Petrogenesis of the Merensky Reef in the Rustenburg section of the Bushveld Complex

1991 ◽  
Vol 107 (3) ◽  
pp. 293-309 ◽  
Author(s):  
D. M. Nicholson ◽  
E. A. Mathez
Keyword(s):  
Bushveld Complex ◽  
Merensky Reef

scholarly journals Contamination of the Bushveld Complex (South Africa) magmas by basinal brines: Stable isotopes in phlogopite from the UG2 chromitite

Geology ◽  
2021 ◽  
Author(s):  
Haoyang Zhou ◽  
Robert B. Trumbull ◽  
Ilya V. Veksler ◽  
Ilya N. Bindeman ◽  
Johannes Glodny ◽  
...  
Keyword(s):  
South Africa ◽  
Stable Isotopes ◽  
Hydrogen Isotope ◽  
Bushveld Complex ◽  
Isotope Ratios ◽  
Second Step ◽  
Merensky Reef ◽  
Oxygen Isotope Ratios ◽  
Abundant Evidence ◽  
Hydrogen Isotope Ratios

There is abundant evidence for significant H2O in evolved melts from the platinum-rich UG2 chromitite and the Merensky Reef of the Bushveld Complex (South Africa), but there is no consensus about the source of H2O. We report triple-oxygen and hydrogen isotope ratios of interstitial, late-magmatic phlogopite from three localities of the UG2 layer. The phlogopite yielded δD values of –43‰ to –23‰, which is >30‰ higher than previously known from Bushveld rocks and far above the mantle values of ~–75‰. The phlogopite triple-oxygen isotope ratios are the first to be reported for Bushveld rocks, with values of Δ′17O0.5305 (17O excess relative to the reference line 0.5305) from –0.069‰ to –0.044‰ (δ18O 5.2‰–6.2‰). The oxygen data support existing models of as much as 30%–40% contamination of mantlederived magmas in the lower to middle crust. However, the high δ values require a second step of contamination, which we attribute to brines from the marine sediments in the Transvaal Basin at the emplacement level.

The UG2-Merensky Reef interval of the Bushveld Complex northwest of Pretoria

1996 ◽  
Vol 31 (5) ◽  
pp. 386-393
Author(s):  
W. D. Maier ◽  
M. P. Bowen
Keyword(s):  
Bushveld Complex ◽  
Merensky Reef

The UG2?Merensky Reef interval of the Bushveld Complex northwest of Pretoria

1996 ◽  
Vol 31 (5) ◽  
pp. 386-393 ◽  
Author(s):  
W. D. Maier ◽  
M. P. Bowen
Keyword(s):  
Bushveld Complex ◽  
Merensky Reef

Concentrations of Te, As, Bi, Sb (TABS) and Se in the Marginal Zone of the Bushveld Complex: evidence for crustal contamination and the nature of the magma that formed the Merensky Reef

2020 ◽  
Author(s):  
Eduardo Mansur ◽  
Sarah-Jane Barnes
Keyword(s):  
Marginal Zone ◽  
Bushveld Complex ◽  
Crustal Contamination ◽  
Sulfide Minerals ◽  
Sulfide Liquid ◽  
Liquid Component ◽  
Merensky Reef ◽  
Chalcophile Elements ◽  
Magmatic Sulfide ◽  
Primary Magmas

<p>The association of platinum-group elements (PGE) and the chalcophile elements Te, As, Bi, Sb and Sn (TABS) has been documented in several magmatic sulfide deposits. These groups of elements are either hosted within sulfide minerals, or combine to form discrete platinum-group minerals (PGM) associated with sulfide minerals. However, the concentration of TABS in parental magmas from which magmatic sulfide deposits formed was still missing. This study presents the distribution of TABS and Se in B-1, B-2 and B-3 rocks of the Marginal Zone of the Bushveld Complex. These rocks have been proposed as representative of the parental liquids from which the Bushveld Complex crystallized, thus allowing us to assess the concentration of Se and TABS in the liquids from which some of the largest PGE deposits in the world have formed. Concentrations of As and Sb in the initial Bushveld liquid (B-1) are significantly higher than in primary magmas, whereas the Se and TABS of later magmas (B-2 and B-3) are similar to primary magmas. We attribute the difference due upper crustal contamination of the B-1 magma, whereas the B-2 and B-3 magmas were most likely contaminated with a plagioclase-rich residuum formed upon the partial melting of the upper crust. Moreover, we modeled the concentrations of the TABS in the Merensky Reef using a mixture of two of the magma types present in the Marginal Zone (the B-1 and B-2) as the initial silicate liquid. The modeled concentrations closely resemble the measured values obtained for a section across the Merensky Reef at the Impala mine. This supports the B-1 and B-2 mixture as an appropriate initial liquid for the crystallization of the Merensky Reef. The modeling also shows that the distributions of Se, Te and Bi across the Merensky Reef are controlled by the sulfide liquid component. In contrast, As and Sb distributions are influenced both by the amount of silicate melt component in the cumulates and the sulfide liquid component. This is because Se, Te and Bi are moderately to strongly chalcophile elements, but As and Sb are only slightly chalcophile elements. Consequently, the effect of crustal contamination for elements with high partition coefficients between sulfide and silicate liquid (Te, Bi and Se) is obscured by the interaction of sulfides with a large volume of silicate magma. Therefore, the concentrations of these elements are higher in samples with greater proportions of sulfide minerals. In contrast, for elements with lower partition coefficients (As and Sb), the whole-rock concentrations are not upgraded by the presence of sulfide minerals, and thus the effect of crustal contamination can be more readily assessed.</p>

PGE enrichment in chromitite layers and the Merensky Reef of the western Bushveld Complex; a Re–Os and Rb–Sr isotope study

1999 ◽  
Vol 172 (1-2) ◽  
pp. 49-64 ◽  
Author(s):  
Ronny Schoenberg ◽  
F. Johan Kruger ◽  
Thomas F. Nägler ◽  
Thomas Meisel ◽  
Jan D. Kramers
Keyword(s):  
Bushveld Complex ◽  
Sr Isotope ◽  
Merensky Reef ◽  
Isotope Study
Sign in / Sign up

Export Citation Format

Share Document