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 COPPER 93 Ball and Shaler, ibid., ix, 1914, pp. 629-30, 632). They are interstratified with slates and dolomites. The beds in depth contain sulphides. The rich ores are mainly carbonates, especially malachite, and are secondary enrichments con- taining from 6 to 14 per cent. of copper. The original bedded Ores are pre-Paleozoic; the country has been lowered Probably thousands of feet by denudation, and ores from the rocks removed have been concentrated in the enrichments. BeppED OR SEDIMENTARY ORES — MANSFELD AND Micuigan — This group of copper ores has given rise to prolonged difference in interpretation. Red sandstones of different ages and countries are associated with copper ores, Which at Mansfeld in Germany have been worked since the year 1199.! That field has yielded 800,000 tons of copper and been the second largest copper-producing field in Europe. The area has been described as the birthplace of strati- graphical geology. The ore occurs in a Permian bituminous shale (the Kupferschiefer), which lies above the Lower Permian red sandstones, and below the Zechstein, a Middle Permian limestone. The average ore contains about 14 per cent. of copper, 3nd occurs in three layers of a bed which is usually from 20 to 24 inches thick ; but the ore may penetrate 4 inches into the Underlying sandstone. The bed is often traversed by faults which contain copper and cobalt. The great extent of the deposit—in the Mansfeld syncline alone 1t is 15 miles wide—suggested the origin of the copper ww Precipitation from the Permian sea. The bed contains 0d plants and fossil fish of which the distorted shape, according to von Groddeck, was due to the agonies of copper Poisoning, but was probably caused by ordinary post-mortem shrinkage, According to the second theory, mainly supported y Beyschlag and Krusch, the copper was brought in solution JP the faults and precipitated in the shale by its organic Matter. The copper is present as grains and nests of chal- Ocite which ig usually, and bornite, which is often, secondary, and as later veins of chalcopyrite: the .ore has partly Tor the history of this field, cf. Dr. W. Hoffmann, Mansfeld, Gedenk- rift sum 725 Jaehrigon Bestchen des Mansfeld-Konzerns, 1200-1925, Be PP; Berlin, 1025. A recent description of the geology s given by . D, Trask, Zeop, Geol., xx, 1925, pp. 746-61.

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