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Understanding the Ecuadorian Rhyolite Province: A Petrochronologic Investigation of a Rhyolitic Flare-up in the Northern Andes of Ecuador

Marykathryn Campos1, Shanaka deSilva1, Patricia Mothes2

  • Affiliations: 1College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR; 2Instituto Geofísico, Escuela Politecnica Nacional, Quito, Ecuador

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 284

  • Programme No: 1.3.25

  • Theme 1 > Session 3

Abstract

Rhyolitic volcanism produces Earth's largest explosive eruptions and poses significant geohazards. The Ecuadorian Rhyolite Province (ERP), spanning 130 km from the Chacana caldera complex to Pisayambo, includes Chalupas and Cotopaxi Calderas. Located in the eastern cordillera, within an active andesitic volcanic belt in the Ecuadorian Andes, 25-50 km south and east of Quito, ERP rhyolitic volcanism initiated ~3.0 Ma. A flare-up occurred ~200 ka, producing the 200 km3 Chalupas pumice flow and coeval rhyolitic flows. Subsequent events included rhyolitic lava flows and pumice lapilli fallout (100 km3) in the northern Chacana Caldera and more recent eruptions at Cotopaxi (7 events between 9.6 and 2.3 ka), Conda (11.8 ka), and Aliso (<2 ka). This history of explosive activity highlights the need to understand better the ERP's magmatic evolution and implications for assessing future eruption risks to Quito and nearby areas. We are investigating the spatial and genetic relationships among volcanic centers to test the hypothesis that ERP rhyolites originate from a single magmatic system. Available whole-rock geochemistry and petrologic data are ambiguous but could support this hypothesis. To better address the hypothesis, we are conducting petrochronology (U-Pb, trace element, and O-isotope) analyses of zircons to track magmatic evolution and origin. Preliminary data suggests a significant overlap in zircon ages and chemistry across ERP rhyolites, connoting shared magmatic processes and a common source. Findings from this investigation will enhance the understanding of silicic magmatic systems in the northern Andes with implications for volcanic hazard assessment in the Quito region.