The Pantanillo Granulites and their implications into the cretaceous tectonic history of the Western Cordillera, Colombia

The Western Cordillera of Colombia preserves the remnants of the Cretaceous tectonic history of the northernmost Andes, including fragments of Ecuadorian-Colombian-Leeward Antilles Arc formed during the northeastward movement of the Caribbean plate. Although the granitoid rocks (such as the Santa Fe tonalite) that constitute the arc crust have been extensively studied, the mafic-ultramafic rocks hosted within the felsic facies, along with their textural variations and potential genetic relationships, remain less understood. This study focuses on the Pantanillo Granulites, analysing their mineral composition to determine their pressure and temperature conditions of formation through pseudosections. Our findings indicate that the Pantanillo granulite-facies rocks formed under pressures ranging from 0.87 to 1.12 GPa and temperatures between 940°C and 1050°C, corresponding to crustal depths of 20–30 km and a high geothermal gradient. Field and petrographic observations suggest that the Santa Fe batholith and the Pantanillo granulites are consanguineous, forming part of an appinite suite characterized by the common presence of large hornblende crystals.