This study aims to inventory and quantify the scientific value of geological sites of Passo da Capela Alkaline Suite (PCAS) using the GEOSSIT platform, based on Brilha’s (2016) method. PCAS represents the only record of the last magmatic episode in Rio Grande do Sul state, Brazil, and highlights the rare alkaline magmatism. Despite its scientific relevance, Brazil lacks legislation to support geoconservation for sites with essentially scientific value, directing efforts and funding to geoparks. The study involved 40 occurrences documented in the literature, of which 26 were mapped and inventoried. The degradation risk due to anthropogenic activities, such as soybean cultivation and tree plantation, particularly threatening smaller outcrops, was also assessed. Several outcrops attributed to this suite are no longer accessible or have been severely degraded since their first description in the 1970s. PCAS is characterized by small magmatic bodies, the largest being necks up to 800 m in diameter, composed of phonolites (aphyric and porphyritic), basanite and trachyte. The exotic mineralogy includes garnet (melanite), pyroxenes (green) and feldspathoids (sodalite, hauyne, and nosean). Textures revealing crystallization evolution, interactions with xenoliths and cumulates from the crust and mantle characterize these rocks, providing insights into the reactivation of faults during the Mesozoic (76–99 Ma). This research proposes a geological itinerary, highlighting four of the five international and two of the 14 national geosites, as a route to understanding the magmatic history to be conserved along this “volcanic path”, reaffirming its scientific value.
