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

[06 ECONOMIC GEOLOGY the Davis Shale, the Potosi Dolomite, and a series of sand- stones and shales which pass up into the Ordovician. The Bonneterre and Potosi Dolomites contain most of the ores. The rocks have been greatly faulted, but show no evidence of the action of hot waters or high temperatures. The ores were at first attributed to solutions rising up fault planes. This view was modified by Foster Bain, who, although accepting the primary introduction of the metals by ascending solutions, explained the ores as secondary and concentrated by descending water. The evidence for the descending water is convincing. The ore in the weathered zone of Potosi Limestone is in vertical channels and pipes, which are richest near the surface. and some ore was deposited F16. 34.—LEAD AND Zinc ORES oF MissourL Diagram of the lead and zinc ores of Mis souri (after Buckley). The rocks con- sist of limestone and. shale with the ore deposits descending sometimes in funnel-shaped concentrations and spreading out over the upper side of the bands of shale. Some veins of solid ore. in cavities as stalactites. The galena is associated with pyrites, barite, blende, smithsonite, anglesite, cerussite, and calcite. The barite of this field supplies a large part of that worked in the United States. The amount of zinc is small. The ores in the Bonneterre Dolomite were also concentrated by descending solutions, and the mines first worked shallow deposits in cavities, caverns, and veins. The ore in the upper workings was mostly the carbonate, cerussite, and coarsely crystalline galena; the deeper galena is in widely disseminated particles. The ore is in places collected in veins, which cut steeply across the bedding ; the disseminated ores occur along the upper and lower sides of a band of shale, and in carbonaceous or bituminous layers, and in seams of limestone between shales. The condition and distribution of the ore shows that it was formed by descending solutions concentrating scattered

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