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 279 ents of ordinary animals and plants. True oil shale contains no oil, but organic residues which, when heated in a retort, are converted into oil. According to the organic theory mineral oil is similarly produced from the organic matter in sedimentary deposits. Oil comes from beds charged with organic material and is only found in igneous rocks which have been injected with it from sedimentary rocks. Pockets and trickles of petroleum are frequently met with in the igneous rocks of the Scottish oil-shale field, but only where the oil may have been distilled out of shales; the field of Bacur- anao in Cuba is fed from an serpentine, which has doubtless been impregnated from sediments. That the mineral oil was not formed synthetically is shown by its optical properties. Synthetic oil does not cause circular polarization, but mineral oil does. Its circular polarization is sometimes attributed to the presence of some organic oil—cholesterol (Ca5H,40), which is familiar as lanoline and is an animal product, or phytosterol, a corre- sponding oil derived from plants. According to this im- probable suggestion mineral oil is partly inorganic and partly organic. Most authorities agree that mineral oil is of organic origin, but there is wide difference of opinion as to whether it is mainly vegetable or animal. Its frequent association with coal and lake deposits is advanced in support of its vege- table origin; but large quantities come from Silurian and Ordovician rocks that are earlier than any land vegetation that would have produced spores and seeds. Animal tissues can be distilled into oil similar to petroleum, and most of the organic matter in many oil-producing beds is more likely to be animal than vegetable. The Scottish oil shales contain abundant fossil fish and entomostraca, and many fields obtain their oil from shales rich in foraminifera and other animals. The constant association of fish with oil deposits has indeed led J. H. Macfarlane to claim in a volume entitled Fishes, the Source of Petroleum (1923, p. 414), not only that petroleum is wholly of animal origin, but that fish alone are its source. Petroleum is probably derived from both plants and animals,"and animals appear to contribute the larger share. The quick accumulation of thick masses of sediment rich

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