Alteration/diagenesis studies

Exploration criteria and tools are developed through the characterisation of alteration footprints of mineral system types to assist with area and target selection.

In the example below, whole-rock geochemistry results are plotted to discriminate diagenetic from hydrothermal trends and determine relative proximity to mineralization:

^{Alteration box plot (Large et al, 2001), applied to Iberian Pyrite Belt volcanic rocks related to VMS mineralization (Oliveira et al, 2013).}

Sandstone petrography, including thin section petrography, scanning electron microscopy of thin sections and rock chips, is compared with sandstone porosity and permeability in order to understand the effect and timing of sandstone diagenesis.

Sandstone alterations associated with intrusions and/or faults are equally important since they may affect the reservoir properties, but may also provide important information about the activity of hydrothermal fluids. Alteration of heavy minerals has been applied to understand the redox conditions during sandstone diagenesis.