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Batholiths of Southern Rhodesia

Published online by Cambridge University Press:  01 May 2009

A. M. Macgregor
A. M. Macgregor
Affiliation:
(Published by permission of the Director, Geological Survey of Southern Rhodesia.)
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Extract

THE problem of the formation of the larger masses of granite is receiving considerable attention by geologists at the present time, and it is hoped that the following observations and surmises regarding the granites of Southern Rhodesia may be of more than local interest. Southern Rhodesia forms part of a typical Pre-Cambrian shield and consists, apart from younger formations, of about 74,000 square miles of granite and gneiss intrusive into 13,000 square miles of older rocks. The area has undergone tremendous denudation, which took place mainly during the Pre-Cambrian, and the structures exposed, therefore, are different from those seen in regions where only the peaks of granite masses have been uncovered.

At the outset I wish to thank Mr. H. B. Maufe for permission to draw from the store of information, much of it unpublished, which he has collected in the Geological Survey Office at Salisbury, and also for having the accompanying illustrations drawn in the office. This information includes both petrological and structural data, but it is only the structural aspect of the problem which it is intended to discuss here.

Type
Original Articles
Information
Geological Magazine , Volume 69 , Issue 1 , January 1932 , pp. 18 - 29
Copyright
Copyright © Cambridge University Press 1932

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References

Notes and References

(1)Lightfoot, B., “The Geology of the Country around Gatooma,” S.R.G.S. Bulletin, No. 5, p. 12. A. M. Macgregor, “The Geology of the Country between Gatooma and Battlefields,” S.R.G.S. Bulletin, No. 17, p. 14. In the area north of Bulawayo, also, the rocks and amygdales are likewise mainly quite undeformed.Google Scholar
(2)These conditions of metamorphism are exemplified in the Victoria, Selukwe, Salisbury, Bindura, and Darwin schist belts. See Maufe, , Lightfoot, and Zealley, , “The Geology of the Selukwe Mineral Belt,” S.R.G.S. Bulletin, No. 3; H. B. Maufe, “ The Geology of the Enterprise Mineral Belt, S.R.G.S. Bulletin, No. 7; Lightfoot and Tyndale-Biscoe, “ The Geology of the Country West of Mount Darwin,” S.R.G.S. Bulletin, No. 10.Google Scholar
(3)Annual Report of the Director, S.R.G.S., 1926, pp. 5 and 6.Google Scholar
(4)The structure of the pillow lavas has been found particularly useful. See S.R.G.S. Bulletin, No. 11, pp. 18 and 19 (in line 17 omit “ and lower ”), and S.R.G.S. Bulletin, No. 17, chap. ii.Google Scholar
(5)Maufe, and Macgregor, , “ Second Interim Report on the Geology of part of the Bembesi Basin,” S.R.G.S. Short Report, No. 9, pp. 8 and 9; A. M. Macgregor, “ The Geology of the Country between Gatooma and Battlefields,” S.R.G.S. Bulletin, No. 17, p. 31, and pl. v, figs. 1 and 2. Steep folding is to be seen among other places at the Sebakwe Poort near Que Que and at the Salisbury Kopje.Google Scholar
(6)Bailey, E. B., “ Iceland—a Stepping Stone,” Geol. Mag., LVI, 1919, 466–77, or Émile Haug, Traité de Géologie, p. 320; L. T. Nel, “ The Geology of the Country around Vredefort,” Union of S.A. Geological Survey, 1927.CrossRefGoogle Scholar
(7)Exhibit “A”. Report of the Committee on Batholithic Problems appointed by the Board of Geology and Geography of the National Research Council of the U.S.A., Washington, 1930.Google Scholar
(8)Adams, F. D., “Structure and Relation of the Laurentian System in Eastern Canada,” Quarterly Journal of the Geological Society, lxiv, 1908, 127–48.CrossRefGoogle Scholar
(9)Daly, R. A., Igneous Rocks and their Origin, pp. 89–116, New York and London, 1914.Google Scholar
(10)Sederholm, J. J., “ On Migmatites and Associated Pre-Cambrian Rocks of South-West Finland,” Bulletins de la Commission Géologique de Finlande, No. 58 and No. 77, Helsingfors, 1923 and 1926.Google Scholar
(11)Wagner, P. A., “The Geology of a Portion of the Belingwe District,” Trans. Geol. Soc. of S. A., xvii, 1914, 39–54. For further information regarding the southern batholith see B. Lightfoot, “ The Geology of the Selukwe Mineral Belt,” S.R.G.S. Bulletin, No. 3, p. 51; A. M. Macgregor, “ The Geology of the Country around the Lonely Mine,” S.R.G.S. Bulletin, No. 11, p. 50, and “ The Geology of the Diamond-bearing Gravels of the Somabula Forest,” S.R.G.S. Bulletin, No. 8, pp. 13–14; and F. E. Keep, “ The Geology of the Shabani Mineral Belt,” S.R.G.S. Bulletin, No. 12, p. 60. For the northern or Rhodesdale batholith, see A. E. V. Zealley, “The Geology of the Country around Gatooma,” S.R.G.S. Bulletin, No. 5, pp. 17–21, and A. M. Macgregor, “ The Geology of the Country between Gatooma and Battlefields,” S.R.G.S. Bulletin, No. 17, p. 54.Google Scholar
(12)Macgregor, A. M., “The Geology of a small area east of Bulawayo,” Trans. Geol. Soc. of S.A., xxiv, 150–67. The Bindura granite is the country rock of some promising gold mines. Mr. Lightfoot states in a personal communication that the greater part of this mass is a normal grey granite, but that there is a marginal belt along the southern edge of gneissic granite crowded with inclusions of Shamva grit. A. M. Macgregor, “ The Geology of the Felixburg Goldfield,” S.R.G.S. Short Report, No. 18.Google Scholar
(13)Macgregor, A. M., loc. cit., S.R.G.S. Bulletin, No. 17, p. 60.Google Scholar
(14)Holmes, A., “Contribution to the Theory of Magmatic Cycles,” Geol. Mag., LXIII, 1926, 306–29.CrossRefGoogle Scholar