Correlation between chromite composition and PGE mineralization in the Critical Zone of the western Bushveld Complex |
| |
Authors: | B. Teigler H. V. Eales |
| |
Affiliation: | (1) Department of Geology, Rhodes University, 6140 Grahamstown, South Africa;(2) Present address: Rio Tinto Namibia (Pvt) Ltd., P.O. Box 1079, Windhoek, Namibia |
| |
Abstract: | Detailed mineralogical investigations of chromite in the Lower and Critical Zones in the northwestern sector of the Bushveld Complex have revealed significant compositional variations with regard to modal proportions, host-rock lithology, and stratigraphic height. Superimposed on these variations are long-range systematic trends in the composition of chromite in the massive layers. These long-range trends are closely linked with the evolution of the silicate cumulates. The massive chromitite layers are divided into two types. Type 1 comprises the chromitites hosted entirely within ultramafic cumulates, while Type 2 chromitites are within cyclic units in which plagioclase cumulates occur. The types are also distinguishable by their respective contents of platinum-group elements (PGEs) and distribution patterns thereof, viz. the ratios between Ru + Os + Ir and Pt + Pd + Rh, or relative element proportions, both of which display a systematic change with height in accordance with chromite composition. The relation between silicate geochemistry, chromite composition, and PGE tenor, leads to the development of a model explaining the formation of PGE-mineralized, sulphide-poor chromitite layers in the Critical Zone of the Bushveld Complex. Presented at the International Conference for Applied Mineralogy, Pretoria, September 1991 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|