Multi-vent construction and eruptive-style transitions in the Bouteguerrouine Volcanic Complex (Middle Atlas, Morocco)

Abstract

Multi-vent volcanic complexes in intraplate monogenetic volcanic fields provide key records of how karstification processes, evolving magma ascent pathways and inherited crustal discontinuities shape volcanic landforms. Located in the Middle Atlas Volcanic Field (MAVF) of Morocco, the Bouteguerrouine Volcanic Complex (BVC) is a coalescent system (~4 × 5 km) emplaced on a Liassic carbonate substratum and comprising 8 craters that include both phreatomagmatic and strombolian vents.We combine field mapping and tephrostratigraphic logging with 0.5 m-resolution DEM morphometry and microstructural observations to link eruptive-style transitions to vent architecture and to evaluate the role of inherited structural trends of Middle Atlas chain in organizing vent migration.Field analysis revealed evidence of polyphase evolution, marked by (i) an early hydromagmatic stage expressed by maar/tuff-ring deposits, including lithic-rich basal breccias and bedsets consistent with surge emplacement (locally preserved as discontinuous tuff-ring remnants and peperites), followed by (ii) a dominant strombolian phase constructed scoria and spatter cones and produced lava flows that either buried or locally truncated the underlying hydromagmatic deposits. These cross-cutting relationships provide a relative chronology markers documenting vent re-use, vent migration and progressive edifice coalescence.DEM-derived metrics (crater elongation and breach azimuths, cone height and flank slopes) quantify vent geometry and migration patterns; Comparing our results with the Middle Atlas chain's inherited structural trends reveals the role of Quaternary tectonic evolution in guiding magma ascent pathways at the complex scale. In addition, microstructural observations indicate open-system magma evolution (zoned olivine and clinopyroxene, and disequilibrium reaction textures involving xenocrysts/xenoliths). These features are consistent with transient recharge and mixing during magma ascent and with variable vent dynamics.Overall, the BVC provides a testable framework linking eruptive transitions, multi-vent growth and landform development, emphasizing coupled volcanotectonic and geomorphological controls in the Middle Atlas MAVF.