Controls of the Lithospheric Thermal Field of an Ocean-Continent Subduction Zone: The Southern Central Andes

Abstract

In an ocean-continent subduction zone, the assessment of the lithospheric thermal state is essential to determine the controls of the deformation within the upper plate and the dip angle of the subducting lithosphere. In this study, we evaluate the degree of influence of both the configuration of the upper plate (i.e., thickness and composition of the rock units) and variations of the subduction angle on the lithospheric thermal field of the southern Central Andes (29°–39°S). Here, the subduction angle increases from subhorizontal (5°) north of 33°S to steep (~30°) in the south. We derived the 3D temperature and heat flow distribution of the lithosphere in the southern Central Andes considering conversion of S wave tomography to temperatures together with steady-state conductive thermal modeling. We found that the orogen is overall warmer than the forearc and the foreland and that the lithosphere of the northern part of the foreland appears colder than its southern counterpart. Sedimentary blanketing and the thickness of the radiogenic crust exert the main control on the shallow thermal field (<50 km depth). Specific conditions are present where the oceanic slab is relatively shallow (<85 km depth) and the radiogenic crust is thin. This configuration results in relatively colder temperatures compared to regions where the radiogenic crust is thick and the slab is steep. At depths >50 km, the temperatures of the overriding plate are mainly controlled by the mantle heat input and the subduction angle. The thermal field of the upper plate likely preserves the flat subduction angle and influences the spatial distribution of shortening.

Flat-slab conveyor effect induces precursory crustal contraction in the Central Andes

“…Based on the layers of the composition and the temperature from the 3D lithospheric scale models of the SCA (Rodriguez Piceda et al, 2021Piceda et al, , 2022, we assigned representative mechanical properties (Supplementary Table 1, see 'Geodynamic model set up' section). The conservation equations (eqs.…”

“…We built a 3D data-driven geodynamic model using the finite element code ASPECT (Advanced Solver for Problems in Earth's ConvecTion, version 2.3.0-pre, Kronbichler et al, 2012;Heister et al, 2017;Rose et al, 2017;Bangerth et al, 2021) to simulate brittle and ductile deformation. The compositional thicknesses, densities, and temperature fields are mainly based on the lithospheric-scale models of Rodriguez Piceda et al (2021Piceda et al ( , 2022; see Methods and Supplementary Fig 1 and 2 for details). We used adaptive mesh refinement to better refine the central part of the model (Supplementary Fig 2).…”

“…This study incorporates the 3D structural SCA lithosphere model of (Rodriguez Piceda et al, 2021) and its 3D thermal model (Rodriguez Piceda et al, 2022). A detailed description of the model set-up is available at Pons et al, 2023 (related manuscript).…”

“…1). The 3D thermal model (Rodriguez Piceda et al, 2022) was derived from S-wave tomography conversion of the mantle and steady-state conductive modelling for the crust. To overcome the lack of resolution of the tomography associated to the oceanic plate, we assigned a linear thermal gradient between 273 K and 1573 K from its top to its base.…”

Localization of Deformation in a Non‐Collisional Subduction Orogen: The Roles of Dip Geometry and Plate Strength on the Evolution of the Broken Andean Foreland, Sierras Pampeanas, Argentina

“…The reference density for each composition was recalculated to ensure that: (a) the estimated final density of each composition (i.e., after correcting for pressure and temperature, Equation 5, Table S1, Figure S2 in Supporting Information S1), is in the range of the density predicted by the structural model of Rodriguez Piceda et al (2021), and (b) the resulting topography does not deviate substantially from the present-day topography (Text S1 in Supporting Information S1 and Figure 1). The thermal properties used in the initial thermal field are from published average values for the lithology of each model unit (see references in Rodriguez Piceda, Scheck-Wenderoth, Bott, et al, 2022).…”