Petrographic and Mineralogical Characterization of the Abitagua Batholith at the “Waysa Yacu and Jatun Yacu River” Geosite of the Napo Sumaco UNESCO Global Geopark in the Ecuadorian Amazon

The UNESCO Napo Sumaco Global Geopark comprises 19 geosites, including geosite nine, Waysa Yacu, and Jatun Yacu River, where the Abitagua batholith outcrops, which was formed in a Jurassic continental arc related to subduction processes (approximately 173 − 162 Ma ago). While some geosites have been the object of previous research, others, such as geosite nine, offer opportunities for more detailed scientific investigation. This study aimed to characterize the geodiversity of the geosite through an integrated analysis of field observations, petrographic analyses, and X-ray diffraction (XRD), with emphasis on the lithological, mineralogical, and structural diversity present in three outcrops, as well as to quantitatively assess the geosite’s geodiversity potential. Macroscopic and microscopic petrographic observations identified a coarse-grained monzogranitic main body, felsic and andesitic dikes, as well as mafic enclaves, together with minerals such as quartz, potassium feldspar (orthoclase), plagioclase (albite, labradorite, and bytownite), biotite, chlorite, and epidote, along with aphanitic, phaneritic, and porphyritic textures, myrmekitic microstructures, and evidence of hydrothermal alteration. The quantitative assessment indicated a high tourism potential, moderate scientific value and educational potential, and a low degradation risk. Overall, Waysa Yacu and Jatun Yacu River stands out for its lithological and mineralogical diversity, tectono-magmatic complexity, and good state of conservation, establishing itself as a reference site for geological studies and as a key resource for education and sustainable geotourism in the Ecuadorian Amazon.