence, indicate that they have many features in common with orogenic associations related to recent subduction-related settings. Some characteristic element ratios suggest back-arc basin environments and the Ce/K vs. Ce diagram suggests a pargasite-lherzolite source. Its partial melting gave primitive basaltic melts of olivine tholeiite to slight alkalic affinities that produced at first differentiated mafic rocks by olivine fractionation (future orthoamphibolites) and, afterwards, a strongly differentiated suite of I-type granitoids by amphibole fractionation. Magma emplacement and subsequent AFC processes took place in subduction environments preceding the main Variscan deformational metamorphic event during which orthoamphibolites were generated. This interpretation is compatible with geodynamic modeling of this part of the Paleotethys.  相似文献   

论构造耦合作用   总被引：17，自引：2，他引：17  

郭令智  朱文斌  马瑞士  孙岩  王锋 《大地构造与成矿学》2003,27(3):197-205

构造耦合作用是一种普遍存在的地质现象。现今东、西太平洋的构造差异及古太平洋和现今太平洋大陆边缘构造差异与俯冲的洋壳板块性状有关,即:①俯冲角度;②俯冲角度的改变;③俯冲速率;④俯冲速率的改变;⑤俯冲深度;⑥俯冲板块前缘与海沟间的水平距离;⑦俯冲板块在670km上、下地幔界线处的构造形态;⑧俯冲板块的位移及位移方向。这种深部构造活动对浅部构造形成的制约和影响,是活动大陆边缘构造耦合现象的具体表现。中国西北部的盆山耦合现象是大陆内部的构造耦合作用,印度板块与欧亚板块碰撞产生的远距离效应,导致中亚地区产生陆内A型俯冲,A型俯冲是造成盆地消亡、山系形成的重要因素。  相似文献   

A bilinear approximation of the surface relief in terrain correction computations   总被引：2，自引：2，他引：2  

D. Tsoulis  H. Wziontek  S. Petrović 《Journal of Geodesy》2003,77(5-6):338-344

A new method is presented for the computation of the gravitational attraction of topographic masses when their height information is given on a regular grid. It is shown that the representation of the terrain relief by means of a bilinear surface not only offers a serious alternative to the polyhedra modeling, but also approaches even more smoothly the continuous reality. Inserting a bilinear approximation into the known scheme of deriving closed analytical expressions for the potential and its first-order derivatives for an arbitrarily shaped polyhedron leads to a one-dimensional integration with – apparently – no analytical solution. However, due to the high degree of smoothness of the integrand function, the numerical computation of this integral is very efficient. Numerical tests using synthetic data and a densely sampled digital terrain model in the Bavarian Alps prove that the new method is comparable to or even faster than a terrain modeling using polyhedra.  相似文献   

Croatia — a coastal and maritime country     

Nikola Stražičić 《GeoJournal》1996,38(4):445-453

Croatia, through its geographic position, is a Mediterranean/Adriatic and Central European/Danube state. As an Adriatic coastal state, it has a long maritime tradition, which is apparent in its well-developed shipping (2.4 million GT), the high-quality ship-building industry (among the top six in the world) and through its numerous sea ports, of which many were established in ancient times. The leading national port is Rijeka, which is at the same time an important transit port for Austria, Hungary, Slovakia and the Czech Republic.The exceptionally indented Croatian Adriatic coast with its attractive archipelagos and favorable climatic and oceanographic conditions in the coastal sea offers very advantageous conditions for comprehensive tourist utilization. This is particularly true of nautical tourism, which is complimented by a larger number of constructed and well-equipped yachting ports/marinas on the coast and islands.  相似文献   

The Carpatho-Balkanides and adjacent area: a sector of the Tethyan Eurasian metallogenic belt   总被引：3，自引：1，他引：3  

S. Janković 《Mineralium Deposita》1997,32(5):426-433

The Tethyan Eurasian metallogenic belt (TEMB) was formed during Mesozoic and post-Mesozoic times in the area of the former Tethyan ocean on the southern margin of Eurasia, with the Afro-Arabian and Indian plates to the south. It extends from western Mediterranean via the Alps and southeastern Europe through the Lesser Caucasus, the Hindu Kush, and the Tibet Plateau to Burma and SW Indonesia, linking with the West Pacific metallogenic belt. The Carpatho-Balkan region is one of the sectors of the TEMB, characterized by some specific features. The emplacement of ore deposits is related to a definite time interval, and to specific tectonic settings such as: 1. Late Permian-Triassic intracontinental rifting along the northern margin of Gondwanaland and/or fragments already separated. This setting involves volcanogenic and volcano-sedimentary deposits (iron, lead/zinc, manganese, antimony, mercury, barite), skarn deposits associated with volcano-plutonic complexes of bimodal magmatism, and low temperature carbonate-hosted lead/zinc deposits. 2. Jurassic intraoceanic rifting – ophiolite complexes: This setting hosts major magmatic (particularly podiform chrome deposits) and volcano-sedimentary deposits, mainly of the Cyprus type. 3. Subduction-related setting involves porphyry copper deposits, lesser skarn deposits (iron, locally Pb-Zn), massive sulphide Cu (e.g. Bor) accompanied locally by Pb-Zn of replacement type, epithermal gold deposits, associated with calc-alkaline igneous complexes of the Early Tertiary-Late Cretaceous, and the Neogene gold/silver and base metals deposits. 4. Post-collision continent-continent setting includes deposits of Pb-Zn, Sb, As, Au-Cu associated with volcano-plutonic complexes of calc-alkaline affinity. Several major Alpine metallogenic units are developed in the Carpatho-Balkanides and adjacent area, each characterized by specific development, mineral associations, and types of ore deposits. Received: 3 June 1996 / Accepted: 10 January 1997  相似文献   

Influence of the Load Wavelength on the Permeability of a Viscosity Interface in the Mantle     

Čížková  Hana  Čadek  Ondřej  van den berg  Arie P. 《Studia Geophysica et Geodaetica》1997,41(1):64-72

Assuming a radially stratified Newtonian mantle in a steady-state approximation, we demonstrate that the permeability of a viscosity interface at 660-km depth strongly depends on the wavelength of buoyancy forces driving the flow. The flow induced by long-wavelength loads penetrates through the boundary freely even if the viscosity increases by two orders. In contrast, the boundary is practically impermeable for short-wavelength loads located in the upper mantle. Thus, a stepwise increase of viscosity is a significant obstacle for small descending features in the upper mantle, but huge upper mantle downwellings, or upwellings formed in the-lower mantle can overcome it easily. This indicates that certain care is necessary in interpreting the seismic structure of the mantle by means of flow models. The global tomographic image includes only the first few degrees of the harmonic series and, consequently, its interpretation in terms of a present-day flow field results in a predominantly whole-mantle circulation even for extreme viscosity contrasts.  相似文献   

Euler deconvolution using differential similarity transformations of gravity or magnetic anomalies     

Petar Y. Stavrev 《Geophysical Prospecting》1997,45(2):207-246

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Remote sensing detection of atmospheric pollutants by differential absorption LIDAR 510M/SODAR PA2 mobile system     

J. Keder  M. Střižík  P. Berger  A. Černý  P. Engst  I. Němcová 《Meteorology and Atmospheric Physics》2004,85(1-3):155-164

Summary Air pollution problem in the Czech Republic is very complex due to large number of factors as turbulent dispersion and chemical reactions concurring in the status of the PBL. For this 3D distribution of pollutants is a key information that cannot be given by conventional monitoring stations. Combined use of DIAL lidar and sodar can give access to such information. Case studies of air pollutants transport are presented using 3D concentration fields of NO₂ and ozone measured by lidar and meteorological conditions monitored by Doppler Sodar.  相似文献   

Shear and objective stress rates in hypoplasticity by D. Kolymbas and I. Herle. Author's Reply to Discussion by A. Beghini and Z. P. Bazant,R. Chambon and A. Niemunis of ‘Shear and objective stress rates in hypoplasticity’     

Alessandro Beghini  Zdeněk P. Bažant  R. Chambon  D. Kolymbas  I. Herle 《国际地质力学数值与分析法杂志》2004,28(4):365-372

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Lead-arsenic soil geochemical study as an exploration guide over the Killik volcanogenic massive sulfide deposit, Northeastern Turkey   总被引：3，自引：0，他引：3  

E. ifti  H. Kolayli  S.Tokel 《Journal of Geochemical Exploration》2005,86(1):49-59

A mountainous terrain, the eastern Pontide tectonic belt, located in northeastern Turkey, contains more than 60 known volcanogenic massive sulfide (VMS) deposits that differ in reserves (0.1–30 million tonnes) and grades. Soil geochemistry is conventionally used in exploration programs to discover concealed VMS deposits in the region. In the present study, Pb and As element pair were used as pathfinder elements to investigate the relationship of their anomalies to a completely delineated ore deposit (Killik VMS deposit) in an orientation survey that served as a natural physical model. Two hundred forty soil samples were analyzed in the present study. The two elements, which represent the opposite ends of the mobility range, revealed high contrast and overlapped each other at the location of the ore deposit due to enhancement of the anomalies by hydromorphic dispersion, which is an indication that soil samples would produce reliable results. The successful delineation of the deposit is remarkable considering the rough topography and the climatic limitations. Previously the extremely moist and temperate climate was thought to cause excessive leaching of the trace element pathfinders from the ore deposits to produce extensive anomalies usually extending away from the mineralization thus, leading to erroneous results and/or extensive anomalous areas. But the present research has shown that the method can be used effectively if the sampling and data evaluation is carefully conducted.  相似文献