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Composite phonolite tholoids in the Cenozoic volcanic province of Nigeria

Published online by Cambridge University Press:  01 May 2009

J. B. Wright  and
Patricia McCurry
J. B. Wright
Affiliation:
Department of Earth Sciences, The Open University, Walton, Buckinghamshire
Patricia McCurry
Affiliation:
Department of Earth Sciences, The Open University, Walton, Buckinghamshire
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Summary

Small trachyte and phonolite bodies are shown as eroded plugs on published geological maps of part of north-eastern Nigeria. Field relationships at two such ‘plugs’ strongly suggest them to be extrusive in origin, formed of an earlier tholoid-building phase, followed by extrusion of a spine (plug dome) of very viscous lava, now forming the central peak at each locality. Petrographic data show that the tholoid and spine-forming lavas are phonolites of contrasted composition. Eruption of salic lavas from scattered centres appears to have occurred intermittently between mid-Tertiary and Pleistocene times.

Type
Articles
Information
Geological Magazine , Volume 107 , Issue 4 , July 1970 , pp. 357 - 360
Copyright
Copyright © Cambridge University Press 1970

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References

REFERENCES

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