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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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part II. Ore deposits

Collection:: Economics Books

ORES OF IRON 135 has yielded the highest grade hematite ores of the British Isles. They are gash-veins in the older rocks, and nodular masses and sheets in the Silurian and Carboniferous Lime- stones. The first group are of little economic importance. The Eskdale granite (granophyre), the Ennerdale syenite, and Skiddaw Slates are traversed by steep gash-veins of hematite which thin out as they are followed downwards; they have been worked in the granophyre to the depth of 300 feet. The veins thicken where two of them intersect. Some cylindrical stems made of concentric layers and known as ‘ ring-ore ’’ were mistaken for fossil tree stems. The ore of the gash-veins was clearly formed by replacement of the ah. S ) Gh. Sh. F16. 40.—Tur REPLACEMENT HEMATITE ORE-BODIES OF CUMBERLAND, R.S. and R.Sh., Permian red sandstones and shales; L., Carboniferous limestone; Sh,, shales; Sli, slate; F., fault, The ore-beds are shown in solid black. country rock by solutions descending along fissures, for the massive ore passes into iron-stained country rock, and the veins in the granophyre include unreplaced felspar. The most important of the Lake District ores are replace- ments in Carboniferous Limestone (Fig. 40), including large kidney-shaped masses of hematite (Fe,O3) which may con- tain 98 per cent. of iron oxide, with the phosphorus varying from ‘02 to +3 pér cent. The ore has replaced some thin beds of limestone, bosses of which remain on the floor of the seam. In some cases limestone has been partially replaced by infiltration from overlying sandstone and the ore forms funnel-shaped masses which may spread out below into an irregular sheet. The largest ore-bodies occur along faults,

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