Feature

band or ratio

Comments

Reference

Sericite/muscovite/illite/smectite

(5 + 7)/6

Phyllic alteration

Rowan (USGS); Hewson (CSIRO)

Alunite/kaolinite/pyrophyllite

(4 + 6)/5

Argillic altration

Rowan (USGS)

Carbonate/chlorite/epidote

(7 + 9)/8

Propylitic

Rowan