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Magnetic investigation and 2½ D gravity profile modelling across the Beattie magnetic anomaly in the southeastern Karoo Basin, South Africa

Baiyegunhi Ch., Gwavava O.

Acta Geophysica

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2017

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Vol. 65, no. 1

119--138

EN

The southeastern Karoo Basin is considered to be one of the most prospective areas for shale gas exploration in South Africa. An interesting magnetic anomaly, the Beattie magnetic anomaly (BMA), and geologic intrusions are seen on the magnetic map. To date, the source of the BMA and interconnectivity of the igneous intrusions are not well understood. In this study, we investigate the interconnectivity of the igneous intrusions and possible location of the source of the BMA using gravity and magnetic methods. The gravity model results showed that igneous intrusions are interconnected at depth, which probably pose threat by increasing the risk of fracking the Karoo for shale gas exploration. The magnetic results revealed that the BMA becomes stronger with depth. The average depths to the top of the shallow and deep magnetic sources were estimated to be approximately 0.6 and 15 km, respectively.

2

An effect of igneous intrusion on the structure, texture and microtexture of coal from the Sośnica coal mine, Upper Silesian Coal Basin, Poland

Smędowski Ł., Duber S., Matuszewska A.

Geological Quarterly

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2015

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Vol. 59, No. 3

507--516

EN

Two coal samples from the Sośnica coal mine, Poland, were analysed in this study. One sample was the natural char collected at the contact of magmatic intrusion, and another sample was the raw coal that was pyrolised in a laboratory furnace. Temperature of pyrolysis was similar to that calculated for the intrusion. The obtained char was analysed to compare its features with those characterizing a natural char sample. Optical microscopy, transmission electron microscopy and Raman spectroscopy studies show that the char from unaltered coal is characterized by the least developed structure, texture and microtexture compared to the natural char. Hence, it can be concluded that geological pressure generated by both the intrusion and the overburden, strongly affects the process of molecular ordering that took place during the heating of coal. The textural, structural or microtextural parameters of coal cannot be used as a geo-thermometer, because they are strongly dependent not only on the temperature but also on other factors.

3

Preliminary results of geochemical and petrographic investigations of hard coal from mine "Sośnica", heat-affected by igneous intrusion

Matuszewska A.

Zeszyty Naukowe. Górnictwo / Politechnika Śląska

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2003

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z. 257

109-129

EN

The preliminary results are presented of geochemical and petrographic investigations of coal from 416-bed of hard coal mine "Sośnica" (Upper Silesia Basin), heat-affected by igneous intrusion. The geochemical parameters were estimated on the basis of the mass chromatograms obtained with the use of GC/MS method for hydrocarbon fractions of the molecular phase of coal. For diversification of the chemical structure in a function of the distance of sampling of the parent coals from intrusion, the most useful were parameters basing on aromatics, of various degree of alkyl substitution and condensation . The aromatisation process of coal structure is in turn a reason of variations in physical coal properties, as e.g. Increasing of vitrinite reflectance. The degree of thermal transformations of coal organie matter may be also characterised well by changes occurring of amounts of dibenzothiophene type compounds. Their presence , as well as some geochemical And mineralogical data, can indicate, moreover, the hydrothermal conditions of transformations in the zone of heat flow of intrusion.

PL

Przedstawiono wstępne wyniki badań geochemicznych i petrograficznych węgla z pokładu 416 w KWK "Sośnica" (GZW), który uległ przeobrażeniu termicznemu pod wpływem intruzji magmowej.Parametry geochemiczne wyznaczono na podstawie chromatogramów masowych wykonanych przy użyciu metody GC/MS dla węglowodorowych frakcji fazy molekularnej węgli. Najlepszą charakterystykę zmian chemicznej struktury w funkcji odległości pobrania węgli macierzystych ód intruzji uzyskano, stosując wskaźniki określające zmiany zawartości węglowodorów aromatycznych o różnym stopniu kondensacji i substytucji podstawnikami alkilowymi. Proces aromatyzacji węglowej struktury jest z kolei przyczyną zmian obserwowanych we własnościach fizycznych węgla, m.in. Wzroście refleksyjności witrynitu. Stopień termicznych przemian organicznej substancji węgla charakteryzują także wskaźniki wykorzystujące zmiany zawartości związków z grupy dibenzotiofenu, których obecność możewskazywać ponadto, obok niektórych danych geochemicznych i mineralogicznych, na hydrotermalne warunki przeobrażeń węgla w strefie strumienia intruzji.