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IV.—On some Variolitic Rocks on Carrock Fell

Published online by Cambridge University Press:  01 May 2009

Alfred Harker
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Extract

The district of Carrock Fell,inCumberland, is one richinvarieties of intrusive igneous rocks. Those on Carrock Fell itself, while probably belonging to one period of igneous activity, fall under three or four heads, which can be arrangedinchronological sequence, as follows:—

(i.) a large intrusion of gabbro generally laccolitio in character.

(ii.) a granophyre, also forming laccolitic bodies, but with associated dykes and veins which traverse the gabbro.

(iii.) a diabase or gabbro, not essentially different from the first intrusion, but injected later and under somewhat changed conditions.

(iv.) a large number of dykes and veins of intermediate to basic composition.

These last are found traversing all the other rocks, and therefore, if we are justifiedingrouping them all together, they represent the latest intrusions in the neighbourhood. They vary from straight dykes two or three feet wide to narrow and rather tortuous veins not more than an inch in width.

I have recently presented to the Geological Society an account of the larger intrusive masses of Carrock Fell,1 and I originally intended to include also the minor dykes and veins alluded to. This purpose I abandoned in view of the multiplicity and variety of rocks which they include, but some of the specimens examined seem worthy of a brief notice.

Type
Original Articles
Information
Geological Magazine , Volume 1 , Issue 12 , December 1894 , pp. 551 - 553
Copyright
Copyright © Cambridge University Press 1894

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References

1 Part I., dealing with the gabbro, is publishedinQ.J.G.S. vol. 1. (1894), pp. 311–336.Google Scholar

2 Q.J.G.S., vol. xlv. (1889), pp. 298–304.Google Scholar

3 Analysis by Mr. K. H. Adie (Groom, I.c.). The iron is estimated as ferric oxide, but is probably present in the ferrous state, which would explain the high total of 103·76 per cent.