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 II. Ore deposits

Collection:: Economics Books

{18 ECONOMIC GEOLOGY area of pillow lavas. The ore-bodies have replaced the sedi- ments at the contact with the quartz-porphyry. The ore occurs in shoots, of which over 30 are known ; a few are in the quartz-porphyry and the lavas, but most are in the sedi- ments. The Hollinger Mine, which is now one of the world’s great mines having up till 1923 produced £15,350,000 worth of gold, consists of a belt of Keewatin lavas which have been sheared and crushed into schist; nodules of unsheared rock can be found which show the variolitic structure. The in- trusion of quartz-porphyry was followed by the deposition of many lodes which are sub-parallel to it, but some- times cut across it. The lode material is mainly quartz, much of which encloses lava debris. A little poor ore has N FD. 5 5 no _ Fr ¥ v ol. Fre. 13.—TuE Dome Mine, PorcupiNg. The section across the country north of the Dome Mine, Porcupine Goldfield, Canada, S, gently folded sedimentary beds, slates, and quartzites, overlying conglomerates. Both are intruded by quartz. porphyry, P. The Dome Mine, D, with the ore-bodies {black} occurs along a fault, F, separating the sedimentary beds from the pillow lavas, p.i., which form an extensive area south of the mine. been found in the quartz-porphyry. According to Spurr the quartz-lodes are intrusive vein-dykes; but to the author they appear due to the saturation of a crushed mass of rock by solutions which deposited the quartz along the main channels of circulation. That the ore formation was deep-seated is shown by the abundance of tourmaline in part of the Dome Mine and the abundant tellurides including hessite (silver-telluride), altaite {lead telluride), and sylvanite and petzite (gold-silver tel- furides). The tellurides in the Hollinger Mine were sparse ‘n the upper levels, but abundant 800 feet deep. THE GorprieLps or West AUSTRALIA—West Australia consists of a plateau which rises from the coast by a mountain scarp to the height of about 1800 feet, and after extending

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