Fault Accommodated Magmatic Localization Beneath Laguna del Maule

Keranen, Katie

Fault Accommodated Magmatic Localization Beneath Laguna del Maule

Monday, 8 January 2018: 16:25

Salon Quinamavida (Hotel Quinamavida)

Katie M Keranen¹, Dana E Peterson², Luis Lara³, Craig Miller⁴, Nicolas Garibaldi⁵, Basil Tikoff⁶, Glyn Williams-Jones⁴ and Andres Tassara⁷, (1)Cornell University, Earth and Atmospheric Sciences, Ithaca, NY, United States, (2)Cornell University, Ithaca, NY, United States, (3)SERNAGEOMIN National Geology and Mining Service, Santiago, Chile, (4)Simon Fraser University, Burnaby, BC, Canada, (5)University of Wisconsin Madison, Madison, WI, United States, (6)University of Wisconsin Madison, Geoscience, Madison, WI, United States, (7)University of Concepcion, Concepcion, Chile

Abstract:

Rapid uplift of >20 cm/yr occurs in a focused zone within the Laguna del Maule volcanic field (LdM) in the Southern Andes of Chile. Active faults cut through the lake near the center of uplift. However, interactions between these faults and the magmatic system are not well understood. Here we use CHIRP and magnetic data acquired within LdM, with complementary fault mapping on land, to map active fault structures above and near the focused uplift. Within the lake we image surface-cutting, NE-trending normal faults, forming a ~5 km wide graben beneath the lake. Sediment fills the graben in distinct growth packages. Above the center of uplift, sedimentary units are domed, and cut sharply by faults that appear to accommodate the uplift in a “trapdoor” style of faulting. We interpret that the NE-trending extensional graben beneath the lake represents a transtensional step-over within the broader regional fault system, within which magma has localized in the shallow crust. Individual faults delineated by magnetic anomalies may serve as conduits for magma migration to the surface.