Role of magmatic and fluid concentrating in formation of platinum mineralization in the Lower Zone and Platreef as follows from composition of phlogopite, cumulus silicates, and sulfide melt, the northern limb of Bushveld Complex
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- 作者：M. A. Yudovskaya (1) (2)
J. A. Kinnaird (2)
L. V. Udachina (1)
V. V. Distler (1)
D. V. Kuz鈥檓in (3) (4)
1. Institute of Geology of Ore Deposits ; Petrography ; Mineralogy ; and Geochemistry ; Russian Academy of Sciences ; Staromonetnyi per. 35 ; Moscow ; 119017 ; Russia
2. School of Geosciences ; University of the Witwatersrand ; 2050 Wits ; Johannesburg ; South Africa
3. Sobolev Institute of Geology and Mineralogy ; Siberian Branch ; Russian Academy of Sciences ; pr. Akademika Koptyuga 3 ; Novosibirsk ; 630090 ; Russia
4. Novosibirsk State University ; ul. Pirogova 2 ; Novosibirsk ; 630090 ; Russia - 刊名：Geology of Ore Deposits
- 出版年：2014
- 出版时间：November 2014
- 年：2014
- 卷：56
- 期：6
- 页码：451-478
- 全文大小：5,223 KB
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- 出版者：Springer US
- ISSN：1555-6476
文摘
As follows from the results of new geological exploration, the thick sequence of primitive cumulates of the Lower Zone underlies Platreef in separate magmatic depressions of the northern limb of the Bushveld Complex. In the Turfspruit area, the Lower Zone is separated from the overlying Platreef by an interval of contact metasedimentary rocks with sills of fine-grained norite and plagioclase orthopyroxenite of the Marginal Zone. The magmatic stratigraphy of Platreef in Turfspruit and its western plunge, where it is slightly contaminated with sedimentary rocks, is close to the section of Critical Zone in the Bushveld. The Lower Zone and Platreef contain sulfide mineralization enriched in PGE in particular units-reefs-throughout the section. The main reef can be correlated with the Merensky Reef. The objective of this study was to estimate the relationships between fluid and magmatic PGE concentrating in the reefs localized in the upper part of Platreef near its unconformable contact with the Main Zone. It is shown that Ni partitioning between cumulus olivine and orthopyroxene, on the one hand, and coexisting sulfide liquid, on the other, indicates their equilibrium crystallization in the Lower Zone and Platreef at close redox conditions. The composition of sulfide liquid was recalculated as sulfide tenor on the basis of bulk Ni, Cu, and S concentrations in rock. In contrast, Ni partitioning between phlogopite and sulfide melt does not provide evidence in favor of their equilibrium crystallization, although Mg # of phlogopite from the intercumulus assemblage is correlated with Mg # of cumulus mineral throughout the section. The results of phlogopite microprobing throughout the section show that the highest F and Cl contents are characteristic of highly evolved rocks, including both the PGE-bearing plagioclase pyroxenite from reefs and barren norite from the Marginal Zone. We have arrived at the conclusion that enrichment in volatile components is the attendant rather than necessary condition of PGE mineralization formation in reefs, whereas the partitioning of metals between silicate and sulfide melts is the main ore-controlling factor.