Zonation of Merensky-Style Platinum-Group Element Mineralization in Turfspruit Thick Reef Facies (Northern Limb of the Bushveld Complex)*

2017 ◽  
Vol 112 (6) ◽  
pp. 1333-1365 ◽  
Author(s):  
Marina A. Yudovskaya ◽  
Judith A. Kinnaird ◽  
Danie F. Grobler ◽  
Gelu Costin ◽  
Vera D. Abramova ◽  
...  
Keyword(s):  
Platinum Group Element ◽  
Bushveld Complex ◽  
Group Element ◽  
Reef Facies ◽  
Northern Limb ◽  
Platinum Group

PGE distribution in Merensky wide-reef facies of the Bushveld Complex, South Africa: Evidence for localized hydromagmatic control

2021 ◽  
Vol 59 (6) ◽  
pp. 1305-1338
Author(s):  
Stephen A. Prevec ◽  
Savvas Anthony Largatzis ◽  
William Brownscombe ◽  
Tobias Salge
Keyword(s):  
Platinum Group Element ◽  
Bushveld Complex ◽  
Platinum Group Elements ◽  
Group Element ◽  
Primitive Mantle ◽  
Reef Facies ◽  
Element Abundances ◽  
Merensky Reef ◽  
Element Concentrations ◽  
Platinum Group

ABSTRACT The wide-reef facies of the Merensky Reef in the eastern part of the western lobe of the Bushveld Complex was sampled in order to better resolve otherwise spatially constrained variation in highly siderophile elements across this geological unit. The platinum group element mineralogy and whole-rock highly siderophile element concentrations were measured across two vertical sections in close proximity. In one section, the Merensky Reef unit was bound by top and bottom platinum group elements-enriched horizons (reefs) with a well-developed pegmatoidal phase in the top third of the intrareef pyroxenite, but with neither a top nor a bottom chromitite present. The other drill core section featured a thin (<1 cm thick) chromitite layer associated with the highest platinum group element concentrations of any rock in this study as the bottom reef, but with a chromitite-absent top reef, and very poor development of the pegmatoid. Primitive mantle-normalized profiles of the main lithological units show relatively flat, primitive mantle-like highly siderophile element abundances (Cr, V, Co, Ni, platinum group elements, Au and Cu) in the Merensky pyroxenite, with modest depletion in Ir-affiliated platinum group elements. The platinum group element-rich top and bottom reefs, and the pegmatoidal upper pyroxenites, display characteristic enrichment in the Pt-affiliated platinum group elements and undepleted Ir-affiliated platinum group elements. The leuconoritic hanging wall and footwall rocks show comparable highly siderophile element profiles, distinguished from one another by relative depletion in the Pt-affiliated platinum group elements of the footwall samples. The vertical variation in highly siderophile element abundances through both sections is characterized by low platinum group element abundances through the lower reef pyroxenite, with platinum group element, Au, and Cu ± Ni concentrations increasing through the upper pegmatoidal pyroxenite, and main enrichment peaks at the top and bottom reefs. Significant localized (centimeter-scale) zones of chalcophile metal depletion are present immediately above the top reef and below the bottom reef. In addition, a wider zone of Pt-affiliated platinum group elements (with Pd more depleted than Pt)-depletion was identified within the pegmatoidal pyroxenite around one meter below the top reef. The platinum group element mineralogy of the bottom reef consists mainly of platinum group element sulfides, with minor arsenides and antimonides. In contrast, the platinum group element mineralogy of the top reef, and the small amount of data from the intrareef pyroxenite, mainly consist of Pt-affiliated platinum group elements-Bi-tellurides. The Pt-sulfides are mainly equant, relatively coarse crystals (many grains between 50 to 100 μm2 area), contrasting with the Pt-affiliated platinum group elements-Sb-As and -Bi-Te minerals that tend be high aspect-ratio grains, occurring in veinlets or as rims on earlier-forming platinum group element phases. These Te-As-Bi-Sb compounds are closely associated with chlorite, actinolite, quartz, and chalcopyrite, consistent with secondary deposition at lower temperatures and association with aqueous fluids. A model is proposed involving the emplacement of the Merensky unit as a magma pulse into at least semi-crystallized host rock, followed by aqueous fluid saturation and local migration, combined with concentration of late magmatic fluids around the top and bottom contacts of the magma pulse. Late remobilization of Pt-affiliated platinum group elements from the zones immediately (centimeter-scale) above the top reef, and from the underlying meter or two of pyroxenite, and from the centimeters underlying the bottom reef, have added additional platinum group elements to the reefs as late platinum group elements-Te-As-Bi-Sb minerals, independent of whether or not chromite is present in the reef initially.

Variations in Composition, Texture, and Platinum Group Element Mineralization in the Lower Group and Middle Group Chromitites of the Northwestern Bushveld Complex, South Africa

2019 ◽  
Vol 114 (3) ◽  
pp. 569-590 ◽  
Author(s):  
Felix E.D. Kaufmann ◽  
Marie C. Hoffmann ◽  
Kai Bachmann ◽  
Ilya V. Veksler ◽  
Robert B. Trumbull ◽  
...  
Keyword(s):  
South Africa ◽  
Platinum Group Element ◽  
Bushveld Complex ◽  
Group Element ◽  
Middle Group ◽  
Platinum Group ◽  
Lower Group

Sulfide mineral chemistry and platinum-group minerals of the UG-2 chromitite in the northern limb of the Bushveld Igneous Complex, South Africa

2021 ◽  
Vol 59 (6) ◽  
pp. 1339-1362
Author(s):  
Malose M. Langa ◽  
Pedro J. Jugo ◽  
Matthew I. Leybourne ◽  
Danie F. Grobler
Keyword(s):  
Platinum Group Element ◽  
Mineral Chemistry ◽  
Sulfide Mineral ◽  
Sulfide Minerals ◽  
Group Element ◽  
Igneous Complex ◽  
Northern Limb ◽  
Platinum Group Minerals ◽  
Platinum Group ◽  
Bushveld Igneous Complex

ABSTRACT The UG-2 chromitite layer, with its elevated platinum-group element content, is a key marker horizon in the eastern and western limbs of the Bushveld Igneous Complex and the largest platinum-group element chromite-hosted resource of its kind in the world. In contrast, much less is known about its stratigraphic equivalent in the northern limb, the “UG-2 equivalent” (UG-2E) chromitite. Recent studies on chromite mineral chemistry show similarities between the UG-2 and sections of the UG-2E, but also that the UG-2E was partially contaminated by assimilation of local metasedimentary rocks. Here, we provide a detailed characterization of sulfide minerals and platinum-group minerals in a suite of samples from the UG-2E and compare the results with data obtained from a reference suite of samples from the UG-2. Results from petrographic observations, electron probe microanalysis, laser ablation-inductively coupled plasma-mass spectrometry, quantitative evaluation of materials by scanning electron microscopy, and δ34S isotopes show that: (1) sulfide minerals in the UG-2E and UG-2 consist mainly of pentlandite-chalcopyrite-pyrrhotite, but pyrrhotite is significantly more abundant in the UG-2E and almost absent in the UG-2; (2) iron contents in pentlandite from the UG-2E are significantly higher than in the UG-2; (3) platinum-group element contents within sulfide minerals are different between the two chromitites; (4) UG-2E platinum-group minerals are dominated by arsenides and bismuthotellurides, and by alloys and platinum-group element-sulfide minerals in the UG-2; (5) sulfide mineral chemistry and δ34S values indicate some crustal contamination of the UG-2E; and (6) sulfide mineral and secondary silicate mineral textures in both the UG-2E and UG-2 are indicative of minor, millimeter- to centimeter-scale, hydrothermal alteration. From our observations and results, we consider the UG-2E chromitite in the northern limb to be the equivalent to the UG-2 in the eastern and western limbs that has been contaminated by assimilation of Transvaal Supergroup footwall rocks during emplacement. The contamination resulted in UG-2E sulfide mineral elemental contents and platinum-group mineral types and abundances that are distinct from those of the UG-2 in the rest of the Bushveld.

Contrasting platinum-group element concentration patterns in cumulates of the Bushveld complex

1989 ◽  
Vol 24 (3) ◽  
pp. 219-229 ◽  
Author(s):  
G. von Gruenewaldt ◽  
L. J. Hulbert ◽  
A. J. Naldrett
Keyword(s):  
Platinum Group Element ◽  
Element Concentration ◽  
Bushveld Complex ◽  
Group Element ◽  
Platinum Group ◽  
Concentration Patterns

Selenium and sulfur concentrations in the Bushveld Complex of South Africa and implications for formation of the platinum-group element deposits

2009 ◽  
Vol 44 (6) ◽  
pp. 647-663 ◽  
Author(s):  
Sarah-Jane Barnes ◽  
Dany Savard ◽  
L. Paul Bédard ◽  
Wolfgang D. Maier
Keyword(s):  
South Africa ◽  
Platinum Group Element ◽  
Bushveld Complex ◽  
Group Element ◽  
Platinum Group

scholarly journals A record of assimilation preserved by exotic minerals in the lowermost platinum-group element deposit of the Bushveld Complex: The Volspruit Sulphide Zone

Lithos ◽  
2019 ◽  
Vol 324-325 ◽  
pp. 584-608 ◽  
Author(s):  
Dominique Tanner ◽  
Iain McDonald ◽  
R.E. Jock Harmer ◽  
Duncan D. Muir ◽  
Hannah S.R. Hughes
Keyword(s):  
Platinum Group Element ◽  
Bushveld Complex ◽  
Group Element ◽  
Platinum Group

Platinum-group element-chromitite associations in the Bushveld Complex

1986 ◽  
Vol 81 (5) ◽  
pp. 1067-1079 ◽  
Author(s):  
Gerhard Von Gruenewaldt ◽  
C. J. Hatton ◽  
R. K. W. Merkle
Keyword(s):  
Platinum Group Element ◽  
Bushveld Complex ◽  
Group Element ◽  
Platinum Group
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