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

Usage license:: Get license information via the feedback formular.

Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

104 ECONOMIC GEOLOGY view has been supported by the discovery (G. M. Butler, Econ. Geol., vii, 1912, p. 318) of the Louemma Vein (Fig. 33), along a fault which passes down from the limestone and por- phyry through quartzite into the underlying granite; it is a primary ore containing 8 oz. per ton of gold, 27 oz. per ton of silver, 11-1 per cent. of zinc, and 29-5 per cent. of lead. The Leadville ores have been followed to depths of 1500 feet and have been traced far from the outcrop. Emmons and Irving (U.S.G.S., Bull. No. 320, 1907)! showed that the ores extend beneath the De- vonian quartzite, where they are away from the porphyry. Nevertheless the ore-bodies in general follow the distribution of the porphyry. Those iso- lated in the Ordovician lime- stone may be near some un- discovered intrusion or due to solutions which rose along the course of the porphyry. The Leadville ores do not contain the lime silicates found in con- tact deposits and the country hasbeen affected by the hydro- thermal changes that happen near dykes and sills. Deposits analogous to those of Leadville occur in the Mag- dalena field in New Mexico (US.G.S., Prof. Pap. 68, 1910, pp. 51-6), and are associated with quartz-porphyry and granite-porphyry. Lead ores beside quartz-porphyry intru- sions also occur in Kelantan in the Malay Peninsula. BroxeN HiLr—The Broken Hill mining field in the arid plains of Western New South Wales is notable for its special geological features, its effect on metal prices and on metallurgy and the many mineral species first found in its gossan. The main lode is 3 miles long, in places 200 feet in width, and has Gr 1 For results from later mining, cf. G. F. Loughlin, U.S.G.S., Bull 770, 1926.

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