Great Dyke
The Great Dyke or Dike is a linear geological feature that trends nearly north-south through the centre of Zimbabwe passing just to the west of the capital, Harare. It consists of a band of short, narrow ridges and hills spanning for approximately 550 kilometres (340 mi). The hills become taller as the range goes north, and reach up to 460 metres (1,510 ft) above the Mvurwi Range. The range is host to vast ore deposits, including gold, silver, chromium, platinum, nickel and asbestos.[1]
Northern end | 16°27′51″S 31°08′24″E / 16.46417°S 31.14000°E |
Southern end | 20°50′22″S 29°39′04″E / 20.83944°S 29.65111°E |
Geology and soils
Geologically the Great Dyke is not a dyke, but is lopolithic[2] and Y-shaped in cross-section. It is a group of layered ultramafic intrusions that extend across Zimbabwe with a strike of about N20°E. The width of the intrusions vary from 3 to 12 km (7.5 mi). The Great Dyke is unusual in that most ultramafic layered intrusions display near horizontal sill or sheet forms.
The well-layered lower units of ultramafic rocks comprising the Great Dyke are locally overlain by erosional remnants of
The dyke lies within the Zimbabwe Craton and has been dated at 2.575 billion years old.[5] The Great Dyke acts as a strain-marker for the craton: The fact that it has been undeformed since intrusion (excluding the Musengezi area) shows that the craton had stabilised by the time the Dyke intruded.[6]
Two
Soils on the Great Dyke are strongly influenced by the underlying bedrock. Shallow, infertile
The Great Dyke is a strategic economic resource with significant quantities of chrome and platinum.
Development
The Great Dyke was first reported in 1867 by the explorer Karl Mauch. However the existence of platinum was not realized until 1918, and mining of oxidized ores did not start until in 1924.[11]
Chromite is mined throughout the Dyke, especially in the Darwendale, Lalapanzi and Mutorashanga areas. The three largest chrome mining companies are Maranatha Ferrochrome, Zimalloys and Zimasco,[12] although most mines are worked by the tribute system.
See also
References
- ISBN 0-7167-1456-6
- ^ Hughes, Charles James (1970) Lateral Cryptic Variation in the Great Dyke of Rhodesia, Geological Magazine, Volume 107, Issue 4, pages 319-325 [1]. Retrieved 2013-12-01.
- ^ ISBN 978-1-870706-06-3
- ^ ISBN 978-1-870706-06-3
- ^ Oberthuer, T., Davis, D.W., Blenkinsop, T.G., Hoehndorf, A., 2002. Precise U–Pb mineral ages, Rb–Sr and Sm–Nd systematics for the Great Dyke, Zimbabwe—constraints on crustal evolution and metallogenesis of the Zimbabwe Craton. Precambrian Research, 113, 293–306.[2]
- ^ Dirks, P.H.G.M. and Jesma, H.A. 2002. Crust–mantle decoupling and the growth of the Archaean Zimbabwe craton. Journal of African Earth Sciences, 34, 157–166 [3]
- ISSN 0301-9268.
- ISSN 1464-343X.
- ^ https://esdac.jrc.ec.europa.eu/images/Eudasm/Africa/images/maps/download/afr_zw2006_so.jpg Provisional Soil Map of Zimbabwe Rhodesia (1980)
- ^ Stribrny, B., Wellmer, F.-W., Burgath, K.-P., Oberthür, T., Tarkian, M. and Pfeiffer, T. 2000. Unconventional PGE occurrences and PGE mineralization in the Great Dyke: metallogenic and economic aspects. Mineralium Deposita, 35, 260-281. [4]
- ^ Zientek, M.L.; Causey, J.D.; Parks, H.L.; Miller, R.J. (2014). Platinum-group elements in southern Africa—Mineral inventory and an assessment of undiscovered mineral resources: U.S. Geological Survey Scientific Investigations Report 2010–5090–Q (PDF). U.S. Dept. of the Interior, USGS. pp. 14–18. Retrieved 24 March 2019.
- ^ Africa: Mining - Chromite Mining Mbendi
- ^ Platinum occurrences on the Great Dyke Zimplats website Archived 2005-11-25 at the Wayback Machine
- ^ Why existing investors are unenthusiastic about Zimbabwe sanctions Zimbabwe Review
- ^ Locmelis, M., Melcher, F., Oberthür, T. 2010. Platinum-group element distribution in the oxidized Main Sulfide Zone, Great Dyke, Zimbabwe.Mineralium Deposita, 45, 93-109. [5]
- ^ Oberthür, T., Melcher, F., Buchholz, P., Locmelis, M. 2012. The oxidized ores of the Main Sulfide Zone, Great Dyke, Zimbabwe: Turning resources into minable reserves – mineralogy is the key.In: Platinum 2012, The Southern African Institute of Mining and Metallurgy (SAIMM), Symposium Series, S72, 647-672. [6]