Open File Report 25
Electron microprobe studies of minerals from weathered profiles,
Parkinson Pit and environs, Mt Magnet, WA
Major and trace element data for more than 100 minerals from 24
separate samples reveal the host minerals for specific elements
during weathering processes at Mt Magnet.
Resistant minerals like rutile, spinel, tourmaline and mica retain
their component elements through the weathering profile with a low
Fe* (i.e. Fe/(Fe + Mg + Mn) ratio for muscovite and tourmaline indicating
proximity to mineralisation. Gold and talc are not so resistant
to weathering, with gold losing its Ag content during weathering
processes at Mt Magnet. Sulphides, chlorite, feldspars and carbonates
are readily destroyed during weathering with their component elements
either incorporated into Fe and Mn oxides, kaolinite and smectitic
clay or lost to the profile by dispersal by groundwaters. The Fe
oxides are particularly important hosts for Au-pathfinder elements
(e.g. As, Sb and W). Chlorite, carbonate and sulphide compositions
may reflect proximity to mineralisation and be useful in deep profiles
but because of their susceptibility to weathering they are not as
versatile as mica or tourmaline.
The Cr contents of each of chlorite, muscovite, rutile and perhaps
spinel, indicate the lithology of their host samples by showing
decreasing Cr contents from ultramafic to mafic to felsic rocks.
Last updated: Tuesday, January 04, 2000 03:23 PM