3‐D Density, Thermal, and Compositional Model of the Antarctic Lithosphere and Implications for Its Evolution

Abstract

We create a 3-D density, temperature, and composition model of the Antarctic lithosphere using an integrative approach combining gravity, topography, and tomography data with mineral physics constraints and seismic data on crustal structures. The latter is used to create a new Moho and crustal density model. Temperature and thermal density variations are estimated based on S wave velocities from two independent tomography models (SL2013sv and AN1-S). Results of the Antarctic continent show the well-known distinction between East and West Antarctica in temperature and density to a depth of about 200 km. Incorporating compositional variations in the temperature calculations increases temperatures in depleted regions by up to 150°C, giving improved insights into thermal structures. The thickness of the lithospheric root also varies strongly between these regions, with values below 100 km in the west and above 200 km in the east. Regions with negative compositional density variations (<−0.040 g/cm 3 at 100 km), high depletion (Mg # > 91.5), and low temperatures (<800°C; central Dronning Maud Land, along the east flank of the Transantarctic Mountains) are interpreted as Precambrian cratonic fragments. Nearly undepleted lithosphere is found in the Lambert Graben and the Aurora Subglacial Basin and is attributed to Mesozoic rifting activity that has caused lithospheric rejuvenation.Plain Language Summary Antarctica remains one of the least studied areas on Earth, because large ice masses and climate conditions strongly hinder measurements. It plays an important role in global phenomena such as sea level change. In order to understand and predict these processes, we need knowledge about the heat coming from the Earth's interior. It has been recently recognized that the thermal state of the lithosphere, the rigid outer shell of the Earth, plays an important role in controlling dynamics of the ice shield and, thus, global sea level changes. Therefore, we create a model of the lithosphere describing the variation in temperature, density, and composition. Before, such models were created by using some single data set (usually seismic tomography). We employ a new integrative approach, combining several data sets to create a comprehensive 3-D model of the Antarctic lithosphere. Combination of various data sets gives more robust models than when using a single approach. Our results of the Antarctic continent show strong differences between East and West Antarctica in temperature and density to a depth of about 200 km. Regions with negative compositional density variations and low temperatures are identified within East Antarctica and are interpreted as being substantially older than the surrounding continent.

Thermal and Compositional Anomalies of the Australian Upper Mantle From Seismic and Gravity Data

“…Despite the data outside, the study area might be less reliable and could vary in different tomography models; for far‐field effects, we should consider only very large/wide structures (like Pacific or Eurasia), which are sufficiently consistent in most of the global models. For the crustal structure outside the Australian Plate, we used the model CRUST1.0 (Laske et al, 2013), which has been improved based on recent continental wide studies of North America (Tesauro et al, 2014b), Eurasia (Stolk et al, 2013; Tesauro et al, 2008), and Antarctica (Haeger et al, 2019).…”

Modeling Satellite Gravity Gradient Data to Derive Density, Temperature, and Viscosity Structure of the Antarctic Lithosphere

“…Journal of Geophysical Research: Solid Earth Another approach to investigate the lithospheric structure of Antarctica in terms of density, along with temperature and composition, has been recently presented by Haeger et al (2019). Instead of predefining the lithospheric mantle composition, that study inverts for composition, density, and temperature while different seismological S wave tomography models are used to iteratively reconcile the estimates in a thermodynamically consistent way.…”

“…Few studies so far have tried to jointly investigate the crust and upper mantle (e.g., An et al, 2015aAn et al, , 2015bHaeger et al, 2019) of EANT, which is needed to better understand the fundamental structure of the lithosphere as a whole. Seismic velocities and rock densities depend on temperature and composition, which can be modeled by minimizing the Gibbs energy or described in simplified terms by other petrophysical parameters such as thermal expansion and compressibility.…”

A Multivariate Approach for Mapping Lithospheric Domain Boundaries in East Antarctica

“…The Australian example suggests these hidden domains will be varied, for example, both cratonic and orogenic. Large-scale models of the Antarctic lithosphere (e.g., Haeger et al, 2019) can potentially be further developed from our mapped interior boundaries. Magnetic surveys and Curie depth variations are widely used to investigate the Antarctic crust (e.g., Ferraccioli et al, 2001Ferraccioli et al, , 2011Goodge & Finn, 2010;Martos et al, 2017;Ruppel et al, 2018).…”