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

ORES OF GOLD 41 indicator may consist of a band of tiny lenticles each Wong a cleavage plane. The deposition of the gold in the ar Opposite the indicator is probably due to the reduction o the gold solutions by the oxidation of the ferrous iron in the chlorite. The miner follows the indicators and extracts the quartz which intersects them. } The Ballarat East Mines are nearer the granite than those of Ballarat West, and their deeper origin is indicated by the more frequent occurrence of albite- felspar in the quartz. The Ballarat West lodes may subdivide below into irregular veins like those of the eastern field. Gold ores are especially characteristic of the pre-Palzozoic crystalline rocks which yield gold in many countries, and include in South and West Africa, India, Siberia, Australia, and North America, some of the most productive goldfields of the world. The Mysore Goldfield in Southern India (T. Pryor, Tr. ILM.M., xxxiii, 1924, pp. 035-115) consists of pre- Paleozoic rocks, of which the founda- tion is mainly hornblende-schist. It has been invaded by masses of granite and gneiss, and by dykes of felsite. While these rocks were cooling the schists were fractured, and the fissures filled by dark, bluish-gray quartz-veins, which were widened by the replacement of the walls, residues of which remain . as actinolite, pyroxene, and brown mica. After the igneous rocks had become quite solid, N.N.W. faults broke througt the quartz-veins, and solutions from below introduce go Pyrites, arsenopyrite, blende, galena, and chalcopyrite. 3 these solutions were pneumatolytic is shown by the abun oo tourmaline, and some scheelite. The gold was deposited in rich shoots where it entered the inclined usta, Su 2 quently the country was broken by faults trending wo to S. and they were filled with further lodes containing

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