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

54 ECONOMIC GEOLOGY its value to such great depths. The ore-body has the shape of a flattened pipe with an average thickness of 10-12 feet., a maximum of 33 feet, and a width of usually less than 600 feet, though in places of 1000 feet. It is in a bed of chloritic schist which is probably altered calcareous clay. The bed is vertical, and the pipe of ore lies along it at an angle of 45° to the horizontal. The ore consists of sulphides, especially pyrite, pyrrhotite, and arsenopyrite, with a little chalco- pyrite, and a matrix of siderite, quartz, dolomite, and calcite, with some carbon and fragments of the chloritic schist. The gold is rarely seen as it is present in the arsenopyrite. The ore was foliated after the mineralization, and the sparse vein-quartz is barren. There is no evidence of much earth- movement, such as faulting, and no pug along the ore. The lower levels are quite dry and the lode has no deep-seated minerals, such as tellurides or tourmaline, There is also no clear evidence of the infiltration of solutions, and the ore has maintained its value as deep as it has yet been followed. This lode was probably a placer containing alluvial iron oxide and fine-grained gold ; when the sediments were foliated into chloritic schist, the iron minerals were converted into sulphides, and the gold dissolved and redeposited with the arsenopyrite. This view is consistent with the continued richness of the ore in depth, its mineral character and micro- scopic structure, and absence of infiltration channels.

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