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Eugen Vujić Giuliana Verbanac Stanislav Francisković-Bilinski Vladis Vujnović Antun Marki 《Studia Geophysica et Geodaetica》2011,55(1):175-190
Based on the ground survey of total-field magnetic data at 53 sites, which recorded a time-series over the interval 2003–2005,
the core field + long wavelength lithospheric field over the middle-northern Croatia region was calculated. The area of the
survey was 18900 km2, an average distance between the neighbouring sites being 12 km. The results were reduced to 2004.5 epoch. This “normal”
total-field was estimated using the firstorder Taylor polynomial as a function of geographic coordinates, and the polynomial
coefficients were calculated with three methods of adjustment: simple and weighted least squares fits and adjustment according
to the most frequent value. The stability of the normal field was tested using the Monte Carlo-type test, by decreasing the
input data set in each adjustment (up to 90%). All obtained field residuals (measured-“normal”) were mutually compared, as
well as fit coefficients of the Taylor polynomials. The residual values indicate the presence of shorter-wavelength anomalies,
specifically three major residual anomalies were found (−106 nT, 74 nT and 57 nT). The geostatistical analysis of the ground
survey data and the normal field residuals (respectively), using the median absolute deviation method, was further conducted
in order to evaluate the calculated anomalies. The geological situation around the anomalies derived by the median absolute
deviation method, and around the normal field residual anomalies, is given. The correlation was found between higher value
anomalies of the normal field residuals, and shallow volcanic rocks and oil field, respectively. 相似文献
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Stable carbon‐isotope record of shallow‐marine evaporative epicratonic basin carbonates,Ordovician Williston Basin,North America 
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下载免费PDF全文 Secular variations in stable carbon‐isotope values of marine carbonates are used widely to correlate successions that lack high‐resolution index fossils. Various environmental processes, however, commonly may affect and alter the primary marine carbon‐isotope signal in shallow epicratonic basins. This study focuses on the marine carbon‐isotope record from the carbonate–evaporite succession of the upper Katian (Upper Ordovician) Red River Formation of the shallow epicratonic Williston Basin, USA. It documents the carbon‐isotope signal between the two major Ordovician positive shifts in δ13C, the early Katian Guttenberg and the Hirnantian excursions. Eight δ13C stages are identified based on positive excursions, shifts from positive to negative values and relatively uniform δ13Ccarb values. A correlation between carbon‐isotope trends and the relative sea‐level changes based on gross facies stacking patterns shows no clear relation. Based on the available biostratigraphy and δ13C trends, the studied Williston Basin curves are tied to the isotope curves from the North American Midcontinent, Québec (Anticosti Island) and Estonia, which confirm the Late Katian age (Aphelognathus divergens Conodont Zone) of the upper Red River Formation. The differences in the δ13C overall trend and absolute values, coupled with the petrographic and cathodoluminescence evidence, suggest that the carbon‐isotope record has been affected by the syndepositional environmental processes in the shallow and periodically isolated Williston Basin, and stabilized by later burial diagenesis under reducing conditions and the presence of isotopically more negative fluids. 相似文献
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Eugen Vujić Giuliana Verbanac Vladis Vujnović Antun Marki 《Studia Geophysica et Geodaetica》2009,53(4):497-517
During the time interval 2003–2005 a ground survey of the total magnetic field intensity in the middle-northern part of Croatia
was performed, in order to get a detailed insight of the field distribution over the region. A special effort was done to
understand the uncertainty and errors in data reduction, namely different amplitudes of the diurnal variations and different
secular variations at the ground stations with respect to the observatories. For data reduction to epoch 2004.5 the total
field recordings from AQU, FUR, NCK and THY geomagnetic observatories have been used. We estimate the mean determination error
to be one order of magnitude smaller than the maximal reduction error. Multiple linear regression and the method of empirical
orthogonal functions were applied on the ground survey and observatory time series. This allowed us to explain the correlations
among them and the variance of the total field. Furthermore, we identified two sources of serious artificial disturbances
caused by DC leakage: the tramway system of the capital and one railway station in neighbouring Slovenia. Also, we estimate
the region free of these disturbances. The magnitude of one of them is estimated to be more than five nT at the distance of
about 10 km. 相似文献
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Zusammenfassung Erze aus zwei Versuchsbauen auf Cu, Ni, Co und Edelmetalle wurden mikroskopisch und mit der Mikrosonde untersucht. Die Schürefe liegen an einer riesigen Bewegungszone im Serpentin in Süd-Cypern. Die höchst ungewöhnliche Paragenese zeigt starke, auf geringste Erstreckung wechselnde Umbildungen. Die Vorkommen selbst sind durch reichlichen bzw. sehr zurücktretenden Anteil an Pyrrhotin verschieden. Träger von Cu ist neben Chalkopyrit Cubanit und sehr reichlich valleriit; von Ni-Pentlandit, Heazlewoodit, Mackinawit, Oregonit; von Co zwei wahrscheinlich neue As-arme Co-Arsenide. Begleiter sind u.a. Pyrrhotin, Chromit, Magnetit, Graphit und Molybdänit, an Gangarten vorwiegend Serpentinmineralien, wenig Carbonate. — Die Lagerstätten geben Gelegenheit, die seltenen Mineralien Mackinawit, Valleriit und Oregonit nebeneinander im Verband und in ihren Beziehungen zu Pentlandit und Chalkopyrit zu untersuchen. Die Mineralisation scheint während der tektonischen Veränderung des Serpentins erfolgt zu sein.
Ores from two claims tested for Cu, Ni, Co and noble metals were examined microscopically and by using the microprobe. The deposits are connected with an enormous fault in ultrabasic rocks in southern Cyprus. The very exceptional association varies in strong alterations over shortest distances. The deposits differ regarding the high and low content of pyrrhotite. Cu-bearing minerals are cubanite and abundant valleriite; Ni-bearing ones pentlandite, mackinawite, oregonite, heazlewoodite; Co is present in two, very probably new arsenides of Co, low in As. — Further are present: Pyrrhotite, chromite, magnetite, graphite, and molybdenite, and as gangue serpentine-minerals and some carbonate. — The deposits give the opportunity to study the rare minerals mackinawite, valleriite, and oregonite together and in relation to pentlandite and chalcopyrite, The mineralisation appears to have occurred during the tectonic movements of the serpentine.相似文献
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