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

Usage license:: Get license information via the feedback formular.

Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

D2 ECONOMIC GEOLOGY on its intrusion. Some of the lode-fissures were due to shrinkage of the cooling monzonite and dykes. The sulphides in the original lodes were sparse; but as the country was cut down by denudation the primary sulphides were concen- trated into bodies of chalcocite which formed the wealth of the Butte Field. OVER-DISSEMINATED AND REPLACEMENT Bopies—Rocky Mountains, Congo—The copper-fields of the Rocky Moun- tains, in Arizona and Utah, contain secondary ores concen- trated from low-grade primary sulphides. = The mining districts consist of ancient granitic rocks covered by Palaxo- zoic and Mesozoic limestones; these rocks were invaded by Lower Kainozoic granite-porphyry and monzonite, beside which are contact bands of lime-silicates, including garnet, tremolite, vesuvianite, diopside, and epidote, and of calcite mixed with chalcopyrite, bornite, and pyrites. Lenticular and tabular deposits of the same ores pass from the porphyry into the limestone, which also contain scattered grains and thin veins of the sulphides. The primary ores contain about 5 per cent. of copper, and mining is dependent on the large secondary enrichments of chalcocite and carbonates, At Bisbee (cf. Ransome, U.S.G.S., Prof. Pap., No. 21, 1905), 6 miles N. of the Mexican frontier, the mines are in Car- boniferous Limestone; the ore is oxidized to the depth of 1400 feet, and caves contain the beautiful blue azurites for which the Copper Queen and other mines were famous. At Clifton-Morenci in S.E. Arizona (cf. W. Lindgren, ibid. No. 43, 1905), the granite and monzonite-porphyry intrusions and many dykes are bordered by contact ores; the ores to the depth of from 50 to 200 feet were mainly oxidized ; from the depth of 100 to about 400 feet lay secondary en- richments of chalcocite with from 3 to 4 per cent. of copper ; below 400 feet are low-grade primary ores of pyrite, chal- copyrite, and blende. The mines at Bingham, in Utah (Butler, 4tid., No. III, 1020, pp. 340-62), in Palmozoic limestones are at the margin of monzonite and djorite. porphyry, and contain masses of chalcocite concentrated from the primary ores. Most of the vast quantities of low-grade ores of Katanga in the Belgian Congo appear to be also alluvial in origin (as suggested by Lindgren, Econ. Geol., vi, 1911, P- 575: cf.

Access restriction

Copyright

fullscreen: The Elements of economic geology

Monograph

Chapter

Table of contents

Download

Monograph

Chapter

This page

Image fragment

Citation links

Citation recommendation