Proc. IODP, 331, Methods

Table T2. Diagnostic features of alteration styles defined during Expedition 331.


Style of alteration	Diagnostic features
Oxidation	Affects near-surface rocks, resulting in a brownish to yellow coloration of fine sediments and localized orange to dark brown iron staining of larger clasts.
Glauconitic	Greenish staining of near-surface sediments. Note that the presence of glauconite was not confirmed by XRD.
Native sulfur	Significant yellow native sulfur present.
Kaolinite-muscovite	Hydrothermal alteration, resulting in pale gray clay. Kaolinite and/or muscovite identified by XRD.
Illite/Montmorillonite	Hydrothermal alteration, resulting in pale gray clay. Illite and/or montmorillonite identified by XRD.
Mg chlorite	Hydrothermal alteration, resulting in pale gray clay, which may have a distinct greenish or bluish tinge. Mg chlorite identified by XRD.
Quartz–Mg chlorite	Hard crystalline rocks with quartz veining and greenish clay alteration. Quartz and Mg chlorite identified by XRD.
Quartz-muscovite/illite	Hard crystalline rocks with intense silicification and a gray color. Quartz and muscovite/illite identified by XRD. Only seen at Site C0016.

XRD = X-ray diffraction.