Hostname: page-component-77c89778f8-fv566 Total loading time: 0 Render date: 2024-07-16T23:57:44.061Z Has data issue: false hasContentIssue false
  • English
  • Français

Olivine nodules and related inclusions in trachyte from the Jos Plateau, Nigeria

Published online by Cambridge University Press:  05 July 2018

J. B. Wright
J. B. Wright*
Affiliation:
Department of Geology, Ahmadu Bello University, Zaria, Nigeria
Get access Rights & Permissions [Opens in a new window]

Summary

A trachyte plug near Jos contains a suite of inclusions, commonly rounded and of large size, including olivine nodules, pyroxenites, and a variety of basic to intermediate plutonic rocks, as well as albite megacrysts.

The olivine nodules are typical of those found elsewhere in alkaline basic lavas and widely interpreted as upper mantle fragments. Most of the other inclusions contain evidence of crystallization at high pressures, even the syenites, which are interpreted as plutonic equivalents of the trachyte; for the feldspar in them is sanidine-microperthite.

Discovery of this inclusion assemblage in a trachyte provides further support for the thesis that alkaline salic lavas can be generated at sub-crustal depths, by partial melting beneath domically uplifted continental shield areas (Bailey, 1964).

The Nigerian Cenozoic volcanic province lies in an area of regional uplift, and is characterized by scattered small volcanic centres rather than by major eruptive foci. High pressure inclusions are being found at an increasing proportion of these centres, suggesting that the magmas rose directly and rapidly to the surface from the upper mantle levels at which they were all (including the trachyte) generated.

Type
Research Article
Information
Mineralogical Magazine , Volume 37 , Issue 287 , September 1969 , pp. 370 - 374
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1969

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Aoki, (K.), 1964. Amer. Min. 49, 1199.Google Scholar
Bailey, (D. K.), 1964. Journ. Geophys. Res. 69, 1519.CrossRefGoogle Scholar
Carter, (J. D.), Barber, (W.), and Tait, (E. A.), 1963. Geol. Surv. Nigeria, Bull. 30.Google Scholar
de Roever, (W. P.), 1961. Fortsehr. Min. 39, 96.Google Scholar
Dickey, (J. S.), 1968. Amer. Min. 53, 1304.Google Scholar
Falconer, (J. D.), 1926. Geol. Surv. Nigeria, Bull. 9.Google Scholar
Green, (D. H.) and Ringwood, (A. E.), 1967. Contr. Min. Petr. 15, 103.CrossRefGoogle Scholar
Harris, (P. G.), Reay, (A.), and White, (I. G.), 1967. Journ. Geophys. Res. 72, 6359.CrossRefGoogle Scholar
Jacosson, (R. R. E.), MacLeod, (W. N.), and Black, (R.), 1958. Geol. Soe. London, Mem. 1.Google Scholar
MacKay, (R. A.), Greenwood, (R.), and Rockingham, (J. E.), 1949. Geol. Surv. Nigeria, Bull. 19.Google Scholar
Moore, (A.), 1968. Contr. Min. Petr. 17, 233.CrossRefGoogle Scholar
Wright, (J. B.), 1965. Geol. Mag. 102, 541.CrossRefGoogle Scholar
Wright, (J. B.), 1966. Nature, 210, 519.CrossRefGoogle Scholar
Wright, (J. B.), 1968. Min. Mag. 36, l024.Google Scholar
Wright, (J. B.), 1969. Geol. Mag., in press.Google Scholar