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Experimental data at 3 kbars pressure on parental magma to the Bushveld Complex

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Abstract

Experimental studies, mainly under 3 kbars pressure, have been undertaken on representative samples to determine if any of these compositions could be parental magma to the Bushveld Complex. One such composition, with 12.5% MgO, Mg/(Mg + Fe) of 0.72 and quartz-normative, crystallizes olivine, Fo88, as liquidus mineral, at about 1,300° C, followed at only slightly lower temperature by orthopyroxene at 3 kbars pressure. There is a temperature drop of over 100° C before the appearance of plagioclase and finally clinopyroxene. This crystallization sequence is in excellent agreement with the observed sequence in the lower part of the Bushveld Complex.

Results at higher pressures show that this composition cannot be a partial melt from mantle peridotite because olivine is replaced by orthopyroxene as the liquidus mineral at lower crustal pressures. A combination of olivine fractionation and contamination was probably involved in the early evolution of this magma.

Experimental data on the other compositions show that they are not suitable as parental magma to the lowest portion of the complex. However, the data are used to construct phase diagrams within the basalt tetrahedron at 3 kbars pressure, which are of relevance to the crystallization of basic magmas in the upper crust.

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References

  • Bender JF, Hodges FN, Bence AE (1978) Petrogenesis of basalts from the project FAMOUS, experimental study from 0 to 15 kbars. Earth Planet Sci Lett 41:277–302

    Google Scholar 

  • Bickle MJ, Ford CE, Nisbett EG (1977) The petrogenesis of peridotitic komatiites: evidence from high-pressure melting experiments. Earth Planet Sci Lett 37:97–106

    Google Scholar 

  • Biggar GM (1974) Phase equilibria studies of the chilled margins of some layered intrusions. Contrib Mineral Petrol 46:159–167

    Google Scholar 

  • Cameron EN (1978) The lower Zone of the Eastern Bushveld Complex in the Olifants River Trough. J Petrol 19:437–462

    Google Scholar 

  • Cameron EN (1980) Evolution of the Lower critical zone, central sector, eastern Bushveld Complex, and its chromite deposits. EconGeol 75:845–871

    Google Scholar 

  • Carlson RW, Lugmair GW, Macdougall JD (1981) Crustal influence in the generation of continental flood basalts. Nature 289:160–162

    Google Scholar 

  • Carter SR, Evensen NM, Hamilton PJ, O'Nions RK (1978) Neodymium and strontium isotope evidence for crustal contamination of continental volcanics. Science 202:743–746

    Google Scholar 

  • Cawthorn RG, Ford CE, Biggar GM, Bravo MS, Clarke DB (1973) Determination of the liquid composition in experimental samples: discrepancies between microprobe analysis and other methods. Earth Planet Sci Lett 21:1–5

    Google Scholar 

  • Cawthorn RG, Biggar GM, Graham CM, Graham A, Ford CE, Sharpe MR, Davies G (1979) Experimental petrological data on the parental magmas to the Bushveld Complex. Institute of Geological Research on the Bushveld Complex, University of Pretoria 18:1–27

    Google Scholar 

  • Cawthorn RG, Davies G, Clubley-Armstrong A, McCarthy TS (1981) Sills associated with the Bushveld Complex, South Africa: an estimate of the parental magma composition. Lithos 14:1–15

    Google Scholar 

  • Davies G, Cawthorn RG, Barton JM Jr, Morton M (1980) Parental magma to the Bushveld Complex. Nature 287:33–35

    Google Scholar 

  • Eggler DH (1972) Water saturated and undersaturated melting relations in a Paricutin andesite and an estimate of water content in the natural magmas. Contrib Mineral Petrol 34:261–271

    Google Scholar 

  • Eggler DH (1974) Effect of CO2 on the melting of peridotite. Carnegie Inst Wash Yearb 73:215–224

    Google Scholar 

  • Ford CE (1972) Furnace design, temperature distribution, calibration and seal design in internally heated pressure vessels. Progress in Experimental Petrology; Natural Environment Research Council, London 2:89–96

    Google Scholar 

  • Ford CE (1978) Platinum-iron alloy sample containers for melting experiments on iron-bearing rocks, minerals and related systems. Mineral Mag 42:271–275

    Google Scholar 

  • Green DH (1981) Petrogenesis of Archaean ultramafic magmas and implications for Archaean tectonics. In: Kroner A, ed. Precambrian Plate Tectonics. Elsevier Amsterdam:469–489

    Google Scholar 

  • Green DH, Ringwood AE (1967) The genesis of basaltic magmas. Contrib Mineral Petrol 15:103–190

    Google Scholar 

  • Hamilton PJ (1977) Sr isotope and trace element studies of the Great Dyke and Bushveld mafic phase and their relation to early Proterozoic magma genesis in southern Africa. J Petrol 18:24–52

    Google Scholar 

  • Holloway JR, Burnham CW (1982) Melting relations of basalt with equilibrium water pressure less than total pressure. J Petrol 13:1–29

    Google Scholar 

  • Irvine TN (1970) Crystallization sequences in the Muskox intrusion and other layered intrusions. Geol Soc S Afr Spec Publ 1:441–476

    Google Scholar 

  • Jaques AL, Green DH (1979) Determination of liquid compositions in high-pressure melting of peridotite. Am Mineral 64:1312–1321

    Google Scholar 

  • Jaques AL, Green DH (1980) Anhydrous melting of peridotite at 0–15 Kb pressure and the genesis of tholeiitic basalts. Contrib Mineral Petrol 73:287–310

    Google Scholar 

  • Kushiro I (1969) The system forsterite-diopside-silica with and without water at high pressures. Am J Sci 267A (Schairer vol.):269–294

    Google Scholar 

  • Kushiro I, Thompson RN (1972) Origin of some abyssal tholeiites from the Mid-Atlantic Ridge. Carnegie Inst Wash Yearb 71:403–406

    Google Scholar 

  • McCarthy TS, Cawthorn RG (1980) Changes in initial Sr87/Sr86 ratio during protracted fractionation in igneous complexes. J Petrol 21:245–264

    Google Scholar 

  • Molyneux TG (1974) A geological investigation of the Bushveld Complex in Sekhukhuneland and part of the Steelpoort valley. Trans Geol Soc S Afr 77:329–338

    Google Scholar 

  • O'Hara MJ (1968) The bearing of phase equilibria studies in synthetic and natural systems on the origin and evolution of basic and ultrabasic rocks. Earth Sci Rev 4:69–113

    Google Scholar 

  • Roeder PL, Emslie RF (1970) Olivine-liquid equilibrium. Contrib Mineral Petrol 29:275–289

    Google Scholar 

  • Sharpe MR (1978) “Cone-type” dia bases from the eastern Transvaal — representatives of a quenched magma. Trans Geol Soc S Afr 81:373–378

    Google Scholar 

  • Sharpe MR (1981) The chronology of magma influxes to the eastern compartment of the Bushveld Complex as exemplified by its marginal border groups. J Geol Soc London 138:307–326

    Google Scholar 

  • Sharpe MR (1982) Noble metals in the marginal rocks of the Bushveld Complex. Econ Geol 77:1286–1295

    Google Scholar 

  • Stolper E (1980) A phase diagram for mid-ocean ridge basalts: preliminary results and implications for petrogenesis. Contrib Mineral Petrol 74:13–27

    Google Scholar 

  • Tatsumi Y (1982) Origin of high-magnesian andesites in the Setouchi volcanic belt, southwest Japan, II: Melting phase relations at high pressures. Earth Planet Sci Lett 60:305–317

    Google Scholar 

  • Thompson RN (1972) Melting behaviour of two Snake River lavas at pressures up to 35 kbar. Carnegie Inst Wash Yearb 71:406–410

    Google Scholar 

  • Tilley CE, Yoder HS Jr, Schairer JF (1968) Melting relations of igneous rock series. Carnegie Inst Wash Yearb 66:450–457

    Google Scholar 

  • van Rensburg WCT (1965) The geology of the Dwars River fragment, Lydenburg District, Transvaal. Ann Geol Surv S Afr 4:69–78

    Google Scholar 

  • Vermaak CF (1976) The Merensky Reef — thoughts on its environment and genesis. Econ Geol 71:1270–1298

    Google Scholar 

  • Vermaak CF, von Gruenewaldt G (1981) Third International Platinum Symposium, Pretoria. Guide to the Bushveld excursion. Geol Soc S Afr, Johannesburg, 59 pp

    Google Scholar 

  • von Gruenewaldt G (1968) The Rooiberg felsite north of Middelburg and its relation to the layered sequence of the Bushveld Complex. Trans Geol Soc S Afr 71:153–172

    Google Scholar 

  • von Gruenewaldt G (1973) The modified differentiation index and the modified crystallization index as parameters of differentiation in layered intrusions. Trans Geol Soc S Afr 76:52–61

    Google Scholar 

  • Wager LR, Brown GM (1968) Layered Igneous Rocks. Oliver and Boyd, Edinburgh and London, 588 pp

    Google Scholar 

  • Willemse J (1959) The “floor” of the Bushveld Igneous Complex and its relationships, with special reference to the Eastern Transvaal. Proc Geol Soc S Afr 62:21–80

    Google Scholar 

  • Williams DAC, Hallberg JA (1973) Archean layered intrusions of the eastern goldfield region, Western Australia. Contrib Mineral Petrol 38:45–70

    Google Scholar 

Download references

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Authors and Affiliations

  1. Geology Department, University of the Witwatersrand, 1, Jan Smuts Avenue, 2001, Johannesburg, South Africa

    R. G. Cawthorn & G. Davies

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  1. R. G. Cawthorn
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  2. G. Davies
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Research undertaken at the Grant Institute of Geology, University of Edinburgh, Scotland

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Cawthorn, R.G., Davies, G. Experimental data at 3 kbars pressure on parental magma to the Bushveld Complex. Contr. Mineral. and Petrol. 83, 128–135 (1983). https://doi.org/10.1007/BF00373085

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