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GRAVITY, MAGNETIC AND PETROPHYSICAL SURVEY OF DIFFERENT GRANITE TYPES OF THE KARLOVY VARY PLUTON
Šobotník, Petr ; Blecha, Vratislav (advisor) ; Marek, František (referee)
The thesis is a part of project "Gravity model of the Karlovy Vary granite pluton", The project is solved at the Faculty of Science, Charles University, Prague and it is supported by Grant Agency of the Czech Republic, grant 205/05/0156. The Karlovy Vary pluton is a part of larger body, The Krušné Hory Mts. pluton, which probably occurs beneath whole area of the Krušné Hory Mts. In the western part of these mountains The Karlovy Vary pluton forms a large outcrop of the granite body. The granites are source of a remarkable regional gravity low. Granites intruded in time interval of several milion years during and after a main deformation phases of the Variscan orogenesis. With regard to age, we recognize two main types and a lot of subtypes of granites. These types are different not only in their ages but also in geochemical composition. We studied if different types of granites are distinguishable also in petrophysical properties and in geophysical measurements in the field. Chosen methods were gravimetry and magnetometry. We measured a 3500 m long profile at the locality close to the Karlovy Vary town, where three types of the granites occur: Older Intrusive Complex (OIC), Younger Inrusive Complex (YIC) and transition type of the granite - microgranite (porhyric granite). Gravity measurements were...
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Temporal gravity changes related to geodynamic phenomena and geomechanical processes
Mrlina, Jan ; Blecha, Vratislav (advisor) ; Novotný, Oldřich (referee) ; Pašteka, Roman (referee)
My Thesis is based on five papers dealing with gravity changes related to various geodynamic, geomechanical and hydrological processes and phenomena. In the first part of the Thesis the gravity changes are defined as a geophysical quantity. The two principal causative parameters are highlighted - variation in elevation of the earth surface, and temporal excess of mass (negative or positive) in the subsurface. I also discuss different groups of parameters and environmental phenomena disturbing the gravity measurements, as the data accuracy is an essential condition of gravity monitoring (4D gravity). I performed a special test with the LaCoste&Romberg D-188 gravimeter in a pressure chamber with notable result showing negligible impact of small and medium size air-pressure variations on this instrument. The calibration stability was proved during two world comparison/calibration campaigns of absolute and relative gravimeters in Sevres, France. The instrument's repeatability was evaluated as 2 μGal (0.02 μm/s 2 ). As well, calibration is being controlled by measurements on the Czech latitude calibration line between Prague and Dolní Dvořiště in South Bohemia. In order to achieve best accuracy we developed special software Drift to control the gravimeter's drift. In principle the software provides a...
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Nature of magnetic anomalies on Moon, sample analysis
Kameníková, Tereza ; Kletetschka, Günther (advisor) ; Blecha, Vratislav (referee)
The magnetic properties of a rocks on Earth are mostly well known. But what is the magnetic properties of a rocks which originate extraterrestrial? Such as on Moon. We are interested in the intensity of paleofield of some Moon rocks which were chipped by Apollo 15 in early 70s. The text is an unification of the basic knowledge of a magnetism, the way how it originates. You can found here also the basics of paleomagnetism and methods how the rocks can get own magnetisation, their properties and some outline how the Moon rocks can get own magnetisation if moon doesn't have a dynamo. Then we summaries the information got from measurements of two Moon rocks 15404.219 and 15445.277, which were divided to subsamples and measured in Paleomagnetic laboratory in Czech Academy of Sciences. Each subsample was measured separately on 2G cryogenic magnetometer. We were interested in AF (alternating field) remanent magnetisation spectra from which we got an estimating intensity of paleofield from which the samples got own magnetisation. The final part is devoted to discussion on topic of possible existence of lunar dynamo or other possibilities how the Moon rocks can have held the magnetisation.
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Gravity survey of the highway route D3
Kohout, Milan ; Blecha, Vratislav (advisor) ; Mrlina, Jan (referee)
The aim of this thesis was to determine if in the area lying west of the town Jílové u Prahy occur old mine galleries, that could pose a risk for the future construction of the highway D3. The problem was solved by microgravity measurements carried out in an area of 310 x 50 m on the five profiles. There were 3 parallel profiles P15, P1 and P-15 and 2 profiles P9290 and 9180 which were perpendicular to them. The measured data were then quantitatively and qualitatively interpreted in the programs Surfer and GM-SYS. The survey located four areas of potential occurrence of galleries or tectonics lines that also appear in the area of study. Quantitative interpretation excluded the presence of the galleries in three sections. In one area was not possible to recognize if the negative anomaly in caused by old mine gallery or by the fault. Based on the interpreted data there was marked one potential risk area with possible occurrence of the old mine gallery. For more accurate information it would be necessary to make more detailed microgravity survey supplemented by electrical resistivity tomography.
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Geophysical survey of subsurface voids at locality Letonice
Bartášková, Lucie ; Blecha, Vratislav (advisor) ; Skácelová, Zuzana (referee)
The Větrníky national nature reserve, located in the South Moravian region north of the village of Letonice, is one of the largest steppe reserves in Southern Moravia. This whole area is characterized by the presence of both stable and active landslides, and the occurrence of suffosion sinkholes has been monitored there in the long-term. The aim of the thesis was to investigate whether it was possible to observe subsurface phenomena, caused by the washing out of fine rock particles by ground water, by means of geophysical methods. This phenomenon is known as suffosion. The measurements took place in the areas where the suffosion manifestation was very distinctive, that is around two sinkholes that were visible on the surface. In order to identify the suffosion structural-geological causes and their manifestations at a given location, the gravimetric and electrical resistivity tomography (ERT) methods were used in the first stage of the research. Measured data was further processed and geologically interpreted. The gravimetric method has proved suitable when identifying rocks affected by suffosion, in which case we assume that their density is lower than the density of the surrounding rocks. Using the ERT method, it was possible, in the vertical profile, to distinguish the sandy-gravelly sediments...
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Complex interpretation of gravity data focused on tectonic structure assessment and environmental projects
Mantlík, František ; Kobr, Miroslav (advisor) ; Blecha, Vratislav (referee) ; Pašteka, Roman (referee)
3 Abstract Gravimetry is an enormously expanding geophysical exploration method during the last decade. Unfortunately the gravity inversion ambiguity problem introduces the necessity to constrain gravity model parameters by other independent data. Overview of gravity data processing and interpretation is presented. All stages of the project lifecycle are discussed with emphasis to the methodological aspects and new challenges introduced by common use of modern digital zero-length spring gravimeters. Special attention is drawn on approaches used in the presented case histories projects. Description of the interpretation stage of the project concentrates on constraining of gravity model parameters with a complex of geophysical and geological data in order to reduce ambiguity of the inversion process in gravimetry. In addition, approaches used for delineation of tectonic structures, an important aspect of the interpretation stage, are described. Three case histories examples are presented to demonstrate methodological aspects of the interpretation of gravity data. They are focused on environmental problems and tectonic structure assessment. The first project represents an attempt to use micro-gravity for determination of internal structure of an undocumented sealed landfill. The second project demonstrates...
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