Fluvial Placer Deposit (PGM)
Physical Process - Ground surface
Synonym
Alluvial placer deposit
Required Geological Setting
Neogene and Quaternary sediments
Occurrence
Fluvial placer deposits containing nuggets of platinum group metals (PGM), where heavy minerals such as chromite are selectively concentrated by water flows of rivers based on the difference of specific density. Nuggets are mainly composed of platinum, iridium, osmium, or alloys of these elements. The deposits may also produce gold. The PGM fluvial placer deposits are at downstreams of peridotite or altered serpentinite. The PGM fluvial placer deposits are formed on the riverbeds at a gently flowing stream in fissures of riverbed slabs or at upstreams of obstacles such as boulders in water.
Mineral Assemblages
Chromite, Platinum, Iridium, Osmium