GEOPHYSICAL RESEARCH, 2018, vol. 19, no. 3, pp. 23-40. https://doi.org/10.21455/gr2018.3-2
UDC 550.838.2, 550.837.32
Abstract References Full text (in Russian)
FRACTAL PROPERTIES OF GEOPHYSICAL DATA ARRAYS USING THE TWO-DIMENSIONAL WAVELET ANALYSIS: MAGNETIC AND GEOELECTRICAL SURVEY IN THE MONCHEGORSK ORE REGION
V.A. Lubchich
Polar Geophysical Institute, Murmansk, Russia
Abstract. The article deals with the investigation of fractal properties of geophysical data arrays, obtained in the Monchegorsk ore region as a result of areal magnetic surveys and geoelectrical surveys by the method of small-scale charge. The ore region is located in the Central part of the Pechenga-Varzugskaya riftogenic structure. This circumstance causes the presence of the hierarchically organized system of tectonic dislocations of various scales and directions in the region. Main structural longitudinal axial faults of the North-West direction and transform faults of the North-East direction together with concomitant tectonic zones of smaller scales control the placement of intrusive massifs of basic-ultrabasic rocks and define the structure of deposits and occurrences of rich epigenetic copper-nickel ores, thus forming the Monchegorsk ore-magmatic system of the Central type. The hierarchical organization of geological systems determines fractal properties of geophysical data arrays, obtained in the result of areal measurements on these systems. So the network of tectonic faults is displayed in geophysical fields as the set of anomalous zones with the high electrical conductivity. The fractal dimension of this set, estimated by the cell method, is df =1.38±0.02. Moreover ore zones are clearly displayed in the magnetic field due to the wide spread of magnetic ore minerals such as pyrrhotite and magnetite. It was shown on the example of magnetic survey data in the Monchegorsk ore region, that the two-dimensional wavelet analysis is useful tool to study fractal properties of geophysical data arrays. The application of the wavelet analysis allows to detect the hierarchical structure of organization of the whole geological system and to conclude about its local properties, for example, ore prospects of separate areas. The average value of local singularity exponents al, calculated for separate ridges of the skeleton of the wavelet transform, may be used as the quantitative characteristic of the magnetic field inhomogeneity within the investigated area. Zones, promising discovery of rich epigenetic copper-nickel ores, are characterized by the strongly inhomogeneous magnetic field, and corresponding local singularity exponents have smaller values. Areas with the predominantly low and medium level of disseminated mineralization are characterized by the more homogeneous magnetic field, and corresponding local singularity exponents are close to unity.
Keywords: copper-nickel ore, tectonic fault, magnetic field, the method of small-scale charge, fractal dimension, wavelet transform, local singularity exponent.
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