Evaluation of crustal recycling and magma formation by subduction in the Trans Mexican Volcanic Belt: New insights from the Ceboruco volcano, Mexico

Overview

The Trans-Mexican Volcanic Belt (TMVB) is one of the most compositionally diverse magmatic arcs on Earth and therefore constitutes a prime location for testing emerging hypotheses on arc petrogenesis and continental evolution (Gómez-Tuena et al., 2018). Recycling of upper plate crust in subduction zones, or ‘subduction erosion’, is a major mechanism of crustal destruction at convergent margins. Assessing the impact of eroded crust on arc magmas is, however, difficult owing to the compositional similarity between the eroded crust, trench sediment and arc crustal basement that may all contribute to arc magma formation (Ferrari et al., 2011; Straub et al., 2015). Ceboruco volcano is one of a few active volcanoes in the western part of the TMVB and is compositionally diverse ranging from mafic to rhyolite magmas (Nelson, 1980; Nunez et al., 2022). It is known that Ceboruco produced three compositionally and volumetrically different magma types including two caldera-forming explosive eruptions. However, it remains unclear how these different magmas formed, what controls their composition including distinctively high-Nb magmas enriched in LILE and HFSE resembling those of enriched intraplate magmas. Volatile bearing minerals, common to other volcanoes within the TMVB, are rare at Ceboruco raising the question whether metasomatism can be held responsible for this enrichment?

This project will focus on a field-based analysis of the volcano and geochemical and petrographic study of samples collected from various domes and lavas in order to gain a better understanding leading to the formation of a range of volcanic products. The aim is to create a schematic model of the Ceboruco magma system and to see whether the basaltic to rhyolitic magmas originated from the same reservoir or whether complex processes involving partial melting of different source regions, fractional crystallisation and magma mixing and/or crustal erosion was responsible for the diverse magmatism at Ceboruco. In order to achieve this, whole rock and in-situ analyses of the mineral budget will be applied and compared to data from other subduction zone volcanoes to outline a potential magmatic system for Ceboruco. This combination provides a unique opportunity to track the eruption history of subduction-related volcanism and magma enrichment processes.

Figure 1: Simplified tectonic map of the north-eastward converging subduction zone showing the location of the Trans Mexican Volcanic Belt (TMVB) which is broadly divided into western, central and eastern regions. The location of several compositionally diverse volcanic centres, including Ceboruco, are indicated (after Frey et al., 2004; Gomez-Tuena et al., 2018).