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

ORES OF PLATINUM 67 rocks include pre-Devonian granite and porphyry; granites and porphyries intrusive into the Devonian; syenite- Porphyrites, quartz-keratophyres, and aplites that are Carboniferous and perhaps partly Permian. The character- istic igneous rocks of the Urals are serpentines and dunites, which are intrusive into the Lower Devonian limestones, and basic diabases, which range in age from the pre-Devonian to Upper Carboniferous or Permian. The Urals were compressed by mountain movements after the Artinskian (Upper Carboniferous), and some of the folds have been overturned westward. The dunite was at first regarded as the only parent rock of platinum, but it is also found in olivine-pyroxenite, gabbro, and serpentine. The Plagi F16, 24.—PLATINUM IN PYROXENITE. atinum in pyroxenite replacing and corroding the pyroxenite, P; from the Urals. (After Duparc and Tikonowitch, 1g20.) placers from which the main supply is obtained (Fig. 23) rise on the dunite masses. In pyroxenite, according to Dupare and Tikonowitch (1920, La Platine et les Gites Platiniferes de POural, P. 80), the platinum * generally forms a local cement between the crystals of pyroxene; ” it is often found in Nodular segregations of chromite; in the dunite it is seen excessively rarely ” (ibid., p. 193). The platinum is doubt- less of deep-seated origin; but as it in part replaced the chromite and ferro-magnesian minerals, and has been moulded on the olivine and pyroxene, Beck truly described the plati- Um as the last formed mineral in the rock (Fig. 24). South Arrica—The Transvaal is expected to become the chief Producer of platinum, as it includes large deposits, estimated to contain 5 dwt. to the ton, at Lydenburg in the

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