Parental magma composition inferred from trace element in cumulus and intercumulus silicate minerals: An example from the Lower and Lower Critical Zones of the Bushveld Complex, South-Africa

Lithos ◽  
2011 ◽  
Vol 125 (1-2) ◽  
pp. 537-552 ◽  
Author(s):  
Bélinda Godel ◽  
Sarah-Jane Barnes ◽  
Wolfgang D. Maier
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Bushveld Complex ◽  
Parental Magma ◽  
Silicate Minerals ◽  
Magma Composition ◽  
Critical Zones

scholarly journals Parental magma composition of the Main Zone of the Bushveld Complex: Evidence from in-situ LA-ICP-MS trace element analysis of silicate minerals in the cumulate rocks

2020 ◽  
Author(s):  
Shenghong Yang ◽  
Wolfgang D. Maier ◽  
Belinda Godel ◽  
Sarah-Jane Barnes ◽  
Eero Hanski ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Bushveld Complex ◽  
Trace Element Analysis ◽  
Parental Magma ◽  
Main Zone ◽  
Element Analysis ◽  
Silicate Minerals ◽  
Incompatible Elements

<p>In-situ trace element analysis of cumulus minerals may provide a clue to the parental magma from which the minerals crystallized. However, this is hampered by effects of the trapped liquid shift (TLS). In the Main Zone (MZ) of the Bushveld Complex, the Ti content in plagioclase grains shows a clear increase from core to rim, whereas most other elements (e.g., rare earth elements (REEs), Zr, Hf, Pb) do not. This is different from the prominent intra-grain variation of all trace elements in silicate minerals in mafic dikes and smaller intrusion, which have a faster cooling rate. We suggest that crystal fractionation of trapped liquid occurred in the MZ of Bushveld and the TLS may have modified the original composition of the cumulus minerals for most trace elements except Ti during slow cooling. Quantitative model calculations suggest that the influence of the TLS depends on the bulk partition coefficient of the element. The effect on highly incompatible elements is clearly more prominent ­­than on moderately incompatible and compatible elements because of different concentration gradients between cores and rims of cumulate minerals. This is supported by the following observations in the MZ of Bushveld: 1) positive correlation between Cr, Ni and Mg# of clinopyroxene and orthopyroxene, 2) negative correlation between moderately incompatible elements (e.g., Mn and Sc in clinopyroxene and orthopyroxene, Sr, Ba, Eu in plagioclase), but 3) poor correlation between highly incompatible elements and Mg# of clinopyroxene and orthopyroxene or An# of plagioclase. Modeling suggests that the extent of the TLS for a trace element is also dependent on the initial fraction of the primary trapped liquid, with strong TLS occurring if the primary trapped liquid fraction is high. This is supported by the positive correlation between highly incompatible trace element abundances in cumulus minerals and whole-rock Zr contents.</p><p>We have calculated the composition of the parental magma of the MZ of the Bushveld Complex. The compatible and moderately incompatible element contents of the calculated parental liquid are generally similar to those of the B3 marginal rocks, but different from the B1 and B2 marginal rocks. For the highly incompatible elements, we suggest that the use of the sample with the lowest whole-rock Zr content and the least degree of TLS is the best approach to obtain the parental magma composition. Based on calculation, we propose that a B3 type liquid is the most likely parental magma to the MZ of the Bushveld Complex.</p>

Sills associated with the Bushveld Complex, South Africa: an estimate of the parental magma composition

Lithos ◽  
1981 ◽  
Vol 14 (1) ◽  
pp. 1-16 ◽  
Author(s):  
R. Grant Cawthorn ◽  
G. Davies ◽  
A. Clubley-Armstrong ◽  
T.S. McCarthy
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Parental Magma ◽  
Magma Composition

Caveats in defining the magmas parental to the mafic rocks of the Bushveld Complex, and the manner of their emplacement: review and commentary

2002 ◽  
Vol 66 (6) ◽  
pp. 815-832 ◽  
Author(s):  
H. V. Eales
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Bushveld Complex ◽  
Bulk Composition ◽  
Trace Element Data ◽  
Mafic Rocks ◽  
Critical Zones ◽  
Derivatives Of ◽  
Western Limb ◽  
Northern Sector

Abstract The composition of magmas proposed as parental to the layered suite of the Bushveld Complex, and some models for the manner of their emplacement, are reviewed briefly. Included are some contributions published in South Africa, with which overseas readers might be less familiar. Emphasis is given to the broader features of the cumulates, and the contradictions raised by whole-rock compositional, Sr-isotopic, and trace-element data that cloud their correlation with proposed parental magmas. It is concluded that the Lower, Critical and Main Zones are the derivatives of only two primary magmatic lineages, while a third was added to residual liquids from which the layered rocks above the Pyroxenite Marker were formed. Excessive amounts of olivine and chromium in the cumulates of the Lower and Lower Critical Zones in the northern sector of the Western Limb can seemingly not be accounted for by the composition and volume of the putative magmas. This is attributed to (1) this sector being a proximal facies located close to the original feeder, and/or (2) crystal-charged magma batches, expelled from a lower magma chamber, being periodically injected into and dispersed within the liquids already in place in the Bushveld chamber. Thus, ongoing changes in the bulk composition of the liquids within the chamber would not be reflected in the rinds of earlier, chilled-facies rocks. The expulsion of significant volumes of liquid residua from the chamber during cumulate deposition is not ruled out.

Oxygen isotope and trace element compositions of platiniferous dunite pipes of the Bushveld Complex, South Africa – Signals from a recycled mantle component?

Lithos ◽  
2018 ◽  
Vol 310-311 ◽  
pp. 332-341 ◽  
Author(s):  
T. Günther ◽  
K.M. Haase ◽  
M. Junge ◽  
T. Oberthür ◽  
D. Woelki ◽  
...  
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Oxygen Isotope ◽  
Bushveld Complex ◽  
Mantle Component

Isotope and trace-element patterns below the Merensky Reef, Bushveld Complex, South Africa: evidence for fluids?

1993 ◽  
Vol 106 (1-2) ◽  
pp. 171-186 ◽  
Author(s):  
D.L. Reid ◽  
R.G. Cawthorn ◽  
F.J. Kruger ◽  
M. Tredoux
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Bushveld Complex ◽  
Merensky Reef

Trace-element study and age dating of zircon from chromitites of the Bushveld Complex (South Africa)

2013 ◽  
Vol 107 (6) ◽  
pp. 915-942 ◽  
Author(s):  
Marina Yudovskaya ◽  
Judith Kinnaird ◽  
Anthony J. Naldrett ◽  
Nickolay Rodionov ◽  
Anton Antonov ◽  
...  
Keyword(s):  
South Africa ◽  
Trace Element ◽  
Bushveld Complex ◽  
Age Dating ◽  
Trace Element Study ◽  
Element Study
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