GLACIOVOLCANISM AT VOLCÁN QUETRUPILLÁN, CHILE

Volcán Quetrupillán is flanked by Volcán Villarrica and Volcán Lanín, and these three volcanoes form a chain oriented obliquely to the major N-S structure tectono-volcanic structure in this part of Chile - the Liquiñe-Ofqui Fault Zone (LOFZ).

During stratocone construction the products of earlier eruptions are often buried and/or destroyed by later eruptions, which is exemplified by the prominent stratocones of Villarrica and Lanín. Although Quetrupillán has also constructed a small Holocene stratocone, its closer proximity to the LOFZ has resulted in a more dispersed (fault-controlled) volcanic field, particularly around its southern flanks where the products of Holocene and Pleistocene fissure eruptions (dacite with minor basaltic andesite – Pavel et al., 2004) are well preserved. Fourteen lava-ice edifices of assumed varying ages are exposed here, and provide an opportunity to study longer term volcano-ice interactions at this volcano.

Lava-ice interactions at Quetrupillán include: ridges formed above erupting fissures, ridge-forming lavas with prominent flanking buttresses; and irregular sheet-like bodies with sinuous (esker-like) and lobate termini. One source of the latter reveals agglutinate mounds from which clastogenic lava sheets flowed beneath relatively thin ice and then plunged into an ice-filled trough to its base. This example illustrates how careful study of lava-ice interactions can reveal important palaeoenvironmental information.

Future work will include Ar-Ar dating and petrological characterisation of the lava-ice edifices to provide a timeline illustrating the development of volcanic field and its relation to ice thicknesses, as well activity on the Liquiñe-Ofqui Fault Zone through time.

Reference

Pavez, A., Lara, LE., Naranjo, JA., and Moreno, H. (2004). Quetrupillán Volcano (Southern Andes, Chile): Holocene explosive activity and morphostructural evolution. Poster presentation at IAVCEI 2004 General Assembly, Pucon, Chile.