Unravelling the thermal state of the southern Central Andes and its controlling factors

RODRIGUEZ PICEDA, CONSTANZA; SCHECK WENDEROTH, MAGDALENA; BOTT, JUDITH; GÓMEZ DACAL, MARÍA LAURA; PONS, MICHAËL; PREZZI, CLAUDIA BEATRIZ; STRECKER, MANFRED R.

Congreso; EGU General Assembly 2021; 2021

The Andes represent the modern type area for orogeny at a non-collisional, ocean-continentconvergent margin. Subduction geometry, tectonic deformation, and seismicity at this plateboundary are closely related to lithospheric temperature distribution in the upper plate. Despiterecent advances in the assessment of the thermal state of the Andean lithosphere and adjacentregions derived from geophysical and geochemical studies, several unknowns remain concerningthe 3D temperature configuration at lithospheric scale. In particular, it is not clear how both, theconfiguration of the continental overriding plate (i.e., its thickness and composition) and thevariations of the subduction angle of the oceanic Nazca plate influence thermal processes anddeformation in the upper plate. To address this issue, we focus on the southern segment of theCentral Andes (SCA, 29°S-39°S), where the Nazca plate changes its subduction angle between 33°Sand 35°S from the Chilean-Pampean flat-slab zone (< 5° dip, 27-33°S) in the north to a steepersector south of 33°S (~30° dip). Additionally, the overriding plate exhibits variations in the crustalgeometry and density distribution along- and across-strike of the subduction zone. We derived the3D lithospheric temperature distribution and the surface heat flow of the SCA from the inversionof S-wave velocity to temperatures and calculations of the steady-state conductive thermal field.The configuration of the region ? concerning both, the heterogeneity of the lithosphere and theslab dip ? was accounted for by incorporating a 3D data-constrained structural and density modelof the SCA into the workflow. We conclude that the generated thermal model allows us to evaluatehow mantle thermal anomalies and first-order structural and lithological heterogeneities in thelithosphere, observed across and along-strike of Andean orogen, affect the thermal field of theSCA and thus the propensity of the South American lithosphere to specific styles in deformation. Inaddition, our results are useful to constrain thermo-mechanical simulations in geodynamicmodelling and therefore, contribute to a better understanding of the present-day rheological stateof the Andes and adjacent regions.