The volcanic rocks of the Chae Hom area in Lampang, northern Thailand were investigated. Petrographic and geochemical analyses were performed to comprehend the alterations. The volcanic rocks in this study were co-magmatic and chemically transitional rhyolite to trachyandesite with calc-alkalic affinity. Their colors were highly variable due to two main alteration processes that included silicification and sericitization. The silicification process yields abundant quartz, whereas the sericitization yields abundant sericite and clay minerals. The sericite and clay minerals are most likely to be illite. The silicafication process occurred after the sericitization process. Based on our petrochemical analysis, the Chae Hom volcanic rocks are considered to be of calc-alkaline affinity and post-collisional magmatic suite.
