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 IRON 143 dyke. According to Per Geijer (Geol. Kiruna, 1910, p. 269; he later adopted the dyke theory), the ore was discharged as a lava flow of magnetite. One essential fact is the occurrence along the base of the quartz-porphyry of fragments of all the varieties of the under- lying ore. The ore was therefore in existence before the first quartz-porphyry lava flow. Prof. Daly’s theory is attended by the difficulty that the quartz-porphyry contains only from 2-9 to 8 per cent. of iron oxide, and the lowest flow, which could alone have supplied the ore, could not have provided the quantity in the lode; and that porphyry still contains a normal amount of iron. SY. - QP CST Gi’ ow. ws’ Fie, 46.-—TuE ORE-SHEET OF KIRUNAVAARA, SWEDISH LAPLAND. Sy.P., syenite-porphyry; solid black, the ore, sharply bounded above, with occasional secondary spurs passing upward,” Q.P., the quartz- porphyry, of which the lower flow contains at the base angular fragments of the ore; C.S.T., conglomerate, sandstone, and tuff; S., quartzite. The iron ore pebbles in the quartz-porphyry favour the formation of the ore by some aqueous agency. The sheet of ore (Fig. 46), though sharply separated from the quartz- porphyry, passes down gradually into the underlying syenite- porphyry; the iron appears to have been dissolved from the underlying syenite and deposited on its surface as a sheet of phosphatic bog iron in a swamp, as suggested by W. H. Herdsman (Journ. Ir. and St. Inst., Ixxxiii, 1911, p. 480), Or as a deposit from hot rising water, as suggested by Bick- Strém (Geol. Fir. Stockholm Fork., xxvi, 1904, pp. 180-5), OF as a sheet of surface ironstone formed by evaporating water.l Backstrom described the process as pneumatolvtic as ‘ De Launay, dun. Mines (10), IV, 1903, Pp. pad = sedimentary, A new paper by Vogt (6G. For. Bork I92 fib 153 5) Arges the intrusive nature of the ore, regarding the Segregations,

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