The Gabal (G) Katherina complex in the southern Sinai of Egypt (Being a part of the Arabian-
Shield) consisting mainly of volcanic arc granitoids, epiclastics and pyroclastic volcanic rocks (Rutiq
volcanics), followed latterly by the emplacement of high-level intrusions (Katherina ring dyke) and
calc-alkaline to slightly alkaline granites. The later-phase intrusions into the country rocks produced
deferent degrees of contact aureole with significant alteration effects especially on the early-formed
intermediate pyroclastics with their amygdules lava flows producing different degrees of zeolitization
in the pyroclastic rocks, were investigated using Optical Microscopy, Scanning Electron Microscopy
(SEM), X-ray diffraction (XRD) and wet chemical analyses. The studied volcanic rocks fall
considerably in the basaltic andesite and rhyodacite- dacite fields and show subcalc- alkaline to calcalkaline
affinities. On the other hand, the amygdaloidal volcanic rocks show low-temperature
hydrothermal alteration characterized by the abundance of chloritization. Geochemically; Hf, Ta, Sr, Y,
and Nb show slightly enrichment relative to the other zeolite-rich samples suggesting partial
releasing of immobile elements from the volcanic rock during the alteration processes. Furthermore,
zeolites found to fill the cavities in a non-uniform behavior. The subclass minerals such as phillipsite
and chabazite have been accompanied by palagonite clasts, smectite, and calcite. Zeolites also occur
in fibrous aggregates, partly or completely filling spheroid, ellipsoidal or irregular amygdules.