Mechanisms of platinum-group element fractionation in ultramafic melts and implications for the exploration for magmatic nickel sulphide deposits ...

• Main Author: Locmelis, Marek
• Format: Text
• Language: unknown
• Published: Macquarie University 2022
• Subjects: Other education not elsewhere classified; Karasjok
• Online Access: https://dx.doi.org/10.25949/19438271; https://figshare.mq.edu.au/articles/thesis/Mechanisms_of_platinum-group_element_fractionation_in_ultramafic_melts_and_implications_for_the_exploration_for_magmatic_nickel_sulphide_deposits/19438271

Platinum-group elements (PGE) are important as petrogenetic tracers, but owing to their low abundances and complex behaviour they are among the least understood elements in geochemistry. This study investigates the mechanisms of PGE fractionation in ultramafic systems (komatiites, komatiitic basalts, ferro-picrites) and focuses on the role of chromite. Samples from a range of occurrences have been analysed to assess potential controls on PGE behaviour, such as geochemical affinities (Munro-type and Karasjok-type), age (2.0 and 2.7 Ga), emplacement styles, metamorphic grade and nickel-sulphide mineralisation endowment and style. -- Data obtained by in-situ laser ablation ICP-MS analysis provide the first direct evidence that Ru can exist in solid solution in chromite with concentrations up to several hundred ppb. The data show that the behaviour of Ru is dominantly controlled by the sulphide-saturation state. In systems that did not equilibrate with a sulphide liquid, chromites have distinctly higher Ru ...