The earthquake of November 21, 1979 in NE Bohemia     

Dana Procházková  Reviewer A. Zátopek 《Studia Geophysica et Geodaetica》1981,25(2):204-207

Summary The present paper describes the macroseismic field of the earthquake which occurred in NE Bohemia on November 21, 1979. The co-ordinates of the epicentre, the focal depth, the epicentral intensity and the magnitude of the considered shock are determined on the basis of macroseismic and microseismic data.  相似文献   

Development of orthopyroxene-Fe/Mg ferrite symplectites by continuous olivine oxidation     

A. Dana Johnston  James H. Stout 《Contributions to Mineralogy and Petrology》1984,88(1-2):196-202

The development of orthopyroxene-Fe/Mg ferrite symplectites associated with olivine is discussed with respect to the chemical reactions by which they form. Previously proposed reactions are presented graphically and the differences between them are reviewed. With the exception of exsolution, these are all discontinuous reactions in the sense that olivine is replaced by the two-phase symplectite assemblage.Olivine-hosted symplectites developed in the margins of lherzolite xenoliths from Kauai, Hawaii, demonstrate a reaction mechanism which has not been previously documented from natural samples. Original Fo₉₀ olivine in these samples oxidized to a new assemblage consisting of orthopyroxene (En_92–95)-Fe/Mg ferrite (Mf_35–50) symplectites developed within more magnesian olivine (Fo_92–96) hosts. Thus, by this mechanism, olivine of a different composition persists as part of a final three-phase assemblage. As oxidation advanced, the compositions of all three product phases became continuously more magnesian and the stoichiometric coefficients of the orthopyroxene and Fe/Mg ferrite continuously increased, whereas those of the product olivine decreased in the mass-balance equations. These characteristics demonstrate that the reaction was controlled by oxygen diffusion into the xenoliths from the highly oxidized alkali picrite melt in which they were entrained. Thermodynamic calculations suggest that a gradient in oxygen fugacity of 10^0.9 bars existed across the xenolith rims and resulted in compositional gradients of 4 mol% fayalite and ferrosilite and 15 mol% magnetite.  相似文献   

Weak Earthquake of Aug. 10, 1987 connected with the Jílovice fault (Northern Bohemia)     

Dana Procházková  Reviewer J. Zahradník 《Studia Geophysica et Geodaetica》1989,33(1):97-100

Summary The paper describes the seismic activity of the Jílovice fault and the last earthquake of Aug. 10, 1987.

---

Резюме Оnuсывaеmся сеŭсмuческaя aкmuвносmь рaзломa йuловuце в северовосmочноŭ Чехuu u землеmрясенuе с 10-о о aв усma 1987 , очa коmоро о был связaн с ?rt;aнным разломом.

  相似文献   

Geochemical aspects of some accumulation models for primary magmas     

Sven Maaløe  A. Dana Johnston 《Contributions to Mineralogy and Petrology》1986,93(4):449-458

The compositions of primary magmas depend to some degree on the dynamic processes occurring in the partially molten region of the mantle. The compositional dependence is estimated for three models which assume either accumulation from a migmatized source region or accumulation entirely by the interstitial flow of magma. Accumulation from a migmatised region results in magmas with higher concentrations of incompatible elements than does batch melting, whereas accumulation by interstitial flow results in magmas with lower concentrations of these elements. The concentrations of refractory elements are almost independent of both the accumulation process and the degree of partial melting and are therefore usefull for the identification of primary magmas.  相似文献   

A steady-state model of a cumulus cloud,describing phase transitions by kinetic equations. I. model pattern     

Ivana Nemešova  Dana Lakomá  Reviewer O. Zikmunda 《Studia Geophysica et Geodaetica》1974,18(3):274-297

  相似文献   

Experimental studies of the <Emphasis Type="Italic">P</Emphasis>–<Emphasis Type="Italic">T</Emphasis>–H<Subscript>2</Subscript>O near-liquidus phase relations of basaltic andesite from North Sister Volcano,High Oregon Cascades: constraints on lower-crustal mineral assemblages     

Celestine N. Mercer  A. Dana Johnston 《Contributions to Mineralogy and Petrology》2008,155(5):571-592

We have mapped the mineralogy onto the H₂O-undersaturated liquidus surface of basaltic andesite from North Sister Volcano to constrain the crystalline assemblage with which, and P–T–H₂O conditions at which, the melt last equilibrated before erupting. Combining our high pressure experimental results with examples of tectonically exposed lower arc crust, geophysical constraints, trace element geochemistry, and melt inclusion volatile contents, we conclude that an anhydrous, augite-rich gabbro at ∼12 kbar and ∼1,175°C is the most probable lithology with which North Sister basaltic andesite with ∼3.5 wt% H₂O last equilibrated before erupting. We speculate that reaction between this gabbro and primitive mantle-derived precursor melts buffered the compositions of magmas erupted from this volcano resulting in their remarkably limited compositional range.  相似文献   

Learning from mistakes in climate research   总被引：1，自引：0，他引：1  

Rasmus E. Benestad  Dana Nuccitelli  Stephan Lewandowsky  Katharine Hayhoe  Hans Olav Hygen  Rob van Dorland  John Cook 《Theoretical and Applied Climatology》2016,126(3-4):699-703

  相似文献   

Terrane character of the north-east margin of the Moldanubian Zone: the Kutná Hora Crystalline Complex,Bohemian Massif     

Jaroslav Synek  Dana Oliveriová 《International Journal of Earth Sciences》1993,82(3):566-582

Three major allochthonous units have been distinguished on the north-eastern border of the Moldanubian Zone, which differ each from other in lithology and structural and metamorphic evolution. Their present day position displays significant metamorphic and structural inversion resulting from progressive nappe stacking during the Variscan orogeny. The uppermost-Gföhl Unit consists of anatectic rocks containing high temperature/high pressure relics, i.e. granulites, eclogites and garnet peridotites. The rocks of the Gföhl Unit were strongly mylonized during uplift and later also extensively migmatized in the kyanite stability field. The Kouiim Nappe is built up by a sequence of fine-grained leucocratic migmatites with preserved relics of a pre-Variscan deformation event. This event was terminated by the intrusion of coarse-grained porphyritic granites, converted into augen orthogneisses by the Variscan orogeny. The lowermost Micaschist Zone was formed from a sequence of metapelites intercalated with diopsidic amphibolites.During uplift from deep crustal zones the Gföhl Unit cut off a thick slice of the basement crustal material represented by the Kourim Nappe. The quartzo-feldspathic material of the Kourim Nappe acted as a major shear interface because of its extreme ductility under the conditions found in the middle crust. This process occurred under amphibolite facies metamorphism. The continuous uplift of the nappe pile induced another crustal segment in the nappe stack, represented by the Micaschist Zone. The whole nappe sequence was then thrust over the Moldanubian Zone. A westward sense of shear is suggested for the whole uplift history. The kinematic pattern was complicated by later strike-slip ductile faults which finished the recent geological configuration.Correspondence to: J. Synek  相似文献   

Factors influencing spatial and annual variability in eelgrass (Zostera marina L.) meadows in Willapa Bay, Washington, and Coos Bay, Oregon, estuaries     

Ronald M. Thom  Amy B. Borde  Steven Rumrill  Dana L. Woodruff  Gregory D. Williams  John A. Southard  Susan L. Sargeant 《Estuaries and Coasts》2003,26(4):1117-1129

Environmental factors that influence annual variability and spatial differences (within and between estuaries) in eelgrass meadows (Zostera marine L.) were examined within Willapa Bay, Washington, and Coos Bay, Oregon, over a period of 4 years (1998–2001). A suite of eelgrass metrics were recorded annually at field sites that spanned the estuarine gradient from the marine-dominated to mesohaline region of each estuary. Plant density (shoots m^?2) of eelgrass was positively correlated with summer estuarine salinity and inversely correlated with water temperature gradients in the estuaries. Eelgrass density, biomass, and the incidence of flowering plants all increased substantially in Willapa Bay, and less so in Coos Bay, over the duration of the study. Warmer winters and cooler summers associated with the transition from El Niño to La Niña ocean conditions during the study period corresponded with this increase in eelgrass abundance and flowering. Large-scale changes in climate and nearshore ocean conditions may exert a strong regional influence on eelgrass abundance that can vary annually by as much as 700% in Willapa Bay. Lower levels of annual variability observed in Coos Bay may be due to the stronger and more direct influence of the nearshore Pacific Ocean on the Coos Bay study sites. The results suggest profound effects of climate variation on the abundance and flowering of eelgrass in Pacific Northwest coastal estuaries.  相似文献   

Theoretical model for the formation of ion-pairs in seawater     

Dana R. Kester  Ricardo M. Pytkowicz   《Marine Chemistry》1975,3(4):365-374

Predictions of association constants for ion-pair formation in seawater were compared to measured constants as a test for the existence of ion-pairs. A fair agreement was obtained in most cases, although the theoretical electrostatic calculations indicate that significant chloride ion-pairing should occur which has not been observed in most experimental investigations.  相似文献