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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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

ORES OF COPPER 83 formed at high temperatures as they are associated with many basic dykes, some of which are earlier and others later than the lodes. The lodes in 1000 had been worked to the depth of over 2000 feet, and the ore contained an average of -8 per cent. of copper, gold worth about £2 10s. per ton of ore, and some nickel. The ores are clearly of hydrothermal origin, and support the same formation of the nickel ores of Sudbury (cf. pp. 114-18). The copper mines which saved South Australia at a critical stage of its early history derived their copper from a pneu- matolytic source. The rich oxidized ores at Burra-burra, which yielded 22 per cent. of copper, were discovered in 1845, and are in altered slate and limestone. The primary F16. 28.—THE BrapeEn Copper MINE, CHILE. One stage in the development of the Braden Copper Mine, Chile. V, the volcanic rocks forming the country; AP, intrusive andesite- porphyry; BT, Braden tuffs filling the explosion crater; B, the intrusive breccia invading both the porphyry and the tufis. re was discovered at Moonta in 1861, and is a pegmatitic formation of quartz, microcline, tourmaline, apatite, and fAuorite. Five lodes occur in quartz-porphyry, which at Moonta has been intruded by pre-Cambrian granite; the lodes contain 2 to 5 per cent. of copper in chalcopyrite, and were covered by an oxidized zone containing copper carbonates, atacamite (oxychloride of copper), and native “opper. The Moonta Mine was once the deepest copper Mine in the world and has been worked to 2600 feet. The Braden Mine, Chile (Lindgren and Bastin, Econ. Geol, xvii, 1922, pp. 75-99), illustrates the relations of the Pheumatolytic to other copper ores (Fig. 28). It is in the Western Cordillera about 100 miles S.E. of Valparaiso. The Mine is in an extinct volcano in Kainozoic tuffs and lavas,

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