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Hokonui Formation Agglomerates

Grid Ref (WGS84 Lat/Long in decimal degrees)

-20.427222, 29.911944
Location: 
Immediately south of the Mtshingwe River Bridge on the Zvishavane-Bulawayo Road there is a road which follows the south bank of the river for about 2km before it reaches the old Mberengwa Road. Some 700m along the old road from the river is a cattle grid. A path to the east leads to the Dohwe river, an easterly trending section of which has exposed various pyroclastic flows
Stratigraphy: 
Hokonui Formation, Mtshingwe Group
Description: 

Narrow, fine-grained pyroclastic layers show graded bedding and flame structures.

 

These give way to a thick sequence of agglomerates with the dominant clasts having a similar composition to the matrix. In thin section the clasts consist of albite phenocrysts set in a dirty saussuritic groundmass containing feldspar microlites and minute quartz grains. The clast margins are very fine-grained and almost opaque except for random feldspar microlites.

 

The matrix to the clasts consists of cryptocrystalline volcanic fragments, blebs of chlorite, coarse clinozoisite and some anhedral feldspar megacrysts. A single ironstone clast was noted from these

Further Reading: 
Chauvel, C., Dupré, B., Todt, W., Arndt, N.T. and Hofmann, A.W. (1983) Pd and Nd isotopic correlation in Archaean and Proterozoic greenstone belts. Eos (American Geophysical Union Transactions), 64, 330. Hall, R. (1983) B.Sc. Dissertation Project, University of Zimbabwe. Martin, A. (1978) The geology of the Belingwe-Shabani schist belt, Geological Survey of Rhodesia, Bulletin, 83. Nisbet, E.G., Bickle, M.J. and Martin, A. (1977) The mafic and ultramafic lavas of the Belingwe greenstone belt, Rhodesia, Journal of Petrology, 18, 521-66. Orpen, J.L., Bickle, M.J., Nisbet, E.G. and Martin, A. (1985) Belingwe Peak (1:100,000), Geological Survey of Zimbabwe. Scholey, S.P. (1989) M.Phil., Ph.D. Transfer Report, University of Southampton, U.K.
Author Credit: 
Tony Martin
Contributed: 
24/10/2010
Updated: 
06/11/2014