Topographic constraints on magma accumulation below the actively uplifting Uturuncu and Lazufre volcanic centers in the Central Andes

Abstract

Geodetic surveys of Volcan Uturuncu and the Lazufre volcanic complex in the Central Andes of South America reveal sustained surface uplift from magmatic intrusion at depth. However, the decadal timescales of geodetic surveys are short relative to the timescales of magma chamber growth. Thus, from ­geodesy alone, it is difficult to infer the deformation and hence magma accumulation history of these volcanoes. Here we combine data from InSAR, long-wavelength topography, GPS and high-resolution topographic surveys of lake shorelines and rivers, and lava flow morphology to constrain the spatial and temporal evolution of magmatism at Uturuncu and Lazufre. Near Uturuncu, dated lake shorelines show no evidence of tilting since ca. 16 ka, and we find no evidence of deformation in the long-wavelength topography. A lack of net surface displacement suggests that uplift related to a rising diapir must be less than a century old, or, more likely, magmatic inflation at Uturuncu is transient over millennial timescales and is therefore not recorded in the topog­raphy. At Lazufre, we also find no evidence for sustained uplift recorded in Late Pleistocene lake shorelines. However, the orientations of multiple dated lava flows suggest that the long-wavelength dome at the center of Lazufre’s uplift has persisted since at least 400 ka. Additionally, we find that the radial distribution of volcanic vents at Lazufre, coupled with the presence of an apical graben, is consistent with experimental and theoretical predictions of magmatic doming. The dome’s longevity indicates significant magma storage at depth, and therefore Lazufre is likely a highly evolved pre-caldera magmatic system. These two case studies demonstrate that combining geomorphic and geophysical data sets to extend the geodetic record back in time can help determine the style and magnitude of magma transport in volcanic systems.