The Elements of economic geology

Bibliographic data

Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part V. Mineral fuels

Collection:: Economics Books

MINERAL OIL 281 The rock material having accumulated quickly, the organic matter was deposited with the shells and has been distilled into bitumen, which having no escape, collected in cracks or pores in the limestone. Gash veins of bitumen in lime- stone may therefore indicate no large supplies of oil, and boring for oil beneath a limestone in which the oil is indi- genous is naturally unsuccessful. Where, however, the limestones have been impregnated from below their bitu- minous veins may be a clue to underlying oil supplies. (4) Some mud volcanoes are due to the escape of petroleum vapours, which carry up with them hot mud, and pile it around the vent, as in the mud volcanoes of Burma, Trinidad, and the coast of Beluchistan. In the Baku oilfield mud hills thus formed are 1300 feet high. Carbon dioxide or sul- phuretted hydrogen denotes a volcanic origin; but a gas of the petroleum series indicates that the mound spring” is not volcanic and that petroleum may occur underground. {3) Burnt clay is sometimes due to the burning of petroleum, as in Barbados; but it may be a result of contact alteration. If the clay has been completely fused into a black glass (pseudotachylyte), the high temiperature necessary for this change may be due to the burning of producer gas generated by the action of steam upon a hot hydrocarbon. (6) Salt is such a frequent associate of oil that the two are often regarded as connected in origin. In England, and elsewhere, thick beds of salt are found without oil, but in some fields, as Ohio and Rumania, salt and oil are so intimately connected that the salt is believed to have helped in the formation of the oil. (7) The presence of sulphur is often also regarded as an indication of oil, but the association may be a coincidence. (8) The most likely part of a coalfield to yield oil has been deduced by D. White (Journ. Wash. Acad. Sci., v, 1915, pp. 189-212) for the Appalachian area and Mississippi valley, from the isovols, or lines drawn through places where the coal has the same ratio of fixed to volatile carbon. In an anthra- cite field the isovols may be above 90; some fields with isovols above 70 contain neither gas nor oil; a little of both may occur between isovols of 65-70; and oil in commer- cial quantities is found where the isovols are below 63. This method is not of universal application as some coalfields

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