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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Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

ORES OF GOLD 55 A deep lead must be 100 feet deep according to Victorian law, or over 20 feet deep by that of Western Australia. The rich- ness of the drifts at Golden Point was due to the river having cut through the indicator belt of Ballarat East (cf. p. 40) and to the repeated rewashing of the gravel as the valley was deepened and enlarged. The leads on the western slopes of Ballarat East disappeared at the foot of the plateau of Igneous rock which was called ‘hypogean trap; as it was regarded as deep-seated, there appeared no chance of the leads passing beneath it. This wall of rock blocked pro- 8ress, so the miners named it Sebastopol—the Crimea war being then in progress. Meanwhile in the neighbouring Fie. 17.~A Hicu Lever Deep Leap. A dissected high level Deep Lead. A modern river, AA, has cut its valley between two hills—contours at 200 and 300 ft. A Deep Lead flow- ing from 1go ft. at the eastern end to 170 ft. at the west has been cut through by the modern river, and rich gravels occurred at XX where the gold from the old river gravel had been redeposited. field of Creswick it was found that a lead continued under a similar igneous rock, which was therefore a sheet of lava and not a deep-seated mass. i This success led the Ballarat miners to renew their siege of the Sebastopol plateau; they mined underneath it and found that the leads from Ballarat East continued west- ward under five lava flows, and joined the main lead of the river that drained the area before the volcanic eruptions. The working of this lead was impossible while alluvial miners were allowed claims of only 20 feet square. By successive concessions the mines were enlarged to prospecting areas of 1000 acres and ultimately leases of 5000 acres. This en- largement of the claims rendered possible boring across the

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