PhasesLg etRg observées à Praha     

Karel Pěč 《Studia Geophysica et Geodaetica》1961,5(3):219-226

  相似文献   

Tin–polymetallic sulfide deposits in the eastern part of the Dachang tin field (South China) and the role of black shales in their origin   总被引：3，自引：0，他引：3  

Pašava  Jan  Kříbek  Bohdan  Dobeš  Petr  Vavřín  Ivan  Žák  Karel  Delian  Fan  Tao  Zhang  Boiron  Marie-Christine 《Mineralium Deposita》2003,38(1):39-66

The Dafulou and Huile vein and stratabound cassiterite-sulfide deposits and sheeted ore veins at the Kangma cassiterite-sulfide deposit are located in the eastern part of the Dachang tin field. These deposits are hosted in a sedimentary sequence containing significant concentrations of organic matter in the form of Lower Devonian calcareous black shales and hornfels. These rocks together with the younger intrusion of Longxianggai granite (91DŽ Ma) actively participated in the formation of Sn-polymetallic deposits. The following three major stages have been distinguished in stratiform and vein-type orebodies at Dafulou, Huile and Kangma: stage I (cassiterite, pyrrhotite, arsenopyrite, tourmaline, carbonate), stage II - main sulfide stage (quartz, cassiterite, arsenopyrite, pyrrhotite, sphalerite, stannite, pyrite, carbonates) and stage III (native Bi, galena, electrum, sulfosalts). Stage IV (post-ore), recognized at Huile is represented by barren carbonates and zeolites. Whole rock geochemistry has revealed that at Dafulou, Bi and Cu correlate strongly with S, whereas V and Pb correlate well with C_org (organic carbon). The similar distribution patterns of selected elements in average slightly mineralized low-Ca black shales indicate a fluid composition similar for all deposits studied. Studies of graphitization of the organic matter in black shales adjacent to orebodies indicate that d₍₀₀₂₎ and FWHM (full width in half maximum)/peak height values gradually decrease in the following sequence: Dafulou deposit M Kangma deposit M Huile deposit. The pyrolysate of wall rocks at the Dafulou deposit is relatively enriched in asphaltenes and maltenes (55.6-72.0% of the pyrolysate) comparable with pyrolysate obtained from more distal black shales (19.2-28.5%). Typical GC-MS spectra of pyrolysate from distal black shales are dominated by alkanes in the n-C15 to n-C25 range, aromatic molecules being represented mostly by alkyl-naphthalenes. In contrast, only traces of aliphatic hydrocarbons in the n-C14 to n-C18 range and elemental sulfur were identified in pyrolysates from pyrrhotitized wall rocks. The earliest fluid inclusions of the studied system occur in the quartz-tourmaline-cassiterite assemblage of stage I at Dafulou. These inclusions are H₂O-CO₂-CH₄-rich, with 10 to 20 vol% of aqueous phase. P-T conditions of the trapping of inclusions are estimated to be up to 400 °C and 1.3 to 2.0 kbar (between 5.0 and 7.5 km under lithostatic pressure). In contrast, the presence of a low density gaseous CO₂-CH₄ phase indicates relatively low pressures during the formation of the breccia-type quartz-calcite-cassiterite-sulfide mineralization (stage II), when P-T conditions probably reached approx. 380 to 400 °C and 0.6 kbar (up to 6 km under hydrostatic pressure). Fluid inclusion data and oxygen isotope thermometry indicate that cassiterite-sulfide ores of the main sulfide stage (stage II) formed from aqueous-carbonic fluid (CO₂/CH₄ =ᄺ) at temperatures of up to 390 °C at Dafulou and in a temperature range of 250 to 360 °C at Huile and 260 to 370 °C at Kangma. The '³⁴S values of sulfides from Dafulou range mostly between -1 and -6‰, whereas sulfides from the Kangma and Huile deposits are characterized by more negative '³⁴S values (between -8 and -11‰, and between -9 and -12‰, respectively). These data suggest that bacteriogenic sulfides of black shales were a dominant source of reduced sulfur for epigenetic (vein and replacement) mineralization. Oxygen isotopic compositions of five quartz-cassiterite pairs from Dafulou and Huile show a relatively narrow range of calculated oxygen isotope temperatures (250-320 °C, using the equation of Alderton 1989) and high '¹⁸O_fluid values between +8 and +10‰ (SMOW), which are in agreement with fluid derivation from and/or high temperature equilibration with the Longxianggai granite. The carbon and oxygen isotope composition of carbonates reflects variable carbon sources. Stage I calcite is characterized by narrow ranges of '¹³C (-7.0 to -9.5‰ PDB) and '¹⁸O (+15.0 to +17.5‰ SMOW). This calcite shows ubiquitous deformation, evidenced by intense development of twins. Fluid compositions calculated at 330 °C for the Dafulou and Huile deposits and at 270-300 °C for the Kangma deposit ('¹⁸O_fluid between +10.0 and +11.5‰ SMOW, '¹³C_fluid between -5.5 and -7.5‰ PDB), agree with fluid derivation from and/or equilibration with the peraluminous, high-'¹⁸O Longxianggai granite and suggest a significant influence of contact metasedimentary sequences (carbon derived from decomposition and/or alteration of organic matter of calcareous black shales). The '¹³ C values of organic matter from the Lower to Upper Devonian host rocks at the Dafulou deposit (-24.0 and -28.0‰) fit with a marine origin from algae. However, organic matter adjacent to the host rock-ore contact displays a slight enrichment in ¹³C. The organic carbon from the Huile and Kangma deposits is even more ¹³C enriched (-24.6 to -23.5‰). The most heavy '¹³ C values (-16.5‰) were detected in hornfels sampled at the contact of the Upper Devonian sediments with the Longxianggai granite. The '¹³C data broadly correlate with the degree of structural ordering (degree of graphitization) of organic matter, which indicates that both variables are related to thermal overprint.  相似文献   

КРИТИКА     

Karel Pěč 《Studia Geophysica et Geodaetica》1979,23(1):100-101

  相似文献   

Sensitivity of the Sharpe and Worden gravity meters to vertical motion     

Vladimír Tobyáš  Karel Diviš  Reviewer O. Novotný  Reviewer Z. Šimon 《Studia Geophysica et Geodaetica》1979,23(2):122-130

Summary Using the least-squares method the constants of both gravity meters — seismometers — were derived from the amplitude responses, observed under vertical motion on a vibrating table in the 0.3–30 s range. The values of the seismogram amplitudes, above which seismic waves cause an observable displacement of the gravity meter reading beam, were determined for the SKD and Press-Ewing station seismographs.  相似文献   

Estimate of the effect of vibrations on quartz gravity meters     

Vladimír Tobyáš  Karel Diviš  Reviewer M. Pick 《Studia Geophysica et Geodaetica》1978,22(4):336-347

Summary Relations for computing the minimum amplitudes of ground vibrations which generate oscillations of the gravity meter reading beam at the limit of the resolution of the optical system, have been derived. The minimum amplitudes in the ground displacement period range of0.1 to10 s, for the assumed values of the fundamental parameters of quartz gravity meters (i.e. the periods and damping constants of the pendulum and the mechanico-optical magnification of the pendulum deflections), range from tenths of a micrometre to units of micrometres. Larger displacement amplitudes, due to, e.g., earthquakes and traffic, disrupt gravity measurements.  相似文献   

Graphs for determining small epicentral distances by means of acoustic waves     

Karel Holub 《Studia Geophysica et Geodaetica》1968,12(3):329-332

  相似文献   

Electroacoustic transducers for seismic modelling     

Karel Klíma  Zdeněk Pros  Alena Knoblochová 《Studia Geophysica et Geodaetica》1966,10(3):323-333

  相似文献   

Joint interpretation ofLg andSa waves based on spectral amplitudes of higher love wave modes     

Karel Pěč  Oldřich Novotný  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1977,21(3-4):242-248

Summary The joint interpretation of Lg and Sa waves has been carried out on the basis of the first higher mode of Love waves. A characteristic feature of the spectral amplitude curve for the first higher mode is the existence of two pronounced maxima separated by a gap. The short-period maximum may be related to the Lg wave, the long-period to the Sa wave.  相似文献   

The effect of the magnetic field on the accuracy of measurements with Worden and Sharpe gravity meters     

Karel Diviš  Vladimír Tobyáš  Reviewer Z. Šimon 《Studia Geophysica et Geodaetica》1976,20(4):338-345

Summary The effect of an additional homogeneous magnetic field with an intensity of 0–4.5 Oe on the Worden quartz gravity meter No. 961 and on Sharpe quartz gravity meters Nos 173 and 174 was tested. Whereas no effect was observed with the Worden gravity meter, the magnetic field had a measurable effect on both the Sharpe gravity meters. The largest deviation of the reading beam is caused by the horizontal component of the magnetic field which acts in the plane of oscillation of the gravity-meter arm. The Sharpe gravity meter No. 173 is considerably sensitive; a field of 0.2 Oe intensity, corresponding to the magnitude of the horizontal component of the geomagnetic field in mid-latitudes, causes an error in the measurement of gravity of as much as 0.08 mGal. With a view to the different behaviours of the individual quartz gravity meters of the same type in a magnetic field, it should prove expedient to carry out check measurements with all gravity meters and, with regard to the sensitivity of the gravity meter to the magnetic field and the required accuracy of the gravity determination, take into account this perturbing factor in field measurements, as well as laboratory tests of gravity meters.  相似文献   

HM-wave filtration in a horizontally stratified earth's magnetosphere     

Karel Prikner  Reviewer G. Siráň 《Studia Geophysica et Geodaetica》1976,20(1):39-51

Summary The model of filtration of a linearly polarized HM-wave in a system of three homogeneous layers, limited by two halfspaces and treated in[1], is generalized. The wave attenuation is considered in all inner layers of the system and the model is applied to the filtration of HM-waves in the lower layers of the magnetosphere, i.e. in the ionosphere. The nature of the changes of the functional dependences is studied, i.e. of the amplitude coupling factor on the frequency under variation of the fundamental parameters, defining the filtering medium. Filtration models are demonstrated and discussed for the periods of maximum and minimum solar activity during daytime and at night. The relation between the properties of filtration and the possibilities of observing geomagnetic pulsations on the Earth's surface is pointed out.  相似文献