Monogenetic volcanism in subduction settings: comparative statistical study of the Sierra Chichinautzin and Los Tuxtlas Volcanic Fields in Mexico

Abstract

Monogenetic fields present significant diversity, yet this diversity has not been fully quantified, and its origin remains elusive. We studied two large subduction-related fields in Mexico, the Sierra Chichinautzin and Los Tuxtlas, that have distinct crustal stress regime and structures, magma compositions, vent types, and climatic conditions. Using recently available 5-m resolution topographical data, we located all the eruptive centers, studied their spatial distribution and analyzed scoria cone shapes in detail, calculating morphometric parameters for the best preserved. We then applied a set of statistical tools to analyze and compare the patterns of vent distribution, vent alignment, and diversity in cone shapes in these two fields. We observe that, despite their distinct setting, the two fields are similar in terms of vent distribution and cone morphology, which shows that this type of data cannot be used alone to infer the tectonic, magmatic, and climatic context of monogenetic fields. It also confirms previous results that the diversity in cone shapes (slope, height-to-diameter ratio) reflects processes that are common to all cones (e.g., ballistic emplacement followed by scoria avalanching on slopes), and hence do not vary significantly (at field-scale) with external parameters. Differences in the crustal stress regime had no apparent impact on vent distribution as the dikes followed active faults, irrespective of their motion. Climatic differences did not affect the shape variety of the studied cones probably because of their young ages (< 50,000 years old) and their location in a vegetated environment. The fields nevertheless differ in size and vent density, as well as scoria cone shape complexity and volume, which can be attributed to differences in the geometry of the magma source for its impact on the closeness of the dikes feeding the activity. Differences in the relative proportion of small cones in both fields are likely due to factors impacting eruptive style such as magma-water interaction, magma composition, and/or fissure lengths.