San José de Guaviare Syenite, Colombia: Repeated Ediacaran intrusions in the northwestern Amazonian Craton

• Published in: Boletín geológico - Ingeominas Vol. 48; no. 1; pp. 49 - 79
• Main Authors: Amaya López, Carolina, Weber Scharff, Marion, Ibáñez Mejía, Mauricio, Cuadros Jiménez, Federico Alberto, Restrepo Álvarez, Jorge Julián, Botelho, Nilson Francisquini, Maya Sánchez, Mario, Pérez Parra, Orlando Manuel, Ramírez Cárdenas, Carlos
• Format: Journal Article
• Language: English
• Published: Servicio Geológico Colombiano 12.07.2021
• Subjects: Geochemistry; Geochronology; Intraplate; Neoproterozoic; Nepheline Syenite
• ISSN: 0120-1425; 2711-1318
• DOI: 10.32685/0120-1425/bol.geol.48.1.2021.503

The Neoproterozoic igneous rocks found in the municipality of San José del Guaviare include several isolated plutonic bodies that protrude from the Phanerozoic sedimentary cover in belts aligned NW-SE. Limited to the Guaviare department, these intrusions stretch from the La Lindosa mountain range to the corregimiento El Capricho. These plutonic bodies consist of nepheline syeni­tes, nepheline monzosyenites, nepheline-bearing alkali-feldspar syenites, syenites, quartz-syenites, quartz-alkali-feldspar syenites, syenogranites, and quartz-rich granitoids, which have been grouped and termed the San José del Guaviare Syenite unit (SJGS). The intrusion of the unit occurred in the Ediacaran (604 ± 7 Ma and 620.5 ± 7.5 Ma) by mantle-derived alkaline magmas formed in anorogenic settings, most likely in rift-like stretching zones. The silica-subsaturated magma may have reacted with host rocks at the crust level, producing some silica-saturated igneous rocks, such as syenogranites and quartz-syenites, which are found in the El Capricho and Cerritos bodies.