Geochemistry and origin of volcanic rocks of the Andes (26°–28°S)     

Jaroslav Dostal  Marcos Zentilli  Juan C. Caelles  Alan H. Clark 《Contributions to Mineralogy and Petrology》1977,63(2):113-128

Mesozoic to Recent volcanic rocks from a transect of the Central Andes between latitudes 26 ° and 28 ° South in northern Chile and Argentina show chemical and temporal zonation with respect to the Peru-Chile trench. Jurassic to Eocene lavas occur closer to the trench and are comparable to calc-alkaline rocks of island arcs. Eastwards they are followed by Miocene to Quaternary sequences of typical continental margin calc-alkaline rocks which have higher contents of K, Rb, Sr, Ba, Zr, and REE and also higher K/Na and La/Yb ratios. The rocks occurring farthest from the trench have shoshonitic affinities. The distribution of major and trace elements is consistent with a model in which magmas were derived by anatexis of an upper mantle source already enriched in LILE and located above the descending oceanic slab. It is suggested that the chemical variations across the volcanic belt reflect systematic changes in the composition of the magmas due to a decreasing degree of partial melting with increasing depth, and probably also due to the heterogeneity of the source materials.  相似文献   

Spectra and polarization characteristics of geomagneticPc4 pulsations recorded at field station štrkovec     

Střeštík  Jaroslav  Tobyášová  Marta  Hvoždara  M. 《Studia Geophysica et Geodaetica》1983,27(3):248-256

ama nm u nmam nuau aamumuuaum nau muna Pc4 n ¶rt;a u mauu m, a¶rt; a m m anam ¶rt;u amu u¶rt;a umu. n¶rt;a auum nu¶rt;a u anum¶rt; nau u u nuau aamumu mu ¶rt; u m aum amumu, u au uu m¶rt; naam. mam auam mamau amu nau Pc3 u Pi2 n ¶rt;a u mau ¶rt; u u.  相似文献   

Partitioning of transition elements between clinopyroxene and garnet     

C. Dupuy  J. Dostal  J.M. Liotard  A. Leyreloup 《Earth and Planetary Science Letters》1980,48(2):303-310

Abundances of transition elements (Ti, V, Cr, Mn, Fe²⁺, Co, Ni, Cu and Zn) in coexisting clinopyroxene and garnet are used to estimate clinopyroxene/garnet partition coefficients for these elements. The analyzed samples include eclogites, granulites and peridotites. The partition coefficients are sensitive to the major element composition of the mineral phases, although for individual transition elements they correlate with different chemical parameters. The partition coefficients of Ti correlate with the (FeO/MgO)_garnet/(FeO/MgO)_{clinopyroxene} ratio thus suggesting that the partitioning of Ti is a sensitive indicator of the physical (temperature-pressure) conditions of equilibration.  相似文献   

The effect of ordered vertical velocities and of the Earth's surface on the trajectories of particles of polluted air in the atmosphere     

Jan Bednář  Jaroslav Krabec  Ladislav Hrtoň  Reviewer Z. Jaňour 《Studia Geophysica et Geodaetica》1982,26(3):300-307

Summary The possibilities of improving of the construction of trajectories of air particles polluted by antropogeneous admixtures are discussed. With this in view attention is devoted to the ordered vertical velocities of dynamic origin and a simple method of approximate construction of the trajectories in the boundary layer of the atmosphere, where the flow is markedly affected by the Earth's surface, is discussed.  相似文献   

Geochemistry of ophiolites from the Chamrousse complex (Belledonne Massif,Alps)   总被引：1，自引：0，他引：1  

J. L. Bodinier  C. Dupuy  J. Dostal  F. Carme 《Contributions to Mineralogy and Petrology》1982,78(4):379-388

The ophiolite complex of Chamrousse (Belledonne Massif, Alps), consists of mafic to ultramafic cumulates and non-cumulates metamorphosed to amphibolite facies grade. The non-cumulitic rocks are similar in chemical composition to recent ocean-floor olivine tholeiites (both N-type and enriched P-type). The distribution of lithophile elements shows that the non-cumulitic rocks represent several magmas of different parentage. The character of the magmas varies according to the time of emplacement.Geological and geochemical data suggest that the Chamrousse complex was formed at a spreading oceanic ridge. The dynamic partial melting of an upper mantle diapir generated tholeiitic melt which decreased in amount and in REE contents. The first melt, enriched in light REE, was generated along the axis of the ridge while the second batch of melt, of lesser quantity and slightly depleted in light REE, was emplaced on the flank of the ridge. The third melt formed cross-cutting dikes with REE abundances typical of N-type (strongly light REE depleted) mid-ocean ridge basalts.  相似文献   

Trace element geochemistry of the peridotite-gabbro-basalt suite from DSDP Leg 37     

J. Dostal  G.K. Muecke 《Earth and Planetary Science Letters》1978,40(3):415-422

REE abundances in gabbros and peridotites from Site 334 of DSDP Leg 37 show that these rocks are cumulates produced by fractional crystallization of a primitive oceanic tholeiite magma. They may be part of a layered oceanic complex. The REE distributions in the residual liquids left after such a fractionation are similar to those of incompatible element-depleted oceanic tholeiites. The REE data indicate that the basalts which overlie the gabbro-peridotite complex, are not genetically related to plutonic rocks.  相似文献   

Geochemistry of calc-alkaline volcanic rocks from southeastern Iran (kouh-e-shahsavaran)     

C. Dupuy  J. Dostal   《Journal of Volcanology and Geothermal Research》1978,4(3-4)

The Upper Tertiary to Quaternary volcanic complex of Kouh-e-Shahsavaran in southeastern Iran is composed of calc-alkaline rocks of island are type (high-alumina basalts, basic andesites, andesites and dacites) even though it was emplaced on the continental basement. The volcanic rocks of the complex are genetically related and were probably derived by low-pressure fractional crystallization of high-Al basalts. The anomalously high content of Sr in some rocks probably reflects an accumulation of plagioclase. The trace element data are consistent with the origin of the parental magma by partial melting of an “enriched” upper mantle peridotite.  相似文献   

The origin of garnet-cordierite-sillimanite bearing rocks from Chandos Township,Ontario     

Jaroslav Dostal 《Contributions to Mineralogy and Petrology》1975,49(2):163-175

Garnet-cordierite-sillimanite bearing rocks from the contact aureole of the Precambrian Loon Lake pluton in Chandos Township, southeastern Ontario were analyzed for the major and rare-earth elements. In comparison with the associated Apsley biotite gneisses, they are rich in Al, Mg, and Fe, low in Si, Na, and K and their REE distribution patterns show a depletion of light REE with a negative Eu anomaly. These rocks are probably residuum left after partial melting of biotite gneiss. Leucogranite associated with the GCS rocks may represent the extracted anatectic material. It is suggested that some of the garnet cordierite-sillimanite gneisses which frequently occur in high-grade regionally metamorphosed areas of the Grenville Province of the Canadian Shield may also be of a similar residual origin as proposed by Lal and Moorhouse (1969).  相似文献   

Frequency-time analysis of geomagnetic beating-type pulsationsPc3     

Karel Prikner  Jaroslav Střeštík  Karel Dobeš  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1974,18(3):266-273

Summary The mechanism of beating of Pc3 type pulsations is studied. Using the method of numerical computation of a sonagram (the method of frequency-time analysis) a set of samples of pulsations from the Budkov Observatory is treated (1968–1969) mostly at K-indices equal to 2–3. By comparing f–t diagrams with the spectra of the samples an attempt has been made at interpreting the beating as a superposition of the frequency components, contained in the pulsation signal. In most observed cases it is possible to determine two close frequencies, the difference of which is on the average =5.4 mHz. The average carrier frequency of the samples was =37.6 mHz, and the average frequency of the beating =2.7 mHz. The interval of observed values of f_B amounted to 1–5 mHz. A tendency was observed for f_B to increase with increasing degree of disturbance of the geomagnetic field.  相似文献   

A new solar observing station     

Jaroslav Halenka 《Studia Geophysica et Geodaetica》1959,3(3):294-295

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