LitMod2D_2.0: An Improved Integrated Geophysical‐Petrological Modeling Tool for the Physical Interpretation of Upper Mantle Anomalies

Abstract

LitMod2D integrates geophysical and petrological data sets to produce the thermal, density, and seismic velocity structure of the lithosphere and upper mantle. We present a new LitMod2D_2.0 package with improvements focused on (i) updated anelastic attenuation correction for anharmonic seismic velocities, (ii) chemical composition in the sublithospheric mantle, and (iii) incorporation of sublithospheric mantle anomalies. Sublithospheric mantle anomalies can be defined with different chemical composition, temperature, seismic velocities, and a combination of them, allowing the application of LitMod2D_2.0 to regions affected by mantle upwelling, subduction, delamination, and metasomatism. We demonstrate the potential application of LitMod2D_2.0 to such regions and the sensitivity of thermal and compositional anomalies on density and seismic velocities through synthetic models. Results show nonlinearity between the sign of thermal and seismic velocity anomalies, and that S wave velocities are more sensitive to temperature whereas P wave velocities are to composition. In a synthetic example of subduction, we show the sensitivity of sublithospheric mantle anomalies associated with the slab and the corner flow on surface observables (elevation, geoid height, and gravity anomalies). A new open‐source graphic user interface is incorporated in the new package. The output of the code is simplified by writing only the relevant physical parameters (temperature, pressure, material type, density, and seismic velocities) to allow the user using predefined post‐processing codes from a toolbox (flexure, mineral assemblages, synthetic passive seismological data, and tomography) or designing new ones. We demonstrate a post‐processing example calculating synthetic seismic tomography, Rayleigh surface‐wave dispersion curves, and P wave receiver functions from the output file of LitMod2D_2.0.

Lithospheric Density Structure and Effective Elastic Thickness Beneath Himalaya and Tibetan Plateau: Inference From the Integrated Analysis of Gravity, Geoid, and Topographic Data Incorporating Seismic Constraints

“…LitMod‐2D_2.0 is a numerical code, which combines geophysical and petrological data to infer the crustal and upper mantle structure down to 410 km depth (Afonso et al, 2008; Kumar et al, 2019). The code calculates the 2‐D distribution of temperature, density, and mantle seismic velocities and the resulting surface heat flow, elevation, gravity, and geoid anomalies (Afonso et al, 2008; Kumar et al, 2019). LitMod‐2D_2.0 works under a forward modeling scheme; at each step, the model outputs (elevation, gravity and geoid anomalies, surface heat flow, and mantle seismic velocities) are compared with observed data (geophysical observables, seismic velocities, and tomography images), and the input parameters and model geometry can be modified by the user within the experimental uncertainties, in a trial and error procedure until the best fitting model is obtained (see Kumar et al, 2019; Tunini et al, 2016, for further details).…”

“…Gravity anomalies are calculated using GM‐SYS professional software (GM‐SYS, 2000) which is based on Talwani's 2‐D algorithm (Talwani et al, 1959), while geoid and topography undulations are calculated using 2‐D Litmod‐2.0 forward modeling algorithm (Afonso et al, 2008; Kumar et al, 2019). LitMod‐2D_2.0 is a numerical code, which combines geophysical and petrological data to infer the crustal and upper mantle structure down to 410 km depth (Afonso et al, 2008; Kumar et al, 2019).…”

“…Tectonics Gravity anomalies are calculated using GM-SYS professional software (GM-SYS, 2000) which is based on Talwani's 2-D algorithm (Talwani et al, 1959), while geoid and topography undulations are calculated using 2-D Litmod-2.0 forward modeling algorithm (Afonso et al, 2008;Kumar et al, 2019). LitMod-2D_2.0 is a numerical code, which combines geophysical and petrological data to infer the crustal and upper mantle structure down to 410 km depth (Afonso et al, 2008;Kumar et al, 2019). The code calculates the 2-D distribution of temperature, density, and mantle seismic velocities and the resulting surface heat flow, elevation, gravity, and geoid anomalies (Afonso et al, 2008;Kumar et al, 2019).…”

“…All the stable assemblages in this study were computed using modified version of thermodynamic database (Afonso & Zlotnik, 2011;Holland & Powell, 1998). The detailed methodology and workflow of the Litmod-2D_2.0 can be found in Kumar et al (2020). The 10.1029/2020TC006219 geometry of the LAB and Moho are modified until the best fit is observed.…”

Opposite Symmetry in the Lithospheric Structure of the Alboran and Algerian Basins and Their Margins (Western Mediterranean): Geodynamic Implications

“…We use the improved LitMod2D_2.0 code (Kumar et al, 2020), which integrates geophysical and petrological data to model the thermo-chemical structure of the crust and the upper mantle down to 400 km. The code, based on Afonso et al (2008), solves the present-day 2D temperature, density (i.e., chemical composition) and seismic velocity by solving stable mantle phase and mineral assemblages using a Gibbs free-energy minimization algorithm and fitting simultaneously SHF, geoid height, Bouguer anomalies, and absolute elevation.…”