The Elements of economic geology

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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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Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

ORES OF GOLD 63 others by Becker (Ann. Rep. U.S.G.S., 1896-7, pp. 163-7), and restated with explanation of the two chief difficulties by the author in 1907 (Tr. I.M.M., xvii, pp. 2-41). It has been fully confirmed by the detailed survey of the field by E. T. Mellor (Tr. G. Soc. S. Afr., xiv, xvi, xviii, 1911-15) of the Geological Survey of South Africa, and the work by R. B. Young (The Banket, 1917). The Banket of the Gold Coast Is also a placer, according to Sir A. E. Kitson (Gold Coast GS. Bull, i, 1935, p. 8). The future of the Rand depends on the depth to which the Banket can be mined, and the field has the great advan- tage that the rise of underground temperature is abnormally slow. Mining has already reached the depth of 7000 feet in the Village Deep Mine, and plans have been prepared for its extension to 10,000 feet, which will be more accessible on the Rand than elsewhere, owing to the slow increase of underground temperature. . The gold was probably derived from gold-quartz veins Dear the granite-schist contact that passes N. of Johannes- burg; and, as a granitic mass is exposed on the southern side of the Rand basin near Vredeport, the contact zone there May have contributed gold to the beds in that district. As the gold particles are exceptionally small they may be wide- SPread. Attention has been called by J. B. Tyrrell (Tr. LM, 1016, and Econ. Geol., xii. pp. 717-21) to an analogous €ase of the occurrence of placer gold in minute particles in the Upper Cretaceous Edmonton Sandstone of Alberta ; the gold was derived from a distant range in British Columbia and only the smallest particles reached the sea. This gold has only peen concentrated to a payable grade where recent rivers have cut through the sandstone ; there was no wide- Spread tidal action as on the Rand. i Morro VELHo—The Brazilian mine, Morro Velho in Minas Geraes, is one of the most interesting in the world. It is workeq by the St. John del Rey Mining Co. which was foundeq in 1830. The mine has an extensive literature, including Miller and Singewald (Eng. and Min. Journ., ci, bg Pp. 207-12); Hussak (Centralbl. f. Min., 1902, pp. 69-92); fo F. Calvert (Min. Res. Mines Geraes, 1915). It is now 7000 he deep and is one of the two deepest of existing mines. ts ore differs from that of any gold-quartz lode by maintaining

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