The Elements of economic geology

Bibliographic data

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 I. Introduction

Collection:: Economics Books

THE FORMATION OF DEPOSITS 23 water being superheated would be a powerful solvent, and would thus obtain alkalis, that increase its power of dissolving quartz and metallic sulphides. The metallic barysphere, like the iron meteorites, doubtless contains sulphides, such as the iron sulphide, troilite, and phosphides (e.g. schreibersite), and carbon as graphite. The solution of troilite would give rise to ferrous sulphate, which is a solvent for gold. The water would also include chlorides, and fluoric and boric acids. This complex solvent would work its way upwards through the rocks, dissolving from them silica and metallic sulphides. The small spaces would unite into large channels along major fissures and fault planes, and through them solu- tions would rise more quickly. From the lower zone of solution the water would reach conditions under which it would begin deposition. It would be constantly passing under less pressure and lower temperature, and both in- fluences would throw materials out of solution. Chemical reactions would aid, as contact with lime would neutralize acid solutions, while carbon by reducing the ferrous sulphate solution would precipitate metallic sulphides; and as gold would no longer be soluble it would be precipitated at the same time. Hence solutions rising up fissures, and especially up the great faults which mountain structures show to ex- tend over 100 miles deep, would bring to the surface metals from the ore-zone. Macwmatic OREs—The nature of these solutions is the main current problem in ore genesis. As the solvent must be mostly water and the temperature high, they are justly called hydrothermal ; but as many authorities held that all the water on or in the earth’s crust falls upon it as rain, the ore-forming solutions were attributed to surface water which had sunk underground, had there dissolved scattered metallic particles and deposited them in lodes as the water was forced to the surface by the gas pressure due to heat. Ores formed by this process of lateral secretion appear to be more abun- dant than has been generally admitted in recent years; they include not only ores of iron and manganese, but many others, such as the copper ores of Mansfeld, of Cheshire, and some of those of Katanga, some of the lead and zinc ores of Mississippi and the rich gold ores of Mount Morgan. For ordinary lodes the lateral secretion theory has been

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