A century of ongoing silicic volcanism at Cordón Caulle, Chile: New constraints on the magmatic system involved in the 1921–1922, 1960 and 2011–2012 eruptions

SEROPIAN, GILLES; SCHIPPER, C. IAN; HARMON, LYDIA J.; SMITHIES, SARAH L.; KENNEDY, BEN M.; CASTRO, JONATHAN M.; ALLOWAY, BRENT V.; FORTE, PABLO

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

ELSEVIER SCIENCE BV

Año: 2021 vol. 420

0377-0273

Cordón Caulle in southern Chile has produced three dacitic to rhyolitic fissure eruptions over the past century (in 1921-1922, 1960 and 2011-2012), and thereby provides an ideal opportunity to examine the architecture of its underlying silicic system. While the 2011-2012 eruption has been extensively studied, comparatively little is known about the 1921-1922 and 1960 events. Major-element matrix glass analyses from the 1960 products (71.5 wt.% SiO2) are indistinguishable from the 2011-2012 data (72.2 wt.% SiO2), but the 1921-1922 analyses form a discrete, slightly less evolved sub-population (69.0 wt.% SiO2). We utilise rhyolite-MELTS geobarometry to estimate both the storage and extraction depths of all three magmas. For all three eruptions, magma was stored in the shallow crust, between 80-150 MPa (3.5-6.6 km). The 2011-2012 magma body spanned this whole depth range but the 1921-1922 and 1960 magma bodies were more confined in pressure, at 90-112 MPa (4.0-5.0 km) and 123-143 MPa (5.4-6.3 km) respectively. Melt extraction from a parental crystal-mush occurred in the range 70-200 MPa (3.1-9.0 km) for all three eruptions, suggesting contiguous melt segregation and storage in the shallow crust. Finally, we discuss whether the deeper magma storage in 1960 reflects the influence of a seismic trigger by events associated with the Mw9.5 Great Chilean earthquake.