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 8s ores; they are typical fissure lodes of quartz with Sry sulphides and pyrite, but have replaced some of the wa rock. The Cornish copper mines have an extensive literatur € (ef. J. H. Collins, W. of England Mining Region, 1912, - XV-XX), reas Soumm AUSTRALIA AND SoutH Arrica—The Wallaroo Mines, near Moonta in South Australia, are quartz- “halcopyrite loges in orthoclase-porphyry. The lodes are bre-Palzozoic, as they do not pass up into the overlying Cambrian. The ore forms deep pipe-like shoots, which con. tain from 3 to 4 per cent. of copper and have been worked to the depth of 2000 feet, } . The Namaqualand copper ores of South Africa occur 1n shallower pipes which have a regular quincuncial arrange- Tent at the intersections of a network of fractures. Accord- vos to Kuntz (Tr. G. Soc. 5. afr, vii 1904, p. 70) the pipes occur where parallel joints cross lode-filled fractures; but according to J. I. Ronaldson (ibid., viii, 1906, p. 161), the Material in the fractures looks like dykes though it may be altered pnejgs, The ores were obviously due to deposition 5Y solutions Passing along intersecting fissures. Disseminations AND REPLACEMENTS — Fissure lodes are often enlarged by the replacement of the walls. In some cases the ore thyg deposited so greatly exceeds that in the fissures that the result is 5 replacement lode, The simplest replacement ores consist of scattered grains Or small patches of copper sulphides, as in the olivine-gabbro of Monte Catini in Tuscany, Cuba, and Turkey. The rock beside the Monte Catini gabbre has been altered to a fractured serpentine which contains veins of copper ore. . The second type is commercially more important, and Includes masses of copper ore in limestones, as at Chillagoe in Queensland ; the solutions having been neutralized by the limestone, the Copper minerals were deposited by its replacement, Analogous ores occur in tuffs at Boundary Creek, British Columbia, A third 8roup of replacement ores are formed as contact products, chiefly beside intrusions of porphyry and diabase into limestone, They occur on a small scale at Campiglia Marittima ip Tuscany, at the contact of diabase with Liassic limestone, ang near Oslo in Norway. The most important

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