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

ORES OF PLATINUM 69 igneous origin. Platinum, however, is found in a great variety of rocks and usually in those that have undergone hydrothermal alterations and contain secondary sulphides. It is associated with serpentine, an altered ultra-basic rock in the Urals and British Columbia. In South America, in Columbia, where platinum was first discovered and which has been second only to Russia in output, it comes from gabbro along the Choco River and is found as nuggets inter- grown with chromite on the Condoto River. In New Zealand alluvial platinum has been derived from dunite, and in Spain from peridotite. It occurs in diorite in Walhalla, Victoria; in quartz-monzonite and pegmatite in Nevada; In pyroxene-syenite at Franklin, British Columbia; and in altered bands beside basic intrusions in Mexico. It is generally associated with chalcopyrite and pyrites as at Lydenburg, Sudbury, and Franklin, British Columbia, and with gold, silver, and copper ores as at Walhalla. It is in many places a constituent of quartz-veins, as in Nevada, the Waterberg Sandstone in the Transvaal, the Gympie goldfield in Queensland, and New Zealand. In Nevada, Near the Boss Mine, platinum was introduced with copper Minerals along fault planes, probably in Carboniferous times after intrusions of quartz-monzonite. It is frequently found In nuggets, which weigh up to 25 lb. in the Urals, and over 3 Ib. in Columbia ; and nuggets are usually due to secondary toncentration. The introduction of platinum by solution hasbeen claimed by L. Hundeshagen (77. I.M.M., xiii, 1904, P. 550), for the ore at Sepongi in Sumatra, for an intrusion or granodiorite that produced wollastonite and garnet, was ollowed by the entrance of solutions carrying platinum, topper, and gold. , The age of the chief platinum occurrences is Upper Palexo- 1c. The pre-Paleozoic coigns of gneiss and schist have Fie no platinum of commercial importance. The igneous the s of the Urals that contain platinum are post-Devonian ; 2 ek Nevada are late Carboniferous or Permian. The a unk in the Waterburg Sandstone of the Transvaal is a arroo (i.e. at least post-Triassic). The most numerous north, occurrences are in western North America, in the Moy, ern Andes in Columbia and Equador, the Appalachian ntains of the eastern United States, the Hercynian folds

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