23-8 Neogene-Quaternary ignimbrite flare-ups in the Central and Northern Andes: differences and the tectonic considerations.

Session: Subduction Zones and Their Volcanic Arcs: Initiation and Evolution, Structure, Metamorphism, Magmatism (Posters)

Poster Booth No.: 22

Presenting Author:

Juan Jaramillo-Ríos

Authors:

Jaramillo-Ríos, Juan Sebastian¹, Cardona, Agustin², Zapata, Sebastián³, Valencia, Victor⁴, Torró, Lisard⁵

(1) Especialidad de Ingeniería Geológica, Departamento Académico de Ingeniería, Pontificia Universidad Católica del Perú, Lima, (None), Peru, (2) Departamento de Procesos y Energía, Facultad de Minas, Universidad Nacional de Colombia, Medellin, Colombia, (3) Faculty of Natural Sciences, Universidad del Rosario, Bogotá, Colombia, (4) School of the Environment, Washington State University, Pullman, Washington, USA, (5) Especialidad de Ingeniería Geológica, Departamento Académico de Ingeniería, Pontificia Universidad Católica del Perú, Lima, Peru,

Abstract:

The Andes are commonly divided into three main segments and, during the Late Cenozoic, have experienced contrasting high-flux volcanic episodes dominated by ignimbrite volcanism. These voluminous magmatic events are commonly explained by two end-member petrogenetic models: (1) partial melting of the continental crust followed by fractional crystallization, and (2) assimilation and fractional crystallization of mantle-derived magmas. A fundamental distinction between Central and Northern Andean ignimbrites lies in their isotopic signatures, with Central Andean ignimbrites characterized by εNd–εHf < 0 and ⁸⁷Sr/⁸⁶Sr > 0.7045.

In the Central Andes, Upper Cenozoic ignimbrite provinces, commonly exceeding 100 km³ in volume, have been linked to changes in subduction dynamics, subduction of topographic anomalies, and lithospheric delamination. These processes provided sufficient thermal input to partially melt a thick, hydrated sialic crust, resulting in magmas dominated by crustal signatures. In contrast, Upper Cenozoic ignimbrites in the Northern Andes commonly have <150 km³ and have traditionally been interpreted as mantle-derived magmas that formed in a relatively thin continental crust (<50 km).

New geochronological, geochemical, and isotopic data from Colombia indicate that, despite continental crustal thicknesses of ~60 km, crustal assimilation played a subordinate role in the genesis of Upper Cenozoic ignimbrites, contributing less than 12% to the total magmatic budget. This behavior contrasts sharply with the Central Andes, where ignimbrite magmatism is dominated by extensive crustal melting, accounting for ~50–65% of magma generation. These differences point to fundamentally distinct mechanisms for producing high-flux silicic volcanism along the Andean margin. In the Central Andes, ignimbrite formation is largely controlled by long magma residence times within thick, thermally mature crustal reservoirs, whereas in the Northern Andes, ignimbrite genesis is governed by short magma residence times facilitated by lithospheric-scale fault systems that promote rapid magma ascent and limit crustal interaction.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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