Cryptic mineral variation and PGE distribution in the Merensky Reef and its discontinuous mela-gabbronoritic hanging wall (“Brown Sugar Norite” - BSN) at Two Rivers Platinum Mine, Eastern Bushveld Complex, South Africa

2016 ◽  
Vol 119 (1) ◽  
pp. 243-272 ◽  
Author(s):  
J.J. Beukes ◽  
C.D.K. Gauert ◽  
R.J. Giebel
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Hanging Wall ◽  
Brown Sugar ◽  
Merensky Reef

A Comparative Study of Sulfur Isotope Variations within the Flatreef and Merensky Reef of the Bushveld Complex, South Africa

2021 ◽  
Vol 59 (6) ◽  
pp. 1363-1380
Author(s):  
Jarlen J. Keet ◽  
Frederick Roelofse ◽  
Christoph D.K. Gauert ◽  
Danie Grobler ◽  
Mike Butler
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Hanging Wall ◽  
Merensky Reef ◽  
Cyclic Unit ◽  
Heterogeneous Nature ◽  
Platinum Mining ◽  
Eastern Limb ◽  
New Perspective ◽  
S Isotope

ABSTRACT The Flatreef, a down-dip, sub-horizontal extension of the Platreef, which underlies the Turfspruit and Macalacaskop farms, represents the future of platinum mining in South Africa. The stratigraphic connection between the Platreef, located at the base of the northern limb of the Bushveld Complex, and the Merensky Reef in the western and eastern limbs of the complex, was disputed for many years due to the heterogeneous nature of the Platreef along strike. However, the discovery of the Flatreef led to a new perspective on the Platreef as the former allowed for the study of a magmatic stratigraphy less affected by footwall interaction. Here, we report whole-rock S isotope (δ34S) compositions across the stratigraphic units of the Flatreef and its footwall and hanging wall as intersected by boreholes UMT-276 and UMT-393, as well as stratigraphic units of the Merensky Reef at Two Rivers Platinum mine in the eastern limb. The units of the Flatreef containing platinum group element mineralization, namely the Main Reef and Upper Reef, have δ34S values that overlap with the range recorded for the Merensky Reef in the western and eastern limbs. In UMT-393, Main Reef δ34S values range between 0.2 and 1.5‰ (with the exception of three outliers, 9.7‰, 11.1‰, and 7.9‰), and 0.52‰ and 11.2‰ for two Upper Reef samples. However, in UMT-276, Main Reef δ34S values range between –0.96 and 2.24‰ and 3.19‰ was recorded for an Upper Reef sample. The S isotope compositions recorded for the Merensky Reef pyroxenite at Two Rivers Platinum mine are relatively higher with δ34S values ranging between 1.24 and 4.83‰. The top unit of the Flatreef, which is a transition zone below the Main Zone, as well as the Footwall Cyclic Unit have heavier S isotope compositions with δ34S values ranging between 6 and 17‰ for the former and 0.7 and 18.6‰ for the latter. At Two Rivers Platinum mine, the hanging-wall anorthosite has a δ34S value of 2.9‰ in contrast to the 5.7‰ measured for the footwall anorthosite and 3.27‰ for the footwall feldspathic pyroxenite. The consistent near-mantle S isotope signature and accompanying metal enrichment in the Main Reef of the Flatreef may be explained by extensive interaction of sulfide minerals in a Lower Zone conduit/pre-Platreef staging chamber with large volumes of uncontaminated magma. The δ34S values of the Merensky Reef at Two Rivers Platinum mine are slightly higher compared to that of the Main Reef at Turfspruit and Macalacaskop possibly due to interaction with underlying carbonate rocks.

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.

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

scholarly journals An overview of global layered intrusions, with a special focus on the Bushveld Complex, South Africa

2021 ◽  
Author(s):  
W.D. Maier ◽  
◽  
Qun-Ke Xia ◽  
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Ore Deposits ◽  
Reactive Flow ◽  
Special Focus ◽  
Potential Importance ◽  
Layered Intrusions ◽  
Merensky Reef ◽  
Research Questions ◽  
Water Contents

Layered intrusions host some of the world’s most important ore deposits, yet their global distribution, age, and petrogenesis remain poorly known. Here we provide an update on our current understanding and highlight some key outstanding research questions, notably on the potential importance of reactive flow. We present some preliminary data on water contents of Bushveld orthopyroxenes from which we calculated the water contents of the magma. The analysed Bushveld rocks, including the Merensky Reef, crystallised from relatively water-poor magma, similar to many other continental basalts.

Re-evaluation of magma compositions and processes in the uppermost Critical Zone of the Bushveld Complex

1996 ◽  
Vol 60 (398) ◽  
pp. 131-148 ◽  
Author(s):  
R. Grant Cawthorn
Keyword(s):  
Bushveld Complex ◽  
Hanging Wall ◽  
Experimental Studies ◽  
Critical Zone ◽  
Element Abundances ◽  
Merensky Reef ◽  
Low Viscosity ◽  
Silicate Magma ◽  
Geochemical Study ◽  
Restricted Mobility

AbstractA detailed geochemical study is presented of the uppermost Critical Zone, especially of the footwall and hanging wall to the Merensky Reef, at Impala Platinum Mines in the Bushveld Complex. The approximately 100 m-thick sequence below the Merensky Reef consists of 13 distinct layers which have sharp boundaries. They are adcumulates with varying proportions of cumulus plagioclase, orthopyroxene and chromite.Experimental studies on the composition of coexisting orthopyroxene liquid indicate that the magma which produced this sequence contained between 4 and 6% MgO. The magma from which the Merensky Reef formed was more evolved than the footwall magma.Significant variations exist for both the En content of orthopyroxene and mg# number of whole-rock analyses in short vertical sections. Pyroxenite and norite always have higher values than anorthosite. Extremely sharp breaks in these values correlate with changes in modal proportions, and argue against both significant fractionation within the studied interval, and infiltration metasomatism. Quantitative modelling shows that the entire footwall section could have contained pyroxene with a uniform primary composition of En82, and that all the variation now observed reflects the effect of reaction with trapped magma.Two independent methods for determining the proportion of trapped liquid are presented, based on mg# number and incompatible element abundances. Both yield a uniform proportion in all samples of approximately 10%. Immiscible sulphide liquid from the Merensky Reef can be shown to have infiltrated downwards for <5 m, despite its high density contrast with silicate magma, very low viscosity and low crystallization temperature. Residual silicate magma would have had even more restricted mobility. The migration of residual liquid or fluid through pothole structures in the floor of the Merensky Reef is not supported by the present data.

Multiple Merensky Reef of the Bushveld Complex, South Africa

2019 ◽  
Vol 174 (3) ◽  
Author(s):  
Sofya Chistyakova ◽  
Rais Latypov ◽  
Kirsten Youlton
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Merensky Reef
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