HR: 1340h
AN: V43A-1114    [Abstracts]
TI: Sulfide Minerals in the Bushveld Complex
AU: Kanitpanyacharo, W
EM: waruntorn.kanitpanyac haroen@duke.edu
AF: Duke University, Div. Earth and Ocean Sciences Nicholas School of the Environment, BOx 90227, Durham, NC 27514, United States
AU: Chutas, N
EM: nichutas@gmail.com
AF: Duke University, Div. Earth and Ocean Sciences Nicholas School of the Environment, BOx 90227, Durham, NC 27514, United States
AU: * Boudreau, A
EM: boudreau@duke.edu
AF: Duke University, Div. Earth and Ocean Sciences Nicholas School of the Environment, BOx 90227, Durham, NC 27514, United States
AB: Debate on the origin of the major platinum-group element (PGE) deposits of the Bushveld, Stillwater and other layered intrusions range from conventional magma mixing-sulfide saturation models in the resident magma chamber to those that suggest that the PGE and S may have been introduced by upward-percolating fluids moving through the solidifying crystal pile. This study looked at details of the petrographic associations and compositions of sulfides in the Bushveld Complex away from the ore zones to see if they can help elucidate degassing and vapor transport in that intrusion. In fresh assemblages where the silicate have not been altered to a variety of low temperature minerals, the sulfide assemblages are typically composed of chalcopyrite, pyrrhotite, pentlandite, pyrite and a variety of other trace phases that are locally important. Textural and modal abundance suggests these assemblages formed by unmixing from high temperature monosulfide phase(s) on cooling. Throughout much of the complex pyrrhotite + pyrite –bearing assemblages are the most common. However, in the Lower and Lower Critical zones pyrite is locally absent and pyrrhitite is associated with a Ti-free magnetite. The pyrrhotite in these oxides-bearing assemblages is characterized by lower S contents as compared with the pyrite-bearing assemblages. These observations imply that the oxide-bearing assemblages formed as the rock cooled along a lower fS₂/fO₂ path, and are consistent with S loss to degassing interstitial fluids in the rocks beneath the Merensky Reef.
DE: 1034 Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424)
DE: 1036 Magma chamber processes (3618)
DE: 3642 Intrusive structures and rocks
DE: 3643 Layered magma chambers
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting