Magnetite composition in Ni-Cu-PGE deposits worldwide: application to mineral exploration

To be useful as a tool for mineral exploration, primary and secondary magnetite should not have the same minor and trace element composition. Primary magnetite from all 13 major Ni-Cu deposits plot in the field for Ni-Cu sulfide deposits in the Ni + Cr vs. Si + Mg discrimination diagram. Secondary magnetite plot outside of the field for Ni-Cu deposits. Therefore using this diagram, we can discriminate between primary and secondary magnetite using the low Ni + Cr content of secondary magnetite. Magnetite is resistant to surficial weathering and destruction during mechanical transport, such that it is a useful indicator mineral in exploration that can be used to detect eroded Ni-Cu-PGE deposits in surficial sediments.