SciELO - Scientific Electronic Library Online

 
vol.110 issue2A heat transfer model for high titania slag blocksA basic triboelectric series for heavy minerals from inductive electrostatic separation behaviour author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Journal of the Southern African Institute of Mining and Metallurgy

On-line version ISSN 2411-9717
Print version ISSN 0038-223X

J. S. Afr. Inst. Min. Metall. vol.110 n.2 Johannesburg Feb. 2010

 

TRANSACTION PAPER

 

Characteristics, recovery and provenance of rutile from the Namakwa Sands heavy mineral deposit, South Africa

 

 

A. Rozendaal; C. Philander; C. Carelse

Department of Earth Sciences, University of Stellenbosch, Matieland, South Africa

 

 


SYNOPSIS

The Namakwa Sands heavy mineral deposit is located along the West Coast of South Africa and the mine is a world class producer of high quality zircon, ilmenite and rutile concentrates from essentially unconsolidated marine and aeolian sands of Cainozoic age. The objective of this study was to characterize rutile with respect to distribution, grain size, textures, colour and mineral chemistry within the Namakwa Sands orebody with the aim to explain its overall poor recovery. A representative suite of heavy mineral concentrates from various sections of the orebody and stages in the recovery circuit has been investigated microscopically and by means of SEM-EDS and LA-ICP-MS. The rutile grain size distribution displays a wide range and is directly related to its variable chemistry and consequently density. In placer deposits such as Namakwa Sands, mineral sorting is a function of hydraulic equivalence, and high density grains are smaller than the lighter grains when deposited under similar conditions. Grain size is also a function of sediment maturity, and the highly mature red aeolian sand (RAS) component of the deposit has a coarser grain size than the less mature orange feldspathic marine sands (OFS). The above primary characteristics of rutile are responsible for the loss of the coarse-grained fraction during screening and, given the empirically determined relationship that increased substitution elements reduce conductivity, also during electrostatic separation. Provenance studies using geothermometry have shown that the heavy mineral suite has been sourced mainly by the proximal medium-to high-grade Namaqualand Metamorphic Complex. The positive relationship between substitution elements and temperature of formation explains their high concentration in rutile of this deposit. The heterogeneity of rutile, produced by the combination of a high temperature primary source and the typical marine-aeolian placer genesis is deposit specific and unfortunately not conducive to high recovery levels in the current Namakwa Sands beneficiation circuit.


 

 

“Full text available only in PDF format”

 

 

References

1. Gous, M. An overview of the Namakwa Sands Ilmenite smelting operations. Southern African Pyrometallurgy, R.T. Jones (ed.), 2006. pp.189-201.         [ Links ]

2. Cilliers, L.M. The geology of the Graauwduinen heavy mineral sand deposit, west coast of South Africa, M.Sc Thesis (Unpublished), University of Stellenbosch, South Africa. 1995.         [ Links ]

3. Palmer, G.L. The Discovery and Delineation of the Heavy Mineral Sand Orebodies at Graauwduinen, Namaqualand, Republic of South Africa, Exploration Mining Geology, vol. 3, 1994. pp. 399-405.         [ Links ]

4. Pether, J., Roberts, D.L., and Ward, J.D. Deposits of the West Coast. Partridge, T.C. and Maud, R.R. (eds.), The Cainozoic of Southern Africa. Oxford Monographs on Geology and Geophysics, vol. 40, 2000. 406 pp.         [ Links ]

5. De Beer, C.H., Gresse, P.G., Theron, J.N., and Almond, J.E. The Geology of the Calvinia Area. Council for Geoscience, South Africa, 2002. pp. 1-55.         [ Links ]

6. Cole, D.I. and Roberts, D.L. Stratigraphy, sedimentology and lignite potential of the Cainozoic strata of the West Coast, Western Cape Province South Africa.. Council Geoscience South Africa. Report number, 1996. pp.1995-0078.         [ Links ]

7. Philander, C. and Rozendaal, A. Geometallurgical challenges of Namakwa Sands-A South African titanium-zirconium heavy minerals mine. Ninth International Congress for Applied Mineralogy. Brisbane, Australia, 2008. pp. 459-464.         [ Links ]

8. Rozendaal, A. and Philander, C. Heavy mineral placer deposits along the West Coast of South Africa-A world-class resource of zircon, ilmenite and rutile. Ninth International Congress for Applied Mineralogy. Brisbane, Australia, 2008. pp. 73-78.         [ Links ]

9. Rozendaal, A. and Philander, C. Recovery of duricrust sterilized heavy mineral resources at the Namakwa Sands Mine South Africa: a geometallurgical challenge, The 6th International Heavy Mineral Conference 'Back to Basics', The Southern African Institute of Mining and Metallurgy, 2007. pp. 133-138.         [ Links ]

10. Deer, W. A., Howie, R. A., and Zussman, J. An Introdution to rock-forming minerals. Longman Scientific and Technical, 1992. 696 pp.         [ Links ]

11. Force, E.R. Placer Deposits. Rev. Econ.Geol, vol. 5, 1991. pp. 131-139.         [ Links ]

12. Zack, T., Kronz, A., Foley, S. F., and Rivers, T. Trace element abundances in rutiles from eclogites and associated garnet mica schists. Chemical Geology, vol. 184, 2002. pp. 97-122.         [ Links ]

13. Zack, T., Moraes, R., and Kronz, A. Temperature dependence of Zr in rutile: empirical calibration of a rutile thermometer. Contribution to Mineralogy and Petrology, vol. 148, 2004. pp. 471-488.         [ Links ]

14. Philander, C and Rozendaal, A. Mineral intricacies of the Namakwa Sands mineral resource. The 7th International Heavy Minerals Conference ' What next', The Southern African Institute of Mining and Metallurgy, 2009.         [ Links ]

15. Meinhold, G., Anders, B., Kostopoulos, D., and Reischmann, T. Rutile chemistry and thermometry as provenance indicator: an example from Chios Island Greece. Sedimentary Geology, vol. 203, 2008. pp. 98-111.         [ Links ]

16. Tomkins, H. S., Powell, R., and Ellis, D.J. The pressure dependence of the zirconium-in-rutile thermometer. J Metamorphic Geol., vol. 25, 2007. pp. 703-713.         [ Links ]

17. Triebold, S., von Eynaten, H., Luiz Luvizotto, G., and Zack, T. Deducing source rock lithology from detrital rutile chemistry: An example from the Erzebirge, Germany. Chemical Geology, vol. 244, 2007. pp. 42-426.         [ Links ]

18. Watson, E.B., Wark, D.A., and Thomas, J.B. Crystallisation thermometers for zircon and rutile. Contribution to Mineralogy and Petrology, vol. 151, 2006. pp. 413-433.         [ Links ]

19. Waters, D.J., Joubert, P., and Moore, J.M. A suggested re-interpretation of Namaqua basement and cover rocks south and west of Bitterfontein. Transactions of the Geological Society of South Africa, vol. 86, 1983. pp. 293-299.         [ Links ]

20. Ramdohr, P. Ore minerals and their intergrowths. Pergamon Press, 1982. p. 1207.         [ Links ]

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License