Skip to main content Accessibility help
×
Home

Irumide and post-Mozambiquian plutonism in Malawi

  • H. W. Haslam (a1), M. S. Brewer (a2), D. P. F. Darbyshire (a1) and A. E. Davis (a1)

Summary

Rb-Sr whole-rock isochron ages of 443 ± 30 Ma, 449 ± 42 Ma and 489 ± 14 Ma with initial 87Sr/86Sr ratios of 0.70669 ± 0.00068, 0.70599 ± 0.00035 and 0.70658 ± 0.00025 were obtained, respectively, for the Cape Maclear granite, the surrounding Cape Maclear syenite and the Senga Bay granitic body. The results confirm previous estimates of the age of the post-Mozambiquian Lake Malawi Granitic Province, of which these plutons are part. Data from the Dzalanyama granite have excess scatter, but indicate an Irumide age of about 1000 Ma. This batholith is therefore much older than the Lake Malawi Granitic Province but much younger than the Nyika granite of northern Malawi, contrary to earlier suggestions. The porphyritic foliated granite of Mcezi Hill gave an age of 1016 ± 55 Ma and an initial ratio of 0.70522 ± 0.00084. Irumide plutonism in the region includes several dissimilar groups of intrusions, all with low initial87Sr/86Sr ratios. The Irumide age of the Dzalanyama granite makes it possible that the metasediments of the Mchinji Group are wholly post-Ubendian.

Copyright

References

Hide All
Andrew, E. M. 1974. Gravity survey of Malawi: fieldwork and processing. Rep. Inst. Geol. Sci. No. 74/15.
Bloomfield, K. 1965(a). A reconnaissance survey of alkaline rocks in the northern and central regions. Rec. geol. Surv. Malawi (1963) 5, 1763.
Bloomfield, K. 1965(b). The Cape Maclear granitic complex. Rec. geol. Surv. Malawi (1963), 5, 6479.
Bloomfield, K. 1968. The pre-Karroo geology of Malawi. Mem. geol. Surv. Malawi No. 5.
Brewer, M. S., Haslam, H. W., Darbyshire, D. P. F. & Davis, A. E. 1979(a). The petrology and geochronology of hypersthene granites in the Mchinji area, Malawi. Rep. Inst. Geol. Sci. No. 79/1.
Brewer, M. S., Haslam, H. W., Darbyshire, D. P. F. & Davis, A. E. 1979(b). Rb-Sr age determinations in the Bangweulu Block, Luapula province, Zambia. Rep. Inst. Geol. Sci. No. 79/5.
Cannon, R. T., Hopkins, D. A., Thatcher, E. C., Peters, E. R., Kemp, J., Gaskell, J. L. & Ray, G. E. 1969. Polyphase deformation in the Mozambique belt, northern Malawi. Bull. geol. Soc. Am. 80, 2615–22.
Carter, G. S. & Bennett, J. D. 1973. The geology and mineral resources of Malawi. 2nd revised edition. Bull. geol. Surv. Malawi No. 6.
Carter, G. S., Haslam, H. W. & Smith, S. H. 1973. Regional geochemical reconnaissance of Malawi. Bull. geol. Surv. Malawi No. 43.
Dawson, A. L. & Kirkpatrick, I. M. 1968. The geology of the Cape Maclear Peninsula and Lower Bwanje Valley. Bull. geol. Surv. Malawi No. 28.
Dodson, M. H., Cavanagh, B. J., Thatcher, E. C. & Aftalion, M. 1975. Age limits for the Ubendian metamorphic episode in northern Malawi. Geol. Mag. 112, 403–10.
Halliday, A. N., Stephens, W. E. & Harmon, R. S. 1980. Rb-Sr and O isotopic relationships in 3 zoned Caledonian granitic plutons, Southern Uplands, Scotland: evidence for varied sources and hybridization of magmas. Jl geol. Soc. Lond. 137, 329–48.
Haslam, H. W., Brewer, M. S., Davis, A. E. & Darbyshire, D. P. F. 1980. Anatexis and high-grade metamorphism in the Champira Dome, Malawi: petrological and Rb-Sr studies. Mineralog. Mag. 43, 701–14.
Holt, D. N. 1961. The geology of part of Fort Johnston District, east of Lake Nyasa. Rec. Geol. Surv. Nyasaland (1959) 1, 2329.
Kemp, J. 1970. Basement geology of two areas in Malawi; their essentially similar histories. 14th Annu. Rep. Inst. Afr. Geol. Univ. Leeds, 1218.
Kemp, J. 1974. The geology of the Dwangwa area. Bull. geol. Surv. Malawi No. 31.
Peters, E. R. 1975. The geology of the south Viphya area. Bull. geol. Surv. Malawi No. 36.
Ray, G. E. 1974. The structural and metamorphic geology of northern Malawi. Jl. geol. Soc. Lond. 130, 427–40.
Ray, G. E. 1975. The geology of the Chitipa-Karonga area. Bull. geol. Surv. Malawi No.42.
Ray, G. E. & Crow, M. J. 1975. A review of some age determinations from the Misuku Belt of northern Malawi. Rec. geol. Surv. Malawi 8, 4966.
Snelling, N. J. 1963. Age determination unit. Rep. Overseas Geol. Surv. for 1962, 30–9.
Thatcher, E. C. 1973. Gneisses and granites in the Malawi Province of the Mozambique belt. Spec. Publ. geol. Soc. S. Afr. 3, 149–55.
Thatcher, E. C. & Walter, M. J. 1968. The geology of the South Lilongwe Plain and Dzalanyama Range. Bull. geol. Surv. Malawi No.23.
Walshaw, R. D. 1965. The geology of the Ncheu-Balaka area. Bull. geol. Surv. Malawi No.19.
Walter, M. J. 1972. The geology of the Salima-Mvera Mission area. Bull. geol. Surv. Malawi No.30.

Irumide and post-Mozambiquian plutonism in Malawi

  • H. W. Haslam (a1), M. S. Brewer (a2), D. P. F. Darbyshire (a1) and A. E. Davis (a1)

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.