Propylitic alteration is the chemical alteration of a rock, caused by iron and magnesium bearing hydrothermal fluids, altering biotite or amphibole within the rock groundmass. It typically results in epidote–chlorite–albite alteration and veining or fracture filling with the mineral assemblage along with pyrite.

What is hydrothermal alteration in geology?

Hydrothermal alteration is defined as any alteration of rocks or minerals by the reaction of hydrothermal fluid with preexisting solid phases.

How does hydrothermal alteration occur?

Hydrothermal alteration is a complex process involving mineralogical, chemical and textural changes, resulting from the interaction of hot aqueous fluids with the rocks through which they circulate, under evolving physicochemical conditions.